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51.
Omar Kammoun Nouha Loulou Walid Rekik Houcine Na?li Tahar Mhiri Thierry Bataille 《Journal of chemical crystallography》2012,42(2):103-110
Abstract
The new hybrid material, cobalt selenate templated by 1,4-diazabicyclo[2.2.2]octane (abbreviated dabco), has been synthesised by the slow evaporation method at room temperature. Its crystal structure was investigated using single crystal X-ray diffraction data. It crystallises in the monoclinic system (space group P21/c) with the following unit-cell parameters: a = 12.9169(2) ?, b = 11.9101(2) ?, c = 12.4951(2) ?, β = 108.484(1)°, V = 1823.10(5) ?3 and Z = 4. The supramolecular structure of (C6H14N2)[Co(H2O)6](SeO4)2 consists of isolated [Co(H2O)]2+ and (C6H14N2)2+ cations and (SeO4)2− anions linked together by three dimensional hydrogen-bond network. The infrared spectroscopy confirmed the presence of these different entities. The thermal behaviour of the precursor, studied by thermodiffractometry and thermogravimetric analyses, indicates that its decomposition proceeds through three stages giving rise to the cobalt oxide. 相似文献52.
Ghazi Kassab Dominique Petit Jean-Pierre Korb Tahar Tajouri Pierre Levitz 《Comptes Rendus Chimie》2010,13(4):394-398
Reversed micelles and water in oil micro-emulsions can be used to solubilize biopolymers and genetic materials allowing analyzing their properties in a confined geometry. Nuclear Magnetic Resonance Dispersion (NMRD) provides a powerful and a noninvasive experimental technique to probe the long-term dynamics of these confined systems. However, the first step is to analyze and understand the slow dynamics of water inside these micro-reactors without any guest molecule. This is the aim of this presentation. Experimental results have been obtained for deuteron 2H NMRD of water confined in reverse micelles of bis (2-ethylhexyl) sodium sulfosuccinate (AOT) dispersed in isooctane C8H18. The water content is expressed as the molar ratio W0 = [Water]/[AOT]. The radius of the spherical reversed micelles, Rm, increases almost linearly with W0. In our case, W0 is chosen in the range 20 ≤ W0 ≤ 50 (35 ≤ Rm ≤ 80 Å). The frequency dependence for the spin-lattice relaxation rate R1(ω) exhibits two regimes, for all W0 values: a plateau at low frequency, proportional to 1/Rm, followed by the beginning of an algebraic decay. These experimental observations are discussed and compared to a numerical simulation of the intermittent Brownian diffusion of a water molecule inside a rotating reverse micelle. The possibility to probe some properties of the confinement, such as the localisation time on the sulfonated palisade and/or the water self-diffusion inside the water pool is emphasised. 相似文献
53.
Guettari Moez Ajroudi Lilia Jouini Karima Tajouri Tahar Herráez José V. 《Journal of solution chemistry》2014,43(8):1414-1420
Journal of Solution Chemistry - The aim of this work is to develop a simple theory to study the effect of the addition of an impurity on the interaction between unlike molecules in mixed liquids.... 相似文献
54.
The condensation of salicylaldehydes with various arylacetonitriles catalyzed by anion-exchange resins such as Amberlite IRA 900, leads to the corresponding 3-arylcoumarins in good yields and selectivity. 相似文献
55.
56.
Mohamed Tahar Kadaoui Abbassi Oldřich Kowalski 《Annals of Global Analysis and Geometry》2010,38(1):11-20
We prove that there is always a locally homogeneous Einstein g-natural metric on the unit tangent sphere bundle over any Riemannian space of constant positive sectional curvature. Furthermore,
using the (1–1) correspondence between all SO(m + 1)-invariant homogeneous metrics on the Stiefel manifold
V2 \mathbbRm+1 = SO(m+1)/SO(m-1){V_2 \mathbb{R}^{m+1} = {{SO}}(m+1)/{{SO}}(m-1)} and all g-natural metrics on T1 Sm{T_1 S^m} (Abbassi and Kowalski, Diff. Geom. Appl., to appear [7]), we reconstruct, by purely local procedure, the same well-known
unique SO(m + 1)-invariant homogeneous Einstein metric on
V2 \mathbbRm+1, m 1 3{V_2 \mathbb{R}^{m+1}, m \neq 3}, initially constructed by Kobayashi. 相似文献
57.
