全文获取类型
收费全文 | 93篇 |
免费 | 0篇 |
专业分类
化学 | 52篇 |
晶体学 | 1篇 |
数学 | 2篇 |
物理学 | 38篇 |
出版年
2016年 | 1篇 |
2015年 | 5篇 |
2013年 | 7篇 |
2012年 | 3篇 |
2011年 | 6篇 |
2010年 | 1篇 |
2009年 | 1篇 |
2008年 | 3篇 |
2007年 | 6篇 |
2005年 | 4篇 |
2004年 | 3篇 |
2003年 | 7篇 |
2002年 | 4篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1997年 | 1篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1978年 | 1篇 |
排序方式: 共有93条查询结果,搜索用时 15 毫秒
61.
62.
A study on electron spin resonance (ESR) spectroscopic determination of exchange interactions in organic oligoradicals is given. When the intramolecular exchange couplingJ between, unpaired electron spins in nitroxide-based oligoradicals falls within the order of 10 Oe (1 mK or 10?3 cm?1 forg=2), which is on the same order as the hyperfine couplingA of magnetic nuclei such as nitrogen atoms of nitroxide radicals, the magnitude ofJ can be determined from the hyperfine splitting pattern of ESR spectra in solutions. This range of the exchange couplingJ is not detectable in conventional magnetic susceptibility measurements. We demonstrate an application of hyperfine ESR spectroscopy as a probe for the exchange coupling to a series of organic oligoradicals, which the authors have recently developed as building blocks for molecule-based magnetic materials. 相似文献
63.
Poly[5, 5′ - (dimethylsilylene) - 2, 2′ - dithienylene] (4a), poly[5, 5′ -(methylphenylsilylene)-2, 2′ -dithienylene] (4b), poly[5, 5′ -(1, 1, 2, 2-tetramethyldisilanylene)-2, 2′ -dithienylene] (4c), poly[5, 5′-(1, 2-dimethyl-1, 2-diphenyldisilanylene)-2, 2′ -dithienylene] (4d), poly[5, 5′-(1, 2, 2, 2-tetramethyldisilanylene)-2, 2′-dithienylene] (4e), and poly[5, 5′-(1, 1, 2, 2, 3, 3 - hexamethyltrisilanylene) - 2, 2′ -dithienylene] were synthesized by dehalogenative coupling of the respective bis(2-bromothienyl)- substituted mono, di- and tri-silanes with magnesium in the presence of a catalytic amount of a nickel(II) complex in 16–99% yields. The polymers thus obtained are light-yellow solids and soluble in common organic solvents. Molecular weights, Mw, of the polymers were measured and found to be 7800–35 000 by gel-permeation chromatography relative to polystyrene standards. The photochemical properties of the polymers (4a–4d) having silylene and disilanylene units were investigated. Only poly[5, 5′-(1, 2-dimethyl-1, 2-diphenyl-disilanylene)-2, 2′-dithienylene] (4d) was found to be photoactive, but the others were inactive. When the thin solid films prepared from the polymers 4a–4e by spin-coating were exposed to antimony(V) fluoride in vacuo, the films became conducting; their conductivities were determined to be 10?2 – 10?3 S cm?1 by the four-probe method. 相似文献
64.
