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21.
Fernando Augusto Pedersen Voll Andreia Fatima Zanette Vladimir Ferreira Cabral Claudio Dariva Rodrigo Octavio Mendon?a Alves De Souza Lucio Cardozo Filho Marcos Lúcio Corazza 《Applied biochemistry and biotechnology》2012,168(5):1121-1142
This work reports the experimental data and kinetic modeling of diacylglycerol (DAG) production from palm oil using a commercial immobilized lipase (Lipozyme RM IM) in a solvent-free medium. The experiments were performed in batch mode, at 55?°C and 400?rpm, and the effects of enzyme concentration (0.68?C2.04?wt% related to the mass of substrates), initial water concentration (5?C15?wt% related to the mass of oil), and reaction time were evaluated. A novel kinetic model is presented based on the ordered-sequential bi?Cbi mechanism considering hydrolysis and esterification steps, in which a correlation between water-in-oil solubility and surfactant molecules concentration in the oil allowed the model to describe the induction period in the beginning of the hydrolysis reaction. Moreover, mass transfer limitations related to the enzyme concentration in the system were also taken into account. The proposed model presented a very satisfactory agreement with the experimental data, thus allowing a better understanding of the reaction kinetics. The best conditions obtained for the product (partially hydrolyzed palm oil) in terms of DAG yield (35.91?wt%) were 2.87?wt% enzyme/substrate, 2.10?wt% water/oil, and 72?h of reaction. 相似文献
22.
Second order rate constants and activation parameters H, S, and V have been measured for the oxidation of [Co(en)2(SOCH2CO2)]+ by S2O82– and by IO4– in highly aqueous H2O – t-BuOH mixtures. The changes in solvation on going from the initial to the transition state are discussed on the basis of the transfer functions Gto, Hto and Sto. Whereas Gt changes smoothly as the proportion of t-BuOH increases, the plots of Ht and TSt exhibit mirror behaviour and pass through extrema located around x2(t- BuOH)=0.038. Information on the role of solvation is complemented by the determination of activation volumes. These are discussed in terms of intrinsic and solvational contributions. It is proposed that changes in hydrophobic hydration are of principal importance in determining the response of H, S, and V to changes in solvent composition in H2O – t-BuOH mixtures. 相似文献
23.
Fabiane Hamerski Giovana Gonçalves Dusi Julia Trancoso Fernandes dos Santos Vítor Renan da Silva Fernando Augusto Pedersen Voll Marcos Lúcio Corazza 《国际化学动力学杂志》2020,52(8):499-512
This study reports experimental data and kinetic modeling of acetic acid esterification with n-pentanol using sulfated zirconia as a catalyst. Reactions were carried out in an isothermal well-mixed batch reactor at different temperatures (50-80°C), n-pentanol to acid molar ratios (1:1-3:1), and catalyst loadings (5-10 wt% in relation to the total amount of acetic acid). The reaction mechanism regarding the heterogeneous catalysis was evaluated considering pseudo-homogeneous, Eley–Rideal, and Langmuir–Hinshelwood model approaches. The reaction mixture was considered a nonideal solution and the UNIQUAC thermodynamic model was used to take into account the nonidealities in the liquid phase. The results obtained indicated that increases in the temperature and catalyst loading increased the product formation, while changes in the n-pentanol to acetic acid molar ratio showed no significant effect. The estimated enthalpy of the reaction was −8.49 kJ mol−1, suggesting a slightly exothermic reaction. The Eley–Rideal model, with acetic acid adsorbed on the catalyst as the limiting step, was found to be the most significant reaction mechanism. 相似文献
24.
Vollárová Ol'ga Benko Ján Aranyosiová Monika Gritzner Gerhard 《Transition Metal Chemistry》2003,28(6):722-726
Information on the solvation of thiolato complex cations [Co(en)2(SCH2COO)]+ [Co(en)2(SCH2CH(COO)NH2)]+, [Co(en)2(SCH2CH2NH2)]2+, sulfenato complexes [Co(en)2(SOCH2COO)]+ [Co(en)2{SOCH2CH(COO)NH2}]+, [Co(en)2(SOCH2CH2NH2)]2+, the sulfinato [Co(en)2{SO2CH2CH(COO)NH2}]+, [Co(en)2(SO2CH2CH2NH2)]2+ as well as of [Co(en)3]3+ has been obtained from solubility measurements in MeCN–H2O mixtures at 298.2 K. The single-ion Gibbs energies of transfer of the CoIII complexes were derived from the solubilities of picrate and perchlorate salts for the full range of MeCN–H2O mixtures. Single-ion Gibbs energies of transfer for the perchlorate ion are given. The effects of the solvent mixtures were interpreted in the framework of chemical bond formation between the ions and the individual solvent molecules. 相似文献
25.
Yingxin Xiao Ronald J. Voll Damon R. Billodeaux Frank R. Fronczek Ezzat S. Younathan 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(4):379-382
Two polymorphs of the title compound, (4R,5R,6R,7R)‐4,7‐bis(hydroxymethyl)‐1,3‐dioxepane‐5,6‐diol, C7H14O6, both have Z′ = 2 at 100 K, and differ in their hydrogen‐bonding patterns. The sodium iodide complex, NaI·C7H14O6, is isomorphous with the NaCl complex, and has the mannitol, cation and anion all lying on twofold axes. The dioxepane rings of all three molecules are in the twist‐chair conformation. 相似文献
26.
A new equipment for the collection of water percolating through the soil and bulk material constructed in 2008 was an essentially
improved variant [1]. Constructed equipment/sampler is cheap to construct on the spot, their installation does not damage
the soil layer and no vacuum was necessary for taking of water samples. From the beginning of 1994 our so called, “old equipment”
[2, 3] is still in operation in the international integrated monitoring stations of the Estonian national programme of environmental
monitoring. The new one can be used for the collection of samples of water percolating through the soil as well as heaps of
bulk materials (such as grain, fuels, construction materials) of all kinds of corner. They are necessary for monitoring the
condition of natural soil, as well as for the research of the changes in the physical state of soil during construction activities
and redesign of relief related to the establishment of ditches, ponds, artificial hills and other objects. 相似文献
27.
In this paper we compute the subgroup zeta functions of nilpotentgroups of the form , all other [,] trivial and deduce local functional equations. 2000 MathematicsSubject Classification 11M41, 20E07. 相似文献
28.
We compute explicitly the normal zeta functions of the Heisenberg groups H(R), where R is a compact discrete valuation ring of characteristic zero. These zeta functions occur as Euler factors of normal zeta functions of Heisenberg groups of the form H(OK), where OK is the ring of integers of an arbitrary number field K, at the rational primes which are non-split in K. We show that these local zeta functions satisfy functional equations upon inversion of the prime. 相似文献
29.
Paloma Souza Cabral Arion Zandoná Filho Fernando Augusto Pedersen Voll Marcos Lúcio Corazza 《Applied biochemistry and biotechnology》2014,173(6):1336-1348
This work reports experimental data, kinetic modeling, and simulations of enzyme-catalyzed hydrolysis of olive oil. This reaction was performed in batch system and an ordered-sequential Bi Bi model was used to model the kinetic mechanism. A fed-batch system was proposed and experimental data were obtained and compared to the simulated values. The kinetic model used was able to correlate the experimental data, in which a satisfactory agreement between the experimental data and modeling results was obtained under different enzyme concentration and initial free water content. Therefore, the modeling allowed a better understanding of the reaction kinetics and affords a fed-batch simulation for this system. From the results obtained, it was observed that the fed-batch approach showed to be more advantageous when compared to the conventional batch system. 相似文献
30.