全文获取类型
收费全文 | 9032篇 |
免费 | 370篇 |
国内免费 | 61篇 |
专业分类
化学 | 6088篇 |
晶体学 | 51篇 |
力学 | 231篇 |
数学 | 1798篇 |
物理学 | 1295篇 |
出版年
2023年 | 72篇 |
2022年 | 142篇 |
2021年 | 242篇 |
2020年 | 169篇 |
2019年 | 215篇 |
2018年 | 166篇 |
2017年 | 147篇 |
2016年 | 322篇 |
2015年 | 284篇 |
2014年 | 318篇 |
2013年 | 552篇 |
2012年 | 641篇 |
2011年 | 707篇 |
2010年 | 439篇 |
2009年 | 462篇 |
2008年 | 583篇 |
2007年 | 599篇 |
2006年 | 537篇 |
2005年 | 484篇 |
2004年 | 398篇 |
2003年 | 281篇 |
2002年 | 284篇 |
2001年 | 113篇 |
2000年 | 104篇 |
1999年 | 87篇 |
1998年 | 68篇 |
1997年 | 69篇 |
1996年 | 102篇 |
1995年 | 55篇 |
1994年 | 61篇 |
1993年 | 53篇 |
1992年 | 70篇 |
1991年 | 51篇 |
1990年 | 42篇 |
1989年 | 40篇 |
1988年 | 35篇 |
1987年 | 33篇 |
1986年 | 38篇 |
1985年 | 54篇 |
1984年 | 49篇 |
1983年 | 32篇 |
1982年 | 39篇 |
1981年 | 31篇 |
1980年 | 28篇 |
1979年 | 26篇 |
1978年 | 17篇 |
1977年 | 12篇 |
1975年 | 10篇 |
1974年 | 14篇 |
1971年 | 12篇 |
排序方式: 共有9463条查询结果,搜索用时 15 毫秒
51.
A classical Fermi accelerator model (FAM) is known to show chaotic behavior. The FAM is defined by a free particle bouncing elastically from two rigid walls, one fixed and the other oscillating periodically in time. The central aim of this paper is to connect the quantum and the classical solutions to the FAM in the semiclassical limit. This goal is accomplished using a finite inverted parametric oscillator (FIPO), confined to a box withfixed walls, as an alternative representation of the FAM. In the FIPO representation, an explicit correspondence between classical and quantum limits is accomplished using a Husimi representation of the quasienergy eigenfunctions. 相似文献
52.
Luiza Amália Moraes Luis Romero Grados 《Journal of Mathematical Analysis and Applications》2003,281(2):575-586
Let Au(BG) be the Banach algebra of all complex valued functions defined on the closed unit ball BG of a complex Banach space G which are uniformly continuous on BG and holomorphic in the interior of BG, endowed with the sup norm. A characterization of the boundaries for Au(BG) is given in case G belongs to a class of Banach spaces that includes the pre-dual of a Lorentz sequence space studied by Gowers in Israel J. Math. 69 (1990) 129-151. The non-existence of the Shilov boundary for Au(BG) is also proved. 相似文献
53.
Jean Dolbeault Maria J Esteban Michael Loss Luis Vega 《Journal of Functional Analysis》2004,216(1):1-21
We prove some sharp Hardy-type inequalities related to the Dirac operator by elementary, direct methods. Some of these inequalities have been obtained previously using spectral information about the Dirac-Coulomb operator. Our results are stated under optimal conditions on the asymptotics of the potentials near zero and near infinity. 相似文献
54.
A program to compute many functions dependent on the electron density ρ(r) from the results of ab initio molecular calculations is presented. The program allows the generation of different one-, two-, and three-dimensional grids for further graphical representation or numerical analysis. Other options like extracting separate atom contributions to the function computed or locating maximum and minimum values are also implemented. A number of illustrative applications regarding different ρ(r)-dependent functions are presented and the performance and portability of the program is discussed. 相似文献
55.
