全文获取类型
收费全文 | 78351篇 |
免费 | 8978篇 |
国内免费 | 7756篇 |
专业分类
化学 | 37021篇 |
晶体学 | 1402篇 |
力学 | 13661篇 |
综合类 | 848篇 |
数学 | 19296篇 |
物理学 | 22857篇 |
出版年
2024年 | 175篇 |
2023年 | 889篇 |
2022年 | 1925篇 |
2021年 | 1975篇 |
2020年 | 2453篇 |
2019年 | 2174篇 |
2018年 | 2091篇 |
2017年 | 2707篇 |
2016年 | 3042篇 |
2015年 | 2582篇 |
2014年 | 3747篇 |
2013年 | 5442篇 |
2012年 | 4529篇 |
2011年 | 5169篇 |
2010年 | 4301篇 |
2009年 | 4975篇 |
2008年 | 4742篇 |
2007年 | 4823篇 |
2006年 | 4469篇 |
2005年 | 4105篇 |
2004年 | 3758篇 |
2003年 | 3201篇 |
2002年 | 3333篇 |
2001年 | 2414篇 |
2000年 | 2116篇 |
1999年 | 1848篇 |
1998年 | 1661篇 |
1997年 | 1425篇 |
1996年 | 1299篇 |
1995年 | 1125篇 |
1994年 | 1068篇 |
1993年 | 815篇 |
1992年 | 817篇 |
1991年 | 583篇 |
1990年 | 470篇 |
1989年 | 381篇 |
1988年 | 346篇 |
1987年 | 275篇 |
1986年 | 198篇 |
1985年 | 213篇 |
1984年 | 203篇 |
1983年 | 92篇 |
1982年 | 161篇 |
1981年 | 155篇 |
1980年 | 147篇 |
1979年 | 167篇 |
1978年 | 136篇 |
1977年 | 112篇 |
1976年 | 89篇 |
1973年 | 33篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
1.
2.
3.
Inner derivations and norm equality 总被引:3,自引:0,他引:3
Mohamed Barraa Mohamed Boumazgour 《Proceedings of the American Mathematical Society》2002,130(2):471-476
We characterize when the norm of the sum of two bounded operators on a Hilbert space is equal to the sum of their norms.
4.
We discuss an error estimation procedure for the global error of collocation schemes applied to solve singular boundary value problems with a singularity of the first kind. This a posteriori estimate of the global error was proposed by Stetter in 1978 and is based on the idea of Defect Correction, originally due to Zadunaisky. Here, we present a new, carefully designed modification of this error estimate which not only results in less computational work but also appears to perform satisfactorily for singular problems. We give a full analytical justification for the asymptotical correctness of the error estimate when it is applied to a general nonlinear regular problem. For the singular case, we are presently only able to provide computational evidence for the full convergence order, the related analysis is still work in progress. This global estimate is the basis for a grid selection routine in which the grid is modified with the aim to equidistribute the global error. This procedure yields meshes suitable for an efficient numerical solution. Most importantly, we observe that the grid is refined in a way reflecting only the behavior of the solution and remains unaffected by the unsmooth direction field close to the singular point. 相似文献
5.
Rafael López 《Annals of Global Analysis and Geometry》1997,15(3):201-210
In this paper we study constant mean curvature compact surfaces with two Jordan curves in parallel planes as boundary and we investigate the point at which the surface inherits the symmetries of its boundary. 相似文献
6.
Phase Relations and Sodium Ion Conductivity within the Quasi-binary System Na2SiF6/Na2AIF6 . The phase diagram of the Na2SiF6/Na3AlF6 system has been determined by means of x-ray powder diffraction, thermal analysis and conductivity measurements in the sub-solidus region. Na3AlF6 accomodates up to 73 mol.-% Na2SiF6 maintaining the crystal structure type. The sodium ion conductivity increases by about five orders of magnitude upon doping Na3AlF6 with Na2SiF6. 相似文献
7.
8.
Dean A. Carlson 《Journal of Mathematical Analysis and Applications》2002,276(2):561-588
The method of equivalent variational methods, originally due to Carathéodory for free problems in the calculus of variations is extended to investigate feedback Nash equilibria for a class of n-person differential games. Both the finite-horizon and infinite-horizon cases are considered. Examples are given to illustrate the presented results. 相似文献
9.
Volker Elling. 《Mathematics of Computation》2006,75(256):1721-1733
A particular case of initial data for the two-dimensional Euler equations is studied numerically. The results show that the Godunov method does not always converge to the physical solution, at least not on feasible grids. Moreover, they suggest that entropy solutions (in the weak entropy inequality sense) are not well posed.
10.
P.A. Ramachandran 《Numerical Methods for Partial Differential Equations》2006,22(4):831-846
Time‐dependent differential equations can be solved using the concept of method of lines (MOL) together with the boundary element (BE) representation for the spatial linear part of the equation. The BE method alleviates the need for spatial discretization and casts the problem in an integral format. Hence errors associated with the numerical approximation of the spatial derivatives are totally eliminated. An element level local cubic approximation is used for the variable at each time step to facilitate the time marching and the nonlinear terms are represented in a semi‐implicit manner by a local linearization at each time step. The accuracy of the method has been illustrated on a number of test problems of engineering significance. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2006 相似文献