全文获取类型
收费全文 | 55933篇 |
免费 | 2103篇 |
国内免费 | 1595篇 |
专业分类
化学 | 38484篇 |
晶体学 | 420篇 |
力学 | 1069篇 |
综合类 | 13篇 |
数学 | 8670篇 |
物理学 | 10975篇 |
出版年
2023年 | 361篇 |
2022年 | 291篇 |
2021年 | 996篇 |
2020年 | 902篇 |
2019年 | 954篇 |
2018年 | 1038篇 |
2017年 | 1013篇 |
2016年 | 1931篇 |
2015年 | 1582篇 |
2014年 | 1720篇 |
2013年 | 3600篇 |
2012年 | 3814篇 |
2011年 | 4222篇 |
2010年 | 2570篇 |
2009年 | 2601篇 |
2008年 | 3411篇 |
2007年 | 3309篇 |
2006年 | 2944篇 |
2005年 | 2783篇 |
2004年 | 2734篇 |
2003年 | 2088篇 |
2002年 | 1833篇 |
2001年 | 1221篇 |
2000年 | 1047篇 |
1999年 | 838篇 |
1998年 | 677篇 |
1997年 | 585篇 |
1996年 | 695篇 |
1995年 | 513篇 |
1994年 | 491篇 |
1993年 | 512篇 |
1992年 | 467篇 |
1991年 | 349篇 |
1990年 | 343篇 |
1989年 | 267篇 |
1988年 | 269篇 |
1987年 | 272篇 |
1986年 | 262篇 |
1985年 | 357篇 |
1984年 | 341篇 |
1983年 | 257篇 |
1982年 | 255篇 |
1981年 | 234篇 |
1980年 | 202篇 |
1979年 | 196篇 |
1978年 | 159篇 |
1977年 | 161篇 |
1976年 | 145篇 |
1975年 | 130篇 |
1973年 | 140篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Jerónimo Rodríguez 《Comptes Rendus Mathematique》2004,339(6):445-450
In the present Note we introduce an extension of the conservative space–time mesh refinement method presented by Fouquet et al. We also propose a post-treatment of the solution that reduces the spurious phenomena due to the non-conformity between the time meshes. A reinterpretation of the equations in terms of new unknowns leads to a new scheme with second order consistent coupling equations. Numerical experiments in 2D and a plane wave analysis for the 1D model show that the method is second order accurate for an arbitrary refinement. To cite this article: J. Rodríguez, C. R. Acad. Sci. Paris, Ser. I 339 (2004). 相似文献
82.
The rational and sustainable exploitation of nature resources is one of the priority objectives of our society. In this article a method is proposed to evaluate and exploit the energetic resources contained in different forest formations. This method is based on the use of a combustion bomb calorimeter to determine the calorific values of the different samples studied. These results were complemented with chemical analysis of the samples and with environmental and geomorphological studies of the zones were samples were taken. The results obtained during the last 3 years for the residual biomass originated from the forest formations existing in Galicia ensure the reliability and usefulness of the method that can be extended to any forest formation all over the world. 相似文献
83.
84.
S. B. Ellis S. J. Kiehl W. S. Hughes K. Schwabe W. C. Gardiner H. L. Sanders H. Yoshimura Hanna Jablezynska-Jedrzewska J. Domański W. A. Dorfman P. Nylén Barbara Stone F. Hovorka W. C. Dearing E. Biilmann W. Kordatzki P. Wulff G. Florence A. Drilhon P. Szigeti O. Tomiček F. Poupě O. Redlich W. Stricks 《Analytical and bioanalytical chemistry》1937,111(2-4):94-104
85.
86.
The aim of this paper is to study I-fuzzy topologies (fuzzy topologies in
ostak's sense) derived from decreasing families of I-topologies (fuzzy topologies in Chang's sense), defined on a set X. 相似文献
87.
Ray Leslie Withers Carlos Otero-Diaz Adrian Gómez-Herrero Albert Prodan Lasse Norén 《Journal of solid state chemistry》2005,178(10):3159-3168
Ternary derivatives of 1T-TaS2 have been synthesized and the variation in the highly structured diffuse intensity distributions characteristic of such materials carefully monitored to investigate the effect that such substitution has upon the band structures and Fermi surfaces (FSs) of the materials. Removal of d electrons via the replacement of Ta ions with lower valent transition metal ions leads to a systematic increase in the radii of the characteristic structured diffuse intensity distribution. Extended Hückel tight binding calculations of the FSs of the doped samples are carried out and used to predict possible nesting wave-vectors. The results are in reasonably good agreement with the radii of the experimentally observed diffuse intensity distributions. 相似文献
88.
The vibrational dynamics of protein folding is analyzed in the framework of Tsallis statistics. We employ exact expressions
for classical harmonic oscillators by considering the unnormalized constraints. As q→1, we show that these approximations agree with the result of Gaussian network model. 相似文献
89.
Ana Luísa Daniel‐da‐Silva João Carlos Moura Bordado José Miguel Martín‐Martínez 《Journal of Polymer Science.Polymer Physics》2007,45(22):3034-3045
The degree of phase separation in several moisture‐cured poly(urethane urea)s (PUUs) was studied by FTIR spectroscopy, wide angle X‐ray diffraction (WAXD), and temperature‐modulated differential scanning calorimetry (TMDSC). This latter technique was shown to be particularly useful in analysing the degree of phase separation in PUU polymers. Both phase mixing and phase segregation coexisted in the PUUs and the degree of phase separation increased as the urea hard segment (HS) content in the PUU increased. The maximum solubility of urea HSs into the polyol soft segments (SSs) was achieved for 50 wt % urea HS content in diol‐based PUUs, whereas for triol‐based PUUs the highest solubility between HS and SS was reached for lower urea HS amount. Finally, the higher the urea HS content the higher the extent of phase separation in the PUU. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3034–3045, 2007 相似文献
90.
Oleg Palumbíny 《Czechoslovak Mathematical Journal》2003,53(2):467-477
The paper deals with oscillation criteria of fourth order linear differential equations with quasi-derivatives. 相似文献