全文获取类型
收费全文 | 111篇 |
免费 | 0篇 |
专业分类
化学 | 91篇 |
物理学 | 20篇 |
出版年
2014年 | 1篇 |
2013年 | 5篇 |
2012年 | 1篇 |
2011年 | 2篇 |
2009年 | 1篇 |
2008年 | 3篇 |
2007年 | 4篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 3篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1969年 | 2篇 |
1968年 | 1篇 |
1917年 | 1篇 |
排序方式: 共有111条查询结果,搜索用时 15 毫秒
61.
The emisssion spectra and photobehaviour were investigated for compounds of general formula COO(CH2)nC6H5 (n = 1?3) located either in small compounds. diluted in methacrylate copolymers, or incorporated as pendant units in methacrylate homopolymers. All the polymers considered show only monomeric emission. In spite of this, the singlet lifetimes of the polymers were shorter than those of small model compounds. This result shows that, even in the absence of excimer formation. the photobehaviour of a polymer can be different from that of the corresponding monomeric model compounds. The quenching rate constants when n = 2 were measured in solvents.of different thermodynamic character employing several quenchers. The results show that preferential absorption is not significant in determining the quenching rate constant but that the polymer is more sensitive to steric hindrance than the model compound. 相似文献
62.
E. A. Lissi M. V. Encina 《Journal of polymer science. Part A, Polymer chemistry》1979,17(9):2791-2803
The polymerization of methyl methacrylate and styrene photosensitized by acetone, aldehydes, ethyl pyruvate, 2,3-butanedione, and 2,3-pentanedione has been investigated and the effect of several additives (carbon tetrachloride, cumene, diethyl amine, triethyl amine, 2-pentanol, and tetrahydrofuran) on initiation efficiency has been evaluated. The initiation efficiency of a given system depends on several factors, the most important of which are the relative rates of quenching by the monomers and the additives and type of product obtained. 相似文献
63.
Link DR Clark NA Ostrovskii BI Soto Bustamante EA 《Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics》2000,61(1):R37-R40
Thin freely suspended films of a mixture of an achiral side-chain liquid crystal polymer and its monomer have been studied with depolarized reflected light microscopy. We observe that regions with an odd number of bilayers exhibit a net spontaneous polarization in the tilt plane of the molecules, while regions with an even number of bilayers have no net polarization. These odd-even effects are direct evidence that the tilted smectic bilayers are anticlinic at the polymer backbone and synclinic at bilayer interface and confirm that the phase is bilayer-by-bilayer antiferroelectric. 相似文献
64.
The emission spectra of benzyl containing itaconate polymers were investigated in dilute tetrahydrofuran solutions. The polymers studied were poly(dibenzyl itaconate), poly(monobenzyl itaconate) and a (dibenzyl itaconate-co-dicyclohexylmethyl itaconate) copolymer. The photobehaviour of small compounds bearing the same chromophores was also investigated. The results obtained allow a discussion of the effect introduced by the polymer backbone upon the process of excimer formation. 相似文献
65.
66.
The reactivity of amines towards tert-butoxy radicals depends upon the amine ionization potential and the solvent, indicating that polar structures contribute to the reactivity of these compounds. Nevertheless, the dependence with the amine potential is smaller than the one obtained for the quenching of carbonyl excited states by amines and other factors as the strength of the broken hydrogen bond and steric hindrance are also significant in determining the rate of the process. 相似文献
67.
68.
Di-tert-butyl nitroxide (DTBN) decomposes in aqueous solutions producing 2-methyl-2-nitroso propane (MNP) and tert-butanol. The process is acid catalyzed, it is of second order in DTBN, and takes place with a rate constant of (1.0 ± 0.1) M?2 s?1. The reaction is also catalyzed by the anionic surfactant sodium dodecyl sulfate and by Fe(II) and Fe(III) ions. The catalysis by Fe(III) involves a very fast reduction of Fe(III) ions with concomitant formation of 2-methyl-2-nitroso propane. The reaction catalyzed by Fe(II) also produces 2-methyl-2-nitroso propane with a formation rate given by: d[MNP]/dt = (0.25 ± 0.10) [Fe(II)] [DTBN]. This reaction rate is nearly pH independent. 相似文献
69.
Rate constants for the reactions of tert-butoxy radicals (generated by the thermal decomposition of di-tert-butylperoxyoxalate) with several sulfur containing compounds have been measured at 310 K in benzene. Hexanethiol (k = 6.5 × 107M?1s?1) reacts considerably faster than alkyl sulfides and disulfides. For these compounds the reaction rate constants are slightly dependent on the α-hydrogen type, changing (when it is expressed per hydrogen atom) only a factor 5 for sulfides and 3 for disulfides when the α-hydrogen is changed from primary (methyl) to tertiary (isopropyl). The data obtained are compared to those found for the deactivation of the benzophenone triplet. Values of ktert-butoxy/kbenzophenone range from ca 10?3 (di-tert-butyl disulfide) to 7.5 (hexanethiol). The results obtained are rationalized in terms of bond strength, steric hindrance, and charge transfer contributions to the critical configuration energies. 相似文献
70.