全文获取类型
收费全文 | 346篇 |
免费 | 14篇 |
专业分类
化学 | 223篇 |
晶体学 | 7篇 |
力学 | 13篇 |
数学 | 49篇 |
物理学 | 68篇 |
出版年
2022年 | 5篇 |
2019年 | 9篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 11篇 |
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 13篇 |
2012年 | 18篇 |
2011年 | 19篇 |
2010年 | 8篇 |
2009年 | 8篇 |
2008年 | 19篇 |
2007年 | 24篇 |
2006年 | 20篇 |
2005年 | 16篇 |
2004年 | 12篇 |
2003年 | 10篇 |
2002年 | 11篇 |
2001年 | 15篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1988年 | 2篇 |
1986年 | 3篇 |
1985年 | 11篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 12篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1969年 | 1篇 |
1967年 | 2篇 |
1958年 | 1篇 |
1897年 | 1篇 |
1895年 | 1篇 |
1888年 | 1篇 |
1884年 | 2篇 |
排序方式: 共有360条查询结果,搜索用时 15 毫秒
41.
Exciton—defect interaction in KI between 4 and 77 K is measured through the study of the intrinsic luminescence of irradiated crystals excited by both u.v. and electron irradiation. Results are interpreted by a possible athermal diffusion of the non-relaxed exciton at low temperature. 相似文献
42.
A first order magnetoelectric effect with α = 10-2 is measured on a powder sample of DyCoO3, due to the Dy3+ ions. The metamagnetic behaviour is demonstrated. 相似文献
43.
Ti4O7 is a striking example of the difficulties involved in the simultaneous control of crystal growth and composition. In this respect, the usual back-transport step must be avoided because it results to the formation of mixed phases. However, an appropriate H2 heat treatment can reduce these mixed crystals into single phase single crystals. This result is ascertained by accurate and sensitive physical methods. Finally suitable pulling transport experiments lead to the growth of centimeter long crystals. 相似文献
44.
Dany-Jack Mercier 《Journal of Pure and Applied Algebra》2003,179(3):273-285
Hermitian forms, exponential sums and linear algebra give us the opportunity to construct two trace-codes and obtain their parameters. 相似文献
45.
Ch. Bailly M. Daumerie R. Legras J. P. Mercier 《Journal of Polymer Science.Polymer Physics》1985,23(4):751-770
The presence of organic acid salts in bisphenol-A polycarbonate (PC) completely modifies the crystallization mechanism, the melting behavior, and the morphology of the polymer. Organic salts are not ordinary nucleating agents for PC since they react with the polymer, producing metal phenoxide chain ends. On reaction, abundant instaneous nucleation is induced. The seeds are likely to be polymer crystalline fragments preexisting in the melt. The phenoxide chain ends significantly increase the growth rate of the crystalline phase. Melting points and enthalpies of fusion are unusually high, suggesting a high degree of crystalline perfection. Thick multilamellar crystals, which are likely to contain chains in extended configuration, are observed by electron microscopy. No trace of spherulitic morphology is found. The chemical instability of PC containing ionic chain ends is also shown to seriously affect the crystallization rate, the maximum degree of crystallinity, and the melting point. 相似文献
46.
Fifty-four amines used as antioxidants and/or antiozonants for elastomers were separated on silica gel thin-layer plates with benzene and benzene-ethyl acetate-acetone (100:5:1) as developing solvents and N-chloro-2,6-dichloro-p-benzoquinone monoimine in buffered alkaline medium as spray reagent. Benzene-n-hexane (50:50) was used to separate diheptyl- and dioctyldiphenylamines. The active agents of several imprecisely defined products were identified and the relationships between some mixtures were elucidated. The method highlights the numerous minor components of these very impure industrial compounds. Some theoretical correlations between the chemical structures, the RF values and the colours of the spots were also established. 相似文献
47.
Summary We consider some equilibrium finite element methods for two-dimensional elasticity problems. The stresses and the displacements are approximated by using piecewise linear functions. We establishL
2-estimates of orderO(h
2) for both stresses and displacements. 相似文献
48.
Prebetanin, a minor companion of betanin in the red beet, was isolated and found to be the 6′-sulfuric acid half-ester of betanin. The arguments are based on elemental analyses, partial hydrolysis and methanolysis, and on comparison of the NMR-spectra of prebetanin and betanin, and of their derivatives. 相似文献
49.
Conclusion Les paramètres qui décrivent le fonctionnement des transistors sont complexes et dépendent de la fréquence. Ceci rend le calcul des schémas long et laborieux. La dépendance des impédances d'entrée et de sortie de la fréquence, d'une part, et des impédances de charge et de source, d'autre part, est souvent très gnante. A ces inconvénients nous pouvons opposer les avantages suivants:Facilité d'alimentation sur batteries tout à fait courantes et absence d'échauffement. Ces deux avantages entraînent les suivants: une stabilité exceptionnelle des performances et l'absence totale des perturbations de 50 Hz dues au réseau. Dans les oscillateurs pilotes, les transistors nous semblent préférables aux lampes pour des fréquences inférieures à 5 MHz (50 MHz pour drift-transistor), à condition de bien découpler le transistor du circuit oscillant. 相似文献
50.
Phuoc KT Corde S Shah R Albert F Fitour R Rousseau JP Burgy F Mercier B Rousse A 《Physical review letters》2006,97(22):225002
We demonstrate that betatron x-ray radiation accurately provides direct imaging of electrons trajectories accelerated in laser wakefields. Experimental far field x-ray beam profiles reveal that electrons can follow similar transverse trajectories with typical excursions of 1.5 microm+/-0.5 microm in the plane of laser polarization and 0.7 microm+/-0.2 microm in the plane perpendicular. 相似文献