全文获取类型
收费全文 | 53336篇 |
免费 | 5338篇 |
国内免费 | 3208篇 |
专业分类
电工技术 | 3561篇 |
技术理论 | 1篇 |
综合类 | 6689篇 |
化学工业 | 2843篇 |
金属工艺 | 4919篇 |
机械仪表 | 7530篇 |
建筑科学 | 7944篇 |
矿业工程 | 2143篇 |
能源动力 | 1500篇 |
轻工业 | 1171篇 |
水利工程 | 1979篇 |
石油天然气 | 2174篇 |
武器工业 | 754篇 |
无线电 | 2580篇 |
一般工业技术 | 9963篇 |
冶金工业 | 2095篇 |
原子能技术 | 534篇 |
自动化技术 | 3502篇 |
出版年
2024年 | 97篇 |
2023年 | 584篇 |
2022年 | 1095篇 |
2021年 | 1383篇 |
2020年 | 1439篇 |
2019年 | 1247篇 |
2018年 | 1248篇 |
2017年 | 1640篇 |
2016年 | 1830篇 |
2015年 | 2113篇 |
2014年 | 3119篇 |
2013年 | 3116篇 |
2012年 | 4072篇 |
2011年 | 4439篇 |
2010年 | 3289篇 |
2009年 | 3506篇 |
2008年 | 3262篇 |
2007年 | 4005篇 |
2006年 | 3486篇 |
2005年 | 2839篇 |
2004年 | 2373篇 |
2003年 | 1986篇 |
2002年 | 1639篇 |
2001年 | 1328篇 |
2000年 | 1226篇 |
1999年 | 1012篇 |
1998年 | 812篇 |
1997年 | 726篇 |
1996年 | 593篇 |
1995年 | 557篇 |
1994年 | 436篇 |
1993年 | 312篇 |
1992年 | 274篇 |
1991年 | 184篇 |
1990年 | 179篇 |
1989年 | 139篇 |
1988年 | 99篇 |
1987年 | 61篇 |
1986年 | 34篇 |
1985年 | 20篇 |
1984年 | 16篇 |
1983年 | 7篇 |
1982年 | 14篇 |
1981年 | 11篇 |
1980年 | 12篇 |
1979年 | 8篇 |
1972年 | 2篇 |
1959年 | 3篇 |
1957年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
PENGLiming MAOXiemin XUKuangdi DINGWenjiang 《稀有金属(英文版)》2002,21(1):62-66
In order to develop a new type of contact cable with high strength and high electrical conductivity, Cu-Cr alloy series were selected as materials and Cu-Cr alloy castings were produced by means of directional solidification continuous casting (DSCC) process. The results show that the fibrillar strengthening phase, 13-Cr, orderly arranges among the copper matrix phase along the wire direction; and a microstructure of in-situ composite forms, which retains the basic property of good conductivity of the copper matrix and meanwhile obtains the strengthening effect of [3-Cr phase. The production technology as well as the mechanical property, electrical property, and synthetic property of the in-situ composite contact cables was discussed. 相似文献
92.
研究了用光漂白的方法制备PMMA/DR1聚合物非线性定向耦合器,提出了一种容易的制备方法来得到要求的耦合长度.测量了材料的光学非线性对定向耦合器两臂透过率的影响.实验结果表明由于光学非线性,耦合器的耦合长度随着入射光强度的改变而发生变化. 相似文献
93.
94.
大长径比自旋弹箭横向自振特性的有限元计算方法与结果分析 总被引:2,自引:0,他引:2
本文研究大长径比自旋弹箭在飞行时横向振动的自振特性。本文将转子动力学应用于弹道学 ,采用有限元法 ,建立自旋弹箭横向振动自振特性方程。同时给出了计算方法。利用该方程和该方法 ,开发了相应的计算程序。通过数值计算 ,可给出细长旋转弹箭飞行时的进动转速和临界转速 ,以及相应的位移和角度振型。利用该程序 ,进行了实例计算和分析。 相似文献
95.
Gyeong-Ho Kim 《Computer Methods in Applied Mechanics and Engineering》2008,198(2):234-244
A continuum-based modeling of coupled electrostatics-structure interactions is presented for the frequency computations of MEMS devices. The present general formulation of electrostatics accounting for free space is validated first by specializing it to one-dimensional uniform motion of conducting surfaces and comparing the resulting electrostatics to conventional lumped models. The general coupled electrostatics-structure interactions are then applied for the prediction of resonant frequencies of MEMS devices due to bias-voltage changes and temperature variations. Comparisons of predicted resonant frequencies obtained by the present coupled electrostatics-structure interaction models with experimental results available in the literature demonstrate that the proposed continuum-based interaction modeling yields high-confidence predictions of resonant frequencies of MEMS devices. 相似文献
96.
温度场有限元分析的接缝单元 总被引:2,自引:2,他引:0
目前混凝土坝的仿真分析正从单坝段仿真向全坝仿真发展,因而需要采用接缝单元,笔者给出三种温度场接缝单元的计算模型:有限厚度接缝单元、近零厚度接缝单元及简化接缝单元. 相似文献
97.
阐述了仿真环境中的网络攻击模型的设计,建立了一个网络攻击仿真模型,用以产生网络攻击,以达到摧毁网络的机密性、完整性和可用性的目的;采用知识表达的方法来建立模型,该模型包含具有知识库和推理机的专家系统,通过随时间而变化的量,使模型具有基于仿真时钟的推理能力;在攻击模型的设计中,定义了它的基本状态和状态跃迁函数,说明了模型的行为,以及攻击策略的制定,最佳策略的选择,攻击选择原则等问题。 相似文献
98.
A comparative study of numerical solutions to non-linear discrete crack modelling of concrete beams involving sharp snap-back 总被引:1,自引:0,他引:1
Numerical problems are often encountered in modelling crack propagation in concrete beams using non-linear finite element (FE) analysis, especially when sharp snap-back behaviour in load-displacement relations occurs. This paper firstly identifies 16 arc-length control based numerical strategies based on extensive literature review. They are then used to carefully model the structural behaviour of a four-point single notched shear beam using discrete crack modelling approach in which cracks are represented by interface elements with bilinear softening constitutive laws. Based on extensive FE analyses, detailed comparisons of the merits and demerits of these numerical algorithms are then made. The results indicate that the effectiveness and efficiency of different algorithms may vary considerably from one to another, with the local arc-length based procedures in conjunction with tangential stiffness strategy and reversible unloading model being the most robust. 相似文献
99.
Dongchang Sun Liyong Tong 《International journal for numerical methods in engineering》2004,60(11):1911-1932
A novel finite element model is presented for static and dynamic analysis of composite plates integrated with a laminated piezoelectric layer, a host laminated composite plate and an adhesive layer between them. A new adhesive element is developed which includes both peel and shear effects in the adhesive layer based on first‐order shear deformation plate theory. The thin adhesive layer between the piezoelectric layer and the host plate is modelled by assuming that it carries constant shear and peel strains throughout its thickness. In addition, a weighted static shape control scheme for finding the optimal voltage distribution for static shape control is given. By selecting different weighting matrices, a variety of items such as displacements, slopes, curvatures, strains and even generalized forces, can be included in finding the optimal actuating voltage for static shape control. The present model is validated by comparing with those results available in the literature. The numerical results show that the weighted linear least method can give a satisfactory voltage distribution to best match the desired shape. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
100.