全文获取类型
收费全文 | 669篇 |
免费 | 102篇 |
国内免费 | 74篇 |
专业分类
化学 | 495篇 |
晶体学 | 2篇 |
力学 | 41篇 |
综合类 | 11篇 |
数学 | 28篇 |
物理学 | 268篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 18篇 |
2021年 | 16篇 |
2020年 | 21篇 |
2019年 | 19篇 |
2018年 | 17篇 |
2017年 | 12篇 |
2016年 | 33篇 |
2015年 | 27篇 |
2014年 | 35篇 |
2013年 | 46篇 |
2012年 | 51篇 |
2011年 | 56篇 |
2010年 | 49篇 |
2009年 | 27篇 |
2008年 | 36篇 |
2007年 | 49篇 |
2006年 | 37篇 |
2005年 | 31篇 |
2004年 | 35篇 |
2003年 | 23篇 |
2002年 | 26篇 |
2001年 | 19篇 |
2000年 | 15篇 |
1999年 | 16篇 |
1998年 | 8篇 |
1997年 | 23篇 |
1996年 | 12篇 |
1995年 | 6篇 |
1994年 | 14篇 |
1993年 | 10篇 |
1992年 | 9篇 |
1991年 | 13篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 8篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1973年 | 3篇 |
1971年 | 1篇 |
排序方式: 共有845条查询结果,搜索用时 359 毫秒
1.
利用Riccati变换求解同谐谐振子的定态薛定谔方程,求得了能谱及态函数
关键词:
同调谐振子
本征值谱
Riccati变换法 相似文献
2.
本文介绍一种用牛顿力学研究赛跑运动的物理模型,给出两种情形下跑步时间的最优化结果.这一结果与优秀运动员的实际比赛成绩很好地相符. 相似文献
3.
4.
从立方抛物线谈起(1)--余弦型振动,椭圆余弦型振动与双曲线型非周期运动 总被引:1,自引:1,他引:0
从立方抛物线的特性谈起 ,用较初浅的方法 ,借助于雅可比椭圆函数求椭圆方程的解来说明一大类一维保守系统的余弦振动、椭圆余弦型振动与双曲线型非周期运动 .并以杜芬振子、单摆、倒摆、转动圆环上的小环运动为典型实例作了详细讨论 相似文献
5.
6.
Microstructure effect on chemical etching behavior of the annealed Ti-6Al-4V and Ti-3Al-2.5V titanium (Ti) alloys was compared with that of unalloyed commercially pure titanium. The microstructural evolution of structure phases after annealing the titanium and its alloys at temperature near and above β transus and followed by furnace cooling to room temperature was studied using optical microscope, scanning electron microscope and X-ray diffraction techniques. The microstructure study illustrates that the heat treatment enhanced partitioning effect allows extensive formation of hemispherical and near spherical pits roughened surface to be readily acquired by chemically etching the annealed α + β titanium alloys. The kinetics of the chemical etching reaction process show a linear dependence on time. The annealed α + β titanium alloys that exhibit relatively lower weight loss and thickness reduction rate illustrate less chemical activity than the annealed unalloyed titanium. 相似文献
7.
A hierarchical structure (HS) analysis (β-test and γ-test) is applied to a fully developed turbulent pipe flow. Velocity signals are measured at two cross sections in the pipe and at a series of radial locations from the pipe wall. Particular attention is paid to the variation of turbulent statistics at wall units 10<y+<3000. It is shown that at all locations the velocity fluctuations satisfy the She–Leveque hierarchical symmetry (Phys. Rev. Lett. 72 (1994) 336). The measured HS parameters, β and γ, are interpreted in terms of the variation of fluid structures. Intense anisotropic fluid structures generated near the wall appear to be more singular than the most intermittent structures in isotropic turbulence and appear to be more outstanding compared to the background fluctuations; this yields a more intermittent velocity signal with smaller γ and β. As turbulence migrates into the logarithmic region, small-scale motions are generated by an energy cascade and large-scale organized structures emerge which are also less singular than the most intermittent structures of isotropic turbulence. At the center, turbulence is nearly isotropic, and β and γ are close to the 1994 She–Leveque predictions. A transition is observed from the logarithmic region to the center in which γ drops and the large-scale organized structures break down. We speculate that it is due to the growing eddy viscosity effects of widely spread turbulent fluctuations in a similar way as in the breakdown of the Taylor vortices in a turbulent Couette–Taylor flow at high Reynolds numbers. 相似文献
8.
9.
用变加速动力学的急动度(加加速度)概念,分析了车辆、电梯的乘座舒适性与高层钢结构建筑的风振舒适性问题. 相似文献
10.
Hong She Wang Jun E. Zeng 《中国化学快报》2007,18(12):1447-1450
Synthesis of symmetrical diaryl sulfoxides from arenes and thionyl chloride in the presence of a catalytic amount of iodine at room temperature under solvent-free conditions is described.Mild reaction conditions,easy workup,high yield,and easily available catalyst are important features of this method. 相似文献