全文获取类型
收费全文 | 5586篇 |
免费 | 653篇 |
国内免费 | 501篇 |
专业分类
化学 | 134篇 |
晶体学 | 2篇 |
力学 | 898篇 |
综合类 | 128篇 |
数学 | 4447篇 |
物理学 | 1131篇 |
出版年
2024年 | 10篇 |
2023年 | 67篇 |
2022年 | 68篇 |
2021年 | 98篇 |
2020年 | 120篇 |
2019年 | 157篇 |
2018年 | 161篇 |
2017年 | 158篇 |
2016年 | 186篇 |
2015年 | 125篇 |
2014年 | 210篇 |
2013年 | 482篇 |
2012年 | 228篇 |
2011年 | 247篇 |
2010年 | 255篇 |
2009年 | 304篇 |
2008年 | 360篇 |
2007年 | 403篇 |
2006年 | 365篇 |
2005年 | 302篇 |
2004年 | 268篇 |
2003年 | 294篇 |
2002年 | 272篇 |
2001年 | 203篇 |
2000年 | 200篇 |
1999年 | 189篇 |
1998年 | 176篇 |
1997年 | 176篇 |
1996年 | 108篇 |
1995年 | 96篇 |
1994年 | 58篇 |
1993年 | 55篇 |
1992年 | 50篇 |
1991年 | 47篇 |
1990年 | 35篇 |
1989年 | 25篇 |
1988年 | 27篇 |
1987年 | 28篇 |
1986年 | 19篇 |
1985年 | 19篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 14篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 14篇 |
1977年 | 4篇 |
1976年 | 10篇 |
1975年 | 2篇 |
排序方式: 共有6740条查询结果,搜索用时 421 毫秒
41.
Adrian Vasiu 《Central European Journal of Mathematics》2005,3(1):14-25
We include short and elementary proofs of two theorems that characterize reductive group schemes over a discrete valuation
ring, in a slightly more general context. 相似文献
42.
This work is devoted to near-optimal controls of large-scale discrete-time nonlinear dynamic systems driven by Markov chains; the underlying problem is to minimize an expected cost function. Our main goal is to reduce the complexity of the underlying systems. To achieve this goal, discrete-time control models under singularly-perturbed Markov chains are introduced. Using a relaxed control representation, our effort is devoted to finding near-optimal controls. Lumping the states in each irreducible class into a single state gives rise to a limit system. Applying near-optimal controls of the limit system to the original system, near-optimal controls of the original system are derived. 相似文献
43.
王梦 《浙江大学学报(理学版)》2003,30(4):361-364
用旋转法结合Fourier估计以及Littlewood-Paley理论给出了乘积空间上带粗糙核的极大奇异积分算子的Lp有界性.证明了对于Ω∈Lq(Sn-1×Sm1),其中q>1,∫ sn-1Ω(x',y')dx'=0, y'∈Sm-1,∫ sm-1Ω(x',y')dy'=0, x'∈Sn-1,且b,h∈L∞(R1+),则积域上极大奇异积分算子T*(f)=supε1>0,ε2>0∫∫|u|>ε1|v|>ε2b(|u|)h (|v|)Ω(u',v')/|v|n|v|mf(x-u,y-v)dudv为Lp(Rn×Rm)有界,其中1<p<∞.从而改进了以往的结果. 相似文献
44.
Mohamed El-Gebeily Donal O'Regan 《Journal of Mathematical Analysis and Applications》2007,334(1):140-156
Existence theory is developed for the equation ?(u)=F(u), where ? is a formally self-adjoint singular second-order differential expression and F is nonlinear. The problem is treated in a Hilbert space and we do not require the operators induced by ? to have completely continuous resolvents. Nonlinear boundary conditions are allowed. Also, F is assumed to be weakly continuous and monotone at one point. Boundary behavior of functions associated with the domains of definitions of the operators associated with ? in the singular case is investigated. A special class of self-adjoint operators associated with ? is obtained. 相似文献
45.
Yu Zanping Zhou Zheyan School of Math.and Computer Science Fujian Normal University Fuzhou ) Shen Jianhe 《Annals of Differential Equations》2007,23(3):365-372
The paper aims to obtain existence and uniqueness of the solution as well as asymptotic estimate of the solution for singularly perturbed nonlinear third- order Robin boundary value problem with a turning point.In order to achieve this aim,existence and uniqueness of the solution for third-order nonlinear Robin boundary value problem is derived first based on the upper and lower solutions method under relatively weaker conditions.In this manner,the goal of this paper is gained by applying the existence and uniqueness results mentioned above. 相似文献
46.
47.
48.
P. W. Hemker 《Advances in Computational Mathematics》1995,4(1):83-110
We introduce a multigrid algorithm for the solution of a second order elliptic equation in three dimensions. For the approximation of the solution we use a partially ordered hierarchy of finite-volume discretisations. We show that there is a relation with semicoarsening and approximation by more-dimensional Haar wavelets. By taking a proper subset of all possible meshes in the hierarchy, a sparse grid finite-volume discretisation can be constructed.The multigrid algorithm consists of a simple damped point-Jacobi relaxation as the smoothing procedure, while the coarse grid correction is made by interpolation from several coarser grid levels.The combination of sparse grids and multigrid with semi-coarsening leads to a relatively small number of degrees of freedom,N, to obtain an accurate approximation, together with anO(N) method for the solution. The algorithm is symmetric with respect to the three coordinate directions and it is fit for combination with adaptive techniques.To analyse the convergence of the multigrid algorithm we develop the necessary Fourier analysis tools. All techniques, designed for 3D-problems, can also be applied for the 2D case, and — for simplicity — we apply the tools to study the convergence behaviour for the anisotropic Poisson equation for this 2D case. 相似文献
49.
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
50.
既不离散也不连续的随机变量 总被引:2,自引:1,他引:1
讨论了既不离散也不连续的随机变量 ,并纠正了有关文献中关于连续型随机变量定义中的错误 . 相似文献