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   49570篇
  免费   3978篇
  国内免费   2064篇
电工技术   2629篇
技术理论   8篇
综合类   3042篇
化学工业   8686篇
金属工艺   2726篇
机械仪表   3252篇
建筑科学   3738篇
矿业工程   1742篇
能源动力   1447篇
轻工业   2763篇
水利工程   785篇
石油天然气   3879篇
武器工业   446篇
无线电   5385篇
一般工业技术   5941篇
冶金工业   2497篇
原子能技术   492篇
自动化技术   6154篇
  2024年   245篇
  2023年   916篇
  2022年   1508篇
  2021年   2050篇
  2020年   1595篇
  2019年   1339篇
  2018年   1502篇
  2017年   1655篇
  2016年   1471篇
  2015年   1955篇
  2014年   2395篇
  2013年   2922篇
  2012年   2963篇
  2011年   3335篇
  2010年   2794篇
  2009年   2706篇
  2008年   2787篇
  2007年   2540篇
  2006年   2623篇
  2005年   2312篇
  2004年   1442篇
  2003年   1353篇
  2002年   1231篇
  2001年   1103篇
  2000年   1213篇
  1999年   1432篇
  1998年   1128篇
  1997年   947篇
  1996年   848篇
  1995年   766篇
  1994年   634篇
  1993年   471篇
  1992年   360篇
  1991年   262篇
  1990年   220篇
  1989年   153篇
  1988年   136篇
  1987年   87篇
  1986年   63篇
  1985年   35篇
  1984年   29篇
  1983年   31篇
  1982年   24篇
  1981年   15篇
  1980年   11篇
  1979年   4篇
  1978年   1篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
81.
将楼宇中的电力、照明、空调、给排水、保安、通信和广播等多方面的设备通过现场总线联接进行控制与管理是楼宇智能化的一个主要的发展方向,本设计利用对上位机和下位机的软硬件系统的设计来实现楼宇智能化控制,达到预期的效果。
Abstract:
Building the power, lighting, air conditioning, plumbing, security, communications and broadcasting, and many other devices via field bus connection for intelligent building control and management is a key to the development of the main, this design is th  相似文献   
82.
共享数据工程(SHADE)体系结构及实现描述   总被引:1,自引:1,他引:0  
文章在深入研究DIICOE的基础上,描述了DIICOE中共享数据工程(SHADE)的体系结构及实现方式。  相似文献   
83.
近年来计算机犯罪案件呈迅速增长趋势,为有效控制和侦破此类案件,急需寻找一套行之有效的侦查办案途径.归纳各种犯罪手段,分别针对单机犯罪、专用网络犯罪和互联网犯罪,提出三种解决方案.  相似文献   
84.
In this brief, the problem of global asymptotic stability for delayed Hopfield neural networks (HNNs) is investigated. A new criterion of asymptotic stability is derived by introducing a new kind of Lyapunov-Krasovskii functional and is formulated in terms of a linear matrix inequality (LMI), which can be readily solved via standard software. This new criterion based on a delay fractioning approach proves to be much less conservative and the conservatism could be notably reduced by thinning the delay fractioning. An example is provided to show the effectiveness and the advantage of the proposed result.  相似文献   
85.
Some practical models contain so complicated mathematical expressions that it is hard to determine the number and distribution of all equilibria, not mentioning the qualitative properties and bifurcations of those equilibria. The three-node recurrent neural network system with two free weight parameters, originally introduced by Ruiz, Owens, and Townley in 1997, is such a system, for which the equation of equilibria involves transcendental function tanh(x) and its iterates. Not computing coordinates of its equilibria, in this paper, we display an effective technique to determine the number and distribution of its equilibria. Without full information about equilibria, our method enables to further study qualitative properties of those equilibria and discuss their saddle node, pitchfork, and Hopf bifurcations by approximating center manifolds.  相似文献   
86.
The crossover operator has been considered "the centre of the storm" in genetic programming (GP). However, many existing GP approaches to object recognition suggest that the standard GP crossover is not sufficiently powerful in producing good child programs due to the totally random choice of the crossover points. To deal with this problem, this paper introduces an approach with a new crossover operator in GP for object recognition, particularly object classification. In this approach, a local hill-climbing search is used in constructing good building blocks, a weight called looseness is introduced to identify the good building blocks in individual programs, and the looseness values are used as heuristics in choosing appropriate crossover points to preserve good building blocks. This approach is examined and compared with the standard crossover operator and the headless chicken crossover (HCC) method on a sequence of object classification problems. The results suggest that this approach outperforms the HCC, the standard crossover, and the standard crossover operator with hill climbing on all of these problems in terms of the classification accuracy. Although this approach spends a bit longer time than the standard crossover operator, it significantly improves the system efficiency over the HCC method.  相似文献   
87.
An interactive three-dimensional finite element generation method is presented for modelling a multi-connected teeth and mandible structure. The tetrahedron is chosen as the basic element type due to its rigorous adaptability to structures with geometric complexities. The mesh generation is implemented by allocating two quadrangles in adjacent CT image slices to form a set of tetrahedrons. By examining all the possible allocations and their degradations, an algorithm is developed for interactive mesh generation, resulting in a series of tetrahedrons consistent with all the others without overlapping and spacing. The developed system was applied to a tooth-mandibular structure, generating a complicated 3D FEM model consisting of 4762 nodes and 18,534 tetrahedral elements with nine different materials. This 3D model was successfully used to evaluate different tooth restoration strategies, which proved the viability and effectiveness of the proposed method.  相似文献   
88.
89.
90.
利用Laguerre超群K上的广义次拉普拉斯算子L定义K上的Riesz位势,并证明它是Lp(1p+∞)有界和弱(1,1)有界的,即证明K上的Hardy-Littlewood-Sobolev不等式.它为进一步分析K上的偏微分方程问题提供了一个有利的工具.  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