全文获取类型
收费全文 | 23574篇 |
免费 | 2974篇 |
国内免费 | 2210篇 |
专业分类
电工技术 | 2283篇 |
技术理论 | 1篇 |
综合类 | 2770篇 |
化学工业 | 1049篇 |
金属工艺 | 393篇 |
机械仪表 | 1913篇 |
建筑科学 | 642篇 |
矿业工程 | 328篇 |
能源动力 | 568篇 |
轻工业 | 1113篇 |
水利工程 | 441篇 |
石油天然气 | 496篇 |
武器工业 | 342篇 |
无线电 | 2171篇 |
一般工业技术 | 1803篇 |
冶金工业 | 342篇 |
原子能技术 | 85篇 |
自动化技术 | 12018篇 |
出版年
2024年 | 95篇 |
2023年 | 247篇 |
2022年 | 548篇 |
2021年 | 610篇 |
2020年 | 623篇 |
2019年 | 588篇 |
2018年 | 518篇 |
2017年 | 671篇 |
2016年 | 806篇 |
2015年 | 976篇 |
2014年 | 1251篇 |
2013年 | 1532篇 |
2012年 | 1615篇 |
2011年 | 1867篇 |
2010年 | 1441篇 |
2009年 | 1717篇 |
2008年 | 1875篇 |
2007年 | 2059篇 |
2006年 | 1802篇 |
2005年 | 1454篇 |
2004年 | 1283篇 |
2003年 | 1039篇 |
2002年 | 853篇 |
2001年 | 650篇 |
2000年 | 578篇 |
1999年 | 389篇 |
1998年 | 324篇 |
1997年 | 269篇 |
1996年 | 182篇 |
1995年 | 133篇 |
1994年 | 111篇 |
1993年 | 83篇 |
1992年 | 86篇 |
1991年 | 55篇 |
1990年 | 43篇 |
1989年 | 43篇 |
1988年 | 55篇 |
1987年 | 32篇 |
1986年 | 25篇 |
1985年 | 34篇 |
1984年 | 48篇 |
1983年 | 27篇 |
1982年 | 21篇 |
1981年 | 20篇 |
1980年 | 19篇 |
1979年 | 12篇 |
1978年 | 7篇 |
1977年 | 11篇 |
1976年 | 9篇 |
1975年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
工业过程随机稳态优化控制算法的鲁棒性分析 总被引:1,自引:0,他引:1
本文给出了一种随机稳态优化算法的灵敏度分析,讨论算法解对参数变化的关系。这些参数代表系统结构参数或噪声向量的某些数字特征. 相似文献
32.
In this paper,a sequential algorithm computing the aww vertex pair distance matrix D and the path matrix Pis given.On a PRAM EREW model with p,1≤p≤n^2,processors,a parallel version of the sequential algorithm is shown.This method can also be used to get a parallel algorithm to compute transitive closure array A^* of an undirected graph.The time complexity of the parallel algorithm is O(n^3/p).If D,P and A^* are known,it is shown that the problems to find all connected components,to compute the diameter of an undirected graph,to determine the center of a directed graph and to search for a directed cycle with the minimum(maximum)length in a directed graph can all be solved in O(n^2/p logp)time. 相似文献
33.
A Linear Cross-Coupled Control System for High-Speed Machining 总被引:4,自引:0,他引:4
Q. Zhong Y. Shi J. Mo S. Huang 《The International Journal of Advanced Manufacturing Technology》2002,19(8):558-563
We present a linear cross-coupled controller to improve highspeed contouring accuracy independently of tracking accuracy in
a biaxial machine tool feed drive servomechanism. Unlike conventional cross-coupled controllers, the cross-coupled controller
presented here is a linear system, so it is very easy to perform the stability and steady-state error analysis, and to optimise
the controller parameters. The proposed controller is evaluated experimentally on a CNC LOM machine and compared to an uncoupled
controller and a conventional cross-coupled controller. Controller performance is evaluated for a circular contour at a feedrate
of 30 m min _1 . The experimental results show that the proposed controller can greatly reduce the contour error at large feedrates. The
linear cross-coupled controller is simple to implement and is practical. 相似文献
34.
I. Belda X. Llorà E. Giralt 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2006,10(4):295-304
One of the goals of computational chemistry is the automated de novo design of bioactive molecules. Despite significant progress
in computational approaches to ligand design and efficient evaluation of binding energy, novel procedures for ligand design
are required. Evolutionary computation provides a new approach to this design issue. This paper presents an automated methodology
for computer-aided peptide design based on evolutionary algorithms. It provides an automatic tool for peptide de novo design,
based on protein surface patches defined by user. Regarding the restrictive constrains of this problem a special emphasis has been made on the design of the
evolutionary algorithms implemented. 相似文献
35.
36.
Given a graph G=(V,E) and a positive integer D , we consider the problem of finding a minimum number of new edges E' such that the augmented graph G'=(V,E\cup E') is biconnected and has diameter no greater than D. In this note we show that this problem is NP-hard for all fixed D , by employing a reduction from the DOMINATING SET problem. We prove that the problem remains NP-hard even for forests and
trees, but in this case we present approximation algorithms with worst-case bounds 3 (for even D ) and 6 (for odd D ). A closely related problem of finding a minimum number of edges such that the augmented graph has diameter no greater than
D has been shown to be NP-hard by Schoone et al. [21] when D=3 , and by Li et al. [17] when D=2.
Received April 19, 1999; revised June 5, 2001. 相似文献
37.
Timothy Thomasma Kurt Hilbrecht 《International Journal of Flexible Manufacturing Systems》1991,3(3-4):231-250
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
38.
A. Kaveh H. A. Rahimi Bondarabady 《International journal for numerical methods in engineering》2004,60(11):1803-1815
This paper presents an algorithm for nodal numbering in order to obtain a small wavefront. Element clique graphs are employed as the mathematical models of finite element meshes. A priority function containing five vectors is used, which can be viewed as a generalization of Sloan's function. These vectors represent different connectivity properties of the graph models. Unlike Sloan's algorithm, which uses two fixed coefficients, here, five coefficients are employed, based on an evaluation by artificial neural networks. The networks weights are obtained using a simple genetic algorithm. Examples are included to illustrate the performance of the present hybrid method. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
39.
通过建立三维有限元模型,对土钉支护的变形和受力性能进行分析,得出土钉力的合理分布。在此基础上,考虑土钉支护的水平位移,采用遗传算法,对土钉支护的结构优化设计进行研究,建立了土钉支护结构的优化设计数学模型,并编制了相应的计算程序。通过算例分析,并与基于极限平衡分析的优化结果相比较,得出合理的土钉支护结构设计的参考结论。 相似文献
40.
天然气管网输配气量优化研究 总被引:2,自引:0,他引:2
天然气管网系统管理部门为了明确天然气管网的输气能力和提高天然气管网的利用率,需要对天然气管网系统的输配气量进行优化。为此,以天然气管网系统的最大流量为目标函数,同时考虑了管道强度、节点压力和流量限制等约束条件,建立了天然气管网输配气量优化的数学模型。在研究遗传算法和模拟退火算法的基础上,提出了一种由二者结合构成的具有全域搜索、快速收敛和鲁棒性强等特点的混合遗传算法。结合实例,采用这一新算法求解了天然气管网输配气量优化的数学模型。实例优化结果表明,所建立的数学模型和采用的混合遗传算法是可行和有效的,能够对天然气管网系统输配气量的调度运行起到指导作用。 相似文献