全文获取类型
收费全文 | 247篇 |
免费 | 1篇 |
专业分类
化学 | 187篇 |
晶体学 | 5篇 |
数学 | 1篇 |
物理学 | 55篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 3篇 |
2015年 | 2篇 |
2014年 | 4篇 |
2013年 | 8篇 |
2012年 | 3篇 |
2011年 | 15篇 |
2010年 | 9篇 |
2009年 | 10篇 |
2008年 | 8篇 |
2007年 | 13篇 |
2006年 | 17篇 |
2005年 | 17篇 |
2004年 | 18篇 |
2003年 | 11篇 |
2002年 | 8篇 |
2001年 | 6篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 9篇 |
1996年 | 6篇 |
1995年 | 8篇 |
1994年 | 2篇 |
1993年 | 7篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1970年 | 1篇 |
1963年 | 2篇 |
排序方式: 共有248条查询结果,搜索用时 991 毫秒
171.
Volchkov V. V. Gromov S. P. Uzhinov B. M. Alfimov M. V. 《Russian Chemical Bulletin》2001,50(7):1186-1189
The protonation of some 2-quinolylthiazoles by trichloroacetic, trifluoroacetic, and sulfuric acids in the ground and excited states was studied in ethanol. The formation of the cations was found in the reaction with sulfuric acid. The formation of a mixture of cations and ionic pairs was found in the reactions with trichloroacetic and trifluoroacetic acids. The spectral-luminescence parameters of the reaction products obtained and the kinetic characteristics of the processes were determined. 相似文献
172.
M.V. Alfimov V.F. Razumov A.G. Rachinsky V.N. Listvan Yu.B. Scheck 《Chemical physics letters》1983,101(6):593-597
Absorption and fluorescence spectra of glassy solutions of some trans-stilbene-like molecules were found to differ remarkably provided trans-diarylethylenes were obtained photochemically at 77 K in situ. The phenomenon has been rationalized as being due to the production of non-equilibrium concentrations of conformers (rotamers) in view of the restrictions imposed by the solid matrix. 相似文献
173.
174.
Turshatov AA Möbius D Bossi ML Hell SW Vedernikov AI Lobova NA Gromov SP Alfimov MV Zaitsev SY 《Langmuir : the ACS journal of surfaces and colloids》2006,22(4):1571-1579
Amphiphilic 4-(3',4'-dimethoxystyryl)-N-octadecylpyridinium perchlorate and bromide form stable monolayers at the air/water interface. Small differences in the surface pressure-area and surface potential-area isotherms depending on the anion indicate interactions between the chromophore and the anions on the pure water subphase. The monolayer behavior is considerably modified on 10 mM aqueous solutions of KI, KClO4, KCl, and KF as revealed by isotherm measurements, reflection spectroscopy, and Brewster angle microscopy. The phase transition observed in the isotherms is shifted to higher surface pressure because of variation of the salt according to the Hofmeister series. Upon monolayer compression, the chromophores are increasingly tilted, and a shift of the band to longer wavelengths is attributed to the environment becoming less polar. However, in the case of KCl at small areas per molecule, relaxation is observed at constant area with the appearance of a new band shifted to shorter wavelengths. This band is assigned to small associates of about four chromophores (H aggregates). In the case of KI, a new band shifted to longer wavelengths is found. Theoretical calculations did not yield a transition in the observed range, even for large aggregates (J aggregates). Therefore, other interactions may be responsible for the appearance of this band. 相似文献
175.
L. G. Samsonova N. I. Selivanov T. N. Kopylova V. Ya. Artyukhov G. V. Maier V. G. Plotnikov V. A. Sazhnikov A. A. Khlebunov M. V. Alfimov 《High Energy Chemistry》2009,43(2):105-115
Complex (experimental and quantum-chemical) investigation of the spectral and luminescent properties of acridine, 9-aminoacridine, 2,7-dimethyl-9-ditolylaminoacridine, and their protonated forms was performed. The electronic absorption and fluorescence spectra of the acridine dyes were studied at room temperature in ethanolic solutions at different pH values and in other solvents of different chemical nature and polarity. The energies of the excited states, the deactivation rate constants for the excited states, and the dipole moments are presented, which were obtained by calculations using the method of intermediate neglect of the differential overlap with special spectroscopic parameterization. 相似文献
176.
