全文获取类型
收费全文 | 5780篇 |
免费 | 547篇 |
国内免费 | 420篇 |
专业分类
化学 | 1034篇 |
晶体学 | 9篇 |
力学 | 528篇 |
综合类 | 91篇 |
数学 | 2331篇 |
物理学 | 2754篇 |
出版年
2024年 | 7篇 |
2023年 | 36篇 |
2022年 | 73篇 |
2021年 | 68篇 |
2020年 | 135篇 |
2019年 | 143篇 |
2018年 | 148篇 |
2017年 | 202篇 |
2016年 | 217篇 |
2015年 | 166篇 |
2014年 | 343篇 |
2013年 | 387篇 |
2012年 | 271篇 |
2011年 | 357篇 |
2010年 | 268篇 |
2009年 | 426篇 |
2008年 | 480篇 |
2007年 | 442篇 |
2006年 | 393篇 |
2005年 | 319篇 |
2004年 | 302篇 |
2003年 | 225篇 |
2002年 | 209篇 |
2001年 | 154篇 |
2000年 | 163篇 |
1999年 | 141篇 |
1998年 | 119篇 |
1997年 | 123篇 |
1996年 | 80篇 |
1995年 | 64篇 |
1994年 | 52篇 |
1993年 | 29篇 |
1992年 | 26篇 |
1991年 | 23篇 |
1990年 | 18篇 |
1989年 | 24篇 |
1988年 | 37篇 |
1987年 | 20篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 8篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1980年 | 2篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1957年 | 2篇 |
1936年 | 1篇 |
排序方式: 共有6747条查询结果,搜索用时 140 毫秒
41.
本文主要讨论了当非负位势 V(x)属于某逆Holder类时,由一致椭圆算子L=-div(A(x))+V(x)所定义的 Riesz变换在 Lp空间的有界性。 相似文献
42.
43.
Jin Cheng Ching-Lung Lin Gen Nakamura 《Proceedings of the American Mathematical Society》2005,133(8):2359-2367
In this paper we prove the following kind of unique continuation property. That is, the zero on each geodesic of the solution in a real analytic hypersurface for second order anisotropic hyperbolic systems with real analytic coefficients can be continued along this curve.
44.
Durand William A.Pham Ngoc Dinh 《Journal of Mathematical Analysis and Applications》2003,282(1):95-106
An electromagnetic diffraction problem in a wedge shaped region is reduced to a system of coupled functional difference equations by means of Sommerfeld integrals and Malyuzhinets theorem. By introducing an integral operator it is shown that the solutions of this system of functional equations can be defined in terms of integral representations whose kernels are solutions of a singular integral equation of Cauchy-Carleman type for which an explicit solution is given. 相似文献
45.
Jonatan Lenells 《Journal of Mathematical Analysis and Applications》2007,325(2):1468-1478
We use the inverse scattering transform to show that a solution of the Camassa-Holm equation is identically zero whenever it vanishes on two horizontal half-lines in the x-t space. In particular, a solution that has compact support at two different times vanishes everywhere, proving that the Camassa-Holm equation has infinite propagation speed. 相似文献
46.
47.
By introducing an imaginary space transform curvature ρs, a complex space called Riemannian space is constructed, in which the light propagating in free space has the trajectory
of straight line while propagating. Moreover, this curvature couples with that of the wave front of the paraxial beam ρw, and therefore a complex curvature ρc is constructed, which can be employed to investigate the behavior of the light transmission and to generalize the ABCD law.
Project supported by the National Hi-Tech Inertial Confinement Fusion Committee, the Guangdong Natural Science Foundation
the Postdoctoral Foundation of Guangdong and National Postdoctoral Foundation of China. 相似文献
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.
THENBELCANDNWELCCLASSESOFLIFEDISTRIBUTIONS¥CAOJINHUA;WANGYUEDONG(InstituteofAppliedMathematics,ChineseAcademyofScience,Beijin... 相似文献
50.
A new method for rotation and brightness invariant pattern recognition was proposed by applying multiple circular harmonic expansions to the joint transform correlator. The amplitudes of the multiple orders of circular harmonic expansions made from a detecting image were synthetically modified to respond to the same auto-correlation peaks. These modified circular harmonic expansions were arranged in the input plane as reference patterns together with an arbitrary target pattern, and the correlation signals between them were calculated in the subtracted joint transform correlator. The fraction of the correlation-peak intensities between the target and the references were extracted as a new discrimination parameter. This new parameter performs pattern recognition under rotation and brightness invariance with good discriminability. Its high discriminability has been proved in computer simulations using the face image patterns of many individuals. 相似文献