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   84529篇
  免费   943篇
  国内免费   235篇
电工技术   786篇
综合类   2318篇
化学工业   11602篇
金属工艺   4839篇
机械仪表   3031篇
建筑科学   2207篇
矿业工程   563篇
能源动力   1112篇
轻工业   3621篇
水利工程   1274篇
石油天然气   342篇
无线电   9275篇
一般工业技术   16377篇
冶金工业   2711篇
原子能技术   259篇
自动化技术   25390篇
  2021年   19篇
  2020年   17篇
  2019年   31篇
  2018年   14454篇
  2017年   13383篇
  2016年   9970篇
  2015年   620篇
  2014年   248篇
  2013年   237篇
  2012年   3156篇
  2011年   9437篇
  2010年   8300篇
  2009年   5561篇
  2008年   6799篇
  2007年   7800篇
  2006年   139篇
  2005年   1233篇
  2004年   1159篇
  2003年   1189篇
  2002年   549篇
  2001年   98篇
  2000年   183篇
  1999年   66篇
  1998年   74篇
  1997年   42篇
  1996年   57篇
  1995年   19篇
  1994年   27篇
  1993年   23篇
  1992年   20篇
  1991年   32篇
  1969年   25篇
  1968年   44篇
  1967年   35篇
  1966年   42篇
  1965年   44篇
  1964年   13篇
  1963年   29篇
  1962年   22篇
  1961年   18篇
  1960年   31篇
  1959年   35篇
  1958年   38篇
  1957年   36篇
  1956年   36篇
  1955年   64篇
  1954年   68篇
  1953年   15篇
  1951年   18篇
  1950年   19篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
We explore an efficient scheme for transferring quantum state between an optomechanical cavity and nuclear spins of nitrogen-vacancy centers in diamond, where quantum information can be efficiently stored (retrieved) into (from) the nuclear spin ensemble assisted by a mechanical resonator in a dispersive regime. Our scheme works for a broad range of cavity frequencies and might have potential applications in employing the nuclear spin ensemble as a memory in quantum information processing. The feasibility of our protocol is analyzed using currently available parameters.  相似文献   
32.
This paper presents a modular designed autonomous bolt tightening shaft system with an adaptive fuzzy backstepping control approach developed for it. The bolt tightening shaft is designed for the autonomous bolt tightening operation, which has huge potential for industry application. Due to the inherent nonlinear and uncertain properties, the bolt tightening shaft and the bolt tightening process are mathematically modeled as an uncertain strict feedback system. With the adaptive backstepping and approximation property of fuzzy logic system, the controller is recursively designed. Based on the Lyapunov stability theorem, all signals in the closed-loop system are proved to be uniformly ultimately bounded and the torque tracking error exponentially converges to a small residue. And the effectiveness and performance of the proposed autonomous system are verified by the simulation and experiment results on the bolt tightening shaft system.  相似文献   
33.
The paper is concerned with the problem of positive L 1-gain filter design for positive continuous-time Markovian jump systems with partly known transition rates. Our aim is to design a positive full-order filter such that the corresponding filtering error system is positive and stochastically stable with L 1-gain performance. By applying a linear co-positive Lyapunov function and free-connection weighting vectors, the desired positive L 1-gain filter is provided. The obtained theoretical results are demonstrated by numerical examples.  相似文献   
34.
We focus on practical Hierarchical Identity-Based Broadcast Encryption (HIBBE) with semantic security against adaptively chosen-ciphertext attacks (CCA2) in the standard model. We achieve this goal in two steps. First, we propose a new HIBBE scheme that is secure against chosen-plaintext attacks (CPA). Compared with the existing HIBBE scheme that is built from composite-order bilinear groups, our construction is based on prime-order bilinear groups. The much better efficiency of group operations in prime-order bilinear groups makes our proposed HIBBE scheme more practical. Then, we convert it into a CCA2-secure scheme at the cost of a one-time signature. Instead of extending one user hierarchy in the Canetti–Halevi–Katz approach from CPA-secure (\(l+1\))-Hierarchical Identity-Based Encryption [(\(l+1\))-HIBE] to CCA2-secure \(l\)-HIBE, our construction merely adds one on-the-fly dummy user in the basic scheme. We formally prove the security of these two schemes in the standard model. Comprehensive theoretical analyses and experimental results demonstrate that the proposed HIBBE schemes achieve desirable performance.  相似文献   
35.
36.
This paper studies the lateral and longitudinal path tracking control of four-wheel steering vehicles. By the introduction of virtual points, a robust and adaptive path tracking control strategy is proposed to simultaneously counteract modeling uncertainties, unexpected disturbances, and coupling effects. An adaptive model-based feedforward adaptive term and the robust integral of the sign of the error (RISE) feedback term can be used to yield an asymptotic tracking result, which improve the tracking performance and reduce the control effort. The stability of closed-loop system is analyzed using a Lyapunov-based method. Simulation results are provided to demonstrate the performance of the proposed controller under different driving conditions.  相似文献   
37.
In this paper, the resilient control under the Denial-of-Service (DoS) attack is rebuilt within the framework of Joint Directors of Laboratories (JDL) data fusion model. The JDL data fusion process is characterized by the so-called Game-in-Game approach, where decisions are made at different layers. The interactions between different JDL levels are considered which take the form of Packet Delivery Rate of the communication channel. Some criterions to judge whether the cyber defense system is able to protect the underlying control system is provided. Finally, a numerical example is proposed to verify the validity of the proposed method.  相似文献   
38.
Zusammenfassung Im Zeitalter der Informationsgesellschaft, so wurde postuliert, spielten r?umliche Distanzen keine Rolle mehr und unsere r?umliche Mobilit?t n?hme ab. Die Mobilit?t in den letzten Jahren, speziell die Freizeitmobilit?t, hat hingegen zugenommen. Die Bereitstellung ortsbezogener Dienste – ,,Location-based Services“ – unterstützt und f?rdert dieses Verhalten.  相似文献   
39.
This paper studies fitted value iteration for continuous state numerical dynamic programming using nonexpansive function approximators. A number of approximation schemes are discussed. The main contribution is to provide error bounds for approximate optimal policies generated by the value iteration algorithm.   相似文献   
40.
For direct imprinting of metals, hard materials such as diamond and SiC have been used to construct mold inserts in preference to Si, despite the ease in fabricating Si-based micro-/nano- scale structures. In this communication, we demonstrate that micron scale Al structures can be replicated with good fidelity at room temperature by compression molding with Si inserts without incurring insert damage. We further report on results of a finite element analysis of the mechanics of the molding process. The finite element results provide some understanding of the observed lack of damage to the Si inserts.  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