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Geological processes are fundamental to the understanding of Global Change and the geological record provides a baseline against which to assess the nature and significance of contemporary global change (Price 1986) 相似文献
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Research on complex systems has identified various aggregate relationships in phenomena that describe these systems. Travel length has been characterized by negative power distributions. Controversy, however, exists over whether mobility patterns can be modeled in terms of a simple power law (Lévy flight model) or that more complicated power laws (exponential power law, truncated Pareto) are required. This study concentrates on two issues: testing the validity of exponential power laws and truncated Pareto distributions in urban systems to describe aggregate mobility patterns, and examining differences in mobility patterns for different travel purposes. The article describes the results of an analysis of Global Positioning System (GPS) taxi trajectory data, collected in Guangzhou, China, to identify mobility patterns in the city. The least squares statistic is used to estimate the parameters of the distribution functions. Results suggest that a fusion of functions, based on an exponential power law and a truncated Pareto distribution, represents the travel time distribution best. Moreover, the findings of this study indicate different mobility patterns to exist for different travel purposes. 相似文献
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Lerner BH 《Journal of the history of medicine and allied sciences》2004,59(4):507-521
Historians have debated the degree to which past patients have provided meaningful consent prior to medical interventions. This article, a chart review of 170 patients treated for cancer between 1945 and 1970, adds to this literature by exploring the years when informed consent was being introduced in medical practice. As would be expected in a largely paternalistic era, physicians controlled most of the clinical encounters, even concealing cancer diagnoses. Yet thirty-one (18 percent) of the patients showed some involvement in decision making, either writing restrictions on their consent forms, asking probing questions, or otherwise challenging physicians' orders. Although the overall number of patients studied was small, minority and other ward patients were as likely as white, private patients to speak up. This study concludes that most patients passively assented to treatment, signing consent forms without making any inquiries. But a small group of patients challenged their physicians, leading them to learn more about proposed treatment options and perhaps make more informed decisions. Although motivated in part by the increasing attention to better consent practices, these patients spoke up for other reasons as well, possibly including their basic personalities, prior negative experiences in hospitals, or apprehensiveness regarding specific types of interventions. Further research should explore the factors--beyond the introduction of informed consent--that have historically promoted better dialogue between physicians and patients. 相似文献
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The reconstruction of woodland history is important in relation to archaeological, ecological, biogeographical and evolutionary problems, and insect remains are a significant source of relevant information. Fully natural interglacial and Holocene ‘waterlogged’ deposits assumed to have formed in woodland generally contain abundant macrofossils of both plants and insects indicative of trees. In contrast, British archaeological deposits rich in macrofossil remains of trees often lack, or contain very few, tree-associated insects. To cast light on this contradiction, assemblages of insect (Coleoptera and Hemiptera) remains from a range of modern deposits with various spatial relationships to woodland and trees have been analysed. The proportions of tree-associated insects varied greatly. There was a general trend from higher values in woodland and near to isolated trees of species supporting a rich insect fauna, to low or zero values where there were no trees. However, low values sometimes occurred in woods or near trees, so that rarity of tree-associated insects in archaeological deposits does not always carry the implication of a treeless environment. Further investigation is suggested, with emphasis on the importance of identifying isolated trees, scrub and hedges as a resource for humans and wildlife in the past. 相似文献