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131.
Mats Johnsson Karl W. Trnroos 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(5):i34-i36
Dizinc selenium dichloride trioxide, β‐Zn2(SeO3)Cl2, a monoclinic polymorph of the orthorhombic mineral sophiite, has a structure built of distorted ZnO4Cl2 octahedra, ZnO2Cl2 tetrahedra and SeO3E tetrahedra (E being the 4s2 lone pair of the SeIV ion), joined through shared edges and corners to form charge‐neutral layers. The Cl atoms and the Se lone pairs protrude from each layer towards adjacent layers. The main structural difference between the mineral and synthetic polymorphs lies in the packing of the layers. 相似文献
132.
Mats Johansson Mikael Trollss Anders Hult 《Journal of polymer science. Part A, Polymer chemistry》1992,30(10):2203-2210
A series of allyl ether-maleate functional star-shaped esters with from one to four arms has been synthesized. The structures that have been made are an analogous series with increasing molecular weight and functionality where the increase in molecular weight has been made nonlinear, i.e., star-shaped. The resins are monodisperse in the sense that each arm has a well-defined structure and that, within a certain sample, only one type of molecule exists. The viscosity and rheological behavior of the resins have been studied. The curing kinetics of the star-shaped (branched) resins and the properties of the films formed have also been studied. These properties have been related to differences in functionality and to differences in the molecular architecture of the resins. © 1992 John Wiley & Sons, Inc. 相似文献
133.
The effect of ionic strength, pH and complexing ligands on the dialysis of metal ions, particularly zinc(II), through cellulose acetate membranes, was studied under flow conditions. The dialysis factor, which depends on both the mass transfer and the membrane permeability, was found to be independence of ionic strength in the interaval 0.05–0.3 M and to increase only slightly with pH 4.6 and 7.0. Some common buffer constituents had no effect, but chloride and calcium ions affected the transfer rates. The rate of transfer of the ligands histidine, NTA and EDTA was of the same order of magnitude as that of the metal ions. The transfer rate of the Ni(II)-EDTA complex was the same as that of a mixture of Ni(II) and EDTA. Generally, addition of the chelating agents decreased the metal-ion transfer rates. Partition coefficients between the membrane polymer and the buffers were evaluated and compared with the dialysis factors and there were significant differences with regard to the range of variation, effect of concentration and pH-dependence. The time scale of uptake or release of metal ions by the polymer is much longer than that of a steady-state transfer in dialysis. Partition and dialysis may not be directly related to each other. 相似文献
134.
Copolymers based on poly(ethylene glycol) bearing one or more lipid-mimetic anchors were mixed with glycerylmonooleate (GMO)-a lipid with nonlamellar propensity-to form bulk and particulate bicontinuous cubic phases in water. The particulate phase was obtained via a liquid precursor method. Three forms of copolymer/GMO mixtures were investigated-precursor dispersions in glycerol and bulk and particulate phases in water-by visual observations, dynamic light scattering (DLS), and cryogenic transmission electron microscopy (cryo-TEM). The bulk phases were found to very slowly develop a macroscopic appearance that can be associated with the bicontinuous cubic phase. They were prepared in a slight excess of water, which became opalescent in some of the preparations. Cryo-TEM investigation of the excess showed that vesicles and particles with a dense interior coexisted. The precursors were prepared as solutions in glycerol. The viscous liquid material was investigated by DLS. Diffusion coefficients and the corresponding hydrodynamic radii, ranging from about 10 to 30 nm, were calculated. The particles are presumably of a structure similar to that of conventional emulsion droplets with GMO in the interior and copolymer molecules in the outer regions. The particulate phase in water was obtained upon hydration of the liquid precursors. The dispersions were investigated by DLS and cryo-TEM. DLS revealed the formation of nanosized particles. The size was found to increase with increasing copolymer content for copolymers with only one lipid-mimetic anchor, whereas the opposite trend was observed for the formulations with copolymers bearing more than one lipid-mimetic anchor. The shape and interior of the particles were studied by cryo-TEM. It was found that most particles were globular. For some of the compositions, particles with a dense internal structure dominated. The texture of the internal structures was assigned to dispersed bicontinuous cubic or L3 phases. In other compositions, the interior seemingly consists of arrays of interlamellar attachments. 相似文献
135.
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137.
Single crystals of nickel(II) divanadium(V) ditellurium(IV) decaoxide, NiV2Te2O10, were synthesized via a transport reaction in sealed evacuated silica tubes. The compound crystallizes in the triclinic system (space group P). The Ni atoms are positioned in the 1c position on the inversion centre, while the V and Te atoms are in general positions 2i. The crystal structure is layered, the building units within a (010) layer being distorted VO6 octahedra and NiO6 octahedra. The metal–oxide layers are connected by distorted TeO4E square pyramids (E being the 5s2 lone electron pair of TeIV) to form the framework. The structure contains corner‐sharing NiO6 octahedra, corner‐ and edge‐sharing TeO4E square pyramids, and corner‐ and edge‐sharing VO6 octahedra. NiV2Te2O10 is the first oxide containing all of the cations NiII, VV and TeIV. 相似文献
138.
Terry F. Hamilton Jussi Jernströem Roger E. Martinelli Steven R. Kehl Mats Eriksson Ross W. Williams Marek Bielewski Ariel N. Rivers Thomas A. Brown Scott J. Tumey Maria Betti 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(3):1019-1026
Runit Island on Enewetak Atoll was very heavily impacted by the U.S. nuclear testing campaign in the northern Marshall Islands (1946–58). The primary source of contamination on Runit Island was the 1958 Quince safety test where a large quantity of device plutonium (Pu) was scattered over the area near the GZ. A second low-yield device was detonated on the same site 10 days later, further disturbing the soil and leaving behind a very heterogeneous pattern of contamination including milligram-size particles of plutonium. A limited cleanup of the Fig-Quince zone was carried out in 1979. During this period, the effectiveness of the cleanup operations was primarily evaluated on the basis of bulk soil concentration data with little consideration given to the heterogeneity and long-term material-, biological-, and environmental-specific impacts of residual high activity (hot) particle contamination. The aim of the present study was twofold; (i) to characterize the levels and distribution of residual contamination in the Fig-Quince zone, and (ii) to develop pertinent data on the frequency distribution, elemental and isotopic composition, and physico-chemical properties of hot particles isolated from surface soils from Fig-Quince with a view towards providing recommendations on the future management and possible cleanup of the site. Today, Runit Island remains under an administrative quarantine. 相似文献
139.
Mats Boman 《BIT Numerical Mathematics》2006,46(2):249-260
We consider the orthogonal L2-projection P onto continuous finite element spaces. We prove estimates for P in a weighted Lp-norm and use these to prove corresponding approximation properties.
AMS subject classification (2000) 65N60, 35K85 相似文献
140.