全文获取类型
收费全文 | 33145篇 |
免费 | 3410篇 |
国内免费 | 1987篇 |
专业分类
化学 | 2359篇 |
晶体学 | 57篇 |
力学 | 4080篇 |
综合类 | 323篇 |
数学 | 21964篇 |
物理学 | 9759篇 |
出版年
2024年 | 62篇 |
2023年 | 328篇 |
2022年 | 330篇 |
2021年 | 472篇 |
2020年 | 906篇 |
2019年 | 895篇 |
2018年 | 839篇 |
2017年 | 800篇 |
2016年 | 915篇 |
2015年 | 784篇 |
2014年 | 1514篇 |
2013年 | 2840篇 |
2012年 | 1567篇 |
2011年 | 2058篇 |
2010年 | 1923篇 |
2009年 | 2123篇 |
2008年 | 2270篇 |
2007年 | 2226篇 |
2006年 | 1792篇 |
2005年 | 1732篇 |
2004年 | 1478篇 |
2003年 | 1401篇 |
2002年 | 1224篇 |
2001年 | 941篇 |
2000年 | 952篇 |
1999年 | 882篇 |
1998年 | 825篇 |
1997年 | 701篇 |
1996年 | 540篇 |
1995年 | 483篇 |
1994年 | 397篇 |
1993年 | 269篇 |
1992年 | 243篇 |
1991年 | 235篇 |
1990年 | 210篇 |
1989年 | 119篇 |
1988年 | 117篇 |
1987年 | 116篇 |
1986年 | 130篇 |
1985年 | 127篇 |
1984年 | 119篇 |
1983年 | 66篇 |
1982年 | 115篇 |
1981年 | 95篇 |
1980年 | 78篇 |
1979年 | 87篇 |
1978年 | 57篇 |
1977年 | 49篇 |
1976年 | 30篇 |
1973年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
921.
First, by using linear and trilinear estimates in Bourgain type analytic and Gevrey spaces, the local well‐posedness of the Cauchy problem for the modified Kawahara equation on the line is established for analytic initial data that can be extended as holomorphic functions in a strip around the x‐axis. Next we use this local result and a Gevrey approximate conservation law to prove that global solutions exist. Furthermore, we obtain explicit lower bounds for the radius of spatial analyticity given by , where can be taken arbitrarily small and c is a positive constant. 相似文献
922.
923.
In this article, we consider the initial boundary value problem for a class of nonlinear pseudo‐parabolic equations with a memory term: Under suitable assumptions, we obtain the local and global existence of the solution by Galerkin method. We prove finite‐time blow‐up of the solution for initial data at arbitrary energy level and obtain upper bounds for blow‐up time by using the concavity method. In addition, by means of differential inequality technique, we obtain a lower bound for blow‐up time of the solution if blow‐up occurs. 相似文献
924.
925.
J. Chevallier A. Duarte E. Löcherbach G. Ost 《Stochastic Processes and their Applications》2019,129(1):1-27
We consider spatially extended systems of interacting nonlinear Hawkes processes modeling large systems of neurons placed in and study the associated mean field limits. As the total number of neurons tends to infinity, we prove that the evolution of a typical neuron, attached to a given spatial position, can be described by a nonlinear limit differential equation driven by a Poisson random measure. The limit process is described by a neural field equation. As a consequence, we provide a rigorous derivation of the neural field equation based on a thorough mean field analysis. 相似文献
926.
We describe the indecomposable involutive non-degenerate set-theoretic solutions of the Yang–Baxter equation as dynamical extensions of non-degenerate left cycle sets. Moreover we characterize the indecomposable dynamical extensions and we produce several examples. As an application we construct a family of finite indecomposable solutions whose structure groups have not the unique product property. 相似文献
927.
Stevo Stevi Bratislav Iri
anin Witold Kosmala Zdenk marda 《Mathematical Methods in the Applied Sciences》2019,42(5):1687-1701
Some formulas for well‐defined solutions to four very special cases of a nonlinear fifth‐order difference equation have been presented recently in this journal, where some of them were proved by the method of induction, some are only quoted, and no any theory behind the formulas was given. Here, we show in an elegant constructive way how the general solution to the difference equation can be obtained, from which the special cases very easily follow, which is also demonstrated here. We also give some comments on the local stability results on the special cases of the nonlinear fifth‐order difference equation previously publish in this journal. 相似文献
928.
In this paper, an unstable linear time invariant (LTI) ODE system is stabilized exponentially by the PDE compensato—a wave equation with Kelvin‐Voigt (K‐V) damping. Direct feedback connections between the ODE system and wave equation are established: The velocity of the wave equation enters the ODE through the variable vt(1,t); meanwhile, the output of the ODE is fluxed into the wave equation. It is found that the spectrum of the system operator is composed of two parts: point spectrum and continuous spectrum. The continuous spectrum consists of an isolated point , and there are two branches of asymptotic eigenvalues: the first branch approaches to , and the other branch tends to ?∞. It is shown that there is a sequence of generalized eigenfunctions, which forms a Riesz basis for the Hilbert state space. As a consequence, the spectrum‐determined growth condition and exponential stability of the system are concluded. 相似文献
929.
Claudianor O. Alves Daniel C. de Morais Filho Giovany M. Figueiredo 《Mathematical Methods in the Applied Sciences》2019,42(14):4862-4875
In this work, we prove the existence of positive solution for the following class of problems where λ>0 and is a potential satisfying some conditions. Using the variational method developed by Szulkin for functionals, which are the sum of a C1 functional with a convex lower semicontinuous functional, we prove that for each large enough λ>0, there exists a positive solution for the problem, and that, as λ→+∞, such solutions converge to a positive solution of the limit problem defined on the domain Ω=int(V?1({0})). 相似文献
930.
ABSTRACTA class of semilinear parabolic reaction diffusion equations with multiple time delays is considered. These time delays and corresponding weights are to be optimized such that the associated solution of the delay equation is the best approximation of a desired state function. The differentiability of the mapping is proved that associates the solution of the delay equation to the vector of weights and delays. Based on an adjoint calculus, first-order necessary optimality conditions are derived. Numerical test examples show the applicability of the concept of optimizing time delays. 相似文献