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   1121450篇
  免费   81881篇
  国内免费   3759篇
耳鼻咽喉   15013篇
儿科学   36312篇
妇产科学   30289篇
基础医学   165040篇
口腔科学   30760篇
临床医学   101700篇
内科学   215559篇
皮肤病学   26875篇
神经病学   89197篇
特种医学   45398篇
外国民族医学   305篇
外科学   165441篇
综合类   24248篇
现状与发展   3篇
一般理论   413篇
预防医学   84372篇
眼科学   25842篇
药学   83159篇
  3篇
中国医学   3507篇
肿瘤学   63654篇
  2021年   11270篇
  2019年   10263篇
  2018年   14224篇
  2017年   11174篇
  2016年   13334篇
  2015年   16106篇
  2014年   20865篇
  2013年   29533篇
  2012年   40214篇
  2011年   41601篇
  2010年   24731篇
  2009年   22790篇
  2008年   36236篇
  2007年   37543篇
  2006年   37261篇
  2005年   35533篇
  2004年   33998篇
  2003年   32235篇
  2002年   30572篇
  2001年   49313篇
  2000年   50157篇
  1999年   41942篇
  1998年   11985篇
  1997年   10726篇
  1996年   10628篇
  1995年   10193篇
  1994年   9440篇
  1993年   8799篇
  1992年   32878篇
  1991年   32049篇
  1990年   31523篇
  1989年   30339篇
  1988年   27555篇
  1987年   27723篇
  1986年   25718篇
  1985年   24907篇
  1984年   18617篇
  1983年   15684篇
  1982年   9412篇
  1979年   17049篇
  1978年   12356篇
  1977年   10418篇
  1976年   9863篇
  1975年   10281篇
  1974年   12440篇
  1973年   11945篇
  1972年   10973篇
  1971年   10188篇
  1970年   9438篇
  1969年   8776篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Diseases like rotavirus afflict both upper- and lower-income countries, but most serious illnesses and deaths occur among the latter. It is a vital public health issue that vaccines for these types of global diseases can recover research and development (R&D) costs from high-priced markets quickly so that manufacturers can offer affordable prices to lower-income nations. Cost recovery depends on how high R&D costs are, and this study attempts to replace high, unverified estimates with lower, more verifiable estimates for two new vaccines, RotaTeq (Merck) and Rotarix (GlaxoSmithKline or GSK), based on detailed searches of public information and follow-up interviews with senior informants. We also offer a new perspective on “cost of capital” as a claim for recovery from public bodies. Our estimates suggest that companies can recover all fixed costs quickly from affluent markets and thus can offer these vaccines to lower-income countries at prices they can afford. Better vaccines are a shared project between companies and public health agencies; greater transparency and consistency in reporting of R&D costs is needed so that fair prices can be established.  相似文献   
992.
993.
994.
995.
996.
The Blalock-Taussig operation is of benefit to any patient who suffers from lack of adequate pulmonary blood flow, provided the structure of the heart is such that it is able to adjust to the altered circulation.Experience has shown that a patient with a tetralogy of Fallot can adjust to the altered circulation. The other types of malformation which have been improved by operation are those with a cardiac contour similar to that of a tetralogy of Fallot with left axis deviation, those with partial rotation of the heart on its axis, possibly those with “pure” pulmonary stenosis and an auricular septal defect, and a few with unusual arrhythmias. In atypical cases an effort is made to determine whether the condition is such that the patient can be helped by increasing the circulation to the lungs.The six criteria essential for successful operation are (1) the primary difficulty must be lack of adequate pulmonary blood flow; (2) there must be a pulmonary artery to which to anastomose the systemic artery; (3) a systemic artery must be available for the anastomosis; (4) the difference in pressure between the systemic and pulmonic circulations must be sufficiently great for blood to flow from the aorta to the lungs; (5) the structure of the lungs must be such that the patient can tolerate the collapse of one lung and the temporary occlusion of one pulmonary artery; and (6) the structure of the heart must be such that it can adjust to the altered circulation. The methods for the determination of each of these factors are discussed.In an analysis of the structure of the heart it is emphasized that (1) venous blood must be directed to the systemic circulation, (2) the increased volume of oxygenated blood which is returned from the lungs must be able to reach the aorta; (3) the structure of the heart must be such as to permit the continuous circulation of the blood at an accelerated rate; (4) the structure of the heart must also be such that the operation does not cause progressive cardiac enlargement. Each of these factors is analyzed.The effect of the altered circulation on the size of the heart is discussed in the light of the long-time results of the operation. Less than 5 per cent of the patients have shown progressive cardiac enlargement or died of cardiac failure. Thirty per cent have shown no increase in heart size. Thirty per cent have shown increase in heart size during the first three weeks after operation and then have adjusted to the load, and 30 per cent have shown cardiac enlargement between the time of discharge and the six-month checkup and thereafter have shown no further increase in heart size.In general, the results from the use of the subclavian artery, as estimated by the oxygen saturation of the arterial blood, the red blood cell count, and the hemoglobin level, have been as beneficial as when the innominate artery has been used for the anastomosis and, moreover, this former group of patients has shown less increase in the size of the heart.A child with a tetralogy of allot has a 90 per cent chance of being greatly improved by the operation and an equally good chance of maintaining that improvement.  相似文献   
997.
998.
999.
1000.
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