全文获取类型
收费全文 | 123篇 |
免费 | 1篇 |
专业分类
化学 | 91篇 |
晶体学 | 4篇 |
数学 | 11篇 |
物理学 | 18篇 |
出版年
2023年 | 6篇 |
2022年 | 4篇 |
2021年 | 2篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 3篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 3篇 |
2014年 | 2篇 |
2013年 | 4篇 |
2012年 | 12篇 |
2011年 | 9篇 |
2010年 | 10篇 |
2009年 | 2篇 |
2008年 | 7篇 |
2007年 | 13篇 |
2006年 | 8篇 |
2005年 | 6篇 |
2004年 | 1篇 |
2003年 | 3篇 |
2002年 | 6篇 |
2001年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1992年 | 3篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有124条查询结果,搜索用时 15 毫秒
51.
52.
Diganta Choudhury Abhijit Banik Rupam Sarma 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(10):o524-o526
In the title compound, C19H15NO, the neutral molecules are held together in the crystal structure by very weak C—H...O interactions, giving rise to a linear chain‐like structure. The structure of the molecule has been optimized using density functional theory at the B3LYP/6‐31G(d) level and this is compared with the molecular structure in the solid state. The two structures show significant differences in the relative orientations of the aromatic rings, which is interesting for further supramolecular study. Apart from the crystal structure analysis, powder X‐ray diffraction, UV–visible and thermogravimetric analyses of the compound have been carried out. 相似文献
53.
Closed-shell contacts between two copper(I) ions are expected to be repulsive. However, such contacts are quite frequent and are well documented. Crystallographic characterization of such contacts in unsupported and bridged multinuclear copper(I) complexes has repeatedly invited debates on the existence of cuprophilicity. Recent developments in the application of Bader's theory of atoms-in-molecules (AIM) to systems in which weak hydrogen bonds are involved suggests that the copper(I)-copper(I) contacts would benefit from a similar analysis. Thus the nature of electron-density distributions in copper(I) dimers that are unsupported, and those that are bridged, have been examined. A comparison of complexes that are dimers of symmetrical monomers and those that are dimers of two copper(I) monomers with different coordination spheres has also been made. AIM analysis shows that a bond critical point (BCP) between two Cu atoms is present in most cases. The nature of the BCP in terms of the electron density, ρ, and its Laplacian is quite similar to the nature of critical points observed in hydrogen bonds in the same systems. The ρ is inversely correlated to Cu-Cu distance. It is higher in asymmetrical systems than what is observed in corresponding symmetrical systems. By examining the ratio of the local electron potential-energy density (V(c)) to the kinetic energy density (G(c)), |V(c)|/G(c) at the critical point suggests that these interactions are not perfectly ionic but have some shared nature. Thus an analysis of critical points by using AIM theory points to the presence of an attractive metallophilic interaction similar to other well-documented weak interactions like hydrogen bonding. 相似文献
54.
A new iridoid, shanzhiol (1), was isolated from the aerial parts of Mussaenda roxburghii. The structure was established by spectroscopic (including 2D NMR) and chemical methods. Shanzhiol (1) showed mild antibacterial activity against both Staphylococcus aureus and Escherichia coli with a MIC of 100 microg/mL by the broth dilution method. 相似文献
55.
Dinda B Debnath S Arima S Sato N Harigaya Y 《Chemical & pharmaceutical bulletin》2006,54(7):1030-1033
Four new iridoid glucosides, 5-dehydro-8-epi-adoxosidic acid, 5-dehydro-8-epi-mussaenoside, 10-O-dihydroferuloyldeacetyldaphylloside, and wendoside, together with one known iridoid glucoside, 8-epi-mussaenoside, beta-D-glucose, D-mannitol and beta-sitosterol have been isolated from the roots of Wendlandia tinctoria. On the basis of chemical and spectral analyses, the structures of new iridoid glucosides have been elucidated. 相似文献
56.
P.L. Majumder S. Joardar T.K. Chanda B.N. Dinda M. Banerjee A.B. Ray A. Chatterjee P. Varenne B.C. Das 《Tetrahedron》1979,35(9):1151-1157
Structures and absolute stereochemistry of (-)-echitoveniline, (-)-11-methoxyechitoveniline and (-)-11-methoxyechitovenedine, three new indole alkaloids of the vincadifformine type, isolated from the fruits and leaves of Alstonia venenata R.Br., have been established as 3b, 3c and 3d, respectively, on the basis of spectral and chemical evidence. A plausible mechanism of the LAH reduction of the δ-lactones8b and8c to the corresponding diols 9b and 9c has been discussed. 相似文献
57.
We report a system in which three distinct dynamic linkages, disulfide (S-S), imine (C=N), and coordinative (N-->metal) bonds were shown to be capable of simultaneous reversible exchange. The "disulfide layer" of the system under study consists of two homo-disulfides, bis(4-aminophenyl) disulfide 1 and bis(4-methoxyphenyl) disulfide 2 that equilibrate in the presence of catalytic amount of triethylamine to favor the formation of a hetero-disulfide product, 4-aminophenyl-4'-methoxyphenyl disulfide 3. The addition of 2-formylpyridine and a metal salt strongly perturbed this 1+2<-->3 equilibrium through the formation of metal complexes incorporating disulfide 1 as a subcomponent. CuI perturbed the equilibrium by a factor of 3.3, and FeII by a factor of 179, in both cases in favor of the homo-disulfides. The disulfide equilibrium could be further modified, following metal-complex formation, by coordinative (transmetallation: substitution of FeII for CuI) or covalent (imine exchange: the substitution of one amine residue for another) exchange. Thus, although the three kinds of dynamic linkages were demonstrated to be mutually compatible, changes at one kind of linkage could be used to predictably perturb an equilibrium involving another. 相似文献
58.
59.
Tirtha Bhattacharjee Pranjit Barman Tapan Thakuria Rupam Sarma Ranjan Dutta Kalita Bipul Sarma 《Heteroatom Chemistry》2013,24(6):502-509
4′‐Methylazobenzene‐2‐sulfenyl thio‐cyanate (MABS‐SCN) was synthesized in an aqueous medium and characterized by 1H nuclear magnetic resonance, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, and elemental analysis. The crystal structure was confirmed by single crystal X‐ray diffraction and its geometry was optimized in ground state by Hartree–Fock model and (B3LYP) density functional theory, and in solution (ethanol) using polarized continuum model at restricted HF using the basis set 6–31+G*. The compound crystallizes in orthorhombic space group Pbca, with unit cell parameters a = 7.165 (7) Å, b = 18.846 (2) Å, c = 20.379 (2) Å, V = 2752.1 (5) Å3, and Z = 8. It attains a planar thiadiazolium salt structure due to strong ortho azo–sulfur interaction imparting exceptional thermal stability, nonreactive solubility in aqueous medium, and high melting crystalline solid nature. A weak intramolecular C H…S type interaction, one C H…S type, four C H…N type intermolecular hydrogen bonds, and van der Waal's interactions are believed to be the stabilizing force for the crystal structure. MABS‐SCN was also tested for antimicrobial activity. 相似文献
60.