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   34994篇
  免费   1353篇
  国内免费   20篇
  2020年   389篇
  2019年   476篇
  2018年   693篇
  2017年   741篇
  2016年   714篇
  2015年   540篇
  2014年   593篇
  2013年   2815篇
  2012年   1079篇
  2011年   1134篇
  2010年   762篇
  2009年   743篇
  2008年   1033篇
  2007年   974篇
  2006年   865篇
  2005年   740篇
  2004年   681篇
  2003年   702篇
  2002年   654篇
  2001年   1256篇
  2000年   1231篇
  1999年   893篇
  1998年   388篇
  1997年   322篇
  1996年   312篇
  1994年   317篇
  1992年   737篇
  1991年   708篇
  1990年   686篇
  1989年   634篇
  1988年   598篇
  1987年   603篇
  1986年   569篇
  1985年   624篇
  1984年   494篇
  1983年   386篇
  1979年   489篇
  1978年   354篇
  1977年   336篇
  1976年   319篇
  1975年   432篇
  1974年   438篇
  1973年   491篇
  1972年   398篇
  1971年   335篇
  1970年   326篇
  1969年   336篇
  1968年   396篇
  1967年   344篇
  1966年   394篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
871.
872.
873.
874.
Summary We have entered into a new era of medical achievement with the development of successful transplantation of human organs. The transplantation of the heart has aroused the greatest scientific interest and at the same time created serious new problems of an ethical and legal nature. It has been necessary to develop new criteria to determine the moment of death of the donor in order to ensure continued life for the recipient. The decision of the moment of death should be made by a small team of skilled physicians interested in furthering this important development, but not as emotionally involved as are the surgeons awaiting the chance to prolong their patient's life with a new heart. Available and suitable hearts will probably always be in very short supply, and the selection of recipients will therefore become critical if the procedure proves to be widely acceptable.New laws will be essential before this process can be adopted in many states and countries. The cost in terms of total resources is so large that careful evaluation of the long-term results must be undertaken after a reasonable number of patients have been operated on and observed, perhaps at the end of the second year following the first procedure. Since the cost of each operation of this type approximates that of the education of several young physicians who could care for thousands of patients during their life span, a good hard look at the potential benefits and ultimate values is in order. At this point in time it is extremely important that this type of surgery be encouraged but limited to those prepared to undertake it with maximum skill and minimal risk. At present it must be recognized as a great experiment rather than a therapeutic triumph for general application.  相似文献   
875.
876.
877.
878.
879.
A 16-yr-old retarded male, diagnosed organically blind and treated by those around him as a blind person, was given practice in discriminating visual stimuli. After training, he responded with significantly better than chance accuracy in a choice situation in which stimuli were as small as 18 pt Futura Medium type. In addition, he was trained to look at the experimenter's eyes when instructed to do so. Control procedures revealed that it was the reinforcement contingency that functioned to establish and maintain eye contact. Eye contact with the experimenter generalized in a limited way to situations in which this behavior was not reinforced, though not to a neutral individual. When the boy was required to use visual cues to help himself in a cafeteria line, he soon emitted the necessary behaviors, where formerly he had been assisted by others. Resumption of assistance markedly decreased self-help, suggesting that continued use of any newly learned skills would depend on the response of the individuals in his environment. The boy also learned eating behavior that appeared to require the use of visual cues.  相似文献   
880.
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