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101.
Alfonso M. Liquori Giuseppe Anzuino Maria D'Alagni Vincenzo Vitagliano Lucia Costantino 《Journal of Polymer Science.Polymer Physics》1968,6(3):509-516
Acid hydrolysis of a stereoblock poly(methyl methacrylate) sample leads to a mixture of isotactic and syndiotactic poly(methacrylic acid) which can be separated by electrophoresis. The experiment confirms the stereochemical identity between the so-called “stereoblock” poly(methyl methacrylate) and the stereocomplex which syndiotactic and isotactic poly(methyl methacrylate) form in the ratio 2:1. A possible mechanism of replica polymerization is suggested to account for this effect. 相似文献
102.
Giovanni Marletta Orazio Puglisi Salvatore Pignataro Giulio Alberti Umberto Costantino 《Polyhedron》1983,2(3):157-162
The valence bands (V.B.) of ESCA spectra of Zr(IV) and Ti(IV) acid phosphates in different crystalline phases are reported. The various bands are assigned by comparison with Li3PO4. Variations on changing the crystalline phase for compounds having the same M(IV) ion are found. Two types of molecular orbitals are mainly involved. One related to PO bonds is affected by the crystalline phase. The other, related to M(IV)O bonds and confined into the layers of the compounds, are less sensitive to crystalline environment. Variation in the symmetry of the tetrahedral type PO3?4 anion are proposed to be mainly responsible of the observed effects. 相似文献
103.
Riccardo Vivani Ferdinando Costantino Giacomo D. Gatta 《Journal of solid state chemistry》2004,177(11):4013-4022
A new layered zirconium diphosphonate fluoride, ZrF(O3PCH2)2NHCH2C6H5 has been prepared and its structure determined ab initio by X-ray powder data and refined with the Rietveld method (orthorhombic, , , , space group Pbca, , Z=8, Rwp=0.080). Both phosphonic groups of each diphosphonate building block are bonded to zirconium atoms on the same side of each layer. Benzyl groups from adjacent layers are interdigitated in the interlayer region, with probable π-π stacking interactions. The structure of the free benzylamino-N,N-bis methylphosphonic acid has been determined by single crystal X-ray data (monoclinic, space group P21, , , , β=92.930(3)°, , Z=2, R1=0.072, wR2=0.150). As in the zirconium derivative, benzyl groups from adjacent layers are interdigitated and create a regular alternation of polar and non-polar regions. 相似文献
104.
R. Sartorio V. Vitagliano L. Costantino O. Ortona 《Journal of solution chemistry》1982,11(12):875-888
Diffusion coefficients have been measured for the binary systems sodium polyacrylate-water and polyacrylic acid-water at 25°C as a function of concentration. Diffusion coefficients have been also measured for the ternary system sodium chloride-sodium polyacrylate-water at constant NaCl concentration and varying polyacrylate concentration. The experimental results have been compared with some limit expressions, available in literature, for the four D
ik
diffusion coefficients of systems containing two electrolytes with a common ion. The ternary system shows strong interaction between flows: as the polyelectrolyte concentration, C2, approaches zero, the main diffusion coefficient D22 and the cross coefficient D21 approach zero, while the cross coefficient D12 reach quite high values. The water motion during the diffusion process is also discussed. 相似文献
105.
Unai Arregui Leon Luca Carletti Davide Rocco Costantino De Angelis Giuseppe Della Valle 《Laser \u0026amp; Photonics Reviews》2024,18(2):2300669
Optical rectification (OR) at the nanoscale has attracted an increasing interest in the prospect of providing efficient ultracompact terahertz (THz) sources. Here, a universal modeling approach capable of addressing both isotropic and anisotropic all-dielectric nonlinear nanomaterials on an ultra-broad spectral range, covering the highly dispersive phonon-polariton window, and different orientations of the crystallographic axes with respect to the geometry of the structure is reported. This analysis is exemplified by considering two study cases, that is, nanopillars of AlGaAs and of LiNbO3. A close comparison between the two cases is established in terms of THz generation efficiency from 4 to 14 THz. Phonon-polariton contributions to the OR process are disentangled from the electronic one, and a model order reduction based on the reciprocity theorem is applied and validated on both the considered configurations. These results, combined with the inspection of the THz near-field features, pave the way to the design and optimization of nonlinear metasurfaces for THz generation and detection at the nanoscale. 相似文献
106.
Water‐Mediated Proton Conduction in a Robust Triazolyl Phosphonate Metal–Organic Framework with Hydrophilic Nanochannels
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Salma Begum Zhaoyang Wang Dr. Anna Donnadio Prof. Dr. Ferdinando Costantino Prof. Dr. Mario Casciola Dr. Rustem Valiullin Dr. Christian Chmelik Dr. Marko Bertmer Prof. Dr. Jörg Kärger Prof. Dr. Jürgen Haase Prof. Dr. Harald Krautscheid 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(29):8862-8866
The development of water‐mediated proton‐conducting materials operating above 100 °C remains challenging because the extended structures of existing materials usually deteriorate at high temperatures. A new triazolyl phosphonate metal–organic framework (MOF) [La3 L 4(H2O)6]Cl ? x H2O ( 1 , L 2?=4‐(4H‐1,2,4‐triazol‐4‐yl)phenyl phosphonate) with highly hydrophilic 1D channels was synthesized hydrothermally. Compound 1 is an example of a phosphonate MOF with large regular pores with 1.9 nm in diameter. It forms a water‐stable, porous structure that can be reversibly hydrated and dehydrated. The proton‐conducting properties of 1 were investigated by impedance spectroscopy. Magic‐angle spinning (MAS) and pulse field gradient (PFG) NMR spectroscopies confirm the dynamic nature of the incorporated water molecules. The diffusivities, determined by PFG NMR and IR microscopy, were found to be close to that of liquid water. This porous framework accomplishes the challenges of water stability and proton conduction even at 110 °C. The conductivity in 1 is proposed to occur by the vehicle mechanism. 相似文献
107.
