全文获取类型
收费全文 | 8377篇 |
免费 | 972篇 |
国内免费 | 488篇 |
专业分类
电工技术 | 172篇 |
综合类 | 1284篇 |
化学工业 | 490篇 |
金属工艺 | 274篇 |
机械仪表 | 1374篇 |
建筑科学 | 2674篇 |
矿业工程 | 219篇 |
能源动力 | 155篇 |
轻工业 | 192篇 |
水利工程 | 299篇 |
石油天然气 | 314篇 |
武器工业 | 135篇 |
无线电 | 337篇 |
一般工业技术 | 1341篇 |
冶金工业 | 172篇 |
原子能技术 | 19篇 |
自动化技术 | 386篇 |
出版年
2024年 | 47篇 |
2023年 | 111篇 |
2022年 | 272篇 |
2021年 | 355篇 |
2020年 | 303篇 |
2019年 | 261篇 |
2018年 | 274篇 |
2017年 | 329篇 |
2016年 | 421篇 |
2015年 | 381篇 |
2014年 | 524篇 |
2013年 | 535篇 |
2012年 | 600篇 |
2011年 | 681篇 |
2010年 | 504篇 |
2009年 | 486篇 |
2008年 | 454篇 |
2007年 | 561篇 |
2006年 | 451篇 |
2005年 | 374篇 |
2004年 | 282篇 |
2003年 | 239篇 |
2002年 | 198篇 |
2001年 | 205篇 |
2000年 | 176篇 |
1999年 | 133篇 |
1998年 | 131篇 |
1997年 | 106篇 |
1996年 | 99篇 |
1995年 | 81篇 |
1994年 | 37篇 |
1993年 | 45篇 |
1992年 | 43篇 |
1991年 | 29篇 |
1990年 | 27篇 |
1989年 | 13篇 |
1988年 | 17篇 |
1987年 | 12篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 1篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1972年 | 1篇 |
1959年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有9837条查询结果,搜索用时 15 毫秒
11.
G. Ranzi M. A. Bradford B. Uy 《International journal for numerical methods in engineering》2004,61(5):657-672
The use of the conventional semi-analytical stiffness method in finite element analysis, in which interpolation polynomials are used to develop the stiffness relationships, leads to problems of curvature locking when beam-type elements are developed for composite members with partial interaction between the materials of which it is comprised. The curvature locking phenomenon that occurs for composite steel–concrete members is quite well reported, and the general approach to minimizing the undesirable ramifications of curvature locking has been to use higher-order polynomials with increasing numbers of internal nodes. This paper presents an alternate formulation based on a direct stiffness approach rather than starting from pre-defined interpolation polynomials, and which does not possess the undesirable locking characteristics. The formulation is based on a more general approach for a bi-material composite flexural member, whose constituent materials are joined by elastic shear connection so as to provide partial interaction. The stiffness relationships are derived, and these are applied to a simply supported and a continuous steel–concrete composite beam to demonstrate the efficacy of the method, and in particular its ability to model accurately both very flexible and very stiff shear connection that causes difficulties when implemented in competitive semi-analytical algorithms. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
12.
新产品——钢带增强聚乙烯螺旋波纹管 总被引:1,自引:0,他引:1
钢带增强聚乙烯螺旋波纹管是一种创新的埋地排水管,把钢材的高刚度、高强度和聚乙烯的柔韧、耐腐结合在一起,突出的优点是环刚度高和节约原材料. 相似文献
13.
小高层建筑需通过剪力墙开洞(结构开洞)降低侧向刚度,本文对开洞部位以及墙肢和连梁设计提出一些看法,供设计人员参考。 相似文献
14.
New mesogenic homologous series having an azo central linkage was synthesized by fixing a rigid 4-methyl phenyl azo group
to resorcinol moiety. The terminal and lateral phenolic -OH groups were esterified, one by one, with 4-n-alkoxybenzoyl and acetyl group, respectively. All the twelve homologues synthesized exhibit mesomorphism. The methoxy ton-decyloxy andn-hexadecyloxy derivatives exhibit monotropic nematic mesophase whereas,n-dodecyloxy andn-tetradecyloxy derivatives exhibit enantiotropic nematic mesophase. The mesogenic properties of the present series was compared
with those of other structurally related mesogenic series.
Paper presented at the 5th National Seminar on Liquid Crystals, University of Jammu, Jammu, December 1997. 相似文献
15.
Ashraf Ayoub 《Computers & Structures》2003,81(7):411-421
This paper presents an inelastic element for the analysis of beams on foundations. The element is derived from a two-field mixed formulation with independent approximation of forces and displacements. The state determination algorithm for the implementation of the element in a general purpose nonlinear finite element analysis program is presented and its stability characteristics are discussed. Numerical studies are performed to compare the model with the classical displacement formulation. The studies confirm the superiority of the proposed model in describing the inelastic behavior of beams on foundations. 相似文献
16.
Moshe Eisenberger 《International journal for numerical methods in engineering》2003,57(11):1603-1614
This work presents the derivation of the exact dynamic stiffness matrix for a high‐order beam element. The terms are found directly from the solutions of the differential equations that describe the deformations of the cross‐section according to the high‐order theory, which include cubic variation of the axial displacements over the cross‐section of the beam. The model has six degrees of freedom at the two ends, one transverse displacement and two rotations, and the end forces are a shear force and two end moments. Using the dynamic stiffness matrix exact vibration frequencies for beams with various combinations of boundary conditions are tabulated and compared with results from the Bernoulli–Euler and Timoshenko beam models. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
17.
18.
分析恒载效应的有限元方法 总被引:2,自引:0,他引:2
本文在Takabatake关于恒载对梁静、动力影响的研究工作的基础上,导出了梁考虑恒载效应的动力分析有限元公式,提出了荷载影响刚度矩阵的概念。分析了分布和集中两种恒载型式对简支梁和悬臂梁自振特性的影响。计算结果表明,用本文方法与Takabatake应用Galerkin方法和近似闭合解方法的结果吻合良好。同时由于本文采用了矩阵形式,不仅便于编制计算机程序,且使方法有更广泛的适用性和灵活性,可更方便地用于各种不同的构造和边界条件下的实际结构。 相似文献
19.
对异常高压层厚度划分问题的探讨 总被引:4,自引:3,他引:1
通过对喇嘛甸油田800多口聚合物井、更新井的厚度划分及对15口井的异常高压层处理的实例,根据异常高压层在电测曲线上的反映特征,准确地将异常高压层识别出来,并采用本井上下相似层对比法、周围邻井砂体预测分析法、新老标准相结合法等综合分析判断方法,正确地划分异常高压层的厚度,将漏划或少划的厚度补划上。给后续的油层对比、水淹层解释、射孔方案的编制及动态、开发综合方案的调整提供准确的基础数据,并为套管损坏的防治、新钻井的异常高压层厚度解释提供了可借鉴的依据。 相似文献
20.