全文获取类型
收费全文 | 450篇 |
免费 | 11篇 |
国内免费 | 6篇 |
专业分类
化学 | 259篇 |
晶体学 | 3篇 |
力学 | 2篇 |
数学 | 92篇 |
物理学 | 111篇 |
出版年
2020年 | 5篇 |
2019年 | 4篇 |
2017年 | 5篇 |
2015年 | 7篇 |
2014年 | 9篇 |
2013年 | 19篇 |
2012年 | 5篇 |
2011年 | 13篇 |
2010年 | 5篇 |
2009年 | 4篇 |
2008年 | 11篇 |
2007年 | 12篇 |
2006年 | 23篇 |
2005年 | 12篇 |
2004年 | 14篇 |
2003年 | 11篇 |
2002年 | 14篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 11篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 11篇 |
1994年 | 13篇 |
1993年 | 12篇 |
1992年 | 11篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 9篇 |
1982年 | 14篇 |
1981年 | 14篇 |
1980年 | 4篇 |
1979年 | 18篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1971年 | 4篇 |
1970年 | 4篇 |
1969年 | 4篇 |
1968年 | 4篇 |
1965年 | 6篇 |
1963年 | 3篇 |
排序方式: 共有467条查询结果,搜索用时 15 毫秒
1.
2.
R. Schuster H. Hajak M. Reinwald W. Wegscheider D. Schuh M. Bichler G. Abstreiter 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):236
The confinement energy of T-shaped quantum wires (QWRs), which were fabricated by the cleaved edge overgrowth technique in a way that the QWRs form at the intersection of In0.2Al0.8As stressor layers and the overgrown (1 1 0) GaAs quantum well (QW), is examined using micro-photoluminescence spectroscopy. Photoluminescence (PL) signals from individual QWRs can be spatially resolved, since the strained films are separated by 1 μm wide Al0.3Ga0.7As layers. We find that due to the tensile strain being transmitted to the QW, the confinement energy of the QWRs rises systematically up to 40 meV with increasing thickness of the stressor layers. By reducing the excitation power to 0.1 μW the QWR PL emission occurs 48 meV redshifted with respect to the QW. All QWR peaks exhibit smooth lineshapes, indicating the absence of pronounced exciton localization. 相似文献
3.
4.
Gröger H Hummel W Buchholz S Drauz K Nguyen TV Rollmann C Hüsken H Abokitse K 《Organic letters》2003,5(2):173-176
[reaction: see text] An enzyme-compatible biphasic reaction media for the asymmetric biocatalytic reduction of ketones with in situ cofactor regeneration has been developed. In this biphasic reaction media, which is advantageous for reactions at higher substrate concentrations, both enzymes (alcohol dehydrogenase and FDH from Candida boidinii) remain stable. The reductions with poorly water-soluble ketones were carried out at substrate concentrations of 10-200 mM, and the optically active (S)-alcohols were formed with moderate to good conversions and with up to >99% ee. 相似文献
5.
Stephen W. Bayles Suzy Beckham Paige R. Leidig Anne Montrem Mervin L. Taylor Tony M. Wright Ying WU Merlyn D. Schuh 《Photochemistry and photobiology》1991,54(2):175-181
The phosphorescence properties of 6-bromo-2-naphthyl sulfate (BNS) in aqueous solution were studied. The phosphorescence lifetime is several hundred microseconds and is self-quenched. Although a fluorescent photoproduct is formed from BNS, it does not interfere with the decay properties of triplet-state BNS and its utility as a probe of the accessibility of the heme group in heme proteins. Quenching of BNS phosphorescence does not occur for the non-heme protein lysozyme and apomyoglobin but occurs by a dynamic mechanism with a quenching constant of 1-2 x 10(9) M-1 s-1 for cytochrome c and myoglobin and with a quenching constant of 6.2 x 10(9) M-1 s-1 for protoporphyrin IX. The phosphorescence of an inclusion complex of 1-bromonaphthalene and beta-cyclodextrin is not quenched by heme-containing proteins. The temperature and viscosity dependencies of the rate with which BNS phosphorescence is quenched by microperoxidase-11 are consistent with unit quenching efficiency. These results indicate that quenching of BNS phosphorescence occurs only upon contact with the quencher, and the quenching constant can be used to assess the degree of accessibility of the heme group. 相似文献
6.
Electron deficient 1,2-diacylcyclopropenes represent synthetic equivalent for both acylcarbenes and vinylcarbenes; in their cycloreaction with ynamines aminofuranes and/or aminocyclopentadienes are formed. 相似文献
7.
The spironaphthalen-2-ones 2, 10 and 18 were prepared by N-bromosuccinimide (NBS) oxidation of 1, 9 and 17 respectively, whereas spironaphthalen-1-ones 24 and 25 were obtained by treating 23 with NBS. The stereoisomeric reduction products 29, 30 and 32 obtained from 24 and 25 , gave the pentacyclic compound 33 on treatment with polyphosphoric acid. 相似文献
8.
9.
10.
Karlheinz Gröchenig 《Monatshefte für Mathematik》1985,100(3):171-182
We study the properties of sequences (c
n
) in a compact groupG such that (x
n
) being (weakly) well-distributed implies (c
n
x
n
) being (weakly) well-distributed and give a complete characterisation in terms of almost constant sequences as well as a generalisation to non-compact locally compact groups. 相似文献