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   418737篇
  免费   35643篇
  国内免费   297篇
  2018年   4877篇
  2017年   4667篇
  2016年   6090篇
  2015年   6359篇
  2014年   8134篇
  2013年   11604篇
  2012年   13173篇
  2011年   14106篇
  2010年   9706篇
  2009年   8590篇
  2008年   12427篇
  2007年   12840篇
  2006年   12263篇
  2005年   11576篇
  2004年   11468篇
  2003年   11123篇
  2002年   10977篇
  2001年   18988篇
  2000年   18845篇
  1999年   14580篇
  1998年   4462篇
  1997年   4460篇
  1996年   4288篇
  1995年   3910篇
  1994年   3814篇
  1992年   11405篇
  1991年   11319篇
  1990年   11308篇
  1989年   11097篇
  1988年   10316篇
  1987年   9704篇
  1986年   8745篇
  1985年   9267篇
  1984年   7341篇
  1983年   6225篇
  1982年   4341篇
  1981年   3912篇
  1980年   3728篇
  1979年   6792篇
  1978年   5174篇
  1977年   4781篇
  1976年   4664篇
  1975年   5475篇
  1974年   5949篇
  1973年   5965篇
  1972年   5278篇
  1971年   4966篇
  1970年   4306篇
  1969年   4092篇
  1968年   3865篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
911.
912.
The occurrence of HBsAg carriership in Leningrad has been found to be 1.4% according to the results of countercurrent immunoelectroosmophoresis (CIEO) and 2.1% according to the results of the passive hemagglutination (PHA) test. In children HBsAg occurs with higher frequency: 1.9% according to the results of CIEO and 3.4% according to the results of the PHA test. The latter test reveals HBsAg carriers more completely, especially in women who have usually less pronounced antigenemia than men. Most of chronic HBsAg carriers are patients with chronic forms of hepatitis B (chronic active hepatitis and chronic persistent hepatitis); frequently they become the source of infection among their relatives under the conditions of family contacts. A complex of antiepidemic measures is necessary in the foci of chronic HBsAg carriership.  相似文献   
913.
Intoxication with bacterial lipopolysaccharide (endotoxin) is accompanied by considerable rearrangements in the systems of blood microcirculation and water metabolism of the liver. These rearrangements are manifested as increased sinusoid area, changed total area of the cytoplasm and nuclei as well as the nucleocytoplasmic ratio in hepatocytes, increased content of total water in the organ, and changed magnetic relaxation properties (spin-lattice and spin-spin relaxation times). Preliminary parasympathetic denervation of the liver (vagotomy) changes the pattern of the organ response to bacterial endotoxin poisoning as indicated by the kinetics of studied morphological and biophysical parameters.  相似文献   
914.
A new staining method is described using naphthalene black 12B and Gurr's improved R66 Giemsa for staining all known crystal types produced by Bacillus thuringiensis.  相似文献   
915.
A quick test has been developed to identify phytopathogenic virus strains by variations in their photoluminescence parameters. When heated, the virus suspension shows a jumpwise drop or rise in fluorescence intensity caused by conformational changes in the macromolecules of the virion protein capsules. The relative value of the jump in fluorescence intensity and the temperature value at which the jump occurs are essentially strain-specific. The minimum time needed for one test is from 15 to 20 minutes.  相似文献   
916.
Urease was immobilized on O-alkylated nylon tubes coated with polyaminated derivatives of starch or dextran. The specific activity of the enzyme coil and the relative stability of the immobilized enzyme, compared with immobilized urease derived from other nylon tube modifications, were enhanced. Also, the nonspecific binding of urease to O-alkylated nylon tubes was virtually eliminated by the coating process.  相似文献   
917.
918.
919.
Recent ultrastructural studies have revealed that there are differences in endothelial cell shape and cytoskeletal architecture between the arterial and ventricular faces of developing semilunar valves. In the present work we have analyzed valvular endothelial cell response to taxol in the chick embryo. Following taxol administration, abnormal mitotic cells appear in the endothelium of both faces of the cusps. Interphase cells show few structural alterations. No differential response of the valvular endothelium to the drug was observed in the arterial or ventricular faces of the cusps.  相似文献   
920.
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