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排序方式: 共有190条查询结果,搜索用时 15 毫秒
41.
Masoud Bodaghi Hesam Zolfonoon Mohammadreza Tahriri Meysam Karimi 《Solid State Sciences》2009,11(2):496-500
In this present work, the synthesis of nanocrystalline α-Al2O3 using pure aluminum (Al) and Fe2O3 (hematite) as the precursors by mechanical alloying technique has been studied. The formation of α-Al2O3 nanocrystallites occurs during the solid-state reaction and through the reduction treatment. Also in this paper, effects of milling time on particle size and the lattice strain nanocrystalline α-Al2O3 have been investigated. Obtained powders were evaluated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential thermal analysis (DTA), thermal gravimetric analysis (TGA) and X-ray diffraction (XRD). The obtained results indicated that a reduction reaction was completed after 2 h milling in a planetary mill. The crystallite size of obtained α-alumina (α-Al2O3) was in general about 12 nm. Finally, the results showed appropriate homogeneity and dispersion of related nanocrystalline. 相似文献
42.
Mohammadreza Khanmohammadi Amir Bagheri Garmarudi Nafiseh Khoddami Keyvan Shabani Mohammadreza Khanlari 《Microchemical Journal》2010,95(2):337-340
Determination of particle size is one of the critical parameters in nanotechnology. The relationship between particle size and diffuse reflectance (DR) spectra in near-infrared region has been applied to introduce a method for estimation of particle size. Back-propagation artificial neural network (BP-ANN) as a nonlinear model was applied to estimate average particle size based on near-infrared diffuse reflectance spectra. Thirty five different nano TiO2 samples with different particle size were analyzed by DR-FTNIR spectrometry and the obtained data were processed by BP-ANN. The network was trained by 30 samples and was evaluated by the remaining 5 samples. In order to establish whether the new method is applicable for estimation of particle size of nano structured samples, the optimized model was applied to analyze 44 nano TiO2 samples. It was observed that ANN using the back-propagation algorithm is capable of generalization and could correctly predict the average particle size of nano-sized particles. 相似文献
43.
Ali Khalaj Morteza Pirali Hogatollah Matloubi Reza Dowlatabadi 《Monatshefte für Chemie / Chemical Monthly》2001,132(6):747-752
Summary. Several novel N-(2,3-dihydro-2-oxo-5-phenyl-1H-1,4-benzodiazepin-3-yl)-2-carboxamides were prepared by acyl coupling of 2-aminobenzophenones with α-(benzotriazol-1-yl)-N-acylglycines
followed by displacement of the benzotriazole ring with ammonia and cyclization of the resulting monoacyl aminals. In addition
to high yields and shorter reaction sequences due to avoiding deprotection and acylation of the protected 3-amino-1,4-benzodiazepin-2-one
intermediates, the present approach did not involve the use of toxic and odoriferous materials as is the case with other methods.
Received September 20, 2000. Accepted (revised) November 29, 2000 相似文献
44.
45.
Synthesis of molecularly imprinted polypyrrole as an adsorbent for solid‐phase extraction of warfarin from human plasma and urine
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The aim of this work was to develop a method for the clean‐up and preconcentration of warfarin from biological sample employing a new molecularly imprinted polymer (MIP) as a selective adsorbent for solid‐phase extraction (SPE). This MIP was synthesized using warfarin as a template, pyrrole as a functional monomer and vinyl triethoxysilane as a cross‐linker. The molar ratio of 1:4:20 (template–functional monomer–cross‐linker) showed the best results. Nonimprinted polymers (NIPs) were prepared and treated with the same method, but in the absence of warfarin. The prepared polymer was characterized by Fourier transmission infrared spectrometry and scanning electron microscopy. An adsorption process (SPE) for the removal of warfarin using the fabricated MIPs and NIPs was evaluated under various conditions. Effective parameters on warfarin extraction, for example, type and volume of elution solvent, pH of sample solution, breakthrough volume and maximum loading capacity, were studied. The limits of detection were in the range of 0.0035–0.0050 µg mL?1. Linearity of the method was determined in the range of 0.0165–10.0000 µg mL?1 for plasma and 0.0115–10.0000 µg mL?1 for urine with coefficients of determination (R2) ranging from 0.9975 to 0.9985. The recoveries for plasma and urine samples were >95%. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
46.
