（50）These processes of particle creation and destruction had been predicted from Dirac’s theory before they were actually discovered in nature, and since then they have been observed millions of times.
（50）These processes of particle creation and destruction had been predicted from Dirac’s theory before they were actually discovered in nature, and since then they have been observed millions of times.
相关考题：
The teachers??____________ the office for a few minutes when we arrived. We didn’t meet them.A. had been away from B. had leftC. have been away from D. have left
________ the smallest mistake, the successful launching of the spacecraft would have been impossible. A.Had there beenB.If there wasC.Were there to beD.If there would have been
Medical scientists __________ finding a cure for cancer since 1960s. A. have been working outB. have been workingC. have been working onD. have been building on
Before relativistic particle physics, the constituents of matter had always been considered as being either elementary units which were indestructible and unchangeable, or as composite objects which could be broken up into their constituent parts;
Millions of pounds’ worth damage ______ by a storm which swept across the north of England last night. A has been causedB had been causedC will be causedD will have been caused
Experiments of this kind ____ in both the U.S. and Europe well before the World War. A have conductedB have been conductedC had conductedD had been conducted
John and I ______ friends for eight years. We first went to know each other at a Christmas party. But we ______ each other a couple of times before that. A had been; have seenB have been; have seenC had been; had seenD have been; had seen
Since he had never been in such a situation before, his apprehension was understandable:(). A.eagernessB. fearC.hesitationD.excitement
If only it ()so cold, perhaps I, too, ()more initiative.A、had been,have shownB、have been,would showC、had’t been,cound't have shownD、had't been,could have shown
— How long _____ at this job? — Since 2000.A、were you employedB、have you been employedC、had you been employedD、will you be employed
Since 1780, when the town’s first hat factory ______ in Danbury, Connecticut, the town has been a center for hat manufacturing in the United States.A、were establishedB、was establishingC、had been establishedD、was established
Had Paul received six more votes in the last election, he ________ our chairman now.[A] must have been[B] would have been[C] were[D] would be
__________ your valuable help, we couhtn't have finished the experiment ahead of time．A.If it were not forB. Had it not been forC.Were it not forD.If it has not been for
__________your valuable help, we couldn't have finished the experiment ahead of time. A. If it were not forB. Had it not been forC. Were it not forD. If it has not been for
discovered that my baggage had been lost. I didn’t have any choice but to wait at the airport for fivehours while your employees tried to trace the whereabouts of my baggage. I left the airport without mybelongings as I had an important meeting to attend.It has been one week, and I have not been contacted regarding my baggage. For this reason, I stronglyfeel that I should be compensated for the items that were lost. I hope to hear from your office ( )the week.Sincerely yours,NATHAN HALLA.withinB.fromC.sinceD.near
共用题干To Survive or to Vanish1.Over 3.6 billion years ago,the first creature was born in the world.Since then,the earth started its era with life.The history of life on earth has been a history of interaction between living things and their surroundings.To a large extent,the physical form and the habits of the earth's vegetation and its animal life have been molded by the environment. Considering the whole span of earthly time,the opposite effect,in which life actually modifies its surroundings,has been relatively slight. Only in the present century has one species一man acquired significant power to alter the nature of his world.2.During the past 25 years,this power has not only become increasingly great but it has changed in character. The most alarming of all man's assaults upon the environment is the contamination of air,earth,rivers,and sea with dangerous and even lethal materials. This pollution is for the most part irrecoverable.In this now universal contamination of the environment,chemicals are the sinister partners of radiation in changing the very nature of the world the very nature of its life. Chemicals sprayed on croplands or forests or gardens lie long in soil,entering into living organisms, passing from one to another in a chain of poisoning and death.Or they pass mysteriously by underground streams until they emerge and combine into new forms that kill vegetation,sicken cattle,and work unknown harm on those who drink from once pure wells."Man can hardly even recognize the devils of his own creation,"as a scientist has said.3.Hundreds of millions of years have passed before the globe produced the life that now inhabits the earth.Given time not in years but in millennia life adjusts,and a balance has been reached.But in the modern world there is no time.4.The quick steps of change follows the impetuous pace of man rather than the deliberate pace of nature.Radiation is now the unnatural creation of man's tampering with the atom.The chemicals are the synthetic creations of man's inventive mind,having no counterparts in nature.5.To survive these chemicals would require not merely the years of one man's life but the life of generations.And even this,were it by some miracle possible,would be futile,for the new chemicals come from our laboratories in an endless stream;almost five hundred annually find their way into actual use in the United States alone.Among them are many that are used in man's war against nature.Since the mid l940's over 200 basic chemicals have been created for use in killing insects,weeds,and other organisms described as"pests".6.It is not my contention that chemical insecticides must never he used.I do contend that we have put poisonous and biologically potent chemicals indiscriminately into the hands of persons largely or wholly ignorant of their potentials for harm. We have subjected enormous numbers of people to contact with these poisons,without their consent and often without their knowledge.I contend,furthermore,that we have allowed these chemicals to be used with little or no advance investigation of their effect on soil,water,wildlife,and man himself. Future generations are unlikely to forgive our lack of concern for the integrity of the natural world that supports all life.Human's pollution on nature is for the most part_______.A:man's tampering with the atomB:enormous numbers of people to contact with these poisonsC:the integrity of the natural world that supports all lifeD:inventiveE:irrecoverableF:relatively slight
