全文获取类型
收费全文 | 487124篇 |
免费 | 43994篇 |
国内免费 | 27338篇 |
专业分类
电工技术 | 39782篇 |
技术理论 | 66篇 |
综合类 | 60107篇 |
化学工业 | 53171篇 |
金属工艺 | 18658篇 |
机械仪表 | 27812篇 |
建筑科学 | 65121篇 |
矿业工程 | 23869篇 |
能源动力 | 24507篇 |
轻工业 | 27616篇 |
水利工程 | 21931篇 |
石油天然气 | 22468篇 |
武器工业 | 6444篇 |
无线电 | 32576篇 |
一般工业技术 | 44918篇 |
冶金工业 | 24702篇 |
原子能技术 | 6038篇 |
自动化技术 | 58670篇 |
出版年
2024年 | 2001篇 |
2023年 | 5997篇 |
2022年 | 11127篇 |
2021年 | 12909篇 |
2020年 | 14049篇 |
2019年 | 11964篇 |
2018年 | 11228篇 |
2017年 | 13532篇 |
2016年 | 15771篇 |
2015年 | 16740篇 |
2014年 | 29130篇 |
2013年 | 27034篇 |
2012年 | 34360篇 |
2011年 | 36452篇 |
2010年 | 28469篇 |
2009年 | 29449篇 |
2008年 | 27189篇 |
2007年 | 34110篇 |
2006年 | 30889篇 |
2005年 | 26409篇 |
2004年 | 22173篇 |
2003年 | 19518篇 |
2002年 | 16249篇 |
2001年 | 13741篇 |
2000年 | 11712篇 |
1999年 | 9718篇 |
1998年 | 7447篇 |
1997年 | 6497篇 |
1996年 | 5797篇 |
1995年 | 4942篇 |
1994年 | 4339篇 |
1993年 | 3184篇 |
1992年 | 2777篇 |
1991年 | 2104篇 |
1990年 | 1771篇 |
1989年 | 1613篇 |
1988年 | 1251篇 |
1987年 | 822篇 |
1986年 | 646篇 |
1985年 | 516篇 |
1984年 | 483篇 |
1983年 | 349篇 |
1982年 | 334篇 |
1981年 | 254篇 |
1980年 | 200篇 |
1979年 | 175篇 |
1978年 | 99篇 |
1977年 | 97篇 |
1975年 | 76篇 |
1959年 | 78篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Ph. D. Candidate:Chen Xue-fengState Key Laboratory of Offshore Coastal Engineering Dalian University of Technology Dalian China e-mail: cxfeng @ student dlut. edu.cn 《水动力学研究与进展(B辑)》2003,15(6)
The reflection coefficient of perforated caissons and the total horizontal forces acting on them were experimentally and numerically analyzed and discussed when wave propagates normally. To consider the viscosity effect of fluid and nonlinear action of waves on structures, the VOF (Volume Of Fluid) method combined with the k-ε turbulence model was used to simulate the interaction between waves and structures. Governing equations were solved with the finite difference method. Through 2D experimental study in the wave flume, the empirical relationship between the reflection coefficient of perforated caissons and the main affecting factors were obtained from the experimental data using the least square method. Also the correlation between the ratio of the total horizontal force acting on perforated caisson and the force acting on solid caisson and the main affecting factors were regressed from the experimental data. 相似文献
102.
103.
Field Static Load Test on Kao-Ping-Hsi Cable-Stayed Bridge 总被引:1,自引:0,他引:1
Field load testing is an effective method for understanding the behavior and fundamental characteristics of a cable-stayed bridge. This paper presents the results of field static load tests on the Kao-Ping-Hsi cable-stayed bridge, the longest cable-stayed bridge in Taiwan, before it was open to traffic. A total of 40 loading cases, including the unit and distributed bending and torsion loading effects, were conducted to investigate the bridge behavior. The atmospheric temperature effect on the variations of the main girder deflections was also monitored. The results of static load testing include the main girder deflections, the flexural strains of the prestressed concrete girder, and the variations of the cable forces. A three-dimensional finite-element model was developed. The results show that the bridge under the planned load test conditions has linear superposition characteristics and the analytical model shows a very good agreement with the bridge responses. Further discussion of deflection and cable forces of the design specifications for a cable-stayed bridge is also presented. 相似文献
104.
求解二维结构-声耦合问题的一种直接方法 总被引:1,自引:1,他引:0
本文基于传递矩阵法(TMM)和虚拟边界元法(VBEM),提出了一种求解在谐激励作用下二维结构-声耦合问题的直接法。文中对任意形状的二维弹性环建立了一阶非齐次运动微分方程组,便于用齐次扩容精细积分法求解,对于含有任意形状孔穴的无穷域流体介质的Helmholtz外问题,采用复数形式的Burton-Miller型组合层势法建立了虚拟边界元方程,保证了声压在全波数域内存在唯一解。根据叠加原理并结合最小二乘法,提出了一种耦合方程的直接解法,由于该方法不存在迭代过程,因而具有较高的计算精度和效率。文中给出了二个典型弹性环在集中谐激励力作用下声辐射算例,计算结果表明本文方法较通常采用的混合FE/BE法更为有效。 相似文献
105.
热镀锌板(卷)工程设计中的环境保护问题 总被引:1,自引:0,他引:1
对热镀锌板(卷)的生产工艺、主要生产设备进行了简要介绍,并就其污染源(工序)、生产过程中产生的污染物及其控制措施进行了评述,同时就设计和生产中宜注意的几个环保问题进行了分析。 相似文献
106.
107.
108.
109.
A new and original method of calibrating helium leaks that makes it possible to take into account the existence of a number of auxiliary phenomena is described. For this purpose, a hollow leak the purpose of which is to reproduce only desorbed gas flows, is introduced into the vacuum system of the calibration bench. Analysis of the results of corresponding cumulation measurements makes it possible to introduce corrections for these phenomena. 相似文献
110.
A method of measuring and identifying the static parameters of a bipolar transistor is considered. The characteristic of the transistor, from which the parameters of the model are determined, is chosen depending on what group the calculated parameters belong to. The characteristics are measured in such a way that the equations of the model describing them can be reduced to the simplest form. 相似文献