全文获取类型
收费全文 | 156篇 |
免费 | 2篇 |
专业分类
化学 | 49篇 |
力学 | 1篇 |
数学 | 73篇 |
物理学 | 35篇 |
出版年
2021年 | 4篇 |
2020年 | 5篇 |
2019年 | 5篇 |
2018年 | 3篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2013年 | 4篇 |
2012年 | 9篇 |
2011年 | 4篇 |
2010年 | 3篇 |
2009年 | 2篇 |
2008年 | 5篇 |
2007年 | 2篇 |
2005年 | 2篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2002年 | 3篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1975年 | 8篇 |
1974年 | 5篇 |
1973年 | 7篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1969年 | 3篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 2篇 |
1965年 | 1篇 |
1963年 | 3篇 |
1962年 | 1篇 |
1961年 | 2篇 |
1960年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有158条查询结果,搜索用时 93 毫秒
31.
Sulphur contents of the original sample and the sample free from sulphur dioxide were determined by ICP-AES following nitric acid digestion under high pressure (using PAAR HPA equipment), and the total sulphur content was calculated from the difference between the results obtained. With the aim of preparing a sample free from sulphur dioxide, bound sulphur dioxide was released by sodium hydroxide, then after acidifying by phosphoric acid, boiling was carried out. Relative standard deviations of the results obtained for total sulphur, the sulphur without S(IV) and total sulphur dioxide were lower than 2.5, 3.5 and 5% respectively. Various amounts of sulphur (in the form of Na2SO4), added to wine samples, were successfully recovered between 95.5 and 104.9%. Based on comparative analyses performed by a widely accepted classic method, the indirect method developed was found to be adequate for the determination of total sulphur dioxide. The procedure is suitable for serial tests. 相似文献
32.
Viktor Kelemen Miklós Bege Dr. Dániel Eszenyi Nóra Debreczeni Dr. Attila Bényei Dr. Tobias Stürzer Prof. Dr. Pál Herczegh Prof. Dr. Anikó Borbás 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(64):14555-14571
A comprehensive optimization and mechanistic study on the photoinduced hydrothiolation of different d - and l - hexo- and pentoglycals with various thiols was performed, at the temperature range of RT to −120 °C. Addition of thiols onto 2-substituted hexoglycals proceeded with complete 1,2-cis-α-stereoselectivity in all cases. Hydrothiolation of 2-substituted pentoglycals resulted in mixtures of 1,2-cis-α- and -β-thioglycosides of varying ratio depending on the configuration of the reactants. Hydrothiolation of unsubstituted glycals at −80 °C proceeded with excellent yields and, except for galactal, provided the axially C2-S-linked isomers with high selectivity. Cooling was always beneficial to the efficacy, increased the yields and in most cases significantly raised the stereoselectivity. The suggested mechanism explains the different conformational preferences of the intermediate carbon-centered radicals, which is a crucial factor in the stereoselectivity of the reactions. 相似文献
33.
34.
We exhibit two relation algebra atom structures such that they are elementarily equivalent but their term algebras are not. This answers Problem 14.19 in Hirsch and Hodkinson’s text Relation Algebras by Games. 相似文献
35.
36.
The adsorption of pyridine on a clean Ag(110) surface was characterized with ultraviolet photoemission spectroscopy, flash desorption and Auger electron spectroscopy. Pyridine condenses on the silver surface below 190 K and rapidly forms multiple layers. At temperatures above 235 K pyridine is present in submonolayer concentrations. At 275 K pyridine is chemisorbed on Ag(110). 相似文献
37.
A family of k-subsets of an n-set such that no more than r have pairwise fewer than s elements in common is maximum (for sufficiently large n) only if consists of all the k-sets containing at least one of r fixed disjoint s-subsets. 相似文献
38.
39.
40.