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   5703篇
  免费   781篇
  国内免费   706篇
电工技术   1219篇
综合类   489篇
化学工业   261篇
金属工艺   123篇
机械仪表   575篇
建筑科学   148篇
矿业工程   56篇
能源动力   163篇
轻工业   64篇
水利工程   21篇
石油天然气   42篇
武器工业   96篇
无线电   422篇
一般工业技术   174篇
冶金工业   103篇
原子能技术   24篇
自动化技术   3210篇
  2024年   67篇
  2023年   169篇
  2022年   176篇
  2021年   235篇
  2020年   296篇
  2019年   354篇
  2018年   235篇
  2017年   289篇
  2016年   302篇
  2015年   296篇
  2014年   343篇
  2013年   429篇
  2012年   311篇
  2011年   419篇
  2010年   277篇
  2009年   335篇
  2008年   309篇
  2007年   333篇
  2006年   333篇
  2005年   266篇
  2004年   236篇
  2003年   186篇
  2002年   149篇
  2001年   118篇
  2000年   110篇
  1999年   75篇
  1998年   84篇
  1997年   67篇
  1996年   57篇
  1995年   56篇
  1994年   36篇
  1993年   39篇
  1992年   28篇
  1991年   22篇
  1990年   27篇
  1989年   12篇
  1988年   13篇
  1987年   11篇
  1986年   9篇
  1985年   10篇
  1984年   13篇
  1983年   9篇
  1982年   7篇
  1981年   9篇
  1980年   5篇
  1979年   3篇
  1978年   4篇
  1974年   3篇
  1959年   2篇
  1954年   3篇
排序方式: 共有7190条查询结果,搜索用时 31 毫秒
21.
Consistent calculation of fugacities of fluid mixtures remains as one of the most important subjects in contemporary molecular thermodynamics. In practice, equations of state (EOSs) and gE-models have been used. However, most EOSs are erroneous for condensed phases at high densities and gE-models are inapplicable for pressuresensitive systems. Recently to remedy the shortcomings in both approaches, there has been a surge of new gE-EOS mixing rules. By equating any set of EOS and gE-models, the limitations in both approaches could be resolved significantly. However, the self-consistency in the underlying concept of those mixing rules remains controversial. During the last several years, the present authors proposed a new lattice-fluid EOS and its simplification relevant to phase equilibrium calculations. Without employing any gE-EOS mixing rule and with only two parameters for a pure component and one adjustable interaction energy parameter for a binary mixture, results obtained to date demonstrated that the EOSs are quantitatively applicable to a great variety of phase equilibrium properties of mixtures, especially, for complex and/or macromolecular systems. In the present article we summarize the EOSs and extended the applications to liquid-liquid Equilibria. In part I, we discussed briefly the molecular thermodynamic aspects of general derivation of the EOS and a brief discussion of applying the EOSs to pure fluids while the illustrative application to various real mixture systems is discussed in part II.  相似文献   
22.
余海棠 《包装工程》2003,24(4):123-125
20世纪90年代,后现代主义被嫁接到中国的视觉艺术中。在中国当代艺术发展处于多种可能时,许多画家自觉不自觉地将眼光投向市场,于是趣味取代了艺术家精神创造者的位置,提供给艺术家一个俗人的标准,一个消费与被消费者的角色与机会,但后现代主义的增生原则,真正体现了艺术的多样性和丰富性。  相似文献   
23.
Using state assignment to minimize power dissipation and area for finite state machines is computationally hard.Most of published results show that the reduction of switching activity often trades with area penalty.In this paper,a new approach is proposed.Experimental results show a significant reduction of switching activity without area penalty compared with previous publications.  相似文献   
24.
Obtaining shorter regular expressions from finite-state automata   总被引:1,自引:0,他引:1  
We consider the use of state elimination to construct shorter regular expressions from finite-state automata (FAs). Although state elimination is an intuitive method for computing regular expressions from FAs, the resulting regular expressions are often very long and complicated. We examine the minimization of FAs to obtain shorter expressions first. Then, we introduce vertical chopping based on bridge states and horizontal chopping based on the structural properties of given FAs. We prove that we should not eliminate bridge states until we eliminate all non-bridge states to obtain shorter regular expressions. In addition, we suggest heuristics for state elimination that leads to shorter regular expressions based on vertical chopping and horizontal chopping.  相似文献   
25.
26.
本文研究了不确定的对称组合系统的稳定化控制器与观测器的设计问题,给出一种设计稳定化控制器与观测器的方法,在这种设计方法中,使给定的带有不确定性的对称组合系统稳定的状态反馈增益矩阵和观测器增益矩阵可由低阶代数Riccati方程的解导出。  相似文献   
27.
无源微波遥感用于地震预报的实验研究   总被引:4,自引:1,他引:3  
对无源微波遥感用于地震预报在理论研究的基础上对不同岩性不同结构的岩石试件进行了加载实验,测量了岩石试件的微波辐射随载荷的变化.实验得出:岩石试件的微波辐射能量随岩石应力状态变化而显著变化;而且,不同的波段变化的幅度不同;同一波段不同极化方式的波随应力变化的变化量也不同;微波辐射能量的变化能够被卫星微波遥感探测器探测到.实验还发现,岩石试件临破裂前出现明显的微波辐射异常.  相似文献   
28.
在异步电动机磁场定向数学模型的基础上,给出了恒磁条件下异步电动机的解耦模型及传动系统的线性状态方程,并提出了重构负载扰动转矩的线性状态观测器。利用重构的负载转矩在矢量控制系统中进行扰动前馈,明显地提高了系统的抗负载扰动能力,从而为进一步提高矢量控制系统的动态性能开辟了一条有效的途径。  相似文献   
29.
Necessary and sufficient conditions for the existence of a static state feedback that achieves noninteraction and internal stability are obtained. This is accomplished by first characterizing the set of all controllability subspaces (distributions) that can arise as solutions to the noninteracting control problem. This characterization is then used to identify a fixed internal dynamics that is common to every noninteractive closed loop. The stability properties of this dynamics is shown to be the key factor in the problem of achieving noninteracting control with internal stability.  相似文献   
30.
A well‐known control system which can reduce the adverse effects of disturbances is a disturbance observer. However, in many cases of mechanical systems, system disturbances which do not satisfy the matching condition may be imposed. Therefore, it may be difficult to reduce the adverse effects of the disturbances by the traditional disturbance observer. In this paper, a method of control system synthesis for disturbance rejection using a dual observer is proposed. This method is based on the zeroing induced by the disturbance localization problem. This problem may be solved by dividing the state space into observable subspace and unobservable subspace. As compared with an H controller based on perfect observation, the usefulness of the proposed control system for disturbance rejection is demonstrated by numerical simulations for a two‐mass spring system. © 2002 Scripta Technica, Electr Eng Jpn, 138(4): 50–60, 2002; DOI 10.1002/eej.1138  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