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   291747篇
  免费   21842篇
  国内免费   11228篇
电工技术   15644篇
技术理论   31篇
综合类   17576篇
化学工业   50476篇
金属工艺   17036篇
机械仪表   18613篇
建筑科学   23023篇
矿业工程   9599篇
能源动力   8016篇
轻工业   16860篇
水利工程   4889篇
石油天然气   20486篇
武器工业   2262篇
无线电   31699篇
一般工业技术   34603篇
冶金工业   15347篇
原子能技术   2886篇
自动化技术   35771篇
  2024年   1241篇
  2023年   4733篇
  2022年   8047篇
  2021年   11664篇
  2020年   8646篇
  2019年   7348篇
  2018年   8250篇
  2017年   9339篇
  2016年   8120篇
  2015年   11300篇
  2014年   13899篇
  2013年   16579篇
  2012年   17905篇
  2011年   19566篇
  2010年   16894篇
  2009年   16038篇
  2008年   15541篇
  2007年   15209篇
  2006年   16077篇
  2005年   14243篇
  2004年   9113篇
  2003年   7963篇
  2002年   7343篇
  2001年   6512篇
  2000年   7134篇
  1999年   8542篇
  1998年   6876篇
  1997年   5849篇
  1996年   5470篇
  1995年   4528篇
  1994年   3779篇
  1993年   2639篇
  1992年   2149篇
  1991年   1603篇
  1990年   1180篇
  1989年   937篇
  1988年   761篇
  1987年   524篇
  1986年   390篇
  1985年   265篇
  1984年   183篇
  1983年   120篇
  1982年   131篇
  1981年   86篇
  1980年   72篇
  1979年   24篇
  1978年   2篇
  1965年   2篇
  1959年   1篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
This paper presents recent efforts on the preparation of flexible polyhedral particles via concentrated emulsion templating polymerization in which the hydrophilic monomer (acrylamide) and hydrophobic monomer (butyl acrylate) are polymerized simultaneously in the continuous and dispersed phase, respectively. Such templating polymerization has been enhanced in our systems owing to the introduction of acrylamide monomer and their higher polymerization rate in continuous phase as compared with butyl acrylate in dispersed phase. Diffusion between the different phases was also inhibited. Furthermore, the stability of the concentrated emulsion and the molecular weight of the produced poly(butyl acrylate) were found to be significantly affected by the amount of redox initiator. The morphology of the particles could be controlled by varying the volume fraction of the dispersed phase and the polyhedral particles were achieved at higher volume fraction. Copyright © 2005 Society of Chemical Industry  相似文献   
112.
in-situ transmission electron microscopy (TEM) tensile tests on as-cast and aged 63Sn37Pb solder alloys were conducted, and the fracture behavior in nanometer scale ahead of the crack tip was inspected and discussed. Results show that the fracture was completed by connecting the discontinuous cracks or voids. Dislocation behavior was concentrated along the grain boundaries for as-cast samples, and displayed mainly as dislocation climb. The crack was intergranular dominated under the lower strain rate. While remarkable mutual dislocation emission was detected in the aged solder. Transgranular cracks were dominant in the fractured area, and they propagated by linking up with the nanometer scale cracks ahead of the crack tips under the effective promotion of the inverse dislocation emission. At the same time, the partial interphase or intergranular cracks in the thinned area were also found. Under this condition, a new critical stress intensity factor K c to define the mutual dislocation emission was proposed.  相似文献   
113.
Melt of NaCO3 can favor oxidation of Zr to form ZrO2 thin film on Zr surface, which is used to make Zr/ZrO2 oxidation/reduction electrode of pH sensor for testing elevated temperature aqueous solutions. Using SEM, EPMA, XPS, EXAFS and HRTEM, we found that ZrO2 film is tightness and solid with 20 μm thickness composed by nanometer-sized monoclinic crystals. Zr/ZrO2 interface is characterized of zoning structure according to topography and chemical composition in five zones: oxygen-rich ZrO2, ZrO2, oxygen-rich Zr metal, oxygen-bearing Zr and Zr from outmost to center. Melt oxidation process of Zr involved oxidation time, air and temperature. The air is important effect on structural and electrochemical properties of ZrO2 thin film for making elevate temperature electrochemical sensor. If oxygen air largely presented in carbonate melting process, ZrO2 thin film is not tightness and not for oxidation/reduction electrode.  相似文献   
114.
115.
116.
117.
118.
119.
120.
Polyurethane elastomer composites were developed using milled fiberglass and their mechanical properties were studied. In particular, the organically chemical treatment of the milled fiberglass was investigated in detail. It was demonstrated that both strength and toughness of the resulting elastomer composites were improved considerably with the addition content of fiberglass. Furthermore, it was indicated that the optimal properties can be achieved by the proper addition of milled fiberglass that was chemically treated using coupling agent.  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