全文获取类型
收费全文 | 304篇 |
免费 | 14篇 |
专业分类
化学 | 241篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 1篇 |
物理学 | 74篇 |
出版年
2021年 | 5篇 |
2020年 | 2篇 |
2019年 | 8篇 |
2017年 | 3篇 |
2016年 | 16篇 |
2015年 | 10篇 |
2014年 | 3篇 |
2013年 | 14篇 |
2012年 | 16篇 |
2011年 | 14篇 |
2010年 | 5篇 |
2009年 | 4篇 |
2008年 | 6篇 |
2007年 | 4篇 |
2006年 | 9篇 |
2005年 | 9篇 |
2004年 | 8篇 |
2003年 | 7篇 |
2002年 | 4篇 |
2001年 | 6篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 12篇 |
1997年 | 8篇 |
1996年 | 8篇 |
1995年 | 10篇 |
1994年 | 16篇 |
1993年 | 2篇 |
1992年 | 11篇 |
1991年 | 13篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1985年 | 2篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 3篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1969年 | 4篇 |
1965年 | 1篇 |
1961年 | 2篇 |
1935年 | 2篇 |
1932年 | 2篇 |
1921年 | 2篇 |
排序方式: 共有318条查询结果,搜索用时 562 毫秒
81.
82.
C. M. Castaneda R. Gearhart B. Sanii P. A. J. Englert D. M. Drake R. C. Reedy 《Journal of Radioanalytical and Nuclear Chemistry》1992,160(2):387-393
Planetary gamma-ray spectroscopy can be used to chemically analyze the top soil from planets in future planetary missions. The production from inelastic neutron interaction plays an effective role in the determination on the C and H at the surface. The gamma-ray production cross section from the strongest lines excited in the neutron bombardment of Fe have been measured by the use of a time analyzed quasi-mono-energetic neutron beam and a high purity germanium detector. The results from En=6.5, 32, 43, and 65 MeV are presented. 相似文献
83.
84.
85.
This paper reports 261 substituent increments for the 1H? NMR. chemical shifts (solvent: CDCl3) of the 18- and 19-methyl protons of 9β, 10α(retro)-steroids relative to 5β,9β,10α,-androstane. The increments were calculated by a least-squares procedure from 1334 spectra of 759 different steroids. 相似文献
86.
William Raven Thomas Joschko Irmgard Kalf Ulli Englert 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(3):184-188
At the molecular level, the enantiomerically pure square‐planar organoplatinum complex (SP‐4‐4)‐(R)‐[2‐(1‐aminoethyl)‐5‐fluorophenyl‐κ2C1,N][(R)‐1‐(4‐fluorophenyl)ethylamine‐κN](isocyanato‐κN)platinum(II), [Pt(C8H9FN)(NCO)(C8H10FN)], and its congener without fluorine substituents on the aryl rings adopt the same structure within error. The similarities between the compounds extend to the most relevant intermolecular interactions, i.e. N—H…O and N—H…N hydrogen bonds link neighbouring molecules into chains along the shortest lattice parameter in each structure. Differences between the crystal structures of the fluoro‐substituted and parent complex become obvious with respect to secondary interactions perpendicular to the classical hydrogen bonds; the fluorinated compound features short C—H…F contacts with an F…H distance of ca 2.6 Å. The fluorine substitution is also reflected in reduced backbonding from the metal cation to the isocyanate ligand. 相似文献
87.
Kevin Lamberts Mihaela‐Diana erb Ulli Englert 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(4):271-275
In catena‐poly[copper(II)‐di‐μ‐chlorido‐μ‐proline‐κ2O:O′], [CuCl2(C5H9NO2)]n, two symmetry‐independent metal cations adopt distorted octahedral coordination, typical for d9 Jahn–Teller systems. Each chloride bridge is involved in both a short and a very long interaction with a CuII centre. The centrosymmetric crystal structure contains homochiral chains of opposite handedness which extend along the shortest lattice parameter (i.e. a). The O:O′‐bridging coordination mode of proline, although a common motif for such complexes in general, is remarkable for CuII; the vast majority of amino acid derivatives of this cation are characterized by N,O‐chelation. 相似文献
88.
The new ligand‐deficient chain polymer [Hg(μ‐Br)2(3,5‐Br2py)]∞ has been obtained in form of single crystals by thermolysis of the ligand‐rich [Hg(μ‐Br)2(3,5‐Br2py)2]∞ at 180 °C at ambient pressure. From this reaction, high quality crystals of the product are directly accessible. The title compound features HgII cations in a distorted square‐pyramidal coordination; their metal centers aggregate via edge‐sharing with asymmetric halide bridges to chains in which all apical N donor ligands are oriented to the same side of the [Hg(μ‐Br)2]∞ backbone. The new polymer cannot be prepared by stoichiometric reaction in solution. 相似文献
89.
Englert JM Hauke F Feng X Müllen K Hirsch A 《Chemical communications (Cambridge, England)》2010,46(48):9194-9196
Unsubstituted hexa-peri-hexabenzocoronene (HBC)-a small and well defined model system for graphite/graphene-was exfoliated and dissolved in water and the resulting individualized nano graphene sheets were characterized spectroscopically for the first time. 相似文献
90.
Calucci L Cloke FG Englert U Hitchcock PB Pampaloni G Pinzino C Puccini F Volpe M 《Dalton transactions (Cambridge, England : 2003)》2006,(35):4228-4234
M(eta(6)-arene)(2) species (M = Cr, arene = 1,3,5-Me(3)C(6)H(3); M = Mo, arene = 1,3,5-Me(3)C(6)H(3), 1,3,5-(i)Pr(3)C(6)H(3)), have been prepared by a modified Fischer-Hafner synthesis or by metal vapour techniques. The reaction of Cr(eta(6)-1,3,5-Me(3)C(6)H(3))(2) with the fulvene derivatives pentacarbomethoxycyclopentadiene (pcmcpH), 1-benzoyl-6-hydroxy-6-phenylfulvene (dbcpH), or 1-benzoyl-3-nitro-6-hydroxy-6-phenylfulvene (dbncpH) proceeds with evolution of dihydrogen and formation of the ionic derivatives [Cr(eta(6)-1,3,5-Me(3)C(6)H(3))(2)][E], where E = pcmcp, dbcp, or dbncp. Mo(eta(6)-arene)(2) derivatives (arene = toluene, 1,3,5-Me(3)C(6)H(3), 1,3,5-(i)Pr(3)C(6)H(3)) are oxidized to [Mo(eta(6)-arene)(2)](+) by pcmcpH. The crystal and molecular structures of [M(eta(6)-1,3,5-R(3)C(6)H(3))(2)][pcmcp] (M = Cr, R = Me; M = Mo, R = Me, (i)Pr) have been solved by X-ray single crystal diffraction. 相似文献