全文获取类型
收费全文 | 393篇 |
免费 | 40篇 |
国内免费 | 9篇 |
专业分类
化学 | 20篇 |
力学 | 24篇 |
综合类 | 2篇 |
数学 | 34篇 |
物理学 | 362篇 |
出版年
2023年 | 3篇 |
2022年 | 9篇 |
2021年 | 7篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2017年 | 11篇 |
2016年 | 13篇 |
2015年 | 4篇 |
2014年 | 16篇 |
2013年 | 17篇 |
2012年 | 24篇 |
2011年 | 30篇 |
2010年 | 14篇 |
2009年 | 25篇 |
2008年 | 26篇 |
2007年 | 39篇 |
2006年 | 13篇 |
2005年 | 16篇 |
2004年 | 44篇 |
2003年 | 17篇 |
2002年 | 17篇 |
2001年 | 16篇 |
2000年 | 16篇 |
1999年 | 7篇 |
1998年 | 11篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1983年 | 1篇 |
排序方式: 共有442条查询结果,搜索用时 109 毫秒
161.
For Hawking radiation, treated as a tunneling process, the no-hair theorem of black hole together with the law of energy conservation is utilized to postulate that the tunneling rate only depends on the external qualities (e.g., the mass for the Schwarzschild black hole) and the energy of the radiated particle. This postulate is justified by the WKB approximation for calculating the tunneling probability. Based on this postulate, a general formula for the tunneling probability is derived without referring to the concrete form of black hole metric. This formula implies an intrinsic correlation between the successive processes of the black hole radiation of two or more particles. It also suggests a kind of entropy conservation and thus resolves the puzzle of black hole information loss in some sense. 相似文献
162.
Mei symmetry and conservation laws of discrete nonholonomic dynamical systems with regular and irregular lattices 下载免费PDF全文
In this paper,Noether symmetry and Mei symmetry of discrete nonholonomic dynamical systems with regular and the irregular lattices are investigated.Firstly,the equations of motion of discrete nonholonomic systems are introduced for regular and irregular lattices.Secondly,for cases of the two lattices,based on the invariance of the Hamiltomian functional under the infinitesimal transformation of time and generalized coordinates,we present the quasi-extremal equation,the discrete analogues of Noether identity,Noether theorems,and the Noether conservation laws of the systems.Thirdly,in cases of the two lattices,we study the Mei symmetry in which we give the discrete analogues of the criterion,the theorem,and the conservative laws of Mei symmetry for the systems.Finally,an example is discussed for the application of the results. 相似文献
163.
电路中伴随自感现象发生的过程中,电路中线圈的电压、电流的变化遵循着一定的规律,这个规律在大学"普通物理"课程中被界定为"暂态"过程. 相似文献
164.
1 问题的提出
在高中物理分组实验中,验证动量守恒定律非常重要,所用的器材如图1所示.
实验时两个小球离开实验槽“落地”后则满地滚.学生要找小球耽误时间.此外小球下落打在复写纸上时通常又弹跳起来再次“落地”, 相似文献
165.
In this paper, based on the discrete zero curvature representation, isospectrai and nonisospectrai lattice hierarchies are proposed. By means of solving corresponding discrete spectral equations, we demonstrate the existence of infinitely many conservation laws for this two hierarchies and obtain the formulae of the corresponding conserved densities and associated fluxes. 相似文献
166.
相对性原理要求粒子的动量和能量对于速度的依赖关系在不同的惯性系中具有相同的函数形式,由此无需利用守恒定律和洛伦兹变换公式直接推导出相对论质速关系,证明了守恒定律和洛伦兹变换公式都不是推导相对论质速关系的必要条件.由相对论质速关系进一步可得到惯性系的广义洛伦兹变换公式,从而揭示了质能关系和质速关系是比洛伦兹变换公式适用范围更广的相对论基本公式. 相似文献
167.
168.
It is shown that the two-component Camassa-Holm and Hunter-Saxton systems are geometrically integrable, namely they describe pseudo-spherical surfaces. As a consequence, their infinite number of conservation laws are directly constructed. In addition, a class of nonlocal symmetries depending on the pseudo-potentials are obtained. 相似文献
169.
In this paper, a classical system of ordinary differential equations is built to describe a kind of n-dimensional quantum systems. The absorption spectrum and the density of the states for the system are defined from the points of quantum view and classical view. From the Birkhoffian form of the equations, a Birkhoffian symplectic scheme is derived for solving n-dimensional equations by using the generating function method. Besides the Birkhoffian structure- preserving, the new scheme is proven to preserve the discrete local energy conservation law of the system with zero vector f . Some numerical experiments for a 3-dimensional example show that the new scheme can simulate the general Birkhoffian system better than the implicit midpoint scheme, which is well known to be symplectic scheme for Hamiltonian system. 相似文献
170.
在物理学中对称性的研究是非常重要的。对称性的研究可追溯到远古的中华和希腊文化。物理世界中的对称性能使人们抓住事物的本质,使复杂的问题变为简单且能控制。现代科学对各种对称性有很好的定性和定量的描述,而且认识到对称性与守恒定律有着密切的联系。1918年Noether证明在古典力学中相对于每一种对称性存在着一守恒量。比如说,两个点粒子之间的引力作用具有连续的空间转动不变性,这一系统的总角动量是守恒的,也就是说空间旋转对称性对应着角动量守恒。 相似文献