全文获取类型
收费全文 | 2639篇 |
免费 | 127篇 |
国内免费 | 12篇 |
专业分类
化学 | 1816篇 |
晶体学 | 14篇 |
力学 | 49篇 |
综合类 | 1篇 |
数学 | 348篇 |
物理学 | 550篇 |
出版年
2023年 | 20篇 |
2021年 | 63篇 |
2020年 | 93篇 |
2019年 | 87篇 |
2018年 | 40篇 |
2017年 | 45篇 |
2016年 | 88篇 |
2015年 | 84篇 |
2014年 | 74篇 |
2013年 | 128篇 |
2012年 | 137篇 |
2011年 | 154篇 |
2010年 | 83篇 |
2009年 | 78篇 |
2008年 | 124篇 |
2007年 | 115篇 |
2006年 | 111篇 |
2005年 | 80篇 |
2004年 | 84篇 |
2003年 | 66篇 |
2002年 | 64篇 |
2001年 | 33篇 |
2000年 | 26篇 |
1999年 | 31篇 |
1998年 | 23篇 |
1997年 | 33篇 |
1996年 | 36篇 |
1995年 | 20篇 |
1994年 | 34篇 |
1993年 | 32篇 |
1992年 | 31篇 |
1991年 | 20篇 |
1989年 | 20篇 |
1988年 | 25篇 |
1987年 | 19篇 |
1985年 | 24篇 |
1984年 | 22篇 |
1983年 | 24篇 |
1982年 | 20篇 |
1981年 | 27篇 |
1979年 | 27篇 |
1978年 | 44篇 |
1977年 | 25篇 |
1976年 | 34篇 |
1975年 | 28篇 |
1974年 | 31篇 |
1973年 | 22篇 |
1972年 | 19篇 |
1971年 | 24篇 |
1970年 | 24篇 |
排序方式: 共有2778条查询结果,搜索用时 16 毫秒
1.
Pan Huang Dawen Xu Robert M. Reich Felix Kaiser Boping Liu Fritz E. Kühn 《Tetrahedron letters》2019,60(24):1574-1577
A first example of an Et2Zn mediated silylation of 1-aklynes is reported. A series of functional groups are tolerated in this reaction. Mechanistic studies support Zn alkynilides as intermediates in the reaction. This reaction protocol provides a practical method for the preparation of alkynylsilanes and expands the application of organometallic zinc in organic synthesis. 相似文献
2.
3.
Sherif Yehia C. Mitros Sanjeev Kumar S. Jha Glenn M. Julian R. A. Dunlap 《Hyperfine Interactions》1987,34(1-4):415-418
The systematics of hyperfine magnetic fields at sp impurities on the Z-sites in Co based Heusler alloys are investigated. New TDPAC measurements of Cd hyperfine fields are reported. 相似文献
4.
In this paper, three new direct Mutually Orthogonal Latin Squares (MOLS) constructions are presented for 7 MOLS(24), 7 MOLS(75) and 8 MOLS(36); then using recursive methods, several new constructions for 7 and 8 MOLS are obtained. These reduce the largest value for which 7 MOLS are unknown from 780 to 570, and the largest odd value for which 8 MOLS are unknown from 1935 to 419. © 2003 Wiley Periodicals, Inc. 相似文献
5.
6.
Eggenhffner R. Masini R. Bellingeri E. Cimberle M. R. Ferdeghini C. Costa G. A. Kaiser E. Signorelli E. 《Il Nuovo Cimento D》1994,16(10):1659-1664
Il Nuovo Cimento D - The formation of Hg-based HTSC materials was investigated through the development of non-conventional techniques. The former was based on a singlestep synthesis at temperatures... 相似文献
7.
Data about the existence of native HO? CH2? CH2? OH (MEG) in natural wines and champagne has led to delicate questions because of legal decisions already made to declare wine or champagne illegal for sale if the MEG concentrations found are above 10 mg/liter. Action has been taken because of the DEG (diethylene glycol) disaster in European wines of 1985…86. An incorrect legal decision was made due to the belief that MEG cannot be produced biochemically by grape vines. A further reason may be lack of correct data on native MEG trace concentrations, as a result of the special behavior of this diol. As first member of a homologous series whose higher members (C4) are normally found in all wines at quite high concentration levels, MEG shows extremely adsorptive behavior. The solution of the chromatographic problems is summarized in this paper. MEG concentrations in Riesling as example are in the range of 2 to 6 mg/liter and can easily be increased by biotechnological steps to a level of around 10 to 60 mg/liter. This is again due to the specific adsorptive behavior of MEG, which can be enriched on filter surfaces and displaced when the wine acidity changes with changing types. In order to control and guarantee the qualitative and quantitative results of MEG analyses we used a combination of Deans heart cutting on-line with Multi-Chromatography. It was easy to produce false data by many otherwise useful single column or two-dimensional separation processes, etc. 相似文献
8.
Ultrasonic analysis of edible fats and oils 总被引:7,自引:0,他引:7
Low intensity ultrasound is a powerful analytical technique for investigating the physico-chemical properties of many biological and non-biological materials. In this article its application for the characterization of edible fats and oils is assessed. Ultrasound can be used to determine the dynamic rheology and composition of oils, the oil content and droplet size of emulsions and the solid fat content of partially crystalline emulsions. It is capable of rapid and precise measurements, is non-destructive and non-invasive, can be used on-line or off-line and is relatively inexpensive. Ultrasonic techniques will therefore prove a useful addition to the existing analytical techniques used to characterize fats and oils. 相似文献
9.
10.
The 29th PME research forum on theories included only one European perspective on mathematics education. In order to convey trends in theory usage in Europe we compile, survey and analyze a large subset of the research papers from the 4th European Congress on Mathematics Education (CERME4). That is, this paper includes a discussion of trends seen within CERME4 reports1 on theory usage by European researchers inseven of the fourteen working groups and (a) Outlines similarities and differences in theory usage and (b) takes a futuristic stance on ways in which researchers from different traditions could understand each other. Such an enterprise would further Hans-Georg Steiner's vision of bridging theoretical traditions which are independently formulated in different regions of the world. 相似文献