全文获取类型
收费全文 | 31729篇 |
免费 | 5241篇 |
国内免费 | 4972篇 |
专业分类
化学 | 24258篇 |
晶体学 | 422篇 |
力学 | 1598篇 |
综合类 | 328篇 |
数学 | 4026篇 |
物理学 | 11310篇 |
出版年
2024年 | 83篇 |
2023年 | 598篇 |
2022年 | 840篇 |
2021年 | 1067篇 |
2020年 | 1306篇 |
2019年 | 1265篇 |
2018年 | 1080篇 |
2017年 | 1075篇 |
2016年 | 1533篇 |
2015年 | 1539篇 |
2014年 | 1858篇 |
2013年 | 2512篇 |
2012年 | 2818篇 |
2011年 | 3010篇 |
2010年 | 2190篇 |
2009年 | 1995篇 |
2008年 | 2279篇 |
2007年 | 2034篇 |
2006年 | 1805篇 |
2005年 | 1562篇 |
2004年 | 1273篇 |
2003年 | 1068篇 |
2002年 | 1129篇 |
2001年 | 927篇 |
2000年 | 766篇 |
1999年 | 687篇 |
1998年 | 527篇 |
1997年 | 437篇 |
1996年 | 455篇 |
1995年 | 404篇 |
1994年 | 337篇 |
1993年 | 240篇 |
1992年 | 222篇 |
1991年 | 216篇 |
1990年 | 185篇 |
1989年 | 118篇 |
1988年 | 90篇 |
1987年 | 74篇 |
1986年 | 96篇 |
1985年 | 70篇 |
1984年 | 52篇 |
1983年 | 41篇 |
1982年 | 22篇 |
1981年 | 17篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1973年 | 3篇 |
1957年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
The behavior of a two-level entangled atom in an optical field with circular polarization is studied in this paper. The interaction of an optical field and one of the entangled atoms is analyzed in detail. A general solution of the SchrAo¨Gdinger equation about the motion of the entangled atom is obtained. The properties of the action are dependent on the initial state of the atom. By detecting the entangled atom out of the field, we can obtain the state of the other atom moving in the field. It is shown that the state of the atom out of the field will influence the energies of the split-levels of the atom in the field. 相似文献
102.
103.
Ying Zhang Gang Hu Shigang Chen H.A. Cerdeira 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(3):381-384
A method of controlling global stochasticity in Hamiltonian systems by applying nonlinear perturbation is proposed. With the
well-known standard map we demonstrate that this control method can convert global stochasticity into regular motion in a
wide chaotic region for arbitrary initial condition, in which the control signal remains very weak after a few kicks. The
system in which chaos has been controlled approximates to the original Hamiltonian system, and this approach appears robust
against small external noise. The mechanism underlying this high control efficiency is intuitively explained.
Received 15 January 2002 Published online 6 June 2002 相似文献
104.
利用Ditzian-Totik光滑模,研究了推广的Kantorovich算子在Ba空间中的逼近,得到逼近的正定理与等价定理.所得结果改进、推广和统一了一些作者的结果. 相似文献
105.
106.
Jiaqiang Wang Hua Fang Ying Li Junjie Li Zhiying Yan 《Journal of molecular catalysis. A, Chemical》2006,250(1-2):75-79
Cobalt-doped mesoporous titania with a crystalline framework synthesized by surfactant templating method presented highly selective (99%) and reasonable conversion rate (49%) of catalytic oxidation of para-chlorotoluene to para-chlorobenzaldehyde in acetic acid using aqueous hydrogen peroxide as oxidant for the first time. Recycling of the catalyst indicates that the catalyst can be used a number of times without losing its activity to a greater extent. By contrast, cobalt-doped mesoporous titania without a crystalline structure and cobalt doped the commercial titania, Degussa P25 prepared by impregnation method with the similar concentration of cobalt were found inactive. The effects of catalyst concentration, reaction time, reaction temperature, and solvents on the performance of the catalyst were also investigated. 相似文献
107.
On the third largest Laplacian eigenvalue of a graph 总被引:1,自引:0,他引:1
Ji-Ming Guo 《Linear and Multilinear Algebra》2007,55(1):93-102
In this article, a sharp lower bound for the third largest Laplacian eigenvalue of a graph is given in terms of the third largest degree of the graph. 相似文献
108.
109.
On Polynomial Functions over Finite Commutative Rings 总被引:1,自引:0,他引:1
Jian Jun JIANG Guo Hua PENG Qi SUN Qi Fan ZHANG 《数学学报(英文版)》2006,22(4):1047-1050
Let R be an arbitrary finite commutative local ring. In this paper, we obtain a necessary and sufficient condition for a function over R to be a polynomial function. Before this paper, necessary and sufficient conditions for a function to be a polynomial function over some special finite commutative local rings were obtained. 相似文献
110.
This study presents a compact optical configuration that can generate a multiplex dot-matrix hologram with complex interlaced images for anti-counterfeiting applications on valuable paper. Varying the orientation of the interference plane can enable the multiplex hologram to be recorded without changing the interference angle of two laser beams. With its simple asymmetric optical setup, a multiplex hologram with many interlaced images can be efficiently fabricated, increasing the cost of imitation. Experimental details of the asymmetric optical setup are also described. 相似文献