The classes ofL
1-matrices,L
2-matrices,L
3-matrices andW-matrices are introduced to study solvability of a linear complementarity problem via solving a linear program. Three sufficient
conditions are presented to guarantee that a linear complementarity problem is solvable via a linear program. The new sufficient
conditions are weaker than the ones introduced by Mangasarian. This fact is also illustrated by an example.
Partially supported by NSFC.
This author is also with College of Business Administration of Human University as a Lotus chair professor. 相似文献
56.
In this work we consider computing and continuing connecting orbits in parameter dependent dynamical systems. We give details
of algorithms for computing connections between equilibria and periodic orbits, and between periodic orbits. The theoretical
foundation for these techniques is given by the seminal work of Beyn in 1994, “On well-posed problems for connecting orbits
in dynamical systems”, where a numerical technique is also proposed. Our algorithms consist of splitting the computation of
the connection from that of the periodic orbit(s). To set up appropriate boundary conditions, we follow the algorithmic approach
used by Demmel, Dieci, and Friedman, for the case of connecting orbits between equilibria, and we construct and exploit the
smooth block Schur decomposition of the monodromy matrices associated to the periodic orbits. Numerical examples illustrate
the performance of the algorithms.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
57.
Inés CarrancoJosé Luis D?&#x;az Oscar JiménezRodolfo Lavilla 《Tetrahedron letters》2003,44(46):8449-8452
The Lewis acid-catalyzed interaction of dihydropyridines with ethyl glyoxalate and primary aliphatic amines yields, depending on the reaction conditions, bicyclic aminals or rearranged tetrahydropyridines in one-pot multicomponent reactions. 相似文献
58.
Jos Luis Rodrigo 《纯数学与应用数学通讯》2005,58(6):821-866
We consider the problem of the evolution of sharp fronts for the surface quasi‐geostrophic (QG) equation. This problem is the analogue to the vortex patch problem for the two‐dimensional Euler equation. The special interest of the quasi‐geostrophic equation lies in its strong similarities with the three‐dimensional Euler equation, while being a two‐dimen‐sional model. In particular, an analogue of the problem considered here, the evolution of sharp fronts for QG, is the evolution of a vortex line for the three‐dimensional Euler equation. The rigorous derivation of an equation for the evolution of a vortex line is still an open problem. The influence of the singularity appearing in the velocity when using the Biot‐Savart law still needs to be understood. We present two derivations for the evolution of a periodic sharp front. The first one, heuristic, shows the presence of a logarithmic singularity in the velocity, while the second, making use of weak solutions, obtains a rigorous equation for the evolution explaining the influence of that term in the evolution of the curve. Finally, using a Nash‐Moser argument as the main tool, we obtain local existence and uniqueness of a solution for the derived equation in the C∞ case. © 2004 Wiley Periodicals, Inc. 相似文献
59.
Jorge Rivera-Noriega 《Proceedings of the American Mathematical Society》2004,132(5):1321-1331
An extension of an inequality of J. B. Garnett (1979), with improvements by B. E. J. Dahlberg (1980), on an approximation property of harmonic functions is proved. The weighted inequality proved here was suggested by the work of J. Pipher (1993) and it implies an extension of a result of S. Y. A. Chang, J. Wilson and T. Wolff (1985) and C. Sweezy (1991) on exponential square integrability of the boundary values of solutions to second-order linear differential equations in divergence form. This implies a solution of a problem left open by R. Bañuelos and C. N. Moore (1989) on sharp estimates for the area integral of harmonic functions in Lipschitz domains.
60.
This study demonstrates the separation of active ingredients in acne formulations (salicylic acid, cloramphenicol and resorcinol in presence of azulene) by capillary zone electrophoresis. Factors affecting their separations were the buffer pH and concentration, applied voltage, sample preparation, and presence of additives. Optimun results were obtained with a 50 mM sodium tetraborate-50 mM sodium phosphate, pH 9.0. The carrier electrolyte gave baseline separation with good resolution, short migration times (<6 min), great reproducibility and accuracy. Calibration plots were linear over at least three orders of magnitude of analyte concentrations, the lower limits of detection being within the range 0.39-1.25 μg ml−1. The procedure was fast and reliable and commercial pharmaceuticals could be analysed without prior sample clean-up procedure. 相似文献