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   44754篇
  免费   5148篇
  国内免费   4213篇
电工技术   3584篇
技术理论   2篇
综合类   7001篇
化学工业   3450篇
金属工艺   1580篇
机械仪表   2753篇
建筑科学   2907篇
矿业工程   858篇
能源动力   948篇
轻工业   3476篇
水利工程   1144篇
石油天然气   964篇
武器工业   504篇
无线电   6026篇
一般工业技术   4808篇
冶金工业   971篇
原子能技术   750篇
自动化技术   12389篇
  2024年   231篇
  2023年   791篇
  2022年   1397篇
  2021年   1454篇
  2020年   1379篇
  2019年   1305篇
  2018年   1275篇
  2017年   1474篇
  2016年   1555篇
  2015年   1599篇
  2014年   2354篇
  2013年   2722篇
  2012年   3048篇
  2011年   3297篇
  2010年   2594篇
  2009年   2787篇
  2008年   2863篇
  2007年   3263篇
  2006年   2901篇
  2005年   2573篇
  2004年   2165篇
  2003年   1770篇
  2002年   1474篇
  2001年   1274篇
  2000年   1091篇
  1999年   909篇
  1998年   724篇
  1997年   637篇
  1996年   574篇
  1995年   496篇
  1994年   436篇
  1993年   323篇
  1992年   282篇
  1991年   233篇
  1990年   214篇
  1989年   189篇
  1988年   127篇
  1987年   73篇
  1986年   42篇
  1985年   39篇
  1984年   29篇
  1983年   35篇
  1982年   25篇
  1981年   16篇
  1980年   17篇
  1979年   10篇
  1978年   6篇
  1977年   6篇
  1976年   8篇
  1959年   4篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
中国古典园林三维造型研究   总被引:1,自引:0,他引:1  
论述了采用层次结构化及参数化三维造型方法,建立一个以造型函数库为核心,从而构造各类、各级园林景观构件表面模型的方法和过程。对于某些非建筑类的园林配景构件,采用了Fractal方法进行造型。  相似文献   
22.
不等波纹函数低通原型的理论及应用   总被引:3,自引:0,他引:3  
李壮  甘仲民 《通信学报》1993,14(5):89-99
本文提出不等波纹函数低通原型,并对其理论进行初步探讨。切比雪夫函数及最平坦型巴特活兹函数皆为其特例。文中给出不等波纹函数的几个性质,最后给出两个应用实例,消除耦合环自感部分的影响;抑制高次模的微带圆盘腔带通滤波器。  相似文献   
23.
In this paper, symbolic code matrix ,constant matrix and count matrix are defined .The first twomatrices are used to describe the elemental expression of augmented matrix and the nede admittance equa-tion is thus obtained. The third matrix is used to obtain the incoming degree matrix, and according to thematrix all the 1- factors of the Coates graph are given. By using the data code, the determinant is expandedand the same items in the expansion are merged. Thus the symbolic network function in which no term can-cellation occurs is generated.  相似文献   
24.
Good methods are needed to specify, test, and debug material-handling control logic. This article surveys a number of representative methods for defining and describing control algorithms for programmable material-handling equipment used in flexible manufacturing systems. The methods are evaluated with regard to their suitability for communication between people and as bases for interfaces to automatic program generators. It is concluded that no single method is entirely satisfactory. Three methods (position diagrams, function block diagrams, and operation networks) have potential to be combined into an effective hybrid approach that minimizes the need for the user to switch between various conceptual models.  相似文献   
25.
Chitosan (CS)/poly(vinyl alcohol) (PVA) and Chitosan/poly(2-hydroxyethyl methacrylate) (P2HEM) blends have been studied through molecular dynamic simulations. In a previous work it was found miscibility between these polymers and it was attributed to hydrogen bonding formation. However, the experimental information obtained was not enough to know which of the interacting groups of Chitosan, i.e. -CH2OH or -NH2, are responsible of the interaction. Therefore, we have performed molecular dynamics simulation runs of 1 ns in order to calculate radial distribution functions (RDF) for the groups tentatively involved in the interaction. The results are correlated with our previous experimental data. This way, we have obtained a more precise conclusive information about the interactions involved as function of the blends composition. For low compositions of PVA and P2HEM the interaction is predominantly with the hydroxymethyl groups of CS while as the composition of PVA and P2HEM increases, the interaction with the amine groups increases.  相似文献   
26.
We give an elementary proof of the well-known fact that shift-invariant operators onL 2[0, ∞) are represented by transfer functions which are bounded and analytic on the right open half-plane. We prove a generalization to Banach space-valuedL p -functions, where 1≤p<∞. We show that the result no longer holds forp=∞. This research was supported partially by the Weizmann Fellowship, and partially by the Air Force Office of Scientific Research under Contract F49620-86-C-0111.  相似文献   
27.
28.
本文的主要目的是利用初等方法研究Smarandache可乘函数在简单数集中的均值性质,并给出一个有趣的渐近公式。  相似文献   
29.
A method is considered to solve a conditional optimization problem with a linear-fractional objective function over permutations. The performance of sub algorithms to solve this problem is evaluated. The practical efficiency of the algorithm is analyzed by conducting numerical experiments. __________ Translated from Kibernetika i Sistemnyi Analiz, No. 4, pp. 133–146, July–August 2007.  相似文献   
30.
We propose a general modeling framework to evaluate the performance of cache consistency algorithms. In addition to the usual hit rate, we introduce the hit* rate as a consistency measure, which captures the fraction of non-stale downloads from the cache. We apply these ideas to the analysis of the fixed TTL consistency algorithm in the presence of network delays. The hit and hit* rates are evaluated when requests and updates are modeled by renewal processes. Classical results on the renewal function lead to various bounds.  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