Complexation of bis‐crown stilbene with alkali and alkaline‐earth metal cations. Ultrafast excited state dynamics of the stilbene‐viologen analogue charge transfer complex 下载免费PDF全文
Valery V. Volchkov Mikhail V. Rusalov Fedor E. Gostev Ivan V. Shelaev Viktor A. Nadtochenko Artem I. Vedernikov Asya A. Efremova Lyudmila G. Kuz'mina Sergey P. Gromov Michael V. Alfimov Mikhail Ya. Melnikov 《Journal of Physical Organic Chemistry》2018,31(2)
The complex formation of bis(18‐crown‐6)stilbene ( 1 ) and its supramolecular donor‐acceptor complex with N,N′‐bis(ammonioethyl) 1,2‐di(4‐pyridyl)ethylene derivative ( 2 ) with alkali and alkaline‐earth metal perchlorates has been studied using absorption, steady‐state fluorescence, and femtosecond transient absorption spectroscopy. The formation of 1 ?Mn+ and 1 ?(Mn+)2 complexes in acetonitrile was demonstrated. The weak long‐wavelength charge‐transfer absorption band of 1 · 2 completely vanishes upon complexation with metal cations because of disruption of the pseudocyclic structure. The spectroscopic and luminescence parameters, stability constants, and 2‐stage dissociation constants were calculated. The initial stage of a recoordination process was found in the excited complexes 1 ?M+ and 1 ?(M+)2 (M = Li, Na). The pronounced fluorescence quenching of 1 · 2 is explained by very fast back electron transfer (τet = 0.397 ps). The structure of complex 1 · 2 was studied by X‐ray diffraction; stacked ( 1 · 2 )m polymer in which the components were connected by hydrogen bonding and stacking was found in the crystal. These compounds can be considered as novel optical molecular sensors for alkali and alkaline‐earth metal cations. 相似文献
177.
Yu. S. Alaverdyan A. V. Feofanov S. P. Gromov A. I. Vedernikov N. A. Lobova M. V. Alfimov 《Optics and Spectroscopy》2004,97(4):560-566
The structure of a charge transfer complex (CTC) formed by a bis-crown-containing stilbene (1) and a dipyridylethylene derivative (2) is studied by surface-enhanced Raman scattering spectroscopy. It is found that an excess of 2 leads to the formation of a 1: 1 CTC structure ([1·2]), whereas an excess of 1 leads to the stabilization of a sandwichlike 2: 1 CTC structure ([1·2·1]). It is also revealed that 1 and diperchlorate of 1-ammoniumpropyl-4-methylpyridinium (5) form a 1: 1 CTC structure, which is much less stable. Analysis of the surface-enhanced Raman scattering data suggests that, in complete agreement with the Mulliken theory, the CTCs under study are ordinary molecular complexes in the ground state and the interaction of a molecular complex with a photon excites the former. The excitation is accompanied by a significant transfer of the electron density from the donor 1 to the acceptor 2 (5). The structural fragments of the molecules responsible for the intermolecular interaction and charge transfer are ascertained using model compounds. The charge transfer in donor-acceptor pairs occurs between the electronic systems of trisubstituted benzene and pyridine. A CTC of the [1·2] or [1·2·1] type contains two equivalent donor-acceptor pairs; however, only one of them is involved in the charge transfer. 相似文献
178.
S.O.?Konorov D.A.?Akimov A.A.?Ivanov M.V.?Alfimov A.M.?ZheltikovEmail author 《Applied physics. B, Lasers and optics》2004,78(5):565-567
Microstructure fibers are shown to allow the creation of new tunable sources for femtosecond nonlinear spectroscopy. These fibers provide a high efficiency of frequency upconversion of regeneratively amplified femtosecond pulses of a Cr:forsterite laser, permitting the generation of subpicosecond anti-Stokes pulses with a smooth temporal envelope and a linear positive chirp. These pulses from a microstructure fiber were used to measure the spectra of coherent anti-Stokes Raman scattering (CARS) of toluene solution by cross-correlating these pulses with the femtosecond second-harmonic output of the Cr:forsterite laser in boxcars geometry (XFROG CARS). PACS 42.65.Wi; 42.81.Qb 相似文献
179.
The results of studying optical and photochemical properties of organic supramolecular nanostructures capable of self-organizing due to specific intermolecular interactions are generalized in the review. The linear and nonlnear optical properties of supramolecular nanostructures of the guest—host type based on cyclodextrins, intramolecular and intermolecular complexes of crown-containing styryl dyes with metal cations, and aggregates of carbocyanine dyes are described. Photolysis reactions in supramolecular nanostructures, including photoisomerization, photocycloaddition, and formation of excimeric and charge-transfer complexes are presented. A possibility of controlling photochemical transformations in these systems by the light and cations of metal salts is shown. 相似文献
180.
Within the framework of stationary optical spectroscopy, a method for estimation of nonradiative relaxation efficiency for the electronically excited state of a fluorophore is suggested using 3,3-diethylthiacarbocyanine iodide solutions in binary mixtures of toluene and dimethyl sulfoxide (DMSO) as an example. In particular, the quantum yield of dye photoisomerization was found to noticeably decrease upon reducing DMSO content in the mixture. 相似文献