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81.
Leila Moura Mark Gilmore Samantha K. Callear Tristan G. A. Youngs 《Molecular physics》2019,117(22):3364-3375
82.
M. G. Rosmaninho L. R. Souza G. M. Gomes R. F. Zica J. S. Nascimento M. C. Pereira J. D. Fabris J. D. Ardison F. C. C. Moura R. M. Lago M. H. Araujo 《Hyperfine Interactions》2010,195(1-3):49-54
Hydrogen production using ethanol and Fe2O3/support in a redox cycle was investigated. The composites were prepared by impregnation of Al2O3 and SiO2 with Fe(NO3)3, with different proportions of iron, i.e. 10, 30 and 50 wt.%, calcinated at 450°C and characterized by Mössbauer spectroscopy, XRD, SEM, BET and TG. The redox cycle to produce and/or store hydrogen is a two step process (1) initially the ethanol is used to reduce the iron oxide to Fe°; (2) and when H2 is needed, Fe° reacts with H2O to produce CO-free hydrogen, and the iron oxide is reduced again to Fe° making this system cyclic. After the reactions it was interesting to observe that ethanol can directly reduce the iron oxide to produce metallic iron, with carbon deposition and iron–carbon as side product. Preliminary results indicate that it is possible to perform multiple redox cycles with the supported iron oxide without deactivation. 相似文献
83.
Susana D. Moura Júlio S. Neves Mariusz Piotrowski 《Journal of Fourier Analysis and Applications》2009,15(6):775-795
The continuity envelope for the Besov and Triebel-Lizorkin spaces of generalized smoothness B
pq
(s,Ψ)(ℝ
n
) and F
pq
(s,Ψ)(ℝ
n
), respectively, are computed in the critical case s=n/p, provided that Ψ satisfies an appropriate critical condition. Surprisingly, in this critical situation, the corresponding optimal index is
∞, when compared with all the known results. Moreover, in the particular case of the classical spaces, we solve an open problem
posed by Haroske in Envelopes and Sharp Embeddings of Function Spaces, Research Notes in Mathematics, vol. 437, Chapman &
Hall, Boca Raton, 2007. As an immediate application of our results we give an upper estimate for approximation numbers of related embeddings. 相似文献
84.
We study finite-dimensional representations of hyper loop algebras over non-algebraically closed fields. The main results
concern the classification of the irreducible representations, the construction of the Weyl modules, base change, tensor products
of irreducible and Weyl modules, and the block decomposition of the underlying abelian category. Several results are interestingly
related to the study of irreducible representations of polynomial algebras and Galois theory. 相似文献
85.
M. G. Rosmaninho J. C. Tristão F. C. C. Moura R. M. Lago M. H. Araújo J. L. G. Fierro 《Analytical and bioanalytical chemistry》2010,396(8):2785-2795
A series of bulk and Al2O3-supported perovskite oxides of the type LaMn1???x???y Fe x Mo y O3 (x?=?0.00?0.90 and y?=?0.00–0.09) were synthesized by the citric acid complexation–gelation method followed by annealing in air at 800 °C. For all samples, the local environment and the chemical state and concentration of surface species were determined. Mössbauer spectra revealed the only presence of octahedral Fe3+ ions dispersed in the perovskite structure, however well-crystallized together with a poorly crystalline LaFeO3 phases were detected for larger substitutions (x?=?0.90). A similar picture was obtained for Mo-loaded (y?=?0.02 and 0.05) samples but a new phase most likely related to Fe3+ ions dispersed aside from the perovskite structure was found for larger substitutions (y?=?0.09). Together with these structures, supported samples showed the presence of LaFeO3 nanoparticles. Finally, photoelectron spectroscopy indicated that the chemical state and composition of the samples in the surface region (2–3 nm) approaches that of the bulk. For the unsupported substituted samples, iron (and molybdenum) enters into the perovskite structure while manganese tends to be slightly segregated. Moreover, in supported perovskites, a fraction of Mo and La atoms interact with the alumina surface. All these oxides were active in methane combustion and best performance was recorded for the Fe-rich composition (x?=?0.9) in which both Mn3+ and Mo3+ ions were in the same proportion (y?=?0.05). 相似文献
86.
