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   1768022篇
  免费   149643篇
  国内免费   29000篇
耳鼻咽喉   21117篇
儿科学   51220篇
妇产科学   44996篇
基础医学   239367篇
口腔科学   43560篇
临床医学   177560篇
内科学   331904篇
皮肤病学   37229篇
神经病学   134022篇
特种医学   67117篇
外国民族医学   688篇
外科学   241703篇
综合类   102083篇
现状与发展   89篇
一般理论   516篇
预防医学   136798篇
眼科学   41770篇
药学   137991篇
  433篇
中国医学   27545篇
肿瘤学   108957篇
  2022年   18320篇
  2021年   28722篇
  2020年   21034篇
  2019年   23038篇
  2018年   28360篇
  2017年   24062篇
  2016年   24711篇
  2015年   32420篇
  2014年   42973篇
  2013年   51940篇
  2012年   72855篇
  2011年   78883篇
  2010年   49148篇
  2009年   44076篇
  2008年   64970篇
  2007年   67171篇
  2006年   66838篇
  2005年   64448篇
  2004年   55889篇
  2003年   53434篇
  2002年   49776篇
  2001年   80635篇
  2000年   81983篇
  1999年   69196篇
  1998年   22075篇
  1997年   20336篇
  1996年   19412篇
  1995年   18401篇
  1994年   16426篇
  1993年   14513篇
  1992年   47954篇
  1991年   45370篇
  1990年   43074篇
  1989年   40925篇
  1988年   37298篇
  1987年   36351篇
  1986年   33673篇
  1985年   31846篇
  1984年   24128篇
  1983年   20250篇
  1982年   12316篇
  1979年   20811篇
  1978年   14615篇
  1977年   12114篇
  1976年   11383篇
  1975年   11639篇
  1974年   14016篇
  1973年   13551篇
  1972年   12653篇
  1971年   11479篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
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   
64.
65.
66.
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   
67.
68.
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   
69.
70.
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   
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