全文获取类型
收费全文 | 15441篇 |
免费 | 1475篇 |
国内免费 | 1740篇 |
专业分类
化学 | 1244篇 |
晶体学 | 95篇 |
力学 | 1032篇 |
综合类 | 313篇 |
数学 | 13107篇 |
物理学 | 2865篇 |
出版年
2024年 | 22篇 |
2023年 | 149篇 |
2022年 | 181篇 |
2021年 | 240篇 |
2020年 | 361篇 |
2019年 | 462篇 |
2018年 | 432篇 |
2017年 | 471篇 |
2016年 | 540篇 |
2015年 | 384篇 |
2014年 | 753篇 |
2013年 | 1264篇 |
2012年 | 666篇 |
2011年 | 920篇 |
2010年 | 844篇 |
2009年 | 1066篇 |
2008年 | 1092篇 |
2007年 | 1093篇 |
2006年 | 925篇 |
2005年 | 849篇 |
2004年 | 720篇 |
2003年 | 720篇 |
2002年 | 710篇 |
2001年 | 541篇 |
2000年 | 560篇 |
1999年 | 511篇 |
1998年 | 431篇 |
1997年 | 403篇 |
1996年 | 263篇 |
1995年 | 156篇 |
1994年 | 135篇 |
1993年 | 96篇 |
1992年 | 74篇 |
1991年 | 73篇 |
1990年 | 52篇 |
1989年 | 52篇 |
1988年 | 48篇 |
1987年 | 32篇 |
1986年 | 18篇 |
1985年 | 48篇 |
1984年 | 53篇 |
1983年 | 31篇 |
1982年 | 44篇 |
1981年 | 32篇 |
1980年 | 34篇 |
1979年 | 27篇 |
1978年 | 24篇 |
1977年 | 11篇 |
1976年 | 11篇 |
1936年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
George A. Anastassiou 《Semigroup Forum》2009,78(1):54-67
Here we present Poincaré type general L
p
inequalities regarding semigroups, cosine and sine operator functions. 相似文献
992.
In this paper we obtain a necessary and sufficient condition for Toeplitz operators with generalized circulant symbols to be hyponormal. 相似文献
993.
An iterative resolution method for inverse Cauchy problems is presented. The successive iterations satisfy the equilibrium equations exactly. Numerical simulations prove the accuracy of the method and its ability to solve Cauchy problems when the domain boundary is not regular. To cite this article: A. Cimetière et al., C. R. Mecanique 333 (2005). 相似文献
994.
Parrondo’s paradox [J.M.R. Parrondo, G.P. Harmer, D. Abbott, New paradoxical games based on Brownian ratchets, Phys. Rev. Lett. 85 (2000), 5226–5229] (see also [O.E. Percus, J.K. Percus, Can two wrongs make a right? Coin-tossing games and Parrondo’s paradox, Math. Intelligencer 24 (3) (2002) 68–72]) states that two losing gambling games when combined one after the other (either deterministically or randomly) can result in a winning game: that is, a losing game followed by a losing game = a winning game. Inspired by this paradox, a recent study [J. Almeida, D. Peralta-Salas, M. Romera, Can two chaotic systems give rise to order? Physica D 200 (2005) 124–132] asked an analogous question in discrete time dynamical system: can two chaotic systems give rise to order, namely can they be combined into another dynamical system which does not behave chaotically? Numerical evidence is provided in [J. Almeida, D. Peralta-Salas, M. Romera, Can two chaotic systems give rise to order? Physica D 200 (2005) 124–132] that two chaotic quadratic maps, when composed with each other, create a new dynamical system which has a stable period orbit. The question of what happens in the case of random composition of maps is posed in [J. Almeida, D. Peralta-Salas, M. Romera, Can two chaotic systems give rise to order? Physica D 200 (2005) 124–132] but left unanswered. In this note we present an example of a dynamical system where, at each iteration, a map is chosen in a probabilistic manner from a collection of chaotic maps. The resulting random map is proved to have an infinite absolutely continuous invariant measure (acim) with spikes at two points. From this we show that the dynamics behaves in a nearly ordered manner. When the foregoing maps are applied one after the other, deterministically as in [O.E. Percus, J.K. Percus, Can two wrongs make a right? Coin-tossing games and Parrondo’s paradox, Math. Intelligencer 24 (3) (2002) 68–72], the resulting composed map has a periodic orbit which is stable. 相似文献
995.
R. S. Ismagilov 《Functional Analysis and Its Applications》2008,42(1):72-74
The author [5] introduced Racah operators for unitary representations of topological groups of type I. In the present paper, we indicate the explicit form of these operators for representations of the group of motions of three-dimensional Euclidean space. 相似文献
996.
一种基于梯度算子和拉普拉斯算子检测医学基因芯片荧光数字图像边缘的方法.数字图像经过图像增强等预处理以后,突出了我们感兴趣的数字图像特征,根据数字图像灰度变化的趋势,用灰度变化的一阶导数(梯度算子)检测图象中的边缘区域;用灰度变化的二阶导数确定图像边缘的中心位置.最后根据某些预定的准则把满足这些准则的象素组成一条边缘. 相似文献
997.
O. A. Veliev 《Mathematische Nachrichten》2008,281(9):1341-1350
In this article we obtain asymptotic formulas for eigenvalues and eigenfunctions of the self‐adjoint operator generated by a system of Sturm–Liouville equations with summable coefficients and quasiperiodic boundary conditions. Then using these asymptotic formulas, we find conditions on the potential for which the number of gaps in the spectrum of the Hill's operator with matrix potential is finite. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
998.
Jianghua Fan 《Journal of Mathematical Analysis and Applications》2008,337(2):1041-1047
In this paper, we study the existence of solutions and approximation of the solutions by using a Mann type iterative scheme for variational inequalities in noncompact subsets of Banach spaces. The results presented in this paper generalize the corresponding results of J. Li [J. Li, On the existence of solutions of variational inequalities in Banach spaces, J. Math. Anal. Appl. 295 (2004) 115-126]. 相似文献
999.
A method is described that solves the problem of determining the correct birefringence and orientation angle of samples having multiple orders of retardation. The approach simultaneously uses two wavelengths of light combined with modulation of the polarization vector using a high-speed rotating half waveplate. The simultaneous application of two wavelengths is possible with the use of an achromatic waveplate. The technique is demonstrated by performing start-up Couette flow experiments on a concentrated polystyrene solution that produced multiple orders in retardation. 相似文献
1000.
希尔伯特空间有限区域成像积分算子的谱 总被引:1,自引:0,他引:1
本文讨论了希尔伯特空间中有限区域成像积分算子的本征值和本征函数,研究了非对称核的情形,并用微扰和有限秩方法计算了衍射受限和离焦情况下的本征值和本征函数。 相似文献