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1.
The equilibrium CO2 sorption isotherms and isobars for rubbery EVA containing various amounts of vinyl acetate (VA) over a wide pressure range 10-340 atm and 25-52 °C were investigated. The normalized CO2 sorption concentration (in cm3 (STP) CO2/mole VA) isotherms of these polymers as a function of pressure consisted of two distinct regions turning at near Pc. The normalized sorption isotherms in these two distinct regions could be fairly described by two respective power laws: C=KaPna for above Pc and C=kbPnb for below Pc. The normalized CO2 sorption isotherms were found to be about the same for four EVA samples having different VA contents for below Pc, suggesting that the sorption process at below Pc may be mainly driven by the presence of carbonyl groups. At above Pc, the degree of crystallinity of the polymer appeared to be a major factor to affect the sorption process, with the higher the degree of crystallinity, the lower the normalized CO2 sorption concentration in the polymer. The sorption isobars of the polymer as a function of temperature were governed by the interplay of density, viscosity, and diffusivity of CO2 depending on the pressure studied. 相似文献
2.
A new technique of using ozone for water treatment is presented. This new technique consists of using a three-step-process composed firstly of ozone adsorption on an appropriate adsorbent, secondly water treatment, and thirdly regeneration of the adsorbent. Results regarding ozone adsorption (the first step) are presented in this paper. Different types of silica gel and a type of TiO2 have been tested for ozone adsorption. It was found that the physical characteristics of the silica gel affect its capacity for ozone. Titanium dioxide has shown ozone decomposition instead of adsorption as it contains Lewis acid sites. An exponential decrease of the silica gel capacity with its moisture content has been found. Linear isotherms in the range of ozone concentrations less than 100?g/m3 NTP have been found. A particle diffusion model with linear equilibrium isotherm has been used to model the breakthrough curves in fixed bed columns. 相似文献
3.
Matthew C. Morley Jennifer L. Henke Gerald E. Speitel Jr. 《Canadian Metallurgical Quarterly》2005,131(1):29-37
The high explosive (HE) compounds royal demolition explosive or hexahydro-1,3,5-trinitro-1,3,5-triazocine (RDX) and high melting explosive or octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) have been detected as groundwater contaminants at many military facilities. This research evaluated adsorption of RDX and HMX with granular activated carbon (GAC) to provide guidance for the design and operation of GAC adsorbers for treatment of HE-contaminated groundwater. Five GACs were screened using rapid small-scale column tests (RSSCTs), after which additional tests were performed with the two GACs that most effectively treated mixtures of RDX and HMX (Calgon F400 and Northwestern LB-830). GAC service life as a function of empty-bed contact time (EBCT) was determined using RSSCTs for a range of simulated full scale EBCTs with influent concentrations of 2,200 μg RDX/L and 350 μg HMX/L. Increasing the influent concentration of either contaminant significantly reduced the predicted service life, as did preloading GAC with groundwater natural organic matter. In batch isotherm tests, RDX was less adsorbable than HMX under all conditions studied. Concurrent loading of natural organic matter reduced the Freundlich K for RDX, whereas adsorption of HMX was not affected. Of the GACs tested, Calgon F400 most effectively removed RDX and HMX. 相似文献
4.
《International Journal of Hydrogen Energy》2020,45(30):15281-15293
In this work, absorption/desorption isotherms of the LaNi3·6Mn0·3Al0·4Co0.7 alloy, have been determined from the experimental data at three temperatures (TFluid = 298 K, TFluid = 303 K, and TFluid = 313 K). However, the experimental isotherms are compared with a proposed theoretical model. The physicochemical parameters of the proposed model are determined from the experimental data. Using these parameters, the absorption and desorption processes of hydrogen by the LaNi3·6Mn0·3Al0·4Co0.7 alloy can be compared. During the absorption/desorption process, the behaviors of each parameter are studied under the effect of temperature and pressure. In addition, internal energy, entropy, and enthalpy are calculated by using the proposed model. On the other hand, the temperature and pressure effects on the variation of these functions have been studied. The calculated physicochemical parameters suggested that the hydrogen absorption/desorption process in the LaNi3·6Mn0·3Al0·4Co0.7 alloy was feasible, spontaneous and exothermic in nature. 相似文献
5.
