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81.
DIRECT DETECTION OF SINGLET OXYGEN SENSITIZED BY HAEMATOPORPHYRIN AND RELATED COMPOUNDS 总被引:1,自引:0,他引:1
J. P. Keene D. Kessel E. J. Land R. W. Redmond T. G. Truscott 《Photochemistry and photobiology》1986,43(2):117-120
Abstract— Direct time-resolved detection of the luminescence at 1270 nm from 'singlet oxygen' was used to estimate the quantum yield of singlet oxygen production (ΦΔ ) from a series of related porphyrins in benzene and in D2 O. From this and available data the fraction of oxygen quenching interactions leading to singlet oxygen production (SΔ ) was derived in most cases. A marked increase in ΦΔ value was observed for di-haematoporphyrin ester (DHE) in cetyltrimethyl ammonium bromide/D2 O solution in comparison to D2 O alone, this increase is attributed to a major structural alteration of DHE on introduction of the detergent. 相似文献
82.
R. Bonnett C. Lambert † E. J. Land + P. A. Scourides R. S. Sinclair † T. G. Truscott § 《Photochemistry and photobiology》1983,38(1):1-8
Abstract— Nanosecond laser flash photolysis and pulse radiolysis have been used to generate and characterise the triplet state, and semioxidised and semireduced radicals of haematoporphyrin, and three 0 -acyl compounds derived from it (the monoacetate, the diacetate and the disuccinate).
After 347 nm irradiation in water containing 2% Triton X-100, haematoporphyrin forms the triplet state (φT = 0.92) and photoionises monophotonically (φI = 0.03). For the O -acyl derivatives, φT approaches unity and photoionisation is reduced. In acetone the triplet yield of all four compounds are close to unity. The difference and corrected spectra for the triplet species are presented and decay rates ( k 1 ˜104 s-1 ) and oxygen quenching constants ( k Q ˜1.5times109 M -1 s-1 ) for the triplet state have been measured. The difference and corrected spectra for the semi-reduced species in methanol and semi-oxidised species in aqueous Triton X-100 are presented.
The photophysical characteristics in fluid solution of haematoporphyrin and its 0 -acyl derivatives are rather similar to those previously recorded for other photosensitising porphyrins. 相似文献
After 347 nm irradiation in water containing 2% Triton X-100, haematoporphyrin forms the triplet state (φ
The photophysical characteristics in fluid solution of haematoporphyrin and its 0 -acyl derivatives are rather similar to those previously recorded for other photosensitising porphyrins. 相似文献
83.
Abstract. The triplet-triplet absorption spectra of psoralen, xanthotoxin, angelicin and bergapten have been determined using the technique of pulse radiolysis and laser flash photolysis in benzene and water. The extinction coefficients of the triplet transitions have been measured and used to determine the singlet → triplet intersystem crossing quantum yields for 353 nm excitation. These yields vary considerably in passing from benzene to water as solvent. The highest yields were obtained for psoralen and angelicin in water, being 0.45 and 0.33, respectively. Reaction rate constants of the psoralen and angelicin triplets with various pyrimidine and purine nucleic acid bases and amino acids have been measured. The high reactivities support the suggestion that the photosensitising properties of furocou-marins are mediated by the corresponding furocoumarin triplet states. The similarly high S → T quantum yields, and triplet reactivities with pyrimidines of psoralen and angelicin, also support the suggestion that the observed differences in photosensitising properties of these two psoralens may be due to their differing geometries, which allow psoralen itself to intercalate DNA more easily than angelicin. The efficient reactions also found for psoralen and angelicin triplets with amino acids suggest that such triplets in vivo may also react with these components. Significant damage may thus be caused to protein as well as nucleic acid components of the cell. 相似文献
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Intracluster proton transfer from the matrix-assisted laser desorption/ionization matrix 2,5-dihydroxybenzoic acid (DHB) to the peptide valyl-prolyl-leucine has been investigated as a function of excitation laser wavelength and power. Ionization laser power studies at 308 nm indicate that cluster ionization occurs with a two-photon dependence, whereas matrix-to-analyte proton transfer and cluster dissociation requires an additional photon. At 266 nm, two-photon absorption leads to both cluster ionization and cluster dissociation/proton transfer. A consideration of these results clearly indicates that analyte protonation occurs following ionization of the cluster to produce a radical cation matrix/analyte cluster. Mass spectral features also indicate that mixed DHB/peptide cluster ionization can occur via two-photon ionization at wavelengths as long as 355 nm. These results suggest a reduction in the ionization potential of larger mixed DHB/peptide clusters of greater than 1 eV. The reduced ionization potential seen in these clusters suggests that radical cation initiated proton transfer remains a viable mechanism for analyte protonation in matrix-assisted laser desorption/ionization at these longer wavelengths. 相似文献
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