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991.
Jinyoung Kim Docheon Ahn Chandramouli Kulshreshtha Kee‐Sun Sohn Namsoo Shin 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(4):i14-i16
The structure of lithium barium silicate, Li2BaSiO4, has been determined from synchrotron radiation powder data. The title compound was synthesized by high‐temperature solid‐state reaction and crystallizes in the hexagonal space group P63cm. It contains two Li atoms, one Ba atom (both site symmetry ..m on special position 6c), two Si atoms [on special positions 4b (site symmetry 3..) and 2a (site symmetry 3.m)] and four O atoms (one on general position 12d, and three on special positions 6c, 4b and 2a). The basic units of the structure are (Li6SiO13)5− units, each comprising seven tetrahedra sharing edges and vertices. These basic units are connected by sharing corners parallel to [001] and through sharing (SiO4)4− tetrahedra in (001). The relationship between the structures and luminescence properties of Li2SrSiO4, Li2CaSiO4 and the title compound is discussed. 相似文献
992.
993.
In this paper we construct circumscribed Hermitian ellipsoids of Hartogs domains of least volume and as an application, we obtain the Carath′eodory extremal mappings between the Hartogs domains and the unit ball, and also give an explicit formula for calculating the extremal values. 相似文献
994.
Thermally reversible pluronic/heparin nanocapsules exhibiting 1000-fold volume transition 总被引:3,自引:0,他引:3
Choi SH Lee JH Choi SM Park TG 《Langmuir : the ACS journal of surfaces and colloids》2006,22(4):1758-1762
Novel Pluronic/heparin composite nanocapsules that exhibit a thermally responsible swelling and deswelling behavior were synthesized. Pluronic F-127 preactivated with p-nitrophenyl chloroformate at its two terminal hydroxyl groups was dissolved in a methylene chloride phase. The organic phase was dispersed in an aqueous phase containing heparin. At an organic/aqueous interface, Pluronic-cross-linked heparin nanocapsules were produced. They exhibited a 1000-fold volume transition (ca. 336 nm at 25 degrees C; ca. 32 nm at 37 degrees C), and a reversible swelling and deswelling behavior when the temperature was cycled between 20 and 37 degrees C. The reversible volume transition of Pluronic nanocapsules was caused by micellization and demicellization of cross-linked Pluronic polymer chains within the nanocapsule structure in response to temperature. The morphological characters were investigated with transmission electron microscopy and small angle neutron scattering. Pluronic/heparin nanocapsules had an aqueous fluid-filled hollow interior with a surrounding shell layer below the critical temperature, but they became a collapsed core/shell structure similar to that of Pluronic micelles above it. 相似文献
995.
Bae KH Choi SH Park SY Lee Y Park TG 《Langmuir : the ACS journal of surfaces and colloids》2006,22(14):6380-6384
Gold nanoparticles were employed to prepare shell cross-linked Pluronic micelles that exhibit a reversibly thermosensitive swelling/shrinking behavior. Two terminal hydroxyl groups of Pluronic F127 were thiol-functionalized to form self-assembling Pluronic micelles in aqueous solution with exposed -SH groups in an outer shell layer. The thiol groups present in the outer shell were cross-linked by gold nanoparticles synthesized through NaBH4 reduction of gold precursor anions. The resultant shell cross-linked gold-Pluronic micelles exhibited a temperature-dependent volume transition: their hydrodynamic diameter was changed from 157.1 +/- 15.6 nm at 15 degrees C to 53.4 +/- 5.5 nm at 37 degrees C as determined by dynamic light scattering. The critical micelle temperature measured by a pyrene solubilization technique suggested that the reversible swelling/shrinking behavior of the micelles was caused by hydrophobic interactions of cross-linked or grafted Pluronic copolymer chains in the micelle structure with increasing temperature. Transmission electron microscopy directly revealed that the shell cross-linked micelles were indeed produced by gold nanoparticles covalently clustered on the surface. These novel self-assembled organic/inorganic hybrid micelles would hold great potential for diagnostic and therapeutic applications. 相似文献
996.
The (1)H and (13)C NMR spectra of dicondensed indolinobenzospiropyrans as precursors of thermo- and photochromic spiropyrans, DC1-DC5, were completely assigned. Especially, the (1)H assignment and coupling characteristics of the diastereotopic protons at the carbon-3 position of the benzopyran rings were achieved by conducting (1)H-(1)H COSY and nOe experiments. The dihedral angles (theta(1), theta(2) and theta(3)) calculated from the experimental values of the vicinal coupling constants ((3)J) of DC5 are in good agreement with the observed values in the solid state. All of the carbons in the DC dye molecules were investigated through a combination of heteronuclear 2D-shift correlation spectroscopy (HETCOR) and DEPT135. 相似文献
997.
Six flavone derivatives were studied. Previously reported NMR data of three of these derivatives were corrected and the NMR data for the other three derivatives not studied previously were completely assigned on the basis of the basic 1D and 2D NMR experiments and molecular modeling. 相似文献
998.
The relationship between the kinetics of the lipase-catalyzed oil hydrolysis and the surface area distribution of oil droplets was investigated using ethyl decanoate and gum Arabic (GA) as a model oil and an emulsifier, respectively. Along an ethyl decanoate concentration gradient between 2 and 8 mM, the initial hydrolysis rate increased at 0.25% (w/v) GA but did not change at 1.0% (w/v) GA. At 0.25% GA, the surface area of droplets was narrowly distributed regardless of the ethyl decanoate concentration. However, at 1.0% GA and with ethyl decanoate concentrations higher than 2 mM, the fraction of relatively large droplets with a surface area larger than approximately 200 microm2, suddenly increased. The microscopy of ethyl decanoate emulsion during the hydrolysis reaction indicates that the large oil droplets were not hydrolyzed. At 20 mM ethyl decanoate where the hydrolysis rate remained the same between 0.25% and 1.0% GA, the surface area of droplets was narrowly distributed at 0.25% and 1.0% GA. Therefore, the constant hydrolysis rate observed in the emulsion of ethyl decanoate between 2 and 8 mM containing GA at 1.0%, is believed to be caused by the relatively large oil droplets with the interface quality differing from that of the small oil droplets. 相似文献
999.
Cong X Czerwieniec G McJimpsey E Ahn S Troy FA Lebrilla CB 《Journal of the American Society for Mass Spectrometry》2006,17(3):442-452
Gas-phase zwitterionic amino acids were formed in complexes of underivatized beta-cyclodextrin through reactions with a neutral base, n-propylamine. The reaction was performed in the analyzer cell of an electrospray ionization-Fourier transform mass spectrometer. Most of the natural amino acids were studied with three cyclodextrin hosts including alpha-, beta-, and gamma-cyclodextrin to understand better the structural features that lead to the stabilization of the zwitterionic complexes. Molecular dynamics calculations were performed to provide insight into the structural features of the complexes. The rate constants of the reactions were obtained through kinetic plots. Examination of both L- and D-enantiomers of the amino acid showed that the reaction was enantioselective. The reaction was then employed to analyze mixtures of Glu enantiomers naturally occurring in the bacteria Bacillus licheniformis. 相似文献
1000.