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71.
Catherine Gkioni Athanassios K. Boudalis Yiannis Sanakis Leondios Leondiadis Vassilis Psycharis Catherine P. Raptopoulou 《Polyhedron》2008
The systematic investigation of the parameter space of the CuCl2/H2mal/phen reaction system in MeOH resulted in the isolation of seven different complexes either as mixtures or in pure form, six of which have been structurally characterized. The molar ratios of the reactants and the crystallization methods have been systematically varied, leading to the isolation of compounds [Cu(H2O)(phen)(mal)] (1), [Cu(MeOH)(phen)(mal)] (2), [Cu2Li2Cl2(phen)2(mal)2(MeOH)4] (3), [Cu2(phen)4(mal)][CuCl(phen)(mal)](OH) (4), [CuCl(phen)2]Cl (5), and [CuCl(phen)(mal)][CuCl(phen)2][Cu(phen)2(Hmal)]Cl (6). The coordination versatility of the malonato ligand has been confirmed by the presence of three different coordination modes and its two deprotonation states in compounds 1–6. Solution studies on methanolic solutions of 2–4 and 6 by mass spectrometry revealed the absence of parent ion peak and the presence of fragment ions of low relative abundance not previously found in their crystal structure, thus indicating decomposition and rearrangement/reorganization of the complexes in solution and confirming the dynamic character of their solutions. Compounds 3 and 4 have been also studied in the solid state by EPR spectroscopy and magnetic measurements. 相似文献
72.
Fitilis I Fakis M Polyzos I Giannetas V Persephonis P Mikroyannidis J 《The journal of physical chemistry. A》2008,112(21):4742-4748
Two photon absorption (TPA) and photophysical properties of three new symmetrical chromophores with electron accepting phthalimide edge substituents have been studied. The three chromophores contain fluorene, alcoxy-substituted divinyl benzene, and carbazole moieties as central cores, respectively. The femtosecond time-resolved fluorescence upconversion spectroscopy and two photon excited fluorescence technique have been carried out. The effect of solvent polarity on TPA and on photophysics has also been determined. Ultrafast fluorescence dynamics, with decay times ranging from 1 to 13 ps, are revealed in polar solvents. This is attributed to the relaxation of the chromophores to the intramolecular charge transfer state. The chromophore bearing fluorene central core, being of the type A-pi-A, is the most efficient concerning TPA. Strong TPA, with a cross section value as high as 2100 GM at an excitation wavelength of 770 nm is found in acetophenone which is a solvent of intermediate polarity. The TPA spectra were also reproduced using a sum over states three-state model. A study of the TPA induced photobleaching of the fluorene molecule, doped in a solid poly(methyl-methacrylate) film, has shown that this material is very promising for efficient TPA optical data storage. 相似文献
73.
V. Metaftsis 《代数通讯》2013,41(11):3879-3886
We show that if the fundamental group of a finite graph of groups with finitely generated Abelian vertex groups is subgroup separable, then it is linear. 相似文献
74.
The concept of "capacity" in zeolite ion-exchange systems 总被引:1,自引:0,他引:1
Inglezakis VJ 《Journal of colloid and interface science》2005,281(1):68-79
In the present paper a study is conducted in order to distinguish the several types of capacity used in the literature on zeolite ion-exchange systems, to verify the use of each capacity type, and to analyze the several experimental methods used for capacity determination. Although the study is focused on zeolite clinoptilolite as a characteristic paradigm, its theoretical approaches and experimental findings and methods could also apply to other zeolites. 相似文献
75.
Vassilis N. Stathopoulos Vassiliki C. Belessi Athanasios K. Ladavos 《Reaction Kinetics and Catalysis Letters》2001,72(1):43-48
High specific surface area (ssa) perovskite type solids based on samarium (SmFe1-xAlxO3, x = 0.00, 0.50, 0.95) were prepared using hexadecyltrimethyl-ammonium bromide C16TAB as a precursor and gelating agent. The structure of perovskite is fully developed at 600oC for the SmFeO3 solid but not for the other materials. The ssa of the solids varies (33.5 m2g-1 - 1 m2g-1) depending on composition and calcination temperature. 相似文献
76.
