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111.
Selma Zahirović Robert Scharler Pia Kilpinen Ingwald Obernberger 《Combustion Theory and Modelling》2013,17(1):61-87
While reasonably accurate in simulating gas phase combustion in biomass grate furnaces, CFD tools based on simple turbulence–chemistry interaction models and global reaction mechanisms have been shown to lack in reliability regarding the prediction of NOx formation. Coupling detailed NOx reaction kinetics with advanced turbulence–chemistry interaction models is a promising alternative, yet computationally inefficient for engineering purposes. In the present work, a model is proposed to overcome these difficulties. The model is based on the Realizable k–? model for turbulence, Eddy Dissipation Concept for turbulence–chemistry interaction and the HK97 reaction mechanism. The assessment of the sub-models in terms of accuracy and computational effort was carried out on three laboratory-scale turbulent jet flames in comparison with the experimental data. Without taking NOx formation into account, the accuracy of turbulence modelling and turbulence–chemistry interaction modelling was systematically examined on Sandia Flame D and Sandia CO/H2/N2 Flame B to support the choice of the associated models. As revealed by the Large Eddy Simulations of the former flame, the shortcomings of turbulence modelling by the Reynolds averaged Navier–Stokes (RANS) approach considerably influence the prediction of the mixing-dominated combustion process. This reduced the sensitivity of the RANS results to the variations of turbulence–chemistry interaction models and combustion kinetics. Issues related to the NOx formation with a focus on fuel bound nitrogen sources were investigated on a NH3-doped syngas flame. The experimentally observed trend in NOx yield from NH3 was correctly reproduced by HK97, whereas the replacement of its combustion subset by that of a detailed reaction scheme led to a more accurate agreement, but at increased computational costs. Moreover, based on results of simulations with HK97, the main features of the local course of the NOx formation processes were identified by a detailed analysis of the interactions between the nitrogen chemistry and the underlying flow field. 相似文献
112.
Joyce Benzaquem Ribeiro Aline de Souza Ramos Sorele Batista Fiaux Selma Gomes Ferreira Leite Maria da Conceição Klaus V. Ramos Francisco Radler de Aquino Neto Octavio A.C. Antunes 《Tetrahedron: Asymmetry》2009,20(19):2263-2266
Microorganisms were used to reduce ethyl 4-chloroacetoacetate (CAAE) to ethyl (S)-4-chloro-3-hydroxybutanoate [(S)-CHBE]. Mucor ramannianus provided 98% conversion with 84% ee. Free cells of Kluyveromyces marxianus led to 95% conversion with 81% ee. After a fractionary factorial design to study the reaction conditions, calcium alginate immobilized cells of K. marxianus furnished the product with 99% conversion with 91% ee. 相似文献
113.
Vinylboronic Acids as Fast Reacting,Synthetically Accessible,and Stable Bioorthogonal Reactants in the Carboni–Lindsey Reaction
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M. Sc. Selma Eising B. Sc. Francis Lelivelt Dr. Kimberly M. Bonger 《Angewandte Chemie (International ed. in English)》2016,55(40):12243-12247
Bioorthogonal reactions are widely used for the chemical modification of biomolecules. The application of vinylboronic acids (VBAs) as non‐strained, synthetically accessible and water‐soluble reaction partners in a bioorthogonal inverse electron‐demand Diels–Alder (iEDDA) reaction with 3,6‐dipyridyl‐s‐tetrazines is described. Depending on the substituents, VBA derivatives give second‐order rate constants up to 27 m ?1 s?1 in aqueous environments at room temperature, which is suitable for biological labeling applications. The VBAs are shown to be biocompatible, non‐toxic, and highly stable in aqueous media and cell lysate. Furthermore, VBAs can be used orthogonally to the strain‐promoted alkyne–azide cycloaddition for protein modification, making them attractive complements to the bioorthogonal molecular toolbox. 相似文献
114.
2(3),9(10),16(17),23(24)-Tetrakis-4′-[3,5-bis-(trifluoromethyl)-phenoxy]-phthalocyanines, {M[Pc-β(OBz-(CF3)2)4]}, (M = Zn(II), Cu(II), Co(II) and Ni(II)) were synthesized and characterized by elemental analysis, FTIR, 1H NMR, UV–Vis and MS (Maldi-TOF) spectral data. It is shown that the 4-(3,5-bis(trifluoromethyl)-phenoxy) moieties on the periphery affect the solubility, spectroscopic data and electrochemistry of the tetrakis metallophthalocyanines. The cyclic voltammetry and differential pulsed voltammetry of the complexes give well-defined redox couples in harmony with common metallophthalocyanine complexes. Electrochemical studies show that the complexes exhibit stable monoanionic M{Pc-β-[(OBz-(CF3)2)4]}1−, dianionic M{Pc-β-[(OBz-(CF3)2)4]}2− and monocationic M{Pc-β-[(OBz-(CF3)2)4]}1+ species during the reduction and oxidation processes. When compared with the unsubstituted analogues, the redox potentials of the complexes shifted to more positive potentials due to the electron-withdrawing fluorine groups. 相似文献
115.
