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1.
In this Note, we present a result concerning the non existence of linear monotone schema with fixed stencil on regular meshes for some linear parabolic equation in two dimensions. The parabolic equations of interest arise from non isotropic diffusion modelling. A corollary is that no linear monotone 9 points-schemes can be designed for the one-dimensional heat equation emerged in the plane with an arbitrary direction of diffusion. Some applications of this result are provided: for the Fokker–Planck–Lorentz model for electrons in the context of plasma physics; all linear monotone scheme for the one-dimensional hyperbolic heat equation treated as a two-dimensional problem are not consistent in the diffusion limit for an arbitrary direction of propagation. We also examine the case of the Landau equation. To cite this article: C. Buet, S. Cordier, C. R. Acad. Sci. Paris, Ser. I 340 (2005). 相似文献
2.
S. Joblot Y. Cordier F. Semond S. Chenot P. Venngus O. Tottereau P. Lorenzini J. Massies 《Superlattices and Microstructures》2006,40(4-6):295
We report the realization of an AlGaN/GaN HEMT on silicon (001) substrate with noticeably better transport and electrical characteristics than previously reported. The heterostructure has been grown by molecular beam epitaxy. The 2D electron gas formed at the AlGaN/GaN interface exhibits a sheet carrier density of 8×1012 cm−2 and a Hall mobility of 1800 cm2/V s at room temperature. High electron mobility transistors with a gate length of 4 μm have been processed and DC characteristics have been achieved. A maximum drain current of more than 500 mA/mm and a transconductance gm of 120 mS/mm have been obtained. These results are promising and open the way for making efficient AlGaN/GaN HEMT devices on Si(001). 相似文献
3.
G. Lefvre A. Hamza M. Fdoroff F. Carrette H. Cordier 《Colloids and surfaces. A, Physicochemical and engineering aspects》2006,280(1-3):32-38
A simple experimental approach was developed to determine the adhesion rate of particles onto massive substrate. Turbidimetry measurements are used to follow the evolution of particle concentration in a suspension in dynamic contact with the walls of a vessel made of different materials. This method allows to rapidly obtain qualitative results about the adhesion of metallic oxides particles on massive substrates. Adhesion of particles of charged latex onto glass was used to validate the approach and was shown to be a method to determine isoelectric points (IEP) of massive substrates. Then, the adhesion of an iron oxide (hematite) particles onto several substrates was studied to determine the reactivity of current labware (glass, polypropylene) and on a metal (aluminum) commonly found in industrial fouling problems. Adhesion of hematite was found to be pH-dependant, and occurs only below ca. 6 (glass) or 7 (polypropylene), and above 7 (aluminum). DLVO calculations were performed to model the hematite/water/glass system and are consistent with the experimental results. Experiments at temperature 7–50 °C have shown an increasing of the adhesion rate from 7 to 40 °C, then a constant value until 50 °C. 相似文献
4.
On the Limits of the Zintl Concept. The New Compound Ba7Ga4Sb9 The new compound Ba7Ga4Sb9 crystallizes in the orthorhombic system, space group Pmmn (No. 59) with the lattice constants GaSb4 tetrahedra are connected by common corners and edges to strings, which are connected by long Sb? Sb bonds to sheets, separated by the Ba ions. The compound is not in accordance to the Zintl concept. 相似文献
5.
6.
A. Boughriet C. Cordier L. Deram B. Ouddane H. Chamley M. Wartel 《Fresenius' Journal of Analytical Chemistry》1995,352(3-4):341-353
A study of managanese and iron associated with particulate matter in seawaters derived from the English Channel (and North Sea). Sequential extraction procedures have been used to identify geochemical processes that govern Mn and Fe coprecipitation/accumulation/distribution in different particulate phases (carbonate; Fe-Mn(hydr)oxides; organic matter and residual phase). The oxidation states of Mn and Fe, some mechanisms of bonding and the magnetic characteristics of particles have been investigated by Mössbauer spectroscopy, electron spin resonance(ESR) spectroscopy, and mass susceptibility balance. The effect of pH and redox potential on stability of different dissolved and particulate Mn species was also examined. In the these calcareous seawaters, manganese (II) is predominantly bound to the carbonate phase (calcite) in the form of MnxCa1-xCO3. However the persistent occurrence of Mn in oxidation states > 2 in these particles has suggested the existence of manganese(III) in the polymeric FeOOH structures as an intermediate entity during Mn(II) oxidation in the sea. The activity coefficient of the entity MnOOH in FeOOH has been evaluated and p-pH diagrams of Mn have been proposed under marine conditions. 相似文献
7.
