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   2735198篇
  免费   204203篇
  国内免费   6042篇
耳鼻咽喉   36178篇
儿科学   90523篇
妇产科学   75608篇
基础医学   387541篇
口腔科学   77758篇
临床医学   247742篇
内科学   536293篇
皮肤病学   62824篇
神经病学   217728篇
特种医学   103084篇
外国民族医学   696篇
外科学   411688篇
综合类   63973篇
现状与发展   7篇
一般理论   950篇
预防医学   209516篇
眼科学   64131篇
药学   197137篇
  7篇
中国医学   6593篇
肿瘤学   155466篇
  2019年   21951篇
  2018年   31506篇
  2017年   23864篇
  2016年   26567篇
  2015年   29950篇
  2014年   42018篇
  2013年   62307篇
  2012年   85409篇
  2011年   90547篇
  2010年   53390篇
  2009年   50309篇
  2008年   83729篇
  2007年   88889篇
  2006年   89731篇
  2005年   86373篇
  2004年   83094篇
  2003年   79208篇
  2002年   76353篇
  2001年   138666篇
  2000年   142172篇
  1999年   117706篇
  1998年   32335篇
  1997年   28517篇
  1996年   28600篇
  1995年   27367篇
  1994年   24976篇
  1993年   23251篇
  1992年   89730篇
  1991年   86113篇
  1990年   82865篇
  1989年   79545篇
  1988年   72813篇
  1987年   71156篇
  1986年   66656篇
  1985年   63473篇
  1984年   47403篇
  1983年   40098篇
  1982年   23380篇
  1981年   20804篇
  1979年   41809篇
  1978年   29105篇
  1977年   24482篇
  1976年   23040篇
  1975年   23961篇
  1974年   29006篇
  1973年   27980篇
  1972年   26059篇
  1971年   23909篇
  1970年   22542篇
  1969年   21021篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
5.
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   
6.
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   
7.
8.
9.
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   
10.
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