全文获取类型
收费全文 | 76篇 |
免费 | 0篇 |
专业分类
化学 | 37篇 |
力学 | 4篇 |
数学 | 1篇 |
物理学 | 34篇 |
出版年
2019年 | 1篇 |
2014年 | 2篇 |
2013年 | 1篇 |
2010年 | 1篇 |
2009年 | 1篇 |
2008年 | 4篇 |
2007年 | 1篇 |
2006年 | 1篇 |
2005年 | 3篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1976年 | 1篇 |
1935年 | 2篇 |
1928年 | 2篇 |
1924年 | 2篇 |
排序方式: 共有76条查询结果,搜索用时 140 毫秒
51.
52.
53.
54.
55.
56.
57.
Dussault PH Lee IQ Lee HJ Lee RJ Niu QJ Schultz JA Zope UR 《The Journal of organic chemistry》2000,65(25):8407-8414
The Lewis acid-mediated reaction of alkene nucleophiles with peroxyacetals provides an effective route for the synthesis of homologated peroxides and hydroperoxides. In the presence of Lewis acids such as TiCl(4), SnCl(4), and trimethylsilyl triflate, peroxyacetals and peroxyketals undergo reaction with allyltrimethylsilane, silyl enol ethers, and silyl ketene acetals to afford homoallyl peroxides, 3-peroxyketones, and 3-peroxyalkanoates, respectively. Reactions of peroxyacetals are Lewis acid dependent; TiCl(4) promotes formation of ethers while SnCl(4) and trimethylsilyl triflate promote formation of peroxides. Lewis acid-promoted reactions of silylated hydroperoxyacetals furnish silylated hydroperoxides, which can be deprotected to homologated hydroperoxides. Hydroperoxyketals undergo Lewis acid-mediated allylation to furnish 1,2-dioxolanes via attack of hydroperoxide on the intermediate carbocation. Lewis acid-mediated cyclization of unsaturated peroxyacetals furnishes 1,2-dioxanes, 1,2-dioxepanes, and 1,2-dioxacanes through 6-endo/exo, 7-endo/endo, and 8-endo/endo pathways. The corresponding reactions involving 6-endo/endo and 5-endo/exo pathways were unsuccessful. 相似文献
58.
Summary Crystal structures have been determined for two nickel complexes of the monodentate S-donating ligand 1-methyl imidazoline-2(3H)-thione (mimtH). The parainagnetic trans-octahedral complex, [Ni(mimtH)4Cl2], crystallises in an orthorhombic unit cell (a=12.459(1),b=13.078(1),c=15.406(1)Å, V=2510.24Å3,Z=4, space group Pbca). Final conventional R from 1848 observed data [F>4(F)] is 0.0273. The Ni–Cl distance is. 2.537(1) Å and the mean Ni–S distance is 2.479 Å.The diamagnetic complex, [Ni(mimtH)4](BF4)2, contains a distorted square-planar cation which is H-bonded. to [BF4]– anions. The complex crystallises in an orthorhombic unit cell [a=9.810(1),b=14.585(1),c=20.120(2)Å, V=2878.8Å3,Z=4, space group Pbcn]. Final conventional R from 1756 observed data [F>4(F)] is 0.0629. The average Ni–S distance is 2.216Å. 相似文献
59.
Eric S. Raper Peter Carty James R. Creighton Angela Miller William Clegg 《Transition Metal Chemistry》1988,13(5):356-360
Summary Imidazoline-2-thione (imtH
2) and 1-methylimidazoline-2-thione (mimtH) react with FeCl2·4H2O in rigorously anhydrous media producing complexes of general formula Fe(LH)2Cl2.Infrared and electronic spectra as well as room temperature magnetic moments are consistent with mononuelear, pseudotetrahedral species. The crystal structure of [Fe(mimHH)2Cl2] confirms this arrangement. The complex crystallises in a triclinic unit cell (a=7.376(2),b=7.595(2),c=15.043(4) Å. =76.80(1)°, =79.60(1)°, =61.90(1)°; V=721.13 Å3; space group=P1, Z=2). Final conventional R from 2267 observed data (F >4(F)) is 0.0271. Average bond lengths are 2.353 Å (Fe–S) and 2.265 Å (Fe–Cl). Angles at the metal range from 91.5(1)° to 114.5(1)°.Thermal degradation of the complexes in flowing air involves sequential loss of halogen and ligand with -Fe2O3 as the final product. The decomposition is exothermic in flowing dinitrogen. 相似文献
60.