全文获取类型
收费全文 | 914篇 |
免费 | 26篇 |
国内免费 | 30篇 |
专业分类
化学 | 196篇 |
力学 | 30篇 |
综合类 | 1篇 |
数学 | 502篇 |
物理学 | 241篇 |
出版年
2023年 | 18篇 |
2022年 | 19篇 |
2021年 | 11篇 |
2020年 | 22篇 |
2019年 | 11篇 |
2018年 | 15篇 |
2017年 | 18篇 |
2016年 | 12篇 |
2015年 | 9篇 |
2014年 | 43篇 |
2013年 | 78篇 |
2012年 | 60篇 |
2011年 | 51篇 |
2010年 | 48篇 |
2009年 | 76篇 |
2008年 | 62篇 |
2007年 | 80篇 |
2006年 | 53篇 |
2005年 | 47篇 |
2004年 | 31篇 |
2003年 | 29篇 |
2002年 | 17篇 |
2001年 | 26篇 |
2000年 | 21篇 |
1999年 | 8篇 |
1998年 | 12篇 |
1997年 | 14篇 |
1996年 | 11篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 7篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 9篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有970条查询结果,搜索用时 15 毫秒
81.
换热器性能测试是换热器设计过程中的重要环节,对其结构优化及性能评估具有重要作用。针对传统的换热器性能测试系统存在试验周期长、组合方案少,自动化水平不高、可重用应用性较差等不足,文章基于工业控制计算机和C++ Builder软件平台开发了换热器性能试验测控与仿真系统。该系统实现了试验工况参数的控制与过程仿真、试验数据的采集记录与分析处理等各项操作的自动化。文章在简要介绍换热器性能测试系统硬件设计的基础上,具体结合系统硬件介绍了利用C++ Builder制作的换热器仿真实验测控系统的方法及过程,最后给出换热器性能测试仿真实验用户界面及仿真实验运行结果。试验结果表明,测控系统具有交互界面良好、使用方便,可靠性高等特点,能够较好地满足换热器性能测试的要求。 相似文献
82.
83.
84.
85.
模糊值Choquet积分(Ⅱ)--函数关于模糊值模糊测度的Choquet积分 总被引:2,自引:0,他引:2
研究一种取值于模糊数集的Choquet积分,该积分的被积函数是单值函数,所用的测度是模糊值模糊测度。给出其定义、性质和收敛定理。 相似文献
86.
LiuYuqi LiZhigang YahYakun 《Acta Mechanica Solida Sinica》2004,17(1):58-64
By using the Finite Element Inverse Approach based on the Hill quadratic anisotrop-ically yield criterion and the quadrilateral element, a fast analyzing software-FASTAMP for the sheet metal forming is developed. The blank shapes of three typical stampings are simulated and compared with numerical results given by the AUTOFORM software and experimental results, respectively. The comparison shows that the FASTAMP can predict blank shape and strain distribution of the stamping more precisely and quickly than those given by the traditional methods and the AUTOFORM. 相似文献
87.
Fully and partially observed stochastic control of systems with nonlinear dynamics and terminal and running costs are considered.
Measure changes are introduced which allow both state and observation dynamics to be thought of as linear. In the case when
the terms of the cost have a special form the measure change transformation “cancels out” the nonlinearities and changes the
original nonlinear problem into a classical LQG one and standard results can be applied. We also consider unnormalized conditional
densities of the whole path as state variables and obtain dynamic programming and verification results.
R. J. Elliott wishes to acknowledge support of the Natural Sciences and Engineering Research Council of Canada, Grant A7964. 相似文献
88.
Efficient measurement of the performance index (the distance of a loading parameter from the voltage collapse point) is one of the key problems in power system operations and planning and such an index indicates the severity of a power system with regard to voltage collapse. There exist many interesting methods and ideas to compute this index. However, some successful methods are not yet mathematically justified while other mathematically sound methods are often proposed directly based on the bifurcation theory and they require the initial stationary state to be too close to the unknown turning point to make the underlying methods practical.This paper first gives a survey of several popular methods for estimating the fold bifurcation point including the continuation methods, bifurcation methods and the test function methods (Seydel's direct solution methods, the tangent vector methods and the reduced Jacobian method) and discuss their relative advantages and problems. Test functions are usually based on scaling of the determinant of the Jacobian matrix and it is generally not clear how to determine the behaviour of such functions. As the underlying nonlinear equations are of a particular type, this allows us to do a new analysis of the determinants of the Jacobian and its submatrices in this paper. Following the analysis, we demonstrate how to construct a class of test functions with a predictable analytical behaviour so that a suitable index can be produced. Finally, examples of two test functions from this class are proposed. For several standard IEEE test systems, promising numerical results have been achieved. 相似文献
89.
90.
本文提出使用频移反馈激光系统测量光学频率差的新方法。实验测得一个Nd:YLF激光器输出的两个纵模的频率差为3.733440GHz,其精度为±5kHz. 相似文献