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   265421篇
  免费   29186篇
  国内免费   9149篇
电工技术   13146篇
技术理论   24篇
综合类   14164篇
化学工业   54671篇
金属工艺   13450篇
机械仪表   15218篇
建筑科学   19221篇
矿业工程   7504篇
能源动力   7192篇
轻工业   20185篇
水利工程   3871篇
石油天然气   16665篇
武器工业   1647篇
无线电   31353篇
一般工业技术   37596篇
冶金工业   13454篇
原子能技术   2264篇
自动化技术   32131篇
  2024年   994篇
  2023年   3801篇
  2022年   6485篇
  2021年   9281篇
  2020年   8323篇
  2019年   8776篇
  2018年   9476篇
  2017年   10607篇
  2016年   10250篇
  2015年   12463篇
  2014年   14817篇
  2013年   17917篇
  2012年   16685篇
  2011年   17587篇
  2010年   15849篇
  2009年   14992篇
  2008年   14254篇
  2007年   13609篇
  2006年   13919篇
  2005年   12052篇
  2004年   8561篇
  2003年   7489篇
  2002年   6708篇
  2001年   5970篇
  2000年   6486篇
  1999年   6898篇
  1998年   5551篇
  1997年   4517篇
  1996年   4238篇
  1995年   3545篇
  1994年   2841篇
  1993年   1996篇
  1992年   1558篇
  1991年   1245篇
  1990年   952篇
  1989年   757篇
  1988年   549篇
  1987年   345篇
  1986年   294篇
  1985年   212篇
  1984年   151篇
  1983年   130篇
  1982年   133篇
  1981年   106篇
  1980年   87篇
  1979年   46篇
  1978年   31篇
  1977年   25篇
  1976年   50篇
  1973年   21篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
本文实验研究了BHP的浓度对产生O2(1△)的影响。实验结果表明:当BHP浓度大于3.5M时,Cl2利用率以及O2(1△)的产率将不依赖于BHP浓度的变化而变化,同时,实验结果表明,使用低浓度的BHP对COIL的操作是可行的。  相似文献   
102.
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   
103.
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   
104.
Micro‐porous syntactic foams were produced by means of integration of glass bubbles into aluminium and zinc matrices. Preforms of glass bubbles were pressure infiltrated with the alloys AlSi9Cu9 ans ZnAl4Cu using squeeze casting. The preforms were sintered thermically without the use of bonding agents. Using the combination of different sintering steps syntactic foams with locally different densities could be produced. The mechanical properties of the foams were tested indicating a high compression strength of the foams and a very good compression energy absorption. Furthermore, corrosion behaviour and behaviour at higher temperatures were investigated.  相似文献   
105.
We define the very rich language of composed conditionals on a three‐valued logic and use this language as the communication tool between man and machine. Communication takes place for three reasons: knowledge acquisition, query, and response. Learning, thinking, and answering questions are of a pure information theoretical nature. The pivot of this knowledge processing concept is the amount of information (bit) we receive if a conditional becomes true. We follow an axiomatic approach to information theory rather than the classical probabilistic approach of Shannon; information comes first, and then comes probability. In the light of this philosophy, query and response experience new interpretations. Both, acquisition and response are realized by maximizing entropy and minimizing relative entropy, respectively. The iterative solution of these mathematical optimization problems gives new insights into the adaptation of prior knowledge to new information. Our expert system shell SPIRIT supports this kind of knowledge processing, which will be established by suitable examples. © 2003 Wiley Periodicals, Inc.  相似文献   
106.
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   
107.
Wood has long traditions as a building material, and is often used in construction elements, and as interior and exterior surfaces in the Nordic countries. In most applications, there are reaction to fire requirements to products used as surfaces, e.g. in escape routes and larger public spaces. Most wood products will therefore have to be treated with fire retardant (FR) agents to fulfil the strict requirements to properties connected to heat release and flame spread. Unfortunately, FR agents usually also increase the smoke production, as they cause a more incomplete combustion of the wood. The wood product manufacturers seek to find the optimal amount of FR additives where both heat release and smoke production in the classifying test are within the requirements given in the building regulations. This paper describes models for prediction of the European reaction to fire classes of wood products. The models are based on multivariate statistical analysis, and use test results from the cone calorimeter test as input. The presented models are, with very good precision, able to predict which Euroclass and additional smoke class a wood based product would obtain if it were to be tested in the single burning item test. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
108.
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   
109.
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   
110.
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