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   5993篇
  免费   481篇
  国内免费   4篇
电工技术   49篇
综合类   3篇
化学工业   1260篇
金属工艺   59篇
机械仪表   93篇
建筑科学   188篇
矿业工程   6篇
能源动力   113篇
轻工业   1336篇
水利工程   77篇
石油天然气   35篇
无线电   244篇
一般工业技术   844篇
冶金工业   1316篇
原子能技术   19篇
自动化技术   836篇
  2024年   9篇
  2023年   62篇
  2022年   105篇
  2021年   205篇
  2020年   145篇
  2019年   153篇
  2018年   238篇
  2017年   227篇
  2016年   229篇
  2015年   185篇
  2014年   258篇
  2013年   469篇
  2012年   396篇
  2011年   369篇
  2010年   292篇
  2009年   247篇
  2008年   267篇
  2007年   262篇
  2006年   186篇
  2005年   134篇
  2004年   118篇
  2003年   128篇
  2002年   100篇
  2001年   93篇
  2000年   52篇
  1999年   69篇
  1998年   504篇
  1997年   276篇
  1996年   187篇
  1995年   100篇
  1994年   80篇
  1993年   82篇
  1992年   23篇
  1991年   17篇
  1990年   11篇
  1989年   23篇
  1988年   13篇
  1987年   23篇
  1986年   16篇
  1985年   20篇
  1984年   12篇
  1983年   9篇
  1982年   4篇
  1981年   10篇
  1980年   13篇
  1979年   4篇
  1978年   7篇
  1977年   8篇
  1976年   18篇
  1975年   8篇
排序方式: 共有6478条查询结果,搜索用时 15 毫秒
51.
OBJECTIVE: The objective of this study was to determine fibronectin levels in umbilical cord blood of infants of diabetic mothers (IDM) and evaluate a possible correlation with perinatal pathology. PATIENTS AND METHODS: A prospective study of 58 IDM (33 males and 25 females) and 58 control newborns (NB) (33 males and 25 females) was carried out. RESULTS: There were no differences in fibronectin levels between the two groups nor between the sexes. Perinatal morbidity was higher in the IDM group, but there was no correlation between fibronectin levels and the presence of perinatal pathology. CONCLUSIONS: Fibronectin levels are not useful in the perinatal evaluation of infants of diabetic mothers.  相似文献   
52.
53.
54.
55.
The aim of this study was to determine whether bisaramil-an antiarrhythmic compound under clinical investigation-influences the reperfusion-induced arrhythmias and biochemical parameters characterizing occlusion-reperfusion-induced free-radical reactions. The left descending coronary artery (LAD) was occluded for 60 min in anaesthetized dogs followed by one hour of reperfusion. Blood samples were taken at different times of the occlusion and reperfusion for the determination of plasma concentration of malondialdehyde (MDA), reduced (GSH) and oxidized glutathione (GSSG); furthermore of the activity of catalase and superoxide dismutase (SOD). Free-radical generating capacity of polymorph neutrophil granulocytes (PMN) was also measured. At the end of the experiments heart tissue samples were excised from the injured areas and from the intact part of the left ventricular muscle. In tissues samples the concentrations of MDA and GSH and the activity of SOD were determined. Bisaramil was given as an i.v. bolus injection at a dose of 2 mg kg-1 several minutes prior to the end of LAD-occlusion; then the administration was repeated in the 30th minute of reperfusion. In the control group (10 dogs) ventricular fibrillation (VF) occurred in seven cases which resulted in death in three. In the bisaramil-treated group, however. VF was seen in three cases and no death was recorded. Bisaramil inhibited the elevation of the plasma concentration of MDA and GSSG during the reperfusion and abolished the decrease in the plasma concentration of GSH during the occlusion and reperfusion. The activity of SOD and catalase in plasma was much better preserved in the bisaramil-treated group then in the controls. Bisaramil significantly inhibited the increase of the superoxide-radical generating capacity of PMNs during the reperfusion. The data obtained from myocardial tissue samples supported the cardioprotective effect of bisaramil. The biochemical investigation of ischemic-reperfused myocardium showed that bisaramil promoted preservation of SOD-activity and of tissue glutathione. Results of this study clearly showed that bisaramil has a significant effect on ischemiareperfusion injury. Besides its inhibitory effects on ischaemia-reperfusion induced arrhythmias it has a special benefit in influencing free-radical mediated damage leading to better preservation of membranes and to limitations of irreversible cell injuries.  相似文献   
56.
We report a case of acute bilateral striatal necrosis in an infant. CT and MRI findings are described.  相似文献   
57.
58.
59.
60.
A prospective study was conducted on 374 patients with urinary lithiasis, aiming to analyze the participation of oxalate in the lithogenesis and composition of the calcium oxalate calculi, alone or associated to other factors. METHODOLOGY: Metabolic urinary study of the patient and analysis of calculi with infrared spectrography and optical microscopy. RESULTS: 26.3% patients had hyperoxaluria and 77.5% of the calculi contain calcium oxalate; these are 167 cases of calcium oxalate, 110 of oxalate and calcium phosphate and 13 cases of mixed calcium oxalate and uric acid lithiasis. 43.4% patients with pure monohydrate calcium oxalate calculi have hypercalciuria, 22.6% hyperoxaluria and 19% hyperuricosuria. Dihydrated calcium oxalate calculi are related to high hypercalciuria in 65% cases and to significant hyperoxaluria in 35% cases. 45% patients present a single lithogenic factor, either hypercalciuria (49.6%), hyperoxaluria (20.6%), hyperuricosuria (13.74%), hypocitraturia (9%), urinary infection (1.5%), A.T.R. (2.25%) or acid oliguria (3%).  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