全文获取类型
收费全文 | 786篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
化学 | 456篇 |
晶体学 | 3篇 |
力学 | 30篇 |
数学 | 89篇 |
物理学 | 218篇 |
出版年
2021年 | 9篇 |
2020年 | 21篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 14篇 |
2015年 | 11篇 |
2014年 | 16篇 |
2013年 | 30篇 |
2012年 | 35篇 |
2011年 | 35篇 |
2010年 | 11篇 |
2009年 | 16篇 |
2008年 | 22篇 |
2007年 | 28篇 |
2006年 | 27篇 |
2005年 | 38篇 |
2004年 | 39篇 |
2003年 | 26篇 |
2002年 | 28篇 |
2001年 | 22篇 |
2000年 | 19篇 |
1999年 | 17篇 |
1998年 | 19篇 |
1997年 | 13篇 |
1996年 | 13篇 |
1995年 | 14篇 |
1994年 | 11篇 |
1993年 | 22篇 |
1992年 | 21篇 |
1991年 | 8篇 |
1990年 | 17篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1981年 | 10篇 |
1980年 | 5篇 |
1978年 | 9篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1974年 | 12篇 |
1973年 | 13篇 |
1972年 | 7篇 |
1924年 | 5篇 |
1881年 | 3篇 |
排序方式: 共有796条查询结果,搜索用时 31 毫秒
171.
M. Kröckel A.X. Trautwein H. Winkler A.F. Arendsen W.R. Hagen 《Hyperfine Interactions》1998,113(1-4):3-14
Iron clusters are the catalytically active groups of many proteins. The basis building blocks of these clusters are few; they are all variants of three archetypal patterns: [Fe–O–Fe], [2Fe–2S], and [4Fe–4S]. Mössbauer spectroscopy, in conjunction with EPR spectroscopy, susceptometry and EXAFS, plays an important role in characterizing type, number, oxidation states and magnetic properties of such clusters in newly discovered proteins, and in detecting how valency and magnetism vary by passing through the catalytical cycle of these proteins. In this contribution we present the characterization of a novel iron cluster with unusual bridging and terminal ligands and metal coordinations. 相似文献
172.
A. C. Berkenbosch E. F. Kaasschieter J. H. M. ten Thije Boonkkamp 《Numerical Methods for Partial Differential Equations》1994,10(2):225-269
This article contains a survey of some important finite-difference methods for one-dimensional hyperbolic conservation laws. Weak solutions of hyperbolic conservation laws are introduced and the concept of entropy stability is discussed. Furthermore, the Riemann problem for hyperbolic conservation laws is solved. An introduction to finite-difference methods is given for which important concepts such as, e.g., conservativity, stability, and consistency are introduced. Godunov-type methods are elaborated for general systems of hyperbolic conservation laws. Finally, flux limiter methods are developed for the scalar nonlinear conservation law. © 1994 John Wiley & Sons, Inc. 相似文献
173.
174.
J. Förster Th. Hagen M. von Hoesslin J. Uhlenbusch 《Applied physics. B, Lasers and optics》1996,62(3):263-272
Absorption spectra of the gases SiH4, NH3, C2H2 and of SiH4/Ar and SiH4/B2H6 mixtures have been measured in the spectral range of the CO2 laser from 9.2 to 10.8 µm. In agreement with literature, silane shows the highest absorption (absorption coefficient = 3.3 × 10–2 Pa–1 m–1). The deviation of the measured absorption behaviour of silane from literature, as far as the pressure dependence is concerned, can be explained by the enhanced spectral energy density in our experiment. This is confirmed by a rate-equation model involving the basic mechanisms of V-V and V-T energy transfer between vibrationally excited silane molecules. In contrast to silane, the absorption coefficient of NH3 at the 10P(20) laser line is 4.5 × 10–4 Pa–1 m–1 atp = 20 kPa and has its maximum of 4.5 × 10–3 Pa–1 m–1 at the 10R(6) laser line. For C2H2 and B2H6, is even less ( 2.1 Ò 10–5 Pa–1 m–1 for C2H2). 相似文献
175.
176.
177.
178.
179.
Environmental trace-element analysis using a benchtop total reflection X-ray fluorescence spectrometer. 总被引:1,自引:0,他引:1
Hagen Stosnach 《Analytical sciences》2005,21(7):873-876
Total reflection X-ray fluorescence (TXRF) analysis is an established technique for trace-element analysis in various types of samples. Though expensive large-scale systems restricted the applications in the past, in this study the capability of a benchtop system for trace elemental analysis is reported. The suitability of this system for the mobile on-site analysis of heavy metal contaminated soils and sediments is reported as well as the possibilities and restrictions of TXRF for additional applications, including trace-element analysis of water, glass and biological samples. 相似文献
180.
Baucke E Behrends R Fuchs K Hagen R Kaatze U 《The Journal of chemical physics》2004,120(17):8118-8124
For solutions of four saccharides in water with alkaline-earth chlorides added ultrasonic attenuation spectra between 100 kHz and 2 GHz are reported and compared to those for carbohydrate solutions without salt. Calcium chloride does not alter the relaxation times in the spectra of D-glucose and D+-maltose solutions, reflecting the exocyclic hydroxymethyl group rotation, a saccharide-saccharide association, and, with the disaccharide, also motions of both rings of a molecule relative to one another. The spectra of D-xylose and D-fructose solutions are substantially changed by the salts. With both saccharides an additional term with relaxation time around some nanoseconds exists which is assigned to a rearrangement of a carbohydrate-cation complex. Other relaxation terms of these saccharide solutions are also subject to noticeable changes by the salt, indicating specific carbohydrate-cation interactions. The ultrasonic spectra show that such interactions may exist also with carbohydrates which do not display the particular hydroxyl group sequences that are considered to promote complexation with cations. 相似文献