全文获取类型
收费全文 | 140篇 |
免费 | 6篇 |
国内免费 | 2篇 |
专业分类
化学 | 50篇 |
晶体学 | 10篇 |
力学 | 13篇 |
数学 | 3篇 |
物理学 | 72篇 |
出版年
2020年 | 8篇 |
2019年 | 2篇 |
2018年 | 13篇 |
2017年 | 3篇 |
2016年 | 9篇 |
2015年 | 13篇 |
2014年 | 7篇 |
2013年 | 40篇 |
2012年 | 1篇 |
2011年 | 1篇 |
2010年 | 4篇 |
2009年 | 6篇 |
2008年 | 5篇 |
2007年 | 4篇 |
2006年 | 5篇 |
2005年 | 2篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2002年 | 3篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有148条查询结果,搜索用时 515 毫秒
141.
New N-sulfonylpyrimidine derivatives 1-(p-toluenesulfonyl)uracil (1), 1-(p-toluenesulfonyl)thymine (2), 5-bromo-1-(p-toluenesulfonyl)uracil (3), 1-(methanesulfonyl)uracil (4), 1-(1-naphthylsulfonyl)uracil (5), and 1-(1-naphthylsulfonyl)thymine (6) were prepared by the condensation reaction of silylated pyrimidine derivatives with selected sulfonyl chlorides in acetonitrile. Some members of the series showed unexpected crystal properties as a consequence of their conformational chirality in the solid state. Compounds 1 and 5 exhibited chiral crystallization, which was, in the case of 1, accompanied by the formation of racemically twinned crystals regardless of the solvent used, while 5 gave a conglomerate of enantiomorphous crystals. For 2, 3, and 6, substituents at the C-5 position of the pyrimidine ring prevented chiral crystallization by influencing the crystal packing. Analysis of the crystal structures of 1, 4, and 5, reveals the influence of the arylsulfonyl group on the occurrence or absence of chiral crystallization. 相似文献
142.
The continuity of a substructure across the interface is considered a necessary condition for the formation of a twin. The application of the analysis of the eigensymmetry of crystallographic orbits to the derivation of this structural continuity is briefly reviewed and applied to the analysis of the {101} twin in marcasite. This analysis shows that one fourth of the structure, but half of the substructure near the composition surface, is common to the two orientations realized in the twin, the operation mapping the common atoms in the twinned domains being an n‐glide occurring every one fourth of the period along the direction quasi‐perpendicular to the twin plane. The existence of this significant common substructure justifies and explains the formation of the twin. 相似文献
143.
Jan Fbry Lubomír Havlk Monika Ku
erkov Michal Duek 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(6):533-535
The title structures NaGdS2 (sodium gadolinium sulfide), NaLuS2 (sodium lutetium sulfide) and NaYS2 (sodium yttrium sulfide) were redetermined in order to improve the structural information available for the family of group 1 and thallium rare earth sulfides, which are isostructural with the rhombohedral α‐NaFeO2 structure type. In particular, the present investigation has been directed at the rhombohedral sodium rare earth sulfides. The observed dependence of the fractional coordinate z(S2−) on the identity of the rare earth element in the newly determined structures is in agreement with the known structures of the potassium and rubidium analogues. Crystals of NaGdS2 and NaLuS2 display obverse–reverse twinning. 相似文献
144.
ABSTRACTWe studied martensitic phase transformation, crystal structure and twinned microstructure of resulting martensite of a Ni-Mn-Ga single crystal as essential conditions for magnetic shape memory effect. Thermal dependence of electric resistivity, magnetic susceptibility and dilatation measurements were measured to characterise kinetics of the transformation. With the help of XRD analysis and optical microscopy we evaluated the hierarchical twinning microstructure in the 10M martensite. 相似文献
145.
146.
E. Kubota 《Crystal Research and Technology》1999,34(4):539-548
This paper analyzes crystal shape monitoring for automatic diameter control (ADC) during the liquid encapsulated Czochralski (LEC) growth of InP crystals. The crystal diameter (shape) is monitored numerically (diagrammatically) by using a disc approximation approach based on precise weight and pulling length measurements. The error in the diameter calculation based on the approximation is estimated to be sufficiently small for practical use. The monitoring accuracy was investigated for crystal bodies with nearly flat growth interfaces, and for their shoulder portions with largely convex growth interfaces. For the straight body portions, the accuracy depended on diameter, d, and improved from ±15% for d=10 mm to ±3% for d=50mm. For the shoulder portions, the diameter was monitored with nearly the same accuracy. This method has therefore made it possible to monitor the growing crystal visually in real time, and was applied to the growth of <111> InP crystals with a cone angle of less than 39° and a smooth appearance to avoid twinning. 相似文献
147.
The structure of the oxygen‐deficient compound 7Bi2O3 · 2WO3, a fluorite‐derivative phase considered a candidate for electronic applications because of its high ionic conductivity, is investigated by singlecrystal X‐Ray diffraction employing Ag‐Kα radiation (λ = 0.5608 Å) to minimize the effect of the absorption by the heavy metals. The space‐group type is I41, the acentric subgroup of I41/a that was previously suggested from powder‐diffraction data and precession‐camera photographs. Lattice parameters are a = 12.513(2), c = 11.231(4) (Z = 2.5). The sample is twinned by syngonic merohedry, class I, with volume ratio of the individuals 0.58/0.42. The ordering of W partly confirms previous models, with one W fully occupying one of the sites on special position. However, the remaining W goes in a site on general position, which shares with Bi, resulting thus more diluted in the structure. The oxygen vacancies are partly ordered in three of the ten anion sites. 相似文献
148.
This paper reports on the microstructural changes occurring within molybdenum single crystals after shock treatment with an excimer laser‐system in a confined ablation mode with different number of impacts. Using different complementary investigation methods (optical microscopy, scanning electron microscopy and transmission electron microscopy) it is found that slip and twinning are active modes of deformation during the shock‐induced plastic deformation. After laser treatment with a single laser pulse slip bands on {112} planes containing several microscopic twins are the dominating microstructural feature, whereas further laser‐shock‐processing leads to the formation of a homogeneous arrangement of screw dislocations, tangles and loops. Deformation modes and microstructure in laser shocked samples prove to be quite similar to those of explosive shocked specimens although the laser‐induced peak pressure is about an order of magnitude lower than that during explosive loading.It is shown that the laser shock‐induced hardening increases with increasing number of impacts in the range from 1 to 6 impacts. This shock‐induced strengthening is correlated with the overall dislocation density. 相似文献