全文获取类型
收费全文 | 6482篇 |
免费 | 1498篇 |
国内免费 | 468篇 |
专业分类
化学 | 1063篇 |
晶体学 | 60篇 |
力学 | 943篇 |
综合类 | 156篇 |
数学 | 1762篇 |
物理学 | 4464篇 |
出版年
2024年 | 22篇 |
2023年 | 63篇 |
2022年 | 132篇 |
2021年 | 164篇 |
2020年 | 182篇 |
2019年 | 164篇 |
2018年 | 173篇 |
2017年 | 245篇 |
2016年 | 277篇 |
2015年 | 248篇 |
2014年 | 488篇 |
2013年 | 513篇 |
2012年 | 388篇 |
2011年 | 426篇 |
2010年 | 329篇 |
2009年 | 373篇 |
2008年 | 424篇 |
2007年 | 436篇 |
2006年 | 423篇 |
2005年 | 369篇 |
2004年 | 313篇 |
2003年 | 280篇 |
2002年 | 269篇 |
2001年 | 277篇 |
2000年 | 237篇 |
1999年 | 202篇 |
1998年 | 167篇 |
1997年 | 155篇 |
1996年 | 135篇 |
1995年 | 106篇 |
1994年 | 76篇 |
1993年 | 52篇 |
1992年 | 53篇 |
1991年 | 51篇 |
1990年 | 36篇 |
1989年 | 27篇 |
1988年 | 24篇 |
1987年 | 30篇 |
1986年 | 18篇 |
1985年 | 16篇 |
1984年 | 15篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 14篇 |
1980年 | 10篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1971年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有8448条查询结果,搜索用时 15 毫秒
61.
62.
Elie Leopold 《Numerical Algorithms》2007,44(4):347-366
In this paper, we give some new explicit relations between two families of polynomials defined by recurrence relations of
all order. These relations allow us to analyze, even in the Sobolev case, how some properties of a family of orthogonal polynomials
are affected when the coefficients of the recurrence relation and the order are perturbed. In a paper we have already given
a method which allows us to study the polynomials defined by a three-term recurrence relation. Also here some generalizations
are given. 相似文献
63.
In this article, we show how to construct pairs of orthogonal pandiagonal Latin squares and panmagic squares from certain types of modular n‐queens solutions. We prove that when these modular n‐queens solutions are symmetric, the panmagic squares thus constructed will be associative, where for an n × n associative magic square A = (aij), for all i and j it holds that aij + an?i?1,n?j?1 = c for a fixed c. We further show how to construct orthogonal Latin squares whose modular difference diagonals are Latin from any modular n‐queens solution. As well, we analyze constructing orthogonal pandiagonal Latin squares from particular classes of non‐linear modular n‐queens solutions. These pandiagonal Latin squares are not row cyclic, giving a partial solution to a problem of Hedayat. © 2007 Wiley Periodicals, Inc. J Combin Designs 15: 221–234, 2007 相似文献
64.
D. S. Barsegyan 《Mathematical Notes》2007,82(3-4):451-460
Applying the method proposed by Kashin for proving inequalities of Lieb-Thirring type for orthonormal systems, we prove a similar inequality in the multidimensional case. 相似文献
65.
王登银 《数学物理学报(B辑英文版)》2007,27(2):317-328
All parabolic subgroups and Borel subgroups of PΩ(2m 1, F) over a linear-able field F of characteristic 0 are shown to be complete groups, provided m > 3. 相似文献
66.
67.
68.
69.
Flat-top interleavers with chromatic dispersion compensator based on phase dispersive free space Mach-Zehnder interferometer 总被引:2,自引:0,他引:2
In this paper, novel interleavers using circular cavities (CC) in a Mach-Zehnder interferometer (MZI) has been presented and demonstrated for the first time, in which CCs act as phase dispersive mirrors which exhibit a periodic dependence on the frequency of light. Three implementation schemes have been proposed and investigated. Theoretical analysis shows the spectral characteristics of each scheme in a 50-GHz channel spacing application. Furthermore, the chromatic dispersion (CD) of each output comb can be flattened within passband by appending an additional CC. The result shows that the proposed designs with novel interferometer technique can simultaneously provide flat top passbands, high isolation stopband and low CD value as well. 相似文献
70.
R. S. Kaler 《Fiber and Integrated Optics》2006,25(1):41-57
In this article, the comparison of large signal theory and small signal theory has been done with dispersive propagation of optical signal with IMDD (Intensity Modulation Direct Detection) systems for semiconductor lasers with higher-order dispersion terms. The expressions for an exact large signal theory and small signal theory including higher-order dispersion terms for propagation of an optical wave with sinusoidal amplitude and frequency modulation in a dispersive fiber have been derived. It is observed that small signal theory is more sensitive compared to large signal theory in terms of intensity modulation/direct detection systems. Also, it is reported that for large signal analysis the higher-order effects of dispersion can be ignored, whereas for small signal theory, the higher-order effects can be ignored for lower modulation frequencies only. The variation in the transfer function for various values of modulation indices are greater for small signal analysis than for large signal analysis. Also, as the intensity modulation index is increased, there is a decrease in the value of transfer function. The large signal model approximates the small signal model for lower values of the intensity modulation index. 相似文献