Arundo donax L., a member of Poaceae, was washed, dried, selected, pulverized, and then used for removal of Cu(II), Cd(II), Ni(II), Pb(II) and Zn(II) from aqueous solution. Series batch experiments were conducted to investigate the effects of contact time, pretreatment, particle size of biomass and solution pH on the biosorption capability of A. donax L. powder. The desorption characteristics and renewability of the biomass were also studied. The applicability of Langmuir and Freundlich isotherms was examined for the experimental data, so did the pseudo-first-order, pseudo-second-order and Elovich kinetic models. Results showed that alkali-treated A. donax L. biomass was more appropriate to be the bio-material for biosorption when compared to acid-treated, washed and virgin A. donax L. Owing to its fast adsorption rate, high uptake capacity and the renewability of facility, stem of A. donax L. treated with NaOH seems to be a promising biosorbent for removal of heavy metals from wastewater. 相似文献
6.
Selvaraj?Rengaraj Younghun?Kim Cheol?Kyun?Joo Kyunghee?Choi Jongheop?YiEmail author 《Korean Journal of Chemical Engineering》2004,21(1):187-194
The removal of copper from aqueous solution by ion exchange resins, such as 1200H and IRN97H, is described. Effect of initial
metal ion concentration, agitation time and pH on adsorption capacities of ion exchange resins was investigated in a batch
mode. The adsorption process, which is pH dependent, shows maximum removal of copper in the pH range 2–7 for an initial copper
concentration of 10 mg/L. The experimental data have been analyzed by using the Freundlich, Langmuir, Redlich-Peterson, Temkin
and Dubinin-Radushkevich isotherm models. The batch sorption kinetics have been tested for a first-order, pseudo-first order
and pseudo-second order kinetic reaction models. The rate constants of adsorption for all these kinetic models have been calculated.
Results showed that the intraparticle diffusion and initial sorption into resins of Cu(II) in the ion exchange resins was
the main rate limiting step. The uptake of copper by the ion exchange resins was reversible and thus has good potential for
the removal/recovery of copper from aqueous solutions. We conclude that such ion exchange resins can be used for the efficient
removal of copper from water and wastewater.
This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University. 相似文献
7.
8.
The water content–water activity–glass transition temperature relationships for sodium caseinate films containing glycerol were analyzed in caseinate based films containing oleic acid (OA) or beeswax (BW). Changes in the lipid phase transitions were also analyzed. Glass transitions of caseinate matrices as a function of water activity were modified by the presence of glycerol that plasticizes at low aw values to a great extent, but which limits the water plasticization effect. Incorporation of oleic acid in the film also induced changes in the water plasticization effect, thus indicating that lipid interactions with polymeric matrix occur, which was also reflected in the lipid melting behavior. OA binding produced a weakening effect in the matrix. When the lipid was beeswax, no notable protein–lipid interactions were revealed from the phase transition analysis. So, different characteristics of film matrix fillers (active or inactive) can be deduced from phase transition analysis and allow us to explain the greatly different impact of these on the film properties. 相似文献
9.
This paper presents a multi-level optimization strategy to obtain optimum operating conditions (four flow-rates and cycle
time) of nonlinear simulated moving bed chromatography. The multi-level optimization procedure (MLOP) approaches systematically
from initialization to optimization with two objective functions (productivity and desorbent consumption), employing the standing
wave analysis, the true moving bed (TMB) model and the simulated moving bed (SMB) model. The procedure is constructed on a
non-worse solution property advancing level by level and its solution does not mean a global optimum. That is, the lower desorbent
consumption under the higher productivity is successively obtained on the basis of the SMB model, as the two SMB-model optimizations
are repeated by using a standard SQP (successive quadratic programming) algorithm. This approach takes advantage of the TMB
model as well as surmounts shortcomings of the TMB model in the general case of any nonlinear adsorption isotherm using the
SMB model. The MLOP is evaluated on two nonlinear SMB cases characterized by i) quasi-linear/non-equilibrium and ii) nonlinear/nonequilibrium
model. For the two cases, the MLOP yields a satisfactory solution for high productivity and low desorbent consumption within
required purities. 相似文献
10.
Phosphoric acid-doped membranes based in poly[2,5-benzimidazole] (ABPBI) were obtained by a new low temperature casting procedure and by the classical high temperature casting from methanesulfonic acid. These membranes, which can be suitable for application in direct methanol proton exchange membrane (PEM) fuel cells, were studied in relation with their phosphoric acid doping level by measuring the free and bonded acid. The water isotherms were also determined for the low and high temperature casted ABPBI membranes. Both, acid and water sorption properties, were compared with those determined in poly [2-2′-(m-fenylene)-5-5′ bibenzimidazole] (PBI) membranes. The water sorption of the ABPBI membranes over the range of all water activity is described by the modified BET equation, commonly known as Guggenheim–Anderson–de Boer (GAB) and a two-parameters empirical isotherm. The acid uptake behaviour of the membranes prepared by low and high temperature casting are related with differences in their supramolecular structure. 相似文献