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   110158篇
  免费   9720篇
  国内免费   5123篇
电工技术   6921篇
技术理论   3篇
综合类   7100篇
化学工业   17035篇
金属工艺   6278篇
机械仪表   6635篇
建筑科学   8263篇
矿业工程   2469篇
能源动力   3166篇
轻工业   8409篇
水利工程   2258篇
石油天然气   4996篇
武器工业   888篇
无线电   14267篇
一般工业技术   13890篇
冶金工业   5671篇
原子能技术   1365篇
自动化技术   15387篇
  2024年   506篇
  2023年   1762篇
  2022年   3301篇
  2021年   4515篇
  2020年   3279篇
  2019年   2751篇
  2018年   3019篇
  2017年   3567篇
  2016年   3139篇
  2015年   4444篇
  2014年   5713篇
  2013年   7075篇
  2012年   7544篇
  2011年   8112篇
  2010年   7114篇
  2009年   6776篇
  2008年   6626篇
  2007年   6382篇
  2006年   6115篇
  2005年   4976篇
  2004年   3370篇
  2003年   2805篇
  2002年   2827篇
  2001年   2418篇
  2000年   2244篇
  1999年   2239篇
  1998年   2060篇
  1997年   1768篇
  1996年   1606篇
  1995年   1337篇
  1994年   1050篇
  1993年   849篇
  1992年   696篇
  1991年   523篇
  1990年   437篇
  1989年   335篇
  1988年   293篇
  1987年   206篇
  1986年   186篇
  1985年   158篇
  1984年   116篇
  1983年   87篇
  1982年   81篇
  1981年   76篇
  1980年   61篇
  1979年   45篇
  1978年   39篇
  1977年   42篇
  1976年   77篇
  1974年   27篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
61.
MIP-CGP工艺专用催化剂CGP-1的开发与应用   总被引:11,自引:3,他引:8  
阐述了生产汽油组分满足欧Ⅲ排放标准并多产丙烯的催化裂化工艺(简称MIP-CGP)专用催化剂(简称CGP-1)的研究开发与工业应用结果。CGP-1催化剂的基质具有良好的容炭性能,使活性组元受到良好保护,其优势作用在第二反应区得以充分发挥,具有更高的氢转移活性和强的汽油小分子烯烃裂化活性。中国石化九江分公司和镇海炼化公司的MIP-CGP工业试验标定结果表明,与常规FCC相比,采用CGP-1催化剂的MIP-CGP技术在生产烯烃体积分数小于18%的汽油组分的同时,丙烯产率达到8%以上。此外,汽油诱导期大幅提高,抗爆指数增加;总液体收率有所提高,干气产率下降,焦炭选择性良好。  相似文献   
62.
In this note, we revisit the problem of global practical stabilization for planar linear systems subject to actuator saturation and input additive disturbances. A parameterized linear state feedback law is designed such that, by tuning the value of the parameter, all trajectories of the closed-loop system converge to an arbitrarily small neighborhood of the origin in a finite time and remain in there.  相似文献   
63.
In this paper, we discuss average consensus problem in undirected networks of dynamic agents with fixed and switching topologies as well as multiple time-varying communication delays. By employing a linear matrix inequality method, we prove that all the nodes in the network achieve average consensus asymptotically for appropriate communication delays if the network topology is connected. Particularly, several feasible linear matrix inequalities are established to determine the maximal allowable upper bound of time-varying communication delays. Numerical examples are given to demonstrate the effectiveness and the sharpness of the theoretical results.  相似文献   
64.
This paper is a tutorial on GrÖbner bases and a survey on the applications of GrÖbner bases in the broad field of signals and systems. A reasonably detailed review is given of several fundamental theoretical issues that occur in the use of GrÖbner bases in multidimensional signals and systems applications. These topics include the primeness of multivariate polynomial matrices, multivariate unimodular polynomial matrix completion, and prime factorization of multivariate polynomial matrices. A brief review is also presented on the wide-ranging applications of GrÖbner bases in multidimensional as well as one-dimensional circuits, networks, control, coding, signals, and systems and other related areas like robotics and applied mechanics. The impact and scope of GrÖbner bases in signals and systems are highlighted with respect to what has already been accomplished as a stepping stone to expanding future research.   相似文献   
65.
本文结合生产实际 ,介绍陶膜的清洗工艺 ,并通过比较试验获得优化的清洗方案。  相似文献   
66.
67.
介绍液态软起动技术在济钢 15000 m3/h制氧机配套的 6000 kW同步电动机上的应用情况,阐述了系统的原理、特点、仿真计算及实际应用后达到的效果.  相似文献   
68.
Spectral and structural characteristics of distributed Bragg reflector (DBR) in vertical-cavity surface-emitting lasers were studied with photoluminescence and double- crystal X- ray diffraction measurement. The expected high quality epitaxial DBR structure was verified. In the X- ray double- crystal rocking curves of DBR the zeroth- order peak, the first and second order satellite peaks were measured. Splitting of diffraction peak appeared in the rocking curves was analyzed. The effects of introduced deep energy levels on the structural perfection and optical properties were discussed.  相似文献   
69.
Reduced integration is frequently used in evaluating the element stiffness matrix of quadratically interpolated finite elements. Typical examples are the serendipity (Q8) and Lagrangian (Q9) membrane finite elements, for which a reduced 2 × 2 Gauss–Legendre integration rule is frequently used, as opposed to full 3 × 3 Gauss–Legendre integration. This ‘softens’ these element, thereby increasing accuracy, albeit at the introduction of spurious zero energy modes on the element level. This is in general not considered problematic for the ‘hourglass’ mode common to Q8 and Q9 elements, since this spurious mode is non‐communicable. The remaining two zero energy modes occurring in the Q9 element are indeed communicable. However, in topology optimization for instance, conditions may arise where the non‐communicable spurious mode associated with the elements becomes activated. To effectively suppress these modes altogether in elements employing quadratic interpolation fields, two modified quadratures are employed herein. For the Q8 and Q9 membrane elements, the respective rules are a five and an eight point rule. As compared to fully integrated elements, the new rules enhance element accuracy due to the introduction of soft, higher‐order deformation modes. A number of standard test problems reveal that element accuracy remains comparable to that of the under‐integrated counterparts. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
70.
介绍焦化行业钛设备的应用,剖析了分块式钛泡罩塔盘的结构特点,并对其经济性作了分析。  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