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   2548480篇
  免费   199352篇
  国内免费   3965篇
耳鼻咽喉   36284篇
儿科学   86539篇
妇产科学   72084篇
基础医学   362570篇
口腔科学   72832篇
临床医学   225671篇
内科学   498509篇
皮肤病学   54842篇
神经病学   204254篇
特种医学   101680篇
外国民族医学   1064篇
外科学   387726篇
综合类   59927篇
现状与发展   4篇
一般理论   866篇
预防医学   196845篇
眼科学   58519篇
药学   191324篇
  5篇
中国医学   4747篇
肿瘤学   135505篇
  2018年   24813篇
  2016年   21133篇
  2015年   24200篇
  2014年   33620篇
  2013年   51573篇
  2012年   70079篇
  2011年   74224篇
  2010年   44164篇
  2009年   42044篇
  2008年   71059篇
  2007年   75419篇
  2006年   76307篇
  2005年   74287篇
  2004年   72762篇
  2003年   69932篇
  2002年   68539篇
  2001年   119632篇
  2000年   124133篇
  1999年   105397篇
  1998年   28974篇
  1997年   26261篇
  1996年   26546篇
  1995年   25626篇
  1994年   24169篇
  1993年   22618篇
  1992年   86012篇
  1991年   83886篇
  1990年   82092篇
  1989年   78755篇
  1988年   73039篇
  1987年   71952篇
  1986年   67908篇
  1985年   65464篇
  1984年   49060篇
  1983年   42034篇
  1982年   24657篇
  1981年   22184篇
  1980年   20495篇
  1979年   45981篇
  1978年   32076篇
  1977年   27046篇
  1976年   25458篇
  1975年   27168篇
  1974年   32716篇
  1973年   31523篇
  1972年   28992篇
  1971年   26876篇
  1970年   24977篇
  1969年   23196篇
  1968年   21193篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
24.
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   
25.
26.
27.
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   
28.
29.
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   
30.
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