Velocity Measurements of a Free-Surface Turbulent Flow Penetrating a Porous Medium Composed of Uniform-Size Spheres 总被引:1,自引:0,他引:1
We present a laboratory experimental investigation of the interaction between the turbulent flow in an open channel and the
turbulent flow within its very permeable bed. The bed was composed of uniform-size spheres packed in a cubic pattern. Fluid
velocities were measured by Particle Image Velocimetry (PIV), which allowed us to investigate the spatial distribution of
the time-averaged flow properties in the zone where they are strongly affected by the geometry of the rough bed. We investigate
the effect of bed porosity on these flow properties by comparing the results of two experimental configurations: one with
an impermeable bed composed of a single layer of spheres and another with a permeable bed composed of five layers. For the
latter case, PIV measurements of velocities were also carried out inside two pores adjacent to the bed surface. This data
provides an insight into the mechanisms of momentum transfer between the turbulent open channel flow and the turbulent flow
within its very permeable bed. 相似文献
108.
Abstract. Let M be a complete nondegenerate locally standard CR manifold. We show that a necessary and sufficient condition for M to be compact is that the Lie algebra of its infinitesimal CR automorphisms is semisimple. In general we realize M as a Mostow fibration over a compact CR manifoldB whose universal covering is a Cartesian product of Hermitian symmetric spaces and compact nondegenerate standard CR manifolds.
Received: 22 July 1998 / Published online: 8 May 2000 相似文献
109.
Stephen J. I. Shearan Jannick Jacobsen Prof. Ferdinando Costantino Dr. Roberto D'Amato Dr. Dmitri Novikov Prof. Norbert Stock Prof. Enrico Andreoli Dr. Marco Taddei 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(21):6579-6592
We report on the results of an in situ synchrotron powder X-ray diffraction study of the crystallisation in aqueous medium of two recently discovered perfluorinated CeIV-based metal–organic frameworks (MOFs), analogues of the already well investigated ZrIV-based UiO-66 and MIL-140A, namely, F4_UiO-66(Ce) and F4_MIL-140A(Ce). The two MOFs were originally obtained in pure form in similar conditions, using ammonium cerium nitrate and tetrafluoroterephthalic acid as reagents, and small variations of the reaction parameters were found to yield mixed phases. Here, we investigate the crystallisation of these compounds, varying parameters such as temperature, amount of the protonation modulator nitric acid and amount of the coordination modulator acetic acid. When only HNO3 is present in the reaction environment, only F4_MIL-140A(Ce) is obtained. Heating preferentially accelerates nucleation, which becomes rate determining below 57 °C. Upon addition of AcOH to the system, alongside HNO3, mixed-phased products are obtained. F4_UiO-66(Ce) is always formed faster, and no interconversion between the two phases occurs. In the case of F4_UiO-66(Ce), crystal growth is always the rate-determining step. A higher amount of HNO3 favours the formation of F4_MIL-140A(Ce), whereas increasing the amount of AcOH favours the formation of F4_UiO-66(Ce). Based on the in situ results, a new optimised route to achieving a pure, high-quality F4_MIL-140A(Ce) phase in mild conditions (60 °C, 1 h) is also identified. 相似文献
110.
Dr. Pier Luigi Gentili Dr. Federica Presciutti Dr. Fabio Evangelisti Dr. Ferdinando Costantino 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(14):4296-4307
A new family of layered metal(III)–phosphono–carboxylate nanostructures (M=Y, Eu, Tb, Er, and Yb) was hydrothermally synthesized and their structures and morphologies were characterized by X‐ray powder diffraction and TEM. 4‐[Bis(phosphonomethyl)amino]caproic acid and 4‐ [bis(phosphonomethyl)amino]undecan‐ oic acid, with general formula (H2O3PCH2)2NR (R=C5H10COOH (P2CAPR) and C10H22COOH (P2UND), respectively) were used as building blocks for the preparation of novel layered hybrid materials in which the inorganic layers were composed of MO7 or MO8 polyhedra and PO3C tetrahedra. The interlayer region was occupied by carboxyalkyl chains. These layered compounds were easily dispersed as stable solutions in alkylamine/water upon ultrasonication. These dispersions were constituted of rectangular elongated nanoparticles (NPs), which showed a distribution of sizes ranging from 20–500 nm. These new materials had interesting photophysical properties because they were multiluminescent compounds. These properties gave rise to several emission bands, which were spread over the broad spectroscopic region, from the near‐UV up to the near‐IR regions. Each emission band had a specific lifetime, which ranged from the sub‐ps to the ms scale. 相似文献