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111.
Ramón J. Durán Ignacio de Miguel Noemí Merayo Patricia Fernández Rubén M. Lorenzo Evaristo J. Abril 《Photonic Network Communications》2009,18(3):334-344
A new multipurpose genetic algorithm, based on Pareto optimality, is proposed to design logical topologies for wavelength-routed
optical networks with the aim of minimizing both the congestion and the end-to-end delay. Simulation results show its efficiency
when compared with other previously proposed algorithms, achieving in most cases optimal or near-optimal solutions, and in
less time than other methods. Moreover, since the algorithm relies on Pareto optimality, not only does it obtain a single
logical topology but a set of them, so that the network designer can easily select the most appropriate one according to the
current network requirements. 相似文献
112.
Ignacio García Agnieszka Tercjak Nikolaos E. Zafeiropoulos Manfred Stamm Iaki Mondragon 《Macromolecular rapid communications》2007,28(24):2361-2365
Magnetic nanomaterials have been studied in order to generate novel nanocomposites that display both the magnetic properties of the nanoparticles and the ability to self‐assemble of the amorphous block copolymer matrix. Towards this goal, iron oxide magnetic nanoparticles have been modified with PS brushes by ATRP in order to improve both the dispersion and the affinity of the nanoparticles with one of the blocks of a polystyrene‐block‐polybutadiene‐block‐polystyrene block copolymer. This method of preparation of nanocomposites opens new strategies for the generation of magnetic nanomaterials. The samples are characterized using DSC and atomic and magnetic force microscopies.
113.
Grant J. Sherborne Avetik G. Gevondian Ignacio Funes-Ardoiz Amit Dahiya Christoph Fricke Prof. Dr. Franziska Schoenebeck 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(36):15673-15678
Selective C –C couplings are powerful strategies for the rapid and programmable construction of bi- or multiaryls. To this end, the next frontier of synthetic modularity will likely arise from harnessing the coupling space that is orthogonal to the powerful Pd-catalyzed coupling regime. This report details the realization of this concept and presents the fully selective arylation of aryl germanes (which are inert under Pd0/PdII catalysis) in the presence of the valuable functionalities C−BPin, C−SiMe3, C−I, C−Br, C−Cl, which in turn offer versatile opportunities for diversification. The protocol makes use of visible light activation combined with gold catalysis, which facilitates the selective coupling of C−Ge with aryl diazonium salts. Contrary to previous light-/gold-catalyzed couplings of Ar–N2+, which were specialized in Ar–N2+ scope, we present conditions to efficiently couple electron-rich, electron-poor, heterocyclic and sterically hindered aryl diazonium salts. Our computational data suggest that while electron-poor Ar–N2+ salts are readily activated by gold under blue-light irradiation, there is a competing dissociative deactivation pathway for excited electron-rich Ar–N2+, which requires an alternative photo-redox approach to enable productive couplings. 相似文献
114.
QM/MM modeling of the hydroxylation of the androstenedione substrate catalyzed by cytochrome P450 aromatase (CYP19A1) 下载免费PDF全文
Ignacio Viciano Raquel Castillo Sergio Martí 《Journal of computational chemistry》2015,36(23):1736-1747
CYP19A1 aromatase is a member of the Cytochrome P450 family of hemeproteins, and is the enzyme responsible for the final step of the androgens conversion into the corresponding estrogens, via a three‐step oxidative process. For this reason, the inhibition of this enzyme plays an important role in the treatment of hormone‐dependent breast cancer. The first catalytic subcycle, corresponding to the hydroxilation of androstenedione, has been proposed to occur through a first hydrogen abstraction and a subsequent oxygen rebound step. In present work, we have studied the mechanism of the first catalytic subcycle by means of hybrid quantum mechanics/molecular mechanics methods. The inclusion of the protein flexibility has been achieved by means of Free Energy Perturbation techniques, giving rise to a free energy of activation for the hydrogen abstraction step of 13.5 kcal/mol. The subsequent oxygen rebound step, characterized by a small free energy barrier (1.5 kcal/mol), leads to the hydroxylated products through a highly exergonic reaction. In addition, an analysis of the primary deuterium kinetic isotopic effects, calculated for the hydrogen abstraction step, reveals values (~10) overpassing the semiclassical limit for the C? H, indicating the presence of a substantial tunnel effect. Finally, a decomposition analysis of the interaction energy for the substrate and cofactor in the active site is also discussed. According to our results, the role of the enzymatic environment consists of a transition state stabilization by means of dispersive and polarization effects. © 2015 Wiley Periodicals, Inc. 相似文献
115.
