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   1854976篇
  免费   139819篇
  国内免费   4453篇
耳鼻咽喉   26700篇
儿科学   59615篇
妇产科学   52795篇
基础医学   268265篇
口腔科学   53929篇
临床医学   164609篇
内科学   352569篇
皮肤病学   41163篇
神经病学   150971篇
特种医学   74777篇
外国民族医学   481篇
外科学   284316篇
综合类   45826篇
现状与发展   2篇
一般理论   658篇
预防医学   142094篇
眼科学   44481篇
药学   135922篇
  3篇
中国医学   3668篇
肿瘤学   96404篇
  2018年   19251篇
  2017年   15116篇
  2016年   17753篇
  2015年   20302篇
  2014年   27203篇
  2013年   41129篇
  2012年   55712篇
  2011年   58148篇
  2010年   34531篇
  2009年   31998篇
  2008年   54763篇
  2007年   58965篇
  2006年   59181篇
  2005年   57888篇
  2004年   56215篇
  2003年   54201篇
  2002年   52399篇
  2001年   78748篇
  2000年   80402篇
  1999年   67910篇
  1998年   20084篇
  1997年   18205篇
  1996年   17817篇
  1995年   16893篇
  1994年   16001篇
  1992年   54910篇
  1991年   53829篇
  1990年   52838篇
  1989年   50999篇
  1988年   47019篇
  1987年   46914篇
  1986年   44090篇
  1985年   42814篇
  1984年   32625篇
  1983年   27916篇
  1982年   17180篇
  1981年   15701篇
  1979年   31875篇
  1978年   23027篇
  1977年   19451篇
  1976年   18184篇
  1975年   19528篇
  1974年   23884篇
  1973年   23006篇
  1972年   21512篇
  1971年   20045篇
  1970年   18921篇
  1969年   17994篇
  1968年   16476篇
  1967年   14976篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
33.
We report two British cases of liver abscess, due to Klebsiella pneumoniae and associated with synchronous infection elsewhere, which required liver resection for definitive treatment. They illustrate the geographic spread of aggressive K pneumoniae liver infection and demonstrate the importance of early aggressive treatment.  相似文献   
34.
35.
36.
37.
38.
Hepatic NADPH-cytochrome P450 oxidoreductase null (HRN?) mice exhibit normal hepatic and extrahepatic biotransformation enzyme activities when compared to wild-type (WT) mice, but express no functional hepatic cytochrome P450 activities. When incubated in vitro with [14C]-diclofenac, liver microsomes from WT mice exhibited extensive biotransformation to oxidative and glucuronide metabolites and covalent binding to proteins was also observed. In contrast, whereas glucuronide conjugates and a quinone-imine metabolite were formed when [14C]-diclofenac was incubated with HRN? mouse liver, only small quantities of P450-derived oxidative metabolites were produced in these samples and covalent binding to proteins was not observed. Livers from vehicle-treated HRN? mice exhibited enhanced lipid accumulation, bile duct proliferation, hepatocellular degeneration and necrosis and inflammatory cell infiltration, which were not present in livers from WT mice. Elevated liver-derived alanine aminotransferase, glutamate dehydrogenase and alkaline phosphatase activities were also observed in plasma from HRN? mice. When treated orally with diclofenac for 7 days, at 30 mg/kg/day, the severities of the abnormal liver histopathology and plasma liver enzyme findings in HRN? mice were reduced markedly. Oral diclofenac administration did not alter the liver histopathology or elevate plasma enzyme activities of WT mice. These findings indicate that HRN? mice are valuable for exploration of the role played by hepatic P450s in drug biotransformation, but poorly suited to investigations of drug-induced liver toxicity. Nevertheless, studies in HRN? mice could provide novel insights into the role played by inflammation in liver injury and may aid the evaluation of new strategies for its treatment.  相似文献   
39.
40.
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