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51.
Ana Lucia T. O. Nascimento Jorge A. Escobar Giuseppe Cilento 《Photochemistry and photobiology》1993,57(2):362-366
The peroxidative metabolism of the nonsteroid anti-inflammatory oxicams generates metabolites of the type expected from a dioxetane intermediae. Therefore, electronically excited metabolites may be expected. Consistent with this possibility, both direct and sensitized light emission are observed when tenoxicam is exposed to horseradish peroxidase or when added to leukocytes, where it undergoes a myeloperoxidase-catalyzed aerobic oxidation. The similarity between peroxidative metabolism with concomitant oxygen uptake and photodegrdation brought about by singlet oxygen addition to the substrate is pointed out. As a whole, the results strengthen the view that electronically excited species should also be considered when analyzing the effect(s) of xenobiotics. 相似文献
52.
Lyda La-Torre-Riveros Emely Abel-Tatis Adrián E. Méndez-Torres Donald A. Tryk Mark Prelas Carlos R. Cabrera 《Journal of nanoparticle research》2011,13(7):2997-3009
With the aim of developing dimensionally stable-supported catalysts for direct methanol fuel cell application, Pt and Pt–Ru
catalyst nanoparticles were deposited onto undoped and boron-doped diamond nanoparticles (BDDNPs) through a chemical reduction
route using sodium borohydride as a reducing agent. As-received commercial diamond nanoparticles (DNPs) were purified by refluxing
in aqueous nitric acid solution. Prompt gamma neutron activation analysis and transmission electron microscopy (TEM) techniques
were employed to characterize the as-received and purified DNPs. The purified diamond nanoparticulates, as well as the supported
Pt and Pt–Ru catalyst systems, were subjected to various physicochemical characterizations, such as scanning electron microscopy,
energy dispersive analysis, TEM, X-ray diffraction, inductively coupled plasma-mass spectrometry, X-ray photoelectron spectroscopy,
and infrared spectroscopy. Physicochemical characterization showed that the sizes of Pt and Pt–Ru particles were only a few
nanometers (2–5 nm), and they were homogeneously dispersed on the diamond surface (5–10 nm). The chemical reduction method
offers a simple route to prepare the well-dispersed Pt and Pt–Ru catalyst nanoparticulates on undoped and BDDNPs for their
possible employment as an advanced electrode material in direct methanol fuel cells. 相似文献
53.
Marcelo José Surpili Adelaide Faijoni-Alario Giuseppe Cilento 《Photochemistry and photobiology》1993,57(3):564-569
With all bacteria tested, addition of phenylacetaldehyde leads to light emission. The latter is markedly stronger with gram-negative bacteria, presumably because they possess a thinner wall and an extra external lipophilic membrane. Consistent with this explanation, the bactericidal effect of phenylacetaldehyde is also stronger with gram-negative bacteria. The spectrum of the emitted light shows maximal emission in the 500 nm region and is very similar to that observed when a protein (bovine serum albumin), free amino acids or isopropylamine reacts with phenylacetaldehyde. 相似文献
54.
Abstract –The peroxidative metabolism of TV-methylcarbazole emits light independently of the presence of oxygen. It is likely that two chemiexcited transients are formed by electron transfer to the activated peroxidase, the cation radical by one electron transfer and a cation biradical by two electron transfer consistent with the failure to observe horseradish peroxidase-II in the steady state of the reaction. In the spectral range investigated (390–700 nm) the observed emission (570–700 nm) is ascribed to the biradical, as the latter is equivalent to an excited state of the postulated iminium cation.
While lipoxygenase has no effect upon JV-methylcarbazole, it markedly enhances the emission if peroxidase is present. This effect requires oxygen and is ascribed to an excited product formed by lipoxygenase acting upon an intermediate hydroperoxide of the aerobic process promoted by peroxidase. 相似文献
While lipoxygenase has no effect upon JV-methylcarbazole, it markedly enhances the emission if peroxidase is present. This effect requires oxygen and is ascribed to an excited product formed by lipoxygenase acting upon an intermediate hydroperoxide of the aerobic process promoted by peroxidase. 相似文献
55.