Sato A Yokotani S Tadokoro T Tanaka S Angkawidjaja C Koga Y Takano K Kanaya S 《Journal of synchrotron radiation》2011,18(1):6-10
CutA1 is widely found in bacteria, plants and animals, including humans. The functions of CutA1, however, have not been well clarified. It is known that CutA1s from Pyrococcus horikoshii, Thermus thermophilus and Oryza sativa unfold at temperatures remarkably higher than the growth temperatures of the host organisms. In this work the crystal structure of CutA1 from the psychrotrophic bacterium Shewanella sp. SIB1 (SIB1-CutA1) in a trimeric form was determined at 2.7?? resolution. This is the first crystal structure of a psychrotrophic CutA1. The overall structure of SIB1-CutA1 is similar to those of CutA1 from Homo sapiens, Escherichia coli, Pyrococcus horikoshii, Thermus thermophilus, Termotoga maritima, Oryza sativa and Rattus norvergicus. A peculiarity is observed in the β2 strand. The β2 strand is divided into two short β strands, β2a and β2b, in SIB1-CutA1. A thermal denaturation experiment revealed that SIB1-CutA1 does not unfold completely at 363?K at pH 7.0, although Shewanella sp. SIB1 cannot grow at temperatures exceeding 303?K. These results indicate that the trimeric structural motif of CutA1 is the critical factor in its unusually high stability and suggest that CutA1 needs to maintain its high stability in order to function, even in psychrotrophs. 相似文献
65.
Upon excitation of carbon disulphide (CS2) molecules under UV light irradiation at 313?nm a gaseous mixture of CS2 and glyoxal deposited sedimentary aerosol particles only. The nucleation process of the aerosol particles was investigated by measuring the He–Ne laser light intensity scattered by the aerosol particles formed under light irradiation at 313?nm, and the chemical structure of the sedimentary particles was analysed by measuring the FT-IR and X-ray photoelectron spectra. On application of a magnetic field of up to 5?T, the nucleation process was decelerated and the chemical species originating from CS2 were less abundant. The results were compared with those obtained under visible light irradiation at 435.8?nm reported previously. Chemical reactions between CS2 and glyoxal molecules, which were responsive to the magnetic field, are discussed briefly. 相似文献
66.
The aim of this study was to establish the best manufacturing conditions for preparation by the direct compression method of tablets which contain microcapsules having a minimal destruction rate of the coating wall, show the same dissolution pattern as microcapsules, and have enough mechanical strength for practical use, and to elucidate the internal structure of the tablets under the best manufacturing conditions. Degree of destruction of the microcapsule wall was evaluated by the dissolution rate of the medicine in the microcapsules. To learn the mechanical strength of tablets, the crushing strength and friability were measured; their internal structure was analyzed by the porosity and pore size distribution. The best manufacturing conditions for the tablets were thus determined, and it was clarified by analysis of the internal structure that these conditions are markedly affected by the flowability of prescribed powders and the packing state at compression. 相似文献
67.
A system for characterization of a particular gaseous substance in a particular gaseous environment is developed. Five semiconductor gas sensors and a personal computer are used. The data sets obtained for three samples (acetone, acetic acid and ethanol) at four concentrations in 12 different environments were evaluated statistically. The accuracy of characterization was 85% to 96%. Although semiconductor gas sensors require 10–20 min to recover their initial conditions after individual measurements, this system could be used for continuous monitoring of a particular substance in the presence of different concentrations of the other substances. 相似文献
68.
69.
Moiré topography is able to determine the shape of an object, by pattern measuring, in a short time. Recently moiré topography has been used in various industrial fields because it has superior features that point measurement doesn't have. As it becomes popular various related techniques that fit specific needs have been developed and there is the prospect that moiré topography will become a more important measurement method and strengthen its position in the near future.
This paper explains the grid irradiation method and the grid projection method as the basis of the moiré topography measurement method and describes the existing status and prospects of utilizing moiré topography measurement in the applied fields of shape measurement, flatness measurement and detection of abnormality. 相似文献
70.
T. Miyazaki R. Inoue K. Nishida T. Kanaya 《The European physical journal. Special topics》2007,141(1):203-206
We have studied thermal expansion of free standing polystyrene thin films using X-ray reflectivity to elucidate the glass
transition temperature and the thermal expansivity. We found that the glass transition temperature Tg decreased with the film thickness, depending on molecular weight. The reduction in the free standing films is much larger
than in the supported films on Si substrate, suggesting that some segmental motions are activated due to free surfaces on
both sides in the free standing films. We also found that the thermal expansivity in the glass and the melt decreased with
the film thickness. This decrease must be attributable to chain confinement effects. 相似文献