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151.
Molecular Dyads Comprising Metalloporphyrin and Alkynylplatinum(II) Polypyridine Terminal Groups for Use as a Sensitizer in Dye‐Sensitized Solar Cells
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Eric Chi‐Ho Kwok Dr. Mei‐Yee Chan Dr. Keith Man‐Chung Wong Prof. Dr. Vivian Wing‐Wah Yam 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(11):3142-3153
A new class of molecular dyads comprising metalloporphyrin‐linked alkynylplatinum(II) polypyridine complexes with carboxylic acids as anchoring groups has been designed and synthesized. These complexes can sensitize nanocrystalline TiO2 in dye‐sensitized solar cell (DSSC) studies. The photophysical, electrochemical, and luminescence properties of the complexes were studied and their excited‐state properties were investigated by nanosecond transient absorption spectroscopy, with the charge‐separated [Por.??{(C?C)Pt(tBu3tpy)}.+] state observed upon excitation. Excited‐state redox potentials were determined; the electrochemical data supports the capability of the complexes to inject an electron into the conduction band of TiO2. The complexes sensitize nanocrystalline TiO2 and exhibited photovoltaic properties, as characterized by current–voltage measurements under illumination of air mass 1.5 G sunlight (100 mWcm?2). A DSSC based on one of the complexes showed a short‐circuit photocurrent of 10.1 mAcm?2, an open‐circuit voltage of 0.64 V, and a fill factor of 0.52, giving an overall power conversion efficiency of 3.4 %. 相似文献
152.
153.
Yingkui Yang Zhifang Yang Qiang Zhao Xinjian Cheng Sie Chin Tjong Robert Kwok Yiu Li Xiaotao Wang Xiaolin Xie 《Journal of polymer science. Part A, Polymer chemistry》2009,47(2):467-484
Silica–polystyrene core‐shell particles were successfully prepared by surface‐mediated reversible addition fragmentation chain transfer (RAFT) polymerization of styrene monomer from the surfaces of the silica‐supported RAFT agents. Initially, macro‐RAFT agents were synthesized by RAFT polymerization of γ‐methacryloxypropyltrimethoxysilane (MPS) in the presence of chain transfer agents (CTAs). Immobilization of CTAs onto the silica surfaces was then performed by reacting silica with macro‐RAFT agents via a silane coupling. Grafting of polymer onto silica forms core‐shell nanostructures and shows a sharp contrast between silica core and polymer shell in the phase composition. The thickness of grafted‐polymer shell and the diameter of core‐shell particles increase with the increasing ratio of monomer to silica. A control experiment was carried out by conventional free radical emulsion copolymerization of MPS‐grafted silica and styrene under comparable conditions. The resulting data provide further insight into the chemical composition of grafted‐polymers that are grown from the silica surface through RAFT process. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 467–484, 2009 相似文献
154.
The Riemann solver is the fundamental building block in the Godunov‐type formulation of many nonlinear fluid‐flow problems involving discontinuities. While existing solvers are obtained either iteratively or through approximations of the Riemann problem, this paper reports an explicit analytical solution to the exact Riemann problem. The present approach uses the homotopy analysis method to solve the nonlinear algebraic equations resulting from the Riemann problem. A deformation equation defines a continuous variation from an initial approximation to the exact solution through an embedding parameter. A Taylor series expansion of the exact solution about the embedding parameter provides a series solution in recursive form with the initial approximation as the zeroth‐order term. For the nonlinear shallow‐water equations, a sensitivity analysis shows fast convergence of the series solution and the first three terms provide highly accurate results. The proposed Riemann solver is implemented in an existing finite‐volume model with a Godunov‐type scheme. The model correctly describes the formation of shocks and rarefaction fans for both one and two‐dimensional dam‐break problems, thereby verifying the proposed Riemann solver for general implementation. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
155.
156.
V. A. Gritsenko D. V. Gritsenko Yu. N. Novikov R. W. M. Kwok I. Bello 《Journal of Experimental and Theoretical Physics》2004,98(4):760-769
The short-range order and electron structure of amorphous silicon nitride SiNx (x<4/3) have been studied by a combination of methods including high-resolution X-ray photoelectron spectroscopy. Neither random bonding nor random mixture models can adequately describe the structure of this compound. An intermediate model is proposed, which assumes giant potential fluctuations for electrons and holes, caused by inhomogeneities in the local chemical composition. The characteristic scale of these fluctuations for both electrons and holes is about 1.5 eV. The photoluminescence in SiNx is interpreted in terms of the optical transitions between quantum states of amorphous silicon clusters. 相似文献
157.
We propose a discrete Boltzmann model for microfluidics based on the Boltzmann equation with external forces using a single relaxation time collision model. Considering the electrostatic interactions in microfluidics systems, we introduce an equilibrium distribution function that differs from the Maxwell-Boltzmann distribution by an exponential factor to represent the action of an external force field. A statistical mechanical approach is applied to derive the equivalent external acceleration force exerting on the lattice particles based on a mean-field approximation, resulting from the electro-static potential energy and intermolecular potential energy between fluid-fluid and fluid-substrate interactions. 相似文献
158.
A.B. Djurišić C.Y. Kwong T.W. Lau E.H. Li Z.T. Liu H.S. Kwok L.S.M. Lam W.K. Chan 《Applied Physics A: Materials Science & Processing》2003,76(2):219-223
Optical functions of tris (8-hydroxyquinoline) aluminum (Alq3) have been studied in the spectral range from 1.55 eV to 5 eV using spectroscopic ellipsometry. The samples have been deposited
by thermal evaporation on glass substrates. Optical functions of Alq3 deposited on unheated substrates and on substrates kept at 100 °C have been determined. The optical functions have been modeled
using point-to-point fitting, with the conventional oscillator model and modified oscillator model. It has been found that
point-to-point fitting gives the best agreement with the experimental data, and that the modified oscillator model yields
better agreement with the experimental data than the conventional oscillator model.
Received: 3 September 2001 / Accepted: 22 March 2002 / Published online: 5 July 2002
RID="*"
ID="*"Corresponding author. Fax: +852-2559/8738, E-mail: dalek@eee.hku.hk 相似文献
159.
(O--N--N)PtX] complexes as a new class of light-emitting materials for electrophosphorescent devices
The synthesis and photophysical properties of the robust Pt(II) emitters [(O--N--N)PtX] (HO--N--N = 6-(2-hydroxyphenyl)-2,2'-bipyridine and its derivatives; X = Cl, Br, I, or -CC-Ph) are reported. Yellow electroluminescent devices based on these materials display a low turn-on voltage (1 cd m(-2) at 4 V) and a high luminance (37000 cd m(-2)). Complex 2e, [(F(t)Bu2O--N--N)PtCl], has the highest thermal stability and gave the best OLED. 相似文献
160.
Smith AW Jaeger HM Rosenbaum TF Petrean AM Kwok WK Crabtree GW 《Physical review letters》2000,84(21):4974-4977
We study the vortex phase diagram in untwinned YBCO crystals with columnar defects. These randomly distributed defects are expected to induce a "Bose glass" phase of localized vortices exhibiting a vanishing resistance and Meissner effect for magnetic fields H( perpendicular) transverse to the columns. We directly observe the transverse Meissner effect using a Hall probe array. As predicted, the Meissner state breaks down at temperatures T(s) that decrease linearly as H( perpendicular) increases. However, T(s) lies far below the conventional melting temperature T(m) determined by a vanishing resistivity, suggesting a regime where vortices are effectively localized even when rotated off the columnar defects. 相似文献