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   3510篇
  免费   20篇
  国内免费   1篇
电工技术   15篇
综合类   2篇
化学工业   168篇
金属工艺   34篇
机械仪表   25篇
建筑科学   28篇
能源动力   16篇
轻工业   135篇
水利工程   31篇
石油天然气   3篇
无线电   90篇
一般工业技术   142篇
冶金工业   2686篇
原子能技术   21篇
自动化技术   135篇
  2021年   12篇
  2019年   8篇
  2018年   19篇
  2017年   10篇
  2016年   21篇
  2015年   7篇
  2014年   35篇
  2013年   61篇
  2012年   36篇
  2011年   41篇
  2010年   31篇
  2009年   26篇
  2008年   33篇
  2007年   45篇
  2006年   43篇
  2005年   35篇
  2004年   38篇
  2003年   30篇
  2002年   36篇
  2001年   27篇
  2000年   29篇
  1999年   109篇
  1998年   828篇
  1997年   494篇
  1996年   304篇
  1995年   172篇
  1994年   146篇
  1993年   171篇
  1992年   24篇
  1991年   37篇
  1990年   45篇
  1989年   42篇
  1988年   46篇
  1987年   40篇
  1986年   29篇
  1985年   41篇
  1984年   8篇
  1983年   15篇
  1982年   21篇
  1981年   20篇
  1980年   27篇
  1979年   11篇
  1978年   14篇
  1977年   51篇
  1976年   108篇
  1975年   21篇
  1974年   13篇
  1973年   7篇
  1972年   8篇
  1970年   8篇
排序方式: 共有3531条查询结果,搜索用时 20 毫秒
1.
2.
The transjugular intrahepatic portosystemic shunt procedure is an accepted treatment for adults with complications of portal hypertension. We performed a retrospective review of all pediatric TIPS placements performed at the University of California, San Francisco between 1990 and 1996. Twelve procedures were attempted in nine children, with a mean age (+/- SD) of 9.4 +/- 3.9 years (range, 5 to 15 years) and a mean weight of 31 +/- 18 kg (range, 16 to 70 kg). The indications for TIPS placement were portal hypertension complicated by chronic variceal hemorrhage not controlled with sclerotherapy (n = 7) and hypersplenism with thrombocytopenia (n = 2). TIPS placement was successfully completed initially in seven of nine (78%) patients. Unfavorable vascular anatomy was the cause of failure in two cases. The seven patients who underwent successful TIPS placement were followed up for an average of 136 days (range, 1 to 800 days); two still have patent shunts, three underwent liver transplantation, one had a splenorenal shunt after stenosis, and one died of underlying liver disease. Variceal bleeding was controlled in four of five patients who successfully underwent TIPS placement. Shunt occlusion occurred in four patients; patency was restored by transjugular shunt revision in three, and a splenorenal shunt was performed in one.  相似文献   
3.
Gastric bacteria from cheetahs with gastritis were used to inoculate specific-pathogen free kittens and conventional mice. Helicobacter sp. and Gastrospirillum sp. colonized kittens, while only Gastrospirillum sp. colonized mice. In kittens, both bacterial species induced mild lymphofolliclar gastritis which did not change over the course of the 11 months observation period. In mice, Gastrospirillum sp. induced lymphoplasmacytic and follicular gastritis which increased in severity over 6 months and persisted for the 12 month observation period. Gastric ulcers and gastric mucosal hypertrophy were present in chronically infected mice. These results indicate that host but not bacterial factors influence the severity of gastritis, and that in mice, bacterial gastritis increases in severity with time and may lead to gastric ulceration in some individuals.  相似文献   
4.
5.
Comments on the argument of L. T. Hoshmand and D. E. Polkinghorn (see record 1992-21300-001) that psychological practice should inform science to the same degree that science informs practice. Based on a survey of 121 faculty members in programs accredited by the American Psychological Association, 65% reported practice activity. The authors agree that the problem involves a much more complex integrative task that goes beyond simply recognizing knowledge gained in practice settings as valid. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
6.
7.
8.
9.
The fabrication using silicon micromachining and characterization of an acoustic Lamb wave actuator is presented. The intended use of the device is for mass transport and sensor applications. The device consists of dual interdigitated transducers patterned on a thin-film composite membrane of silicon nitride, platinum, and a sol-gel-derived piezoelectric ceramic (PZT) thin film. The acoustic properties of the device are presented along with preliminary applications to mechanical transport and liquid delivery systems. Improved acoustic signals and improved mass transport are achieved with PZT over present Lamb wave devices utilizing ZnO or AlN as the piezoelectric transducer  相似文献   
10.
We investigated the effect of chlorpromazine (CPZ) in a murine model of T-cell-dependent liver injury caused by concanavalin A (ConA). CPZ (3 and 10 mg/kg) treatment 1 h before ConA injection prevented liver injury. CPZ (3, 10 mg/kg) administered 1 h after a ConA injection was also hepatoprotective, whereas cyclosporin (CsA, 100 mg/kg) was active only when given before ConA. Under either condition, CsA but not CPZ prevented concurrent increases in splenic ornithine decarboxylase (ODC) activity, a putative index of T-cell proliferation/differentiation. CPZ down-regulated tumor necrosis factor-alpha (TNF-alpha) and up-regulated IL-10 in mice that then received ConA, whereas delayed administration of CPZ had no effect. These results suggest that CPZ prevented liver injury without affecting the proliferation/differentiation of T-cells. The dissociation of hepatoprotection by CPZ from cytokine modulation indicates that this drug intervenes in the adherence of T-cells or the death of hepatocytes in the ConA-model.  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