共用题干To Survive or to Vanish1.Over 3.6 billion years ago,the first creature was born in the world.Since then,the earth started its era with life.The history of life on earth has been a history of interaction between living things and their surroundings.To a large extent,the physical form and the habits of the earth's vegetation and its animal life have been molded by the environment. Considering the whole span of earthly time,the opposite effect,in which life actually modifies its surroundings,has been relatively slight. Only in the present century has one species一man acquired significant power to alter the nature of his world.2.During the past 25 years,this power has not only become increasingly great but it has changed in character. The most alarming of all man's assaults upon the environment is the contamination of air,earth,rivers,and sea with dangerous and even lethal materials. This pollution is for the most part irrecoverable.In this now universal contamination of the environment,chemicals are the sinister partners of radiation in changing the very nature of the world the very nature of its life. Chemicals sprayed on croplands or forests or gardens lie long in soil,entering into living organisms, passing from one to another in a chain of poisoning and death.Or they pass mysteriously by underground streams until they emerge and combine into new forms that kill vegetation,sicken cattle,and work unknown harm on those who drink from once pure wells."Man can hardly even recognize the devils of his own creation,"as a scientist has said.3.Hundreds of millions of years have passed before the globe produced the life that now inhabits the earth.Given time not in years but in millennia life adjusts,and a balance has been reached.But in the modern world there is no time.4.The quick steps of change follows the impetuous pace of man rather than the deliberate pace of nature.Radiation is now the unnatural creation of man's tampering with the atom.The chemicals are the synthetic creations of man's inventive mind,having no counterparts in nature.5.To survive these chemicals would require not merely the years of one man's life but the life of generations.And even this,were it by some miracle possible,would be futile,for the new chemicals come from our laboratories in an endless stream;almost five hundred annually find their way into actual use in the United States alone.Among them are many that are used in man's war against nature.Since the mid l940's over 200 basic chemicals have been created for use in killing insects,weeds,and other organisms described as"pests".6.It is not my contention that chemical insecticides must never he used.I do contend that we have put poisonous and biologically potent chemicals indiscriminately into the hands of persons largely or wholly ignorant of their potentials for harm. We have subjected enormous numbers of people to contact with these poisons,without their consent and often without their knowledge.I contend,furthermore,that we have allowed these chemicals to be used with little or no advance investigation of their effect on soil,water,wildlife,and man himself. Future generations are unlikely to forgive our lack of concern for the integrity of the natural world that supports all life.The effect of life modifying its surroundings has been_______.A:man's tampering with the atomB:enormous numbers of people to contact with these poisonsC:the integrity of the natural world that supports all lifeD:inventiveE:irrecoverableF:relatively slight
共用题干To Survive or to Vanish1.Over 3.6 billion years ago,the first creature was born in the world.Since then,the earth started its era with life.The history of life on earth has been a history of interaction between living things and their surroundings.To a large extent,the physical form and the habits of the earth's vegetation and its animal life have been molded by the environment. Considering the whole span of earthly time,the opposite effect,in which life actually modifies its surroundings,has been relatively slight. Only in the present century has one species一man acquired significant power to alter the nature of his world.2.During the past 25 years,this power has not only become increasingly great but it has changed in character. The most alarming of all man's assaults upon the environment is the contamination of air,earth,rivers,and sea with dangerous and even lethal materials. This pollution is for the most part irrecoverable.In this now universal contamination of the environment,chemicals are the sinister partners of radiation in changing the very nature of the world the very nature of its life. Chemicals sprayed on croplands or forests or gardens lie long in soil,entering into living organisms, passing from one to another in a chain of poisoning and death.Or they pass mysteriously by underground streams until they emerge and combine into new forms that kill vegetation,sicken cattle,and work unknown harm on those who drink from once pure wells."Man can hardly even recognize the devils of his own creation,"as a scientist has said.3.Hundreds of millions of years have passed before the globe