全文获取类型
收费全文 | 79篇 |
免费 | 0篇 |
专业分类
化学 | 44篇 |
数学 | 26篇 |
物理学 | 9篇 |
出版年
2021年 | 1篇 |
2018年 | 1篇 |
2016年 | 1篇 |
2013年 | 3篇 |
2012年 | 2篇 |
2011年 | 2篇 |
2010年 | 1篇 |
2008年 | 2篇 |
2007年 | 1篇 |
2006年 | 1篇 |
2004年 | 3篇 |
2003年 | 5篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 4篇 |
1975年 | 1篇 |
1965年 | 1篇 |
1937年 | 1篇 |
1928年 | 2篇 |
1916年 | 1篇 |
1913年 | 2篇 |
1909年 | 2篇 |
1908年 | 1篇 |
1906年 | 2篇 |
1903年 | 1篇 |
1902年 | 1篇 |
1901年 | 1篇 |
1900年 | 1篇 |
1899年 | 2篇 |
1877年 | 1篇 |
1868年 | 1篇 |
排序方式: 共有79条查询结果,搜索用时 343 毫秒
71.
V.G. Albano G. Ciani A. Fumagalli S. Martinengo W.M. Anker 《Journal of organometallic chemistry》1976,116(3):343-352
The solid state structure of the cluster complex undecacarbonyltetrarhodate(2—) has been determined in the salt (PPh3NPPh3)2[Rh4(CO)11], which crystallizes in the space group P with cell constants a 22.394(3), b 14.351(2), c 11.937(2) Å, α 93.05(2)°, β 96.25(2)°, υ 88.38(2)°, Z = 2. The structure was refined by least-squares to a conventional discrepancy factor R of 0.060, based on 3884 reflection intensities collected by counter methods. The metal atom cluster is a distorted tetrahedron to which the ligands are bound four terminally and seven edge bridging; the idealized symmetry of the anion is C2[itv. The RhRh distances range from 2.662(2) to 2.986(2) Å, and are discussed in terms of ligand topology and the localized character of the anionic charge. 相似文献
72.
P. Chini G. Ciani L. Garlaschelli M. Manassero S. Martinengo A. Sironi F. Canziani 《Journal of organometallic chemistry》1978,152(2):C35-C38
[Ir4(CO)11X]? anions are obtained by reaction of halide and pseudo-halide ions with Ir4(CO)12. X-ray determination of the structure of [Ir4(CO)11Br]? shows that the carbonyl arrangement differs from that of the parent Ir4(CO)12, and is similar to that known for Co4(CO)12; one terminal CO group in the basal M3(CO)9 moiety is replaced by the bromide ligand, and two of the bridging CO groups become markedly asymmetric. 相似文献
73.
Gianfranco Ciani Angelo Sironi Paolo Chini Secondo Martinengo 《Journal of organometallic chemistry》1981,213(2):C37-C40
The anions [Rh6(CO)15X]?, with X = COEt and CO(OMe), have been studied by single-crystal X-ray diffraction. They contain octahedral rhodium clusters, with mean metalmetal distances of 2.779 and 2.765 », respectively. The carbonyl stereochemistry in the two anions is similar to that of Rh6(CO)16, with one terminal CO group replaced by the X ligand. The RhC(carbomethoxy) bond distance (1.96(2) ») is significantly shorter than the RhC(acyl) distance (2.06(2) »). 相似文献
74.
75.
76.
77.
Kondo A Kajiro H Noguchi H Carlucci L Proserpio DM Ciani G Kato K Takata M Seki H Sakamoto M Hattori Y Okino F Maeda K Ohba T Kaneko K Kanoh H 《Journal of the American Chemical Society》2011,133(27):10512-10522
Selective synthetic routes to coordination polymers [Cu(bpy)(2)(OTf)(2)](n) (bpy = 4,4'-bipyridine, OTf = trifluoromethanesulfonate) with 2- and 3-dimensionalities of the frameworks were established by properly choosing each different solvent-solution system. They show a quite similar local coordination environment around the Cu(II) centers, but these assemble in a different way leading to the 2D and 3D building-up structures. Although the two kinds of porous coordination polymers (PCPs) both have flexible frameworks, the 2D shows more marked flexibility than the 3D, giving rise to different flexibility-associated gas adsorption behaviors. All adsorption isotherms for N(2), CO(2), and Ar on the 3D PCP are of type I, whereas the 2D PCP has stepwise gas adsorption isotherms, also for CH(4) and water, in addition to these gases. The 3D structure, having hydrophilic and hydrophobic pores, shows the size-selective and quadrupole-surface electrical field interaction dependent adsorption. Remarkably, the 2D structure can accommodate greater amounts of gas molecules than that corresponding to the inherent crystallographic void volume through framework structural changes. In alcohol adsorption isotherms, however, the 2D PCP changes its framework structure through the guest accommodation, leading to no stepwise adsorption isotherms. The structural diversity of the 2D PCP stems from the breathing phenomenon and expansion/shrinkage modulation. 相似文献
78.
The performance in anodic stripping voltammetry (ASV) of hemispherical mercury microelectrodes, fabricated by electrodeposition of liquid mercury on the surface of Pt microdisks which were surrounded by a rather thick or thin insulating shield, was compared. The Pt microdisks were produced by sealing a wire of 25 μm diameter into a glass capillary, and by coating the cylindrical length of the Pt wire with a cathodic electrophoretic paint. The ratio of the overall tip radius b, to the basal radius of the electrode a, so-called RG = b/a, was equal to 110 ± 10 and 1.52 ± 0.01 for the thick- and thin-shielded microdisk, respectively. The mercury microelectrodes were characterized by cyclic voltammetry at 1 mV s−1, in 1 mM Ru(NH3)63+ aqueous solution. The steady-state voltammogram recorded with the thin-shielded mercury microelectrode displayed less hysteresis, while the steady-state current was about 30% higher than that of the thicker one. This was a consequence of the additional flux due to diffusion from behind the plane of the electrode. The flux enhancement, which was operative at the thin-shielded mercury microelectrode during the deposition step in the ASV experiments, allowed recording stripping peaks for Cd and Pb, which resulted about 32% larger than those recorded at the thicker shielded mercury microelectrode, under same experimental conditions.The usefulness of the thin-shielded mercury microelectrode for ASV measurements in real samples was verified by determining the content of heavy metal ions released in the pore water (pH 4.5) of a soil slurry. 相似文献
79.
G. Casasanta D. Ciani R. Garra 《Journal of Quantitative Spectroscopy & Radiative Transfer》2012,113(2):194-197
Possible deviations from exponential attenuation of radiation in a random medium have been recently studied in several works. These deviations from the classical Beer–Lambert law were justified from a stochastic point of view by Kostinski (2001) [1]. In his model he introduced the spatial correlation among the random variables, i.e. a space memory. In this note we introduce a different approach, including a memory formalism in the classical Beer–Lambert law through fractional calculus modelling. We find a generalized Beer–Lambert law in which the exponential memoryless extinction is only a special case of non-exponential extinction solutions described by Mittag–Leffler functions. We also justify this result from a stochastic point of view, using the space fractional Poisson process. Moreover, we discuss some concrete advantages of this approach from an experimental point of view, giving an estimate of the deviation from exponential extinction law, varying the optical depth. This is also an interesting model to understand the meaning of fractional derivative as an instrument to transmit randomness of microscopic dynamics to the macroscopic scale. 相似文献