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   2374586篇
  免费   175362篇
  国内免费   4385篇
耳鼻咽喉   35233篇
儿科学   77305篇
妇产科学   67259篇
基础医学   335225篇
口腔科学   67745篇
临床医学   204546篇
内科学   467848篇
皮肤病学   53038篇
神经病学   187764篇
特种医学   95283篇
外国民族医学   1056篇
外科学   367240篇
综合类   53611篇
现状与发展   7篇
一般理论   763篇
预防医学   171934篇
眼科学   55049篇
药学   178442篇
  4篇
中国医学   5005篇
肿瘤学   129976篇
  2018年   22642篇
  2016年   19338篇
  2015年   21893篇
  2014年   30638篇
  2013年   46797篇
  2012年   63051篇
  2011年   66826篇
  2010年   39904篇
  2009年   38312篇
  2008年   64006篇
  2007年   69296篇
  2006年   69788篇
  2005年   67852篇
  2004年   66357篇
  2003年   64293篇
  2002年   63221篇
  2001年   113866篇
  2000年   117668篇
  1999年   99870篇
  1998年   26964篇
  1997年   24413篇
  1996年   24252篇
  1995年   22954篇
  1994年   21581篇
  1993年   20131篇
  1992年   78314篇
  1991年   76261篇
  1990年   74465篇
  1989年   71998篇
  1988年   66745篇
  1987年   65767篇
  1986年   62150篇
  1985年   59238篇
  1984年   44435篇
  1983年   37585篇
  1982年   22123篇
  1981年   20063篇
  1979年   41266篇
  1978年   29017篇
  1977年   24923篇
  1976年   22916篇
  1975年   25594篇
  1974年   30162篇
  1973年   29180篇
  1972年   27588篇
  1971年   25450篇
  1970年   24093篇
  1969年   22692篇
  1968年   21038篇
  1967年   18874篇
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
51.
Dosage form is a mean used for the delivery of drug to a living body. In order to get the desired effect the drug should be delivered to its site of action at such rate and concentration to achieve the maximum therapeutic effect and minimum adverse effect. Since oral route is still widely accepted route but having a common drawback of difficulty in swallowing of tablets and capsules. Therefore a lot of research has been done on novel drug delivery systems. This review is about oral dispersible tablets a novel approach in drug delivery systems that are now a day''s more focused in formulation world, and laid a new path that, helped the patients to build their compliance level with the therapy, also reduced the cost and ease the administration especially in case of pediatrics and geriatrics. Quick absorption, rapid onset of action and reduction in drug loss properties are the basic advantages of this dosage form.  相似文献   
52.
53.
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   
54.
55.
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.
The human visual system is amenable to a number of adaptive processes; one such process, or collection of processes, is the adaptation to blur. Blur adaptation can be observed as an improvement in vision under degraded conditions, and these changes occur relatively rapidly following exposure to blur. The potential important future directions of this research area and the clinical implications of blur adaptation are discussed.  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