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   312050篇
  免费   3715篇
  国内免费   1096篇
电工技术   5689篇
综合类   2519篇
化学工业   45906篇
金属工艺   15830篇
机械仪表   13810篇
建筑科学   8374篇
矿业工程   1911篇
能源动力   6119篇
轻工业   22184篇
水利工程   3277篇
石油天然气   2554篇
武器工业   5篇
无线电   36243篇
一般工业技术   63908篇
冶金工业   36733篇
原子能技术   3863篇
自动化技术   47936篇
  2021年   1131篇
  2019年   1145篇
  2018年   21707篇
  2017年   21385篇
  2016年   14438篇
  2015年   2443篇
  2014年   2627篇
  2013年   8248篇
  2012年   8985篇
  2011年   21290篇
  2010年   18701篇
  2009年   16190篇
  2008年   17268篇
  2007年   20080篇
  2006年   5398篇
  2005年   9456篇
  2004年   7441篇
  2003年   6994篇
  2002年   5575篇
  2001年   4564篇
  2000年   4353篇
  1999年   4152篇
  1998年   7092篇
  1997年   5644篇
  1996年   4928篇
  1995年   4122篇
  1994年   3812篇
  1993年   3558篇
  1992年   3130篇
  1991年   2916篇
  1990年   2937篇
  1989年   2879篇
  1988年   2708篇
  1987年   2458篇
  1986年   2382篇
  1985年   2885篇
  1984年   2692篇
  1983年   2495篇
  1982年   2350篇
  1981年   2215篇
  1980年   2069篇
  1979年   2162篇
  1978年   1995篇
  1977年   2245篇
  1976年   2724篇
  1975年   1759篇
  1974年   1579篇
  1973年   1632篇
  1972年   1321篇
  1971年   1180篇
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
41.
Moderate alcohol consumption is associated with increased plasma high-density lipoprotein (HDL)-cholesterol concentrations and reduced risk for cardiovascular disease. Plasma cholesteryl ester transfer activity (CETA) mediates the exchange of HDL-cholesteryl ester (CE) for the triacylglycerol (TAG) of very-low-density lipoproteins. We compared the effects of oral challenges of Alcohol, saturated fat (SAT), and (Alcohol + SAT) on plasma CETA, cholesterol, nonesterified fatty acids (NEFA), and TAG among normo-triglyceridemic (NTG) and mildly hypertriglyceridemic (HTG) volunteers having a range of plasma TAG concentrations. The major changes were (1) CETA increased more after ingestion of SAT and (Alcohol + SAT) in the HTG group versus the NTG group; (2) after all three challenges, elevation of plasma TAG concentration persisted longer in the HTG versus NTG group. Plasma cholesterol was not affected by the three dietary challenges, while Alcohol increased NEFA more in the HTG group than the NTG group. Plasma TAG best predicted plasma CETA, suggesting that intestinally derived lipoproteins are acceptors of HDL-CE. Unexpectedly, ingestion of (Alcohol + SAT) reduced the strength of the correlation between plasma TAG and CETA, that is the effects of (SAT and Alcohol) on plasma CETA are not synergistic nor additive but rather mutually suppressive. The alcohol-mediated inhibition of CE-transfer to chylomicrons maintains a higher plasma HDL-cholesterol concentration, which is athero-protective, although the suppressive metabolite underlying this correlation could be acetate, the terminal alcohol metabolite, other factors, including CETA inhibitors, are also likely important.  相似文献   
42.
43.
44.
This paper presents an integrated passive damping approach in hybrid metal-CFRP parts for structural applications. In this concept a viscoelastic material is embedded in the joint zone of the hybrid component. To examine the connection strength single-lap-joint specimens were produced and tested and the influence of the used material combinations, different surface structures, and different process parameters i.e. the moment of cross-linking were evaluated. Afterwards, the metal-CFRP hybrids were tested in quasi-static tests to assess their connection strength and failure behaviour. Dynamic cyclic tensile tests with step-wise increased loading conditions were performed to determine the specimens damping behaviour and to estimate their fatigue performance. Finally, these results are compared to a state of the art metal-CFRP hybrid with rivets connecting both materials.  相似文献   
45.
Software and Systems Modeling - Many model transformation scenarios require flexible execution strategies as they should produce models with the highest possible quality. At the same time,...  相似文献   
46.
The data on the use of solar photovoltaic plants (PVPs) for providing a reliable and guaranteed power supply to telecommunication systems and cellular communication systems in the conditions prevalent in Uzbekistan are given. The research-based structures developed by OOO MIR SOLAR and the selection of PVP elements ensuring their reliable operation are described. The main influencing factors are discussed, and the use of effective combinations of different types of panels (from monocrystalline and polycrystalline silicon) and a specially developed controller are considered.  相似文献   
47.
This work presents simulation of microstructure evolution in the nugget zone (NZ) of a AZ31-Mg-alloy friction stir weld. The process parameters (tool geometrical characteristics, rotational speed, travel speed, applied load) have been correlated with the resulting microstructural features in the NZ of the weld (grain size and population) with the aid of the MICRESS software, which provides the ability to simulate both nucleation and grain growth during dynamic recrystallization phenomena evolving in the NZ during the weld thermal cycle. The input parameters of the developed model include the tool geometry, the welding conditions as well as the recrystallization energy, the grain boundary mobility and specific material properties. NZ microstructure obtained by simulation shows good agreement with experimental measurements for both grain population and size.  相似文献   
48.
49.
50.
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