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81.
Electrochemical Characterization of Carbon Solidlike Paste Electrode Assembled Using Different Carbon Nanoparticles 下载免费PDF全文
Seif Islam Rabie Malha Abdellatif Ait Lahcen Fabiana Arduini Ali Ourari Aziz Amine 《Electroanalysis》2016,28(5):1044-1051
Solid like carbon paste electrodes (SCPEs) are built using different carbon materials namely carbon black N110, N220, N375, N772 and acetylene black. The electrochemical behavior of these electrodes and the influence of carbon black/paraffin ratio were studied and the results were discussed and compared to other electrodes prepared with graphite, mesoporous carbon and nanopowder carbon. Cyclic voltammetry, amperometry and electrochemical impedance spectroscopy were employed for their electrochemical and analytical characterizations. Amperometric measurements using N110, N220, N375 SCPEs with solid paraffin, showed a linear response of benzoquinone concentration with a detection limit of 75, 32 and 171 nM respectively. 相似文献
82.
Jihane Zeghlouli Gwendoline Christophe Amine Guendouz Cherkaoui El Modafar Abdeljalil Belkamel Philippe Michaud Cdric Delattre 《Molecules (Basel, Switzerland)》2021,26(9)
Argan pulp is an abundant byproduct from the argan oil process. It was investigated to study the feasibility of second-generation bioethanol production using, for the first time, enzymatic hydrolysis pretreatment. Argan pulp was subjected to an industrial grinding process before enzymatic hydrolysis using Viscozyme L and Celluclast 1.5 L, followed by fermentation of the resulting sugar solution by Saccharomyces cerevisiae. The argan pulp, as a biomass rich on carbohydrates, presented high saccharification yields (up to 91% and 88%) and an optimal ethanol bioconversion of 44.82% and 47.16% using 30 FBGU/g and 30 U/g of Viscozyme L and Celluclast 1.5 L, respectively, at 10%w/v of argan biomass. 相似文献
83.
84.
We develop and implement a method for maximum likelihood estimation of a regime-switching stochastic volatility model. Our model uses a continuous time stochastic process for the stock dynamics with the instantaneous variance driven by a Cox–Ingersoll–Ross process and each parameter modulated by a hidden Markov chain. We propose an extension of the EM algorithm through the Baum–Welch implementation to estimate our model and filter the hidden state of the Markov chain while using the VIX index to invert the latent volatility state. Using Monte Carlo simulations, we test the convergence of our algorithm and compare it with an approximate likelihood procedure where the volatility state is replaced by the VIX index. We found that our method is more accurate than the approximate procedure. Then, we apply Fourier methods to derive a semi-analytical expression of S&P500 and VIX option prices, which we calibrate to market data. We show that the model is sufficiently rich to encapsulate important features of the joint dynamics of the stock and the volatility and to consistently fit option market prices. 相似文献
85.
Kristiaan Kerstens Amine Mounir Ignace Van de Woestyne 《European Journal of Operational Research》2011
The literature suggests that investors prefer portfolios based on mean, variance and skewness rather than portfolios based on mean–variance (MV) criteria solely. Furthermore, a small variety of methods have been proposed to determine mean–variance–skewness (MVS) optimal portfolios. Recently, the shortage function has been introduced as a measure of efficiency, allowing to characterize MVS optimal portfolios using non-parametric mathematical programming tools. While tracing the MV portfolio frontier has become trivial, the geometric representation of the MVS frontier is an open challenge. A hitherto unnoticed advantage of the shortage function is that it allows to geometrically represent the MVS portfolio frontier. The purpose of this contribution is to systematically develop geometric representations of the MVS portfolio frontier using the shortage function and related approaches. 相似文献
86.
Dambournet D Chapman KW Koudriachova MV Chupas PJ Belharouak I Amine K 《Inorganic chemistry》2011,50(13):5855-5857
X-ray pair distribution function (PDF) methods and first-principles calculations have been combined to probe the structure of electrochemically lithiated TiO(2) Brookite. Traditional powder diffraction studies suggest that Brookite amorphizes upon lithium insertion, with the Bragg reflections disappearing. However, PDF analysis indicates that the TiO(2) framework connectivity is maintained throughout lithium intercalation, with expansions along the a and b axes. The Li(+) ions within the framework are poorly observed in the X-ray PDF, which is dominated by contributions from the more strongly scattering Ti and O atoms. First-principles calculations were used to identify energetically favorable Li(+) sites within the Brookite lattice and to develop a complete structural model of the lithiated material. This model replicates the local structure and decreased intermediate range order observed in the PDF data. The analysis suggests that local structural distortions of the TiO(2) lattice accommodate lithium in five-coordinate sites. This structural model is consistent with the observed electrochemical behavior. 相似文献
87.
