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   34509篇
  免费   3501篇
  国内免费   2235篇
电工技术   2345篇
技术理论   9篇
综合类   3995篇
化学工业   780篇
金属工艺   276篇
机械仪表   1202篇
建筑科学   15562篇
矿业工程   1688篇
能源动力   626篇
轻工业   387篇
水利工程   1104篇
石油天然气   607篇
武器工业   246篇
无线电   2623篇
一般工业技术   1826篇
冶金工业   636篇
原子能技术   194篇
自动化技术   6139篇
  2024年   126篇
  2023年   368篇
  2022年   770篇
  2021年   903篇
  2020年   966篇
  2019年   761篇
  2018年   793篇
  2017年   864篇
  2016年   1171篇
  2015年   1343篇
  2014年   2532篇
  2013年   2056篇
  2012年   2761篇
  2011年   2925篇
  2010年   2511篇
  2009年   2507篇
  2008年   2323篇
  2007年   2588篇
  2006年   2285篇
  2005年   1810篇
  2004年   1468篇
  2003年   1190篇
  2002年   984篇
  2001年   841篇
  2000年   764篇
  1999年   568篇
  1998年   420篇
  1997年   294篇
  1996年   243篇
  1995年   220篇
  1994年   177篇
  1993年   130篇
  1992年   135篇
  1991年   80篇
  1990年   62篇
  1989年   61篇
  1988年   48篇
  1987年   28篇
  1986年   33篇
  1985年   21篇
  1984年   19篇
  1983年   13篇
  1982年   12篇
  1981年   13篇
  1980年   9篇
  1979年   12篇
  1978年   5篇
  1977年   6篇
  1976年   3篇
  1959年   8篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
In this paper an original variant of the Schwarz domain decomposition method is introduced for heterogeneous media. This method uses new optimized interface conditions specially designed to take into account the heterogeneity between the sub-domains on each sides of the interfaces. Numerical experiments illustrate the dependency of the proposed method with respect to several parameters, and confirm the robustness and efficiency of this method based on such optimized interface conditions. Several mesh partitions taking into account multiple cross points are considered in these experiments.  相似文献   
92.
93.
Markovian and semi-Markovian random processes are used to analyze the problem of optimal search for signals in a multichannel communication system with arbitrarily distributed random outputs. The search efficiency factor is found in explicit form based on state space merging, and a mathematical programming problem is set up to find a numerical suboptimal solution. __________ Translated from Kibernetika i Sistemnyi Analiz, No. 3, pp. 144–150, May–June 2007.  相似文献   
94.
The measure-theoretic definition of Kullback-Leibler relative-entropy (or simply KL-entropy) plays a basic role in defining various classical information measures on general spaces. Entropy, mutual information and conditional forms of entropy can be expressed in terms of KL-entropy and hence properties of their measure-theoretic analogs will follow from those of measure-theoretic KL-entropy. These measure-theoretic definitions are key to extending the ergodic theorems of information theory to non-discrete cases. A fundamental theorem in this respect is the Gelfand-Yaglom-Perez (GYP) Theorem [M.S. Pinsker, Information and Information Stability of Random Variables and Process, 1960, Holden-Day, San Francisco, CA (English ed., 1964, translated and edited by Amiel Feinstein), Theorem. 2.4.2] which states that measure-theoretic relative-entropy equals the supremum of relative-entropies over all measurable partitions. This paper states and proves the GYP-theorem for Rényi relative-entropy of order greater than one. Consequently, the result can be easily extended to Tsallis relative-entropy.  相似文献   
95.
CIE TC8‐01 has adopted a new color appearance model: CIECAM021 replaces the CIECAM97s.2 The new model consists of a number of refinements and simplifications of the CIECAM97s color appearance model. This article describes further tests to the robustness of the forward and reverse modes. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 99–106, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20087  相似文献   
96.
康续瀚  周亚军 《山西建筑》2007,33(30):54-55
介绍了法西斯大厦的基本情况,通过对朱赛普·特拉尼的代表作法西斯大厦的空间结构、承重结构、围护结构、立面结构的分析,以使人们更深刻地理解特拉尼的建筑思想,探索其积极的现实意义。  相似文献   
97.
An Efficient Code-Based Voxel-Traversing Algorithm   总被引:3,自引:1,他引:2  
The paper considers an efficient approach to traversing a uniformly-subdivided space pierced by a line segment. A voxel, as the basic constituent element of the uniformly subdivided space, is restricted to having the form of a cube. The algorithm works in two steps. In the first step, the so-called Bresenham voxels are identified and, by comparing their position codes, their type of connectivity is determined. To achieve the required connectivity between neighbouring voxels, the second step of the algorithm is applied to find the missing voxels. In this way, the algorithm efficiently switches between face-, edge- and vertex-connectivity. Although the algorithm works with oating-point precision, it is extremely computationally efficient, and tests of speed compared with the Müller, Cleary & Wyvill, Amanatides & Woo, and Zemčik algorithms are described.  相似文献   
98.
浅述城市规划管理信息系统   总被引:3,自引:0,他引:3  
阐述了城市规划管理信息系统的内容及其建立的方法和步骤,以及其与管理人员构成和该系统的经济效益,并指出城市规划管理信息系统利用计算机技术,科学地现代化地优化了城市规划设计与城市规划管理,为了城市建设的科学发展应加大投入,跟上时代步伐,进入城市建设的计算机时代。  相似文献   
99.
现代光学和通讯理论由于引入了傅里叶变换的方法,使计算光学系统和通讯系统的物像的对应关系简洁、清晰。该文用傅氏变换计算长为2a、照度为A的均匀缝光源在观察面上的光强分布为I(x)=│E(x)│^2=AA^2a^2(sin2πfa/2πfa)此方法也可运用于矩形孔、圆孔等。  相似文献   
100.
Detailed analyses and comparisons of urban travel forecasts prepared by applying the state-of-practice sequential procedure and the solution of a combined network equilibrium model are presented. The sequential procedure for solving the trip distribution, mode choice and assignment problems with feedback is the current practice in most transportation planning agencies, although its important limitations are well known. The solution of a combined model, in contrast, results from a single mathematical formulation, which ensures a well-converged and consistent result. Using a real network, several methods for solving the sequential procedure with feedback are compared to the solution of the combined model ESTRAUS. The results of these methods are shown to have various levels of instability. The paper concludes with a call for a new paradigm of travel forecasting practice based on an internally consistent model formulation that can be solved to a level of precision suitable for comparing alternative scenarios.  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