全文获取类型
收费全文 | 15261篇 |
免费 | 3819篇 |
国内免费 | 1410篇 |
专业分类
化学 | 9802篇 |
晶体学 | 205篇 |
力学 | 147篇 |
综合类 | 76篇 |
数学 | 105篇 |
物理学 | 10155篇 |
出版年
2024年 | 23篇 |
2023年 | 129篇 |
2022年 | 412篇 |
2021年 | 576篇 |
2020年 | 706篇 |
2019年 | 576篇 |
2018年 | 522篇 |
2017年 | 590篇 |
2016年 | 807篇 |
2015年 | 807篇 |
2014年 | 1146篇 |
2013年 | 1474篇 |
2012年 | 1066篇 |
2011年 | 1105篇 |
2010年 | 884篇 |
2009年 | 983篇 |
2008年 | 977篇 |
2007年 | 1097篇 |
2006年 | 959篇 |
2005年 | 739篇 |
2004年 | 626篇 |
2003年 | 601篇 |
2002年 | 497篇 |
2001年 | 448篇 |
2000年 | 420篇 |
1999年 | 347篇 |
1998年 | 310篇 |
1997年 | 290篇 |
1996年 | 226篇 |
1995年 | 189篇 |
1994年 | 170篇 |
1993年 | 138篇 |
1992年 | 105篇 |
1991年 | 78篇 |
1990年 | 87篇 |
1989年 | 56篇 |
1988年 | 56篇 |
1987年 | 51篇 |
1986年 | 43篇 |
1985年 | 35篇 |
1984年 | 42篇 |
1983年 | 7篇 |
1982年 | 23篇 |
1981年 | 19篇 |
1980年 | 16篇 |
1979年 | 4篇 |
1978年 | 10篇 |
1975年 | 5篇 |
1973年 | 5篇 |
1970年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
31.
电子自旋是原子物理学和量子力学的重要概念,电子自旋假说的产生在物理学史上具有一定的特殊性,该文系统论述了电子自旋假说提出了与被物理学界接受的历史,并从荷兰莱顿理论物理研究的学术环境、乌仑贝克和哥德斯密“理论型”与实验型”的互补、艾仑费斯行的教育艺术等方面分析了其历史经验。 相似文献
32.
Chemical bonding in isolated molecules and crystals of zwitterionic pentacoordinate silicon chelates
The electronic structures of a number of zwitterionic pentacoordinate silicon chelates were investigated using the results of X-ray diffraction studies and quantum-chemical calculatoins by the MPW1PW91/6-311G(d) method. The topological analysis of the electron density distribution function and the study in the framework of the natural bond orbital partitioning scheme showed that the character of chemical bonding in the axial fragments of the molecules under consideration changes from dative to three-center, four-electron as the silicon atom assumes a trigonal-bipyramidal coordination. 相似文献
33.
强流脉冲电子束在材料中的能量沉积剖面、能量沉积系数和束流传输系数受其入射角的影响很大,理论计算了0.5~2.0MeV的电子束以不同的入射角在Al材料中的能量沉积剖面和能量沉积系数,并且还计算了0.4~1.4MeV电子束以不同入射角穿透不同厚度C靶的束流传输系数。计算结果表明,随着入射角的增大,靶材表面层单位质量中沉积的能量增大,电子在靶材料中穿透深度减小,能量沉积系数减小,相应的束流传输系数也减小;能量为0.5~2.0MeV的电子束当入射角在60°~70°时在材料表面层单位质量中沉积的能量较大。 相似文献
34.
35.
36.
37.
N. U. Aldiyarov K. K. Kadyrzhanov E. M. Yakushev V. S. Zhdanov 《Hyperfine Interactions》2005,164(1-4):67-72
The conditions for achievement of high resolving power of depth selective conversion electron Mössbauer spectroscopy method at a combined installation ‘electron spectrometer–nuclear gamma-resonance spectrometer’ have been obtained. There has been made a considerable step in development of the method at its realization at a magnetic sector electron spectrometer with double focusing, equipped with electron source (a sample under investigation) of large-area and position-sensitive detector. The paper presents a prospective symmetrical version of a magnetic sector electron spectrometer that allows realizing more completely possibilities of the method. It is noted that the proposed method is particularly valuable for investigations of nanosystems, nanostrutures that contain Mössbauer nuclei. 相似文献
38.
本文提出从高分辨电子显微像中,利用光学、全息和部分相干等方法,提取传递函数,制作相位和振幅滤波器,实现解卷,提高高分辨电子显微像的分辨率. 相似文献
39.
B. Saha S. Bhattacharyya T. K. Mukherjee P. K. Mukherjee 《International journal of quantum chemistry》2003,92(5):413-418
In the framework of nonrelativistic variational formalism a new type of basis set is proposed, to estimate separately the effect of radial and angular correlations on the ground‐state energy for helium isoelectronic sequence H? to Ar16+. Effect of radial correlation is incorporated by using multiexponential functions arising from product basis sets suitably formed out of Slater‐type one‐particle orbitals. The angular correlation can be switched on by incorporating an expansion in terms of basis involving interparticle coordinates. With a set of six‐term Slater‐type one‐particle basis and five‐term interparticle expansion, the ground‐state energy of helium is estimated as ?2.9037236 (a.u.) compared with the multiterm variational estimates ?2.9037244 (a.u.) due to Pekeris and Thakkar and Smith and Drake. Matrix elements of different operators in the ground state have been calculated and found to be in good agreement with available accurate results. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003 相似文献
40.
K. Dayananda R. Dhamodharan K. Vijayakumaran T. Rajamannar 《Journal of polymer science. Part A, Polymer chemistry》2004,42(21):5413-5423
A monolayer of covalently anchored, novel, binaphthyl ketone is used as a surface‐confined photochemical radical generator (PRG) for anchoring a variety of polymers to silicon surfaces. The precursor PRG is synthesized by the application of a facile and novel method for the oxidation of sterically hindered benzylic hydrocarbons to carbonyl compounds. Oxidation was carried out with a stoichiometric amount of potassium peroxydisulfate, in the presence of a catalytic amount of copper sulfate in an acetonitrile/water mixture. The PRG synthesized is characterized by 1H NMR, UV, and Fourier transform infrared (FTIR). The covalently attached monolayers are characterized by X‐ray photoelectron spectroscopy, ellipsometry, and water contact angle measurements. The method developed is applicable to the preparation of a monolayer of a variety of polymers on a wide range of substrates carrying surface hydroxyl groups. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5413–5423, 2004 相似文献