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Evidence of simian immunodeficiency virus (SIV) infection has been reported for 26 different species of African nonhuman primates. Two of these viruses, SIVcpz from chimpanzees and SIVsm from sooty mangabeys, are the cause of acquired immunodeficiency syndrome (AIDS) in humans. Together, they have been transmitted to humans on at least seven occasions. The implications of human infection by a diverse set of SIVs and of exposure to a plethora of additional human immunodeficiency virus-related viruses are discussed. 相似文献
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Benjamin CJ 《Science (New York, N.Y.)》1975,188(4191):886-888
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An assessment of the effects of airline deregulation on travelers and carriers indicates that deregulation has provided travelers and carriers with $14.9 billion of annual benefits (1988 dollars). Airport congestion, airline safety, airline bankruptcy, and mergers are also analyzed and found in most cases to have reduced benefits. But, these costs should not be attributed to deregulation per se, but to failures by the government to pursue appropriate policies in these areas. Pursuit of policies that promote airline competition and efficient use of airport capacity would significantly increase the benefits from deregulation and would provide valuable guidance for other industries undergoing the transition to deregulation. 相似文献
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Holden C 《Science (New York, N.Y.)》1975,189(4197):120-124
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Samuels SW 《Science (New York, N.Y.)》1990,248(4957):799-799
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Cronje R 《Science (New York, N.Y.)》2008,319(5869):1483
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Snow CP 《Science (New York, N.Y.)》1966,151(3711):650-653