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   1803112篇
  免费   133238篇
  国内免费   3031篇
耳鼻咽喉   26065篇
儿科学   55646篇
妇产科学   49980篇
基础医学   257762篇
口腔科学   52114篇
临床医学   159476篇
内科学   341261篇
皮肤病学   38760篇
神经病学   141029篇
特种医学   72013篇
外国民族医学   370篇
外科学   278022篇
综合类   43378篇
现状与发展   3篇
一般理论   513篇
预防医学   133391篇
眼科学   42578篇
药学   140770篇
  7篇
中国医学   4092篇
肿瘤学   102151篇
  2018年   17481篇
  2016年   15569篇
  2015年   17737篇
  2014年   24793篇
  2013年   36718篇
  2012年   49964篇
  2011年   52689篇
  2010年   30899篇
  2009年   29013篇
  2008年   49163篇
  2007年   52938篇
  2006年   53415篇
  2005年   51545篇
  2004年   49908篇
  2003年   47911篇
  2002年   46226篇
  2001年   86938篇
  2000年   89044篇
  1999年   74804篇
  1998年   20099篇
  1997年   18062篇
  1996年   17995篇
  1995年   16934篇
  1994年   15774篇
  1993年   14925篇
  1992年   59323篇
  1991年   57513篇
  1990年   56541篇
  1989年   54589篇
  1988年   50139篇
  1987年   49077篇
  1986年   46433篇
  1985年   44246篇
  1984年   32984篇
  1983年   28172篇
  1982年   16567篇
  1981年   14808篇
  1979年   31508篇
  1978年   21976篇
  1977年   19151篇
  1976年   17045篇
  1975年   19012篇
  1974年   22870篇
  1973年   21995篇
  1972年   21001篇
  1971年   19627篇
  1970年   18408篇
  1969年   17883篇
  1968年   16001篇
  1967年   14536篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
We report on a child with several café au lait spots in association with a lumbar lipomeningomyelocele as an apparently new association. Cutaneous markers, the identification of which plays a crucial role in the early diagnosis and management of spinal malformations, can accompany occult spinal dysraphism. Herein we report a case of lumbar lipomeningomyelocele associated with an overlying café au lait spot that served as a marker of occult spinal dysraphism. The patient also had segmental café au lait spots on the face, making the association unique.  相似文献   
43.
44.
45.
46.
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   
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