Rebersek M Corović S Sersa G Miklavcic D 《Bioelectrochemistry (Amsterdam, Netherlands)》2008,74(1):26-31
Electrochemotherapy is a treatment based on combination of chemotherapeutic drug and electroporation. It is used in clinics for treatment of solid tumours. For electrochemotherapy of larger tumours multiple needle electrodes were already suggested. We developed and tested electrode commutation circuit, which controls up to 19 electrodes independently. Each electrode can be in one of three possible states: on positive or negative potential or in the state of high impedance. In addition, we tested a pulse sequence using seven electrodes for which we also calculated electric field distribution in tumour tissue by means of finite-elements method. Electrochemotherapy, performed by multiple needle electrodes and tested pulse sequence on large subcutaneous murine tumour model resulted in tumour growth delay and 57% complete responses, thus demonstrating that the tested electrode commutation sequence is efficient. 相似文献
116.
117.
Schulz S Yildizhan S Stritzke K Estrada C Gilbert LE 《Organic & biomolecular chemistry》2007,5(21):3434-3441
The four major components present in scent gland extracts of the male Costa Rica longwing butterflies Heliconius cydno and Heliconius pachinus were identified as 12- and 14-membered macrolides containing a C(18)-carbon skeleton. By use of micro-reactions and spectrometric examinations, structural proposals were made and subsequently proven by synthesis, using ring-closing-metathesis as the key steps. These macrolides, (9Z,11E,13S)-octadeca-9,11-dien-13-olide (5, S-coriolide), (9Z,11E,13S,15Z)-octadeca-9,11,15-trien-13-olide (6), (9Z,13S)-octadec-9-en-13-olide (13), and (9Z,11S)-octadec-9-en-11-olide (25), are biosynthetically obviously derived from oleic, linoleic, and linolenic acids. Their absolute configurations were determined by gas chromatographic investigations on chiral phases, showing all to possess (S)-configuration. 相似文献
118.
Joana L. M. S. Ganter Selma F. Zawadzki-Baggio Sirlei C. S. Leitner Maria-Rita Sierakowski Fany Reicher 《Journal of carbohydrate chemistry》2013,32(6):753-767
Abstract Chemical structures of galactomannans from the native Brazilian species, M. scabrella, S. barbatiman and S. parahy-bum were studied. Their seeds, on aqueous extraction, furnished high yields of viscous galactomannans, whose mannose to galactose ratios were 1.1:1, 1.5:1, and 3.0:1, respectively. The polysaccharides were analysed by methylation, periodate oxidation and chromium trioxide oxidation. The results, confirmed by 13C NMR spectroscopy, indicated expected structures of legume galactomannans, namely a polymeric main chain of (l→4) -linked β-D-mannopyranosyl residues substituted at 0–6 by single unit α-D-galactopyranosyl side-chains. 13C NMR spectra showed clear splitting of the O-substituted resonances of C-4 of the β-D-mannosyl residues depending on the nearest-neighbour probabilities, indicating a random arrangement of the D-galactosyl groups in all of the three galactomannans. 相似文献
119.
Raquel de Oliveira Lopes Joyce Benzaquem Ribeiro Aline de Souza Ramos Leandro S.M. Miranda Ivana Corrêa Ramos Leal Selma Gomes Ferreira Leite Rodrigo Octavio Mendonça Alves de Souza 《Tetrahedron: Asymmetry》2011,22(18-19):1763-1766
Microorganisms were used to reduce 4-bromoacetophenone to (S)-4-bromophenylethanol and (R)-4-bromophenylethanol. After a fractional factorial design to identify the important variables for this reaction, Geotrichum candidum provided a 98.9% conversion with >99% ee of the (R)-isomer, while Rhodotorula rubra led to a 97.6% conversion with a 98.8% ee of the S-isomer. 相似文献
120.
Ravi P. Agarwal Selma Baghli Mouffak Benchohra 《Applied Mathematics and Optimization》2009,60(2):253-274
The controllability of mild solutions defined on the semi-infinite positive real interval for two classes of first order semilinear
functional and neutral functional differential evolution equations with infinite delay is studied in this paper. Our results
are obtained using a recent nonlinear alternative due to Avramescu for sum of compact and contraction operators in Fréchet
spaces, combined with the semigroup theory. 相似文献