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871.
A method for evaluating the electromagnetic Casimir energy in situations involving spherical or circular boundaries is presented. Zeta function regularization is unambiguously used from the start and the properties of Bessel and related zeta functions are central. Nontrivial results concerning these functions are given. While part of their application agrees with previous knowledge, new results like the zeta-regularized electromagnetic Casimir energy for a circular wire are included. 相似文献
872.
Jozef Sitek Marcel Miglierini Jozef Lipka Pavol Valko Ignác Tóth 《Hyperfine Interactions》1990,60(1-4):777-779
The present work provides an analysis of crystallization processes in amorphous metallic alloys Fe80Si4Cr1.0B14 and Fe67Co18B14Si1. Crystallization of the first sample started at the temperature of 648 K. The fully crystalline state was observed after
annealing at 748 K. We identified four sextets. One corresponds to crystalline Fe2B and the three others to FeSi solid solution with 10 at .% of Si. Crystallization of Fe67Co18B14Si1 started at the temperature of 623 K. We identified two crystalline phases. The first may have its origin as (Fe1−xCox)3B, the second one may correspond to a Fe−Co solid solution with a different Co content. 相似文献
873.
Kövér KE Batta G Kowalewski J Ghalebani L Kruk D 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2004,167(2):273-281
Conventional relaxation parameters (T1(-1), T2(-1), and NOE), obtained at different temperatures and magnetic fields, are reported for the hydroxymethyl (C6) carbon in methyl-beta-D-glucopyranoside in a D2O/DMSO cryosolvent. These data are interpreted with the Lipari-Szabo model. In addition, two-field measurements of longitudinal and spin-locked relaxation rates related to the cross-correlated carbon-proton dipole-dipole interactions for the same carbon are reported. The complete data set consisting the conventional and cross-correlated relaxation parameters is interpreted using a new "hybrid" approach, in which the Lipari-Szabo model for the auto-correlated spectral densities is combined with the two-site jump model for the cross-correlated spectral densities, with the global correlation time as a common parameter. The two-site jump rates thus obtained are in reasonable agreement with the ultrasonic relaxation measurements, and have reasonable temperature dependence. 相似文献
874.
Gonda J 《Angewandte Chemie (International ed. in English)》2004,43(27):3516-3524
Among the reactions available to synthetic chemists for the construction of new C--C bonds, the Claisen rearrangement is one of the most powerful, elegant, and well-characterized methods. A genuinely new variant, the Bellus-Claisen rearrangement came to light a quarter of a century ago: The reaction of an allylic ether, thioether, or amine with a ketene leads through a [3,3] sigmatropic bond reorganization of a zwitterionic intermediate to an E unsaturated ester, thioester, or amide. When applied to cyclic allylic substrates, a ring-enlargement by four carbon atoms in one step provides medium-ring unsaturated E-configured lactones, thiolactones, and lactams. The scope of the Bellus-Claisen rearrangement and the optimum reaction conditions will be discussed in this Minireview. 相似文献
875.
Jozef Džurina 《Czechoslovak Mathematical Journal》2004,54(1):107-117
In this paper we present some new oscillatory criteria for the n-th order neutral differential equations of the form
The results obtained extend and improve a number of existing criteria. 相似文献
876.
Gorecka E Pociecha D Mieczkowski J Matraszek J Guillon D Donnio B 《Journal of the American Chemical Society》2004,126(49):15946-15947
The polycatenar bent-shaped molecules are able to form columnar phases with column stratum built of few molecules, arranged in coplanar or conelike geometry. In the latter case, the phase becomes axially polar, with electric spontaneous polarization reorientable in the electric field by flipping the cone axis. The phase is antiferroelectric; in the plane perpendicular to columns, the ferroelectric hexagonal order exists, but the columns are broken along the z direction and the polarization direction alternates between the blocks. 相似文献
877.
Antonio Breda d'Azevedo Roman Nedela Jozef Sirá n 《Transactions of the American Mathematical Society》2005,357(10):4175-4190
We give a classification of all regular maps on nonorientable surfaces with a negative odd prime Euler characteristic (equivalently, on nonorientable surfaces of genus where is an odd prime). A consequence of our classification is that there are no regular maps on nonorientable surfaces of genus where is a prime such that (mod ) and .
878.
Eva Veverková Mária Meciarová ?tefan Toma Jozef Balko 《Monatshefte für Chemie / Chemical Monthly》2003,14(6):1215-1219
Salicylanilides were prepared in 70–95% yields in 4–8min from phenyl salicylate or phenyl 4-methoxysalicylate and substituted anilines under microwave irradiation under solvent free conditions. 相似文献
879.
Moali C Anne C Lamotte-Brasseur J Groslambert S Devreese B Van Beeumen J Galleni M Frère JM 《Chemistry & biology》2003,10(4):319-329
The role of the mobile loop comprising residues 60-66 in metallo-beta-lactamases has been studied by site-directed mutagenesis, determination of kinetic parameters for six substrates and two inhibitors, pre-steady-state characterization of the interaction with chromogenic nitrocefin, and molecular modeling. The W64A mutation was performed in IMP-1 and BcII (after replacement of the BcII 60-66 peptide by that of IMP-1) and always resulted in increased K(i) and K(m) and decreased k(cat)/K(m) values, an effect reinforced by complete deletion of the loop. k(cat) values were, by contrast, much more diversely affected, indicating that the loop does not systematically favor the best relative positioning of substrate and enzyme catalytic groups. The hydrophobic nature of the ligand is also crucial to strong interactions with the loop, since imipenem was almost insensitive to loop modifications. 相似文献
880.