首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   4235篇
  免费   470篇
  国内免费   3篇
  2022年   24篇
  2021年   73篇
  2020年   40篇
  2019年   45篇
  2018年   60篇
  2017年   48篇
  2016年   92篇
  2015年   144篇
  2014年   151篇
  2013年   211篇
  2012年   313篇
  2011年   270篇
  2010年   192篇
  2009年   174篇
  2008年   255篇
  2007年   227篇
  2006年   236篇
  2005年   207篇
  2004年   251篇
  2003年   204篇
  2002年   184篇
  2001年   78篇
  2000年   71篇
  1999年   67篇
  1998年   50篇
  1997年   46篇
  1996年   39篇
  1995年   46篇
  1994年   35篇
  1993年   50篇
  1992年   49篇
  1991年   70篇
  1990年   54篇
  1989年   46篇
  1988年   41篇
  1987年   41篇
  1986年   38篇
  1985年   32篇
  1984年   27篇
  1983年   28篇
  1982年   28篇
  1981年   25篇
  1979年   28篇
  1978年   20篇
  1977年   17篇
  1974年   18篇
  1972年   18篇
  1970年   20篇
  1967年   20篇
  1966年   16篇
排序方式: 共有4708条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Fort Greely, Alaska has an extensive complex of weapon training and testing areas located on lands withdrawn from the public domain under the Military Lands Withdrawal Act (PL106-65). The Army has pledged to implement a program to identify possible munitions contamination. Because of the large size (344,165,000 m2) of the high hazard impact areas, characterization of these constituents will be difficult. We used an authoritative sampling design to find locations most likely to contain explosives-residues on three impact areas. We focused our sampling on surface soils and collected multi-increment and discrete samples at locations of known firing events and from areas on the range that had craters, pieces of munitions, targets, or a designation as a firing point. In the two impact areas used primarily by the Army, RDX was the most frequently detected explosive. In the impact area that was also used by the Air Force, TNT was the most frequently detected explosive. Where detected, the explosives concentrations generally were low (<0.05 mg/kg) except in soils near low-order detonations, where the explosive-filler was in contact with the soil surface. These low-order detonations potentially can serve as localized sources for groundwater contamination if positioned in recharge areas.  相似文献   
5.

Background  

Populations of the Oriental White-backed Vulture (Gyps bengalensis) have declined by over 95% within the past decade. This decline is largely due to incidental consumption of the non-steroidal anti-inflammatory veterinary pharmaceutical diclofenac, commonly used to treat domestic livestock. The conservation status of other Gyps vultures in southern Asia is also of immediate concern, given the lack of knowledge regarding status of their populations and the continuing existence of taxonomic uncertainties. In this study, we assess phylogenetic relationships for all recognized species and the majority of subspecies within the genus Gyps. The continuing veterinary use of diclofenac is an unknown but potential risk to related species with similar feeding habits to Gyps bengalensis. Therefore, an accurate assessment of the phylogenetic relationships among Gyps vultures should aid in their conservation by clarifying taxonomic uncertainties, and enabling inference of their respective relatedness to susceptible G. bengalensis.  相似文献   
6.
7.
8.
9.
10.
S Benvenga  J Robbins 《Biochimie》1999,81(5):545-548
Lipoproteins, especially HDL, are carriers of a small fraction of the thyroid hormones in plasma and participate in the intracellular transport of T4. In previous work we showed that a brief period of hypothyroidism alters the hormone distribution among the lipoproteins, causing a decrease in VLDL and LDL binding despite a relative increase in VLDL and LDL cholesterol, an increase in HDL binding, and a reversal of T4 and T3 binding to the smallest HDL size subgroup. The present study of three patients with thyroid hormone resistance and largely compensated hypothyroidism showed thyroid hormone distribution that differed markedly from both normal and hypothyroid subjects. The most striking difference was a much lower binding of both T4 and T3 to HDL and a much higher binding to LDL. If confirmed in a larger group of patients, this might serve as a marker for thyroid hormone resistance.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号