全文获取类型
收费全文 | 35274篇 |
免费 | 3376篇 |
国内免费 | 3102篇 |
专业分类
化学 | 7153篇 |
晶体学 | 131篇 |
力学 | 2932篇 |
综合类 | 724篇 |
数学 | 20201篇 |
物理学 | 10611篇 |
出版年
2024年 | 46篇 |
2023年 | 282篇 |
2022年 | 588篇 |
2021年 | 598篇 |
2020年 | 711篇 |
2019年 | 739篇 |
2018年 | 760篇 |
2017年 | 973篇 |
2016年 | 1053篇 |
2015年 | 870篇 |
2014年 | 1520篇 |
2013年 | 2229篇 |
2012年 | 1621篇 |
2011年 | 1957篇 |
2010年 | 1813篇 |
2009年 | 2597篇 |
2008年 | 2621篇 |
2007年 | 2637篇 |
2006年 | 2347篇 |
2005年 | 1972篇 |
2004年 | 1595篇 |
2003年 | 1533篇 |
2002年 | 1474篇 |
2001年 | 1195篇 |
2000年 | 1088篇 |
1999年 | 957篇 |
1998年 | 934篇 |
1997年 | 763篇 |
1996年 | 632篇 |
1995年 | 512篇 |
1994年 | 430篇 |
1993年 | 342篇 |
1992年 | 299篇 |
1991年 | 254篇 |
1990年 | 218篇 |
1989年 | 165篇 |
1988年 | 160篇 |
1987年 | 133篇 |
1986年 | 139篇 |
1985年 | 144篇 |
1984年 | 125篇 |
1983年 | 80篇 |
1982年 | 125篇 |
1981年 | 114篇 |
1980年 | 70篇 |
1979年 | 75篇 |
1978年 | 59篇 |
1977年 | 40篇 |
1976年 | 49篇 |
1973年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
A. Mielke 《Journal of statistical physics》1991,62(3-4):509-528
The magnetic properties of the one-dimensional Hubbard model with a hardcore interaction on a ring (periodic boundary conditions) are investigated. At finite temperatures it is shown to behave up to exponentially small corrections as a pure paramagnet. An explicit expression for the ground-state degeneracies is derived. The eigenstates of this model are used to perform a perlurbational treatment for large but finite interactions. In first order inU
1 an effective Hamiltonian for the one-dimensional Hubbard model is derived. It is the Hamiltonian of the one-dimensional Hcisenberg model with antiferromagnetic couplings between nearest neighbor spins. An asymptotic expansion for the ground-state energy is given. The results are valid for arbitrary densities of electrons. 相似文献
22.
两种拔尿管方法对膀胱功能损伤的临床观察 总被引:2,自引:0,他引:2
为观察两种不同的拔尿管方法对膀胱功能损伤的差异,将80例患者随机分成两组,分别采用改良法(40例)和常规法(40例)拔除留置尿管,分析比较了两组患者排尿顺利率、逼尿肌功能恢复率及尿道刺激症、尿失禁、尿潴留。结果表明,两组患者拔管后上述指标与情况有显著性差异,P<0.05。提示改良组膀胱功能损伤明显低于对照组。改良的拔管方法是一种值得护理推广应用的好方法。 相似文献
23.
We obtain upper bounds for the tail distribution of the first nonnegative sum of a random walk and for the moments of the overshoot over an arbitrary nonnegative level if the expectation of jumps is positive and close to zero. In addition, we find an estimate for the expectation of the first ladder epoch. 相似文献
24.
Under idealized conditions, electroconvection in a nematic liquid crystal sets in at a well-defined threshold of the driving ac voltage. Fluctuating convection rolls of a small amplitude below that threshold have been observed recently. The measurement of the amplitude of these fluctuations is described in detail in this paper. It is based on averaging the light intensity signals using the structure function and a quantitative analysis of the light deflection. 相似文献
25.
It is long known that the Fokker-Planck equation with prescribed constant coefficients of diffusion and linear friction describes
the ensemble average of the stochastic evolutions in velocity space of a Brownian test particle immersed in a heat bath of
fixed temperature. Apparently, it is not so well known that the same partial differential equation, but now with constant
coefficients which are functionals of the solution itself rather than being prescribed, describes the kinetic evolution (in
the N→∞ limit) of an
isolated
N-particle system with certain stochastic interactions. Here we discuss in detail this recently discovered interpretation.
An erratum to this article can be found at 相似文献
26.
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
27.
V. V. Kozlov 《Functional Analysis and Its Applications》2005,39(4):271-283
We discuss the symplectic geometry of linear Hamiltonian systems with nondegenerate Hamiltonians. These systems can be reduced to linear second-order differential equations characteristic of linear oscillation theory. This reduction is related to the problem on the signatures of restrictions of quadratic forms to Lagrangian planes. We study vortex symplectic planes invariant with respect to linear Hamiltonian systems. These planes are determined by the solutions of quadratic matrix equations of a special form. New conditions for gyroscopic stabilization are found. 相似文献
28.
We extend the matrix version of Cochran's statistical theorem to outer inverses of a matrix. As applications, we investigate the Wishartness and independence of matrix quadratic forms for Kronecker product covariance structures. 相似文献
29.
We propose a unified method for deducing recursive relations for the canonical partition function of a system of noninteracting particles with charge conservation if the particles follow the Bose–Einstein, Fermi–Dirac, or Maxwell–Boltzmann statistics or parastatistics. For all these types of statistics, we find recursive relations for the partition function of a new statistical model of nuclear multifragmentation with electric charge and baryon number conservation, accounting for the internal degrees of freedom of the nuclear fragments. 相似文献
30.
HUA Jianjun LIU Yanhong & ZHANG Zhihe . Institute of Physics Chinese Academy of Sciences Beijing China . College of Biomedical Engineering Capital University of Medical Sciences Beijing China Correspondence should be addressed to Hua Jianjun 《中国科学G辑(英文版)》2004,(1)
Adustyplasmacanbedefinedasacomplicatedplasmacontainingsmallsolidmattercalleddustgrainsordustparticles,whichareusuallychargednegatively,duetoelectronshighermobilitythanion,bycollectingelectronsandionsfromthebackgroundplasma.Theuniverseisfilledwithdustyplasmassuchasplanetaryrings,comettails,andnebulae.Also,inindustrialplasmaprocessing,particulatessuspendedinplasmaarethemajorcontaminationinsemiconductormanufacture.Studiesondustyplasmahavebeenextendedtofar-flungtopicssuchaswaves,instabilities,stro… 相似文献