Ignacio Llatser Christian Kremers Albert Cabellos-Aparicio Josep Miquel Jornet Eduard Alarcón Dmitry N. Chigrin 《Photonics and Nanostructures》2012,10(4):353-358
The scattering of terahertz radiation on a graphene-based nano-patch antenna is numerically analyzed. The extinction cross section of the nano-antenna supported by silicon and silicon dioxide substrates of different thickness are calculated. Scattering resonances in the terahertz band are identified as Fabry–Perot resonances of surface plasmon polaritons supported by the graphene film. A strong tunability of the antenna resonances via electrostatic bias is numerically demonstrated, opening perspectives to design tunable graphene-based nano-antennas. These antennas are envisaged to enable wireless communications at the nanoscale. 相似文献
116.
Marvin J. Núñez María L. Kennedy Ignacio A. JiménezIsabel L. Bazzocchi 《Tetrahedron》2011,67(17):3030-3033
Uragogin and blepharodin were isolated from Crossopetalum uragoga and Maytenus magellanica, respectively. They represent the first examples of a triterpene-neolignan ester and a heptacyclic arylpropanoid-nor-triterpenephenol, hetero-Diels-Alder adducts built with dioxane bridges. Their proposed biosynthetic route is discussed. 相似文献
117.
We have studied the magnetic and electronic properties of double perovskites A2FeReO6 with A=Ba and Ca using ab initio methods based on density functional theory. It has been shown that when changing Ba by Ca the system undergoes a metal–insulator transition coincidentally to a structural phase transition, even if conduction band fillings are not significantly changed. Our results suggest that only considering a quite large correlation term on the Re site could explain an insulating character for Ca2FeReO6. Instead, we found that small correlations could induce a bad metallic behavior as suggested in more recent experiments. 相似文献
118.
Diego Adolfo Santamaría Razo Luca Pallavidino Edoardo Garrone Francesco Geobaldo Emiliano Descrovi Angelica Chiodoni Fabrizio Giorgis 《Journal of nanoparticle research》2008,10(7):1225-1229
A sol-gel synthesis procedure based on the method proposed by Stöber et al. (J Colloid Interface Sci 26:302–315, 1968) has been adopted for the one-step preparation of mono-dispersed silica nanospheres. An excellent control of the particle diameter over a wide range is obtained by varying the amount of silicon alkoxide only, while the concentration of all other components is kept fixed: this allows the fabrication of artificial opals with a finely tuned and precisely predictable lattice parameter. 相似文献
119.
Gabriel Chuchani Ignacio Martín Alexandra Rotinov Rosa M. Domínguez 《国际化学动力学杂志》1990,22(12):1249-1255
Elimination kinetics of 2-bromohexane and 2-bromo-4-methylpentane in the gas phase were examined over the temperature range of 310–360°C and pressure range of 46–213 torr. The reactionsin seasoned, static reaction vessels, and in the presence of the free radical inhibitor cyclohexene, are homogeneous, unimolecular, and follow first order rate laws. The overall rate coefficients are described by the following Arrhenius equations: For 2-bromohexane, log??1(s?1) = (13.08 ± 0.70) ? (185.7 ± 8.2) kJ mol?1 (2.303RT)?1; for 2-bromo-4-methylpentane, log??1(s?1) = (13.08 ± 0.33) ? (183.4 ± 3.8) kJ mol?1 (2.303RT)?1. The electron releasing effect of alkyl groups influences the overall elimination rates. The olefin products isomerize in the presence of HBr gas until an equilibrium mixture is reached. 相似文献
120.
Alicia López María Ángeles Losada Ignacio Garcés Ignacio de Miguel 《Photonic Network Communications》2006,11(1):111-121
We present a novel CWDM metropolitan multiple-access ring network based on optical switching of packets according to their
wavelength. Each node within the MAN is identified by a combination of wavelength and numerical address. Hence, nodes are
able to drop packets presenting a particular wavelength and numerical address, but can insert packets in any wavelength into
the ring. This configuration allows wavelength sharing, as several nodes are identified by the same wavelength (but different
numerical addresses), and simplifies switching requirements since the set of numerical addresses is reduced. We analyze the
viability and scalability of such a network, determining the number of nodes supported by the network under different traffic
scenarios and wavelength resources. The impact of switching time on network performance is also analyzed in order to determine
which switching technology should be employed when implementing the network.
An erratum to this article is available at . 相似文献