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   557201篇
  免费   61549篇
  国内免费   351篇
  619101篇
  2018年   5680篇
  2017年   5478篇
  2016年   7777篇
  2015年   10164篇
  2014年   11836篇
  2013年   17094篇
  2012年   19227篇
  2011年   19206篇
  2010年   12765篇
  2009年   11591篇
  2008年   16700篇
  2007年   17151篇
  2006年   16224篇
  2005年   15399篇
  2004年   15247篇
  2003年   14523篇
  2002年   13982篇
  2001年   28790篇
  2000年   28730篇
  1999年   22258篇
  1998年   6905篇
  1997年   7404篇
  1996年   6862篇
  1995年   6354篇
  1994年   6099篇
  1993年   6059篇
  1992年   17159篇
  1991年   16392篇
  1990年   15795篇
  1989年   15294篇
  1988年   13978篇
  1987年   12972篇
  1986年   12090篇
  1985年   11876篇
  1984年   9746篇
  1983年   8133篇
  1982年   6060篇
  1981年   5415篇
  1980年   5149篇
  1979年   8985篇
  1978年   6845篇
  1977年   6310篇
  1976年   5696篇
  1975年   6277篇
  1974年   6799篇
  1973年   6573篇
  1972年   5999篇
  1971年   5443篇
  1970年   4690篇
  1969年   4408篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
101.
Extensibility, contractile function and resistance to excess calcium of the right atrium myocardium were studied in normotensive Wistar-Kyoto and August rats and in spontaneously hypertensive rats (SHR). It was shown that long-term stress results in a decrease in the measured parameters in normotensive animals. SHR do not show any stress-induced disturbances. It was discovered that in intact SHR rats, the myocardium has a greater resistance to excess calcium, indirect evidence for higher efficiency of the Ca-pump of the sarcoplasmic reticulum in cardiomyocytes of SHR animals, which is apparently a constituent part of the mechanism of such animals' heart increased resistance to stress-induced damage.  相似文献   
102.
—A resolution of the enhancement of protein synthesis in the visual cortex of rats during first exposure to light (Richardson and Rose , 1972) was achieved by polyacrylamide gel electrophoresis using a double-labelling technique. Differential incorporation of lysine was established between exposed and control animals in two fractions of the soluble proteins and seven fractions of the insoluble proteins. This suggests that exposure to a new experience of this type involves a specific effect on protein synthesis, rather than a general stimulation across all fractions.  相似文献   
103.
104.
A new gas-liquid chromatographic method was developed for the determination of diethylether in whole blood. Ether was quantitated by peak area ratio analysis with n-propanol as the internal standard using a flame ionization detector. Blood ether concentrations were determined in cats undergoing inhalational anesthesia by ether in oxygen. In normal spontaneously breathing cats, anesthesia began at ether concentrations of about 0.6 g/l, and respiratory arrest occurred at 2.4 g/l and above. Mean arterial blood pressure was well maintained throughout the entire anesthetic range. In spinal artificially respired animals, mean arterial blood pressure correlated inversely with blood ether concentration. The data suggest that decline in blood pressure may be a useful sign of ether toxicity in spinal cats.  相似文献   
105.
106.
107.
From three Fouquieria sp. 12 iridoid glucosides were isolated and identified. Eight of these were structurally related to galioside (monotropein methylester), while four were hydroxy substitution products of deoxyloganin. In three cases the glucoside occurred together with the corresponding 10-O-acetate.  相似文献   
108.
An indwelling nasal suction tampon is described that effectively controls both intraoperative and postoperative nasal hemorrhage. The significant benefits of this device are better intraoperative control for the surgeon and less complicated postoperative recovery. I do not have any financial involvement in this device, but I would like other nasal surgeons to benefit from its particular advantages. The device is available under the trade name Instant and may be obtained from Innovations by Westmed, 3351 E. Hemisphere Loop, Tucson, Ariz. 85706; (602) 294-7987.  相似文献   
109.
110.
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