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31.
Ab initio values for the potential energy functions for ion–neutral interactions can be tested by comparison with gaseous ion transport coefficients, but only if special care is taken to compute the interaction potentials accurately over wide ranges of internuclear separation. This is illustrated here by a reanalysis of the ab initio values for the coinage metal ions interacting with rare gas atoms, precise calculations of the transport cross sections over extremely wide ranges of energy, and similarly precise calculations of the zero-field ion mobilities as functions of gas temperature and the field-dependent ion mobilities at various fixed temperatures. The calculations indicate that the mobilities for Ag+(1S) moving in Ne or Ar can distinguish between the existing, very similar ab initio potentials. They also show that substantial differences exist among the mobilities of the coinage metal anions and the ground and excited states of the cations. The techniques implemented are recommended for future ab initio calculations. 相似文献
32.
Two hydrated hydroxy magnesium carbonate minerals brugnatellite and coalingite with a hydrotalcite‐like structure were studied by Raman spectroscopy. Intense bands are observed at 1094 cm−1 for brugnatellite and at 1093 cm−1 for coalingite attributed to the CO32−ν1 symmetric stretching mode. Additional low intensity bands are observed at 1064 cm−1. The existence of two symmetric stretching modes is accounted for in terms of different anion structural arrangements. Very low intensity bands at 1377 and 1451 cm−1 are observed for brugnatellite, and the Raman spectrum of coalingite displays two bands at 1420 and 1465 cm−1 attributed to the (CO3)2−ν3 antisymmetric stretching modes. Very low intensity bands at 792 cm−1 for brugnatellite and 797 cm−1 for coalingite are assigned to the CO32− out‐of‐plane bend (ν2). X‐ray diffraction studies by other researchers have shown that these minerals are disordered. This is reflected in the difficulty of obtaining Raman spectra of reasonable quality and explains why the Raman spectra of these minerals have not been previously or sufficiently described. A comparison is made with the Raman spectra of other hydrated magnesium carbonate minerals. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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36.
Balance equations are derived from Enskog’s kinetic equation for a two-dimensional system of hard disks using Grad’s moment
expansion method. This set of equations constitute an extended hydrodynamics for moderately dense bi-dimensional fluids. The
set of independent hydrodynamic fields in the present formulations are: density, velocity, temperature and also—following Grad’s original idea—the symmetric and traceless pressure tensor p
ij
and the heat flux vector q
k
. An approximation scheme similar in spirit to one made by Grad in his original work is made. Once the hydrodynamics is derived
it is used to discuss the nature of a simple one-dimensional heat conduction problem. It is shown that, not too far from equilibrium,
the nonequilibrium pressure in this case only depends on the density, temperature and heat flux vector.
PACS: 51.10.+y, 05.20.Jj, 44.10.+i, 05.70.Ln 相似文献
37.
D. Lee 《The European Physical Journal A - Hadrons and Nuclei》2008,35(2):171-187
The symmetric heavy-light ansatz is a method for finding the ground state of any dilute unpolarized system of attractive two-component
fermions. Operationally it can be viewed as a generalization of the Kohn-Sham equations in density functional theory applied
to N -body density correlations. While the original Hamiltonian has an exact Z2 symmetry, the heavy-light ansatz breaks this symmetry by skewing the mass ratio of the two components. In the limit where
one component is infinitely heavy, the many-body problem can be solved in terms of single-particle orbitals. The original
Z2 symmetry is recovered by enforcing Z2 symmetry as a constraint on N -body density correlations for the two components. For the 1D, 2D, and 3D attractive Hubbard models the method is in very
good agreement with exact Lanczos calculations for few-body systems at arbitrary coupling. For the 3D attractive Hubbard model
there is very good agreement with lattice Monte Carlo results for many-body systems in the limit of infinite scattering length. 相似文献
38.
A rigorous and systematic intercomparison of codes used for the retrieval of trace gas profiles from high-resolution ground-based solar absorption FTIR measurements is presented for the first time. Spectra were analyzed with the two widely used independent, retrieval codes: SFIT2 and PROFFIT9. Vertical profiles of O3, HNO3, HDO, and N2O were derived from the same set of typical observed spectra. Analysis of O3 was improved by using updated line parameters. It is shown that profiles and total column amounts are in excellent agreement, when similar constraints are applied, and that the resolution kernel matrices are also consistent. Owing to the limited altitude resolution of ground-based observations, the impact of the constraints on the solution is not negligible. It is shown that the results are also compatible for independently chosen constraints. Perspectives for refined constraints are discussed. It can be concluded that the error budget introduced by the radiative transfer code and the retrieval algorithm on total columns deduced from high-resolution ground-based solar FTIR spectra is below 1%. 相似文献
39.
Christian Maes 《Journal of statistical physics》1990,61(3-4):667-681
An anisotropic lattice gas dynamics is investigated for which particles on
d
jump to empty nearest neighbor sites with (fast) rate –2 in a specified direction and some particular configuration-dependent rates in the other directions. The model is translation and reflection invariant and is particle conserving. The space coordinate in the fast-rate direction is rescaled by –1. It follows that the density field converges in probability, as 0, to the corresponding solution of a nonlinear diffusion-type equation. The microscopic fluctuations about the deterministic macroscopic evolution are determined explicitly and it is found that the stationary fluctuations decay via a power law (1/r
d
) with the direction dependence of a quadrupole field. 相似文献
40.
麦克斯韦-玻耳兹曼统计分布律的相对论修正 总被引:3,自引:0,他引:3
为了避免光速极限带来的复杂性,首先给出了理想气体分子动量的分布律公式.在此基础上,进一步讨论了麦克斯韦一玻耳兹曼统计分布律的相对论修正.解析和数值计算均表明,这一修正几乎没有可观测的物理效应.这说明,大学物理教学中介绍的麦克斯韦一玻耳兹曼速度分布律公式对实际应用已经足够精确.当然,我们决不可据此近似公式断言气体分子有一定的概率可以超光速运动. 相似文献