produced the life that now inhabits the earth.Given time not in years but in millennia life adjusts,and a balance has been reached.But in the modern world there is no time.4.The quick steps of change follows the impetuous pace of man rather than the deliberate pace of nature.Radiation is now the unnatural creation of man's tampering with the atom.The chemicals are the synthetic creations of man's inventive mind,having no counterparts in nature.5.To survive these chemicals would require not merely the years of one man's life but the life of generations.And even this,were it by some miracle possible,would be futile,for the new chemicals come from our laboratories in an endless stream;almost five hundred annually find their way into actual use in the United States alone.Among them are many that are used in man's war against nature.Since the mid l940's over 200 basic chemicals have been created for use in killing insects,weeds,and other organisms described as"pests".6.It is not my contention that chemical insecticides must never he used.I do contend that we have put poisonous and biologically potent chemicals indiscriminately into the hands of persons largely or wholly ignorant of their potentials for harm. We have subjected enormous numbers of people to contact with these poisons,without their consent and often without their knowledge.I contend,furthermore,that we have allowed these chemicals to be used with little or no advance investigation of their effect on soil,water,wildlife,and man himself. Future generations are unlikely to forgive our lack of concern for the integrity of the natural world that supports all life.Paragraph 1_______A:Man should be cautious in chemical use.B:It takes generations for mankind to adapt themselves to the chemicals.C:Chemicals are human's inventionD:Human's power increases and has changed its character in the past quarter century.E:The new change in the relationship between earth and its creature一human's power playing a greater role in changing the worldF: Modern world gives no time for nature to adjust to human.
共用题干To Survive or to Vanish1.Over 3.6 billion years ago,the first creature was born in the world.Since then,the earth started its era with life.The history of life on earth has been a history of interaction between living things and their surroundings.To a large extent,the physical form and the habits of the earth's vegetation and its animal life have been molded by the environment. Considering the whole span of earthly time,the opposite effect,in which life actually modifies its surroundings,has been relatively slight. Only in the present century has one species一man acquired significant power to alter the nature of his world.2.During the past 25 years,this power has not only become increasingly great but it has changed in character. The most alarming of all man's assaults upon the environment is the contamination of air,earth,rivers,and sea with dangerous and even lethal materials. This pollution is for the most part irrecoverable.In this now universal contamination of the environment,chemicals are the sinister partners of radiation in changing the very nature of the world the very nature of its life. Chemicals sprayed on croplands or forests or gardens lie long in soil,entering into living organisms, passing from one to another in a chain of poisoning and death.Or they pass mysteriously by underground streams until they emerge and combine into new forms that kill vegetation,sicken cattle,and work unknown harm on those who drink from once pure wells."Man can hardly even recognize the devils of his own creation,"as a scientist has said.3.Hundreds of millions of years have passed before the globe produced the life that now inhabits the earth.Given time not in years but in millennia life adjusts,and a balance has been reached.But in the modern world there is no time.4.The quick steps of change follows the impetuous pace of man rather than the deliberate pace of nature.Radiation is now the unnatural creation of man's tampering with the atom.The chemicals are the synthetic creations of man's inventive mind,having no counterparts in nature.5.To survive these chemicals would require not merely the years of one man's life but the life of generations.And even this,were it by some miracle possible,would be futile,for the new chemicals come from our laboratories in an endless stream;almost five hundred annually find their way into actual use in the United States alone.Among them are many that are used in man's war against nature.Since the mid l940's over 200 basic chemicals have been created for use in killing insects,weeds,and other organisms described as"pests".6.It is not my contention that chemical insecticides must never he used.I do contend that we have put poisonous and biologically potent chemicals indiscriminately into the hands of persons largely or wholly ignorant of their potentials for harm. We have subjected enormous numbers of people to contact with these poisons,without their consent and often without their knowledge.I contend,furthermore,that we have allowed these chemicals to be used with little or no advance investigation of their effect on soil,water,wildlife,and man himself. Future generations are unlikely to forgive our lack of concern for the integrity of the natural world that supports all life.Radiation is now the unnatural creation of_______.A:man's tampering with the atomB:enormous numbers of people to contact with these poisonsC:the integrity of the natural world that supports all lifeD:inventiveE:irrecoverableF:relatively slight
