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   679485篇
  免费   73678篇
  国内免费   329篇
  2018年   5723篇
  2016年   7533篇
  2015年   10049篇
  2014年   11924篇
  2013年   17340篇
  2012年   19161篇
  2011年   19699篇
  2010年   13231篇
  2009年   12388篇
  2008年   17591篇
  2007年   18402篇
  2006年   17497篇
  2005年   16858篇
  2004年   16697篇
  2003年   16297篇
  2002年   16107篇
  2001年   31574篇
  2000年   31902篇
  1999年   25153篇
  1998年   8387篇
  1997年   8861篇
  1996年   8075篇
  1995年   7732篇
  1994年   7587篇
  1993年   7674篇
  1992年   21039篇
  1991年   20732篇
  1990年   20208篇
  1989年   19923篇
  1988年   18654篇
  1987年   17535篇
  1986年   16144篇
  1985年   16471篇
  1984年   13347篇
  1983年   11551篇
  1982年   8704篇
  1981年   7789篇
  1980年   7301篇
  1979年   12626篇
  1978年   9850篇
  1977年   9206篇
  1976年   8548篇
  1975年   9394篇
  1974年   10103篇
  1973年   9967篇
  1972年   9095篇
  1971年   8321篇
  1970年   7213篇
  1969年   7154篇
  1968年   6566篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Ten asthmatic children with a history of cough and wheeze after drinking a cola drink performed histamine inhalation tests before and 30 minutes after a drink of Pepsi-Cola, soda water, and water on three separate study days. There was no significant change in baseline peak expiratory flow after any of the three drinks. Sensitivity to histamine was increased after the cola drink (p less than 0.005) but was not significantly different after soda water or water. The detection of change in sensitivity to histamine appears to be a simple and effective method of testing for food sensitivity in asthma.  相似文献   
993.
Idiopathic calcinosis of the scrotum is a rare disease that may cause massive deformation of the scrotal wall. The first patient we present was also known to have neurofibromatosis. In the second patient we describe, nodules of idiopathic calcinosis of the scrotum were seen with walls that evidenced no epithelial lining, as well as calcification in epithelial cysts. At present, the only possible treatment is excision, and we excised the afflicted skin without problems in primary wound closure.  相似文献   
994.
Three acetotrophicMethanosarcina species, which included marine, nonmarine, and thermophilic strains, were grown on acetate in a 10-liter pH auxostat. Specific growth rates and molar growth yields were constant throughout growth. Cell yields were up to 18-fold greater than previously reported. These properties of the pH auxostat indicate that it is a preferred culture method for the biochemical study of methanogenesis from acetate.  相似文献   
995.
996.
997.
A test system permitting the detection of influenza virus protein M at a concentration of 0.1-0.5 ng/ml in ELISA has been developed. The use of this system made it possible to detect influenza viruses A and B directly in crude virus-containing material and clinical samples obtained from influenza patients. During the outbreak of influenza in the spring of 1983 ELISA was successfully used for the rapid diagnosis of influenza, and some of its advantages in comparison with the conventional immunofluorescence test were thus demonstrated. To overcome difficulties arising from the low immunogenic potency of protein M, in the process of obtaining diagnostic sera and ascitic fluids the animals were immunized with the conjugate of protein M and polyelectrolite, which ensured considerable activation of humoral immune response.  相似文献   
998.
Human Tamm-Horsfall urinary glycoprotein from an individual of the blood group Sd(a+) phenotype was tritium-labelled by treatment with galactose oxidase and sodium boro[3H]hydride and was then digested with endo-beta-galactosidase. A series of dialysable, labelled fragments was released from which a pentasaccharide was isolated that strongly inhibited the agglutination of Sd(a+) red cells by human anti-Sda serum and hence contained the Sda determinant structure. Reduction, methylation analysis and sequential exo-glycosidase digestion established the structure of the pentasaccharide as: GalNAc beta(1 leads to 4)[NeuAc(2 leads to 3)]Gal beta(1 leads to 4)GlcNAc beta(1 leads to 3)Gal  相似文献   
999.
Home range, dispersal and the clan system of impala   总被引:1,自引:0,他引:1  
  相似文献   
1000.
The study of the effect of gamma globulin introduced in different doses (0.5 and 0.25 ml/mg) in combination with Fermi rabies vaccine (observations on humans were made) and with cerebral rabies vaccine inactivated by UV irradiation (in animal experiments) demonstrated that the injection of the higher doses of gamma globulin resulted in lower geometrical mean of antibody titers. Therefore, in combined administration of rabies vaccine and gamma globulin for postexposure rabies prevention it is advisable to reduce the dose of gamma globulin by one-half.  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