全文获取类型
收费全文 | 132篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
化学 | 114篇 |
晶体学 | 3篇 |
力学 | 1篇 |
数学 | 4篇 |
物理学 | 13篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2016年 | 6篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 8篇 |
2012年 | 4篇 |
2011年 | 7篇 |
2010年 | 8篇 |
2009年 | 2篇 |
2008年 | 8篇 |
2007年 | 8篇 |
2006年 | 3篇 |
2005年 | 6篇 |
2004年 | 3篇 |
2003年 | 5篇 |
2002年 | 9篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 4篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有135条查询结果,搜索用时 15 毫秒
101.
Takeshi Takemura Katsuo Uchida Masahisa Fujita Yoshio Shindo Nobumasa Suzuki Hiroaki Baba 《Chemical physics letters》1980,73(1):12-15
The phosphorescence from pyrimidine vapor has been observed by a method of time-resolved laser spectroscopy. The phosphorescence spectrum commences at 350.5 nm and consists mainly of three totally symmetric vibrations in the ground state, v6a, v12 and v9a as in the case of the zero-point vibrational level fluorescence of pyrimidine vapor. The phosphorescence quantum yield and lifetime are found to be about 1 × 10?4 and 50 μs. 相似文献
102.
Ohkata K Tamura Y Shetuni BB Takagi R Miyanaga W Kojima S Paquette LA 《Journal of the American Chemical Society》2004,126(51):16783-16792
The diastereofacial selectivity operating in Diels-Alder additions involving spirocyclic cross-conjugated cyclohexadienones with dienes of varying reactivity has been investigated. The study has included the ether series 1a-c as well as the lactone/ketone pair 2a/2b. In all cases, the preferred [4+2] cycloaddition pathway consisted of bonding from that pi-surface syn to the oxygen atom. 4-Substituted-4-methyl-2,5-cyclohexadienones (monocyclic systems) were also examined and found to undergo bond formation preferentially from the face bearing the more electron-withdrawing of the two groups at the 4 position. Kinetic parameters were determined for the cycloaddition of 1a and 2a to cyclopentadiene. The rate acceleration profile of solvents was in the order CF(3)CH(2)OH > CH(3)CN approximately CH(2)Cl(2) for the production of 9a from 1a and CF(3)CH(2)OH > CH(2)Cl(2) > CH(3)CN for the production of 21a from 2a, respectively. This spread in polarity had no major impact on product distribution, a phenomenon also reflected in the behavior of 4-substituted-4-methyl-2,5-cyclohexadienones under comparable conditions. Theoretical assessment of these experimental facts was undertaken at the HF/6-31G level. The facial selectivity is understandable in terms of the secondary interaction between the HOMO of the diene and LUMO of the dienophile as well as the effective hyperconjugation between the newly forming bond and the 4-anti-C-C sigma-orbital due to the more electron-donating bond, as defined by the Cieplak model. 相似文献
103.
A novel method which effects ring extension of the ladder oligosilsesquioxanes was developed. By applying this method, we synthesized the first functionalized tricyclic laddersiloxanes and pentacyclic laddersiloxane. The reaction of (i-PrSi(OH)O)4 with (i-PrPhClSiO)2 in pyridine gave the tetraphenyl tricyclic laddersiloxane. Following dephenylchlorination with AlCl3/HCl, and hydrolysis enabled us to isolate the tetrahydroxyl tricyclic laddersiloxane in good yield. We repeated the similar reaction from this tetrahydroxyl laddersiloxane, and the first pentacyclic laddersiloxane was obtained. The structures of the tetraphenyl and tetrahydroxyl tricyclic laddersiloxanes, and pentacyclic laddersiloxane were determined by X-ray crystallography. 相似文献
104.
feasible new preparation was reported for an octacarboxylphenyl functionalized spherosilicate, octakis[(pcarboxyphenyl) dimethylsilyl]silicate, which was a versatile monomer leading to other functional spherosilicate derivatives. The synthesis was started from octakis[dimethyl(p-methylphenyl)silyl]silicate. Octakis[dimethyl(pmethylphenyl) silyl]silicate was brominated by NBS to produce octakis[dimethyl(4-tribromomethylphenyl)silyl]silicate. Finally, octakis[dimethyl(4-tribromomethylphenyl)silyl]silicate was hydrolyzed in the presence of AgNO3 and formic acid to give the desired compound. Octakis[(pcarboxyphenyl) dimethylsilyl]silicate was fully characterized by FTIR, 1H NMR, 13C NMR, 29Si NMR spectra, ESI-MS, and elemental analysis. 相似文献
105.
A monogalactosyl monoacylglycerol 1 and two digalactosyl monoacylglycerols 2 and 3 were isolated from a cultured marine dinoflagellate Heterocapsa circularisquama along with known (2S)-1-O-6,9,12,15-octadecatetraenoyl-3-O-beta-D-galactopyranosyl]-sn-glycerol (4). On the basis of spectral analysis, the glycolipid 1 was characterised as (2S)-1-O-3,6,9,12,15-octadecapentaenoyl-3-O-beta-D-galactopyranosyl]-sn-glycerol. The glycolipids 2 and 3 were characterised as (2S)-1-O-3,6,9,12,15-octadecapentaenoyl-3-O-[alpha-D-galactopyranosyl-(1' --> 6')-O-beta-D-galactopyranosyl]-sn-glycerol and (2S)-1-O-6,9,12,15-octadecatetraenoyl-3-O-[alpha-D-galactopyranosyl-(1' --> 6')-O-beta-D-galactopyranosyl]-sn-glycerol, respectively. The isolated monoacylglycerols 1-4 showed cytolytic activity towards heart and gill cells of oyster. 相似文献
106.
Yokoi N Ueno T Unno M Matsui T Ikeda-Saito M Watanabe Y 《Chemical communications (Cambridge, England)》2008,(2):229-231
We have succeeded in improving the stability of Fe(Schiff-base).heme oxygenase (HO) hybrids by ligand design based on the crystal structure of Fe(N,N'-bis(salicylidene)-3.4-diaminobenzene propionic acid).HO. 相似文献
107.
Introduction Semiconductordeviceshavebeenwidelyusedforvariousapplicationsandbecomeindispensableforcivilizedlife style.Avarietyofchemicalsandmaterialsareusedinprocessofmanufacturingofsemiconductordevices.Atracelevelofmetallicimpu ritiesinthechemicalsan… 相似文献
108.
109.
A Baba A Mori T Yasuma S Unno H Makino T Sohda 《Chemical & pharmaceutical bulletin》1999,47(7):993-999
The syntheses and anti-inflammatory activities of novel thieno[2,3-b]pyridine and thieno[2,3-b:5,4-c']-dipyridine derivatives are described. These compounds were designed by modification of the quinoline template of a new type of disease-modifying antirheumatic drug (DMARD), TAK-603, and prepared by the Friedl?nder reaction as a key reaction. Their anti-inflammatory effects were evaluated using an adjuvant arthritis rat model. Most of the compounds which included a diethylamino moiety in the side chain had potent anti-inflammatory effect. In particular, ethyl 2-(diethylaminomethyl)-4-(3,4-dimethoxyphenyl)thieno[2,3-b:5,4-c'] dipyridine-3-carboxylate (21) exhibited more potent activity than TAK-603. 相似文献
110.