An effective synthesis of 1-(6-hydroxyindol-1-yl)-2,2-dimethylpropan-1-one (4) was developed starting from 1H-indole (2). The key step involved suitable utilization of 4-(1-pyrrolidino)pyridine for the removal of the chloroacetyl moiety from chloroacetic acid 1-(2,2-dimethylpropionyl)-1H-indol-6-yl ester (3); a possible mechanism is, also, presented. Compound 4 might lead to selectively substituted derivatives, either on the phenolic-OH or the indolyl-NH, with putative biological interest. In this respect, we found that the core structure of 1H-indol-6-ol (1) possesses a degree of aldose reductase inhibitory potential, at a concentration of 100 microM. 相似文献
77.
Inglezakis VJ Loizidou MD Grigoropoulou HP 《Journal of colloid and interface science》2003,261(1):49-54
In the present study ion exchange of Pb(2+), Cu(2+), Fe(3+), and Cr(3+) on natural Greek clinoptilolite was examined in terms of selectivity toward the above heavy metals in single- and multicomponent solutions in batch systems. Also examined are the influence of clinoptilolite on solution acidity and the effect of acidity on the ion exchange process. Clinoptilolite increases solution acidity due to the exchange of H(+) cations with the cations initially present in its structure. H(+) cations should be considered as competitive ones in ion exchange processes, and consequently ion exchange of metals is favored at high acidity values. Cu(2+) and Cr(3+) are the most sensitive cations with respect to acidity. Selectivity determination demonstrates that the selectivity at total concentration 0.01 N and acidity 2 in both single- and multicomponent solutions is following the order Pb(2+)>Fe(3+)>Cr(3+) > or =Cu(2+). This order is set since the first days of equilibration. However, Cu(2+) shows remarkable changes in selectivity and generally its uptake and selectivity are increasing with time. On the other hand selectivity in single metal solutions where acidity is not adjusted is following the order Pb(2+)>Cr(3+)>Fe(3+) congruent with Cu(2+). 相似文献
78.
79.
We study the instability of algebraic solitons for integrable
nonlinear equations in one spatial dimension that include modified
KdV, focusing NLS, derivative NLS, and massive Thirring equations.
We develop the analysis of the Evans function that defines
eigenvalues in the corresponding Lax operators with algebraically
decaying potentials. The standard Evans function generically has
singularities in the essential spectrum, which may include embedded
eigenvalues with algebraically decaying eigenfunctions. We construct
a renormalized Evans function and study bifurcations of embedded
eigenvalues, when an algebraically decaying potential is perturbed
by a generic potential with a faster decay at infinity. We show that
the bifurcation problem for embedded eigenvalues can be reduced to
cubic or quadratic equations, depending on whether the algebraic
potential decays to zero or approaches a nonzero constant. Roots of
the bifurcation equations define eigenvalues which correspond to
nonlinear waves that are formed from unstable algebraic solitons. Our results provide precise information on the transformation
of
unstable algebraic solitons in the time-evolution problem associated
with the integrable nonlinear equation. Algebraic solitons of the
modified KdV equation are shown to transform to either travelling
solitons or time-periodic breathers, depending on the sign of the
perturbation. Algebraic solitons of the derivative NLS and massive
Thirring equations are shown to transform to travelling and rotating
solitons for either sign of the perturbation. Finally, algebraic
homoclinic orbits of the focusing NLS equation are destroyed by the
perturbation and evolve into time-periodic space-decaying solutions. 相似文献
80.
Michael A. Terzidis Julia Stephanidou-Stephanatou Aristides Terzis Vassilis Psycharis 《Tetrahedron》2008,64(51):11611-11617
Chromones were reacted with dimethyl acetonedicarboxylate in the presence of DBU in THF at room temperature to furnish good yields of products, their structure depending on the substituent at 3-position. Unsubstituted chromones lead to methyl 7-hydroxy-6-oxo-6H-benzo[c]chromone-8-carboxylates 2, whereas by using 3-bromochromone, the methyl furoate 3c along with the unexpected furylcyclopropyl-chromene carboxylate 4c was isolated. Finally, from 3-formyl-chromones functionalized benzophenones 5 were isolated, in good yields. Plausible mechanisms are proposed. 相似文献