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71.
72.
Sergio Madurga Josep Lluís Garcés Encarnació Companys Carlos Rey-Castro José Salvador Josep Galceran Eudald Vilaseca Jaume Puy Francesc Mas 《Theoretical chemistry accounts》2009,123(1-2):127-135
The influence of ion size and surface charge model in titrations of ionizable polyelectrolytes is studied by means of the Semi Grand Canonical Monte Carlo simulation method in the context of the primitive model. Three models describing a discrete distribution of charged functional groups on the polyelectrolyte and different values for the radius of the background electrolyte spanning from ionic to hydrated radii values were analyzed. The polyelectrolyte titrations were simulated by calculating the degree of ionization versus pH curves at two ionic strengths. The results allow us to quantify the impact of the sizes of the background salt ions and surface functional groups of the polyelectrolyte on the dissociation degree. This influence is explained in terms of the effectiveness of the screening of the charged surface sites. Finally, by comparison with the Non-Linear Poisson–Boltzmann model, the influence of ionic correlations and finite size of the solution ions is assessed. 相似文献
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In this paper the complementary hyperstructure obtained from a multiplicative hyperring is considered. Furthermore a characterization for such hyperstructures obtained starting from a strongly distributive multiplicative hyperring is given. 相似文献
75.
Gheorghe R Kalisz M Clérac R Mathonière C Herson P Li Y Seuleiman M Lescouëzec R Lloret F Julve M 《Inorganic chemistry》2010,49(23):11045-11056
The heterometallic hexanuclear cyanide-bridged complex {[Mn(bpym)(H(2)O)](2)[Fe(HB(pz)(3))(CN)(3)](4)} (1), its C(15)N and D(2)O enriched forms {[Mn(bpym)(H(2)O)](2)[Fe(HB(pz)(3))(C(15)N)(3)](4)} (2) and {[Mn(bpym)(D(2)O)](2)[Fe(HB(pz)(3))(CN)(3)](4)} (3), and the hexanuclear derivative complex {[Mn(bpym)(H(2)O)](2)[Fe(B(pz)(4))(CN)(3)](4)}·4H(2)O (4) [bpym = 2,2'-bipyrimidine, HB(pz)(3)(-) = hydrotris(1-pyrazolyl)borate, B(pz)(4)(-) = tetra(1-pyrazolyl)borate] have been synthesized. Their structures have been determined through single-crystal X-ray crystallography at different temperatures. Whereas 3 and 4 maintain a discrete hexanuclear motif during the entire temperature range investigated (down to 95 K), 1 and 2 exhibit a thermally induced reversible single-crystal to single-crystal phase transition driven by a remarkable concerted rearrangement of hydrogen and cyanide coordination bonds. While hexanuclear complexes are observed in the high temperature phases (noted 1a and 2a) above 200 K, the low temperature phases are composed of one-dimensional coordination polymers noted 1b and 2b. The magnetic properties of the four compounds have been investigated in the 2-300 K range, and they reveal the occurrence of an overall antiferromagnetic behavior. The thermal dependence of the optical reflectivity and the FT-IR absorbance have been studied for 1 in the range 10-300 K and 130-300 K, respectively. A comparative analysis of the structural and electronic properties for 1-4 clearly underlines the major role of the intermolecular interactions in the topological and dimensional rearrangement observed during the structural phase transition. This result opens new perspectives in the design of cyanide-based switchable magnetic materials using coordination bonds rearrangements. 相似文献
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Laura Parejo Dr. Mahdi Chaari Sara Santiago Dr. Gonzalo Guirado Prof. Francesc Teixidor Dr. Rosario Núñez Dr. Jordi Hernando 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(1):270-280
Icosahedral metallacarboranes are θ-shaped anionic molecules in which two icosahedra share one vertex that is a metal center. The most remarkable of these compounds is the anionic cobalt-based metallacarborane [Co(C2B9H11)2]−, whose oxidation-reduction processes occur via an outer sphere electron process. This, along with its low density negative charge, makes [Co(C2B9H11)2]− very appealing to participate in electron-transfer processes. In this work, [Co(C2B9H11)2]− is tethered to a perylenediimide dye to produce the first examples of switchable luminescent molecules and materials based on metallacarboranes. In particular, the electronic communication of [Co(C2B9H11)2]− with the appended chromophore unit in these compounds can be regulated upon application of redox stimuli, which allows the reversible modulation of the emitted fluorescence. As such, they behave as electrochemically-controlled fluorescent molecular switches in solution, which surpass the performance of previous systems based on conjugates of perylendiimides with ferrocene. Remarkably, they can form gels by treatment with appropriate mixtures of organic solvents, which result from the self-assembly of the cobaltabisdicarbollide-perylendiimide conjugates into 1D nanostructures. The interplay between dye π-stacking and metallacarborane electronic and steric interactions ultimately governs the supramolecular arrangement in these materials, which for one of the compounds prepared allows preserving the luminescent behavior in the gel state. 相似文献
80.
Francesc Planas-Vilanova 《manuscripta mathematica》1995,87(1):349-357
For a given idealI of a commutative ringA, B=A/I, the vanishing of the second André-Quillen (co)homology functorH
2
(A, B, δ) is characterized in terms of the canonical homomorphism α:S(I)→R(I) from the symmetric algebra of the idealI onto its Rees algebra. This is done by introducing a Koszul complex that characterizes commutative graded algebras which
are symmetric algebras.
This article was processed by the author using the LATEX style filecljour1 from Springer-Verlag. 相似文献
This article was processed by the author using the LATEX style filecljour1 from Springer-Verlag. 相似文献