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   337538篇
  免费   24609篇
  国内免费   12822篇
电工技术   18274篇
技术理论   56篇
综合类   19979篇
化学工业   57375篇
金属工艺   18893篇
机械仪表   21574篇
建筑科学   26148篇
矿业工程   11078篇
能源动力   9920篇
轻工业   18879篇
水利工程   5369篇
石油天然气   23230篇
武器工业   2644篇
无线电   37146篇
一般工业技术   40239篇
冶金工业   18533篇
原子能技术   3269篇
自动化技术   42363篇
  2024年   1326篇
  2023年   5297篇
  2022年   9100篇
  2021年   12853篇
  2020年   10025篇
  2019年   8146篇
  2018年   9366篇
  2017年   10559篇
  2016年   9431篇
  2015年   12460篇
  2014年   16148篇
  2013年   19478篇
  2012年   20500篇
  2011年   22813篇
  2010年   19486篇
  2009年   18627篇
  2008年   18255篇
  2007年   17612篇
  2006年   18561篇
  2005年   16322篇
  2004年   10511篇
  2003年   9238篇
  2002年   8203篇
  2001年   7557篇
  2000年   8073篇
  1999年   9736篇
  1998年   8200篇
  1997年   6812篇
  1996年   6400篇
  1995年   5364篇
  1994年   4407篇
  1993年   3113篇
  1992年   2500篇
  1991年   1964篇
  1990年   1507篇
  1989年   1232篇
  1988年   1021篇
  1987年   681篇
  1986年   537篇
  1985年   342篇
  1984年   243篇
  1983年   205篇
  1982年   198篇
  1981年   129篇
  1980年   131篇
  1979年   67篇
  1978年   33篇
  1977年   38篇
  1976年   55篇
  1975年   20篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
This paper presents an electric arc model that can approximately represent both the static and dynamic characteristics of an arc load controlled by a power electronic circuit. The proposed model was developed from the combination and modifications of the classical Cassie and Mayr equations. The model equations have been expressed in a form suitable for incorporation into circuit simulators employing the nodal analysis method of equation solving. The model has been test-implemented in the Saber circuit simulator. Simulated and experimental results appear to be in good agreement  相似文献   
102.
The broadband wireless access industry, which provides high-rate network connections to stationary sites, has matured to the point at which it now has a standard for second-generation wireless metropolitan area networks. The IEEE standard 802.16, with its WirelessMANTM air interface, sets the stage for widespread and effective deployments worldwide. This article overviews the technical medium access control and physical layer features of this new standard  相似文献   
103.
Laguerre Functional Model has many advantages such as good approximation capability for the variances of system time‐delay, order and other structural parameters, low computational complexity, and the facility of online parameter identification, etc., so this model is suitable for complex industrial process control. A series of successful applications have been gained in linear and non‐linear predictive control fields by the control algorithm based on Laguerre Functional Model, however, former researchers have not systemically brought forward the theoretical analyses of the stability, robustness, and steady‐state performance of this algorithm, which are the keys to guarantee the feasibility of the control algorithm fundamentally. Aimed at this problem, we introduce the principles of the Incremental Mode Linear Laguerre Predictive Control (IMLLPC) algorithm, and then systemically propose the theoretical analyses and proofs of the stability and robustness of the algorithm, in addition, we also put forward the steady‐state performance analysis. At last, the control performances of this algorithm on two different physical industrial plants are presented in detail, and a number of experimental results validate the feasibility and superiority of IMLLPC algorithm. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
104.
STUDYONRESIDUESOF~(14)C-FENITROTHIONINMODELRICE-FISHECOSYSTEMANDFIELDRICE-FISHECOSYSTEMZhangZhongliang(张仲良);WangHuaxin(王化新);G?..  相似文献   
105.
用于重离子核反应实验测量的纵向电场气体电离室   总被引:1,自引:0,他引:1  
本文报道了一种新型的大动态范围,多叠层探测器系统组件之一的纵向电场气体电离室的构造,性能和在中能得离子核反应实验中的应用。  相似文献   
106.
The manufacturing message specification (MMS) is the ISO standard communication protocol specific to manufacturing. To analyze MMS design and performance, service unit automats are introduced to represent individual MMS services, while service connection Petri Nets (PNs) are constructed from these automats to describe MMS service connections and processes. This approach makes MMS protocol specification and analysis possible in terms of well-developed concepts and methods in PN theory. It leads to a distributed and hierarchical model of MMS software system by integrating service connection PNs. A generalized stochastic PN for MMS performance evaluation is obtained by incorporating service parameters and time factors into the model. A technique based on T-invariants is used to simplify the performance analysis  相似文献   
107.
We consider the problem of turbo multiuser detection for synchronous and asynchronous code-division multiple-access (CDMA) in the presence of unknown users. Turbo multiuser detectors, as previously developed, typically require knowledge of the signature waveforms of all of the users in the system and ignore users whose signature sequences are unknown, e.g., users outside the cell. We develop turbo multiuser detection for CDMA uplink systems and other environments in which the receiver has knowledge of the signature waveforms of only K˘⩽ K users. Subspace techniques are used to estimate the interference from the unknown-users and the interference estimate is subtracted from the received signal. We see that the new receiver significantly outperforms the conventional turbo multiuser receiver for moderate and high signal-to-noise ratios. It is also seen that the traditional turbo receiver provides little gain through iteration when unknown users are present  相似文献   
108.
Aerodynamic loads on a multi-bladed helicopter rotor in hovering flight were calculated by solving the three-dimensional incompressible Navier-Stokes equations. The rotor wake effects were accounted by the correction of local geometric angle of attack according to a free-wake modeling in addition to an empirical modification for the tip flow effect. The validity and efficiency of the present method were verified by the comparisons between numerical results and experimental data.  相似文献   
109.
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