全文获取类型
收费全文 | 317篇 |
免费 | 7篇 |
国内免费 | 1篇 |
专业分类
化学 | 152篇 |
晶体学 | 1篇 |
力学 | 2篇 |
数学 | 47篇 |
物理学 | 103篇 |
无线电 | 20篇 |
出版年
2022年 | 5篇 |
2021年 | 12篇 |
2020年 | 4篇 |
2018年 | 2篇 |
2017年 | 6篇 |
2016年 | 2篇 |
2015年 | 6篇 |
2014年 | 4篇 |
2013年 | 20篇 |
2012年 | 14篇 |
2011年 | 23篇 |
2010年 | 11篇 |
2009年 | 14篇 |
2008年 | 14篇 |
2007年 | 12篇 |
2006年 | 18篇 |
2005年 | 18篇 |
2004年 | 7篇 |
2003年 | 17篇 |
2002年 | 20篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1989年 | 3篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 3篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1966年 | 1篇 |
1961年 | 1篇 |
1956年 | 2篇 |
1955年 | 1篇 |
1940年 | 1篇 |
1937年 | 1篇 |
1928年 | 1篇 |
排序方式: 共有325条查询结果,搜索用时 15 毫秒
11.
Tarak Saied Nourchaine Jelaiel Mohamed Lotfi Efrit Yves Fort Corinne Comoy 《Tetrahedron》2017,73(11):1489-1494
We report herein a short and efficient synthesis of benz[e][1,2,4]- or [d][1,2,6]oxadiazepines and benzo[f][1,3,5]triazocines from easily prepared N-aryl iminoesters. The strategy involves a bis-nucleophile reagent (hydroxylamine or guanidine) that promotes a one-step ring closure from the starting functionalized iminoesters. 相似文献
12.
13.
On heating with hydroxylamine and on subsequent treatment with ferric chloride, pyrrolidonecarboxylic acid gives a colour reaction. This reaction can be used for the quantitative estimation of glutamic acid in protein hydrolyzates since this acid is almost completely converted into pyrrohdonecarboxylic acid at 125° and pH 3–4. 相似文献
14.
15.
Dorkenoo KD Gillot F Crégut O Sonnefraud Y Fort A Leblond H 《Physical review letters》2004,93(14):143905
We report an experimental and theoretical study on the optimization of (2+1)D self-written waveguide formation inside a photopolymerizable material. The accurate control of the refractive index value inside the bulk of the material during the polymerization process gives us the opportunity to define a virtual core and a virtual cladding for the system. The V value which characterizes the guidance properties of a fiber can be applied to this propagation. The control of the V value allows us to propagate single mode or multimode waveguides on a few centimeters. Numerical simulations of these waveguides based on a paraxial model including both photopolymerization and Kerr effect give very good agreement with our experimental results. 相似文献
16.
The lithiation pathway of 2-chloro and 2-methoxypyridine with LDA and LTMP has been investigated using deuterated probes. The availability of both H-6 and H-3 protons on the pyridine nucleus was found to be critical to ensure complete C-3 lithiation. We thus concluded that the C-3 lithiation was not a straightforward process. A mechanism involving precomplexation of lithium dialkylamides near the H-6 proton and formation of a 3,6-dilithio pyridine intermediate is proposed. 相似文献
17.
Two 87Rb condensates ( F = 2, m(f) = 2, and m(f) = 1) are produced in highly displaced harmonic traps and the collective dynamical behavior is investigated. The mutual interaction between the two condensates is evidenced in the center-of-mass oscillations as a frequency shift of 6.4(3)%. Calculations based on a mean-field theory well describe the observed effects of periodical collisions both on the center-of-mass motion and on the shape oscillations. 相似文献
18.
Fort S Birikaki L Dubois MP Antoine T Samain E Driguez H 《Chemical communications (Cambridge, England)》2005,(20):2558-2560
Oligosaccharidic moieties of GM(2) and GM(3) gangliosides bearing an allyl or a propargyl aglycon, are efficiently biosynthesized on the gram scale by growing metabolically engineered Escherichia coli cells in the presence of the corresponding lactoside acceptors and sialic acid. 相似文献
19.
Dr. Nguyet Trang Thanh Chau Maxime Meyer Dr. Shinsuke Komagawa Dr. Floris Chevallier Prof. Yves Fort Prof. Masanobu Uchiyama Prof. Florence Mongin Dr. Philippe C. Gros 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(41):12425-12433
Homoleptic lithium tri‐ and tetraalkyl zincates were reacted with a set of bromopyridines. Efficient and chemoselective bromine–metal exchanges were realized at room temperature with a substoichiometric amount of nBu4ZnLi2?TMEDA reagent (1/3 equiv; TMEDA=N,N,N′,N′‐tetramethylethylenediamine). This reactivity contrasted with that of tBu4ZnLi2?TMEDA, which was inefficient below one equivalent. DFT calculations allowed us to rationalize the formation of N???Li stabilized polypyridyl zincates in the reaction. The one‐pot difunctionalization of dibromopyridines was also realized using the reagent stoichiometrically. The direct creation of C? Zn bonds in bromopyridines enabled us to perform efficient Negishi‐type cross‐couplings. 相似文献
20.
da Silva UG de F Melo MA da Silva AF de Farias RF 《Journal of colloid and interface science》2003,260(2):302-304
This publication reports the adsorption of crude oil on vermiculite samples, expanded and hydrophobized with carnauba (Copernícia Cerífera) wax. The adsorption studies were performed by using columns filled with the vermiculite matrices and by dispersion of the vermiculite samples in an oil-water (50 ppm of oil) emulsion. The hydrate vermiculite exhibits a very low adsorption capacity against crude oil. On the other hand, anhydrous (expanded) and hydrophobized matrices show a high adsorption capacity. The 10% hydrophobized matrix show a 50% increased adsorption capacity, in comparison with the expanded one. For adsorption performed in the water-oil emulsion, saturation of the solid hydrophobized matrix is achieved after 60 min. The hydrophobized samples exhibit adsorption factors in the 0.7-1.0 range. 相似文献