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   13274篇
  免费   1086篇
  国内免费   3篇
  14363篇
  2023年   36篇
  2022年   66篇
  2021年   139篇
  2020年   93篇
  2019年   116篇
  2018年   228篇
  2017年   243篇
  2016年   392篇
  2015年   618篇
  2014年   647篇
  2013年   827篇
  2012年   1099篇
  2011年   1099篇
  2010年   619篇
  2009年   530篇
  2008年   812篇
  2007年   821篇
  2006年   741篇
  2005年   765篇
  2004年   657篇
  2003年   597篇
  2002年   575篇
  2001年   196篇
  2000年   196篇
  1999年   184篇
  1998年   100篇
  1997年   96篇
  1996年   86篇
  1995年   69篇
  1994年   62篇
  1993年   52篇
  1992年   91篇
  1991年   93篇
  1990年   63篇
  1989年   92篇
  1988年   79篇
  1987年   69篇
  1986年   69篇
  1985年   64篇
  1984年   58篇
  1983年   63篇
  1982年   49篇
  1981年   48篇
  1979年   41篇
  1978年   38篇
  1976年   46篇
  1975年   40篇
  1974年   56篇
  1973年   41篇
  1971年   42篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
We present here a new, dedicated mechanical device for monitoring quick-release movements of the wrist. The ergometer was designed to easily assess musculotendinous properties during wrist flexion. Maximal voluntary contractions (MVC) and quick-release (QR) movements during wrist flexion were performed on 14 subjects. A validation of the ergometer, using a test-retest methodology, was performed to assess its reliability and sensitivity. The device has been technically and biomechanically validated in a range of situations, including inertia measurement (mean inertia was found 0.0119+/-0.0012 N m s(2) rad(-1)) and appearance of the unloading reflex. Our results indicate that the device provides highly reliable, sensitive evaluation of wrist muscle stiffness (intraclass correlation coefficient for inertia, maximal voluntary contraction and stiffness index were 0.873, 0.994 and 0.930, respectively). Its portability facilitates measurement of the influence of repetitive, occupational activity on the musculotendinous complex of the wrist flexors.  相似文献   
4.
5.
6.
Structure-activity relationships for the inhibition of thrombin and trypsin by N alpha-substituted amidinophenyl-alpha-aminoalkylcarboxylic acid amides are presented. Secondary cyclic amides of N alpha-substituted 4-amidinophenylalanine and 2-amino-5-(4-amidinophenyl)valeric acid were found to be potent and specific inhibitors of thrombin, whereas trypsin was inhibited strongly by primary amides of 2-amino-4-(4-amidinophenyl) butyric acid. For this type of inhibitor the carbon amide structure seems to play a decisive role in the enzyme-inhibitor interaction.  相似文献   
7.
A capillary electrophoresis (CE) method has been developed as an alternative method for the determination of the inorganic degradation products sulfate and sulfamate in topiramate drug product and drug substance, currently performed by ion chromatography. The anions are separated in a background electrolyte containing potassium chromate and boric acid, followed by indirect UV detection. By adding tetradecyltrimethylammonium bromide to the electrolyte, analysis is performed under co-electroosmotic flow conditions. Variations in injection volumes and migration times are compensated for by use of an internal standard. The validation of the method, which was performed according to ICH guidelines (International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use) [1], comprises specificity, accuracy, linearity, precision, sensitivity and robustness. In addition, the results of an actual tablet sample analysis obtained by this CE method are statistically shown to be in close agreement with those obtained by an ion chromatographic method.  相似文献   
8.
9.
Risk assessment is part of the risk analysis process as it is used in veterinary medicine to estimate risks related to international trade and food safety. Data from monitoring and surveillance systems (MO&SS) are used throughout the risk assessment process for hazard identification, release assessment, exposure assessment and consequence assessment. As the quality of risk assessments depends to a large extent on the availability and quality of input data, there is a close relationship between MO&SS and risk assessment. In order to improve the quality of risk assessments, MO&SS should be designed according to minimum quality standards. Second, recent scientific developments on state-of-the-art design and analysis of surveys need to be translated into field applications and legislation. Finally, knowledge about the risk assessment process among MO&SS planners and managers should be promoted in order to assure high-quality data.  相似文献   
10.
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