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   1293176篇
  免费   98976篇
  国内免费   2009篇
耳鼻咽喉   18557篇
儿科学   44739篇
妇产科学   35436篇
基础医学   184109篇
口腔科学   34081篇
临床医学   113000篇
内科学   260687篇
皮肤病学   28334篇
神经病学   101762篇
特种医学   51789篇
外国民族医学   660篇
外科学   198226篇
综合类   27434篇
现状与发展   1篇
一般理论   386篇
预防医学   97407篇
眼科学   28104篇
药学   95655篇
  3篇
中国医学   2437篇
肿瘤学   71354篇
  2018年   13442篇
  2017年   10186篇
  2016年   11107篇
  2015年   12609篇
  2014年   17504篇
  2013年   26737篇
  2012年   36721篇
  2011年   38750篇
  2010年   23228篇
  2009年   22180篇
  2008年   37227篇
  2007年   39859篇
  2006年   40076篇
  2005年   39038篇
  2004年   38167篇
  2003年   36998篇
  2002年   36345篇
  2001年   64422篇
  2000年   66975篇
  1999年   56800篇
  1998年   15313篇
  1997年   13909篇
  1996年   14367篇
  1995年   13589篇
  1994年   12878篇
  1993年   11908篇
  1992年   44896篇
  1991年   43741篇
  1990年   42521篇
  1989年   40396篇
  1988年   37135篇
  1987年   36463篇
  1986年   33838篇
  1985年   32516篇
  1984年   24358篇
  1983年   20448篇
  1982年   11827篇
  1981年   10775篇
  1980年   9622篇
  1979年   21494篇
  1978年   14931篇
  1977年   12610篇
  1976年   11795篇
  1975年   12731篇
  1974年   14783篇
  1973年   14241篇
  1972年   13069篇
  1971年   11825篇
  1970年   11133篇
  1969年   10102篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
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   
13.
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   
14.
15.
16.
Pharmaceutical Chemistry Journal - Three extracts were produced from the above-ground part of the meadowsweet Filipendula ulmaria (L.) Maxim. using water, 40% ethanol, and 70% ethanol. Comparative...  相似文献   
17.
18.
19.
Haemophilia is a common cause of genetically inherited bleeding disorders. Pseudotumours occur in 1–2 % of persons with severe forms of haemophilia. These are a result of repeated haemorrhage into soft tissues, subperiosteum or a site of bone fracture with inadequate resorption of the extravasated blood. There are a number of therapeutic alternatives for this dangerous condition: surgical removal, percutaneous management, irradiation, embolization etc. In this case report, we describe the natural history, clinical course and successful surgical management of a patient with haemophilia who presented with a massive pseudotumour. We also briefly review the relevant literature on the various therapeutic modalities that have been implemented in the management of this rare complication. Though surgeons may be averse to operate on haemophiliacs, primary surgical management as done in our case may prove to be the definitive treatment option for such patients.  相似文献   
20.
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