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931.
Conservation laws for variable coefficient nonlinear wave equations with power nonlinearities 下载免费PDF全文
Conservation laws for a class of variable coefficient nonlinear wave equations with power nonlinearities are investigated.The usual equivalence group and the generalized extended one including transformations which are nonlocal with respect to arbitrary elements are introduced.Then,using the most direct method,we carry out a classification of local conservation laws with characteristics of zero order for the equation under consideration up to equivalence relations generated by the generalized extended equivalence group.The equivalence with respect to this group and the correct choice of gauge coefficients of the equations play the major roles for simple and clear formulation of the final results. 相似文献
932.
Symmetry solutions of a nonlinear elastic wave equation with third-order anharmonic corrections 总被引:1,自引:0,他引:1
M.Tahir Mustafa Khalid Masood 《应用数学和力学(英文版)》2009,30(8):1017-1026
Lie symmetry method is applied to analyze a nonlinear elastic wave equation for longitudinal deformations with third-order anharmonic corrections to the elastic energy. Symmetry algebra is found and reductions to second-order ordinary differential equations (ODEs) are obtained through invariance under different symmetries. The reduced ODEs are further analyzed to obtain several exact solutions in an explicit form. It was observed in the literature that anharmonic corrections generally lead to solutions with time-dependent singularities in finite times singularities, we also obtain solutions which Along with solutions with time-dependent do not exhibit time-dependent singularities. 相似文献
933.
934.
MA Hong-Cai LOU Sen-Yue 《理论物理通讯》2005,44(2):193-196
The general Lie point symmetry groups of the Nizhnik-Novikov-Vesselov (NNV) equation and the asymmetric NNV equation are given by a simple direct method with help of their weak Lax pairs. 相似文献
935.
Based on the FS(Finnis-Sinclair) many-body potential model, the rapid cooling process of a system, which consists of 375 Cu atoms and 125 Au atoms, controlled by period boundary condition was simulated. The dependence of pair distribution function of melten compound AuCu3 on the temperature under these conditions was researched. It can be concluded that the noncrystal exists under 700 K, and the liquid-glass transition temperature is approximately 680 K according to the Abraham′s method. Furthermore, the feature of version of cluster in melten AuCu3 was investigated by Honeycutt pair analysis technique. It is demonstrated that the structural configuration in melten AuCu3 has remarkable variation during the formation of noncrystal according to the relationship between the bonded pairs and polyhedron and temperatures. The defective polyhedra in liquid AuCu3 have greatest changes accompanying the changing temperatures. 相似文献
936.
937.
V. Meden W. Metzner U. Schollwöck O. Schneider T. Stauber K. Schönhammer 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(4):631-646
We present a study of the one-particle spectral properties for a variety of models of Luttinger liquids with open boundaries.
We first consider the Tomonaga-Luttinger model using bosonization. For weak interactions the boundary exponent of the power-law
suppression of the spectral weight close to the chemical potential is dominated by a term linear in the interaction. This
motivates us to study the spectral properties also within the Hartree-Fock approximation. It already gives power-law behavior
and qualitative agreement with the exact spectral function. For the lattice model of spinless fermions and the Hubbard model
we present numerically exact results obtained using the density-matrix renormalization-group algorithm. We show that many
aspects of the behavior of the spectral function close to the boundary can again be understood within the Hartree-Fock approximation.
For the repulsive Hubbard model with interaction U the spectral weight is enhanced in a large energy range around the chemical potential. At smaller energies a power-law suppression,
as predicted by bosonization, sets in. We present an analytical discussion of the crossover and show that for small U it occurs at energies exponentially (in -1/U) close to the chemical potential, i.e. that bosonization only holds on exponentially small energy scales. We show that such a crossover can also be found in other
models.
Received 8 February 2000 and Received in final form 25 April 2000 相似文献
938.
K. Keren A. Stern U. Sivan 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(2):311-318
Though atoms and quantum dots typically contain a comparable number of electrons, the number of discrete levels resolved in
spectroscopy experiments is very different for the two systems. In atoms, hundreds of levels are observed while in quantum
dots that number is usually smaller than 10. In the present work, this difference is traced to the different confining potentials
in these systems. In atoms, the soft confining potential leads to large spatial extent of the excited electron's wave function
and hence to weak Coulomb interaction with the rest of the atomic electrons. The resulting level broadening is smaller than
the single particle level spacing and decreases as the excitation energy is increased. In quantum dots, on the other hand, the sharp confining potential results in electron-electron
scattering rates that grow rapidly with energy and fairly quickly exceed the approximately constant single particle level
spacing. The number of discrete levels in quantum dots is hence limited by electron-electron interaction, whose effect is
negligible in atoms.
Received 3 April 2000 and Received in final form 7 August 2000 相似文献
939.
E.P. Nakhmedov H. Feldmann R. Oppermann 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(3):515-520
A new diagrammatic method, which is a reformulation of Berezinskii's technique, is constructed to study the density of electronic
states of a one-channel weakly disordered ring, threaded by an external magnetic flux. The exact result obtained for the density
of states shows an oscillation of with a period of the flux quantum . As the sample length (or the impurity concentration) is reduced, a transition takes place from the weak localization regime
() to the ballistic one (). The analytical expression for the density of states shows the exact dependence of on the ring's circumference and on disorder strength for both regimes.
Received 27 December 1999 相似文献
940.
In this paper, by using the classical Lie symmetry approach, Lie point symmetries and reductions of one Blaszak– Marciniak(BM) four-field lattice equation are obtained. Two kinds of exact solutions of a rational form and an exponential form are given. Moreover, we show that the equation has a sequence of generalized symmetries and conservation laws of polynomial form, which further confirms the integrability of the BM system. 相似文献