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排序方式: 共有56条查询结果,搜索用时 31 毫秒
1.
The equilibrium extraction behaviour of Gd(III) using a chloroform/kerosine solution containing di(2-ethylhexyl)phosphoric acid (HDEHP), either alone or combined with one of three adductants, 1,10-phenanthroline monohydrate (phen), alpha,alpha'-dipyridyl(2,2'-bipyridine) (bipy) or trioctylphosphine oxide (TOPO) is described. The enhancement of the extraction by addition of such neutral adductants is explained in terms of adduct formation of the metal chelate in the organic phase. Among the three synergistic mixtures, 1,10-phenanthroline is the most promising for the extraction of the last member of light lanthanoids, gadolinium. Gadolinium ions are found to be extracted in the absence of phen, bipy or TOPO; the species was M(HA(2))(3) but M(HA(2))(3))(phen)(2) was found when phen was added and M(HA(2))(3)(bipy), M(HA(2))(3)(bipy)(2) was found when bipy was added and M(HA(2))(3)(TOPO) was found when TOPO was added. The compositions of the extracted species are obtained from the slope analysis method. pH (1 2 ) values were also obtained. The stoichiometry, extraction constants and stability constants of these systems were determined. Synergistic extraction can be carried out at lower pH. 相似文献
2.
LetG be a nilpotent Lie group. The adapted nilpotent Fourier transform was introduced by D. Arnal and J. C. Cortet,:L(G) C
(V,L(2d
)), whereL(G) is the Schwartz space ofG andV × 2k
is aG-invariant Zariski open set ing
* the dual of the Lie algebra ofG. We prove the surjectivity of this transformation, which allows us to extend it to distribution spaces. 相似文献
3.
Angappa Gunasekaran Zahir Irani Thanos Papadopoulos 《The Journal of the Operational Research Society》2014,65(6):806-823
Sustainable operations management (SOM) can be defined as the operations strategies, tactics and techniques, and operational policies to support both economic and environmental objectives and goals. The subject of sustainability has gained much attention from both researchers and practitioners in the past 6–8 years. Most of the articles deal with sustainability from environmental perspectives, but a limited number of them integrate both economic and environmental implications or focus on trading-off between profitability, competitiveness and environmental dimensions. Moreover, there is a limited focus on modelling and analysis (MA) of SOM integrating and balancing the interests of both economic and environmental interests. Therefore, an attempt has been made in this paper to review the extant literature on SOM. The objective is to understand the definition of SOM and present the current status of research in MA, as well as future research directions in the field. Considering the recent focus of the subject, we review the literature on MA of SOM beginning in 2000 in order to make our study current and more relevant for both researchers and practitioners. Finally, a summary of findings and conclusions is reported. 相似文献
4.
The worldwide demand for energy continues to grow and the production of heavy crude is escalating due to shortage of conventional light crude. The transportation of heavy crude oil from the head-well to the refinery is a challenging task due to its high viscosity and low API gravity. Catalytic aquathermolysis is one of the most significant and cost-effective viscosity reduction techniques employed in the up gradation of the crude oil at elevated temperatures and hence to enhance oil extraction process. In this study, catalytic aquathermolysis of Omani heavy crude oil was performed using magnetite nanoparticles (NPs). The NPs were synthesised by reverse co-precipitation method using iron salts in alkaline medium. The synthesised NPs were characterized using Scanning Electron Microscopy (SEM), X-Ray Powder Diffraction (XRD), Energy Dispersive X- Ray analysis (EDX) and Fourier Transform Infrared Spectroscopy (FTIR). The XRD results exhibited a characteristic peak confirming the high purity of iron oxide nanoparticles. The FTIR spectral analysis designated two well-defined peaks corresponding to wave numbers of 500 ?cm?1 and 630 ?cm?1, endorses the presence of Fe–O. The catalytic aquathermolysis experiments were carried out in a Parr high temperature-high pressure batch reactor at different experimental conditions. The processing parameters in temperature range of 250 ?°C - 300 ?°C, 0.1% to 0.3% catalyst loading, water to oil ratio of 1:7 to 3:7 with 24–72 ?h of reaction time. The initial pressure in the reactor was maintained at 32 ?bars and the optimization was performed using the Taguchi method to maximize the level of heavy oil. An orthogonal array was employed to analyse the effects of mean response and mean signal-to-noise ratio (S/N) to upgrade the heavy oil. The regression analysis was used to establish a relationship between the viscosity and experimental parameters. The experimental outcomes indicates that the maximum reduction in viscosity occurred at a processing temperature of 300 ?°C, 1:7 ?W/O ratio, 0.1 ?wt% of catalyst concentration and 48 ?h of reaction time. Similarly, the optimum conditions for the reduction in API gravity were obtained at 280 ?°C temperature, 3:7 ?W/O ratio, 0.2 ?wt% of catalyst concentration and a reaction time of 24 ?h. 相似文献
5.
In GSI experiments, a light pseudoscalar boson of mass Φ 1.6 MeV may have been observed. In order to examine this possibility from a different aspect we propose to study the photo-and electro-production process of Φ-particles. We calculate the cross section of neutral and charged Φ-particles. We examine the possible role of these production mechanisms in the heavy ion collision processes. 相似文献
6.
