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   355553篇
  免费   4219篇
  国内免费   1217篇
电工技术   6398篇
综合类   243篇
化学工业   53880篇
金属工艺   14859篇
机械仪表   10506篇
建筑科学   8821篇
矿业工程   2063篇
能源动力   9297篇
轻工业   31372篇
水利工程   3756篇
石油天然气   6656篇
武器工业   10篇
无线电   40346篇
一般工业技术   69003篇
冶金工业   66758篇
原子能技术   8533篇
自动化技术   28488篇
  2021年   2754篇
  2019年   2628篇
  2018年   4384篇
  2017年   4444篇
  2016年   4721篇
  2015年   3199篇
  2014年   5450篇
  2013年   15829篇
  2012年   8992篇
  2011年   12544篇
  2010年   9975篇
  2009年   11536篇
  2008年   11594篇
  2007年   11626篇
  2006年   9946篇
  2005年   9277篇
  2004年   8902篇
  2003年   8494篇
  2002年   8157篇
  2001年   8262篇
  2000年   8024篇
  1999年   8308篇
  1998年   20445篇
  1997年   14635篇
  1996年   11360篇
  1995年   8461篇
  1994年   7479篇
  1993年   7250篇
  1992年   5498篇
  1991年   5334篇
  1990年   5028篇
  1989年   5123篇
  1988年   4934篇
  1987年   4281篇
  1986年   4126篇
  1985年   4860篇
  1984年   4458篇
  1983年   4156篇
  1982年   3776篇
  1981年   3924篇
  1980年   3651篇
  1979年   3692篇
  1978年   3684篇
  1977年   4216篇
  1976年   5617篇
  1975年   3215篇
  1974年   3125篇
  1973年   3188篇
  1972年   2648篇
  1971年   2469篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Functional Properties and Food Applications of Rapeseed Protein Concentrate   总被引:1,自引:0,他引:1  
Rapeseed protein concentrate (RC), prepared with 2% hexameta-phosphate, was tested for its functionality and performance in some foods. The RC had good nitrogen solubility, fat absorption, emulsification, and whipping capacities but poor water absorption and gelling properties. It increased the emulsion stability, and protein but lowered the fat content of wieners. It also increased the cooking yield, reduced the shrinkage and tenderized meat patties. Results were similar to soybean isolate except for the poorer color and flavor. The cooking yield of RC supplemented wieners was less than the all-meat control and soybean-supplemented wieners. A 9% RC dispersion mixed with an equal volume of eggwhite produced a meringue of comparable stability and texture to that of eggwhite alone.  相似文献   
62.
Translated from Atomnaya Énergiya, Vol. 67, No. 3, pp. 215–216, September, 1989.  相似文献   
63.
No generally accepted principles and guidelines currently exist to help engineers design local interaction mechanisms that result in a desired global behavior. However, several communities have developed ways of approaching this problem in the context of niched application areas. Because the ideas underlying these approaches are often obscured or underemphasized in technical papers, the authors review the role of self-organization in their work. They provide a better picture of the status of the emerging field of self-organizing systems or autonomic computing.  相似文献   
64.
65.
Elasticity is discussed as an aspect of viscoelasticity, which is described by the tube model. The effects of both crosslinks and entanglements contribute to this model and a discussion of how these effects can be quantified is given. At high enough concentration, entanglements ensure the existence of elastic effects even without crosslinks, and a theory is presented on how this dynamical phase change comes about.  相似文献   
66.
An investigation into the effects of pressure (helium gas) on the isothermal fluid behavior includes: (1) the effect of pressure on the rate of melting and coking as evidenced by the rate constants k(melt) and k(coke); (2) the effect of pressure on the energies of activation of melting and coking; (3) the effects of pressure on the characteristic times; (4) the effects of pressure on the maximum isothermal fluidity. Results from the effects of pressure on k(melt) revealed that it was generally the high total sulfur, low nitrogen, low reactives/mineral matter ratio, medium rank coals which show the greatest increase in k(melt), whereas the highest rank coals show the least decrease in k(coke). The energies of activation of melting and coking were not significantly affected by pressure. The investigation also reveals increases or decreases in the respective times of softening, maximum fluidity, resolidification and total time of fluid behavior under isothermal pressurized conditions. There appears the possibility that these shifts may be rank dependent. Additionally, the lower rank coals show the largest relative increase in their fluidities when subjected to pressure. Empirical relationships were derived in order to quantitatively predict the maximum isothermal fluidity for most (fluid) coals at a given pressure.  相似文献   
67.
Pre-metal-deposition reactive ion etching (RIE) was performed on an Al0.3Ga0.7N/AlN/GaN heterostructure in order to improve the metal-to-semiconductor contact resistance. An optimum AlGaN thickness for minimizing contact resistance was determined. An initial decrease in contact resistance with etching time was explained in terms of removal of an oxide surface layer and/or by an increase in tunnelling current with the decrease of the AlGaN thickness. The presence of a dissimilar surface layer was confirmed by an initial nonuniform etch depth rate. An increase in contact resistance for deeper etches was experienced. The increase was related to depletion of the two-dimensional (2-D) electron gas (2-DEG) under the ohmics. Etch depths were measured by atomic force microscopy (AFM). The contact resistance decreased from about 0.45 Ωmm for unetched ohmics to a minimum of 0.27 Ωmm for 70 Å etched ohmics. The initial thickness of the AlGaN layer was 250 Å. The decrease in contact resistance, without excessive complications on device processing, supports RIE etching as a viable solution to improve ohmic contact resistance in AlGaN/GaN HEMTs  相似文献   
68.
69.
70.
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