共查询到20条相似文献，搜索用时 984 毫秒
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Sokal RR 《Science (New York, N.Y.)》1974,185(4157):1115-1123
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Hillman WS 《Science (New York, N.Y.)》1976,193(4252):453-458
The roles of photoperiodism and related light-dependent and hormonal processes in plants are not well understood. Rapid growth, aquatic habit, and adaptability to axenic culture make the Lemnaceae, or duckweeds, excellent material for investigating these topics and others in which highly defined conditions or the presence of organic substances are crucial. As a major example among several that are described, recent work with one species suggests a relation between some features of carbon dioxide flux and the photoperiodic timing mechanism, thus providing a system in which the biochemical basis of the latter may be explored. 相似文献
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Edelson I 《Science (New York, N.Y.)》1968,160(3829):797-798
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Famines are generally caused by decline in food production in successive years brought about by poor weather, war, or both. The consequent complex interactions between prices, employment, and assets impoverish victims and lead to sharply increased mortality. Government policy is a key determinant as to whether or not these conditions mature into wisespread famine. India and Bangladesh have succeeded in controlling famines in recent years, but problems in most of Africa remain intractable due to civil unrest and a paucity of resources, including trained people, institutions, and infrastructure. General economic development and political consensus is needed to reduce Africa's vulnerability to famine. In this context, judiciously provided foreign aid can be of immense help. 相似文献
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Pierce JR 《Science (New York, N.Y.)》1977,195(4283):1092-1095
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Cook OF 《Science (New York, N.Y.)》1907,26(654):50-52
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Pieri DC 《Science (New York, N.Y.)》1980,210(4472):895-897
Branching valley networks throughout the heavily cratered terrain of Mars exhibit no compelling evidence for formation by rainfall-fed erosion. The networks are diffuse and inefficient, with irregular tributary junction angles and large, undissected intervalley areas. Rather, the deeply entrenched canyons, with blunt amphitheater terminations, cliff-bench wall topography, lack of evidence of interior erosion by flow, and clear structural control, suggest headward extension by basal sapping. The size-frequency distributions of impact craters in these valleys and in the heavily cratered terrain that surrounds them are statistically indistinguishable, suggesting that valley formation has not occurred on Mars for billions of years. 相似文献
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Walsh J 《Science (New York, N.Y.)》1972,175(4019):281-282
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D R Schneider G L Endahl M C Dodd J E Jesseph N J Bigley R M Zollinger 《Science (New York, N.Y.)》1967,156(773):391-392
Antibodies to the antral hormone gastrin have been induced in the rabbit and detected by passive hemagglutination. Specificity of the antibody, as determined by three methods, is directed to gastrins I and II, gastrin pentapeptide, and gastrin tetrapeptide, as well as to the stage-1 gastrin used for immunization. 相似文献
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Kerr RA 《Science (New York, N.Y.)》1988,239(4836):144-146
Researchers who gathered in San Francisco in December at the annual fall meeting of the American Geophysical Union heard the usual variety of talks treating everything from Earth's core to the tenuous wisps of solar particles far beyond Pluto. Earthquakes, the local California variety in particular, figured prominently, as did the currently popular subjects of ancient air trapped in amber and the deepening Antarctic ozone hole. 相似文献
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Genes, genetics, and epigenetics: a correspondence 总被引：2，自引：0，他引：2
Over the past months, as this special issue took shape, the Editors of Science have monitored an exchange of seven letters initiated by three queries from M. Bacon. These queries concern the popular definitions of "genes," "genetics," and "epigenetics." Below, we reprint excerpts from these letters, referring interested readers to www.sciencemag.org/cgi/content/full/293/5532/1103/DC1 for the complete text and additional references. 相似文献
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Thwing CF 《Science (New York, N.Y.)》1931,73(1891):331-333