全文获取类型
收费全文 | 14810篇 |
免费 | 1853篇 |
国内免费 | 733篇 |
专业分类
化学 | 6309篇 |
晶体学 | 52篇 |
力学 | 1253篇 |
综合类 | 54篇 |
数学 | 5569篇 |
物理学 | 4159篇 |
出版年
2024年 | 19篇 |
2023年 | 169篇 |
2022年 | 203篇 |
2021年 | 288篇 |
2020年 | 468篇 |
2019年 | 377篇 |
2018年 | 388篇 |
2017年 | 356篇 |
2016年 | 620篇 |
2015年 | 579篇 |
2014年 | 745篇 |
2013年 | 1373篇 |
2012年 | 839篇 |
2011年 | 860篇 |
2010年 | 638篇 |
2009年 | 907篇 |
2008年 | 875篇 |
2007年 | 947篇 |
2006年 | 805篇 |
2005年 | 626篇 |
2004年 | 605篇 |
2003年 | 573篇 |
2002年 | 483篇 |
2001年 | 474篇 |
2000年 | 429篇 |
1999年 | 346篇 |
1998年 | 354篇 |
1997年 | 272篇 |
1996年 | 270篇 |
1995年 | 203篇 |
1994年 | 166篇 |
1993年 | 154篇 |
1992年 | 99篇 |
1991年 | 100篇 |
1990年 | 82篇 |
1989年 | 68篇 |
1988年 | 72篇 |
1987年 | 49篇 |
1986年 | 86篇 |
1985年 | 45篇 |
1984年 | 57篇 |
1983年 | 19篇 |
1982年 | 36篇 |
1981年 | 32篇 |
1980年 | 20篇 |
1979年 | 26篇 |
1978年 | 43篇 |
1977年 | 43篇 |
1976年 | 43篇 |
1974年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
Madhu V. Nayakkankuppam 《Mathematical Programming》2007,109(2-3):477-504
We describe an approach to the parallel and distributed solution of large-scale, block structured semidefinite programs using
the spectral bundle method. Various elements of this approach (such as data distribution, an implicitly restarted Lanczos
method tailored to handle block diagonal structure, a mixed polyhedral-semidefinite subdifferential model, and other aspects
related to parallelism) are combined in an implementation called LAMBDA, which delivers faster solution times than previously
possible, and acceptable parallel scalability on sufficiently large problems.
This work was supported in part by NSF grants DMS-0215373 and DMS-0238008. 相似文献
72.
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
73.
A generalized inverse problem for the identification of the absorption coefficient for a hyperbolic system is considered. The well-posedness of the problem is examined. It is proved that the regular part of the solution is an L 2 function, which reduces the inverse problem to minimizing the error functional. The gradient of the functional is determined in explicit form from the adjoint problem, and approximate formulas for its calculation are derived. A regularization algorithm for the solution of the inverse problem is considered. Numerical results obtained for various excitation sources are displayed. 相似文献
74.
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
75.
Enantioselective biocatalysis in nonaqueous media is becoming increasingly important in preparative synthetic chemistry. This article discusses (1) the general catalytic properties of enzymes in nonaqueous environments, (2) the basic principles that govern lipase-catalyzed enantioselective esterification and transesterification reactions in organic media for the preparation of optically active acids and alcohols, (3) the determination of kinetic and thermodynamic parameters, and (4) the quantitative analysis of published data. 相似文献
76.
Applied Biochemistry and Biotechnology - 相似文献
77.
本文讨论了一类Rosenbrock方法求解比例延迟微分方程,y′(t)=λy(t) μy(qt),λ,μ∈C,0 相似文献
78.
采用Monte Carlo模拟方法研究了多嵌段聚合物在A/B/嵌段聚合物三组份体系作为相容剂使用的有效性.占总体积19%的A组份在体系中为分散相.模拟结果显示了两嵌段和多嵌段聚合物在界面上的聚集行为,以及如何影响这个不相容体系的相形为.两嵌段聚合物趋于直立在相界面上,而多嵌段聚合物更容易横跨在相界面上并占据较大的界面积.从而导致多嵌段聚合物更有效的阻止体系相分离的发生. 相似文献
79.
Jeannette Van Iseghem 《Numerical Algorithms》2002,29(1-3):267-279
A method for solving a linear system is defined. It is a Lanczos-type method, but it uses formal vector orthogonality instead of scalar orthogonality. Moreover, the dimension of vector orthogonality may vary which gives a large freedom in leading the algorithm, and controlling the numerical problems. The ideas of truncated and restarted methods are revisited. The obtained residuals are exactly orthogonal to a space of increasing dimension. Some experiments are done, the problem of finding automaticaly good directions of projection remains partly open. 相似文献
80.
We construct weighted modifications of statistical modeling of an ensemble of interacting particles which is connected with approximate solution of a nonlinear Boltzmann equation. 相似文献