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   12655篇
  免费   357篇
  国内免费   2篇
  13014篇
  2021年   143篇
  2020年   111篇
  2019年   133篇
  2018年   282篇
  2017年   235篇
  2016年   334篇
  2015年   336篇
  2014年   411篇
  2013年   524篇
  2012年   525篇
  2011年   545篇
  2010年   340篇
  2009年   267篇
  2008年   344篇
  2007年   393篇
  2006年   395篇
  2005年   351篇
  2004年   299篇
  2003年   335篇
  2002年   293篇
  2001年   283篇
  2000年   226篇
  1999年   176篇
  1998年   90篇
  1992年   231篇
  1991年   221篇
  1990年   178篇
  1989年   212篇
  1988年   230篇
  1987年   236篇
  1986年   214篇
  1985年   241篇
  1984年   193篇
  1983年   160篇
  1980年   83篇
  1979年   230篇
  1978年   152篇
  1977年   134篇
  1976年   134篇
  1975年   166篇
  1974年   261篇
  1973年   260篇
  1972年   249篇
  1971年   241篇
  1970年   255篇
  1969年   245篇
  1968年   184篇
  1967年   185篇
  1966年   166篇
  1965年   123篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
A robust method for selection of variables with the greatest discriminatory power is presented in the paper. The method deals with the two groups of data problem. An application of the method to some respiratory disease data and comparisons with classical procedures are given, also.  相似文献   
22.
Coagulation and fibrinolysis were measured in the portal and peripheral circulation in 15 rabbits after ligation of the superior mesenteric artery. It was found that the local coagulation syndrome in the mesenteric region can be recognized by tests in blood samples taken from the peripheral circulation area.  相似文献   
23.
The Escherichia coli dnaW mutation is an allele of the adk gene   总被引:3,自引:0,他引:3  
Summary A dnaW mutant, isolated on the basis of inability to effect conjugal DNA transfer at high temperature, has been shown by complementation and enzyme assay to be defective in the adk (adenylate kinase; EC 2.7.4.3) locus. The adk mutant, known to have reduced ATP concentration at the nonpermissive temperature (Cousin and Belaich 1966), was used to demonstrate a donor energy requirement for stable aggregate formation and for chromosome transfer in conjugation.  相似文献   
24.
In chronic renal failure AMP-deaminase operates in the erythrocytes at a much higher velocity than in healthy subjects, with a simultaneous shift from the AMP-adenine-inosine-hypoxanthine pathway (55% and 19%, respectively) to the pathway initiated by AMP-deaminase (45% and 81%, respectively).  相似文献   
25.
26.
27.
28.
The development of tolerance to ethanol-induced hypothermia and hypnosis, and cross-tolerance with morphine was studied in mice and rats. Ethanol significantly decreased the body temperature in rats (3.0 and 3.2 g/kg) and in mice (3.5 and 4.0 g/kg). Chronic administration of ethanol resulted in the tolerance not only to ethanol hypothermia but also to hypothermic effects of morphine in examined animals. Implantation of morphine pellets caused the development of cross tolerance to ethanol-induced hypothermia in rats but not in mice. The hypnotic effect of ethanol was significantly shorter in chronic alcoholized rats but not in morphine-implanted rats. Neither chronic ethanol administration nor implantation of morphine pellets changed the duration of ethanol-induced hypnosis in mice. These results seem to support the hypothesis on the opiate-like mechanism of ethanol action.  相似文献   
29.
30.
The fluorometric method is described for determination of the final product of dopamine metabolism homovanillic acid in urine, amniotic fluid and tissue extracts. The metabolite was isolated using three chromatographic columns (1-Amberlit CG-50, 2-Dowex AG 1 x 2, 8-Aluminium oxide). Oxidation of eluates to emitter was done with potassium ferricyanide in alkalic medium. The use of internal standards made high recovery of compound and a good specificity and sensitivity of detection.  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