全文获取类型
收费全文 | 29543篇 |
免费 | 3494篇 |
国内免费 | 1977篇 |
专业分类
化学 | 1887篇 |
晶体学 | 18篇 |
力学 | 3335篇 |
综合类 | 427篇 |
数学 | 20964篇 |
物理学 | 8383篇 |
出版年
2024年 | 41篇 |
2023年 | 281篇 |
2022年 | 303篇 |
2021年 | 437篇 |
2020年 | 872篇 |
2019年 | 846篇 |
2018年 | 796篇 |
2017年 | 748篇 |
2016年 | 869篇 |
2015年 | 704篇 |
2014年 | 1317篇 |
2013年 | 2545篇 |
2012年 | 1453篇 |
2011年 | 1811篇 |
2010年 | 1743篇 |
2009年 | 1933篇 |
2008年 | 2017篇 |
2007年 | 1981篇 |
2006年 | 1685篇 |
2005年 | 1670篇 |
2004年 | 1387篇 |
2003年 | 1345篇 |
2002年 | 1152篇 |
2001年 | 894篇 |
2000年 | 818篇 |
1999年 | 795篇 |
1998年 | 740篇 |
1997年 | 606篇 |
1996年 | 487篇 |
1995年 | 398篇 |
1994年 | 343篇 |
1993年 | 231篇 |
1992年 | 220篇 |
1991年 | 220篇 |
1990年 | 185篇 |
1989年 | 109篇 |
1988年 | 109篇 |
1987年 | 104篇 |
1986年 | 107篇 |
1985年 | 103篇 |
1984年 | 94篇 |
1983年 | 52篇 |
1982年 | 95篇 |
1981年 | 80篇 |
1980年 | 61篇 |
1979年 | 56篇 |
1978年 | 37篇 |
1977年 | 33篇 |
1976年 | 24篇 |
1973年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
Yuhua Long 《Journal of Difference Equations and Applications》2020,26(7):966-986
In the present paper, we apply the method of invariant sets of descending flow to establish a series of criteria to ensure that a second-order nonlinear functional difference equation with periodic boundary conditions possesses at least one trivial solution and three nontrivial solutions. These nontrivial solutions consist of sign-changing solutions, positive solutions and negative solutions. Moreover, as an application of our theoretical results, an example is elaborated. Our results generalize and improve some existing ones. 相似文献
22.
23.
Transformation hydrodynamics and the corresponding metamaterials have been proposed as a means to exclude the drag force acting on an object. Here, we report a strategy to deploy the hydrodynamic cloaks in a more practical manner by assembling different-shaped cloaking parts. Our strategy is to first model a square-shaped cloak and a carpet cloak and then combine them to conceal a more complex-shaped space in the three-dimensional hydrodynamic flow. With the derivation of transformation hydrodynamics, the coordinate transformations for each hydrodynamic cloaking are demonstrated with the calculated viscosity tensors. The pressure and velocity fields of the square, triangular (carpet), and exemplary three-dimensional house-shaped cloaks are numerically simulated, thus showing a cloaking effect and reduced drag. This study suggests an efficient way of cloaking complex architectures from fluid-dynamic forces. 相似文献
24.
Existence and Uniqueness of Solution for a Class of Nonlinear Degenerate Elliptic Equations 下载免费PDF全文
Albo Carlos Cavalheiro 《分析论及其应用》2020,36(1):69-88
In this work we are interested in the existence and uniqueness of solutions for the Navier problem associated to the degenerate nonlinear elliptic equations■,in the setting of the weighted Sobolev spaces. 相似文献
25.
Michele Colturato 《Mathematical Methods in the Applied Sciences》2020,43(10):6598-6626
We consider the sliding mode control (SMC) problem for a diffuse interface tumor growth model coupling a Cahn–Hilliard equation with a reaction–diffusion equation perturbed by a maximal monotone nonlinearity. We prove existence and regularity of strong solutions and, under further assumptions, a uniqueness result. Then, we show that the chosen SMC law forces the system to reach within finite time a sliding manifold that we chose in order that the tumor phase remains constant in time. 相似文献
26.
27.
Weiliang Xiao & Xuhuan Zhou 《数学研究》2020,53(3):316-328
We study a kind of generalized porous medium equation with fractional Laplacian and abstract pressure term. For a large class of equations corresponding to the form: $u_t+\nu \Lambda^{\beta}u=\nabla\cdot(u\nabla Pu)$, we get their local well-posedness in Fourier-Besov spaces for large initial data. If the initial data is small, then the solution becomes global. Furthermore, we prove a blowup criterion for the solutions. 相似文献
28.
29.
30.
《Wave Motion》2020
We review work of Jordan on a hyperbolic variant of the Fisher–KPP equation, where a shock solution is found and the amplitude is calculated exactly. The Jordan procedure is extended to a hyperbolic variant of the Chafee–Infante equation. Extension of Jordan’s ideas to a model for traffic flow are also mentioned. We also examine a diffusive susceptible–infected (SI) model, and generalizations of diffusive Lotka–Volterra equations, including a Lotka–Volterra–Bass competition model with diffusion. For all cases we show how a Jordan–Cattaneo wave may be analysed and we indicate how to find the wavespeeds and the amplitudes. Finally we present details of a fully nonlinear analysis of acceleration waves in a Cattaneo–Christov poroacoustic model. 相似文献