全文获取类型
收费全文 | 28528篇 |
免费 | 3042篇 |
国内免费 | 2447篇 |
专业分类
电工技术 | 1646篇 |
技术理论 | 1篇 |
综合类 | 4050篇 |
化学工业 | 1665篇 |
金属工艺 | 435篇 |
机械仪表 | 1366篇 |
建筑科学 | 2301篇 |
矿业工程 | 621篇 |
能源动力 | 627篇 |
轻工业 | 976篇 |
水利工程 | 739篇 |
石油天然气 | 763篇 |
武器工业 | 290篇 |
无线电 | 3387篇 |
一般工业技术 | 2932篇 |
冶金工业 | 1426篇 |
原子能技术 | 151篇 |
自动化技术 | 10641篇 |
出版年
2024年 | 114篇 |
2023年 | 317篇 |
2022年 | 620篇 |
2021年 | 735篇 |
2020年 | 842篇 |
2019年 | 831篇 |
2018年 | 771篇 |
2017年 | 916篇 |
2016年 | 1114篇 |
2015年 | 1188篇 |
2014年 | 1858篇 |
2013年 | 2005篇 |
2012年 | 2148篇 |
2011年 | 2116篇 |
2010年 | 1652篇 |
2009年 | 1852篇 |
2008年 | 1879篇 |
2007年 | 2040篇 |
2006年 | 1751篇 |
2005年 | 1526篇 |
2004年 | 1196篇 |
2003年 | 1083篇 |
2002年 | 863篇 |
2001年 | 832篇 |
2000年 | 676篇 |
1999年 | 551篇 |
1998年 | 397篇 |
1997年 | 312篇 |
1996年 | 271篇 |
1995年 | 259篇 |
1994年 | 200篇 |
1993年 | 168篇 |
1992年 | 145篇 |
1991年 | 117篇 |
1990年 | 114篇 |
1989年 | 106篇 |
1988年 | 81篇 |
1987年 | 47篇 |
1986年 | 28篇 |
1985年 | 28篇 |
1984年 | 19篇 |
1983年 | 21篇 |
1982年 | 17篇 |
1981年 | 17篇 |
1980年 | 13篇 |
1964年 | 16篇 |
1963年 | 16篇 |
1961年 | 15篇 |
1959年 | 17篇 |
1955年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Chouping Luo Marek Klisinski 《International journal for numerical methods in engineering》2004,61(2):159-188
The present study is a continuation of our previous work with the aim to reduce problems caused by standard higher order elements in contact problems. The difficulties can be attributed to the inherent property of the Galerkin method which gives uneven distributions of nodal forces resulting in oscillating contact pressures. The proposed remedy is use of piece‐wise linear weight functions. The methods to establish stiffness and/or mass matrix for 8‐node quadrilateral element in 2D are presented, i.e. the condensing and direct procedures. The energy and nodal displacement error norms are also checked to establish the convergence ratio. Interpretation of calculated contact pressures is discussed. Two new 2D 8‐node quadrilateral elements, QUAD8C and QUAD8D, are derived and tested in many examples, which show their good performance in contact problems. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
12.
陈继初 《湖南冶金职业技术学院学报》2003,(4)
会计政策选择类型在理论上大体可分为机会主义型和效率(或有效契约)型。会计政策选择具有效率性,但也为经理人员的机会主义行为打开了大门。在我国,由于企业缺乏一系列有效的激励约束机制,会计政策选择的机会主义仍然严重。为此,必须建立适合我国企业有效的激励约束机制。 相似文献
13.
This paper deals with the time-optimal control problem for a class of control systems which includes controlled mechanical systems with possible dissipation terms. The Lie algebras associated with such mechanical systems have certain special properties. These properties are explored and used in conjunction with the Pontryagin maximum principle to determine the structure of singular extremals and, in particular, time-optimal trajectories. The theory is illustrated by an application to a time-optimal problem for a class of underwater vehicles. 相似文献
14.
Curry I. Guinn 《Knowledge》1994,7(4):277-278
Collaboration is more efficient when the most capable participant for each goal has initiative in directing the problem-solving for that goal. The paper describes a method for using a probabilistic analysis to create a mode-switching mechanism that selects which participant should control the collaborative problem solving so that efficiency is maximized. 相似文献
15.
针对铜鼓县小水电站联网时存在的问题及其不利影响进行了分析,井提出了改进途径,指出小水电站的联网改造应立足安全,争取效益。 相似文献
16.
This paper formulates the pickup and delivery problem, also known as the dial-a-ride problem, as an integer program. Its polyhedral structure is explored and four classes of valid inequalities developed. The results of a branch-and-cut algorithm based on these constraints are presented. 相似文献
17.
Ye. L. Stolov 《Journal of Electronic Testing》1993,4(3):283-283
Let a circuit havem outputs,m>1. There are two ways to test this circuit by means of a signature analyzer: use a single input analyzer for each output or use anm-input analyzer to test all outputs simultaneously. The main goal of this letter is to demonstrate that for fault output sequences with small multiplicity of errors and long length the second approach is more effective. 相似文献
18.
We study the application of the geographic nearest neighbor approach to two problems. The first problem is the construction of an approximately minimum length rectilinear Steiner tree for a set ofn points in the plane. For this problem, we introduce a variation of a subgraph of sizeO(n) used by YaO [31] for constructing minimum spanning trees. Using this subgraph, we improve the running times of the heuristics discussed by Bern [6] fromO(n
2
log
n) toO(n log2
n). The second problem is the construction of a rectilinear minimum spanning tree for a set ofn noncrossing line segments in the plane. We present an optimalO(n logn) algorithm for this problem. The rectilinear minimum spanning tree for a set of points can thus be computed optimally without using the Voronoi diagram. This algorithm can also be extended to obtain a rectilinear minimum spanning tree for a set of nonintersecting simple polygons.The results in this paper are a part of Y. C. Yee's Ph.D. thesis done at SUNY at Albany. He was supported in part by NSF Grants IRI-8703430 and CCR-8805782. S. S. Ravi was supported in part by NSF Grants DCI-86-03318 and CCR-89-05296. 相似文献
19.
陈金强 《数字社区&智能家居》2007,(9):1460-1461
中等职业学校一般开设VB、VC及数据库等涉及程序设计的计算机课程。本文拟就程序设计中一题多解的教学方法进行探讨。 相似文献
20.
Mulcahy Nicholas J.; Call Josep; Dunbar Robin I. M. 《Canadian Metallurgical Quarterly》2005,119(1):23
Two important elements in problem solving are the abilities to encode relevant task features and to combine multiple actions to achieve the goal. The authors investigated these 2 elements in a task in which gorillas (Gorilla gorilla) and orangutans (Pongo pygmaeus) had to use a tool to retrieve an out-of-reach reward. Subjects were able to select tools of an appropriate length to reach the reward even when the position of the reward and tools were not simultaneously visible. When presented with tools that were too short to retrieve the reward, subjects were more likely to refuse to use them than when tools were the appropriate length. Subjects were proficient at using tools in sequence to retrieve the reward. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献