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1.
V. N. Knyukshto A. M. Shul’ga E. I. Sagun É. I. Zen’kevich 《Optics and Spectroscopy》2006,101(6):895-901
Based on the study of the phosphorescence and phosphorescence excitation spectra of Pd(II) tetramethylporphyrin (PdTMP) and Pd(II) tetramethyldiethylporphyrin (PdTMDEP) in solutions in 2-methyltetrahydrofuran and dodecane in the temperature range 77–283 K, the occurrence of the splitting of the lowest degenerate singlet (S 1) and triplet (T 1, T 2) levels of porphyrin molecules is established. In the absorption of molecules of the compounds studied, two components, S 1 and S 2, are revealed in the range of allowed long-wavelength Q(0,0) transitions (530–550 nm) and four components, T 1–T 4, are observed in the range of spin-forbidden intersystem crossing transitions S 0 → T n (560–670 nm), with all the triplet levels T 1-T 4 being located below the S 1 level on the energy scale. It is shown that an increase in the degree of deformation of the porphyrin macrocycle caused by steric interactions between β alkyls and hydrogen meso atoms is accompanied by an increase in the splitting in the system of singlet levels δE(S 2–S 1) from 120 cm?1 for PdTMDEP to 215 cm?1 for PdTMP, as well as by an increase in the splitting in the system of triplet levels δE(T 2–T 1) from 190 cm?1 for PdTMDEP to 250 cm?1 for PdTMP. 相似文献
2.
3.
V. N. Knyukshto A. M. Shul’ga E. I. Sagun É. I. Zen’kevich 《Optics and Spectroscopy》2002,92(1):53-62
It is found on the basis of kinetic spectral studies in nonane, dodecane, and vitreous solutions at 77 K (phosphorescence spectra, polarized phosphorescence, decay kinetics, and phosphorescence excitation spectra) that symmetric and nonsymmetric Pd-porphyrins are characterized by the presence of two noninteracting spectrally different long-and short-wavelength forms in the ground state. The existence of the long-wavelength form is associated with the displacement of the central Pd ion from the macrocycle plane, which leads to the formation of the nonplanar “dome” conformation of the porphyrin ligand. In the case of a nonsymmetrically substituted Pd-tetramethyl-diethylporphyrin molecule, the nonplanar conformation of the π-conjugated macrocycle is characterized by the splitting of the triplet state into two components (T 1 and T 2, Δν=90 cm?1 at 77 K). Both narrow components, which have the same decay, form a dual phosphorescence of the long-wavelength form of this compound, which is caused by efficient thermal exchange between T 1 and T 2 levels in the course of deactivation to the ground state. 相似文献
4.
5.
V. N. Knyukshto E. I. Zenkevich E. I. Sagun A. M. Shulga S. M. Bachilo 《Journal of fluorescence》2000,10(1):55-68
It was found that mono- and di-meso-phenyl substitution in octaethylporphyrins (OEP)and their chemical dimers with the phenyl ring as a spacer manifests itself in the dramatical shortening of T1 state lifetimes at 295 K (from 1.5 ms down to 2–5 s in degassed toluene solutions). On the other hand, this substitution does not influence spectral-kinetic parameters of S0 and S1 states. The enhancement of the T1 state non-radiative deactivation is explained by torsional librations of the phenyl ring around a single C-C bond in sterically encumbered OEP molecules leading to non-planar dynamic distorted conformations in the excited T1 states. For these compounds with electron-accepting NO2-groups in the meso-phenyl ring the strong non-radiative deactivation of S1 and T1 states (by 2–3 orders of magnitude) is observed upon the displacement of NO2-group from para-to ortho-position of the phenyl ring. The S1 state quenching is caused by the direct intramolecular electron transfer to low-lying CT state of the radical ion pair (the normal region, non-adiabatic case presumably, V = 130–190 cm–1 in dimethylformamide). The additional deactivation of the T1 state is connected with thermally activated transitions to upper-lying CT states as well as the strengthening of intersystem crossing probabilities. 相似文献
6.
The mechanism of deactivation of the electronic excitation energy of 2-N-piperidino-5-(2′,2′-dicyanovinyl)thiophene is studied by the methods of fluorescence and quantum chemical calculations. The increase in the fluorescence quantum yield from 0.0004 in n-hexane at room temperature to 1 in an EPA mixture at 77 K is determined by an increase in the viscosity (rigidity) of the medium hindering the rotation of molecular fragments. The efficient nonradiative process in a molecule with the probability ≤2.5×1011 s?1 results mainly from rotation about the C12–C13 bond and the transition to an intermediate state with a low-lying energy level. 相似文献
7.
N. G. Kozlov S. L. Bondarev V. N. Knyukshto B. A. Odnoburtsev L. I. Basalaeva 《Russian Journal of Organic Chemistry》2010,46(11):1645-1651
The three-component condensation of 1- or 2-naphthylamines, aromatic aldehydes, and methyl 2-(benzo[1,3]dioxol-5-yl)-4,6-dioxocyclohexane-1-carboxylate
led to the formation of methyl 9-(cis,trans)-10-(1,3-benzodioxol-5-yl)-7-aryl-8-oxo-7,8,9,10,11,12-hexahydrobenzo[c]acridine-9-carboxylates or methyl 10-(cis,trans)-9-(1,3-benzodioxol-5-yl)-12-aryl-11-oxo-7,8,9,10,11,12-hexahydrobenzo[a]acridine-10-carboxylates. The spectral luminescence
properties of compounds obtained were investigated in ethanol at 293 and 77 K. 相似文献
8.
M. V. Parkhats V. A. Galievskii E. S. Zharnikova V. N. Knyukshto S. V. Lepeshkevich A. S. Stashevskii T. V. Trukhacheva B. M. Dzhagarov 《Journal of Applied Spectroscopy》2011,78(2):278-285
We have used luminescence and absorption spectroscopy to study the dynamics of photosensitized singlet oxygen generation and
the photophysical characteristics of chlorin e
6 in Photolon ointment. We have shown that dimethylsulfoxide and polyethylene glycol 400, in concentrations comparable with
their content in the ointment form of the drug Photolon, do not lead to appreciable changes in the spectral characteristics
of chlorin e
6. Substantial changes in the photophysical characteristics of the photosensitizer are observed at significantly higher concentrations
of the excipients in the ointment. We have shown that in buffer solution, chlorin e
6 forms a complex with polyethylene glycol 1500. For the first time, we have detected luminescence of singlet oxygen from the
surface of biological tissue treated with Photolon ointment. 相似文献
9.
S. A. Bagnich N. N. Khropik V. N. Knyukshto A. L. Mikhalchuk 《Journal of fluorescence》2002,12(2):249-252
This paper presents the results of the investigation of delayed luminescence of 2,3-methoxy-8-azagona-1,3,5(10),13-tetraene-12,17-dione classed with 8-azasteroids in ethanol solution at 77 K. Dual phosphorescence with maxima in the region of 400 and 500 nm, depending on the excitation wavelength, has been discovered. It is shown that the short-wavelength luminescence is due to the radiation transition from second triplet state. The possible mechanisms of emergence of dual phosphorescence in the compound investigated are considered. 相似文献
10.