全文获取类型
收费全文 | 46086篇 |
免费 | 5590篇 |
国内免费 | 9871篇 |
专业分类
化学 | 35841篇 |
晶体学 | 212篇 |
力学 | 3138篇 |
综合类 | 3篇 |
数学 | 13026篇 |
物理学 | 9327篇 |
出版年
2024年 | 179篇 |
2023年 | 1691篇 |
2022年 | 1195篇 |
2021年 | 1426篇 |
2020年 | 2315篇 |
2019年 | 1666篇 |
2018年 | 1762篇 |
2017年 | 1775篇 |
2016年 | 2755篇 |
2015年 | 2484篇 |
2014年 | 2144篇 |
2013年 | 5277篇 |
2012年 | 4026篇 |
2011年 | 3815篇 |
2010年 | 2920篇 |
2009年 | 2464篇 |
2008年 | 2767篇 |
2007年 | 3294篇 |
2006年 | 3118篇 |
2005年 | 2126篇 |
2004年 | 1723篇 |
2003年 | 1692篇 |
2002年 | 1359篇 |
2001年 | 1221篇 |
2000年 | 1067篇 |
1999年 | 1527篇 |
1998年 | 630篇 |
1997年 | 593篇 |
1996年 | 450篇 |
1995年 | 440篇 |
1994年 | 213篇 |
1993年 | 232篇 |
1992年 | 172篇 |
1991年 | 137篇 |
1990年 | 124篇 |
1989年 | 64篇 |
1988年 | 125篇 |
1987年 | 157篇 |
1986年 | 258篇 |
1985年 | 57篇 |
1984年 | 11篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 13篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 12篇 |
1936年 | 42篇 |
排序方式: 共有10000条查询结果,搜索用时 6 毫秒
81.
X.P. Hu X. Wang Z. Yan H.X. Li J.L. He S.N. Zhu 《Applied physics. B, Lasers and optics》2007,86(2):265-268
High power red light was generated from a periodically-poled stoichiometric LiTaO3 (PPSLT) by single-pass frequency doubling of a diode-side-pumped, Q-switched Nd:YAG laser at 1319 nm. An average power of
2.4 W of the 660 nm red light was obtained at the fundamental power of ∼5.4 W with the conversion efficiency up to 44.4% and
with low fluctuation down to 2%. The high efficiency and stability at the red output indicate that it is a practical method
to construct a reliable compact red laser.
PACS 42.70.Mp; 42.79.Nv; 42.55.Xi 相似文献
82.
Wei Gang SU Huai Jie ZHONG 《数学学报(英文版)》2006,22(2):515-522
This paper introduces the concept of the generalized Riesz operators and the concept of the generalized West decomposition of a general operator which generalizes the definition of the West decomposition of Riesz operators, and proves that the following three statements are equivalent on a general Banach space:
(a) Every generalized Riesz operator has the generalized West decomposition;
(b) Every operator makes strong Stampfli theorem true; Every operator has Apostol's compact correction. 相似文献
83.
84.
Chuncheng Hao Zuolin Cui Yansheng Yin Zhikun Zhang 《Journal of nanoparticle research》2002,4(1-2):107-110
Nanostructured Fe3Al intermetallic compounds were produced by using hydrogen arc plasma method. The transmission electron microscopy experiments showed that the average particle size of the as-synthesized was about 40-nm. The change in hardness of Fe3Al nanostructured intermetallic compounds with annealing temperatures was observed and evaluated. 相似文献
85.
Jinyan Fan 《Computational Optimization and Applications》2006,34(2):215-227
In this paper, we present the new trust region method for nonlinear equations with the trust region converging to zero. The
new method preserves the global convergence of the traditional trust region methods in which the trust region radius will
be larger than a positive constant. We study the convergence rate of the new method under the local error bound condition
which is weaker than the nonsingularity. An example given by Y.X. Yuan shows that the convergence rate can not be quadratic.
Finally, some numerical results are given.
This work is supported by Chinese NSFC grants 10401023 and 10371076, Research Grants for Young Teachers of Shanghai Jiao Tong
University, and E-Institute of Computational Sciences of Shanghai Universities.
An erratum to this article is available at . 相似文献
86.
Qingfeng Zhang Shanjia Xu 《International Journal of Infrared and Millimeter Waves》2006,27(11):1539-1552
A novel uniplanar 2-D composite right/left-handed transmission line (CRLH-TL) structure is proposed based on a general transmission
line theory and the way to increase the relative operating bandwidth in the left-handed (LH) region and lower the LH operating
frequency is illustrated. In addition, a new method to extract parameters and calculate the Bloch impedance of the structure
is presented. Numerical results of the dispersion as well as the extracted parameters are given, which are calculated based
on full-wave simulation. The present 2-D uniplanar CRLH-TL structure is applicable to 2-D left-handed materials in lower and
wider LH frequency range.
Supported by the National Natural Science Foundation of China (No. 60371010) (No. 60471037) (No. 63531020) 相似文献
87.
Zhao Yang YIN 《数学学报(英文版)》2006,22(3):819-826
Sufficient conditions for the existence of positive solutions to a class of quasilinear elliptic equations in two-dimensional exterior domains are given. 相似文献
88.
利用离子速度影象技术研究了正一溴丁烷(n-C4H9Br)在231~267 nm波段的光解,得出了如下结论:正一溴丁烷(n-C4H9Br)在231~267 nm波段的吸收源于基态到三个最低激发态的跃迁,这三个激发态标识为1A″、2A′和3A′;发生在这三个排斥态的势能面(PES)上的光解最终导致C4H9 Br(2P3/2)或C4H9 Br*(2P1/2)的产生;2A′和3A′态之间存在避免交叉(Avoided crossing)会影响最终的光解产物;从基态1A′到激发态1A″的跃迁矩垂直于对称面,也就垂直于C-Br键;从基态1A′到激发态3A′的跃迁矩平行于对称面,同时平行于C-Br键;从基态1A′到激发态2A′的跃迁矩在对称面内,且与C-Br键成53.1°夹角.我们也讨论了正一溴丁烷(n-C4H9Br)在234 nm和267 nm附近光解时的避免交叉几率(Avoided crossingprobability),以及它对单通道相对产额(Relative fraction of the individual pathways)的影响. 相似文献
89.
Hongwei Yu 《General Relativity and Gravitation》1991,23(3):297-304
By solving the coupled SU(5) Einstein-Yang-Mills-Higgs equations, we obtain the exact Reissner-Nordstrom type gravitational field of a family of spherically symmetric SU(5) dyons with magnetic charge 1/2e. 相似文献
90.
一类多线性积分算子的端点有界性 总被引:3,自引:0,他引:3
本文对一类相关于非卷积型算子的多线性算子,证明了其在端点情形上的有界性,该算子包括Littlewood-Paley算子和Marcinkiewicz算子. 相似文献