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   2065434篇
  免费   168435篇
  国内免费   4792篇
耳鼻咽喉   28884篇
儿科学   65717篇
妇产科学   60118篇
基础医学   295471篇
口腔科学   58050篇
临床医学   184141篇
内科学   404680篇
皮肤病学   46549篇
神经病学   170700篇
特种医学   80545篇
外国民族医学   626篇
外科学   313835篇
综合类   52360篇
现状与发展   4篇
一般理论   704篇
预防医学   162754篇
眼科学   48159篇
药学   148706篇
  1篇
中国医学   4464篇
肿瘤学   112193篇
  2018年   21876篇
  2017年   16795篇
  2016年   19022篇
  2015年   21589篇
  2014年   30681篇
  2013年   46187篇
  2012年   62421篇
  2011年   65872篇
  2010年   38671篇
  2009年   36867篇
  2008年   61332篇
  2007年   65494篇
  2006年   65938篇
  2005年   64088篇
  2004年   61706篇
  2003年   59178篇
  2002年   57146篇
  2001年   96830篇
  2000年   99123篇
  1999年   82839篇
  1998年   24083篇
  1997年   21808篇
  1996年   21751篇
  1995年   20647篇
  1994年   19084篇
  1993年   17895篇
  1992年   64787篇
  1991年   62346篇
  1990年   60293篇
  1989年   57636篇
  1988年   53475篇
  1987年   52344篇
  1986年   49294篇
  1985年   47301篇
  1984年   36323篇
  1983年   30805篇
  1982年   19194篇
  1981年   17330篇
  1979年   34083篇
  1978年   24267篇
  1977年   20271篇
  1976年   18916篇
  1975年   19855篇
  1974年   24354篇
  1973年   23471篇
  1972年   22190篇
  1971年   20351篇
  1970年   19405篇
  1969年   18372篇
  1968年   16954篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
52.
53.
Sinus venosus atrial septal defect (SV‐ASD) usually coexists with partial anomalous pulmonary vein connection (PAPVC). It is a difficult diagnosis in transthoracic echocardiography (TTE) due to eccentric position of defects. We present a rare case of atypical anatomical variation in PAPVC, which was never described before. Two right pulmonary veins drained into superior vena cava, which overrode SV‐ASD and interatrial septum, a third pulmonary vein into the right atrium. Complete diagnosis could not be set after TTE, nor transesophageal echocardiography, whereas angio‐CT was finally conclusive. This diagnostic approach allowed the surgical planning.  相似文献   
54.
55.
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   
56.
57.
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   
58.
59.
60.
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