全文获取类型
收费全文 | 8658篇 |
免费 | 1647篇 |
国内免费 | 919篇 |
专业分类
化学 | 3107篇 |
晶体学 | 71篇 |
力学 | 846篇 |
综合类 | 111篇 |
数学 | 452篇 |
物理学 | 6637篇 |
出版年
2024年 | 29篇 |
2023年 | 126篇 |
2022年 | 189篇 |
2021年 | 215篇 |
2020年 | 209篇 |
2019年 | 209篇 |
2018年 | 225篇 |
2017年 | 261篇 |
2016年 | 330篇 |
2015年 | 315篇 |
2014年 | 511篇 |
2013年 | 557篇 |
2012年 | 465篇 |
2011年 | 627篇 |
2010年 | 459篇 |
2009年 | 574篇 |
2008年 | 579篇 |
2007年 | 653篇 |
2006年 | 638篇 |
2005年 | 483篇 |
2004年 | 415篇 |
2003年 | 350篇 |
2002年 | 317篇 |
2001年 | 327篇 |
2000年 | 292篇 |
1999年 | 260篇 |
1998年 | 263篇 |
1997年 | 200篇 |
1996年 | 160篇 |
1995年 | 146篇 |
1994年 | 135篇 |
1993年 | 94篇 |
1992年 | 83篇 |
1991年 | 84篇 |
1990年 | 56篇 |
1989年 | 42篇 |
1988年 | 43篇 |
1987年 | 51篇 |
1986年 | 38篇 |
1985年 | 37篇 |
1984年 | 25篇 |
1983年 | 12篇 |
1982年 | 19篇 |
1981年 | 26篇 |
1980年 | 21篇 |
1979年 | 10篇 |
1978年 | 13篇 |
1977年 | 13篇 |
1976年 | 8篇 |
1974年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
D. Onoufriou 《Surface science》2004,573(2):237-252
The evolution of N,N′-dimethylperylene-3,4,9,10-dicarboxyimide (Me-PTCDI) thin films formed by vapour deposition on InSb(1 1 1)A substrates has been studied by X-ray photoelectron spectroscopy (XPS), high-resolution electron energy loss spectroscopy (HREELS) and low energy electron diffraction (LEED). XPS studies of the Me-PTCDI covered surface indicate that no significant interaction occurs at sub-monolayer coverage when compared to multilayer Me-PTCDI films. HREELS studies suggest only a weak interaction as evidenced by very small changes in the frequencies of several molecular vibrational modes. LEED patterns show the Me-PTCDI overlayer adopts a structure commensurate with the underlying InSb(1 1 1)A substrate surface and that can be rationalised by van der Waals intermolecular energy calculations for the Me-PTCDI unit cell. The results are consistent with a weak interaction at the Me-PTCDI/InSb interface, the formation of the commensurate structure being sufficient to overcome the small energetic penalty associated with deviation from the calculated intermolecular interaction energy minimum. 相似文献
962.
With the emphasis on the effects of the density-dependent bag constant and the rotation of strange star the limiting mass of strange star is calculated. The obtained results show that the limiting mass and the corresponding radius of strange star increase as the rotation frequency increases, and tend to be lowered when the density-dependent bag constant is considered. 相似文献
963.
964.
表面增强拉曼散射概述 总被引:5,自引:0,他引:5
表面增强拉曼散射概述武建劳,郇宜贤,傅克德,张鹏翔(陕西师范大学物理系西安710062)Thestatusofsurface-enhancedRamanscatteringWuJialao;HuanYixianFuKede;ZhangPengxian... 相似文献
965.
本文针对《1972年国际海上避碰规则》号灯、号型提供的协助避碰的信息和海员作出避碰决策所需的避碰信息的关系,分析了规则号灯、号型的现状及存在问题,提出了修改号灯、号型有关内容的若干具体建议。 相似文献
966.
A population global optimization algorithm to solve the image alignment problem in electron crystallography 总被引:2,自引:0,他引:2
P. M. Ortigosa J. L. Redondo I. García J. J. Fernández 《Journal of Global Optimization》2007,37(4):527-539
Knowledge of the structure of biological specimens is critical to understanding their function. Electron crystallography is
an electron microscopy (EM) approach that derives the 3D structure of specimens at high-resolution, even at atomic detail.
