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   622796篇
  免费   60168篇
  国内免费   1226篇
  684190篇
  2018年   16254篇
  2017年   14988篇
  2016年   13922篇
  2015年   9433篇
  2014年   10877篇
  2013年   15696篇
  2012年   21122篇
  2011年   29497篇
  2010年   22957篇
  2009年   18446篇
  2008年   24373篇
  2007年   26346篇
  2006年   15091篇
  2005年   14712篇
  2004年   14996篇
  2003年   14400篇
  2002年   13699篇
  2001年   28623篇
  2000年   28395篇
  1999年   22058篇
  1998年   6791篇
  1997年   7351篇
  1996年   6781篇
  1995年   6259篇
  1994年   6028篇
  1993年   6030篇
  1992年   17098篇
  1991年   16362篇
  1990年   15743篇
  1989年   15252篇
  1988年   13968篇
  1987年   12975篇
  1986年   12069篇
  1985年   11840篇
  1984年   9707篇
  1983年   8126篇
  1982年   6042篇
  1981年   5411篇
  1980年   5147篇
  1979年   8964篇
  1978年   6845篇
  1977年   6302篇
  1976年   5672篇
  1975年   6276篇
  1974年   6782篇
  1973年   6572篇
  1972年   6226篇
  1971年   5699篇
  1970年   4695篇
  1969年   4417篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
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   
113.
114.
115.
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   
116.
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   
117.
118.
119.
120.
Convenient extraction and radioimmunoassay methods for measurement of leukotrienes C4 and D4 (LTC4 and LTD4) in biological fluids are described. LTC4 or LTD4 in plasma was extracted with acetonitrile, and the extract was washed with dichloromethane then adjusted to pH 3.5 or 6.0, respectively. Each leukotriene was partially purified by using a C18-bonded silica cartridge and quantitated by radioimmunoassay. Amounts of LTC4 and LTD4 in the range of 0.025-1.6 ng could be assayed in plasma. This procedure was employed to examine the increase in plasma LTC4 (0.249 +/- 0.036 ng/ml) and LTD4 (1.399 +/- 0.235 ng/ml) of guinea pigs during intravenous challenge-induced anaphylactic bronchoconstriction, and the suppression of the increase of bronchoconstriction and leukotrienes by the administration of 5-lipoxygenase inhibitors such as E6080 (6-hydroxy-2-(4-sulfamoylbenzyl-amino)- 4,5,7-trimethylbenzothiazole hydrochloride), AA861 (2,3,5-trimethyl-6-(12-hydroxy-5,10-dodecadiynyl)-1,4-benzoquinone ) and phenidone. On the other hand, LTC4 and LTD4 were not detected in plasma after an inhaled challenge, though significant bronchoconstriction was provoked. It was concluded that the present study validates a new technique for quantitating plasma leukotrienes on the basis of pH and a suitable method for evaluating the pharmacological efficacy of 5-lipoxygenase inhibitors.  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