47.
Anna M. Fyhn Xiaodong Yang Mohammadreza Nematollahi John C. Walmsley Ursula J. Gibson 《Journal of Solid State Electrochemistry》2014,18(1):13-18
We demonstrate the anodic electrodeposition of copper-doped AgO at high pH using a silver counter-electrode. Precipitates from a mixture of nitrates and NaOH provided source material for the deposition, and application of a moderate anodic voltage (0.9 V) to the substrate led to deposition of crystalline nanoparticles with incorporated copper. Further increase of the NaOH concentration reduced the amount of copper in the crystals, and higher voltages degraded the crystal quality. XRD confirms the underlying structure to be that of AgO, and Auger and energy dispersive x-ray analyses confirm copper concentrations of approximately 3 % in the crystals. 相似文献
48.
In this paper, a new approach is proposed for nondestructive characterization of immersed and embedded isotropic rod-shaped samples by inversion of acoustic scattering data. The normal mode expansion technique is used for modelling the scattered field and the compression incident and compression scattered waves are considered. Genetic algorithm is the inversion technique used for estimating the elastic wave velocities and density of the rods from their measured backscattered pressure spectrum. The inversion technique is capable of computing the parameter values that best fit a particular set of data. A perturbation study is conducted on the sensitivity of the resonance frequencies to changes in elastic properties and density of the rods. The numerical results indicate that proper selection of resonance frequencies leads to accurate measurement of elastic constants and density. The proposed approach showed very good convergence and the results obtained were found to agree very well with available data. 相似文献
49.
Mohammadreza Gharibreza John Kuna Raj Ismail Yusoff Zainudin Othman Wan Zakaria Wan Muhamad Tahir Muhammad Aqeel Ashraf 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(3):1715-1730
The Bera Lake basin is a lacustrine mire system and the largest natural lake in Peninsular Malaysia. Three cores were collected from the lake sediments in order to assess sediment quality and ecological risks for aquatic life and human health. An index analysis approach (C f , C d , E r , and IR) and fallout 210Pb and 137Cs radioisotopes were applied to assess the impacts of environmental evolutionary changes. Sediment chronology was determined using the Constant Rate of Supply model with the resultant ages verified by 137Cs horizons. Although the general contamination factors indicate low risk conditions in Bera Lake the risks associated with individual layers ranged from moderate to considerable. Five deforestation phases can be identified in the dated sediment cores with distinct variations in heavy metal influxes since 1972. These phases are in excellent agreement with the dates of land clearance and development projects undertaken over the past four decades. This study has highlighted the capability of contamination factors and chronological methods in environmental evolutionary studies where catchments have experienced extensive land use changes. The destiny of heavy metal influxes into a lake can also be revealed using this methodology. 相似文献
50.
Hamidreza Ali-Asgari Dehaghi Saeedeh Mazinani Davood Zaarei Mohammadreza Kalaee Hamed Jabari Navid Sedaghat 《Journal of Thermal Analysis and Calorimetry》2013,114(1):185-194
Systematic study about the effect of acrylonitrile–butadiene rubber (NBR) concentration on the fracture toughness and thermal behavior of epoxy resin is conducted in this study. NBR is solved in an aromatic hydrocarbon solvent and is added to epoxy resin. We used diethylene-teriamin as the curing agent for epoxy resin. Tensile test results, performed followed by molding procedure, show that the toughness is improved owing to the increase of rubber content. Scanning electron microscopy (SEM) and atomic force microscopy besides thermogravimetric analysis (TG) are used to investigate the epoxy/rubber interface and chemical decomposition of the resultant mixture. The thermal behavior of cured epoxy resin was analyzed via TG instrument at different heating rates. Thermogravimetry curves showed that the thermal decomposition of epoxy system was occurred in only one stage regardless of the rubber content. The apparent activation energies of the rubber/epoxy systems containing 0, 5, and 10 phr of rubber were determined by Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose, and Friedman methods. The results prove that the thermal stability of epoxy resin was decreased with enhancing the rubber content. However, the trend of changing activation energy versus conversions is totally different followed by adding the elastomer to the system compared to neat epoxy resin. Moreover, the results obtained via our proposed facile solution blending method are compared to those of resins modified with nano-powdered elastomer. 相似文献