全文获取类型
收费全文 | 41715篇 |
免费 | 5390篇 |
国内免费 | 4206篇 |
专业分类
化学 | 11222篇 |
晶体学 | 964篇 |
力学 | 9769篇 |
综合类 | 564篇 |
数学 | 14752篇 |
物理学 | 14040篇 |
出版年
2024年 | 102篇 |
2023年 | 473篇 |
2022年 | 839篇 |
2021年 | 959篇 |
2020年 | 1202篇 |
2019年 | 1043篇 |
2018年 | 1070篇 |
2017年 | 1486篇 |
2016年 | 1668篇 |
2015年 | 1317篇 |
2014年 | 2161篇 |
2013年 | 2966篇 |
2012年 | 2556篇 |
2011年 | 2940篇 |
2010年 | 2478篇 |
2009年 | 2755篇 |
2008年 | 2644篇 |
2007年 | 2648篇 |
2006年 | 2455篇 |
2005年 | 2273篇 |
2004年 | 1929篇 |
2003年 | 1730篇 |
2002年 | 1541篇 |
2001年 | 1305篇 |
2000年 | 1217篇 |
1999年 | 1097篇 |
1998年 | 1010篇 |
1997年 | 853篇 |
1996年 | 707篇 |
1995年 | 595篇 |
1994年 | 548篇 |
1993年 | 444篇 |
1992年 | 454篇 |
1991年 | 355篇 |
1990年 | 277篇 |
1989年 | 215篇 |
1988年 | 177篇 |
1987年 | 129篇 |
1986年 | 87篇 |
1985年 | 116篇 |
1984年 | 110篇 |
1983年 | 54篇 |
1982年 | 73篇 |
1981年 | 51篇 |
1980年 | 27篇 |
1979年 | 44篇 |
1978年 | 31篇 |
1977年 | 38篇 |
1976年 | 15篇 |
1957年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Andreas Rößler 《BIT Numerical Mathematics》2006,46(1):97-110
A general class of stochastic Runge–Kutta methods for Itô stochastic differential equation systems w.r.t. a one-dimensional Wiener process is introduced. The colored rooted tree analysis is applied to derive conditions for the coefficients of the stochastic Runge–Kutta method assuring convergence in the weak sense with a prescribed order. Some coefficients for new stochastic Runge–Kutta schemes of order two are calculated explicitly and a simulation study reveals their good performance. 相似文献
142.
A special model of a rarefied hard-sphere gas is considered. The hard-sphere particles undergo absolutely elastic collisions. It is assumed that particles can collide only if their nonzero velocities are orthogonal to each other. The model makes it possible to proceed from the Boltzmann equation to the Smoluchowski coagulation equation, where coagulation means that the kinetic energies of the colliding particles are added. A Monte Carlo scheme for simulation of the phenomenon is described, and the convergence of the simulation algorithm is proved. The convergence of numerical results to exact solutions of the Smoluchowski equation and to finite-difference solutions is tested. 相似文献
143.
四阶方程两点边值问题Hermite有限元解的渐近展式与外推 总被引:1,自引:0,他引:1
1引言有限元解的渐近展式是提高微分方程数值解精度的重要工具,比如亏量校正和外推就是建立在有限元解的渐近展式的基础之上.许多作者对此进行了大量的研究(见[1]-[4]),特别是文[1],提出了在研究有限元解的渐近展式中十分有用的能量嵌入技巧.本文利用能量嵌入定理得到了四阶方程两点边值问题Hermite有限元解及其二阶平均导数的渐近展式,进一步我们还讨论了它们的Richardson外推公式.考虑四阶方程两点边值问题 相似文献
144.
145.
An energy-dependent partitioning scheme is explored for extracting a small number of eigenvalues of a real symmetric matrix with the help of genetic algorithm. The proposed method is tested with matrices of different sizes (30 × 30 to 1000 × 1000). Comparison is made with Löwdin’s strategy for solving the problem. The relative advantages and disadvantages of the GA-based method are analyzed 相似文献
146.
In general, we will use the numerical differentiation when dealing with the differential equations. Thus the differential equations can be transformed into algebraic equations and then we can get the numerical solutions. But as we all have known, the numerical differentiation process is very sensitive to even a small level of errors. In contrast it is expected that on average the numerical integration process is much less sensitive to errors. In this paper, based on the Sinc method we provide a new method using Sinc method incorporated with the double exponential transformation based on the interpolation of the highest derivatives (SIHD) for the differential equations. The error in the approximation of the solution is shown to converge at an exponential rate. The numerical results show that compared with the exiting results, our method is of high accuracy, of good convergence with little computational efforts. It is easy to treat nonhomogeneous mixed boundary condition for our method, which is unlike the traditional Sinc method. 相似文献
147.
Chen-liang Li Jin-ping Zeng 《应用数学学报(英文版)》2007,23(1):79-90
We consider several synchronous and asynchronous multisplitting iteration schemes for solving aclass of nonlinear complementarity problems with the system matrix being an H-matrix.We establish theconvergence theorems for the schemes.The numerical experiments show that the schemes are efficient forsolving the class of nonlinear complementarity problems. 相似文献
148.
An analytical method is presented to investigate the bending-torsion vibration characteristics of a cylinder with an arbitrary cross-section and partially submerged in water. The compressibility and the free surface waves of the water are considered simultaneously in the analysis. The exact solution of structure–water interaction is obtained mathematically. Firstly, the analytical expression of the velocity potential of the water is derived by using the method of separation of variables. The unknown coefficients in the velocity potential are determined by the longitudinal and circumferential Fourier expansions along the outer surface of the cylinder and are expressed in the form of integral equations including the unknown dynamic bending deflection and torsional angle of the cylinder. Secondly, the force and torque acting on the cylinder per unit length, provided by the water, are obtained by integrating the water dynamic pressure along the circumference of the cylinder. The general solution of bending-torsion vibration of the cylinder under the water dynamic pressure is derived analytically. The integral equations included in the velocity potential of the water can be solved exactly. Finally, the eigenfrequency equation of cylinder–water interaction is obtained by means of the boundary conditions of the cylinder. Some numerical examples for elliptical columns partially submerged in water are provided to show the application of the present method. 相似文献
149.
B. V. Pal’tsev I. I. Chechel’ 《Computational Mathematics and Mathematical Physics》2006,46(5):820-847
The convergence rate of a fast-converging second-order accurate iterative method with splitting of boundary conditions constructed by the authors for solving an axisymmetric Dirichlet boundary value problem for the Stokes system in a spherical gap is studied numerically. For R/r exceeding about 30, where r and R are the radii of the inner and outer boundary spheres, it is established that the convergence rate of the method is lower (and considerably lower for large R/r) than the convergence rate of its differential version. For this reason, a really simpler, more slowly converging modification of the original method is constructed on the differential level and a finite-element implementation of this modification is built. Numerical experiments have revealed that this modification has the same convergence rate as its differential counterpart for R/r of up to 5 × 103. When the multigrid method is used to solve the split and auxiliary boundary value problems arising at iterations, the modification is more efficient than the original method starting from R/r ~ 30 and is considerably more efficient for large values of R/r. It is also established that the convergence rates of both methods depend little on the stretching coefficient η of circularly rectangular mesh cells in a range of η that is well sufficient for effective use of the multigrid method for arbitrary values of R/r smaller than ~ 5 × 103. 相似文献
150.
In this paper we derive a priori and a posteriori error estimates for cell centered finite volume approximations of nonlinear conservation laws on polygonal bounded domains. Numerical experiments show the applicability of the a posteriori result for the derivation of local adaptive solution strategies.