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   29113篇
  免费   3687篇
  国内免费   3篇
  32803篇
  2021年   286篇
  2018年   287篇
  2017年   258篇
  2016年   477篇
  2015年   753篇
  2014年   832篇
  2013年   1067篇
  2012年   1298篇
  2011年   1200篇
  2010年   771篇
  2009年   739篇
  2008年   1099篇
  2007年   1084篇
  2006年   1003篇
  2005年   969篇
  2004年   946篇
  2003年   949篇
  2002年   917篇
  2001年   916篇
  2000年   913篇
  1999年   775篇
  1998年   414篇
  1997年   380篇
  1996年   367篇
  1995年   319篇
  1994年   321篇
  1993年   335篇
  1992年   682篇
  1991年   629篇
  1990年   611篇
  1989年   660篇
  1988年   563篇
  1987年   602篇
  1986年   475篇
  1985年   564篇
  1984年   478篇
  1983年   385篇
  1982年   398篇
  1981年   358篇
  1980年   328篇
  1979年   435篇
  1978年   382篇
  1977年   337篇
  1976年   313篇
  1975年   334篇
  1974年   382篇
  1973年   361篇
  1972年   305篇
  1971年   285篇
  1969年   247篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
Software for fitting of NMR spectra in MATLAB is presented. Spectra are fitted in the frequency domain, using Fourier transformed lineshapes, which are derived using the experimental acquisition and processing parameters. This yields more accurate fits compared to common fitting methods that use Lorentzian or Gaussian functions. Furthermore, a very time-efficient algorithm for calculating and fitting spectra has been developed. The software also performs initial peak picking, followed by subsequent fitting and refinement of the peak list, by iteratively adding and removing peaks to improve the overall fit. Estimation of error on fitting parameters is performed using a Monte-Carlo approach. Many fitting options allow the software to be flexible enough for a wide array of applications, while still being straightforward to set up with minimal user input.  相似文献   
93.
94.
D H Smith 《CMAJ》1997,157(9):1202-1203
  相似文献   
95.
96.
97.
Summary Myocardial cell culture methods are now well established for animal and fetal human tissue. We present here a method for harvesting and culturing adult human atrial myocardiocytes. Cells are obtained from fresh atrial tissue normally discarded after being removed to cannulate the right atrium during open heart surgery. The atrial tissue is minced and then digested using collagenase. The single cell suspension is initially cultured in serum-containing growth medium, then transferred to defined medium, selective for myocardial cell growth. The cells are characterized by immunoperoxidase stains and transmission electron microscopy. The cultured cells stain positive for myoglobin, whereas control cultured fibroblasts and endothelial cells do not. Electron microscopy shows the presence of numerous myofibrils, Z-bodies, pleomorphic mitochondria, and secretory granules. The chronological age of the donor was an important factor in culturing the adult tissue, the younger tissue correlated with a higher success rate. This method provides a means for in vitro study of human adult myocardial cells and provides guidelines for appropriate atrial tissue to use.  相似文献   
98.
99.
100.
Heart rate at rest and during increasing workloads was measured in a double blind study of 12 patients with chronic atrial fibrillation when serum concentrations of digoxin were nil and at low and high therapeutic values. Twelve normal subjects were studied for comparison. The heart rate at all levels of exercise in most patients with atrial fibrillation was not adequately controlled by any serum digoxin concentration tested despite a reduction in heart rate with increasing serum digoxin concentrations. Control of the resting heart rate, even in patients with high serum digoxin concentrations, did not ensure adequate control of the heart rate during work rates equivalent to regular daily activities.  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