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   2648626篇
  免费   193326篇
  国内免费   5141篇
耳鼻咽喉   36520篇
儿科学   88535篇
妇产科学   72703篇
基础医学   374733篇
口腔科学   74805篇
临床医学   236473篇
内科学   519876篇
皮肤病学   59253篇
神经病学   206311篇
特种医学   102473篇
外国民族医学   868篇
外科学   404126篇
综合类   59570篇
现状与发展   5篇
一般理论   849篇
预防医学   198522篇
眼科学   61768篇
药学   194644篇
  8篇
中国医学   6075篇
肿瘤学   148976篇
  2019年   20075篇
  2018年   29060篇
  2017年   21978篇
  2016年   24180篇
  2015年   27492篇
  2014年   38263篇
  2013年   56921篇
  2012年   78540篇
  2011年   82959篇
  2010年   49461篇
  2009年   46548篇
  2008年   78042篇
  2007年   83171篇
  2006年   83908篇
  2005年   80717篇
  2004年   78467篇
  2003年   75159篇
  2002年   72941篇
  2001年   133968篇
  2000年   137673篇
  1999年   115468篇
  1998年   30900篇
  1997年   27380篇
  1996年   27694篇
  1995年   26495篇
  1994年   24641篇
  1993年   22770篇
  1992年   89366篇
  1991年   86816篇
  1990年   83943篇
  1989年   80469篇
  1988年   73764篇
  1987年   72334篇
  1986年   67782篇
  1985年   64519篇
  1984年   47955篇
  1983年   40589篇
  1982年   23097篇
  1981年   20794篇
  1979年   42517篇
  1978年   29414篇
  1977年   25054篇
  1976年   23300篇
  1975年   24999篇
  1974年   29870篇
  1973年   28518篇
  1972年   26519篇
  1971年   24213篇
  1970年   22702篇
  1969年   20968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.
6.
7.
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   
8.
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   
9.
10.
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