Teresa Viciosa Gabriel Pires Joaquim J. Moura Ramos 《Journal of Molecular Liquids》2009,148(2-3):114-119
In the present work we revisit the previously published study by Thermally Stimulated Depolarisation Currents (TSDC) of the slow molecular mobility in the amorphous solid state of 4,4′-methylenebis(N,N-diglycidylaniline), MBDA (H. P. Diogo, J. J. Moura Ramos, J. Mol. Liq. 129(2006)138–146) in order to add two important points dealing with recent uses of the TSDC technique. One of them concerns a new method to account for nonexponentiality in Thermally Stimulated Depolarisation Currents (TSDC) data treatment which affects the analysis of the alpha relaxation peak and the determination of the fragility index of the glass-forming system. The other point concerns the analysis of the secondary relaxations in MBDA. It is shown that two kinds of secondary relaxations are differently influenced by aging. The faster components of the secondary relaxation are negligibly dependent on aging and may be ascribed to intramolecular modes of motion, while the slower motional modes show a significant dependence on aging and correspond to the genuine Johari-Goldstein β-relaxation. 相似文献
87.
Fátima Duarte Freire Cícero Flávio Soares Aragão Túlio Flávio Accioly de Lima e Moura Fernanda Nervo Raffin 《Journal of Thermal Analysis and Calorimetry》2009,97(1):333-336
Rifampicin–Isoniazid mixture is a frequently used product in the treatment of tuberculosis. Rifampicin exhibits polymorphism
and exists in two polymorphic forms: the stable form I and the metastable form II. The aim of this work was to evaluate the
thermal behavior of the binary mixtures of polymorphs I and II of rifampicin and isoniazid by using DSC. Mixtures of different
forms (rifampicin form I and II) showed interaction with isoniazid indicating that the mixtures are less stable compared to
the drug alone. Interaction was observed in case of both polymorphs of rifampicin. 相似文献
88.
A method for automatic classification of the shape of graphite particles in cast iron is proposed. In a typical supervised classification procedure, the standard charts from the ISO-945 standard are used as a training and validation population. Several shape and size parameters are described and used as discriminants. A new parameter, the average internal angle, is proposed and is shown to be relevant for accurate classification. The ideal parameter sets are determined, leading to validation success rates above 90%. The classifier is then applied to real cast iron samples and provides results that are consistent with visual examination. The method provides classification results per particle, different from the traditional per field chart comparison methods. The full procedure can run automatically without user interference. 相似文献
89.
A recently proposed model for calculating the energetics of cavity formation in liquids is used to study the interaction of rare gases in n-alkane solvents. It is observed that the energy and the entropy of interaction of a given solute with different n-alkane solvents are very similar and show a monotonic variation with the n-alkane carbon number. This behaviour, which is not observed when other methods are used to calculate the energetics of cavity formation, reinforces the idea of the similarity of the contact energies of the different n-alkane molecules. 相似文献
90.
Dey A Glaser T Moura JJ Holm RH Hedman B Hodgson KO Solomon EI 《Journal of the American Chemical Society》2004,126(51):16868-16878
Ligand K-edge XAS of an [Fe3S4]0 model complex is reported. The pre-edge can be resolved into contributions from the mu(2)S(sulfide), mu(3)S(sulfide), and S(thiolate) ligands. The average ligand-metal bond covalencies obtained from these pre-edges are further distributed between Fe(3+) and Fe(2.5+) components using DFT calculations. The bridging ligand covalency in the [Fe2S2]+ subsite of the [Fe3S4]0 cluster is found to be significantly lower than its value in a reduced [Fe2S2] cluster (38% vs 61%, respectively). This lowered bridging ligand covalency reduces the superexchange coupling parameter J relative to its value in a reduced [Fe2S2]+ site (-146 cm(-1) vs -360 cm(-1), respectively). This decrease in J, along with estimates of the double exchange parameter B and vibronic coupling parameter lambda2/k(-), leads to an S = 2 delocalized ground state in the [Fe3S4]0 cluster. The S K-edge XAS of the protein ferredoxin II (Fd II) from the D. gigas active site shows a decrease in covalency compared to the model complex, in the same oxidation state, which correlates with the number of H-bonding interactions to specific sulfur ligands present in the active site. The changes in ligand-metal bond covalencies upon redox compared with DFT calculations indicate that the redox reaction involves a two-electron change (one-electron ionization plus a spin change of a second electron) with significant electronic relaxation. The presence of the redox inactive Fe(3+) center is found to decrease the barrier of the redox process in the [Fe3S4] cluster due to its strong antiferromagnetic coupling with the redox active Fe2S2 subsite. 相似文献