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   499374篇
  免费   8180篇
  国内免费   3784篇
电工技术   10616篇
技术理论   5篇
综合类   2341篇
化学工业   74445篇
金属工艺   21504篇
机械仪表   15092篇
建筑科学   12817篇
矿业工程   2906篇
能源动力   12142篇
轻工业   43837篇
水利工程   5050篇
石油天然气   9402篇
武器工业   433篇
无线电   58135篇
一般工业技术   93468篇
冶金工业   98108篇
原子能技术   10136篇
自动化技术   40901篇
  2021年   4507篇
  2020年   3171篇
  2019年   3879篇
  2018年   6128篇
  2017年   6140篇
  2016年   6607篇
  2015年   5272篇
  2014年   8377篇
  2013年   21876篇
  2012年   13790篇
  2011年   18748篇
  2010年   15216篇
  2009年   16872篇
  2008年   17662篇
  2007年   17976篇
  2006年   15942篇
  2005年   14267篇
  2004年   13027篇
  2003年   12183篇
  2002年   11961篇
  2001年   12339篇
  2000年   11470篇
  1999年   11842篇
  1998年   29816篇
  1997年   21093篇
  1996年   16248篇
  1995年   11928篇
  1994年   10558篇
  1993年   10363篇
  1992年   7485篇
  1991年   7217篇
  1990年   7103篇
  1989年   6969篇
  1988年   6530篇
  1987年   5578篇
  1986年   5562篇
  1985年   6245篇
  1984年   5832篇
  1983年   5390篇
  1982年   4865篇
  1981年   5135篇
  1980年   4631篇
  1979年   4747篇
  1978年   4573篇
  1977年   5114篇
  1976年   6897篇
  1975年   4010篇
  1974年   3811篇
  1973年   3890篇
  1972年   3274篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
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   
72.
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   
73.
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   
74.
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   
75.
In this letter, a concise process technology is proposed for the first time to enable the fabrication of good quality three-dimensional (3-D) suspended radio frequency (RF) micro-inductors on bulk silicon, without utilizing the lithography process on sidewall and trench-bottom patterning. Samples were fabricated to demonstrate the applicability of the proposed process technology.  相似文献   
76.
77.
78.
The dynamic linewidth of 1.5 ?m ridge waveguide DFB lasers is shown to be reduced by shaping the pulse of the laser modulating waveform. Pulse shaping is performed by a second-order network designed to cancel the small-signal laser resonance. Results demonstrate a dynamic linewidth reduction from 1.4 ? to 0.55 ? FWHM for a 500 ps pulse.  相似文献   
79.
80.
It is suggested that the chord length distribution method could be useful for predicting double-bit upset rates in certain circumstances. A chord length distribution function for simultaneous path lengths in two parallelepipeds, applicable to a unidirectional flux, is derived. A proof of the system is outlined for the case under consideration  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