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   2913篇
  免费   17篇
  国内免费   4篇
电工技术   6篇
综合类   3篇
化学工业   139篇
金属工艺   25篇
机械仪表   10篇
建筑科学   20篇
矿业工程   2篇
能源动力   26篇
轻工业   44篇
水利工程   4篇
石油天然气   3篇
无线电   114篇
一般工业技术   149篇
冶金工业   2296篇
原子能技术   25篇
自动化技术   68篇
  2023年   3篇
  2022年   18篇
  2021年   16篇
  2020年   16篇
  2019年   18篇
  2018年   16篇
  2017年   26篇
  2016年   22篇
  2015年   10篇
  2014年   30篇
  2013年   60篇
  2012年   31篇
  2011年   28篇
  2010年   34篇
  2009年   35篇
  2008年   28篇
  2007年   29篇
  2006年   25篇
  2005年   14篇
  2004年   14篇
  2003年   16篇
  2002年   8篇
  2001年   8篇
  2000年   6篇
  1999年   83篇
  1998年   760篇
  1997年   429篇
  1996年   254篇
  1995年   152篇
  1994年   128篇
  1993年   149篇
  1992年   26篇
  1991年   32篇
  1990年   40篇
  1989年   35篇
  1988年   41篇
  1987年   35篇
  1986年   21篇
  1985年   29篇
  1984年   3篇
  1983年   4篇
  1982年   11篇
  1981年   11篇
  1980年   20篇
  1979年   3篇
  1978年   7篇
  1977年   47篇
  1976年   94篇
  1975年   3篇
  1955年   2篇
排序方式: 共有2934条查询结果,搜索用时 15 毫秒
1.
2.
3.
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   
4.
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   
5.
6.
7.
8.
9.
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   
10.
The epilepsies are a group of disorders characterised by recurrent seizures caused by episodes of abnormal neuronal hyperexcitability involving the brain. Up to 60 million people are affected worldwide and genetic factors may contribute to the aetiology in up to 40% of patients. The most common human genetic epilepsies display a complex pattern of inheritance. These are categorised as idiopathic in the absence of detectable structural or metabolic abnormalities. Juvenile myoclonic epilepsy (JME) is a distinctive and common variety of familial idiopathic generalised epilepsy (IGE) with a prevalence of 0.5-1.0 per 1000 and a ratio of sibling risk to population prevalence (lambda(s)) of 42. The molecular genetic basis of these familial idiopathic epilepsies is entirely unknown, but a mutation in the gene CHRNA4, encoding the alpha4 subunit of the neuronal nicotinic acetylcholine receptor (nAChR), was recently identified in a rare Mendelian variety of idiopathic epilepsy. Chromosomal regions harbouring genes for nAChR subunits were therefore tested for linkage to the JME trait in 34 pedigrees. Significant evidence for linkage with heterogeneity was found to polymorphic loci encompassing the region in which the gene encoding the alpha7 subunit of nAChR (CHRNA7) maps on chromosome 15q14 (HLOD = 4.4 at alpha = 0.65; Z(all) = 2.94, P = 0.0005). This major locus contributes to genetic susceptibility to JME in a majority of the families studied.  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