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691.
In this paper a method is developed to study the first eigenfunction u>0 of the Laplacian. It is based on a study of the distribution function for u. The distribution function satisfies an integro–differential inequality, and by introducing a maximal solution Z of the corresponding equation, bounds obtained for Z are then used to estimate u. These bounds come from a detailed study of Z, especially the basic identity derived in Theorem 3.1. 相似文献
692.
S. P. Gavrilov A. A. Vertiy 《International Journal of Infrared and Millimeter Waves》1997,18(9):1739-1760
Tomographic methods of image reconstruction of two-dimensional cross-sections of volumetric objects in millimeter wavelengths
band are suggested and considered.
It is shown that in the frequency band under consideration, the images of investigated objects may be obtained by first-order
diffraction tomography method (Born, Rytov or high frequency approximation of the first-order for scattered electromagnetic
field). 相似文献
694.
Douglas Henderson Stefan Sokolowski Darsh Wasan 《Journal of statistical physics》1997,89(1-2):233-247
A fluid of hard spheres confined between two hard walls and in equilibrium with a bulk hard-sphere fluid is studied using
a second-order Percus-Yevick approximation. We refer to this approximation as second-order because the correlations that are
calculated depend upon the position of two hard spheres in the confined fluid. However, because the correlation functions
depend upon the positions of four particles (two hard spheres and two walls treated as giant hard spheres), this is the most
demanding application of the second-order theory that has been attempted. When the two walls are far apart, this calculation
reduces to our earlier second-order approximation calculations of the properties of hard spheres near a single hard wall.
Our earlier calculations showed this approach to be accurate for the single-wall case. In this work we calculate the density
profiles and the pressure of the hard-sphere fluid on the walls. We find, by comparison with grand canonical Monte Carlo results,
that the second-order approximation is very accurate, even when the two walls have a small separation. We compare with a singlet
approximation (in the sense that correlation functions that depend on the position of only one hard sphere are considered).
The singlet approach is fairly satisfactory when the two walls are far apart but becomes unsatisfactory when the two walls
have a small separation. We also examine a simple theory of the pressure of the confined hard spheres, based on the usual
Percus-Yevick theory of hard-sphere mixtures. Given the simplicity of the latter approach the results of this simple (and
explicit) theory are surprisingly good. 相似文献
695.
L. A. Ferrari 《Il Nuovo Cimento D》1992,14(8):843-849
Summary Using simple, approximate arguments, we obtain a formula that relates the average spacing between peaks in the transmitted
intensityvs. wave frequency distribution of a single configuration of a random distribution of scatterers to the diffusion constant, sample
thickness, and effective absorption length. The value of the diffusion constant obtained this way is found to be within 20%
of the value obtained via intensity-intensity autocorrelation function techniques.
The author of this paper has agreed to not receive the proofs for correction. 相似文献
696.
基于达朗贝尔公式,讨论了半无界弦自由振动时的非齐次边界条件的延拓问题.结果表明:对半无界弦自由振动时的非齐次边界条件的延拓,理论上可有多种方法,尽管延拓表达式不同,但不会影响最终结果.文中最后还给出了两种相对简单的延拓方法. 相似文献
697.
Heinz -Jürgen Wagner 《Journal of statistical physics》1989,55(5-6):1293-1302
It is argued that the up to now only existing expression for the microscopic stress tensor in the presence of many-body interactions, while being formally acceptable, displays some physical shortcomings. These unpleasant features are remedied by explicitly constructing and symmetrizing a new stress tensor field. With the help of this construction, some recent results on the appearance of extremely long-ranged correlations involving the stress tensor field in systems with spontaneously broken symmetries are generalized. 相似文献
698.
Approaches to consistency adjustment 总被引:5,自引:0,他引:5
E. Blankmeyer 《Journal of Optimization Theory and Applications》1987,54(3):479-488
699.
Juri N. Grin 《Monatshefte für Chemie / Chemical Monthly》1986,117(8-9):921-932
On the basis of a concept of inhomogeneous linear structure series a model for the Chimney-LadderNowotny phases is proposed. All the phases can be explained as members of a structural series of general formulaT
p+2q+3r
B
2p+2q+4r
,T-transition metal of 5–7 groups,B-Al, Ga, Si, Ge, Sn. The real and possible hypothetical members of this series are described by the symmetry of 21 monoclinic, orthorhombic and tetragonal space groups. The structure types for Tc4Si7 and Mo9Ge16 have been proposed. 相似文献
700.
We studied synchronization behaviours of spiral waves in a two-layer
coupled inhomogeneous excitable system. It was found that phase
synchronization can be observed under weak coupling strength. By
increasing the coupling strength, the synchronization is broken
down. With the further increase of the coupling strength, complete
synchronization and phase synchronization occur again. We also found
that the inhomogeneity in excitable systems is helpful to the
synchronization. 相似文献