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991.
A Taylor series augmentation of a weak statement (a ‘Taylor weak statement’ or ‘Taylor-Galerkin’ method) is used to systematically reduce the dispersion error in a finite element approximation of the one-dimensional transient advection equation. A frequency analysis is applied to determine the phase velocity of semi-implicit linear, quadratic and cubic basis one-dimensional finite element methods and of several comparative finite difference/finite volume algorithms. The finite element methods analysed include both Galerkin and Taylor weak statements. The frequency analysis is used to obtain an improved linear basis Taylor weak statement finite element algorithm. Solutions are reported for verification problems in one and two dimensions and are compared with finite volume solutions. The improved finite element algorithms have sufficient phase accuracy to achieve highly accurate linear transient solutions with little or no artificial diffusion. 相似文献
992.
Under certain conditions, the Bose-Einstein condensate confined in a two-dimensional harmonic trap is associated with a one-dimensional nonlinear Schrödinger equation and a soliton solution. The influence of the initial condition on the solution is discussed. The critical initial number of condensed atoms to maintain a soliton is evaluated. In the
Li case, this number is of the order of thousand. The energy per particle of the solitons is also calculated. 相似文献
993.
994.
995.
In the present paper, a comparative study of numerical solutions for Newtonian fluids based on the lattice‐Boltzmann method (LBM) and the classical finite volume method (FVM) is presented for the laminar flow through a 4:1 planar contraction at a Reynolds number of value one, Re=1. In this study, the stress field for LBM is directly obtained from the distribution function. The calculations of the stress based on the FVM‐data use the evaluations of velocity gradients with finite differences. The stress field for both LBM and FVM is expressed in the present study in terms of the shear stress and the first normal stress difference. The lateral and axial profiles of the velocity, the shear stress and the first normal stress difference for both methods are investigated. It is shown that the LBM results for the velocity and the stresses are in excellent agreement with the FVM results. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
996.
S. Z. Adzhiev V. V. Vedenyapin 《Computational Mathematics and Mathematical Physics》2007,47(6):998-1006
The Boltzmann equation for a mixture of particles with different masses is modeled using symmetric discrete velocity models
that involve energy interchange between the species of the mixture. The computational complexity of this problem is investigated.
New discrete models are presented.
Published in Zhurnal Vychislitel’noi Matematiki i Matematicheskoi Fiziki, 2007, Vol. 47, No. 6, pp. 1045–1054. 相似文献
997.
This paper introduces an implicit method for advection–diffusion equations called Implicit DisPar, based on particle displacement moments applied to uniform grids. The present method tries to solve constraints associated with explicit methods also based on particle displacement methods, in which diffusivity-dominated situations can only be handled by considerably increasing the associated computational costs. In fact, a higher particle destination nodes number allows the use of higher diffusion coefficients for the transport simulation without instabilities. The average was evaluated by an analogy between the Fokker–Planck and the transport equations. The variance is considered to be Fickian. The particle displacement distribution is used to predict deterministic mass transfers between domain nodes. Mass conservation was guaranteed by the distribution concept. In the truncation error analysis, it was shown that the linear Implicit DisPar formulation does not have numerical error up to v − 1 order, if the first v particle moments are forced by the Gaussian moments. It was shown by theoretical tests for linear conditions that the model accuracy level is proportional to the number of particle destination nodes. 相似文献
998.
A. Bonasera R. Coniglione P. Sapienza 《The European Physical Journal A - Hadrons and Nuclei》2006,30(1):47-64
We review some results on energetic particle production in heavy-ion collisions below roughly 100A·MeV, both theoretically
and experimentally. We discuss the possible mechanisms of particle production, as well as the possibility to gather information
on the nuclear equation of state (EOS) from data. Results on subthreshold pions, energetic photons, nucleons and light charged
particles (Z ⩽ 2) are discussed and contrasted to microscopic models. Important information about the first stages of the reaction are
obtained by such probes. At present, we can conclude that we have at least a qualitative understanding of the processes involved
when such particles are produced. However, a quantitative determination of relevant EOS parameters is still missing. The production
mechanism close to the kinematical threshold (incoherent, cooperative or statistical) is not completely elucidated either.
This calls for new data using more modern detector systems and comparison to more refined microscopic models. 相似文献
999.
BALUJA Shipra 《中国化学》2006,24(10):1327-1331
From experimental data of density,viscosity and ultrasonic velocity,the various acoustical properties,such asspecific impedance(Z),isentropic compressibility(к_s),Rao's molar sound function(R_m),the van der Waals con-stant(b),molar compressibility(W),intermolecular free length(L_f),relaxation strength(r),internal pressure(π),free volume(V_f),solvation number(S_n)etc.,were calculated for three Schiff bases in 1,4-dioxane and dimethylfor-mamide(DMF)at 318.15 K.The results are interpreted in terms of molecular interactions occurring in the solu-tions. 相似文献
1000.