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941.
Thomas X. Neenan Matthew R. Callstrom Olivier J. A. Schueller 《Macromolecular Symposia》1994,80(1):315-322
We describe the synthesis and characterization of metallopolymers comprising poly(phenylene diacetylenes) containing platinum and cobalt species coordinated to the triple bonds of the diacetylene moities. Thermal treatment of these polymers as thin films results in their conversion to hetero glassy carbon (HGC). The coordinated metals are retained within the matrices of the glassy carbons as small metallic clusters (∼10-30 Å for Pt and 50-1000 Å for cobalt). The platinum doped glassy carbon shows remarkable activity for the reduction of both H+ and O2, a result that has important implications for the development of fuel cell electrodes. At both pH 0 and 7, the platinum Pt-HGC reduced the overpotential for O2 reduction by ∼800 mV, and resulted in a voltammetric response similar to that of pure platinum. 相似文献
942.
The global response of polycrystalline aggregates is investigated, in order to simulate grain size effects in IF ferritic steels. The mechanics of generalized continua is used to describe the studied phenomena. The polycrystal is regarded as a heterogeneous Cosserat medium, and the overall properties are estimated using a specific homogenization technique. To illustrate the capabilities of the model, some simple bidimensionnal computations are presented for different grain sizes. Afterwards tridimensionnal computations are shown in order to extract the global effect on the mechanical behaviour for grain sizes ranging from 5 µm to 120 µm. The finite element response is harder for the smallest grain size, but the model still underestimate the grain size effect on the tensile response. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
943.
Andr Deluzet Olivier Guillou 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(7):m277-m279
The title compound is composed of one‐dimensional polymeric {[Er2(C12O12)(H2O)10]·4H2O}n chains containing Er in a slightly distorted antiprismatic eightfold coordination. The benzenehexacarboxylate ion is located about an inversion centre. Water molecules of crystallization, linked by hydrogen bonding to water molecules of the rare earth coordination spheres or the carboxylate groups of the organic ligands, fill the space generated by the packing of the separated chains. 相似文献
944.
945.
Olivier Musse Jean-Paul Armspach Izzie Jacques Namer Fabrice Heitz Franciszek Hennel Daniel Grucker 《Magnetic resonance imaging》1998,16(10):1227-1235
This paper presents a data-driven method for the reconstruction and visualisation of curvilinear slices from three-dimensional (3D) magnetic resonance (MR) scans of the head. Visualisation of curvilinear slices, rather than standard planar slices, produces symmetrical views of the cortex and allows small abnormalities to be detected by comparing the two hemispheres of the brain. In our method, the surface defined by the upper half of the brain is used as a reference shape for curvilinear reconstructions. The brain is first segmented from the 3D scan using a 3D region growing method associated to an unsupervised threshold selection technique. The upper half of the segmented brain is then extracted and fitted by a deformable surface model. This surface is finally interactively moved by the operator in the 3D scan, to visualise the desired curvilinear slice, which is projected on the screen as a two-dimensional image. We show an application of this visualisation technique to the localisation of cerebral epileptogenic lesions. The procedure has proven efficient and handy in clinical use. 相似文献
946.
947.
948.
We report accurate measurements of the current-phase relationship in the flow of superfluid 3He through a single orifice. While ideal sinusoidal 2π-periodic Josephson behavior prevails close to Tc, increasingly strong π-periodic admixture is usually observed at lower temperatures. 相似文献
949.
Ali Boudjada Olivier Hernandez Jean Meinnel Mohammed Mani Werner Paulus 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(9):1106-1108
In the structure of triiodomesitylene (1,3,5‐triiodo‐2,4,6‐trimethylbenzene), C9H9I3, at 293 K, the benzene ring is found to be significantly distorted from ideal D6h symmetry; the average endocyclic angles facing the I atoms and the methyl groups are 123.8 (3) and 116.2 (3)°, respectively. The angle between the normal to the molecular plane and the normal to the (100) plane is 5.1°. No disorder was detected at 293 K. The thermal motion was investigated by a rigid‐body motion tensor analysis. Intra‐ and intermolecular contacts are described and topological differences compared with the isomorphous compounds trichloromesitylene and tribromomesitylene are discussed. 相似文献
950.