全文获取类型
收费全文 | 5359篇 |
免费 | 363篇 |
国内免费 | 731篇 |
专业分类
化学 | 69篇 |
晶体学 | 3篇 |
力学 | 187篇 |
综合类 | 77篇 |
数学 | 5759篇 |
物理学 | 358篇 |
出版年
2024年 | 7篇 |
2023年 | 102篇 |
2022年 | 42篇 |
2021年 | 71篇 |
2020年 | 108篇 |
2019年 | 151篇 |
2018年 | 160篇 |
2017年 | 163篇 |
2016年 | 150篇 |
2015年 | 130篇 |
2014年 | 228篇 |
2013年 | 416篇 |
2012年 | 163篇 |
2011年 | 259篇 |
2010年 | 252篇 |
2009年 | 364篇 |
2008年 | 391篇 |
2007年 | 406篇 |
2006年 | 382篇 |
2005年 | 361篇 |
2004年 | 276篇 |
2003年 | 270篇 |
2002年 | 231篇 |
2001年 | 178篇 |
2000年 | 192篇 |
1999年 | 190篇 |
1998年 | 152篇 |
1997年 | 167篇 |
1996年 | 109篇 |
1995年 | 52篇 |
1994年 | 51篇 |
1993年 | 22篇 |
1992年 | 21篇 |
1991年 | 18篇 |
1990年 | 12篇 |
1989年 | 8篇 |
1988年 | 19篇 |
1987年 | 7篇 |
1986年 | 9篇 |
1985年 | 22篇 |
1984年 | 20篇 |
1983年 | 13篇 |
1982年 | 18篇 |
1981年 | 12篇 |
1980年 | 21篇 |
1979年 | 15篇 |
1978年 | 14篇 |
1977年 | 9篇 |
1976年 | 7篇 |
1974年 | 4篇 |
排序方式: 共有6453条查询结果,搜索用时 78 毫秒
81.
82.
This paper is concerned with nonisentropic hydrodynamic models for two-carrier plasmas, which take the form of Euler equations for conservation laws of mass density, current density and energy density for two-carrier plasmas, coupled to Poisson’s equation for self-consistent electronic field. Due to the nonlinear coupling and cancellation between electrons and ions, the expected dissipation rates of densities for two carriers are no longer available in comparison with the one-carrier case, which leads to the lack of exponential stability near constant equilibrium in the whole space. In order to capture the weaker dissipation and obtain global solutions in spatially critical Besov spaces, calculus techniques which have been recently developed in Chemin–Lerner spaces, will be further applied. 相似文献
83.
A high‐order compact finite‐difference lattice Boltzmann method for simulation of steady and unsteady incompressible flows 下载免费PDF全文
A high‐order compact finite‐difference lattice Boltzmann method (CFDLBM) is proposed and applied to accurately compute steady and unsteady incompressible flows. Herein, the spatial derivatives in the lattice Boltzmann equation are discretized by using the fourth‐order compact FD scheme, and the temporal term is discretized with the fourth‐order Runge–Kutta scheme to provide an accurate and efficient incompressible flow solver. A high‐order spectral‐type low‐pass compact filter is used to stabilize the numerical solution. An iterative initialization procedure is presented and applied to generate consistent initial conditions for the simulation of unsteady flows. A sensitivity study is also conducted to evaluate the effects of grid size, filtering, and procedure of boundary conditions implementation on accuracy and convergence rate of the solution. The accuracy and efficiency of the proposed solution procedure based on the CFDLBM method are also examined by comparison with the classical LBM for different flow conditions. Two test cases considered herein for validating the results of the incompressible steady flows are a two‐dimensional (2‐D) backward‐facing step and a 2‐D cavity at different Reynolds numbers. Results of these steady solutions computed by the CFDLBM are thoroughly compared with those of a compact FD Navier–Stokes flow solver. Three other test cases, namely, a 2‐D Couette flow, the Taylor's vortex problem, and the doubly periodic shear layers, are simulated to investigate the accuracy of the proposed scheme in solving unsteady incompressible flows. Results obtained for these test cases are in good agreement with the analytical solutions and also with the available numerical and experimental results. The study shows that the present solution methodology is robust, efficient, and accurate for solving steady and unsteady incompressible flow problems even at high Reynolds numbers. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
84.
L. Weggler 《Mathematical Methods in the Applied Sciences》2014,37(12):1847-1852
For curvilinear Lipschitz polyhedral domains Ω, explicit characterizations of the tangential trace spaces of H 1(Ω) are presented. These extend the original characterizations given by Buffa and Ciarlet that hold on Lipschitz polyhedral domains with plane faces. The tangential trace spaces of H 1(Ω) are fundamental for the definition, analysis and intuitive understanding of the trace spaces of H ( curl ,Ω) and therefore, more general characterizations of the latter are obtained at the same time. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
85.
Let K and S be locally compact Hausdorff spaces and let X be a strictly convex Banach space of finite dimension at least 2. In this paper, we prove that if there exists an isomorphism T from onto satisfying then K and S are homeomorphic. Here denotes the Schäffer constant of X. Even for the classical cases , and , this result is the X‐valued Banach–Stone theorem via isomorphism with the largest distortion that is known so far, namely . On the other hand, it is well known that this result is not true for , even though K and S are compact Hausdorff spaces. 相似文献
86.
We prove that a WLD subspace of the space consisting of all bounded, countably supported functions on a set Γ embeds isomorphically into if and only if it does not contain isometric copies of . Moreover, a subspace of is constructed that has an unconditional basis, does not embed into , and whose every weakly compact subset is separable (in particular, it cannot contain any isomorphic copies of ). 相似文献
87.
88.
89.
Merve lkhan 《Mathematical Methods in the Applied Sciences》2019,42(16):5143-5153
Norm of an operator T:X→Y is the best possible value of U satisfying the inequality and lower bound for T is the value of L satisfying the inequality where ‖.‖X and ‖.‖Y are the norms on the spaces X and Y, respectively. The main goal of this paper is to compute norms and lower bounds for some matrix operators from the weighted sequence space ?p(w) into a new space called as Fibonacci weighted difference sequence space. For this purpose, we firstly introduce the Fibonacci difference matrix and the space consisting of sequences whose ‐transforms are in . 相似文献
90.
Güllü Canan Hazar Güle 《Mathematical Methods in the Applied Sciences》2019,42(16):5398-5402
By , we denote the set of all sequences such that Σ?nan is summable V whenever Σan is summable U, where U and V are two summability methods. Recently, Sar?göl has characterized the set for k > 1,α > ?1 and arbitrary positive sequences Now, in the present paper, we characterize the sets , k > 1 and , k ≥ 1 for arbitrary positive sequences Hence we extend these results to the range α≥ ? 1. In this way, some open problems in this topic are also completed. 相似文献