Sébastien Prévost Sébastien Gauthier Maria Cristina Caño de Andrade Céline Mordant Ali Rhida Touati Philippe Lesot Philippe Savignac Tahar Ayad Phannarath Phansavath Virginie Ratovelomanana-Vidal Jean-Pierre Genêt 《Tetrahedron: Asymmetry》2010,21(11-12):1436-1446
The dynamic kinetic resolution (DKR) of racemic α-chloro β-ketoesters and α-chloro β-ketophosphonates through ruthenium-mediated asymmetric hydrogenation is reported. The corresponding α-chloro β-hydroxyesters and α-chloro β-hydroxyphosphonates were obtained in good to high enantio- and diastereomeric excesses using, in particular, the atropisomeric ligand DIFLUORPHOS. This methodology allowed an efficient preparation of the anti phenylisoserine side chain of Taxotere® which has been used for the hemisynthesis of the cancer therapeutic agent itself. In addition, 13C NMR in chiral oriented solvents was used to investigate the DKR effect. 相似文献
58.
A single-crystal X-ray diffraction analysis has been performed on KDyP4O12 synthesized by a flux method. The new compound crystallizes at room temperature in the monoclinic space group C2/c with unit cell parameters: a=7.812(2) Å, b=12.318(3) Å, c=10.441(2) Å, β=111.09(2)°, V=937.42(4) Å3 and Dcal=3.66 g cm−3 for Z=4. A full-matrix least square refinement gave R1=0.022, wR2=0.04 for 2421 independent reflections (I>2σ(I)) refined with 84 parameters.The structure is built up from P4O124− cyclotetraphosphate anions linked by DyO8 polyhedra to form a three-dimensional framework, which delimits intersecting oxygen tunnels in which the K+ ions are located. The atomic arrangement can be described as a succession of layers extending along the [010] direction. The P4O124− ring anion is centrosymmetrical is connected by irregularly shaped KO10 polyhedra to form a layer structure parallel to (001). Dysprosium and potassium are surrounded by eight and ten oxygen atoms respectively.Samples have been examined by impedance and infrared spectroscopy techniques. The reported IR absorption investigation, recorded at room temperature in the frequency range 200-4000 cm−1, shows some bands characteristic of cyclotetraphosphates.The electrical conductivity of KDyP4O12 has subsequently been measured as a function of temperature, it represents a significant ionic conductivity and activation energy (σ=2.15×10−4 Ω−1cm−1 at 453 K and Ea=0.387 eV) corresponding to the mobility of the K+ cations located within tunnels. 相似文献
59.
Crystal structure and ionic conductivity of lithium gadolinium polyphosphate, LiGd(PO3)4, were investigated. Single crystals of the title compound have been grown by a flux technique. The structure of this novel phosphate was determined by single crystal X-ray diffraction techniques. LiGd(PO3)4 is isotypic with LiNd(PO3)4. It crystallizes in the monoclinic space group C2/c with the unit cell parameters a=16.386(2), b=7.059(3), c=9.677(2) Å, β=126.12(1)°, V=904.2(4) Å3 and Z=4. The structure refined from 967 independent reflections leads to R1=0.0167 and wR2=0.0458. The lattice of LiGd(PO3)4 is built of twisted zig-zag chains running along with the b direction and make up of PO4 tetrahedra sharing two corners, connected to the GdO8 and LiO4 polyhedra by common oxygen atoms to form a three-dimensional framework. Differential and thermogravimetric thermal analysis are given. The thermal curve of this compound was recorded and interpreted in agreement with impedance measurements. The ionic conductivity has been measured on pellet of the polycrystalline powder and evaluated as a function of temperature. This phase showed the conductivity of 2×10−6 and 2×10−4 Ω−1 cm−1 at 682 and 951 K, respectively. 相似文献
60.
A new organically templated metal sulfate has been synthesized and characterized. At room temperature, dabcodiium hexaaquacopper(II) bis(sulfate), (C6H14N2)[Cu(H2O)6](SO4)2 crystallizes in the monoclinic symmetry (space group P21/n) with the following unit cell parameters: a = 6.9533(2), b = 12.5568(2), c = 9.9434(2) Å; β = 90.526(1)° and Z = 2. Its crystal structure is built from isolated [Cu(H2O)6]2+, and disordered ions linked together by a hydrogen-bonding network. The title compound undergoes a reversible phase transition of the first-order type at 265.7/281.8 K on heating–cooling runs. Below the phase transition temperature, the structure is fully ordered. 相似文献