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61.
Daniel J. Arrigo Luis R. Suazo Olabode M. Sule 《Journal of Mathematical Analysis and Applications》2007,333(1):52-67
A symmetry analysis is performed on a (2+1)-dimensional linear diffusion equation with a nonlinear source term involving the dependent variable and its spatial derivatives. In the first part of the paper, we use the classical method to classify source terms where the original equation admits a nontrivial symmetry. In the second part of the paper, we use the nonclassical method and show that we simply recover the classical symmetries. 相似文献
62.
Sabriye Yusan Mahmoud A. A. Aslani D. Alkim Turkozu Hasan A. Aycan Sule Aytas Sema Akyil 《Journal of Radioanalytical and Nuclear Chemistry》2010,283(1):231-238
In this work, sorption of uranium ions on volcanic tuff collected from the deposits located at the Tendurek of Eastern Turkey
was investigated in batch technique. The effect of different parameters such as pH of the medium, contact time, uranium concentration
and temperature were investigated. The maximum removal of U(VI) was found to be 68% at pH 5.0, initial U(VI) concentration
of 75 mg L−1 and 30 °C. Thermodynamic parameters, such as enthalpy of adsorption ∆H°, free energy change ∆G° and entropy change ∆S° have been also calculated and interpreted. The suitability of the Langmuir, Freundlich and Dubinin-Radushkhevic adsorption
models to the equilibrium data was investigated for uranium-volcanic tuff system. The results suggest that volcanic tuff can
be used as efficient and cost effective adsorbents for uranium ion removal. 相似文献
63.
Deyu Wang Sule Erten Ela Shaik M. Zakeeruddin Peter Pechy Ivan Exnar Qing Wang Michael Grätzel 《Electrochemistry communications》2009,11(7):1350-1352
The poor electronic conductivity of LiFePO4 has been one of the major issues impeding it from achieving high power and energy density lithium-ion batteries. In this communication, a novel polymer-wiring concept was proposed to improve the conduction of the insulating electrode material. By using a polymer with tethered “swing” redox active molecules (S) attached on a polymer chain, as the standard redox potential of S matches closely the Fermi level of LiFePO4, electronic communication between the redox molecule and LiFePO4 is established. Upon charging, S is oxidized at the current collector to S+, which then delivers the charge (holes) to the LiFePO4 particles by intermolecular hopping assisted by a “swing” – type motion of the shuttle molecule. And Li+ is extracted. Upon discharging, the above process is just reversed. Preliminary studies with redox polymer consisting of poly (4-vinylpyridine) and phenoxazine moiety tethered with a C12 alkyl chain have shown promising result with carbon-free LiFePO4, where effective electron exchange between the shuttle molecule and LiFePO4 has been observed. In addition, as the redox polymer itself could act as binder, we anticipate that the polymer-wiring concept would provide a viable approach to conducting-additive and binder free electrode for high energy density batteries. 相似文献
64.
Oncul S Demchenko AP 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,65(1):179-183
The 3-hydroxyflavone (3HF) and its derivatives are the classical objects in the studies of the mechanisms of excited-state intramolecular proton transfer (ESIPT) reaction due to very frequent observation of two separate bands in fluorescence emission belonging to reactant and reaction product. Those of them possessing electron-donor groups in 4' position find many applications as fluorescence sensors and probes because of their much higher sensitivity of their two-band ratiometric response to interactions with the environment. We report on the strong differences between 3HF and such derivatives in the behavior of their fluorescence spectra as a function of temperature. The thermal quenching changes the intensity ratio of two bands strongly for 3HF but does not change it for its studied derivatives. These results are interpreted in terms of different kinetic mechanisms of ESIPT reaction. In 3HF the equilibrium between the two excited-state species is not established prior to emission, so that the ESIPT reaction is under kinetic control, but in these derivatives the equilibrium is established faster than the emission and the reaction is under thermodynamic control. We suggest that the thermal perturbation of fluorescence spectra can be an extremely simple and convenient alternative to time-resolved spectroscopy for determining if slow irreversible or fast reversible ESIPT reaction gives rise to two bands of fluorescence spectra of similar magnitude. This is essential for the development of new wavelength-ratiometric fluorescence sensors and probes. 相似文献
65.
