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   123605篇
  免费   9842篇
  国内免费   3898篇
电工技术   6506篇
技术理论   8篇
综合类   5212篇
化学工业   20654篇
金属工艺   6179篇
机械仪表   7341篇
建筑科学   6755篇
矿业工程   2414篇
能源动力   4181篇
轻工业   8322篇
水利工程   1861篇
石油天然气   3572篇
武器工业   800篇
无线电   17920篇
一般工业技术   18603篇
冶金工业   8634篇
原子能技术   1545篇
自动化技术   16838篇
  2024年   419篇
  2023年   1851篇
  2022年   3596篇
  2021年   5023篇
  2020年   3714篇
  2019年   3078篇
  2018年   3720篇
  2017年   3913篇
  2016年   4022篇
  2015年   4618篇
  2014年   6003篇
  2013年   8136篇
  2012年   8411篇
  2011年   9414篇
  2010年   7678篇
  2009年   7555篇
  2008年   7160篇
  2007年   6301篇
  2006年   5842篇
  2005年   4898篇
  2004年   3841篇
  2003年   3145篇
  2002年   2954篇
  2001年   2333篇
  2000年   2203篇
  1999年   2097篇
  1998年   2882篇
  1997年   1993篇
  1996年   1778篇
  1995年   1361篇
  1994年   1060篇
  1993年   924篇
  1992年   698篇
  1991年   613篇
  1990年   522篇
  1989年   483篇
  1988年   396篇
  1987年   319篇
  1986年   287篇
  1985年   260篇
  1984年   213篇
  1983年   163篇
  1982年   166篇
  1981年   140篇
  1980年   139篇
  1979年   109篇
  1978年   94篇
  1977年   126篇
  1976年   167篇
  1975年   83篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Although the notion of the parallelism in multidimensional applications has existed for a long time, it is so far unknown what the bound (if any) of inter-iteration parallelism in multirate multidimensional digital signal processing (DSP) algorithms is, and whether the maximum inter-iteration parallelism can be achieved for arbitrary multirate data flow algorithms. This paper explores the bound of inter-iteration parallelism within rate-balanced multirate multidimensional DSP algorithms and proves that this parallelism can always be achieved in hardware system given the availability of a large number of processors and the interconnections between them.  相似文献   
62.
In this paper, two algebraic decoders for the (103, 52, 19) and (113, 57, 15) quadratic residue codes, which have lengths greater than 100, are presented. The results have been verified by software simulation that programs in C++ language have been executed to check possible error patterns of both quadratic residue codes.  相似文献   
63.
A direct adaptive control scheme is proposed for nonminimum-phase systems in which controller parameters are estimated from the recursive least-squares algorithm and additional auxiliary parameters are obtained from the proposed polynomial identity. A local convergence is guaranteed without any extra condition. Integral action is incorporated into the adaptive controller to eliminate the steady-state error and to satisfy a condition of the unique solution for the polynomial identity. The control law used in this scheme is based on the set-point-on-I-only proportional-integral-derivative (PID) structure  相似文献   
64.
65.
66.
67.
The effects of gallia additions on the sintering behavior of gadolinia-doped ceria were systematically investigated from the following aspects: the variation in sintered density, the variation in grain size, and the existing forms of Ga2O3 in CeO2.Sintered density increased with increasing Ga2O3 content up to 5 mol.% and then it decreased with further addition of Ga2O3. Grain size also increased with increasing Ga2O3 content up to 5 mol.% and then decreased with further addition of Ga2O3. Decrease in grain size was caused by a pinning effect of Ga2O3 precipitation at grain boundaries. Lattice constant decreased with increasing Ga2O3 content up to 5 mol.%. This decrease will be due to the substitution of smaller Ga3+ ions for Ce4+ ions in the CeO2 structure. According to the results obtained from scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses, the solubility limit of Ga2O3 in Ce0.8Gd0.2O1.9 ceramics can be estimated to be nearly 5 mol.%. The addition of Ga2O3 up to the solubility limit was found to promote the sintering properties of Gd2O3-doped CeO2.  相似文献   
68.
文章探讨了GB 12437-2000标准规定的产品检验项目中,中包浸水试验的科学性问题和对批产品进行抽样时的样本代表性问题以及使用多段爆速仪测试爆速时应注意的样本量问题.  相似文献   
69.
We experimentally demonstrated the great advantages of a high dielectric constant thin film electromagnetic bandgap (EBG) power distribution network (PDN) for the suppression of power/ground noises and radiated emissions in high-performance multilayer digital printed circuit boards (PCBs). Five-layer test PCBs were fabricated and their scattering parameters measured. The power plane noise and radiated emissions were measured, investigated and related to the PDN impedance. This successfully demonstrated that the bandgap of the EBG was extended more than three times, covering a range of hundreds of MHz using a 1-cm /spl times/ 1-cm EBG cell, the SSN was reduced from 170 mV to 10 mV and the radiated emission was suppressed by 22 dB because of the high dielectric constant thin film EBG power/ground network.  相似文献   
70.
This paper looks at the concepts of entities, identities, identifiers and credentials, their definitions, and how they combine to authenticate an identity to an account, or function, within a service. Credentials can be divided into several different types on the basis of their use, origin and characteristics. In particular, types such as composite, dynamic and derived credentials will be considered, and their applicability within an identity management system. Each credential must be managed through its entire life cycle from initial registration, general use and suspension, to deletion. The notion of public (i.e. freely distributable) and private (i.e. known only to you) aspects of a credential is explored. The bindings, by trusted third parties, of identifiers and public credentials into permits and instruments of proof is explained along with the convenience, but greater exposure, of local information. Several scenarios are analysed in terms of how different types of credentials are employed during the authentication process.  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