全文获取类型
收费全文 | 21977篇 |
免费 | 1878篇 |
国内免费 | 1099篇 |
专业分类
化学 | 2020篇 |
晶体学 | 92篇 |
力学 | 3264篇 |
综合类 | 157篇 |
数学 | 13541篇 |
物理学 | 5880篇 |
出版年
2024年 | 38篇 |
2023年 | 213篇 |
2022年 | 233篇 |
2021年 | 392篇 |
2020年 | 606篇 |
2019年 | 560篇 |
2018年 | 586篇 |
2017年 | 584篇 |
2016年 | 531篇 |
2015年 | 517篇 |
2014年 | 841篇 |
2013年 | 2266篇 |
2012年 | 910篇 |
2011年 | 1306篇 |
2010年 | 1023篇 |
2009年 | 1372篇 |
2008年 | 1326篇 |
2007年 | 1282篇 |
2006年 | 1202篇 |
2005年 | 958篇 |
2004年 | 898篇 |
2003年 | 873篇 |
2002年 | 852篇 |
2001年 | 664篇 |
2000年 | 677篇 |
1999年 | 567篇 |
1998年 | 542篇 |
1997年 | 501篇 |
1996年 | 378篇 |
1995年 | 273篇 |
1994年 | 253篇 |
1993年 | 204篇 |
1992年 | 185篇 |
1991年 | 127篇 |
1990年 | 129篇 |
1989年 | 89篇 |
1988年 | 80篇 |
1987年 | 69篇 |
1986年 | 65篇 |
1985年 | 100篇 |
1984年 | 123篇 |
1983年 | 59篇 |
1982年 | 91篇 |
1981年 | 76篇 |
1980年 | 69篇 |
1979年 | 65篇 |
1978年 | 67篇 |
1977年 | 38篇 |
1976年 | 34篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
We study the behaviour of a conjugate gradient Uzawa-type method for a stabilized finite element approximation of the Stokes problem. Many variants of the Uzawa algorithm have been described for different finite elements satisfying the well-known Inf-Sup condition of Babu?ka and Brezzi, but it is surprising that developments for unstable ‘low-order’ discretizations with stabilization procedures are still missing. Our paper is presented in this context for the popular (so-called) Q1–P0 element. First we show that a simple stabilization technique for this element permits us to retain the property of a convergence factor bounded independently of the discretization mesh size. The second contribution of this work deals with the construction of a less costly preconditioner taking full advantages of the block diagonal structure of the stabilization matrix. Its efficiency is supported by 2D and. 3D numerical results. 相似文献
993.
Roland Hunt 《国际流体数值方法杂志》1992,14(5):539-556
The numerical solution of the thin film flow surrounding a horizontal cylinder resulting from a single vertical cylindrical jet is obtained. This is effected by transforming the domain of the flow, which contains a free surface, onto a rectangular parallelepiped and using a marching strategy to solve the ensuing parabolic equations. The flow terminates at a finite distance along the cylinder, its position depending on the velocity and mass flux of the jet. A comparison with the usual two-dimensional model in which the jet is replaced by a vertical sheet shows that such a representation is valid provided the overall width of the flow is not too large. In particular, the differences in heat transfer characteristics amount to a few per cent, thus validating the use of the two-dimensional model when applied to heat exchanger tubes. A comparison with the more usual multicolumn case is also considered. 相似文献
994.
Poisson跳的拟线性倒向随机微分方程x(t) ∫tf(s,x(s),,x(s)) y(s)]dMs =ξ,t∈[0,1],这里M = (W,Q)T,其中W为Wiener过程,Q为补偿Poisson过程.利用区间延拓和 Bihari 不等式证明了在某种弱于Lipschitz条件下方程存在唯一适应解,并给出了解的估计,从而将文章[1]的结论推广到带 Poission 跳的情形.另外,本文还讨论了以下形式的边值问题:dx(t) = f(t,x(t),y(t))dt y(t)dMt,Ax(0) Bx(1) =ξ*,t∈[0,1],并证明了在Lipschitz条件下适应解的存在唯一性. 相似文献
995.
An extended hyperbola function method is proposed to construct exact solitary wave solutions to nonlinear wave equation based upon a coupled Riccati equation. It is shown that more new solitary wave solutions can be found by this new method, which include kink-shaped soliton solutions, bell-shaped soliton solutions and new solitary wave.The new method can be applied to other nonlinear equations in mathematical physics. 相似文献
996.
In this paper we study the oscillations for a class of functional differential inequalities. By using these properties some forced oscillations to the boundary value problems of functional partial differential equations are established. 相似文献
997.
We investigate neutron star properties by constructing a chiral SU(3) spontaneous breaking Lagrangian and using relativistic mean-field approximation. The results show that π- condensate appears at some baryon densities,and hyperons ∑- and A exist in neutron star matter at high density. In this model, neutron star's maximum mass is1.12Ms with corresponding radius about 8 km. 相似文献
998.
We study local convergence of quasi-Newton methods for solving systems of nonlinear equations defined by B-differentiable functions. We extend the classical linear and superlinear convergence results for general quasi-Newton methods as well as for Broyden's method. We also show how Broyden's method may be applied to nonlinear complementarity problems and illustrate its computational performance on two small examples. 相似文献
999.
Summary Analytic results for electronic kinetic energy are first presented for a hydrogen atom in a spherical cage for two radii near
to the corresponding densities employed in the path-integral Monte Carlo study of isochoric molecular dissociation in dense
hydrogen by Magroet al. (Magro W. R., Ceperley D. M., Pierleoni C. andBernu B.,Phys. Rev. Lett.,76 (1996) 1240). The relevance of the ?cage? results to the behaviour of dense atomic hydrogen is pointed out. Attention is
then shifted to the molecular regime, and the variation with density of electronic kinetic energy for a H2 molecule in a rigid spheroidal cage is compared and contrasted with the Monte Carlo findings. The rigid-cage model mimics
this, as well as bond length contraction, under compression. 相似文献
1000.
Asymptotic normality of the solutions of the initial-value problems for multidimensional Burgers' equation with weakly dependent possible non-Gaussian initial condition is proved. 相似文献