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   2017864篇
  免费   152794篇
  国内免费   4565篇
耳鼻咽喉   30351篇
儿科学   59396篇
妇产科学   57934篇
基础医学   285741篇
口腔科学   61242篇
临床医学   173793篇
内科学   389695篇
皮肤病学   44061篇
神经病学   162608篇
特种医学   81378篇
外国民族医学   590篇
外科学   314449篇
综合类   50883篇
现状与发展   10篇
一般理论   680篇
预防医学   146927篇
眼科学   48317篇
药学   152440篇
  4篇
中国医学   4479篇
肿瘤学   110245篇
  2018年   18225篇
  2015年   19233篇
  2014年   26703篇
  2013年   40379篇
  2012年   53439篇
  2011年   55996篇
  2010年   33187篇
  2009年   31623篇
  2008年   52991篇
  2007年   57424篇
  2006年   57616篇
  2005年   56056篇
  2004年   54668篇
  2003年   52733篇
  2002年   51330篇
  2001年   88848篇
  2000年   91241篇
  1999年   77494篇
  1998年   21855篇
  1997年   20035篇
  1996年   19310篇
  1995年   18279篇
  1994年   17366篇
  1992年   62631篇
  1991年   60710篇
  1990年   59710篇
  1989年   58078篇
  1988年   54346篇
  1987年   53557篇
  1986年   51228篇
  1985年   48993篇
  1984年   37324篇
  1983年   31752篇
  1982年   19521篇
  1981年   17972篇
  1980年   16723篇
  1979年   36752篇
  1978年   26362篇
  1977年   22678篇
  1976年   20606篇
  1975年   22994篇
  1974年   27861篇
  1973年   26947篇
  1972年   25762篇
  1971年   24074篇
  1970年   22901篇
  1969年   22018篇
  1968年   20294篇
  1967年   18497篇
  1966年   17276篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
45.
Bipolar disorder (BD) is a common psychiatric mood disorder affecting more than 1-2% of the general population of different European countries. Unfortunately, there is no objective laboratory-based test to aid BD diagnosis or monitor its progression, and little is known about the molecular basis of BD. Here, we performed a comparative proteomic study to identify differentially expressed plasma proteins in various BD mood states (depressed BD, manic BD, and euthymic BD) relative to healthy controls. A total of 10 euthymic BD, 20 depressed BD, 15 manic BD, and 20 demographically matched healthy control subjects were recruited. Seven high-abundance proteins were immunodepleted in plasma samples from the 4 experimental groups, which were then subjected to proteome-wide expression profiling by two-dimensional electrophoresis and matrix-assisted laser desorption/ionization-time-of-flight/time-of-flight tandem mass spectrometry. Proteomic results were validated by immunoblotting and bioinformatically analyzed using MetaCore. From a total of 32 proteins identified with 1.5-fold changes in expression compared with healthy controls, 16 proteins were perturbed in BD independent of mood state, while 16 proteins were specifically associated with particular BD mood states. Two mood-independent differential proteins, apolipoprotein (Apo) A1 and Apo L1, suggest that BD pathophysiology may be associated with early perturbations in lipid metabolism. Moreover, down-regulation of one mood-dependent protein, carbonic anhydrase 1 (CA-1), suggests it may be involved in the pathophysiology of depressive episodes in BD. Thus, BD pathophysiology may be associated with early perturbations in lipid metabolism that are independent of mood state, while CA-1 may be involved in the pathophysiology of depressive episodes.  相似文献   
46.
47.
48.
Analyzing functional species’ characteristics (species traits) that represent physiological, life history and morphological characteristics of species help understanding the impacts of various stressors on aquatic communities at field conditions. This research aimed to study the combined effects of pesticides and other environmental factors (temperature, dissolved oxygen, dissolved organic carbon, floating macrophytes cover, phosphate, nitrite, and nitrate) on the trait modality distribution of aquatic macrofauna communities. To this purpose, a field inventory was performed in a flower bulb growing area of the Netherlands with significant variation in pesticides pressures. Macrofauna community composition, water chemistry parameters and pesticide concentrations in ditches next to flower bulb fields were determined. Trait modalities of nine traits (feeding mode, respiration mode, locomotion type, resistance form, reproduction mode, life stage, voltinism, saprobity, maximum body size) likely to indicate pesticides impacts were analyzed. According to a redundancy analysis, phosphate -and not pesticides- constituted the main factor structuring the trait modality distribution of aquatic macrofauna. The functional composition could be ascribed for 2–4 % to pesticides, and for 3–11 % to phosphate. The lack of trait responses to pesticides may indicate that species may have used alternative strategies to adapt to ambient pesticides stress. Biomass of animals exhibiting trait modalities related to feeding by predation and grazing, presence of diapause form or dormancy, reproduction by free clutches and ovoviviparity, life stage of larvae and pupa, was negatively correlated to the concentration of phosphate. Hence, despite the high pesticide pollution in the area, variation in nutrient-related stressors seems to be the dominant driver of the functional composition of aquatic macrofauna assembly in agricultural ditches.  相似文献   
49.
50.
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