全文获取类型
收费全文 | 19495篇 |
免费 | 1363篇 |
国内免费 | 1237篇 |
专业分类
化学 | 905篇 |
晶体学 | 26篇 |
力学 | 1716篇 |
综合类 | 279篇 |
数学 | 17149篇 |
物理学 | 2020篇 |
出版年
2024年 | 33篇 |
2023年 | 179篇 |
2022年 | 286篇 |
2021年 | 341篇 |
2020年 | 427篇 |
2019年 | 464篇 |
2018年 | 476篇 |
2017年 | 545篇 |
2016年 | 548篇 |
2015年 | 384篇 |
2014年 | 854篇 |
2013年 | 1544篇 |
2012年 | 881篇 |
2011年 | 1045篇 |
2010年 | 917篇 |
2009年 | 1272篇 |
2008年 | 1325篇 |
2007年 | 1366篇 |
2006年 | 1168篇 |
2005年 | 947篇 |
2004年 | 840篇 |
2003年 | 853篇 |
2002年 | 759篇 |
2001年 | 605篇 |
2000年 | 588篇 |
1999年 | 515篇 |
1998年 | 492篇 |
1997年 | 437篇 |
1996年 | 353篇 |
1995年 | 267篇 |
1994年 | 194篇 |
1993年 | 162篇 |
1992年 | 142篇 |
1991年 | 134篇 |
1990年 | 108篇 |
1989年 | 58篇 |
1988年 | 57篇 |
1987年 | 56篇 |
1986年 | 52篇 |
1985年 | 77篇 |
1984年 | 73篇 |
1983年 | 51篇 |
1982年 | 43篇 |
1981年 | 41篇 |
1980年 | 38篇 |
1979年 | 28篇 |
1978年 | 24篇 |
1977年 | 17篇 |
1976年 | 9篇 |
1974年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Chu-Li Fu Xiang-Tuan Xiong Zhi Qian 《Journal of Mathematical Analysis and Applications》2007,331(1):472-480
In this paper a simple and convenient new regularization method for solving backward heat equation—Fourier regularization method is given. Meanwhile, some quite sharp error estimates between the approximate solution and exact solution are provided. A numerical example also shows that the method works effectively. 相似文献
82.
Noureddine Igbida 《Journal of Mathematical Analysis and Applications》2007,335(2):1061-1078
In this paper, we study the nonlinear evolution equation of Hele-Shaw type with dynamical boundary conditions. That is, the equation ut=Δw+f where u∈H(w) and H is the Heaviside function, with boundary condition μ(x,w)t∂w+k∇w⋅ν=g, where ν denotes the outward normal vector of the fixed boundary of the domain. We prove existence, uniqueness and some qualitative properties of the solution. 相似文献
83.
Wuqing Ning 《Journal of Mathematical Analysis and Applications》2007,327(2):1396-1419
In this paper, an algorithm is established to reconstruct an eigenvalue problem from the given data satisfying certain conditions. These conditions are proved to be not only necessary but also sufficient for the given data to coincide with the spectral characteristics corresponding to the reconstructed eigenvalue problem. 相似文献
84.
N. E. Tovmasyan H. A. Babayan 《Journal of Contemporary Mathematical Analysis (Armenian Academy of Sciences)》2007,42(4):198-204
The paper establishes some solvability conditions of the Cauchy problem for linear differential equation in the class of monotone increasing functions. The results are applied for clarifying the possibility of flight along a given trajectory under existence of braking forces. 相似文献
85.
We study the generalization of the Willmore functional for surfaces in the three-dimensional Heisenberg group. Its construction is based on the spectral theory of the Dirac operator entering into theWeierstrass representation of surfaces in this group. Using the surfaces of revolution we demonstrate that the generalization resembles the Willmore functional for the surfaces in the Euclidean space in many geometrical aspects. We also observe the relation of these functionals to the isoperimetric problem. 相似文献
86.
This paper discusses a class of second-order derivative nonlinear Schrödinger equations which are used to describe the upper-hybrid oscillation propagation. By establishing a variational problem, applying the potential well argument and the concavity method, we prove that there exists a sharp condition for global existence and blow-up of the solutions to the nonlinear Schrödinger equation. In addition, we also answer the question: how small are the initial data, the global solutions exist? 相似文献
87.
Veli B. Shakhmurov 《Journal of Mathematical Analysis and Applications》2007,327(2):1182-1201
The nonlocal boundary value problems for anisotropic partial differential-operator equations with a dependent coefficients are studied. The principal parts of the appropriate generated differential operators are nonself-adjoint. Several conditions for the maximal regularity and the fredholmness in Banach-valued Lp-spaces of these problems are given. These results permit us to establish that the inverse of corresponding differential operators belongs to Schatten q-class. Some spectral properties of the operators are investigated. In applications, the nonlocal BVP's for quasielliptic partial differential equations and for systems of quasielliptic equations on cylindrical domain are studied. 相似文献
88.
Ch. Tsitouras 《Numerical Algorithms》2007,44(3):291-307
Runge–Kutta (RK) pairs furnish approximations of the solution of an initial value problem at discrete points in the interval
of integration. Many techniques for enriching these methods with continuous approximations have been proposed. Here we construct
C
1 continuous, eighth and ninth order interpolation methods for a recently appeared RK pair of orders 9(8). These interpolants
share a very small leading truncation error making them suitable for use at quadruple precision, i.e. 32–33 decimal digits
of accuracy. Extended numerical results justify our effort. 相似文献
89.
The parallel version of precondition techniques is developed for matrices arising from the Galerkin boundary element method for two-dimensional domains with Dirichlet boundary conditions. Results were obtained for implementations on a transputer network as well as on an nCUBE-2 parallel computer showing that iterative solution methods are very well suited for a MIMD computer. A comparison of numerical results for iterative and direct solution methods is presented and underlines the superiority of iterative methods for large systems. 相似文献
90.
无穷区间上二阶微分方程的边值问题 总被引:5,自引:0,他引:5
刘衍胜 《应用泛函分析学报》2002,4(3):211-216
利用Schauder不动点定理讨论了一类非线性二阶微分方程在无穷区间上的边值问题无界解的存在性,部分改进了郭大钧教授最近得到的结果。 相似文献