全文获取类型
收费全文 | 164655篇 |
免费 | 16705篇 |
国内免费 | 10384篇 |
专业分类
电工技术 | 12932篇 |
技术理论 | 2篇 |
综合类 | 21268篇 |
化学工业 | 16849篇 |
金属工艺 | 7782篇 |
机械仪表 | 13971篇 |
建筑科学 | 22262篇 |
矿业工程 | 7313篇 |
能源动力 | 5366篇 |
轻工业 | 7760篇 |
水利工程 | 7327篇 |
石油天然气 | 6979篇 |
武器工业 | 2355篇 |
无线电 | 10773篇 |
一般工业技术 | 21814篇 |
冶金工业 | 5801篇 |
原子能技术 | 2393篇 |
自动化技术 | 18797篇 |
出版年
2024年 | 589篇 |
2023年 | 1836篇 |
2022年 | 3687篇 |
2021年 | 4380篇 |
2020年 | 4899篇 |
2019年 | 4195篇 |
2018年 | 4057篇 |
2017年 | 5199篇 |
2016年 | 5790篇 |
2015年 | 6122篇 |
2014年 | 10104篇 |
2013年 | 9562篇 |
2012年 | 13003篇 |
2011年 | 13099篇 |
2010年 | 10174篇 |
2009年 | 10465篇 |
2008年 | 9586篇 |
2007年 | 11904篇 |
2006年 | 10420篇 |
2005年 | 8645篇 |
2004年 | 7058篇 |
2003年 | 6073篇 |
2002年 | 5027篇 |
2001年 | 4207篇 |
2000年 | 3744篇 |
1999年 | 3236篇 |
1998年 | 2536篇 |
1997年 | 2257篇 |
1996年 | 1898篇 |
1995年 | 1675篇 |
1994年 | 1383篇 |
1993年 | 1027篇 |
1992年 | 900篇 |
1991年 | 636篇 |
1990年 | 530篇 |
1989年 | 514篇 |
1988年 | 370篇 |
1987年 | 210篇 |
1986年 | 168篇 |
1985年 | 82篇 |
1984年 | 83篇 |
1983年 | 41篇 |
1982年 | 51篇 |
1981年 | 63篇 |
1980年 | 45篇 |
1979年 | 41篇 |
1978年 | 20篇 |
1977年 | 15篇 |
1975年 | 16篇 |
1959年 | 33篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Ali Maghami Dominik Schillinger 《International journal for numerical methods in engineering》2020,121(5):967-989
We explore a truncation error criterion to steer adaptive step length refinement and coarsening in incremental-iterative path following procedures, applied to problems in large-deformation structural mechanics. Elaborating on ideas proposed by Bergan and collaborators in the 1970s, we first describe an easily computable scalar stiffness parameter whose sign and rate of change provide reliable information on the local behavior and complexity of the equilibrium path. We then derive a simple scaling law that adaptively adjusts the length of the next step based on the rate of change of the stiffness parameter at previous points on the path. We show that this scaling is equivalent to keeping a local truncation error constant in each step. We demonstrate with numerical examples that our adaptive method follows a path with a significantly reduced number of points compared to an analysis with uniform step length of the same fidelity level. A comparison with Abaqus illustrates that the truncation error criterion effectively concentrates points around the smallest-scale features of the path, which is generally not possible with automatic incrementation solely based on local convergence properties. 相似文献
42.
43.
44.
本文基于横向积分离散纵标方程,解析得到横向积分通量中出射通量与入射通量的关系,并根据类似于扩散方程节块展开法的输运节块中子平衡方程形式,得到了一种高效的节块离散纵标法数值迭代策略。数值结果表明,本文提出的方法可行且数值结果正确。此外,粗网有限差分(CMFD)加速技术在节块离散纵标法中也取得了非常好的应用效果。 相似文献
45.
46.
对射频电缆幅相稳定性进行了介绍,阐述了射频测试电缆相位和幅度变化的因素,并详细分析了射频电缆相位性能以及幅度性能的不同测试方法,最后通过实测数据的展示,总结说明了在日常测试中该如何正确使用测试电缆。 相似文献
47.