Waldemar Adam Wilhelm J. Baader † Luiz H. Catalani Giuseppe Cilento Lyda Rychlá 《Photochemistry and photobiology》1985,42(5):587-589
Abstract— Excited acetone generated in the thermolysis of tetramethyldioxetane elicits the anomalous S2 → S0 fluorescence from azulene and from xanthione. In the case of azulene it could be demonstrated that (i) only the acetone singlets transfer energy to the S 2 state and (ii) the acetone triplets are quenched. These energy transfer processes are diffusion-controlled. 相似文献
56.
—Enzyme-generated triplet acetone and triplet indole-3-aldehyde transfer energy very efficiently to chloroplasts, as indicated by the intensity of the sensitized red emission that is observed. The intermediacy of excited species of oxygen (1 O2 , O2 − , HO) has been excluded. Our results open the way for investigating energy transfer in architecturally organized systems in the absence of light. 相似文献
57.
Jozef Rychlý Lyda Matisová-RychláKatarína Csomorová Ivica JanigováMichael Schilling Tom Learner 《Polymer Degradation and Stability》2011,96(9):1573-1581
The degradation of pure polymers such as polyethylene, polypropylene, polystyrene and poly(methyl methacrylate) in nitrogen and oxygen was characterized by means of non-isothermal thermogravimetry, chemiluminescence and differential scanning calorimetry. The link between the results of the different methods based on Bolland Gee scheme of polymer oxidation is described. From the set of parameters determined from the thermogravimetry, the rate constants based upon the sum of several temperature dependent first-order processes were calculated and compared with those obtained by an iso-conversional method derived for several heating rates. Competition between propagation of oxidation and depolymerisation to monomer is proposed to explain the differences in kinetic behaviour of the examined polymers. 相似文献
58.
Jozef Rychlý Lyda Matisová-Rychlá Vladimír Bukovský Martina Pleteníková Milan Vrška 《Macromolecular Symposia》2005,231(1):178-192
Lignin-containing papers from different sources and of different age were irradiated by the visible light and the progress of the degradation reaction was followed by non-isothermal chemiluminescence method. Kinetic data obtained for papers degraded in oxygen were compared with double fold endurance test and carbonyl groups concentration. The effect of lignin on degradation of cellulose after deacidification treatment of the paper by methoxymagnesium methylcarbonate (MMMC) was ascertained and a mechanism of co-oxidation of lignin and cellulose in originally alkaline conditions was outlined. 相似文献
59.
In the presence of the surfactant hexadecyltrimethyl ammonium bromide (CTAB) a cascade of electronically excited states accompanies the successive steps in the peroxidative metabolization of the strong estrogenic and tumourogenic diethylstilbestrol. Reversing the order by necessity, we report in this first paper results with the metabolites. Exposure of 4-hydroxypropiophenone, Z,Z-dienestrol or E,E-dienestrol to horseradish peroxidase and H2O2 promotes oxygen uptake and spectral alterations. Light emission is observed provided that the surfactant CTAB is present. With the three substrates, 4-hydroxybenzoic acid and a new metabolite, p-benzoquinone, have been identified. With both dienestrol isomers, 1-(4'-hydroxyphenyl)-propan-1-on-2-ol has been identified. In all cases the emission spectrum indicates the presence of several emitters. Possible chemiexcitation routes are pointed out. From the dramatic increase of the emission by enhancers, values as high as 1 x 10(-5) are inferred for the product of the quantum yields of chemiexcitation and energy transfer. 相似文献
60.
Etelvino J. H. Bechara Olga M. M. Faria Oliveira Nelson Duran ‡ Roberto Casadei de Baptista Giuseppe Cilento 《Photochemistry and photobiology》1979,30(1):101-110
Abstract— Triplet acetone generated in the isobutanal/horseradish peroxidase/O, system is quenched by collisional agents of the diene type. A Stern-Volmer analysis indicates that collision is considerably impeded, the barrier being largely entropic. Triplet-triplet energy transfer to biacetyl is also observed. Quenching of triplet acetone by energy transfer to 9 ,10-dibromoanthracene-2-sulfonate (DBAS) is a much faster process than energy transfer to these collisional agents, in accordance with the earlier inference that transfer to DBAS is a long-range triplet-singlet transfer process. The fraction of the triplet acetone which undergoes reduction to isopropanol is not interceptable by quenchers.
Absorption and circular dichroism studies suggest that peroxidase shuttles between Compound II and I when generating the precursor hydroperoxide. 相似文献
Absorption and circular dichroism studies suggest that peroxidase shuttles between Compound II and I when generating the precursor hydroperoxide. 相似文献