全文获取类型
收费全文 | 2908篇 |
免费 | 376篇 |
国内免费 | 167篇 |
专业分类
化学 | 278篇 |
晶体学 | 35篇 |
力学 | 1579篇 |
综合类 | 51篇 |
数学 | 491篇 |
物理学 | 1017篇 |
出版年
2024年 | 11篇 |
2023年 | 21篇 |
2022年 | 31篇 |
2021年 | 47篇 |
2020年 | 75篇 |
2019年 | 51篇 |
2018年 | 67篇 |
2017年 | 81篇 |
2016年 | 102篇 |
2015年 | 53篇 |
2014年 | 121篇 |
2013年 | 247篇 |
2012年 | 149篇 |
2011年 | 124篇 |
2010年 | 108篇 |
2009年 | 138篇 |
2008年 | 164篇 |
2007年 | 180篇 |
2006年 | 196篇 |
2005年 | 170篇 |
2004年 | 139篇 |
2003年 | 145篇 |
2002年 | 96篇 |
2001年 | 94篇 |
2000年 | 92篇 |
1999年 | 108篇 |
1998年 | 82篇 |
1997年 | 86篇 |
1996年 | 75篇 |
1995年 | 65篇 |
1994年 | 44篇 |
1993年 | 30篇 |
1992年 | 51篇 |
1991年 | 48篇 |
1990年 | 22篇 |
1989年 | 12篇 |
1988年 | 27篇 |
1987年 | 20篇 |
1986年 | 20篇 |
1985年 | 15篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 10篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1971年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有3451条查询结果,搜索用时 421 毫秒
191.
回顾了实心弹性薄板优化研究的发展历程。给出了由无限密和无限细的肋骨加强的环板在常肋骨密度时的解析解;采用精确刚度阵的有限元法计算了具有有限根肋骨加强的板的柔顺性,它低于光滑优化解的柔顺性。这些结果进一步说明近期文献中出现的枕头形的光滑解并不是几何受约束实心弹性薄板优化问题的全局最优解。 相似文献
192.
井眼轨迹控制力学模型 总被引:8,自引:0,他引:8
对石油钻井中井眼轨迹控制问题进行了力学分析,给出了底部钻具组合三维受力和变形的控制方程,建立了钻头与正交各向异性地层相互作用模型,阐明了井眼轨迹预测和控制计算方法。 相似文献
193.
194.
The stability and vibration of an elastic rod with a circular cross section under the constraint of a cylinder is discussed.
The differential equations of dynamics of the constrained rod are established with Euler’s angles as variables describing
the attitude of the cross section. The existence conditions of helical equilibrium under constraint are discussed as a special
configuration of the rod. The stability of the helical equilibrium is discussed in the realms of statics and dynamics, respectively.
Necessary conditions for the stability of helical rod are derived in space domain and time domain, and the difference and
relationship between Lyapunov’s and Euler’s stability concepts are discussed. The free frequency of flexural vibration of
the helical rod with cylinder constraint is obtained in analytical form.
The project supported by the National Natural Science Foundation of China (10472067). The English text was polished by Yunming
Chen. 相似文献
195.
In this paper a new modelling method, called the tolerance averaging method, is presented and applied to analyse a buckling of thin periodic plates resting on a periodically heterogeneous Winkler foundation. The derived length-scale model makes it possible to take into account the effect of periodicity cell size (the length-scale effect) on the overall plate behaviour, on the contrary to the known homogenised models of periodic plates neglecting this effect. In order to evaluate obtained results the buckling problems of those plates are analysed using not only the proposed model but also a certain effective stiffnesses model. A comparison between obtained results leads to a conclusion that the length-scale effect could not be neglected in buckling of periodic plates resting on a Winkler foundation. 相似文献
196.
土工聚合物减小土体差异沉降的机理及最佳埋置深度的计算 总被引:3,自引:1,他引:3
以弹性理论为基础,分析讨论了利用土工聚合物减小土体差异沉降的机理和土工聚合物最佳埋置深度的确定方法. 相似文献
197.
非线性粘弹性拟静态问题与非线性弹性静力问题对应原理 总被引:7,自引:0,他引:7
本文应用多重单边拉氏变换导出了非线性粘弹性拟静态问题与非线性弹性静力问题的对应关系,从而把过去认为只有线性条件下存在的粘弹性——弹性对应原理拓展到了非线性范畴 相似文献
198.
In this paper, based on the theory of multiple scattering of elastic waves, employing wave functions expansion method, multiple scattering and strain energy density in semi-infinite functional graded materials with a circular cavity are investigated, the analytical solution of the problem is derived, and the numerical solution of the strain energy density factors around the cavity is also presented. The effects of the distance between the cavity and the edge of the materials, the wave number and the non-homogeneous parameter of materials on strain energy density factors are analyzed. From analysis, it can be seen that when the non-homogeneous parameter of materials is less than zero, it has less influence on the maximum strain energy density factor around the cavity; however, it has greater influence on the distribution of strain energy density factors around the cavity. When the non-homogeneous parameter of materials is greater than zero, it has greater influence on both the maximum strain energy density factor and the distribution of strain energy density factor around the cavity, especially in the case that the distance between the cavity and the edge is comparatively little. 相似文献
199.
200.
BENDING SOLUTION OF A RECTANGULAR PLATE WITH ONE EDGE BUILT-IN AND ONE CORNER POINT SUPPORTED SUBJECTED TO UNIFORM LOAD 总被引:3,自引:0,他引:3
BENDING SOLUTION OF A RECTANGULAR PLATE WITH ONE EDGE BUILT-IN AND ONE CORNER POINT SUPPORTED SUBJECTED TO UNIFORM LOADXuQilo... 相似文献