全文获取类型
收费全文 | 442篇 |
免费 | 1篇 |
国内免费 | 1篇 |
学科分类
数理化 | 444篇 |
出版年
2017年 | 2篇 |
2015年 | 3篇 |
2013年 | 26篇 |
2012年 | 7篇 |
2011年 | 4篇 |
2010年 | 3篇 |
2009年 | 3篇 |
2008年 | 9篇 |
2007年 | 7篇 |
2005年 | 3篇 |
2004年 | 9篇 |
2003年 | 11篇 |
2002年 | 14篇 |
2001年 | 5篇 |
2000年 | 8篇 |
1999年 | 9篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 13篇 |
1995年 | 15篇 |
1994年 | 12篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 14篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 14篇 |
1985年 | 14篇 |
1984年 | 12篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 18篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1978年 | 10篇 |
1977年 | 11篇 |
1976年 | 13篇 |
1975年 | 8篇 |
1974年 | 15篇 |
1973年 | 18篇 |
1972年 | 13篇 |
1971年 | 17篇 |
1970年 | 5篇 |
1967年 | 6篇 |
1966年 | 3篇 |
1963年 | 6篇 |
1956年 | 1篇 |
1943年 | 1篇 |
排序方式: 共有444条查询结果,搜索用时 15 毫秒
1.
On P? P Containing Cyclic Compounds. II. Reaction of N,N'-dimethylthiourea with phenyl dichlorophosphane yields 1.4-dimethyl-2. 3-diphenyl-1.4.2.3-diazadiphospholidine-5-thione-2-sulfide ( II ). The compound is characterized by its nmr, vibration and mass spectra as well as the results of an X-ray structural analysis. Byproduct of the reaction is N-(N,N'-dimethylcarbamimidoyl)-N,N'-dimethyl thiourea hydrochloride ( III ), which crystallizes with pyridinium chloride. Molecular and crystal structure are reported. With methyl dichlorophosphane N,N'-dimethylthiourea forms 1.2.3.4-tetramethyl-1.4.2.3-diazadiphospholidine-5-thione-2-sulfide ( IV ), which is characterized by its nmr and vibration spectra. 相似文献
2.
N.M.R. Investigation of Methylphosphonium Chloride The n.m.r. spectra of [CH3PH3]Cl in aqueous hydrochloric acid as solvent and of [OP(CH3) (OCH2CH2Cl)OCH2? ]2 in C6D6 und CD2Cl2 are described. 31P n.m.r. resonances with a line width at half height of 55 Hz are found for the H2O? HCl solutions of [CH3PH3]Cl in the solid state at 183 K. 相似文献
3.
The photoelectron(PE)spectrum of tricyclo[3.1.0.02,6] hex-2-ene(benzvalene 1) has been recorded. The first four bands in the PE spectrum of 1 can be assigned to transitions to 2B2, 2A1, 2A2 and 2B1 states of 11. This assignment is discussed in terms of the results of semiempirical and ab initio calculations on 1. Furthermore the highest occupied MO's of 1 are derived qualitatively from an interaction diagram between a distorted bicyclobutane and an ethylene moiety. 相似文献
4.
On Trichlorophosphazo Compounds from Nitriles. III. The Reaction between Acrylonitrile and PCl3. The reaction of PCl3 with acrylonitrile at higher temperatures gives CH2Cl? CCl2? CCl2? N? PCl3 ( II ). On pyrolysis of (II), CH2Cl? CCl2? CN (IV) is form- ed. Treatment of (II) with SO, results in CHzCL? CCl2? CCl?N-P(0)Cl2 ( III ). At lower temperatures and/or in the presence of PCl3, acrylonitrile reacts with PCl3 to give the cis/ trans isomers VIa and VIb . 相似文献
5.
Diazadiphosphetidines. VIII. Further Diazadiphosphetidine Oxides and an Oxide Sulfide Synthesis and properties of 1,3-dimethyl-2-phenyl-4-diethylamino-1,3,2,4-diazadiphosphetidine-2-oxide ( II ), 1,3-dimethyl-2-diethylamino-4-phenyl-1,3,2,4-diazadiphosphetidine-2-sulfide-4-oxide ( III ), and 1,3-dimethyl-2,4-diphenyl-1,3,2,4-diazadiphosphetidine-2,4-dioxide ( V ) are reported. 相似文献
6.
7.
8.
9.
Diazadiphosphetidines. VII. New Diazadiphosphetidine Oxides and Oxide Sulfides By reaction of phosphoric tris(methylamide) with tris(dimethylamino)phosphane and tris(diethylamino)phosphane, the diazadiphosphetidine oxides V and I , as well as VI and II are obtained, respectively. With elemental sulfur these compounds form the diazadiphosphetidine oxide sulfides VI and III , as well as VIII and IV , respectively. The n.m.r. spectra of the compounds II — VII are reported and discussed. 相似文献
10.
Phosphorus pentachloride reacts with BF3 · NH3 to give [Cl3P?N? PCl3][BCl4](Va). Mechanism of formation and chemical behaviour to SO2 and H2S are described, followed by a presentation and discussion of the 31P, 19F, and 11B NMR spectra of the adducts formed by P2NOCl5 and BF3, BCl3, and PF5, respectively. 相似文献