Nacer Ferrah Omar Abderrahim Mohamed Amine Didi Didier Villemin 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(3):721-730
A novel sorbent resin consisting of a Phosphonic Acid grafted on Merrifield Resin (PA-MR) for the extraction of uranyl from
nitrate media is described. The sorption behaviour of uranyl cation on PA-MR was investigated using batch equilibrium technique.
The effects of parameters such as shaking speed, pH levels, contact time, metal concentrations, ionic strength and temperature
were reported. The results show that the sorption capacity increases with increasing both initial uranyl ion concentration
and temperature and decreases with increasing ionic strength. Therefore, the optimum condition for the present study should
be using 6.6 mg adsorbent per 1.0 mg uranyl in solution with pH 3.6 and shaking at 250 rpm for 180 min. The adsorption behavior
of the system was also investigated and found to be in line with Langmuir isotherm. The kinetic data was well described by
the pseudo second-order. Thermodynamics data leads to endothermic process ∆H = + 31.03 kJ−1 mol−1, ∆S = + 146.64 J mol−1 K−1 and ∆G = −11.96 kJ mol−1 at 20 K. ∆G decreased to negatives values with increasing temperature indicating that the process was more favoured at high temperature. 相似文献
88.
Josefina Calvo Quintana Fabiana Arduini Aziz Amine Kees van Velzen Giuseppe Palleschi Danila Moscone 《Analytica chimica acta》2012
This work reports the optimisation of a new analytical method for lead ion detection in milk; the electrochemical detection scheme is based on the method that was described in Part I [1]. It features the use of a disposable, environmentally friendly bismuth film electrode to replace the traditionally used (toxic) mercury one while here we report an arduous development of sample treatment so that the simple device can be applied as a screening tool in many settings. For this purpose, a milk pre-treatment procedure by means of wet digestion with HCl, HClO4, and H2O2 combined with an ultrasonic treatment was developed. The detection of lead ions in treated milk was then carried out using a disposable screen-printed electrode modified with Nafion® and an “in situ” bismuth film, with the analysis being performed in anodic stripping voltammetry mode. The analytical method developed allows the detection of milk contaminated with lead ions at a concentration of 20 μg Kg−1 (legal limit) and it can be proposed as a screening method for routine analysis of lead ions in milk with the advantage of employing inexpensive and portable instrumentation. Moreover, dedicated software supported by a portable instrument introduces procedures that are essential to avoid distortion from ambient lead contamination and also makes it possible for an unskilled operator to carry out each step of the analysis. 相似文献
89.
Amine Aribi Ahmad El Soufi 《Calculus of Variations and Partial Differential Equations》2013,47(3-4):437-463
We establish inequalities for the eigenvalues of the sub-Laplace operator associated with a pseudo-Hermitian structure on a strictly pseudoconvex CR manifold. Our inequalities extend those obtained by Niu and Zhang (Pac J Math 208(2):325–345, 2003 [26]) for the Dirichlet eigenvalues of the sub-Laplacian on a bounded domain in the Heisenberg group and are in the spirit of the well known Payne–Pólya–Weinberger and Yang universal inequalities. 相似文献
90.
Abouimrane A Dambournet D Chapman KW Chupas PJ Weng W Amine K 《Journal of the American Chemical Society》2012,134(10):4505-4508
A new class of selenium and selenium-sulfur (Se(x)S(y))-based cathode materials for room temperature lithium and sodium batteries is reported. The structural mechanisms for Li/Na insertion in these electrodes were investigated using pair distribution function (PDF) analysis. Not only does the Se electrode show promising electrochemical performance with both Li and Na anodes, but the additional potential for mixed Se(x)S(y) systems allows for tunable electrodes, combining the high capacities of S-rich systems with the high electrical conductivity of the d-electron containing Se. Unlike the widely studied Li/S system, both Se and Se(x)S(y) can be cycled to high voltages (up to 4.6 V) without failure. Their high densities and voltage output offer greater volumetric energy densities than S-based batteries, opening possibilities for new energy storage systems that can enable electric vehicles and smart grids. 相似文献