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   281128篇
  免费   22018篇
  国内免费   11819篇
电工技术   16306篇
技术理论   29篇
综合类   17979篇
化学工业   46582篇
金属工艺   16120篇
机械仪表   17580篇
建筑科学   22329篇
矿业工程   8838篇
能源动力   7970篇
轻工业   16732篇
水利工程   4574篇
石油天然气   19295篇
武器工业   2105篇
无线电   31440篇
一般工业技术   33351篇
冶金工业   15066篇
原子能技术   2916篇
自动化技术   35753篇
  2024年   1243篇
  2023年   4619篇
  2022年   7916篇
  2021年   11196篇
  2020年   8586篇
  2019年   7220篇
  2018年   8109篇
  2017年   9108篇
  2016年   8174篇
  2015年   10851篇
  2014年   13709篇
  2013年   16278篇
  2012年   17493篇
  2011年   18963篇
  2010年   16631篇
  2009年   15676篇
  2008年   15485篇
  2007年   14870篇
  2006年   15346篇
  2005年   13272篇
  2004年   9084篇
  2003年   7885篇
  2002年   7219篇
  2001年   6459篇
  2000年   6745篇
  1999年   7843篇
  1998年   6429篇
  1997年   5365篇
  1996年   5083篇
  1995年   4226篇
  1994年   3409篇
  1993年   2409篇
  1992年   1931篇
  1991年   1517篇
  1990年   1133篇
  1989年   912篇
  1988年   688篇
  1987年   431篇
  1986年   335篇
  1985年   251篇
  1984年   170篇
  1983年   137篇
  1982年   151篇
  1981年   114篇
  1980年   89篇
  1979年   43篇
  1978年   28篇
  1977年   20篇
  1976年   35篇
  1973年   13篇
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
41.
Two kinds of biosensors for amino acids (one with nonspecific enzyme as bioelement, the other with specific enzyme(s) as bioelement), including their principles, applications, recent researches and future trends were discussed in detail. 61 references were given. A part of work for gaining Ph. D in chemical and biochemical application at FPMs (Mons, Belgique) Synopsis of the first author Xia Jinlan, Male, born in 1963, now at Facult’e Polytechnique de Mons, Belgique  相似文献   
42.
Bayesian analysis is used to show that Wald's sequential probability ratio test with varying thresholds is optimal for the nonstationary situation, where the observed samples are independent but not identically distributed. Some important properties useful for the design of the test thresholds are discussed. Wald's lower bound, generalized to the nonstationary situation, is also presented. The results have important applications in situations where the observed signal is time-varying. such as in radar signal processing, image processing, and spread spectrum communications  相似文献   
43.
Carboxymethyl-2-diethylaminoethylcellulose (CM-DEAE cellulose) was prepared by etherification of carboxymethylcellulose with diethylaminoethyl chloride in a NaOH solution. The behaviour of CM-DEAE cellulose in aqueous solution was studied by viscosity and GPC measurements. The degree of substitution (DS) and existing states of DEAE substituents were examined by the use of proton NMR, and those of the CM substituents were observed with FT-IR. The results reveal that the reduced viscosity and apparent molecular size of CM-DEAE cellulose vary with the concentration of sodium chloride and changes in pH and DS. These phenomena can be explained in terms of inter- and intra-molecular ionic interactions.  相似文献   
44.
The crystallization behaviour of three amorphous alloys, Co50Ni25Si15B10, Ni50Co25Si15B10 and Ni50Co25P15B10, was studied by means of differential thermal analysis in conjunction with scanning transmission electron microscopy. Isochronal annealing showed a strong dependence of crystallization on scan rate over the range of 1.99 to 20.70 K min–1. At high Co/Ni ratios, a sequential two-stage crystallization process involving primary MS-I phase followed by MS-II phase precipitation was observed. At low Co/Ni ratios MS-I and MS-II crystallization were concurrent and inseparable. Replacement of the metalloid Si with P as the glass-former dramatically reduced the activation energy for crystallization as well as the crystallization temperature. A mechanistic understanding of these findings was pursued in light of TEM/STEM microanalysis  相似文献   
45.
Methods of optimizing the design of electrical machines are discussed. The augmented Lagrangian multiplier method is described, and an algorithm for this method is introduced. The method is compared with the more familiar exterior penalty function method using, as an example, the cost optimization of permanent magnetic variable-speed drive motors. The improved method is shown to be superior, both in its ability to reach an optimum consistently and in the number of required iterations  相似文献   
46.
47.
This paper examines bidding strategies in a bilateral market in which generating companies submit bids to loads. A load accepts electricity delivery from the generator with the lowest bid at its bid price as long as this price is not higher than the load's willingness to pay. Necessary and sufficient conditions of Nash equilibrium (NE) bidding strategy are derived based on a generic generating cost matrix and the loads' willingness to pay vector. The study shows that in any NE, efficient allocation is achieved. Furthermore, all Nash equilibria are revenue equivalent for the generators. Based on the necessary and sufficient conditions, this problem is formulated as an optimal assignment problem. Network optimization techniques are applied to calculate NE bid prices for the generators  相似文献   
48.
HHD型核子秤电离室已成功地使用于HCS型核子秤.对它的各种物理性能指标进行了检测,各项性能指标都达到了设计要求。  相似文献   
49.
50.
有扰对称信道平均信息量的计算   总被引:3,自引:1,他引:2  
郑世林 《通信技术》2002,(12):32-33
照相手机让诺基亚抢了风头,这真是亚洲人的失策。在日本和韩国,内置摄像头的手机早就不是什么值得炫耀的东西了。不过日本人的动作还是很快的,GD88和N8一副后来居上的架势,让人不敢小瞧。  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