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   248404篇
  免费   1908篇
  国内免费   263篇
电工技术   4036篇
综合类   90篇
化学工业   40026篇
金属工艺   15143篇
机械仪表   10062篇
建筑科学   4175篇
矿业工程   3756篇
能源动力   3871篇
轻工业   9698篇
水利工程   4084篇
石油天然气   13006篇
武器工业   28篇
无线电   20179篇
一般工业技术   62743篇
冶金工业   32129篇
原子能技术   11134篇
自动化技术   16415篇
  2021年   2746篇
  2019年   2729篇
  2018年   5428篇
  2017年   5710篇
  2016年   6044篇
  2015年   3051篇
  2014年   5322篇
  2013年   10080篇
  2012年   7303篇
  2011年   8925篇
  2010年   7293篇
  2009年   8103篇
  2008年   8171篇
  2007年   7856篇
  2006年   6356篇
  2005年   5561篇
  2004年   5478篇
  2003年   5299篇
  2002年   5133篇
  2001年   4947篇
  2000年   4937篇
  1999年   4253篇
  1998年   7171篇
  1997年   5831篇
  1996年   4421篇
  1995年   3653篇
  1994年   3422篇
  1993年   3623篇
  1992年   3214篇
  1991年   3359篇
  1990年   3481篇
  1989年   3369篇
  1988年   3267篇
  1987年   3260篇
  1986年   3156篇
  1985年   3314篇
  1984年   3252篇
  1983年   3146篇
  1982年   2993篇
  1981年   3045篇
  1980年   3071篇
  1979年   3258篇
  1978年   3490篇
  1977年   3460篇
  1976年   3911篇
  1975年   3210篇
  1974年   3293篇
  1973年   3341篇
  1972年   2987篇
  1971年   2754篇
排序方式: 共有10000条查询结果,搜索用时 593 毫秒
981.
Results of a laboratory study of the properties of corundum concrete with metallic fibers of five compositions are presented. It is shown that some of the fibers affect favorably the strength and heat resistance of the concrete. Industrial tests of parts made of the suggested reinforced concrete have proved these conclusions.Translated from Ogneupory i Tekhnicheskaya Keramika, No. 11, pp. 22–24, November, 1996.  相似文献   
982.
983.
Buffalo milk Cheddar cheese samples of different ages were analysed for compositional attributes (CA), ripening indices (RI) and Instron Textural Profile (ITP). All samples were compositionally alike, except for pH and salt-in-moisture (SM) contents. RI showed significant variations. CA and RI showed highly significant correlations within themselves and with each other, except for moisture with pH, SM with moisture, MNFS, Fat and FDM and Fat with MNFS. The ITPs of cheeses showed significant variations and had highly significant intercorrelations indicating their interdependence. CA (except moisture and MNFS) and RI showed a highly significant correlationship with ITPs. Moisture content showed a highly significant correlationship with all ITPs, except cohesiveness and springiness, where it was significant. MNFS content showed significant correlations only with hardness and brittleness. Stepwise regression analysis revealed that MI was the most predominant factor influencing cheese texture, followed by pH, SM, FDM and TVFA. Knowing Ca and RI, the textural properties of cheeses can be forecast through mathematical equations. Similarly the age of cheese can also be predicted if RI and/or textural properties are known.  相似文献   
984.
The paper describes the physical and chemical mechanisms governing the tribochemical reduction of metals and non-metals from their oxides. The reduction was started by a tribochemical activation of initial constituents in a vibrating mill used as a reactor. Powders of oxides of copper, iron, molybdenum, tungsten, vanadium, titanium and boron and also such chemically pure metals as magnesium, aluminium and titanium were used as reaction constituents. The triboactivation energy contribution needed to start the explosive mechanism reduction is found to increase as the heat of reaction decreases and the heat of formation of the associated product rises. Introducing oxygen into the reactor during the tribochemical activation of powders of oxides together with magnesium causes the intense oxidation of magnesium and stimulates the reduction process. To increase the yield of tungsten monocarbide from tungsten concentrate, the reduction process should be implemented in an atmosphere of hydrogen or hydrocarbons.  相似文献   
985.
986.
987.
988.
The composition, thickness, thermodynamic activities of components, Gibbs energy and excess energy of formation of the surface layer on binary melts of iron, cobalt and nickel-based alloys with different interatomic interactions were evaluated with the aid of data from the literature and the authors measurements of the concentration dependence of the surface tension and molar volume.  相似文献   
989.
990.
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