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   1775293篇
  免费   126804篇
  国内免费   3775篇
耳鼻咽喉   22371篇
儿科学   58330篇
妇产科学   47426篇
基础医学   250835篇
口腔科学   49186篇
临床医学   156445篇
内科学   350249篇
皮肤病学   39061篇
神经病学   139637篇
特种医学   67761篇
外国民族医学   242篇
外科学   271740篇
综合类   39627篇
现状与发展   4篇
一般理论   531篇
预防医学   131775篇
眼科学   41004篇
药学   127833篇
  7篇
中国医学   4481篇
肿瘤学   107327篇
  2021年   12791篇
  2019年   13531篇
  2018年   29522篇
  2017年   22938篇
  2016年   25835篇
  2015年   19275篇
  2014年   26467篇
  2013年   38182篇
  2012年   55353篇
  2011年   64044篇
  2010年   39683篇
  2009年   35785篇
  2008年   60449篇
  2007年   65815篇
  2006年   55474篇
  2005年   54325篇
  2004年   52995篇
  2003年   51471篇
  2002年   48609篇
  2001年   92053篇
  2000年   94082篇
  1999年   77127篇
  1998年   19911篇
  1997年   17512篇
  1996年   17535篇
  1995年   16892篇
  1994年   15450篇
  1993年   14205篇
  1992年   57501篇
  1991年   55406篇
  1990年   53099篇
  1989年   50854篇
  1988年   46234篇
  1987年   45057篇
  1986年   42319篇
  1985年   40083篇
  1984年   29411篇
  1983年   24973篇
  1982年   13981篇
  1979年   25621篇
  1978年   17637篇
  1977年   14926篇
  1976年   13943篇
  1975年   14565篇
  1974年   17664篇
  1973年   16952篇
  1972年   15674篇
  1971年   14455篇
  1970年   13463篇
  1969年   12552篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
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   
43.
44.
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   
45.
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   
46.
47.
48.
49.
50.
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