Lithium manganese oxide powders have been successfully prepared by a molten salt synthesis using eutectic mixture of LiCl
and MnO2 salt at 900 °C. The synthesis was performed in open atmosphere. The crystalline powders were characterized for their phase
identification using X-ray diffraction analysis. The physicochemical properties of the lithium manganese oxide powders are
investigated by thermal analysis (thermo gravimetric analysis/ differential thermal analysis), Fourier transform infrared
spectroscopy, Raman spectroscopy, atomic absorption spectroscopy, electron spin resonance spectroscopy, and scanning electron
microscopy. This work shows the feasibility for obtaining lithium manganese oxide at low-temperature molten salt flux method. 相似文献
7.
Characteristics of phenol and chlorinated phenols sorption onto surfactant-modified bentonite 总被引:11,自引:0,他引:11
Surfactant-modified bentonite was synthesized by replacing adsorbed Na+ with long-chain alkyl quaternary ammonium cation, hexadecyltrimethylammonium bromide (HDTMAB). The sorption isotherms of phenol, p-chlorophenol, and 2,4-dichlorophenol were modeled according to the Langmuir and Freundlich equations. The Langmuir isotherm was found to describe the equilibrium adsorption data well. The mechanisms and characteristics of sorption of these ionizable organic contaminants onto surfactant-modified bentonite from water were investigated systematically and described quantitatively. The sorption properties are affected by the treatment conditions, such as amount of organobentonite, and the properties of organic compounds. Results indicated that adsorption of phenols from water was in proportion to their hydrophobicities, which increased with chlorine addition (phenol相似文献
8.
Dr. Chanchal Kumar Roy Syed Shaheen Shah Akter H. Reaz Sharmin Sultana Dr. Al-Nakib Chowdhury Dr. Shakhawat H. Firoz Dr. Md. Hasan Zahir Dr. Mohammed Ameen Ahmed Qasem Dr. Md. Abdul Aziz 《化学:亚洲杂志》2021,16(4):296-308
We demonstrate a facile efficient way to fabricate activated carbon nanosheets (ACNSs) consisting of hierarchical porous carbon materials. Simply heating banana leaves with K2CO3 produce ACNSs having a unique combination of macro-, meso- and micropores with a high specific surface area of ∼1459 m2 g−1. The effects of different electrolytes on the electrochemical supercapacitor performance and stability of the ACNSs are tested using a two-electrode system. The specific capacitance (Csp) values are 55, 114, and 190 F g−1 in aqueous 0.5 M sodium sulfate, organic 1 M tetraethylammonium tetrafluoroborate in acetonitrile, and pure ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) electrolytes, respectively. The ACNSs also shows the largest potential window of 3.0 V, the highest specific energy (59 Wh kg−1) and specific power (750 W kg−1) in [BMIM][PF6]. A mini-prototype device is prepared to demonstrate the practicality of the ACNSs. 相似文献
9.
The equilibrium extraction behavior of a series of trivalent lanthanide ions (Ln(3+)) using a chloroform-Kerosine solution containing Di(2-ethylhexyl)phosphoric acid, combined with an adductant, 1,10-phenanthroline monohydrate (phen), was studied. The enhancement of the extraction by addition of such a neutral adductant is explained in terms of the extraction of the quaternary complex, M(HX(2))(3)(phen)(2), in addition to the neutral complex, M(HX(2))(3), into the organic phase. The stoichiometry, extraction constants and separation factors of these systems were determined. The extraction constants of these systems partially follow the order of the atomic numbers. The synergistic extraction constants increased in the other Gd > Er > Ho > Eu > Ce > La > Pr and the highest separation factor was observed for ErHo (2.09). pH (1 2 ) values were also obtained. In this synergistic extraction system, both the extraction equilibrium constants and the separation factors were found to be greater than those of commercial extractants. 相似文献
10.
Hakim Mazrou Zahir Idiri Tassadit Sidahmed Malika Allab 《Journal of Radioanalytical and Nuclear Chemistry》2010,284(2):253-263
A new approach has been suggested to establish reliable response matrix of a CRNA Bonner Sphere Spectrometer equipped with
a high efficiency 10 mm diameter × 2 mm thick 6LiI (Eu) scintillation detector from thermal neutron energy up to 20 MeV. It combines the experimental response functions
obtained using a continuous neutron spectrum emitted from an 241Am-Be neutron source of known emission, with those obtained by Monte-Carlo (MC) calculations. Sensitivity analysis has been
performed to check the influence of pertinent parameters on the MC computed detector response. The parameters of interest
are the density of polyethylene moderators, the cross section library used in MCNP5 and two computing models depending on
the interactions of the neutrons in the detector. The calculated responses of the spectrometer to the 241Am-Be neutron source showed discrepancies depending on the sphere diameter when compared to our measured responses. However,
this difference was smaller compared with the experiments available in the literature. The enhancement achieved in the present
study is partly due to improved modeling in the MC calculations. To correct for the differences observed, a fitting factor
has been deduced for each sphere diameter and used to adjust the MC responses to the experimental ones. The obtained results
were subsequently compared to the experimental data of GSF-G spheres system obtained for a typical 4 mm diameter × 4 mm thick
6LiI scintillator for four ISO-8529 selected neutron energies (144.0 keV, 565 keV, 2.5 and 14.8 MeV). The present responses
were similar in shape but higher, in absolute values, by about two and half times for all spheres owing essentially to the
increase in active part of the detector. Finally, the CRNA-BSS response matrix containing 48 energy points from 0.01 eV to
20 MeV for 22 sphere diameters with a mean polyethylene density of 0.944 g/cm3 was constructed by applying a spline interpolation method. The released response matrix was then compared to data available
in the literature evaluated by Monte-Carlo calculations for a 4 mm × 4 mm 6LiI crystal scintillator. The obtained response matrix is intended for radiation protection applications at CRNA. 相似文献