全文获取类型
收费全文 | 2792篇 |
免费 | 527篇 |
国内免费 | 401篇 |
专业分类
化学 | 2073篇 |
晶体学 | 17篇 |
力学 | 160篇 |
综合类 | 22篇 |
数学 | 308篇 |
物理学 | 1140篇 |
出版年
2024年 | 10篇 |
2023年 | 60篇 |
2022年 | 113篇 |
2021年 | 69篇 |
2020年 | 119篇 |
2019年 | 116篇 |
2018年 | 121篇 |
2017年 | 101篇 |
2016年 | 151篇 |
2015年 | 132篇 |
2014年 | 175篇 |
2013年 | 195篇 |
2012年 | 224篇 |
2011年 | 234篇 |
2010年 | 181篇 |
2009年 | 173篇 |
2008年 | 206篇 |
2007年 | 149篇 |
2006年 | 158篇 |
2005年 | 163篇 |
2004年 | 111篇 |
2003年 | 101篇 |
2002年 | 109篇 |
2001年 | 76篇 |
2000年 | 58篇 |
1999年 | 63篇 |
1998年 | 49篇 |
1997年 | 28篇 |
1996年 | 35篇 |
1995年 | 41篇 |
1994年 | 38篇 |
1993年 | 35篇 |
1992年 | 25篇 |
1991年 | 20篇 |
1990年 | 19篇 |
1989年 | 13篇 |
1988年 | 8篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 5篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1936年 | 1篇 |
排序方式: 共有3720条查询结果,搜索用时 15 毫秒
981.
This paper has observed linewidth narrowing of dark states in rubidium cell by using the Hanle configuration. The reduction of the coherent resonance width under the transition of ^87Rb Fg = 1 → Fe = 0 is observed and the qualitative explanation about its mechanism is presented. Multiple subnatural width dips are obtained with a linearly polarized laser beam for the transitions of ^87Rb Fg = 1→Fe = 0, 1, 2. The feature of negative and positive slope, namely dispersionlike feature, is observed in the transmitted light. 相似文献
982.
This paper presents a scheme for probabilistic remote preparation of a three-particle entangled Greenberger-Horne-Zeilinger (GHZ) state via three-particle orthonormal basis projective measurement, and then directly generalize the scheme to multi-particle case. It is shown that by using N pairs of bipartite non-maximally entangled states as the quantum channel and N-particle orthonormal basis projective measurement, the multi-particle remote preparation can be successfully realized with a certain probability. 相似文献
983.
The growth of Mn5Ge3 ultrathin films with different thicknesses, prepared by solid phase epitaxy, is studied. The results of scanning tunnelling microscopy and low energy electron diffraction studies show that the film can be formed and it is terminated with a (√3 × √3) R30° surface reconstruction when the thickness of Mn exceeds 3 monolayers. The magnetic properties show that the Curie temperature is about 300 K and the T^2-dependent behaviour is observed to remain up to 220 K. 相似文献
984.
Different chaos synchronization based encryption schemes are reviewed and compared from the practical point of view. As an efficient cryptanalysis tool for chaos encryption, a proposal based on the error function attack is presented systematically and used to evaluate system security. We define a quantitative measure (quality factor) of the effective applicability of a chaos encryption scheme, which takes into account the security, the encryption speed, and the robustness against channel noise. A comparison is made of several encryption schemes and it is found that a scheme based on one-way coupled chaotic map lattices performs outstandingly well, as judged from quality factor. 相似文献
985.
Jun?Zhang Jie?ZhangEmail author Yang?Qiu Zhengming?Sheng Yutong?Li Zhan?Jin Hao?Teng 《中国科学G辑(英文版)》2003,46(6):625-631
The dependence of emission direction of fast electrons on the laser intensity has been investigated. The experimental results
show that, at nonrelativistic laser intensities, the emission of fast electrons is mainly in the polarization plane. With
the increase of the laser intensity, fast electrons emit towards the laser propagation direction from laser polarization direction.
At relativistic laser intensities, fast electrons move away from the laser polarization plane, closely to the reflection direction
of the incident laser beam. 相似文献
986.
Highly oriented GaN nanowire arrays have been achieved by the catalytic reaction of gallium with ammonium. The resulting materials
were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM), energy dispersive X-ray
spectroscopy (EDS), transmission electron microscopy (TEM) and selected-area electron diffraction (SAED). SEM images show
that the resulting materials are nanowire arrays with a uniform length of about 10 μm. XRD, EDS, TEM and SAED indicate that
the nanowire arrays are single-crystal hexagonal GaN with a wurtzite structure. They have diameters of 10 to 20 nm.
Received: 2 October 2002 / Accepted: 7 October 2002 / Published online: 17 December 2002
RID="*"
ID="*"Corresponding author. E-mail: wwwangjc@sina.com 相似文献
987.
Kadish KM Shao J Ou Z Frémond L Zhan R Burdet F Barbe JM Gros CP Guilard R 《Inorganic chemistry》2005,44(19):6744-6754
Three face-to-face linked porphyrin-corrole dyads were investigated as to their electrochemistry, spectroelectrochemistry, and chloride-binding properties in dichloromethane or benzonitrile. The same three compounds were also investigated as to their ability to catalyze the electroreduction of dioxygen in aqueous 1 M HClO4 or HCl when adsorbed on a graphite electrode. The characterized compounds are represented as (PCY)H2Co, where P = a porphyrin dianion; C = a corrole trianion; and Y = a biphenylenyl, 9,9-dimethylxanthenyl, or anthracenyl spacer, which links the two macrocycles in a face-to-face arrangement. An axial binding of one or two Cl- ligands to the cobalt center of the corrole is observed for singly and doubly oxidized (PCY)H2Co, with the exact stoichiometry of the reaction depending upon the spacer size and the concentration of Cl- added to solution. No Cl- binding occurs for the neutral or reduced forms of the dyad, which contrasts with what is seen for the monocorrole, (Me4Ph5Cor)Co, where a single Cl- ligand is added to the Co(III) corrole in PhCN. The Co(III) form of the corrole in (PCY)H2Co also appears to be the catalytically active species in the electroreduction of dioxygen, which occurs at potentials associated with the Co(IV)/Co(III) reaction, that is, 0.35 V in 1 M HClO4 as compared to 0.31-0.42 V for the same three dyads in PhCN and 0.1 M TBAP. The potential for the catalytic electroreduction of O2 in HCl shifts negatively by 60 to 70 mV as compared to E(1/2) values in 1 M HClO4, consistent with the binding of Cl- to the Co(IV) form of the corrole and its rapid dissociation after electroreduction to Co(III) at the electrode surface. 相似文献
988.
Uniqueness and stability of solution for Cauchy problem of degenerate quasilinear parabolic equations 总被引:2,自引:0,他引:2
ZHAO Junning & ZHAN Huashui Department of Mathematics Xiamen University Xiamen China School of Science Jimei University Xiamen China 《中国科学A辑(英文版)》2005,48(5):583-593
The uniqueness and existence of BV-solutions for Cauchy problem of the form are proved. 相似文献
989.
Fabrication of metal-semiconductor nanowire heterojunctions 总被引:1,自引:0,他引:1
990.