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   293445篇
  免费   5624篇
  国内免费   1927篇
电工技术   5925篇
技术理论   5篇
综合类   1327篇
化学工业   48042篇
金属工艺   11803篇
机械仪表   8465篇
建筑科学   7799篇
矿业工程   1810篇
能源动力   6150篇
轻工业   29832篇
水利工程   3111篇
石油天然气   6101篇
武器工业   250篇
无线电   29536篇
一般工业技术   54953篇
冶金工业   54737篇
原子能技术   5814篇
自动化技术   25336篇
  2021年   3085篇
  2020年   2162篇
  2019年   2564篇
  2018年   4285篇
  2017年   4159篇
  2016年   4640篇
  2015年   3632篇
  2014年   5573篇
  2013年   13377篇
  2012年   9153篇
  2011年   11790篇
  2010年   9439篇
  2009年   9958篇
  2008年   10886篇
  2007年   10940篇
  2006年   9426篇
  2005年   8241篇
  2004年   7341篇
  2003年   6801篇
  2002年   6779篇
  2001年   6754篇
  2000年   6323篇
  1999年   6380篇
  1998年   15035篇
  1997年   10889篇
  1996年   8225篇
  1995年   6161篇
  1994年   5579篇
  1993年   5416篇
  1992年   4198篇
  1991年   3967篇
  1990年   4022篇
  1989年   3978篇
  1988年   3733篇
  1987年   3213篇
  1986年   3211篇
  1985年   3668篇
  1984年   3563篇
  1983年   3268篇
  1982年   2864篇
  1981年   3129篇
  1980年   2857篇
  1979年   3014篇
  1978年   2888篇
  1977年   3092篇
  1976年   4162篇
  1975年   2580篇
  1974年   2388篇
  1973年   2457篇
  1972年   2035篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
This research was supported under project No. 6.02.02/128-93 as part of the state scientific-technical program on future information technologies and systems by the Ukrainian State Committee, of Science and Technology.  相似文献   
33.
34.
Carboxyl-terminated butadiene-acrylonitrile-rubber decreases modulus and yield stress of the studied epoxy but increases fracture toughness. The addition of glass bead compensates for the loss in modulus but has little effect on yield stress. However, it significantly contributes to the fracture toughness by providing additional mechanisms for toughening of both the unmodified and rubber-modified epoxy. For the toughened epoxies studied, fracture surfaces gave only limited information on fracture mechanisms since significant energy absorption also occurs in the material below the fracture surface. Suggestions for suitable material compositions for fiber composite matrices are given.  相似文献   
35.
The technological process of cold forging applied for the first time in the production of the casing of the internal joint with races is described. The process operations of cold forging and the annealing and carburizing regimes for this part me described.  相似文献   
36.
Summary The synthesis of new high optical abrasion resistance coating materials has been undertaken by functionalizing melamine and tris(m-aminophenyl)phosphine oxide with a triethoxysilane containing reagent. These highly functionalized compounds have been used for coating a bis-phenol-A polycarbonate substrate by the sol-gel method. Preliminary data shows the abrasion resistance of the polymer substrate is considerably improved when it is coated by these optically clear materials.  相似文献   
37.
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   
38.
39.
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   
40.
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