全文获取类型
收费全文 | 1578篇 |
免费 | 279篇 |
国内免费 | 74篇 |
专业分类
化学 | 148篇 |
晶体学 | 5篇 |
力学 | 24篇 |
综合类 | 28篇 |
数学 | 333篇 |
物理学 | 1393篇 |
出版年
2024年 | 2篇 |
2023年 | 10篇 |
2022年 | 18篇 |
2021年 | 24篇 |
2020年 | 27篇 |
2019年 | 16篇 |
2018年 | 31篇 |
2017年 | 31篇 |
2016年 | 50篇 |
2015年 | 42篇 |
2014年 | 122篇 |
2013年 | 71篇 |
2012年 | 117篇 |
2011年 | 72篇 |
2010年 | 70篇 |
2009年 | 86篇 |
2008年 | 106篇 |
2007年 | 97篇 |
2006年 | 92篇 |
2005年 | 111篇 |
2004年 | 77篇 |
2003年 | 86篇 |
2002年 | 94篇 |
2001年 | 60篇 |
2000年 | 55篇 |
1999年 | 53篇 |
1998年 | 55篇 |
1997年 | 48篇 |
1996年 | 37篇 |
1995年 | 33篇 |
1994年 | 34篇 |
1993年 | 23篇 |
1992年 | 22篇 |
1991年 | 18篇 |
1990年 | 17篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1977年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有1931条查询结果,搜索用时 31 毫秒
1.
2.
The dependence of the beam propagation factor (M
2 parameter) with the absorbed pump power in the case of monolithic microchip laser under face-cooled configuration is extensively
studied. Our investigations show that the M
2 parameter is related to the absorbed pump power through two parameters (α and β) whose values depend on the laser material properties and laser configuration. We have shown that one parameter arises due
to the oscillation of higher order modes in the microchip cavity and the other parameter accounts for the spherical aberration
associated with the thermal lens induced by the pump beam. Such dependency of M
2 parameter with the absorbed pump power is experimentally verified for a face-cooled monolithic microchip laser based on Nd3+ -doped GdVO4 crystal and the values of α and β parameters were estimated from the experimentally measured data points. 相似文献
3.
Huafei Sun 《Geometriae Dedicata》2002,90(1):63-75
We study minimal submanifolds in the locally symmetric and conformally flat Riemannian manifold and generalize Yau's result obtained in J. Amer. Math. 97 (1975), 76–100. 相似文献
4.
Benjamin J. K. Evans Susan M. Scott Antony C. Searle 《General Relativity and Gravitation》2002,34(10):1675-1684
We have developed a new tool for numerical work in General Relativity: GRworkbench. We discuss how GRworkbench's implementation of a numerically-amenable analogue to Differential Geometry facilitates the development of robust and chart-independent numerical algorithms. We consider, as an example, geodesic tracing on two charts covering the exterior Schwarzschild space-time. 相似文献
5.
6.
Rossella Bartolo Anna Germinario Miguel Sánchez 《Annals of Global Analysis and Geometry》2002,21(1):63-84
In this paper the problem of the geodesic connectedness and convexity ofincomplete Riemannian manifolds is analyzed. To this aim, a detailedstudy of the notion of convexity for the associated Cauchy boundary iscarried out. In particular, under widely discussed hypotheses,we prove the convexity of open domains (whose boundaries may benondifferentiable) of a complete Riemannian manifold. Variationalmethods are mainly used. Examples and applications are provided,including a result for dynamical systems on the existence oftrajectories with fixed energy. 相似文献
7.
Based on the Collins formula and irradiance moments definition, the propagation of the kurtosis parameter of super-Gaussian beams through a spherically aberrated lens is studied. Detailed numerical results are given. It is shown that, as compared with aberration-free super-Gaussian beams, the profile of spherically aberrated super-Gaussian beams can be leptokurtic, mesokurtic or platykurtic, depending on the aberration and propagation distance. The results for the spherically aberrated Gaussian beams can be dealt with as a special case treated in this paper. Finally, the advantage of our method is pointed out. 相似文献
8.
在二极管泵浦固体激光器耦合光学系统中,柱面透镜起着非常重要的作用。随着系统轻量化、小型化的要求需要用重量轻、尺寸小的光学器件来替代。本文介绍一种用于替代柱面透镜的二元光学元件的设计和制作方法。 相似文献
9.
10.
Forces along Equidistant Particle Paths 总被引:1,自引:1,他引:0
Two particles on the sphere leave the equator moving due south and travel at a constant and equal speed along a geodesic colliding
at the south pole. An observer who is unaware of the curvature of the space will conclude that there is an attractive force
acting between the particles. On the other hand, if particles travel at the same speed (initially parallel) along geodesics
in the hyperbolic plane, then the particle paths diverge. Imagine two particles in the hyperbolic plane that are bound together
at a constant distance with their center of mass traveling along a geodesic path at a constant velocity, then the force due
to the curvature of the space acts to break the bond and increases as a quadratic function of the velocity. We consider this
problem for the sphere and the hyperbolic plane and we give the exact formula for the apparent force between the particles.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献