共用题干To Survive or to Vanish1.Over 3.6 billion years ago,the first creature was born in the world.Since then,the earth started its era with life.The history of life on earth has been a history of interaction between living things and their surroundings.To a large extent,the physical form and the habits of the earth's vegetation and its animal life have been molded by the environment. Considering the whole span of earthly time,the opposite effect,in which life actually modifies its surroundings,has been relatively slight. Only in the present century has one species一man acquired significant power to alter the nature of his world.2.During the past 25 years,this power has not only become increasingly great but it has changed in character. The most alarming of all man's assaults upon the environment is the contamination of air,earth,rivers,and sea with dangerous and even lethal materials. This pollution is for the most part irrecoverable.In this now universal contamination of the environment,chemicals are the sinister partners of radiation in changing the very nature of the world the very nature of its life. Chemicals sprayed on croplands or forests or gardens lie long in soil,entering into living organisms, passing from one to another in a chain of poisoning and death.Or they pass mysteriously by underground streams until they emerge and combine into new forms that kill vegetation,sicken cattle,and work unknown harm on those who drink from once pure wells."Man can hardly even recognize the devils of his own creation,"as a scientist has said.3.Hundreds of millions of years have passed before the globe produced the life that now inhabits the earth.Given time not in years but in millennia life adjusts,and a balance has been reached.But in the modern world there is no time.4.The quick steps of change follows the impetuous pace of man rather than the deliberate pace of nature.Radiation is now the unnatural creation of man's tampering with the atom.The chemicals are the synthetic creations of man's inventive mind,having no counterparts in nature.5.To survive these chemicals would require not merely the years of one man's life but the life of generations.And even this,were it by some miracle possible,would be futile,for the new chemicals come from our laboratories in an endless stream;almost five hundred annually find their way into actual use in the United States alone.Among them are many that are used in man's war against nature.Since the mid l940's over 200 basic chemicals have been created for use in killing insects,weeds,and other organisms described as"pests".6.It is not my contention that chemical insecticides must never he used.I do contend that we have put poisonous and biologically potent chemicals indiscriminately into the hands of persons largely or wholly ignorant of their potentials for harm. We have subjected enormous numbers of people to contact with these poisons,without their consent and often without their knowledge.I contend,furthermore,that we have allowed these chemicals to be used with little or no advance investigation of their effect on soil,water,wildlife,and man himself. Future generations are unlikely to forgive our lack of concern for the integrity of the natural world that supports all life.Future generations are unlikely to forgive our lack of concern for_______.A:man's tampering with the atomB:enormous numbers of people to contact with these poisonsC:the integrity of the natural world that supports all lifeD:inventiveE:irrecoverableF:relatively slight
If the whole operation__________beforehand,a great deal of time and money would have been lost.A.was not plannedB.has not been plannedC.had not been plannedD.were not planned
—There‘s been an earthquake.—I know.At least a hundred people________.A.were to be killedB.are said to have been killedC.said to have been killedD.are said to kill
It may be pointed out that warfare（战争）as practiced by man has no parallel in nature,This is to say that within the more highly developed animal populations of this earth,there is not now.nor has there been similar destruction within a species（物种）itself.In fact,one has to go to the lowliest forms of animal life,such as certain kinds of ants,to find anything comparable to human warfare.It is a curious fact that mankind appears to give the killing of his own kind a good reason by imaging that it is a"law of nature".There are now a lot of wrong ideas about the laws of nature,of which this is one of the most incorrect and fateful（致命的）.Political beliefs have been based upon it with results that have come near to destroying human civilization.The theory that war is a biological necessity.that it is nature′s method of controlling population and believing in the survival（生存）of the strong and the elimination（灭亡）of the weak,is totally wrong and insupportable.Within the last century.when wars have been common all over the world,the human population of the earth has almost doubled.According to Sentence 2,which of the following is true?A.The destruction is similar to the killing of each other within human beings.B.There is not the similar destruction now,but it occurred before.,'C.There is never a time when we may see the similar destruction.D.The destruction is now a thing of the past.
单选题Which of the following is NOT true about Gordon Brown’s recent agenda?AHe has been negotiating on a tougher regulation of tax havens.BHe had a talk with Obama before the summit.CHe made a speech at St Paul’s Cathedral.DHe had an interview with the Financial Times.
单选题It is implied in the passage that ______.Amany scientists had known dinoflagellate before 1988Bthere had been no such organisms before 1988Cmany scientists were in doubt about the nature of the organism in 1988Dno scientists knew anything about the organism in 1988
单选题Although no proof yet exists of the electromagnetic disturbances observed being the results of nuclear weapons testing, diplomats are treating the situation with utmost delicacy.Aof the electromagnetic disturbances observed being the results of nuclear weapons testingBregarding the observed electromagnetic disturbances having been the results of nuclear weapons testingCthat the electromagnetic disturbances observed were the results of nuclear weapons testingDthat nuclear weapons testing resulted in the electromagnetic disturbances having been observedEthat the electromagnetic disturbance observed were resulting from nuclear weapons testing