全文获取类型
收费全文 | 103篇 |
免费 | 6篇 |
专业分类
化学 | 69篇 |
力学 | 2篇 |
数学 | 8篇 |
物理学 | 30篇 |
出版年
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 2篇 |
2015年 | 5篇 |
2012年 | 5篇 |
2011年 | 5篇 |
2009年 | 4篇 |
2008年 | 4篇 |
2006年 | 4篇 |
2005年 | 2篇 |
2004年 | 3篇 |
2003年 | 4篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
1948年 | 3篇 |
排序方式: 共有109条查询结果,搜索用时 911 毫秒
11.
12.
13.
Spatzek S Greilich A Economou SE Varwig S Schwan A Yakovlev DR Reuter D Wieck AD Reinecke TL Bayer M 《Physical review letters》2011,107(13):137402
Coherent interactions between spins in quantum dots are a key requirement for quantum gates. We have performed pump-probe experiments in which pulsed lasers emitting at different photon energies manipulate two distinct subsets of electron spins within an inhomogeneous InGaAs quantum dot ensemble. The spin dynamics are monitored through their precession about an external magnetic field. These measurements demonstrate spin precession phase shifts and modulations of the magnitude of one subset of oriented spins after optical orientation of the second subset. The observations are consistent with results from a model using a Heisenberg-like interaction with μeV strength. 相似文献
14.
Ch. Schwan F. Martin G. Jakob J.C. Martinez H. Adrian 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(3):477-481
We have investigated the crystal structure and the ferroelectric properties of BaTiO3 thin films with YBa2Cu3O as the bottom and Au as the top electrode. Epitaxial heterostructures of YBa2Cu3O and BaTiO3 were prepared by dc and rf sputtering, respectively. The crystal structure of the films was characterised by X-ray diffraction.
The ferroelectric behaviour of the BaTiO3 films was confirmed by hysteresis loop measurements using a Sawyer Tower circuit. We obtain a coercive field of 30 kV/cm
and a remanent polarisation of 1.25 μC/cm2. At sub-switching fields the capacitance of the films obeys a relation analogous to the Rayleigh law. This behaviour indicates
an interaction of domain walls with randomly distributed pinning centres. At a field of 5 MV/m we calculate a 3% contribution
of the irreversible domain wall motion to the total dielectric constant.
Received 24 June 1999 and Received in final form 27 August 1999 相似文献
15.
Cover Picture: Metal‐Free Addition/Head‐to‐Tail Polymerization of Transient Phosphinoboranes,RPH‐BH2: A Route to Poly(alkylphosphinoboranes) (Angew. Chem. Int. Ed. 46/2015) 下载免费PDF全文
16.
Shabi Abbas Zaidi Seung Mi Lee Zeid A. AL Othman Abdullah M. AL Majid Won Jo Cheong 《Chromatographia》2011,73(5-6):517-525
Some acidic chiral templates were used to prepare open tubular (OT) molecule imprinted polymer (MIP) capillary columns to explore the effects of molecular structures of templates on chiral recognition capabilities and to verify the feasibility of the general MIP preparation protocol introduced in the previous study. The templates are phenyl carboxylic acids and their derivatives. Optimization was carried out for chiral separation of template enantiomers for each MIP column through varying pH and composition of eluent. It was found that the preparation protocol can be successfully applied for the appropriate templates with functional groups fulfilling the three-points interaction rule. The chiral separation performances were quite satisfactory for MIPs of such templates although they are yet inferior to the separation performances of the MIP columns fabricated with the templates of profen drugs (2-arylpropionic acids with a large substituent on the phenyl ring). Subtle variations of the template molecular structures have been found to be critical to enhance chiral recognition ability of the resultant MIP column. 相似文献
17.
We study a first-order identification problem in a Banach space. We discuss the nondegenerate and mainly the degenerate case. As a first step, suitable hypotheses on the involved closed linear operators are made in order to obtain unique solvability after reduction to a nondegenerate case; the general case is then handled with the help of new results on convolutions. Some applications to partial differential equations motivate this abstract approach.Communicated by I. GalliganiWork partially supported by MIUR (Ministero dell’ Istruzione, dell’ Università e dalla Ricerca), Project PRIN 2004011204 “Analisi Matematica nei Problemi Inversi,” and by the University of Bologna Funds for Selected Research Topics. 相似文献
18.
Thomas J. Schwan Raymond Freedman Jay R. Pollack 《Journal of heterocyclic chemistry》1983,20(5):1351-1353
The preparation, structure elucidation and antibacterial activity of 6-ethyl-6,9-dihydro-9-oxopyrazolo-[3,4-f]quinoline-8-carboxylic acid are reported. 相似文献
19.
In KCl interstitially diffusing neutral hydrogen atoms (H
i
0
) can be trapped near substitutional Li+ ions. The new center possesses a characteristic absorption band at 250nm, at the long wavelength side of the knownH
i
0
absorption band (235nm). EPR measurements reveal, that the hydrogen atoms are closely connected to the Li+ ions at a cation lattice site forming (LiH)+ molecules. Below 70K hydrogen and lithium occupy a fixed relative position to each other in a (111) crystal direction: the hydrogen shows a superhyperfine interaction to three equivalent Cl– neighboring ions. Above 70K the hydrogen exhibits a superhyperfine interaction to six equivalent chlorine neighbors, interpreted by a rapid reorientational motion of the (LiH)+ molecule within the cation vacancy. The high temperature interaction parameters can be explained as the time average of the low temperature values. A qualitative explanation of the optical absorption of the (LiH)+ center is given. 相似文献
20.
Enolate additions to chiral N-sulfonyloxaziridines providing enantiomerically enriched α-hydroxy carbonyl compounds is a reaction of importance, yet a clear understanding of the factors governing stereoinduction in these transformations remains ambiguous. This is despite, previous computational studies, one by Bach et al. employing truncated model systems exploring oxygen atom transfer to an unsubstituted lithium enolate and another by our own group. In clarifying this reactivity we report here a computational study examining oxygen atom transfer from 1-S-(+)-(10-camphorsulfonyl)oxaziridine, viz., archetypal Davis chiral oxaziridine to substituted Li, Na, K enolates offering improved mechanistic understanding. From this investigation, a revised model is offered revealing the metal cation, chelation effects and sterics as decisive stereocontrolling factors in enolate additions to chiral N-sulfonyloxaziridines affording enantiomerically enriched α-hydroxy carbonyl compounds. 相似文献