全文获取类型
收费全文 | 483篇 |
免费 | 7篇 |
国内免费 | 1篇 |
专业分类
化学 | 334篇 |
晶体学 | 4篇 |
力学 | 13篇 |
数学 | 100篇 |
物理学 | 40篇 |
出版年
2023年 | 6篇 |
2022年 | 16篇 |
2021年 | 12篇 |
2020年 | 13篇 |
2019年 | 7篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 8篇 |
2015年 | 3篇 |
2014年 | 16篇 |
2013年 | 25篇 |
2012年 | 30篇 |
2011年 | 34篇 |
2010年 | 24篇 |
2009年 | 13篇 |
2008年 | 35篇 |
2007年 | 25篇 |
2006年 | 26篇 |
2005年 | 23篇 |
2004年 | 15篇 |
2003年 | 25篇 |
2002年 | 19篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 11篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 8篇 |
1995年 | 2篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1989年 | 2篇 |
1984年 | 4篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1968年 | 3篇 |
1915年 | 1篇 |
1912年 | 2篇 |
1905年 | 1篇 |
1903年 | 1篇 |
1899年 | 1篇 |
1897年 | 2篇 |
1894年 | 1篇 |
1892年 | 1篇 |
1889年 | 2篇 |
1888年 | 1篇 |
1882年 | 1篇 |
排序方式: 共有491条查询结果,搜索用时 0 毫秒
101.
Mastrorilli P Nobile CF Latronico M Gallo V Englert U Fanizzi FP Sciacovelli O 《Inorganic chemistry》2005,44(24):9097-9104
Dynamic NMR experiments on trans-[Pt(Cl)(PHCy2)2[P(X)Cy2]]z where X is a lone pair (1, z = 0), H (2, z = +1), S (3, z = 0), or O (4, z = 0) show that the rotation around the P(X)-Pt bond is hindered for all molecules studied, with deltaG++ ranging from 8.2 to 11.0 kcal/mol. The highest value of the series was calculated for trans-[Pt(Cl)(PHCy2)2[P(O)Cy2]] (4) where intramolecular P=O...H-P interactions act as a molecular brake at room temperature. Single-crystal X-ray diffraction confirms the presence of both intra and intermolecular P=O...H interactions in solid 4. In the case of [Pt(Cl)(PHCy2)3]Cl, multinuclear NMR analysis indicates the presence of a P-H...Cl- interaction in aromatic or halogenated solvents which could have also a minor effect on the rotational barrier around the P(X)-Pt bond. 相似文献
102.
103.
By condensation of the chlorides of the four isomeric fluorenecarboxylic acids, respectively of the three 1-, 3- and 4-fluorenonecarboxylic acids with fluorene, followed by reduction of the obtained mono-respectively diketones, the four difluorenylmethanes I, II, III and IV are synthesized. The oxydation of the diketones gives the corresponding triketones. Starting from the chloride of 4-fluorenecarboxylic acid and 1-methylfluorene, a methyl derivative of IV is analogically obtained. 相似文献
104.
Marcelo R. L. Oliveira José E. J. C. Graúdo Nivaldo L. Speziali Vito M. De Bellis 《Structural chemistry》1999,10(1):41-45
Potassium N-4-methylphenylsulfonyldithiocarbimate, K2(4-CH3C6H4SO2N=CS2), reacted with nickel(II) chloride hexahydrate and tetrabutylammonium bromide to form the bis(N-4-methylphenylsulfonyldithiocarbimate)nickelate(II) tetrabutylammonium salt (Bu4N)2[Ni(4-CH3C6H4S2C=NSO2)2]. The elemental analyses, IR and UV-Vis data obtained were consistent with the formation of a
diamagnetic planar complex. The 1H NMR and the 13C NMR spectra showed the expected signals for the dithiocarbimate moiety and the tetrabutylammonium cation. The single-crystal structure analysis showed that this substance crystallizes in the triclinic
space group with a = 10.474(3) Å, b = 10.767(3) Å, c = 13.657(3) Å and = 81.54(2)°, = 80.44(2)°, = 67.63(2)°, V = 1398.5(8) Å3, and Z = 2. The nickel atom is coordinated to four sulfur atoms. 相似文献
105.
[reaction: see text] The stereoselective synthesis of novel alpha-epoxy-beta-amino acids is described by a route that combines the chemistry of oxazolinyloxiranyllithiums with that of nitrones. The intermediate trioxadiazadispiro[2.0.4.3]undecanes 4 have been isolated and converted by hydrolysis into epoxy-5-isoxazolidinones 5 which can be transformed into the alpha-epoxy-beta-amino acids 8 by N-O reduction. 相似文献
106.
[reaction: see text] A stereoselective/stereospecific synthesis of polysubstituted tetrahydronaphthols based on the Michael addition of ortho-lithiated stilbene oxides to alpha,beta-unsaturated Fischer carbene complexes followed by an unusual cyclization of the corresponding intermediate in a 6-endo-tet mode is described. 相似文献
107.
108.
High-resolution infrared spectrum of CHD279Br: ro-vibrational analysis of the ν5 and ν9 fundamentals
ABSTRACTThe high-resolution infrared spectrum of CHD279Br has been investigated by Fourier transform spectroscopy in the range 700–900?cm?1 at an unapodized resolution of 0.0035?cm?1. This spectral region is characterised by the absorptions of the ν5 (814.5185?cm?1) and ν9 (716.9649?cm?1) fundamental bands, corresponding to H–C–Br deformation and CD2 rocking modes, respectively. The ν5 vibration of symmetry species A′ gives rise to an a-/c-hybrid band with a predominant a-type component, while the ν9 mode of A′′ symmetry produces a b-type envelope. The spectral analysis resulted in the identification of 5290 (J′?≤?63 and Ka′?≤?13) and 1657 (J′?≤?53 and Ka′?≤?12) transitions for ν5 and ν9 bands, respectively. The assigned data were fitted using the Watson’s S-reduced Hamiltonian in the Ir representation and the v5?=?1 and v9?=?1 state parameters up to the quartic centrifugal distortion terms have been obtained. From spectral simulations the dipole moment ratio |Δμa/Δμc| of the ν5 band has been determined to be 1.4?±?0.1 while the intensity ratio between ν5 and ν9 fundamentals has been estimated to have a value of 4.3?±?0.5. 相似文献
109.