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Leaching tests are essential in the environmental assessment of stabilized wastes. Research programmes were conducted on their interpretation in order to develop tools for the evaluation of long term release of pollutants contained in solidified wastes. Models for the leaching of porous materials are discussed in this paper according to the specificity of the chemical species (i.e. transport model with total dissolution of species-diffusional model; transport model with progressive dissolution of species due to limitation of solubility-shrinking core model; and the model coupling transport and chemical phenomena). The leaching behaviour of pollutants (i.e. lead) solidified in a cement matrix was studied under different chemical conditions. Results have shown that the release of species whose solubilities depend on the physico-chemical conditions, and especially the pH (e.g. amphoteric metals), is governed by the solubility of the species in the pore water at local conditions and by the pH evolution within the matrix. A coupled dissolution/diffusion model was developed to describe the release of chemically complex species contained in a porous medium in contact with water. Leaching tests of cement matrices and artificial porous matrices containing calcium hydroxide and pollutants were conducted in order to validate the coupled dissolution/diffusion model. A good assessment of the retention of some pollutants contained in cement matrices could then be obtained by the association of two tests: solubilization of the pollutants related to the chemical context (pH) under steady state conditions and monolithic long term dynamic leaching tests in order to characterize the evolution of the chemical context (pH) and consequently the release of pollutants. The objective is to integrate this approach in the standardization process (CEN TC 292- WG 6, in progress). 相似文献
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Mann DL Ware GM Bonnin E Eitenmiller RR Barna E Christiansen S De Borde JL DeVries J Gilliland P Hemmer J Kalman A Konings E Levin D Salvati L Woollard D 《Journal of AOAC International》2005,88(1):30-37
A liquid chromatographic (LC) method was validated for the determination of total vitamin B6 in infant formula. Total vitamin B6 was quantified by converting the phosphorylated and free vitamers into pyridoxine. Pyridoxine was determined by ion pair reversed-phase LC with fluorescence detection. The method was subjected to an AOAC collaborative study involving a factory-manufactured, milk- and soy-based infant formula. Each was spiked at 3 concentrations in the range of 0-1 microg/g and sent as blind duplicate to participant laboratories. Nine laboratories returned valid data which were statistically analyzed for outliers and precision parameters. The repeatability relative standard deviation (RSD(r)) ranges were 2.0-4.0 and 3.5-5.9% for fortified milk- and soy-based formulas, respectively. The reproducibility relative standard deviation (RSD(R)) ranges were 8.2-8.4 and 6.7-11.2% for fortified milk- and soy-based formulas, respectively. HORRAT values ranged from 0.42 to 0.53, indicating that the precision of the method is acceptable. The mean RSD(r):RSD(R) values were 0.60 and 0.55 for milk- and soy-based formulas, respectively. As expected, RSDs for the unfortified samples were higher, but their HORRAT values (0.81 and 2.06) helped define a realistic limit of quantitation as 0.05 microg/g. Recovery data were quantitative and varied between 81.4 and 98.0% (mean = 89.8%) for each of 6 spiked materials. 相似文献
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Peter M. Barna 《合成通讯》2013,43(3):207-214
Abstract Pyrophosphoric acid was first reported as a phosphorylating agent for highmolecular weight alcohols in 19341. Direct phosphorylating of sugars and sugar derivatives was first carried out by Cherbuliez2 who used polyphosphoric acid on alcohols, amines and glycols. These precedents suggested to Seegmiller and Horecker in 19513 to try tetraphosphoric (polyphosphoric) acid, as supplied by commercs, as the phosphorylating agent of carbohydrate phosphorylation. Carbohydrates can be phosphorylated when all but one of the positions is blocked by suitable protective groups, or, on rare occasions, in the unblocked, “natural” stata.? The latter method can be used only on terminal, C5 or C6 positions as the 5-phosphates of pentoses and the 6-phosphates of hexoses are more stable at low pH than other phosphates and can withstand an acidic hydrolysis of the mixture of phosphorylated sugars resulting from such phosphorylation. For the phosphorylation of easily available, cheap pentoses and hexoses in the 5- and 6-positions respectively, with cheap polyphosphoric acid, this is the method of choice. 相似文献
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Peter M. Barna 《合成通讯》2013,43(3):215-220
In connection with the synthesis directed toward 25-hydroxycholesterol,1/ and other cholestane derivatives hydroxylated in the side chain, the research was undertaken in order to find the most effective method for the preparation of pregn-17/20/-en-21-oic acid derivatives.2/ In the present communication we would like to report the observation that contrary to the literature data, such pregnenoic acid derivatives can be conveniently obtained in very good yields by the Wittig-Horner reaction of 17-ketoandrostane derivatives and estrone with trialkyl phosphonoacetates when alcohols or DME are used as the reaction medium. In the previous reports the following statements have been made: 1/ the Wittig-Horner reaction of steroidal 17-ketones with trialkyl phosphonoacetates is compleetely inhibited as a result of the steric shielding of the carbonyl group3a, 2/ this reaction gives very low yields3b/, 3/ in the case of 17-ketoanderostane derivatives this reaction requires drastic conditions and is completely inhibited in the case of estrone/irrespective of conditions/3c/. 相似文献
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Erzsébet P. Gere Barna Bérczi Péter Simándi Gyula Wittmann András Dombi 《International journal of environmental analytical chemistry》2013,93(7):443-450
The kinetics of the reactions of H 2 O 2 and of methyl, ethyl, tert -butyl, and cumene hydroperoxides with I m were investigated in the presence and absence of molybdate as catalyst. These results were utilized to develop an analytical method for the simultaneous determination of H 2 O 2 and organic hydroperoxides in aqueous solutions. The total amount of H 2 O 2 and organic hydroperoxides can be determined by the spectrophotometric measurement of $ {\rm I}_3^ - $ formed quantitatively during 30 min of heating at 60°C. Catalase selectively decomposes H 2 O 2 in solutions containing organic hydroperoxides. The total amount of the latter can therefore be determined iodometrically after H 2 O 2 decomposition. In the oxidation of leuco crystal violet to crystal violet by H 2 O 2 and organic hydroperoxides, horseradish peroxidase exerts similar activities in the reactions involving methyl and ethyl hydroperoxides and H 2 O 2 , but its activity is much lower with tert -butyl and cumene hydroperoxide. It was observed that acetate buffer is unsuitable for pH adjustment in this type of hydroperoxide determination in consequence of the slow oxidation of the dye in the blank solution. 相似文献