全文获取类型
收费全文 | 475篇 |
免费 | 5篇 |
国内免费 | 3篇 |
专业分类
化学 | 377篇 |
晶体学 | 1篇 |
力学 | 15篇 |
数学 | 38篇 |
物理学 | 52篇 |
出版年
2022年 | 7篇 |
2021年 | 4篇 |
2020年 | 7篇 |
2019年 | 4篇 |
2018年 | 6篇 |
2017年 | 2篇 |
2016年 | 9篇 |
2015年 | 7篇 |
2014年 | 14篇 |
2013年 | 24篇 |
2012年 | 30篇 |
2011年 | 28篇 |
2010年 | 17篇 |
2009年 | 14篇 |
2008年 | 24篇 |
2007年 | 24篇 |
2006年 | 21篇 |
2005年 | 27篇 |
2004年 | 29篇 |
2003年 | 33篇 |
2002年 | 33篇 |
2001年 | 8篇 |
2000年 | 8篇 |
1999年 | 8篇 |
1998年 | 6篇 |
1997年 | 9篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 7篇 |
1993年 | 8篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有483条查询结果,搜索用时 31 毫秒
451.
The structures of mass selected silver cluster cations Ag19 +, Ag38 +, Ag55 +, Ag59 +, Ag75 +, and Ag79 + have been probed at a temperature of 100 K by trapped ion electron diffraction. The structure assignment is carried out by comparison of the experimental scattering intensity with theoretical scattering functions of calculated candidate structures obtained by density functional theory. For the cluster sizes studied the resulting experimental data are invariably best described by structures based on the icosahedral motif, while closed packed structures can be ruled out. 相似文献
452.
The action of borontrifluoride etherate on methyl isopimarate 7,8 epoxides has been studied. A backbone rearrangement and the obtention of compounds with new skeletons are reported. 相似文献
453.
[reaction: see text] The anodic oxidation of pyrogallol derivatives produces chemically unstable o-quinone heterodienes, which are trapped in situ by enamine dienophiles through regiospecific inverse-electron-demand Diels-Alder reactions. The possibility of introducing variations in both cycloaddition partners gives rise to highly substituted 1,4-benzodioxin cycloadducts with up to five elements of diversity. The reactions proceed under mild conditions with a good efficiency. The methodology should be amenable to the assembly of libraries of biologically relevant heterocycles. 相似文献
454.
A rapid and stereoselective access to novel polycyclic indolyldiamines is described. The key step involves simple chemoselective transformations of a common bicyclic aminal intermediate, easily available on a large scale from an enantiomerically pure cyano oxazolopiperidine precursor. 相似文献
455.
[reaction: see text] Terminal alumination of alkynes by DIBALH or trimethylaluminum can be performed in a simple manner in the presence of a small amount of triethylamine. This new Lewis-base-catalyzed process delivers mixed alkynyldialkylalanes of great interest, without the need of an initial deprotonation step with lithium or sodium derivatives followed by a transmetalation. 相似文献
456.
457.
The Lamb waves are used for the ultrasonic characterization of welds because of their relative long-range propagation. In this paper, a simplified model of a weld-strip between two identical semi-infinite elastic layers is investigated. The reflected and transmitted ultrasonic fields are expressed by modal series whose coefficients are obtained by application of orthogonality relation. Comparisons with solutions obtained by finite elements wave propagation simulations are made. The energy balance between the incident and the scattered waves is also used to verify the accuracy of the obtained modal amplitudes. 相似文献
458.
Michel Kruglanski Martine De Mazière 《Journal of Quantitative Spectroscopy & Radiative Transfer》2005,94(1):117-125
When performing line-by-line simulations of atmospheric high-resolution infrared spectra, a large portion of the computation time is spent in the calculation of the absorptions by the far wings of the absorption lines. For applications in which one is interested mainly in evaluating the effective absorption in a microwindow, a computationally less expensive method has been developed. The method is faster than the explicit line-by-line calculation by a factor proportional to the number of line wings that contribute to the absorption in the simulated microwindow. This paper presents the method and demonstrates its performances in the 700- infrared band. Typically one obtains a gain in computation time of order 25. 相似文献
459.
Hennekinne JA Gohier M Maire T Lapeyre C Lombard B Dragacci S 《Journal of AOAC International》2003,86(2):332-339
The European Commission has designed a network of European Union-National Reference Laboratories (EU-NRLs), coordinated by a Community Reference Laboratory (CRL), for control of hygiene of milk and milk products (Council Directive 92/46/ECC). As a common contaminant of milk and milk products such as cheese, staphylococcal enterotoxins are often involved in human outbreaks and should be monitored regularly. The main tasks of the EU-CRLs were to select and transfer to the EU-NRLs a reference method for detection of enterotoxins, and to set up proficiency testing to evaluate the competency of the European laboratory network. The first interlaboratory exercise was performed on samples of freeze-dried cheese inoculated with 2 levels of staphylococcal enterotoxins (0.1 and 0.25 ng/g) and on an uninoculated control. These levels were chosen considering the EU regulation for staphylococcal enterotoxins in milk and milk products and the limit of detection of the enzyme-linked immunosorbent assay test recommended in the reference method. The trial was conducted according to the recommendations of ISO Guide 43. Results produced by laboratories were compiled and compared through statistical analysis. Except for data from 2 laboratories for the uninoculated control and cheese inoculated at 0.1 ng/g, all laboratories produced satisfactory results, showing the ability of the EU-NRL network to monitor the enterotoxin contaminant. 相似文献
460.