全文获取类型
收费全文 | 392073篇 |
免费 | 2776篇 |
国内免费 | 882篇 |
专业分类
化学 | 189166篇 |
晶体学 | 5961篇 |
力学 | 19493篇 |
综合类 | 10篇 |
数学 | 56555篇 |
物理学 | 124546篇 |
出版年
2020年 | 2375篇 |
2019年 | 2589篇 |
2018年 | 11269篇 |
2017年 | 12074篇 |
2016年 | 8995篇 |
2015年 | 4026篇 |
2014年 | 5301篇 |
2013年 | 13409篇 |
2012年 | 13789篇 |
2011年 | 23316篇 |
2010年 | 15150篇 |
2009年 | 15205篇 |
2008年 | 20908篇 |
2007年 | 24042篇 |
2006年 | 10850篇 |
2005年 | 15764篇 |
2004年 | 11877篇 |
2003年 | 10950篇 |
2002年 | 9023篇 |
2001年 | 8978篇 |
2000年 | 6980篇 |
1999年 | 5197篇 |
1998年 | 4472篇 |
1997年 | 4306篇 |
1996年 | 4134篇 |
1995年 | 3869篇 |
1994年 | 3811篇 |
1993年 | 3588篇 |
1992年 | 4083篇 |
1991年 | 4131篇 |
1990年 | 3926篇 |
1989年 | 3859篇 |
1988年 | 3827篇 |
1987年 | 3714篇 |
1986年 | 3555篇 |
1985年 | 4631篇 |
1984年 | 4835篇 |
1983年 | 4138篇 |
1982年 | 4396篇 |
1981年 | 4093篇 |
1980年 | 4028篇 |
1979年 | 4324篇 |
1978年 | 4523篇 |
1977年 | 4235篇 |
1976年 | 4366篇 |
1975年 | 4213篇 |
1974年 | 4203篇 |
1973年 | 4351篇 |
1972年 | 2869篇 |
1971年 | 2454篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
S. Meenakshi B.K. Godwal I. Orgzall S. Tkachev 《Journal of Physics and Chemistry of Solids》2006,67(8):1660-1667
We report the results of an X-ray diffraction study of CdAl2Se4 and of Raman studies of HgAl2Se4 and ZnAl2Se4 at room temperature, and of CdAl2S4 and CdAl2Se4 at 80 K at high pressure. The ambient pressure phase of CdAl2Se4 is stable up to a pressure of 9.1 GPa above which a phase transition to a disordered rock salt phase is observed. A fit of the volume pressure data to a Birch-Murnaghan type equation of state yields a bulk modulus of 52.1 GPa. The relative volume change at the phase transition at ∼9 GPa is about 10%. The analysis of the Raman data of HgAl2Se4 and ZnAl2Se4 reveals a general trend observed for different defect chalcopyrite materials. The line widths of the Raman peaks change at intermediate pressures between 4 and 6 GPa as an indication of the pressure induced two stage order-disorder transition observed in these materials. In addition, we include results of a low temperature Raman study of CdAl2S4 and CdAl2Se4, which shows a very weak temperature dependence of the Raman-active phonon modes. 相似文献
72.
V. Edon M.C. Hugon B. Agius L. Miotti C. Radtke F. Tatsch J.J. Ganem I. Trimaille I.J.R. Baumvol 《Applied Physics A: Materials Science & Processing》2006,83(2):289-293
The influence of processing parameters on the electrical characteristics of RuO2/LaAlO3/Si metal-oxide-semiconductor structures was investigated. In particular, the sputtering regime during deposition of LaAlO3 on Si and the atmosphere used in the post-deposition annealing step were addressed by determining capacitance-voltage and
gate current-voltage characteristics. These results were correlated with compositional information obtained by Rutherford
backscattering spectrometry and nuclear reaction analysis. A post-deposition annealing step in oxygen at 600 °C resulted in
better electrical characteristics of the final structure as compared to the same treatment performed in nitrogen. This result
is explained by oxygen ability to heal oxygen vacancies in the LaAlO3 film, especially at the dielectric/semiconductor interface region. A thermalized sputtering regime during deposition of LaAlO3 on Si leads to capacitors with electrical characteristics superior to those deposited in ballistic regime.
PACS 77.84.Dy; 81.15.Cd; 81.40.Gh; 73.40.Qv; 82.80.Yc 相似文献
73.
A Dirac picture perturbation theory is developed for the time evolution operator in classical dynamics in the spirit of the Schwinger–Feynman–Dyson perturbation expansion and detailed rules are derived for computations. Complexification formalisms are given for the time evolution operator suitable for phase space analyses, and then extended to a two-dimensional setting for a study of the geometrical Berry phase as an example. Finally a direct integration of Hamilton's equations is shown to lead naturally to a path integral expression, as a resolution of the identity, as applied to arbitrary functions of generalized coordinates and momenta. 相似文献
74.
F. Iachello S. Oss 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(3):307-314
We present a brief review of algebraic techniques developed and applied in molecular spectroscopy in the last five years.
We also outline perspectives for new applications of the Lie algebraic method in the first decade of the new century.
Received 21 November 2001 相似文献
75.
R. F. Bikbaev 《Journal of Mathematical Sciences》1991,57(3):3078-3083
Diffraction by a semitransparent screen is considered in the framework of the nonlinear Schrödinger equation. The case of a defocusing medium is investigated. The method used represents a synthesis of the method of Riemann's matrix problem and the technique of Whitham's deformations of spectral curves.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova, Vol. 179, pp. 23–31, 1989. 相似文献
76.
Under idealized conditions, electroconvection in a nematic liquid crystal sets in at a well-defined threshold of the driving ac voltage. Fluctuating convection rolls of a small amplitude below that threshold have been observed recently. The measurement of the amplitude of these fluctuations is described in detail in this paper. It is based on averaging the light intensity signals using the structure function and a quantitative analysis of the light deflection. 相似文献
77.
Robert M. O'Keefe 《The Journal of the Operational Research Society》1989,40(5):415-422
Cognitive style refers to differences that can be perceived in individuals due to differing cognitive structures. There has been a large amount of research on how cognitive style affects managerial decision-making, particularly in the context of management information systems, but little or no attempt to relate these findings to operational research. This paper reviews the findings of cognitive-style research from the perspective of operational research, and draws a number of useful inferences concerning the matching of OR aids to managers, the presentation of information and recommendations, the use and acceptance of OR, and the structure of OR groups. Further, it is argued that cognitive-style findings help to give a justification to the move towards ‘soft’ approaches to analysis. 相似文献
78.
79.