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   1045417篇
  免费   123050篇
  国内免费   710篇
  2016年   10862篇
  2015年   16493篇
  2014年   19133篇
  2013年   27030篇
  2012年   30460篇
  2011年   30583篇
  2010年   20695篇
  2009年   19531篇
  2008年   27737篇
  2007年   28785篇
  2006年   27047篇
  2005年   26152篇
  2004年   25939篇
  2003年   24979篇
  2002年   24438篇
  2001年   44870篇
  2000年   45773篇
  1999年   36686篇
  1998年   13920篇
  1997年   14576篇
  1996年   13842篇
  1995年   13118篇
  1994年   12962篇
  1993年   12825篇
  1992年   30918篇
  1991年   29959篇
  1990年   29388篇
  1989年   28611篇
  1988年   26587篇
  1987年   25841篇
  1986年   24086篇
  1985年   24154篇
  1984年   20245篇
  1983年   17638篇
  1982年   14068篇
  1981年   12781篇
  1980年   11958篇
  1979年   19667篇
  1978年   15820篇
  1977年   14450篇
  1976年   13677篇
  1975年   14960篇
  1974年   16170篇
  1973年   15993篇
  1972年   14546篇
  1971年   13324篇
  1970年   11504篇
  1969年   11063篇
  1968年   10017篇
  1967年   8833篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
Dr A C Srivastava has written to us to describe a case that raises the suggestion that people infected with the human immuno-deficiency virus (HIV) should carry identity cards. We asked two physicians, a general practitioner working with patients with the acquired immune deficiency syndrome (AIDS), and a general practitioner with a special interest in medical ethics to respond to the broad issues raised by Dr Srivastava''s letter.  相似文献   
942.
943.
944.
Experimental projects have demonstrated the technical feasibility of systems of accessible, affordable health care. These projects have relied extensively on non-professional community health workers. However, large-scale implementation of these schemes will require new management procedures that are both responsive to rural health needs and congruent with national institutions. This paper identifies the need to establish institutional mechanisms to mobilize essential inputs, promote acceptance by beneficiaries, maintain quality standards, recruit and retain field staff, and achieve accountability for resources. It then outlines methods for developing these institutions. It stresses the need for both formal, bureaucratic organizations and informal organizations of clients. It also identifies the need to consider administrative and institutional resources in determining the appropriateness of a health care technology.  相似文献   
945.
946.
A peroxidase-anti-peroxidase (PAP) method using polyclonal anti-PR antibodies was used to localize progesterone receptor (PR) electron microscopically in the chick oviduct. The immunoreaction precipitate indicating PR was localized inside the nuclei of epithelial, glandular and stromal cells. In the estrogen withdrawn oviduct cytoplasmic immunoreaction precipitate was not seen. Inside the nucleus unoccupied PR was localized mainly like the heterochromatin. As visualized by the PAP technique, the localization of PR was not systematically changed after progesterone administration. In conclusion, we suggest that progesterone receptor in the chick oviduct is an intranuclear protein.  相似文献   
947.
A spectroscopic method employing pulsed dye laser instrumentation is described for the determination of the 1H2O/2H2O composition of aqueous solutions by the measurement of reciprocal excited state lifetimes of EuEDTA-. The reciprocal lifetimes, gamma-1, of the 1H2O/2H2O mixtures increase linearly with the mole fraction of 1H2O. For EuEDTA- the relationship between gamma-1 and the mole fraction, chi H, of 1H2O in 1H2O/2H2O mixtures is expressed by the equation chi H = 0.37 gamma-1-0.152, with a sensitivity in chi H of +/- 0.02. The reciprocal lifetimes are independent of pH in the range 5.1 to 10.5, changes in ionic strength, and the type of buffer used in EuEDTA- containing solutions.  相似文献   
948.
949.
950.
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