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81.
82.
The inverse 1-median problem consists in modifying the weights of the customers at minimum cost such that a prespecified supplier becomes the 1-median of modified location problem. A linear time algorithm is first proposed for the inverse problem under weighted l ?? norm. Then two polynomial time algorithms with time complexities O(n log n) and O(n) are given for the problem under weighted bottleneck-Hamming distance, where n is the number of vertices. Finally, the problem under weighted sum-Hamming distance is shown to be equivalent to a 0-1 knapsack problem, and hence is ${\mathcal{NP}}$ -hard. 相似文献
83.
An inhibitory kinetic fluorimetric method is reported for the determination of trace bisphenol S (BPS). The proposed method is based on the inhibitory effect of BPS on the fluorescence quenching of rhodamine B (RhB) caused by potassium bromate in a dilute phosphoric acid medium. Under the optimal conditions of the experiment, the detection limit for BPS was 0.021 mg/L, and the linear range of determination was from 0.035 mg/L to 0.750 mg/L. The relative standard deviations of 11 measurements for 0.20 mg/L and 0.40 mg/L BPS solutions were 2.74 % and 1.87 %, respectively. The method was successfully applied to the determination of bisphenol S derived from commercially available plastic film samples in hot water. A possible reaction mechanism of the inhibitory effect of BPS on the fluorescence quenching of RhB was proposed. 相似文献
84.
Electrocatalysis on the degradation of methyl orange is investigated using Sb2O3‐loaded activated carbon (Sb2O3/AC), a new particle electrode. The electrode was prepared by an impregnation method. An orthogonal array with four factors and three levels was selected to carry out the experiment. Electrocatalysis on the degradation of methyl orange through Sb2O3/AC was characterized by a series of parameters, including the amount of the particle electrode, the concentration of Na2SO4, the cell voltage, and the electrolysis time, and the results were compared with those of a conventional AC particle electrode. The results indicate that calcination temperature has the greatest impact on the catalytic activity of the particle electrode. The optimal conditions for preparing the Sb2O3/AC electrode include an 8 mL SbCl3 solution, 90 min hydrolysis time, 400 °C calcination temperature, and 180 min calcination time. As well, the degradation efficiency of the Sb2O3/AC electrode is consistently higher than that of the AC electrode under the same electrolysis conditions. The electrochemical oxidation of methyl orange of both electrodes conformed to pseudo first‐order kinetics, but the rate constant of the Sb2O3/AC electrode was 2.29 times that of the AC electrode; this is likely due to the high electrocatalytic activity of the experimental electrode. The electrocatalysis results exhibited the synergetic effects of AC and Sb2O3 in the new particle electrode. 相似文献
85.
Flow injection analysis of ketoprofen based on the order transform second chemiluminescence reaction
Zhuang Y Cao G Ge C 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2012,85(1):139-144
This paper explores an order-transform-second-chemiluminescence (OTSCL) method combining the flow injection technique for the determination of ketoprofen. When ketoprofen solution was injected into the mixture after the end of the reaction of alkaline luminol and sodium periodate or sodium periodate solution was injected into the reaction mixture of ketoprofen and alkaline luminol, a new chemiluminescence (CL) reaction was initiated and strong CL signal was detected. A mechanism for the OTSCL has been proposed on the basis of the chemiluminescence kinetic characteristic, UV-visible absorption and chemiluminescent spectra. Under optimal experimental conditions, the CL response is proportional to the concentration of ketoprofen over the range of 2.0×10(-7) to 1.0×10(-5)mol/L with a correlation coefficient of 0.9950 and a detection limit of 8.0×10(-9)mol/L (3σ). The relative standard deviation for 11 repetitive determinations of 1.0×10(-6)mol/L ketoprofen is 2.9%. The utility of this method was demonstrated by determining ketoprofen in pharmaceutical formulations without interference from its potential impurities. 相似文献
86.
87.
Amar Si-Ammour Said Djennoune Maamar Bettayeb 《Communications in Nonlinear Science & Numerical Simulation》2009,14(5):2310-2318
In this paper, a sliding mode control design for fractional order systems with input and state time-delay is proposed. First, we consider a fractional order system without delay for which a sliding surface is proposed based on fractional integration of the state. Then, a stabilizing switching controller is derived. Second, a fractional system with state delay is considered. Third, a strategy including a fractional state predictor input delay compensation is developed. The existence of the sliding mode and the stability of the proposed control design are discussed. Numerical examples are given to illustrate the theoretical developments. 相似文献
88.
Yanbing Gong 《Fuzzy Optimization and Decision Making》2011,10(4):311-321
One of the key issues in the theory of ordered weighted averaging operator is the determination of OWA operator weights. In
this paper, a simple combination approach for obtaining minimal disparity OWA operator weights is proposed. The proposed approach
generates the OWA operator weights by minimizing the combination disparity between any two adjacent weights and its expectation.
This involves the formulation and solution of a linear programming model and a quadratic programming model for a given degree
of orness. A numerical example demonstrated simpleness and effectiveness of the methods proposed in this paper. 相似文献
89.
在马氏体不锈钢中引入氮,通过铌、钛固氮制备氮合金化堆焊合金. 利用往复式摩擦磨损试验机测试加氮和未加氮两种堆焊合金在不同载荷(5、10和15 N)下的摩擦磨损性能,研究了其摩擦磨损行为. 结果表明:在摩擦磨损过程中,堆焊合金表面承受周期性载荷,摩擦表面出现明显的切削痕和塑性变形,其磨损机制以磨粒磨损和表面疲劳磨损为主. 氮合金化堆焊合金中,碳氮化物沿马氏体基体、晶界弥散析出,起到了明显的细晶强化和弥散强化作用,增强了基体的塑性变形抗力以及抵御磨粒磨损的能力,使磨损表面切削痕数量更少、深度更浅,抗疲劳剥落现象得到明显改善. 相似文献
90.
Dr. Fei Wang Yanshuai Bi Kai Hu Dr. Xuejiao Wei 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(21):4874-4879
A catalyst in which Pd nanoparticles are supported on triangle-shaped La2O2CO3 nanosheets exposing predominantly the (001) planes (Pd/La2O2CO3-TNS; where TNS denotes triangular nanosheets) was prepared by a facile solvothermal method. The Pd/La2O2CO3-TNS catalysts exhibited excellent catalytic activity and recycling stability for hydrogenation of cinnamaldehyde to hydrocinnamaldehyde with turnover frequency of up to 41 238 h−1. This enhanced activity of Pd/La2O2CO3-TNS results from strong metal–support interactions. Structure analysis and characterization demonstrated that surface-oxygen-enriched La2O2CO3-TNS supports exposing (001) planes are beneficial to charge transfer between the Pd nanoparticles and triangle-shaped La2O2CO3 nanosheets and increase the electron density of Pd. Moreover, the modulated electronic states of the Pd/La2O2CO3-TNS catalysts can enhance the adsorption and activation of hydrogen to enhance the hydrogenation activity. 相似文献