全文获取类型
收费全文 | 4244篇 |
免费 | 347篇 |
国内免费 | 518篇 |
专业分类
化学 | 558篇 |
晶体学 | 20篇 |
力学 | 309篇 |
综合类 | 53篇 |
数学 | 2781篇 |
物理学 | 1388篇 |
出版年
2023年 | 52篇 |
2022年 | 58篇 |
2021年 | 78篇 |
2020年 | 79篇 |
2019年 | 122篇 |
2018年 | 112篇 |
2017年 | 131篇 |
2016年 | 126篇 |
2015年 | 113篇 |
2014年 | 207篇 |
2013年 | 342篇 |
2012年 | 128篇 |
2011年 | 216篇 |
2010年 | 215篇 |
2009年 | 265篇 |
2008年 | 323篇 |
2007年 | 241篇 |
2006年 | 248篇 |
2005年 | 222篇 |
2004年 | 205篇 |
2003年 | 187篇 |
2002年 | 201篇 |
2001年 | 146篇 |
2000年 | 140篇 |
1999年 | 123篇 |
1998年 | 109篇 |
1997年 | 105篇 |
1996年 | 73篇 |
1995年 | 53篇 |
1994年 | 54篇 |
1993年 | 36篇 |
1992年 | 32篇 |
1991年 | 25篇 |
1990年 | 26篇 |
1989年 | 23篇 |
1988年 | 19篇 |
1987年 | 14篇 |
1986年 | 14篇 |
1985年 | 21篇 |
1984年 | 17篇 |
1983年 | 11篇 |
1982年 | 22篇 |
1981年 | 33篇 |
1980年 | 30篇 |
1979年 | 21篇 |
1978年 | 19篇 |
1977年 | 19篇 |
1976年 | 19篇 |
1975年 | 11篇 |
1973年 | 7篇 |
排序方式: 共有5109条查询结果,搜索用时 15 毫秒
1.
《Physics letters. A》2019,383(23):2784-2788
By modifying the conventional one-electron hopping behavior, we study effects of an occupation-dependent hopping on the ground state of the half-filled one-dimensional pair-hopping model. At weak coupling, the use of bosonization and renormalization-group analysis techniques helps to derive the phase diagram. Such unusual hopping is shown to drive a spin-gap transition and to introduce a new region where the triplet superconducting instability dominates for positively small pair-hopping interaction. 相似文献
2.
设E为一个可数集,Q=(qi,j;i,j∈E)为E×E上的矩阵,满足m为E上的概率分布满足何时存在Q过程,使得m是它的不变分布? 这个问题由Williams(1979)作为一个开问题提出.文[15]对全稳定情形,解决了这个问题;本文对单瞬时情形,完整地解决了该问题. 相似文献
3.
4.
在不同激光脉宽下的高次谐波 总被引:3,自引:2,他引:1
用数值计算方法计算了不同强激光脉冲宽度下高次谐波的产生.我们发现对于激光场强度不高,不能有效电离初态的激光场,长脉冲宽度可以更有效产生高次谐波;而对于高场强的激光场,由于它能够在几个光学周期之内把原子的初态全部电离,所以短脉冲的激光场能够更有效产生高次谐波. 相似文献
5.
S. K. Godunov V. T. Zhukov O. B. Feodoritova 《Computational Mathematics and Mathematical Physics》2006,46(6):971-982
An algorithm is constructed for calculating invariant subspaces of symmetric hyperbolic systems arising in electromagnetic, acoustic, and elasticity problems. Discrete approximations are calculated for subspaces that correspond to minimal eigenvalues and smooth eigenfunctions. Difficulties related to the presence of an infinite-dimensional kernel in the differential operator are successfully handled. The efficiency of the algorithm is demonstrated using acoustics equations. 相似文献
6.
Quantization of Underdamped, Critically Damped, and Overdamped Electric Circuits with a Power Source
Jeong-Ryeol Choi 《International Journal of Theoretical Physics》2002,41(10):1931-1939
We have investigated the quantum mechanical effect of the underdamped, critically damped, and overdamped electric circuits with a power source. The charge of the underdamped circuit oscillates while those of the critically damped and overdamped ones don't. The wave function of the system of overdamped circuit represented parabolic cylinder function while underdamped circuit was represented by well-known Hermite polynomial. The eigenvalues of underdamped circuit is discrete while those of the critically damped and overdamped ones are given as continuously. 相似文献
7.
Fillmore在[1]中得到一个定理:设A,T是Banach空间X上的线性变换,A有界,若Lat(A) Lat(T)且AT=TA,则T是A的多项式.在本文里,以此作为引理,讨论了Banach空间上可逆线性变换A在什么情况下,A-1可表示为A的多项式.本文最主要的结论是定理3.4:设X是Banach空间,A是X上的有界线性变换,且可逆,则A-1是A的多项式当且仅当A-1是A的局部多项式. 相似文献
8.
Shinji Takesue 《Journal of statistical physics》1989,56(3-4):371-402
This is the first part of a series devoted to the study of thermodynamic behavior of large dynamical systems with the use of a family of fully-discrete and conservative models named elementary reversible cellular automata (ERCAs). In this paper, basic properties such as conservation laws and phase space structure are investigated in preparation for the later studies. ERCAs are a family of one-dimensional reversible cellular automata having two Boolean variables on each site. Reflection and Boolean conjugation symmetries divide them into 88 equivalence classes. For each rule, additive conserved quantities written in a certain form are regarded as a kind of energy, if they exist. By the aid of the discreteness of the variables, every ERCA satisfies the Liouville theorem or the preservation of phase space volume. Thus, if an energy exists in the above sense, statistical mechanics of the model can formally be constructed. If a locally defined quantity is conserved, however, it prevents the realization of statistical mechanics. The existence of such a quantity is examined for each class and a number of rules which have at least one energy but no local conservation laws are selected as hopeful candidates for the realization of thermodynamic behavior. In addition, the phase space structure of ERCAs is analyzed by enumerating cycles exactly in the phase space for systems of comparatively small sizes. As a result, it is revealed that a finite ERCA is not ergodic, that is, a large number of orbits coexist on an energy surface. It is argued that this fact does not necessarily mean the failure of thermodynamic behavior on the basis of an analogy with the ergodic nature of infinite systems. 相似文献
9.
We introduce the notion of an invariant of characteristics for a system of first-order partial differential equations. We prove that the existence of invariants is connected with passiveness of some systems. We describe a few methods for construction of new invariants from those already known. We give a scheme for application of the invariants to reduction and integration of systems of partial differential equations. As an application we consider the equation of gas dynamics. 相似文献
10.
Jeong Ryeol Choi 《International Journal of Theoretical Physics》2004,43(4):947-958
We derived the WKB wave function for the general time-dependent quadratic Hamiltonian system using a unitary transformation method. We applied our research to sinusodially drived Caldirola–Kanai oscillator and confirmed that the time evolution of our approximated WKB wave function is similar to that of the exact one. This wave function can be used to analyze the interference between the probability amplitudes contributed by the area of overlap in phase space of quantum states. 相似文献