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   5068篇
  免费   405篇
  国内免费   2篇
电工技术   37篇
综合类   3篇
化学工业   905篇
金属工艺   52篇
机械仪表   69篇
建筑科学   160篇
矿业工程   8篇
能源动力   112篇
轻工业   1141篇
水利工程   76篇
石油天然气   23篇
无线电   208篇
一般工业技术   715篇
冶金工业   1229篇
原子能技术   12篇
自动化技术   725篇
  2024年   9篇
  2023年   50篇
  2022年   42篇
  2021年   107篇
  2020年   106篇
  2019年   122篇
  2018年   195篇
  2017年   195篇
  2016年   186篇
  2015年   162篇
  2014年   210篇
  2013年   407篇
  2012年   334篇
  2011年   316篇
  2010年   252篇
  2009年   223篇
  2008年   234篇
  2007年   225篇
  2006年   158篇
  2005年   111篇
  2004年   100篇
  2003年   99篇
  2002年   82篇
  2001年   78篇
  2000年   50篇
  1999年   66篇
  1998年   501篇
  1997年   269篇
  1996年   178篇
  1995年   92篇
  1994年   70篇
  1993年   70篇
  1992年   20篇
  1991年   12篇
  1990年   9篇
  1989年   12篇
  1988年   12篇
  1987年   16篇
  1986年   11篇
  1985年   12篇
  1984年   7篇
  1983年   5篇
  1981年   9篇
  1980年   7篇
  1979年   2篇
  1978年   5篇
  1977年   8篇
  1976年   18篇
  1975年   3篇
  1973年   5篇
排序方式: 共有5475条查询结果,搜索用时 234 毫秒
41.
BACKGROUND AND STUDY AIMS: Anastomotic leakage is a severe complication in gastric surgery and it is associated with a high rate of mortality. Conservative treatment sometimes is not sufficient to stem the leakages and, even when it is sufficient, it takes a long time. The present study describes the first experience in the treatment of anastomotic leakages with endoscopic clipping. PATIENTS AND METHODS: From May 1995 to December 1996, seven patients with postoperative anastomotic leakages after gastric surgery were prospectively treated in our Endoscopy Service. Metallic endoclips (MD 850, Olympus Corp., Tokyo, Japan) with prongs 12 mm long and 6 mm wide were applied, controlling the closure of the leakage by endoscopy, using radiographs to confirm the closure 24 hours later. RESULTS: Complete closure of the leakage was obtained in all seven cases. A single session of endoscopic clipping was needed for five patients while two other required, respectively, two and three sessions. The median time of leakage closure after endoscopic clipping was 2.3 days (range 1-5 days). The clips spontaneously dislodged within 1 month in five patients and within the second month in the other two patients. CONCLUSION: Endoscopic treatment of anastomotic leakages by metallic clips represents a safe and easily repeated method and, compared to conservative treatment, it seems to offer several time and cost advantages. Further studies involving a larger number of patients are needed to verify this finding.  相似文献   
42.
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   
43.
44.
45.
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   
46.
We report a case of acute bilateral striatal necrosis in an infant. CT and MRI findings are described.  相似文献   
47.
48.
49.
50.
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