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   1941篇
  免费   1篇
化学工业   29篇
机械仪表   9篇
建筑科学   17篇
能源动力   1篇
轻工业   16篇
水利工程   2篇
石油天然气   17篇
无线电   13篇
一般工业技术   16篇
冶金工业   1782篇
原子能技术   5篇
自动化技术   35篇
  2022年   2篇
  2021年   3篇
  2020年   3篇
  2019年   1篇
  2018年   2篇
  2017年   1篇
  2015年   2篇
  2014年   9篇
  2013年   14篇
  2012年   5篇
  2011年   11篇
  2010年   10篇
  2009年   8篇
  2008年   6篇
  2007年   6篇
  2006年   10篇
  2005年   9篇
  2004年   4篇
  2003年   19篇
  2002年   7篇
  2001年   5篇
  2000年   3篇
  1999年   56篇
  1998年   526篇
  1997年   293篇
  1996年   231篇
  1995年   113篇
  1994年   101篇
  1993年   106篇
  1992年   15篇
  1991年   31篇
  1990年   35篇
  1989年   24篇
  1988年   40篇
  1987年   25篇
  1986年   24篇
  1985年   19篇
  1984年   1篇
  1983年   6篇
  1982年   10篇
  1981年   12篇
  1980年   16篇
  1979年   1篇
  1978年   4篇
  1977年   37篇
  1976年   73篇
  1975年   1篇
  1972年   1篇
  1966年   1篇
排序方式: 共有1942条查询结果,搜索用时 0 毫秒
101.
上网本 我办公室有办公用笔记本电脑,家里有台式PC,而华硕Eee PC 1000HE算是我的随身电脑。  相似文献   
102.
Three methods approved by the National Committee for Clinical Laboratory Standards for testing the susceptibility of anaerobic bacteria were used to evaluate the fluoroquinolone, trovafloxacin. The methods gave essentially comparable results with 126 anaerobes and with three quality control strains. A collaborative study defined the quality control range for trovafloxacin MICs. Trovafloxacin had good in vitro activity against the more common anaerobes (MIC 90 < = or 2.0 micrograms/ml).  相似文献   
103.
104.
105.
We analyzed signal-averaged electrocardiograms (ECG) obtained in 50 patients with recent myocardial infarction (RMI: 25 anterior and 25 inferior) and 20 normal subjects to determine the relationship between the initial portion of the signal-averaged QRS complex and cardiac function and infarct size. We examined (1) the root mean square voltage (RMS10-40, microV), (2) the integration (A10-40, microV.msec) at 10-msec intervals over the first 40 msec of the signal-averaged QRS complex, and (3) the intervals (T) of the magnitude of the signal-averaged ECG achieved at 10-microV intervals over the first 40 microV (T10-40, msec). The mean RMS10-40 (p < 0.01) and A10-40 (A10, p < 0.05; A20-40, p < 0.01) were significantly lower and the T10-40 (p < 0.01) was significantly longer in RMI patients than in normal subjects. The RMS10-40 (p < 0.01) and A10-40 (p < 0.05) were significantly lower and the T10-40 (T10.20, p < 0.01; T30.40, p < 0.05) was significantly longer in patients with anterior RMI patients than in patients with inferior RMI. The A30 was correlated with the ejection fraction and total creatine kinase (CK) release in all patients (r = 0.73, and -0.78, respectively, p < 0.001). These results suggest that the A30 may be an important predictor of ventricular dysfunction and infarct size in patients with RMI.  相似文献   
106.
107.
在市场经济条件下,国营企业要生存发展,必须大力开拓市场营销渠道,生产适销对路的产品,满足用户需要。文章介绍了天津第一预应力钢丝有限公司,充分发挥自身实力,“保重点、占大户”,打国家重点工程项目,创名牌产品,树立企业形象,提高企业在市场竞争中的参与能力的做法与经验。  相似文献   
108.
PURPOSE: The aim of this study was to determine the concentration of interleukin-1 alpha in human embryo culture medium with or without oviductal cell coculture and to correlate the interleukin-1 alpha levels with pregnancy. METHODS: Culture media from 32 in vitro fertilization and embryo transfer cycles were assayed for interleukin-1 alpha by immunoassay technique. Human embryos were cultured in Earles' balanced salt solution supplemented with 15% preovulatory serum (sEBSS) in 16 of these cycles, while embryos in the rest of the cycles were cocultured with human oviductal cells in sEBSS. RESULTS: Both sEBSS and spent sEBSS after embryo culture contained low or undetectable levels of interleukin-1 alpha in the pregnant and nonpregnant cycles. On the other hand, oviductal cells significantly increased the amount of interleukin-1 alpha immunoreactivity in the conventional culture medium or coculture medium (P < 0.001, Mann-Whitney rank sum test). The concentrations of interleukin-1 alpha in the spent sEBSS after oviductal cell culture and after coculture with human embryos were 1.5 +/- 1.0 and 1.3 +/- 0.9 pg/ml, respectively. There was no difference in the interleukin-1 alpha concentration between the pregnant and the nonpregnant coculture cycles. CONCLUSIONS: These data showed that human oviductal cells produced interleukin-1 alpha immunoreactivity in a coculture system. However, this production could not be used as a marker for successful embryo implantation.  相似文献   
109.
110.
For cardiovascular biomaterials, thrombosis, thromboembolism and vascular graft occlusion are believed to be precipitated by the adsorption of proteins containing adhesive ligands for platelets. Polyethylene-glycol-diisocyanate (PEG-diisocyanate, 3400 MW) may potentially react with protein amines to form molecular barriers on adsorbed proteins on biomaterials, thereby masking adhesive ligands and preventing acute surface thrombosis. To test this notion, PE, PTFE, and glass microconduits were pre-adsorbed with fibrinogen and treated with PEG-diisocyanate, non-reactive PEG-dihydroxyl, or remained untreated. Following perfusion of 111In-labeled platelets in whole human blood for 1 min (wall shear rate = 312 s(-1)), PEG-diisocyanate treated surfaces experienced 96% (PE), 97% (PTFE) and 94% (glass) less platelet deposition than untreated surfaces. Similar reductions were seen for PEG-diisocyanate versus PEG-dihydroxyl treatment. Low shear perfusions of plasma for 1 h prior to blood contact did not reduce the inhibitory effect of PEG-diisocyanate. Platelet adhesion onto collagen-coated glass coverslips and platelet deposition onto preclotted Dacron were also reduced by treatment with PEG-diisocyanate (93 and 91%, respectively). Protein-reactive PEG may thus have utility in forming molecular barriers on surface-associated proteins to inhibit acute thrombosis on cardiovascular biomaterials.  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