全文获取类型
收费全文 | 10848篇 |
免费 | 877篇 |
国内免费 | 1046篇 |
专业分类
化学 | 7002篇 |
晶体学 | 39篇 |
力学 | 861篇 |
综合类 | 92篇 |
数学 | 3006篇 |
物理学 | 1771篇 |
出版年
2024年 | 29篇 |
2023年 | 130篇 |
2022年 | 220篇 |
2021年 | 268篇 |
2020年 | 405篇 |
2019年 | 320篇 |
2018年 | 308篇 |
2017年 | 351篇 |
2016年 | 420篇 |
2015年 | 340篇 |
2014年 | 455篇 |
2013年 | 936篇 |
2012年 | 516篇 |
2011年 | 536篇 |
2010年 | 464篇 |
2009年 | 658篇 |
2008年 | 614篇 |
2007年 | 614篇 |
2006年 | 585篇 |
2005年 | 528篇 |
2004年 | 522篇 |
2003年 | 407篇 |
2002年 | 330篇 |
2001年 | 280篇 |
2000年 | 299篇 |
1999年 | 255篇 |
1998年 | 251篇 |
1997年 | 229篇 |
1996年 | 192篇 |
1995年 | 167篇 |
1994年 | 160篇 |
1993年 | 127篇 |
1992年 | 129篇 |
1991年 | 108篇 |
1990年 | 90篇 |
1989年 | 74篇 |
1988年 | 60篇 |
1987年 | 52篇 |
1986年 | 46篇 |
1985年 | 29篇 |
1984年 | 39篇 |
1983年 | 21篇 |
1982年 | 35篇 |
1981年 | 33篇 |
1980年 | 36篇 |
1979年 | 36篇 |
1978年 | 24篇 |
1977年 | 12篇 |
1976年 | 15篇 |
1974年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
61.
Eric Flauraud Frdric Nataf Isabelle Faille Roland Masson 《Comptes Rendus Mecanique》2003,331(12):849-855
We present in this paper a domain decomposition method to treat faults in geological basin modeling. The particularity of this model is that the faults whose widths are very small in comparison with the basin size, are not characterized as subdomains any more but as interfaces between sedimentary blocks. The originality of this work lies in the formulation of this new fault model and in the definition and the computation of the interface conditions between the subdomains. To cite this article: E. Flauraud et al., C. R. Mecanique 331 (2003). 相似文献
62.
63.
An extremum problem is embedded in a parametric scheme which contains, as a particular case, the classic perturbation function. The introduction of the image of the embedded problem allows one to derive a generalized duality and, in particular, Lagrangian and Fenchel duality. 相似文献
64.
Ansgar Jüngel 《Mathematische Nachrichten》1997,185(1):85-110
A multi-dimensional transient drift-diffusion model for (at most) three charged particles, consisting of the continuity equations for the concentrations of the species and the Poisson equation for the electric potential, is considered. The diffusion terms depend on the concentrations. Such a system arises in electrophoretic modeling of three species (neutrally, positively and negatively charged) and in semiconductor theory for two species (positively charged holes and negatively charged electrons). Diffusion terms of degenerate type are also possible in semiconductor modeling. For the initial boundary value problem with mixed Dirichlet - Neumann boundary conditions and general reaction rates, a global existence result is proved. Uniqueness of solutions follows in the Dirichlet boundary case if the diffusion terms are uniformly parabolic or if the initial and boundary densities are strictly positive. Finally, we prove that solutions exist which are positive uniformly in time and globally bounded if the reaction rates satisfy appropriate growth conditions. 相似文献
65.
66.
67.
Poly (n-butylisocyanate)-benzene solutions prepared by solubilization at 45°C, followed by aging at room temperature were found to be metastable for months, although, eventually, they separated into a birefringent polymer-rich phase and an isotropic solution. These metastable solutions, as well as isothermally phase-separated biphasic samples, flowed and exhibited dynamic moduli indicative of low polymer connectivity. By contrast samples prepared by a freeze-thaw cycle were uniformly and highly birefringent and showed network (gel) behavior at room temperature. The mechanism of gel formation is most likely the exclusion of the polymer from the benzene crystal during crystallization, forcing the polymer to align and exist at grain boundaries. Films formed from solutions have different moduli than those formed from gels, and are consistent with the proposed mechanism. 相似文献
68.
The Stokes motions of three-dimensional screw-sensed slender particles in a homogeneous shear field are investigated, including the effects of buoyancy. Conclusions are drawn about the possibility of achieving a separation of mixtures of right- and left-handed particles. The linearity of the Stokes equations allows complex flows to be solved by adding the effects of the several terms which describe the flow in which the particle is immersed. The homogeneous shear flow considered here consists of three such terms; solutions for a series of 12 unit motions are sufficient to determine the hydrodynamic resistance tensors. The forces and torques experienced by screw-sensed particles are calculated from these 51 resistance tensors, using slender-filament theory. The results allow an estimate of the range of buoyancy parameters for which gravitational sedimentation can be neglected. The fundamental component of the particle motion is a rotation, at approximately the same angular velocity as that of the fluid. Superimposed on this are variations, of large period, in the particle orientation. A phase plane analysis is used to find the terminal orientations. Very long calculation times are required for the phase portrait. An approximate method based on azimuthally-averaged equations is developed to avoid the requirements for long time integration. 相似文献
69.
具有非局部边界条件的奇摄动反应扩散问题 总被引:2,自引:0,他引:2
本文研究了一类具有非局部边界条件的奇摄动反应扩散初始边值问题.在适当的条件下,利用比较定理讨论了问题解的渐近性态. 相似文献
70.
Bernard Bialecki 《Numerical Algorithms》1994,8(2):167-184
Cyclic reduction and Fourier analysis-cyclic reduction (FACR) methods are presented for the solution of the linear systems which arise when orthogonal spline collocation with piecewise Hermite bicubics is applied to boundary value problems for certain separable partial differential equations on a rectangle. On anN×N uniform partition, the cyclic reduction and Fourier analysis-cyclic reduction methods requireO(N
2log2
N) andO(N
2log2log2
N) arithmetic operations, respectively. 相似文献