全文获取类型
收费全文 | 312篇 |
免费 | 12篇 |
国内免费 | 3篇 |
专业分类
化学 | 243篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 19篇 |
物理学 | 60篇 |
出版年
2023年 | 4篇 |
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 11篇 |
2015年 | 7篇 |
2014年 | 9篇 |
2013年 | 17篇 |
2012年 | 18篇 |
2011年 | 23篇 |
2010年 | 16篇 |
2009年 | 3篇 |
2008年 | 12篇 |
2007年 | 17篇 |
2006年 | 16篇 |
2005年 | 24篇 |
2004年 | 15篇 |
2003年 | 10篇 |
2002年 | 12篇 |
2001年 | 6篇 |
2000年 | 7篇 |
1999年 | 6篇 |
1998年 | 9篇 |
1997年 | 8篇 |
1996年 | 6篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1977年 | 1篇 |
1976年 | 2篇 |
排序方式: 共有327条查询结果,搜索用时 15 毫秒
321.
Freytag N Tokunaga Y Horvatić M Berthier C Shayegan M Lévy LP 《Physical review letters》2001,87(13):136801
The average electron spin polarization Rho of a two-dimensional electron gas confined in GaAs/GaAlAs multiple quantum wells was measured by NMR near the fractional quantum Hall state with filling factor nu = 2/3. Above this filling factor (2/3< or = nu < 0.85), a strong depolarization is observed corresponding to two spin flips per additional flux quantum. The most remarkable behavior of the polarization is observed at nu = 2/3, where a quantum phase transition from a partially polarized (Rho approximately 3/4) to a fully polarized (Rho = 1) state can be driven by increasing the ratio between the Zeeman and the Coulomb energy above a critical value eta(c) = Delta(Z)/Delta(C) = 0.0185. 相似文献
322.
Alan Tokunaga Prasad Varanasi 《Journal of Quantitative Spectroscopy & Radiative Transfer》1976,16(12):1057-1059
The intensity of the RQ0 branch of the v9 fundamental of ethane has been measured to be 0.74±0.09cm-2atm-1 at 300°K. Rotational structure of the laboratory spectrum is discussed by means of a comparison with a computed spectrum. 相似文献
323.
Masashi Tokunaga 《Frontiers of Physics》2012,7(4):386-398
In this article, studies on the magnetoelectric effects of multiferroic materials in high magnetic fields, particularly pulsed magnetic fields, are discussed and results for some representative materials are presented. In the discussions on representative materials, the relationship between the crystallographic symmetry and the linear magnetoelectric effect in Cr2O3 is introduced. Then drastic changes in polarization caused by magnetic transitions are discussed through a case study of manganites with a perovskite-type structure. In addition, high field studies on the magnetoelectric effects in BiFeO3, which is an exceptional multiferroic material, are presented and discussed in the framework of the Landau-Ginzburg theory. 相似文献
324.
2-Acetonyl or 2-phenacyl-l,2-dihydropyrimidines (5) were obtained by the reaction of β-sulfinyl or β-sulfenyl-α,β-unsaturated ketones (2 or 3) with diimines (1). The formation of 1,2-dihydropyrimidines (5) can be explained in terms of substitution reaction and subsequent Michael addition of amino group of diimines (1). 相似文献
325.
326.
Susumu Itoh Takuya Tokunaga Masayuki Kurihara Shin Aoki 《Tetrahedron: Asymmetry》2013,24(24):1583-1590
The direct aldol reaction between cyclic ketones and 4-nitrobenzaldehyde catalyzed by chiral Zn2+ complexes of aminoacyl 1,4,7,10-tetraazacyclododecane is reported. The anti-aldol products were mainly formed in cyclohexanone/N-methylpyrrolidone(NMP)/MeOH with good diastereo- and enantioselectivity, while syn-aldol adducts were obtained as major products with good enantioselectivity in cyclohexanone/H2O and cyclohexanone/NMP/H2O. The fact that the UV/vis spectra of 2,6-diphenyl-4-(2,4,6-triphenyl-1-pyridinio)phenolate (Reichardt’s dye) were nearly identical in these solvent systems suggests that the switch in the relative configuration of the aldol products is induced by a large excess of H2O rather than the polarity of the solvent system. Furthermore, the addition of a small amount of TFA improved the enantioselectivity of the syn-aldol adducts produced in cyclohexanone/H2O with up to 92% ee (anti/syn ratio = 30:70). 相似文献
327.
Hiroyuki Yasui Takehisa Ishimaru Etsuko Tokunaga Motoo Shiro 《Journal of fluorine chemistry》2011,132(3):222-225
We disclose here a novel electrophilic fluorinating reagent, N-fluoro-(3,5-di-tert-butyl-4-methoxy)benzenesulfonimide (NFBSI) as a sterically demanding analogue of popular fluorinating reagent, N-fluorobenzenesulfonmide (NFSI). NFBSI improves the enantioselectivity of the products as much as 18% for the cinchona alkaloid-catalyzed enantioselective fluorination of silylenol ether compared to the use of NFSI. 相似文献