全文获取类型
收费全文 | 543433篇 |
免费 | 4214篇 |
国内免费 | 1448篇 |
专业分类
化学 | 272978篇 |
晶体学 | 8175篇 |
力学 | 26347篇 |
综合类 | 11篇 |
数学 | 75261篇 |
物理学 | 166323篇 |
出版年
2020年 | 3562篇 |
2019年 | 4013篇 |
2018年 | 12137篇 |
2017年 | 12769篇 |
2016年 | 11002篇 |
2015年 | 5552篇 |
2014年 | 7648篇 |
2013年 | 20207篇 |
2012年 | 18271篇 |
2011年 | 28128篇 |
2010年 | 18280篇 |
2009年 | 17994篇 |
2008年 | 25102篇 |
2007年 | 28086篇 |
2006年 | 15830篇 |
2005年 | 19694篇 |
2004年 | 15780篇 |
2003年 | 14492篇 |
2002年 | 12781篇 |
2001年 | 13086篇 |
2000年 | 10157篇 |
1999年 | 7764篇 |
1998年 | 6714篇 |
1997年 | 6671篇 |
1996年 | 6416篇 |
1995年 | 5912篇 |
1994年 | 5904篇 |
1993年 | 5689篇 |
1992年 | 6327篇 |
1991年 | 6327篇 |
1990年 | 6103篇 |
1989年 | 6010篇 |
1988年 | 6148篇 |
1987年 | 5947篇 |
1986年 | 5677篇 |
1985年 | 7588篇 |
1984年 | 8057篇 |
1983年 | 6695篇 |
1982年 | 7087篇 |
1981年 | 6946篇 |
1980年 | 6826篇 |
1979年 | 6842篇 |
1978年 | 7272篇 |
1977年 | 7067篇 |
1976年 | 7300篇 |
1975年 | 6663篇 |
1974年 | 6804篇 |
1973年 | 7270篇 |
1972年 | 4813篇 |
1971年 | 3900篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The reasons for the existence of various scenarios for structural transformations in disordered condensed media, such as liquids and amorphous substances, where both smeared transformations and sharp first-order transitions may occur, were analyzed. The ratio between the spatial scale of structural correlations and the size of the smallest possible region occupied by a new phase in the matrix of initial modification is the key parameter determining the scenario for equilibrium phase transformations in liquids. In amorphous substances, the experimentally observed transformations occur far from equilibrium, and the possible size of the region occupied by the new phase corresponds to the minimal nucleus size. For some amorphous solids, quantitative analysis of the transformation width was carried out and the main classes of covalent substances, in which the smeared or sharp transitions occur, were revealed. Specific features of the interparticle interactions determining various transformation scenarios are discussed. 相似文献
992.
Jacques Rouzaud MatthewD. Jones Robert Raja BrianF.G. Johnson John MeurigThomas MelindaJ. Duer 《Helvetica chimica acta》2003,86(5):1753-1759
A set of new, air‐stable, RhI‐based heterogeneous asymmetric hydrogenation catalysts have been synthesised, characterised, and tested. Individual members of this new family all exhibit good enantioselectivity. 相似文献
993.
Arthur G. Maki John C. Grecu Brenda Winnewisser Manfred Winnewisser 《Journal of Molecular Spectroscopy》2003,222(2):198-212
High-resolution spectra of 15N12C12C15N and 14N13C13C14N have been measured and analyzed from 200 to 3600 cm−1. All the vibrational levels below 900 cm−1 have been observed and characterized. The Fermi resonance between ν2 and 2ν4 has been studied and the resonance constant has been determined for several cases. Several Σ− states have been directly observed for the first time for each isotopomer, the (0001111)0f, (0011111)0f, and (0002222)0f states. The pattern of the energy levels for clusters of l-type resonance coupled levels, such as 0001131,3, has been determined for cyanogen for the first time. Among other things this involved the determination of the vibrational l-type resonance constant, r45. Many of the power series constants, αi and xij, and higher order constants have been determined. 相似文献
994.
995.
V. G. Bozhkov 《Radiophysics and Quantum Electronics》2003,46(8-9):631-656
The state of the art in the development of semiconductor detectors, mixers, and frequency multipliers based on Schottky-barrier diodes (SBDs) and heterojunction structures for uncooled terahertz receivers is reviewed. The present status of this field features a transition from quasi-optical designs based on dot-matrix, whisker-contacted SBDs to the designs with hybrid-integrated and monolithic constructions on the planar SBD base, which are positioned in a waveguide mount. The high-level performance of these planar devices is achieved by partially or completely removing or changing semiconductor substrates and/or using membrane constructions incorporated in the waveguide. 相似文献
996.
A pseudopotential depending on an effective core radius is proposed to study the binding energy, equation of state, ion-ion
interaction, phonon dispersion curves (q-space and r-space analysis), mode Grüneisen parameters and dynamical elastic constants
of some fcc f-shell metals La, Yb, Ce and Th. The contribution of the s-like electrons is calculated in the second-order perturbation
theory for the potential while d and f-like electron is taken into account by introducing repulsive short-range Born-Mayer
term. The parameter of the potential is evaluated by zero pressure condition. An excellent agreement between theoretical investigations
and experimental findings is achieved which confirms the present formalism 相似文献
997.
998.
999.
Makarov V. L. Khlobystov V. V. Kashpur E. F. Mikhal'chuk B. R. 《Ukrainian Mathematical Journal》2003,55(6):942-955
We construct an integral Newton-type interpolation polynomial with a continual set of nodes. This interpolant is unique and preserves an operator polynomial of the corresponding degree. 相似文献
1000.
M. M. Glazov 《Physics of the Solid State》2003,45(6):1162-1165
A precession mechanism of spin relaxation of conduction electrons in a square quantum well is analyzed. The dependence of the spin relaxation time on the width of a quantum well and the height of its barriers is calculated under the assumption that the electron-electron collisions dominate over other processes of carrier scattering. 相似文献