全文获取类型
收费全文 | 3996篇 |
免费 | 371篇 |
国内免费 | 79篇 |
专业分类
化学 | 99篇 |
晶体学 | 7篇 |
力学 | 1321篇 |
综合类 | 19篇 |
数学 | 841篇 |
物理学 | 2159篇 |
出版年
2024年 | 19篇 |
2023年 | 43篇 |
2022年 | 43篇 |
2021年 | 61篇 |
2020年 | 145篇 |
2019年 | 135篇 |
2018年 | 90篇 |
2017年 | 113篇 |
2016年 | 88篇 |
2015年 | 122篇 |
2014年 | 203篇 |
2013年 | 233篇 |
2012年 | 150篇 |
2011年 | 241篇 |
2010年 | 181篇 |
2009年 | 225篇 |
2008年 | 271篇 |
2007年 | 226篇 |
2006年 | 222篇 |
2005年 | 174篇 |
2004年 | 166篇 |
2003年 | 173篇 |
2002年 | 150篇 |
2001年 | 111篇 |
2000年 | 110篇 |
1999年 | 79篇 |
1998年 | 89篇 |
1997年 | 72篇 |
1996年 | 68篇 |
1995年 | 52篇 |
1994年 | 42篇 |
1993年 | 45篇 |
1992年 | 40篇 |
1991年 | 48篇 |
1990年 | 23篇 |
1989年 | 27篇 |
1988年 | 22篇 |
1987年 | 21篇 |
1986年 | 18篇 |
1985年 | 26篇 |
1984年 | 18篇 |
1983年 | 6篇 |
1982年 | 17篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1973年 | 6篇 |
1971年 | 2篇 |
排序方式: 共有4446条查询结果,搜索用时 15 毫秒
11.
An analytical solution of a linearized problem of the emission of periodic internal waves by part of a plane which oscillates with a small amplitude in an arbitrary direction in a viscous exponentially stratified fluid is constructed. Solutions of the dispersion equation are given for all positions of the emitting surface (arbitrary, vertical, horizontal, and critical when one of the beam propagation directions is collinear with the emitting surface). The possibility of transition to the case of a uniform fluid, which is important for applications, is analyzed. 相似文献
12.
We obtain expressions for the energy spectrum widths of Rayleigh waves corresponding to their deformational coupling to Fermi and Boltzmann electrons in a two-dimensional layer near the surface of a semibounded solid. We evaluate the nonequilibrium energy of Rayleigh waves that depends on these widths and is caused by the same coupling to the corresponding hot electrons. We show that this energy is independent of the degeneracy degree of the electrons and is given by the mean energy of free Rayleigh waves heated up to temperature of the electrons. We find conditions under which the thermodynamics is determined by this nonequilibrium energy of Rayleigh waves in films of a certain thickness with Fermi electrons near the surface and by the equilibrium energy of bulk phonons in thicker samples. All the results are obtained using the Keldysh diagram technique applied to the case of semibounded media. 相似文献
13.
LIN Chang ZHANG Xiu-Lian 《理论物理通讯》2005,44(2):247-251
The nonlinear dust acoustic waves in two-dimensional dust plasma with dust charge variation is analytically investigated by using the formally variable separation approach. New analytical solutions for the governing equation of this system have been obtained for dust acoustic waves in a dust plasma for the first time. We derive exact analytical expressions for the general case of the nonlinear dust acoustic waves in two-dimensional dust plasma with dust charge variation. 相似文献
14.
A group representation of radiation propagation in an anisotropic medium is developed. The system of wave equations for electromagnetic potentials, obtained from the Maxwell equations with account for the constitutive equations, has been factorized. It is shown that the linear differential operator of the factorized system is orthogonal in transparent crystals and unitary in gyrotropic ones and is represented through the momentum operator. On the basis of the commutation relations for the components of this operator, the eigenvalue problem has been solved and the expression for the change in the radiant energy in the crystal in the form of spherical waves has been obtained. The dependences of the ray and phase velocities and the polarization vectors of waves on the birefringence anisotropy and gyrotropy as well as on the angular momentum, displacement current, and bound charge determining them have been analyzed. It has been established that in the general case of gyrotropic crystals where the nonreciprocity phenomenon takes place and in magnetoelectrics Maxwell equations are represented in a form similar to the Dirac equations and the electromagnetic radiation is correctly described by means of bispinors and is quantized as fermions. 相似文献
15.
