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111.
An improved typology of cutting and packing problems 总被引:1,自引:0,他引:1
The number of publications in the area of Cutting and Packing (C&P) has increased considerably over the last two decades. The typology of C&P problems introduced by Dyckhoff [Dyckhoff, H., 1990. A typology of cutting and packing problems. European Journal of Operational Research 44, 145–159] initially provided an excellent instrument for the organisation and categorisation of existing and new literature. However, over the years also some deficiencies of this typology became evident, which created problems in dealing with recent developments and prevented it from being accepted more generally. In this paper, the authors present an improved typology, which is partially based on Dyckhoff’s original ideas, but introduces new categorisation criteria, which define problem categories different from those of Dyckhoff. Furthermore, a new, consistent system of names is suggested for these problem categories. Finally, the practicability of the new scheme is demonstrated by using it as a basis for a categorisation of the C&P literature from the years between 1995 and 2004. 相似文献
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114.
Heike Mildenberger 《Archive for Mathematical Logic》1992,31(6):445-455
Summary The local homogeneity property is defined as in [Mak]. We show thatL
(Q1) and some related logics do not have the local homogeneity property, whereas cofinality logicL
(Q
cf) has the homogeneity property. Both proofs use forcing and absoluteness arguments. 相似文献
115.
Fliegl H Köhn A Hättig C Ahlrichs R 《Journal of the American Chemical Society》2003,125(32):9821-9827
We report accurate geometries and harmonic force fields for trans- and cis-azobenzene determined by second-order M?ller-Plesset perturbation theory. For the trans isomer, the planar structure with C(2h) symmetry, found in a recent gas electron diffraction experiment, is verified. The calculated vibrational spectra are compared with experimental data and density functional calculations. Important vibrational frequencies are localized and discussed. For both isomers, we report UV spectra calculated using the second-order approximate coupled-cluster singles-and-doubles model CC2 with accurate basis sets. Vertical excitation energies and oscillator strengths have been determined for the lowest singlet n(pi)* and (pi)(pi)* transitions. The results are compared with the available experimental data and second-order polarization propagator (SOPPA) and density functional (DFT) calculations. For both isomers, the CC2 results for the excitation energies into the S(1) and S(2) states agree within 0.1 eV with experimental gas-phase measurements. 相似文献
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Widmann A Kahlert H Petrovic-Prelevic I Wulff H Yakhmi JV Bagkar N Scholz F 《Inorganic chemistry》2002,41(22):5706-5715
Substitutional solid solutions of metal hexacyanometalates in which low-spin iron(III) and cobalt(III) ions populate the carbon-coordinated sites were synthesized and studied by powder diffraction including Rietveld refinement, cyclic voltammetry of immobilized microparticles, diffuse reflection vis-spectrometry, and magnetization techniques. The continuous solid solution series of potassium copper(II), potassium nickel(II), and iron(III) [(hexacyanoferrate(III))(1-x)(hexacyanocobaltate(III))(x)] show that the substitution of low-spin iron(III) by cobalt(III) in the hexacyanometalate units more strongly affects the formal potentials of the nitrogen-coordinated copper(II) and high-spin iron(III) ions than those of the remaining low-spin iron(III) ions. In the case of copper(II) and iron(III) [(hexacyanoferrate(III))(1-x)(hexacyanocobaltate(III))(x)] the peak currents decrease much more than can be explained by stoichiometry, indicating that the charge propagation is slowed by the substitution of low-spin iron(III) by cobalt(III). The Rietveld refinement of all compounds confirmed the structure initially proposed by Keggin for Prussian blue and contradicts the structure described later by Ludi. The dependencies of lattice parameters on composition exhibit in all series of solid solutions studied similar, although small, deviations from ideality, which correlate with the electrochemical behavior. Finally, a series of solid solutions of the composition KNi(0.5)(II)Cu(0.5)(II)[Fe(III)(CN)(6)](1-x)[Co(III)(CN)(6)](x), where both the nitrogen- and carbon-coordinated metal ions are mixed populated and were synthesized and characterized. These are the first examples of solid solutions of metal hexacyanometalates with four different metal ions, where both the nitrogen- and the carbon-coordinated sites possess a mixed population. 相似文献
118.
Über Thio-, Selenido- und Telluridogermanate (III): Zur Kenntnis von K6Ge2S6, K6Ge2Se6 und Na6Ge2Te6
On Thio-, Selenido-, and Telluridogermanates (III): K6Ge2S6, K6Ge2Se6, and Na6Ge2Te6 The new compounds K6Ge2S6 and K6Ge2Se6 crystallize in the monoclinic system, space group C2/m (No 12); lattice constants see “Inhaltsübersicht”. The compounds are isotypic and form the K6Si2Te6 structure. Na6Ge2Te6 crystallizes in the K6Sn2Te6 structure, monoclinic, space group P21/c (No 14); lattice constants see “Inhaltsübersicht”. 相似文献
119.
Conjugated β-fluoro-enamines 4 undergo cycloaddtion to methyl acrylate regio- and stereospecifically, affording the 1-fluorobicyclo[2.2.2]octan-2-one 6a after hydrolysis. 相似文献
120.
β-Alkoxy, β-dialkylamino, and β-N-alkylacylamino substituents determine the regioselectivity of the vinylic deprotonation of acrylic ester and nitrile derivatives: either α- or β-vinyllithium species may be generated. The corresponding acrylamides or systems with additional α-alkyl or α-methylmercapto substituents are lithiated at β-position. 相似文献