Mohammed Heyouni Farid Saberi-Movahed Azita Tajaddini 《Computers & Mathematics with Applications》2019,77(1):77-92
In the first part of this paper, we investigate the use of Hessenberg-based methods for solving the Sylvester matrix equation . To achieve this goal, the Sylvester form of the global generalized Hessenberg process is presented. Using this process, different methods based on a Petrov–Galerkin or on a minimal norm condition are derived. In the second part, we focus on the SGl-CMRH method which is based on the Sylvester form of the Hessenberg process with pivoting strategy combined with a minimal norm condition. In order to accelerate the SGl-CMRH method, a preconditioned framework of this method is also considered. It includes both fixed and flexible variants of the SGl-CMRH method. Moreover, the connection between the flexible preconditioned SGl-CMRH method and the fixed one is studied and some upper bounds for the residual norm are obtained. In particular, application of the obtained theoretical results is investigated for the special case of solving linear systems of equations with several right-hand sides. Finally, some numerical experiments are given in order to evaluate the effectiveness of the proposed methods. 相似文献
48.
The performance of surface ionic conduction single chamber fuel cell (SIC‐SCFC) prepared by the sol gel method was studied on electric characteristics due to the differences of the operating temperature and humidity, the electrode distance and electrolyte film depth, and multiple cells with the series and parallel connections. The SIC–SCFC was arranged the both anode of Pt and cathode of Au on the boehmite electrolyte. The open circuit voltage (OCV) of single cell achieved a maximum of 530mV in the dry gas mixtures of O2/H2=50% in room temperature operation, and but it became decrease as over 60%. The OCV was maintained the constant value between operating temperatures of 30°C to 80°C, and but it was decreased sharply at over 90°C because a humidity on the cell became lower as increasing operating temperature. Then, the cell property was improved to 120°C by adding to the humidity of 70% using a humidifier. The electrode distance and the electrolyte film depth of SIC‐SCFC found to be contributed to the reductions of the cell resistance and the surface roughness on the electrode, respectively. Moreover, the power property of SIC‐SCFC was significantly improved by cell stacks comprised of the series or parallel connection of a cell. 相似文献
49.
面向草莓抓取的气动四叶片软体抓手研制 总被引:1,自引:0,他引:1
农林业中果蔬的自动化采摘需求日趋强烈,末端抓手是实现无损采摘的关键。传统的末端抓手以刚性结构居多,现有的各种柔性抓手也存在抓取力不足、包覆性不佳等缺点。本文以草莓的无损采摘为研究对象,提出将草莓外部轮廓曲线作为设计曲线,设计了一种新型气动四叶片软体抓手。首先,对软体抓手的结构做仿真优化,提出一种安全地附着在目标物表面的设想。然后,在进行草莓表面的最小破坏应力试验的基础上,测试了软体抓手的末端力,验证了其实现无损抓取的可行性。再次,利用动态捕捉技术,研究了软体抓手叶面的弯曲变形规律。最后,选择使用弧线型气体通道的软体抓手进行了草莓抓取测试,结果证明了气动四叶片软体抓手可以实现草莓的无损抓取,抓取成功率达90%,破损率为2%,表明所研制的四叶片软体抓手用于草莓抓取时具有良好的稳定性和实用性,可用于草莓采摘的末端执行器。本研究也可为其他易损果蔬的采摘技术提供理论基础和技术支撑。 相似文献
50.
The capture of particles by charged droplets was simulated by considering the electrostatic interactions of droplet-droplet and droplet-particle. The results indicate that the electrostatic repulsion between droplets leads to a dynamic accumulation mode of particles. However, the droplet spacing has an insignificant effect on the capture efficiency when the electrostatic deposition predominates. The increase of droplet charge remarkably improves the capture efficiency, in which the capture of fine particles accounts for the largest proportion. Compared to the droplet charge, the droplet size shows a limited improvement in the capture efficiency. Reducing the droplet velocity prolongs the capture time instead of enhancing the capture capacity per unit time, thereby improving capture efficiency. 相似文献