Electron Deficient Compounds of Gallium: Crystal Structure of Ca3Ga5 The stoichiometry of the formerly described compound Ca2Ga3 is corrected to Ca3Ga5. This compound crystallizes in the orthorhombic system, space group Cmcm (No. 63) with the lattice constants see ?Inhaltsübersicht”?. In the structure there is a Ga framework for which on the basis of the Gillespie/Nyholm conception and by calculating the bond numbers according to Pauling a characteristic electron concentration can be derived. 相似文献
8.
Aihara H Alston-Garnjost M Bakken JA Barbaro-Galtieri A Barnes AV Barnett BA Bengtsson H Blumenfeld BJ Bross AD Buchanan CD Chamberlain O Chien C Clark AR Cordier A Dahl OI Day CT Derby KA Eberhard PH Fancher DL Fujii H Fujii T Gabioud B Gary JW Gorn W Hadley NJ Hauptman JM Hofmann W Huth JE Hylen J Kamae T Kaye HS Kenney RW Kerth LT Koda RI Kofler RR Kwong KK Layter JG Lindsey CS Loken SC Lu X Lynch GR Madansky L Madaras RJ Maruyama K Marx JN Matthews JA Melnikoff SO Moses W Nemethy P 《Physical review letters》1985,54(4):270-273
9.
Gerhard Cordier Christoph Schwidetzky Herbert Schäfer 《Journal of solid state chemistry》1984,54(1):84-88
The new compound BaSb2S4 crystallizes in the monoclinic system (space group: , No. 14) with a = 8.985(2) Å, b = 8.203(3) Å, c = 20.602(5) Å, β = 101.36(3)°. SbS3 ψ tetrahedra and ψ-trigonal SbS4 bipyramids are connected by common corners and edgers to infinite strings. These are arraged cross-wise in sheets perpendicular to the c axis. 相似文献
10.
The syntheses, crystal structures determined by single-crystal X-ray diffraction, and characterizations of new Mo(6) cluster chalcobromides and cyano-substituted compounds with 24 valence electrons per Mo(6) cluster (VEC = 24), are presented in this work. The structures of Cs(4)Mo(6)Br(12)S(2) and Cs(4)Mo(6)Br(12)Se(2) prepared by solid state routes are based on the novel [(Mo(6)Br(i)(6)Y(i)(2))Br(a)(6)](4)(-) (Y = S, Se) discrete units in which two chalcogen and six bromine ligands randomly occupy the inner positions, while the six apical ones are fully occupied by bromine atoms. The interaction of these two compounds with aqueous KCN solution results in apical ligand exchange giving the two first Mo(6) cyano-chalcohalides: Cs(0.4)K(0.6)(Et(4)N)(11)[(Mo(6)Br(6)S(2))(CN)(6)](3).16H(2)O and Cs(0.4)K(0.6)(Et(4)N)(11)[(Mo(6)Br(6)Se(2))(CN)(6)](3).16H(2)O. Their crystal structures, built from the original [(Mo(6)Br(i)(6)Y(i)(2))(CN)(a)(6)](4)(-) discrete units, will be compared to those of the two solid state precursors and other previously reported Mo(6) cluster compounds. Their redox properties and (77)Se NMR characterizations will be presented. Crystal data: Cs(4)Mo(6)Br(12)S(2), orthorhombic, Pbca (No. 61), a = 11.511(5) A, b = 18.772(5) A, c = 28.381 A (5), Z = 8; Cs(4)Mo(6)Br(12)Se(2), Pbca (No. 61), a = 11.6237(1) A, b = 18.9447(1) A, c = 28.4874(1) A, Z = 8; Cs(0.4)K(0.6)(Et(4)N)(11)[(Mo(6)Br(6)S(2))(CN)(6)](3).16H(2)O, Pm-3m (No. 221), a = 17.1969(4) A, Z = 1; Cs(0.4)K(0.6)(Et(4)N)(11)[(Mo(6)Br(6)Se(2))(CN)(6)](3).16H(2)O, Pm-3m (No. 221), a = 17.235(5) A, Z = 1. 相似文献