A brief account of applications of polarized inelastic neutron scattering in condensed matter research is given. We show that
full polarization analysis is the only tool allowing to discriminate unambiguously between different magnetic modes in various
magnetic materials. We show by means of recent results in the Heisenberg ferromagnet EuS that the effects of dipolar interactions
can be studied on a microscopic scale. Moreover, we have found for the first time indications for the divergence of the longitudinal
fluctuations belowT
c. In the itinerant antiferromagnet chromium we demonstrate that the dynamics of the longitudinal and transverse excitations
are very different, resolving a long standing puzzle concerning the slope of their dispersion. Finally, we show that a measurement
of the polarization-dependent part of the cross section of non-centrosymmetric MnSi proves directly that the chirality of
the magnetic fluctuations is left-handed. 相似文献
16.
ZHANG WenlingDepartment of Mathematics Physics National Natural Science Foundation of China Beijing China 《中国科学A辑(英文版)》2004,(6)
We use qualitative analysis and numerical simulation to study peaked traveling wave solutions of CH-γ and CH equations. General expressions of peakon and periodic cusp wave solutions are obtained. Some previous results become our special cases. 相似文献
17.
18.
Marko Nedeljkov 《Mathematical Methods in the Applied Sciences》2004,27(8):931-955
This work gives a condition for existence of singular and delta shock wave solutions to Riemann problem for 2×2 systems of conservation laws. For a fixed left‐hand side value of Riemann data, the condition obtained in the paper describes a set of possible right‐hand side values. The procedure is similar to the standard one of finding the Hugoniot locus. Fluxes of the considered systems are globally Lipschitz with respect to one of the dependent variables. The association in a Colombeau‐type algebra is used as a solution concept. Copyright © 2004 John Wiley &Sons, Ltd. 相似文献
19.
Luis L. Bonilla 《Journal of statistical physics》1987,46(3-4):659-678
A nonlinear Fokker-Planck equation is derived to describe the cooperative behavior of general stochastic systems interacting via mean-field couplings, in the limit of an infinite number of such systems. Disordered systems are also considered. In the weak-noise limit; a general result yields the possibility of having bifurcations from stationary solutions of the nonlinear Fokker-Planck equation into stable time-dependent solutions. The latter are interpreted as non-equilibrium probability distributions (states), and the bifurcations to them as nonequilibrium phase transitions. In the thermodynamic limit, results for three models are given for illustrative purposes. A model of self-synchronization of nonlinear oscillators presents a Hopf bifurcation to a time-periodic probability density, which can be analyzed for any value of the noise. The effects of disorder are illustrated by a simplified version of the Sompolinsky-Zippelius model of spin-glasses. Finally, results for the Fukuyama-Lee-Fisher model of charge-density waves are given. A singular perturbation analysis shows that the depinning transition is a bifurcation problem modified by the disorder noise due to impurities. Far from the bifurcation point, the CDW is either pinned or free, obeying (to leading order) the Grüner-Zawadowki-Chaikin equation. Near the bifurcation, the disorder noise drastically modifies the pattern, giving a quenched average of the CDW current which is constant. Critical exponents are found to depend on the noise, and they are larger than Fisher's values for the two probability distributions considered. 相似文献
20.
An efficient way of obtaining travelling waves in a periodic fluid system is described and tested. We search for steady states in a reference frame travelling at the wave phase velocity using a first‐order pseudospectral semi‐implicit time scheme adapted to carry out the Newton's iterations. The method is compared to a standard Newton–Raphson solver and is shown to be highly efficient in performing this task, even when high‐resolution grids are used. This method is well suited to three‐dimensional calculations in cylindrical or spherical geometries. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献