Atahan S Kłos J Zuchowski PS Alexander MH 《Physical chemistry chemical physics : PCCP》2006,8(38):4420-4426
We report an ab initio study of the van der Waals region of the O(3P)-H2 potential energy surface based on RCCSD(T) calculations with an aug-cc-pVQZ basis supplemented by bond functions. In addition, an open-shell implementation of symmetry-adapted perturbation theory (SAPT) is used to corroborate the RCCSD(T) calculations and to investigate the relative magnitudes of the various contributions to the van der Waals interaction. We also investigate the effect of the spin-orbit coupling on the position and depth of the van der Waals well. We predict the van der Waals minimum to occur in perpendicular geometry, and located at a closer distance than a secondary well in colinear geometry. The potentials obtained in the present study confirm the previous calculations of Alexander [M. H. Alexander, J. Chem. Phys., 1998, 108, 4467], but disagree with the earlier work of Harding and co-workers [Z. Li, V. A. Apkarian and L. B. Harding, J. Chem. Phys., 1997, 106, 942] as well as with recently refitted surfaces of Brand?o and coworkers [J. Brand?o, C. Mogo and B. C. Silva, J. Chem. Phys., 2004, 121, 8861]. Inclusion of spin-orbit coupling reduces the depth of the van der Waals minimum without causing a change in its position. 相似文献
66.
Jun Wang Gregory Dam Sule Yildirim William Rand Uri Wilensky James C. Houk 《Complexity》2008,14(2):29-45
The cerebellum and basal ganglia are reciprocally connected with the cerebral cortex, forming many loops that function as distributed processing modules. Here we present a detailed model of one microscopic loop between the motor cortex and the cerebellum, and we show how small arrays of these microscopic loops (CB modules) can be used to generate biologically plausible motor commands for controlling movement. A fundamental feature of CB modules is the presence of positive feedback loops between the cerebellar nucleus and the motor cortex. We use nonlinear dynamics to model one microscopic loop and to investigate its bistable properties. Simulations demonstrate an ability to program a motor command well in advance of command generation and an ability to vary command duration. However, control of command intensity is minimal, which could interfere with the control of movement velocity. To assess these hypotheses, we use a minimal nonlinear model of the neuromuscular (NM) system that translates motor commands into actual movements. Simulations of the combined CB‐NM modular model indicate that movement duration is readily controlled, whereas velocity is poorly controlled. We then explore how an array of eight CB‐NM modules can be used to control the direction and endpoint of a planar movement. In actuality, thousands of such microscopic loops function together as an array of adjustable pattern generators for programming and regulating the composite motor commands that control limb movements. We discuss the biological plausibility and limitations of the model. We also discuss ways in which an agent‐based representation can take advantage of the modularity in order to model this complex system. © 2008 Wiley Periodicals, Inc. Complexity, 2008 相似文献
67.
68.
Three kinds of queues with Markovian arrival process and/or Markovian service process, are considered in this paper. In great generality, their basic steady-state distributions have asymptotically exponential tails. We investigate the sensitivity of these asymptotic decay rates to the small entrywise perturbations in the parameter matrices of the Markovian arrival process. 相似文献
69.
A high-resolution Fourier transform spectrum of the ν9 band of CD3CCH has been recorded at an apodized resolution of 0.004 cm−1 and analyzed. More than 1700 lines in the spectrum have been assigned and the parameters of the ν9 state derived. The standard deviation of the fit was 0.00034 cm−1. In order to achieve this fit it was necessary to include l-type doubling interaction and Fermi resonance between ν9 and the E component of 2ν10. 相似文献
70.
In this paper two solution methods to the MAP(t)/PH(t)/1/K queueing model are introduced, one based on the Backwards Euler Method and the other on the Uniformization Method. Both methods
use finite-differencing with a discretized, adaptive time-mesh to obtain time-dependent values for the entire state probability
vector. From this vector, most performance parameters such as expected waiting time and expected number in the system can
be computed. Also presented is a technique to compute the entire waiting (sojourn) time distribution as a function of transient
time. With these two solution methods one can examine any transient associated with the MAP(t)/PH(t)/1/K model including time-varying arrival and/or service patterns. Four test cases are used to demonstrate the effectiveness of
these methods. Results from these cases indicate that both methods provide fast and accurate solutions to a wide range of
transient scenarios.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献