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   12267篇
  免费   2023篇
  国内免费   1141篇
电工技术   1368篇
综合类   1142篇
化学工业   2227篇
金属工艺   439篇
机械仪表   983篇
建筑科学   219篇
矿业工程   184篇
能源动力   741篇
轻工业   156篇
水利工程   178篇
石油天然气   456篇
武器工业   348篇
无线电   1398篇
一般工业技术   1560篇
冶金工业   281篇
原子能技术   98篇
自动化技术   3653篇
  2024年   76篇
  2023年   295篇
  2022年   491篇
  2021年   492篇
  2020年   620篇
  2019年   510篇
  2018年   461篇
  2017年   584篇
  2016年   625篇
  2015年   630篇
  2014年   772篇
  2013年   868篇
  2012年   936篇
  2011年   1043篇
  2010年   721篇
  2009年   785篇
  2008年   652篇
  2007年   778篇
  2006年   652篇
  2005年   511篇
  2004年   402篇
  2003年   403篇
  2002年   334篇
  2001年   259篇
  2000年   258篇
  1999年   185篇
  1998年   181篇
  1997年   155篇
  1996年   130篇
  1995年   107篇
  1994年   110篇
  1993年   57篇
  1992年   78篇
  1991年   49篇
  1990年   47篇
  1989年   33篇
  1988年   21篇
  1987年   23篇
  1986年   17篇
  1985年   14篇
  1984年   20篇
  1983年   14篇
  1982年   13篇
  1981年   8篇
  1980年   2篇
  1979年   2篇
  1978年   2篇
  1977年   2篇
  1973年   1篇
  1951年   1篇
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
81.
TPC方法研究催化剂热分解动力学   总被引:2,自引:1,他引:1  
设计了TPC方法研究催化剂前驱体的热分解;对TPC方法求取催化剂的热分解动力学方程进行了理论推导;采用TPC方法试验求得了Ni-Zn/C催化剂的热分解动力学参数。试验表明,TPC方法能直观、灵敏、方便地反映催化剂活性组份前驱体的本征热分解。  相似文献   
82.
Numerical simulations of acoustic scattering in the frequency domain based on hybrid methods coupling finite elements and boundary elements are the most suited for dealing with problems involving wave propagation in inhomogeneous media. Furthermore, it is necessary to resort to high performance computing to effectively solve the large size problems. However, the direct coupling yields a linear system with a matrix which is partly dense and partly sparse and thus not adapted to high performance computing. To avoid this difficulty, we present a new iterative method constructed from a non overlapping domain decomposition technique.  相似文献   
83.
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   
84.
A method of processing complex signals in passive multi-element antenna arrays based on an analysis of the natural values of the correlation matrix of the signal is considered. By means of the method it is possible to substantially increase the output signal-to-noise ratio. An iterational process by means of which optimal estimators of both the signal and the amplitude-phase distribution may be obtained, is proposed. Theoretical estimators of the efficiency of the method are given. It is proved that, in terms of the efficiency, the approach considered in the article comes close to the technique of matched filtration. Results of statistical modeling that confirm the statistical results are presented.  相似文献   
85.
The paper considers the set-theoretical approach to the joint decomposition of systems of Boolean functions of variables specified in different representation forms. The approach is based on the method of q-partitions of conjuncterms and concept of decomposition clones. Theorems on joint decomposition of a system of full and partial functions are formulated. The approach is illustrated by examples. Parts I and II of this article are published in No. 5 (2001) and No. 1 (2002). __________ Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 39–58, March–April 2007.  相似文献   
86.
Strontium-doped lanthanum manganite powders were prepared using a peroxide acetate salt based solution. The stable sol was peptized by reacting ammonium hydroxide with the precursor solution. The amorphous dried gel powders exhibit a high energy level, due to their high cations coordination and small particles, to develop the perovskite phase. This crystalline phase development from powders containing monocarboxylate ligands was characterized by thermal analysis (TG, DTG, DTA), X-ray diffraction, and IR spectroscopy. The transformation from amorphous powders into a crystallized homogeneous oxycarbonate phase in a first stage corresponds to an exothermal DTA peak at 270°C. X-ray diffraction patterns and IR spectra showed similar behavior of the powders after complete organic removal, during the conversion into perovskite phase starting at approximately 630°C and achieved about 700°C and achieved about 700°C, as well as during the sintering process.  相似文献   
87.
From the principle of of the Domain Decomposition Method (DDM), we analyse the 2nd-order linear elliptic partial differential problems and link the Separated-Layers Algorithm (SLA) with DDM. The mathematical properties of SLA and numerical example are presented to obtain satisfactory computation results. For general linear differential ones, also are the structure of SLA and its characteristics discussed.  相似文献   
88.
This work is devoted to a study of a conjugated infinite element method for Helmholtz problems in exterior domains. A formulation of this method with Lagrange multipliers defined on (semi-)infinite space is presented and analyzed in a domain decomposition context. The implementation aspects of this method in a parallel industrial acoustic software (SYSNOISE) are described in details. Numerical results show the computational efficiency of this method on acoustic scattering problems.  相似文献   
89.
The clustering of vector observations of hyperplanes is studied. Different cases of correspondence distances are proposed and investigated, including the algebraic Jack Knife one. The efficiency, constructivity, and explicit form of formulas are provided by using the pseudoinverse technique including the pseudoinverse-perturbation theory. Results important for the application of pseudoinverse and related operators are presented. __________ Translated from Kibernetika i Sistemnyi Analiz, No. 4, pp. 73–92, July–August 2007.  相似文献   
90.
研究了渠道梯级电站群的运行特点,在分析基础上建立了这类电站群化高度的分解协调模型,并采用模拟和动态规划相结合的方法,求解了海南松涛灌区5级电站群的优化调度问题.且求解优化模型的基础上对渠道梯级电站群系统和站内运行提出了具体的调控规则.  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