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101.
1. IntroductionMany methods have been proposed for adapting the mesh to aChieve spatial resolution in thesolution of partial dthereatial equations. In addition to the capability of concedrating sufficientpoints about regions of rapid variation of the solution, a satisfactory mesh equatioll should besample, easy to program, and reasonably insensitive to the choice of its adjustable parameters.The earliest work on adaptive tecboques, based on moving trite element method (MFEM) wdone by Miller … 相似文献
102.
Fuzzy同余和正规Fuzzy子群(英文) 总被引:1,自引:0,他引:1
自从A. Rosenfeld在1971年提出Fuzzy子群的概念以来,在Fuzzy群的研究方面已有不少进展,例如见[1,2,5,6,10,11,14]。另一方面,L.A.Zadeh首创的Fuzzy关系理论的研究也是硕果累累,例如见[3,4,8,12,13,15]。本文通过Fuzzy同余关系和正规Fuzzy子群的相互联系,将这两个方向的研究成果进行“嫁接”和“杂交”,得到许多有趣的结果。主要结果是定理2.7,定理3.1和3.6。本文另一主题是引入T-Fuzzy群的正规T-Fuzzy子群的新概念,当T是正则t-范算子时,得到了T-Fuzzy群的三个同构定理,作者认为它比现有的相应同构定理更为简洁、广泛和自然。 相似文献
103.
104.
We study the almost sure limiting behavior and convergence in probability of weighted partial sums of the form
where {Wnj, 1jn, n1} and {Xnj, 1jn, n1} are triangular arrays of random variables. The results obtain irrespective of the joint distributions of the random variables within each array. Applications concerning the Efron bootstrap and queueing theory are discussed. 相似文献
105.
激光烧蚀瑞利-泰勒不稳定性模拟 总被引:9,自引:5,他引:4
给出了激光烧蚀流体不稳定性计算程序EUL2D的物理方程,介绍了计算中使用的活动网格和一些技术问题处理。EUL2D程序的计算结果与Takabe公式、FAST2D程序和LASNEX程序的结果较好符合。数值计算日本大阪大学激光烧蚀瑞利-泰勒不稳定性实验,再现了实验结果。发现了横向电子热传导烧蚀在长波长扰动的非线性瑞利-泰勒不稳定性演变中起重要作用。 相似文献
106.
S. G. Ravi Kumar P. A. Aswatha Narayana K. N. Seetharamu B. Ramaswamy 《国际流体数值方法杂志》1989,9(9):1165-1177
The velocity correction algorithm is used in the finite element method to solve forced convection problems between parallel plates with a triangular step, for Reynolds numbers up to 1000. Equal-order interpolation functions for velocity, pressure and temperature are used. The solutions show a smooth variation of pressure. The streamfunction, isotherms, isobars and velocity profiles are presented for a typical Reynolds number of 500. The skin friction and heat transfer results are presented for Reynolds numbers up to 1000. 相似文献
107.
We present a deterministic scheme for the discrete Smoluchowski's coagulation equation based on a binary grid refinement.
Starting from the binary grid Ω0={1,2,4,8,16,. . .}, we first introduce an appropriate grid refinement by adding at each level 2l grid points in every binary subsection of the grid Ωl. In a next step we derive an approximate equation for the dynamic behavior on each level Ωl based on a piecewise constant approximation of the right hand side of Smoluchowski's equation. Numerical results show that
the computational effort can be drastically decreased compared to the corresponding complete integer grid. When considering
unbounded kernels in Smoluchowski's equation we use an adaptive time step method to overcome numerical instabilities which
may occur at the tails of the density function. 相似文献
108.
The discrete Fourier transform in d dimensions with equispaced knots in space and frequency domain can be computed by the fast Fourier transform (FFT) in arithmetic operations. In order to circumvent the ‘curse of dimensionality’ in multivariate approximation, interpolations on sparse grids were introduced. In particular, for frequencies chosen from an hyperbolic cross and spatial knots on a sparse grid fast Fourier transforms that need only arithmetic operations were developed. Recently, the FFT was generalised to nonequispaced spatial knots by the so-called NFFT. In this paper, we propose an algorithm for the fast Fourier transform on hyperbolic cross points for nonequispaced spatial knots in two and three dimensions. We call this algorithm sparse NFFT (SNFFT). Our new algorithm is based on the NFFT and an appropriate partitioning of the hyperbolic cross. Numerical examples confirm our theoretical results. 相似文献
109.
110.
Hiroaki Nishikawa 《Journal of computational physics》2010,229(11):3989-4016
In this paper, we unify advection and diffusion into a single hyperbolic system by extending the first-order system approach introduced for the diffusion equation [J. Comput. Phys., 227 (2007) 315–352] to the advection–diffusion equation. Specifically, we construct a unified hyperbolic advection–diffusion system by expressing the diffusion term as a first-order hyperbolic system and simply adding the advection term to it. Naturally then, we develop upwind schemes for this entire system; there is thus no need to develop two different schemes, i.e., advection and diffusion schemes. We show that numerical schemes constructed in this way can be automatically uniformly accurate, allow O(h) time step, and compute the solution gradients (viscous stresses/heat fluxes for the Navier–Stokes equations) simultaneously to the same order of accuracy as the main variable, for all Reynolds numbers. We present numerical results for boundary-layer type problems on non-uniform grids in one dimension and irregular triangular grids in two dimensions to demonstrate various remarkable advantages of the proposed approach. In particular, we show that the schemes solving the first-order advection–diffusion system give a tremendous speed-up in CPU time over traditional scalar schemes despite the additional cost of carrying extra variables and solving equations for them. We conclude the paper with discussions on further developments to come. 相似文献