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   1796篇
  免费   267篇
  国内免费   26篇
耳鼻咽喉   16篇
儿科学   46篇
妇产科学   35篇
基础医学   287篇
口腔科学   60篇
临床医学   199篇
内科学   369篇
皮肤病学   34篇
神经病学   277篇
特种医学   93篇
外科学   130篇
综合类   105篇
预防医学   170篇
眼科学   39篇
药学   122篇
中国医学   1篇
肿瘤学   106篇
  2022年   21篇
  2021年   24篇
  2020年   23篇
  2019年   30篇
  2018年   48篇
  2017年   23篇
  2016年   30篇
  2015年   31篇
  2014年   29篇
  2013年   56篇
  2012年   84篇
  2011年   71篇
  2010年   47篇
  2009年   41篇
  2008年   60篇
  2007年   79篇
  2006年   84篇
  2005年   86篇
  2004年   67篇
  2003年   67篇
  2002年   65篇
  2001年   45篇
  2000年   60篇
  1999年   40篇
  1998年   38篇
  1997年   32篇
  1996年   27篇
  1995年   21篇
  1994年   27篇
  1993年   20篇
  1992年   42篇
  1991年   44篇
  1990年   32篇
  1989年   54篇
  1988年   61篇
  1987年   48篇
  1986年   38篇
  1985年   32篇
  1984年   32篇
  1983年   41篇
  1982年   21篇
  1981年   16篇
  1980年   17篇
  1979年   28篇
  1978年   23篇
  1976年   16篇
  1972年   14篇
  1971年   19篇
  1970年   17篇
  1969年   17篇
排序方式: 共有2089条查询结果,搜索用时 15 毫秒
1.
2.
3.
周向东  周维善  王钟麒   《药学学报》1997,32(6):416-419
报道新化合物A-失碳-17β-羟基-17α-乙炔基-Δ3(5),9(10)-雌甾二烯-2-酮2的合成。文中探讨了用炔钾粗品对A-失碳-Δ3(5),9(10)-雌甾二烯-2,17-二酮1和A-失碳-6β,19-环氧-Δ3-雄甾-2,17-二酮3的选择性炔化,分别得标题化合物2(44%)及A-失碳-17β-羟基-17α-乙炔基-6β,19-环氧-Δ3雄甾-2-酮4(65%),4经还原性破开环氧、去羟甲基和去醋酰氧基合成了标题化合物2。四步总收率为34%。  相似文献   
4.
1. This laboratory has previously reported that pretreatment with ganglioside, or even with its constituent, sialic acid (SA), can attenuate certain intoxicating effects of ethanol. It was important to see if these findings could be replicated, particularly by using other measures of ethanol effects. Herein we report that pretreatment with either gangliosides or SA attenuated ethanol-induced decrements in locomotion, nose-poke exploration, and anxiety, but not body temperature. 2. An ethanol dose of 4 gm/kg caused a temperature drop of about 3 degrees C, which was unaffected by any pretreatment. The onset to sleep, however, was delayed an average of 18 or 36 secs in mice pretreated with ganglioside or SA, respectively. Ethanol-only (4 gm/kg) depressed mean cumulative locomotor activity to 31% of normal, whereas the depression was 83% of normal with beef brain ganglioside pretreatment. At 2 gm/kg ethanol alone decreased nose poking in a hole-board test to 29% of normal, but the depression was only 55-63% of normal with SA or ganglioside pretreatment. In a staircase climbing anxiety test, this dose of ethanol had no effect by itself, but both ganglioside and SA pre-treatment increased climbing by 22%. Ethanol did depress rearing to only 11% of normal, whereas rearing was 51 and 99% of normal with SA and ganglioside pretreatment, respectively. In a dark-preference test, ethanol-only caused mice to spend 64% of the time in the light, compared to 31% for controls. Time in the light was only 39 and 46% with ganglioside and SA pretreatment, respectively. 3. Blood levels of ethanol were not significantly affected by pretreatment. 4. When given alone, gangliosides significantly stimulated locomotion and staircase climbing. SA significantly decreased rearing in the staircase test. Both gangliosides and SA tended to increase nose poking, number of crossings in the dark-preference test, and time in a lighted compartment. Thus, it is possible that some of the attenuation of intoxication is attributable to non-specific stimulant properties of gangliosides and SA.  相似文献   
5.
Hare  WS 《Radiology》1986,160(1):189-192
Two modified helical basket extractors are described that have increased the success rate of removing ureteral calculi using fluoroscopy from 63% to 92%. Initially a rather stiff and expandable basket with a 20-cm filiform tip is used with coaxial catheters and sheath (stage 1). If this procedure is unsuccessful, a basket with two long cable ends is passed from the nephrostomy out through the urethra (stage 2). When used with coaxial bladder catheters, this technique allows dilatation of the vesicoureteric junction and retrograde catheterization and injection of fluids or gas to dislodge the stone prior to extraction. In a series of 38 patients, stones were removed in all but three (a success rate of 92%). In five cases small stones (less than 5 mm) were not retrieved but subsequent studies were normal. Ureteral stones were found in the abdominal ureter in 28 cases, in the pelvic ureter in seven cases, and in multiple sites in three cases. Stones were larger than 1 cm in 27.7% of cases. Postextraction mucosal edema with reduced ureteral patency was common but usually cleared in 2-3 days. Occasional complications were related to the nephrostomy.  相似文献   
6.
7.
8.
9.
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