全文获取类型
收费全文 | 2650篇 |
免费 | 62篇 |
国内免费 | 2篇 |
专业分类
化学 | 1543篇 |
晶体学 | 12篇 |
力学 | 40篇 |
数学 | 171篇 |
物理学 | 948篇 |
出版年
2023年 | 22篇 |
2021年 | 25篇 |
2020年 | 45篇 |
2019年 | 39篇 |
2016年 | 53篇 |
2015年 | 34篇 |
2014年 | 40篇 |
2013年 | 105篇 |
2012年 | 99篇 |
2011年 | 100篇 |
2010年 | 63篇 |
2009年 | 58篇 |
2008年 | 123篇 |
2007年 | 111篇 |
2006年 | 122篇 |
2005年 | 106篇 |
2004年 | 91篇 |
2003年 | 61篇 |
2002年 | 51篇 |
2001年 | 52篇 |
2000年 | 44篇 |
1999年 | 22篇 |
1998年 | 27篇 |
1997年 | 34篇 |
1996年 | 42篇 |
1995年 | 32篇 |
1994年 | 42篇 |
1993年 | 56篇 |
1992年 | 49篇 |
1991年 | 25篇 |
1990年 | 36篇 |
1989年 | 25篇 |
1988年 | 26篇 |
1987年 | 41篇 |
1986年 | 36篇 |
1985年 | 36篇 |
1984年 | 42篇 |
1983年 | 23篇 |
1981年 | 21篇 |
1980年 | 24篇 |
1978年 | 30篇 |
1977年 | 39篇 |
1976年 | 33篇 |
1975年 | 27篇 |
1974年 | 20篇 |
1973年 | 35篇 |
1970年 | 20篇 |
1957年 | 30篇 |
1955年 | 29篇 |
1954年 | 21篇 |
排序方式: 共有2714条查询结果,搜索用时 46 毫秒
1.
2.
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
3.
4.
Extending to r > 1 a formula of the authors, we compute the expected reflection distance of a product of t random reflections in the complex reflection group G(r, 1, n). The result relies on an explicit decomposition of the reflection distance function into irreducible G(r, 1, n)-characters and on the eigenvalues of certain adjacency matrices.Received December 8, 2003 相似文献
5.
6.
C. Baumgarten B. Braun G. Court G. Ciullo P. Ferretti G. Graw W. Haeberli M. Henoch R. Hertenberger N. Koch H. Kolster P. Lenisa A. Nass S.P. Pod'yachev D. Reggiani K. Rith M.C. Simani E. Steffens J. Stewart T. Wise 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):37-49
The use of storage cells has become a standard technique for internal gas targets in conjunction with high energy storage
rings. In case of spin-polarized hydrogen and deuterium gas targets the interaction of the injected atoms with the walls of
the storage cell can lead to depolarization and recombination. Thus the number of wall collisions of the atoms in the target
gas is important for modeling the processes of spin relaxation and recombination. It is shown in this article that the diffusion
process of rarefied gases in long tubes or storage cells can be described with the help of the one-dimensional diffusion equation.
Mathematical methods are presented that allow one to calculate collision age distributions (CAD) and their moments analytically.
These methods provide a better understanding of the different aspects of diffusion than Monte Carlo calculations. Additionally
it is shown that measurements of the atomic density or polarization of a gas sample taken from the center of the tube allow
one to determine the possible range of the corresponding density weighted average values along the tube. The calculations
are applied to the storage cell geometry of the HERMES internal polarized hydrogen and deuterium gas target.
Received 9 July 2001 and Received in final form 18 September 2001 相似文献
7.
D. Chiladze J. Carbonell S. Dymov V. Glagolev M. Hartmann V. Hejny A. Kacharava I. Keshelashvili A. Khoukaz H.R. Koch V. Komarov P. Kulessa A. Kulikov G. Macharashvili Y. Maeda T. Mersmann S. Merzliakov S. Mikirtytchiants A. Mussgiller M. Nioradze H. Ohm F. Rathmann R. Schleichert H.J. Stein H. Ströher Yu. Uzikov S. Yaschenko C. Wilkin 《Physics letters. [Part B]》2006
8.
9.
Matthias Heydenreich Andreas Koch E. Kleinpeter Thomas Zimmermann 《Fresenius' Journal of Analytical Chemistry》1997,357(5):517-521
Dynamic NMR investigations of a number of 2-amino-3-aroyl-4,6-diaryl-pyrylium salts were carried out. The barrier to rotation
of the partial C, N double bond was determined and proved to be in the range of 62 to 63 kJ/mol. Quantum chemical calculations
of bond orders and electron densities of the different atoms in the molecules show the distinct double bond character of the
exocyclic C, N bond. This is in agreement with the relatively high barrier to rotation. By quantum chemical ab initio 3-21G
calculations, the dynamic behaviour of this kind of compounds was simulated; two pairs (image and mirror image) of ground
state conformations, in coincidence with the experiment, were obtained.
Received: 10 May 1996 / Revised: 1 July 1996 / Accepted: 4 July 1996 相似文献
10.