Prior to the tomographic reconstruction, the images taken from the microscope have to be properly aligned. Traditional alignment
methods in electron crystallography are based on a phase residual function to be minimized by inefficient exhaustive search
procedures. This work addresses this minimization problem from an evolutionary perspective. Universal Evolutionary Global
Optimizer (UEGO), an evolutionary multimodal optimization algorithm, has been applied and evaluated for the task of image
alignment in this field. UEGO has turned out to be a promising technique alternative to the standard methodology. The alignments
found out by UEGO show high levels of accuracy, while reducing the number of function evaluations by a significant factor
with respect to the standard method. 相似文献
967.
中频脉冲磁控溅射制备氮化铝薄膜 总被引:10,自引:0,他引:10
使用中频脉冲磁控溅射技术分别在Si(111)、玻璃以及高速钢基底上沉积A1N薄膜,利用X射线衍射、X射线光电子谱、扫描电镜、紫外荧光、FTIR、精密阻抗分析仪等研究了薄膜的结构、光学及电学性质,结果表明,生成的(002)取向多晶A1N薄膜在可见光区域平均透过率超过75%,在紫外区域也具有较高的透过经,在低频交流区域具有良好的绝缘性。 相似文献
968.
S.A. Mikhailov K. Ziegler 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(1):117-120
A floating Wigner crystal differs from the standard one by a spatial averaging over positions of the Wigner-crystal lattice.
It has the same internal structure as the fixed crystal, but contrary to it, takes into account rotational and/or translational
symmetry of the underlying jellium background. We study properties of a floating Wigner molecule in few-electron spin-polarized
quantum dots, and show that the floating solid has the lower energy than the standard Wigner crystal with fixed lattice points.
We also argue that internal rotational symmetry of individual dots can be broken in arrays of quantum dots, due to degenerate
ground states and inter-dot Coulomb coupling.
Received 12 September 2001 / Received in final form 24 April 2002 Published online 9 July 2002 相似文献
969.
Xavier Fradera Jordi Poater Sílvia Simon Miquel Duran Miquel Solà 《Theoretical chemistry accounts》2002,108(4):214-224
This article presents an overview of recent advances in the study of electron pairing through the use of localization and
delocalization indices obtained from double integration over atomic basins of the exchange–correlation density in the framework
of the atoms-in-molecules theory. These localization and delocalization indices describe the intra- and interatomic distribution
of the electron pairs in a molecule. The main results of the application of these second-order indices to the analysis of
molecular structure and chemical reactivity are briefly reviewed. It is shown that localization and delocalization indices
represent a powerful tool to describe the electron-pair structure of molecules, which, in turn, provides deeper insight into
relevant chemical phenomena such as electron correlation effects and the formation of localized α, β electron pairs.
Received: 8 April 2002 / Accepted: 26 June 2002 / Published online: 6 September 2002
Acknowledgements. Financial help was furnished by the Spanish DGES projects no. PB98-0457-C02-01 and BQU2002-04112-C02-02. J.P. thanks the
Departament d'Universitats, Recerca i Societat de la Informació de la Generalitat de Catalunya for benefiting from a doctoral
fellowship, no. 2000FI-00582. M.S. is indebted to the Departament d'Universitats, Recerca i Societat de la Informació of the
Generalitat de Catalunya for financial support through the Distinguished University Research Promotion, 2001. We also thank
the Centre de Supercomputació de Catalunya for providing us with computing facilities.
Correspondence to: M. Solà e-mail: miquel.sola@udg.es 相似文献
970.
LD泵浦Nd:YAG微片激光器 总被引:3,自引:0,他引:3
LD泵浦Nd:YAG微片激光器结构简单紧凑,与半导体激光器相比,前者具有激光线宽窄、光束质量好、相干长度长等优点,因此在一些测量领域有着较好的应用前景。目前对LD泵浦Nd:YAG微片激光器的实验工作主要是获得单频、单模连续输出和线性频率调制特性研究。本文综述了近几年来LD泵浦Nd:YAG微片激光器的研究方向、成果及应用,主要介绍了各国对LD泵浦Nd:YAG微片激光器的调频特性的研究状况 相似文献