全文获取类型
收费全文 | 183616篇 |
免费 | 18241篇 |
国内免费 | 10350篇 |
专业分类
电工技术 | 15065篇 |
技术理论 | 8篇 |
综合类 | 18846篇 |
化学工业 | 19249篇 |
金属工艺 | 7534篇 |
机械仪表 | 16621篇 |
建筑科学 | 20439篇 |
矿业工程 | 6820篇 |
能源动力 | 8417篇 |
轻工业 | 12913篇 |
水利工程 | 7612篇 |
石油天然气 | 8646篇 |
武器工业 | 2331篇 |
无线电 | 11102篇 |
一般工业技术 | 17972篇 |
冶金工业 | 6928篇 |
原子能技术 | 2603篇 |
自动化技术 | 29101篇 |
出版年
2024年 | 655篇 |
2023年 | 2226篇 |
2022年 | 4582篇 |
2021年 | 5486篇 |
2020年 | 5691篇 |
2019年 | 4788篇 |
2018年 | 4618篇 |
2017年 | 5734篇 |
2016年 | 6895篇 |
2015年 | 7299篇 |
2014年 | 11744篇 |
2013年 | 11879篇 |
2012年 | 13797篇 |
2011年 | 15247篇 |
2010年 | 10909篇 |
2009年 | 11165篇 |
2008年 | 10394篇 |
2007年 | 12478篇 |
2006年 | 10804篇 |
2005年 | 9049篇 |
2004年 | 7634篇 |
2003年 | 6569篇 |
2002年 | 5322篇 |
2001年 | 4352篇 |
2000年 | 3760篇 |
1999年 | 3098篇 |
1998年 | 2685篇 |
1997年 | 2259篇 |
1996年 | 1866篇 |
1995年 | 1531篇 |
1994年 | 1389篇 |
1993年 | 1015篇 |
1992年 | 959篇 |
1991年 | 697篇 |
1990年 | 584篇 |
1989年 | 498篇 |
1988年 | 408篇 |
1987年 | 286篇 |
1986年 | 241篇 |
1985年 | 227篇 |
1984年 | 271篇 |
1983年 | 251篇 |
1982年 | 207篇 |
1981年 | 101篇 |
1980年 | 96篇 |
1979年 | 66篇 |
1978年 | 55篇 |
1977年 | 48篇 |
1976年 | 43篇 |
1959年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
全金属反射光学系统结构的有限元分析 总被引:3,自引:1,他引:2
用有限元分析方法对全金属反射光学系统在各种受力状态下的变形、应力及固有频率做了全面的分析,并给出了结构多次优化后的分析结果。 相似文献
952.
953.
本文介绍应力分析设计法的原理,通过有限元计算得到汽包封头的温度场、应力场,并以应力分析为基础对汽包封头强度作了校核。 相似文献
954.
提高大口径金属主镜面形精度的方法 总被引:1,自引:1,他引:0
分析了影响Ritchey-Chreitien光学系统中金属主反射镜面形精度因素,采用有限元法对立交易的加工过程及其安装进行了模拟,指出提高主镜的面形镜度,既要合理主镜材料的热处理工艺,也要对加工参数进行控制。良好的稳定化处理可以有效地消除材料内部的残余应力,保证主镜尺寸的稳定性。提高加工基准的精度,并采用组合加工镜面,可以大大提高主镜的面形精度,最后,给出了主镜的干涉仪检测结果。 相似文献
955.
956.
通过对故县水库水文特征分析,论述了水库开发任务和要求。并根据水库的洪水、径流、泥沙特性,拟定了水库防洪运用的控制条件和运用方式,以及水库的兴利运用水位和原则。对水库工程的投资和效益作出了分析和评价。 相似文献
957.
The strip element method (SEM) is used to investigate wave scattering by rectangular flaws in anisotropic laminated plates. The plates containing flaws are divided by junctions into domains in which the SEM is applied. For each domain, SEM equations are obtained which give a relationship between the traction and displacement vector on the vertical boundaries. A set of equations which gives a relationship between the traction and displacement vector on the junctions is then obtained by assembling the SEM equations for all the domains. This set of equations is solved by using the conditions on the junctions. Scattered wave fields in the frequency domain for isotropic and composite plates with rectangular flaws are computed and discussed in comparison with results for corresponding plates without flaws. A technique for determining the length of a rectangular flaw in a plate is also presented. The results presented in this paper are of importance and could be used in the characterization of flaws in anisotropic laminated plates. 相似文献
958.
使用有限元程序SAP5对某新型导弹发射筒内的适配器的强度进行了计算。通过结果分析,找出了适配器危险应力点的分布规律,它对结构选型设计具有指导意义。 相似文献
959.
《International Journal of Pressure Vessels and Piping》1996,66(1-3):187-198
The limit carrying capacity of gas pipelines having corrosion defects were evaluated by means of an improved FEM analysis, together with the ANSI/ASME defect judgement and an experimental verification. When compared with our past presentation at the proceedings of the CAPE'93 Colloquium (dealing with reproduced defects), this paper evaluates the remaining lifetime of a pipeline having natural faults. The new improved analysis includes geometrical nonlinearities leading to a modification of limit state parameters and thus matching better with actuality. This presented work was initiated by the firm of Trans-Gas in Prague after having had a pipeline inspected proving some parts of it as being heavily corroded. The task in hand was to determine the remaining pipeline lifetime with the view to at least a two-year period. 相似文献
960.
S. R. Reid T. X. Yu J. L. Yang G. G. Corbett 《International Journal of Impact Engineering》1996,18(7-8)
This paper is concerned with the problem of pipe whip, the dynamic response of a high pressure piping system subjected to an end force as the result of a pipe break which releases a jet of fluid from the broken section. Both experimental and theoretical results are presented concerning the dynamic elastic-plastic behaviour of cantilever pipes subjected to a transverse force pulse at the free end. Comparisons between experimental data and theoretical predictions are made for mild-steel pipes with outer diameter-to-thickness ratios of 19.5, 28 and 32. It is demonstrated that, for these geometries, the whipping pipes display three characteristically different responses, viz. elastic, plastic hardening behaviour for thick pipes, elastic, plastic hardening-softening behaviour for moderately thick pipes and elastic, plastic hardening-softening-collapse behaviour for thinner pipes. The experimental data taken from a series of high-speed films are compared with the predictions of the instantaneous shapes of the whipping pipes derived from both a rigid, perfectly-plastic, large deflection, dynamic beam model and a more comprehensive model which incorporates the effects of elasticity and plastic hardening and softening, the details of which are presented in the paper. 相似文献