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1.
The acid-base equilibria of three anionic sulfonephthalein dyes, viz., bromothymol blue (BTB), thymol blue (TB), and cresol red (CR), were studied spectroscopically in aqueous media containing
the water-soluble noninonic polymers polyvinyl alcohol (PVA) and polyethylene glycol (PEG) in the presence of an anionic surfactant,
sodium dodecyl sulfate (SDS). A partition equilibrium method was used to determine the equilibrium constant of partition of
the dyes between the micellar pseudo phase and aqueous phase in the presence of PVA and PEG. The critical aggregation concentrations
(CAC) of the surfactants in buffered aqueous systems containing the neutral polymers were also determined. The CAC of the
polymer-surfactant systems were found to be lower than the critical micelle concentration of such systems in the absence of
polymer, in otherwise identical conditions. The pH-dependent association constants, K
ass, of the sulfonephthalein dyes with the SDS-PVA system increased with the increase in molecular weight of the polymer. The
interactions of the dyes with the buffered aqueous SDS-PVA and SDS-PEG systems were found to be endothermic and entropy oriented.
In the polymer domain, the head group region of the micelles was more exposed at lower concentrations of the polymer, but
under excess polymer concentration they were increasingly shielded, which impaired their electrostatic interaction with the
dyes. 相似文献
2.
Well-defined poly(n-docosyl acrylate) (PDA) with narrow molecular weight distribution has been synthesized by atom transfer radical polymerization (ATRP) and reverse ATRP of n-docosyl acrylate (DA) at 80 °C in N,N-dimethylformamide using the carbon tetrabromide/FeCl3/2,2′-bipyridine (bpy) initiation system in the presence of 2,2′-azobisisobutyronitrile (AIBN) and benzoyl peroxide (BPO) as the source of reducing agent. The rates of polymerization for both the systems exhibit first-order kinetics with respect to the monomer, however, peroxide-initiated system shows slow rate of polymerization as compared to the azo-system. The effect of various reaction parameters on number average molecular weight (M n ) and molecular weight distribution (M w/M n ) have been investigated. The resulting PDA that obtained in presence of AIBN and BPO systems has been compared for both the conventional and reverse ATRP. The reverse ATRP initiated by peroxides behaves differently than that of the azo initiators. In reverse ATRP with BPO, the rate of polymerization (R p) has been significantly increased with the increase of BPO resulting higher M n and broader M w/M n . The reverse ATRP of DA did not exhibit living characteristics with BPO system. PDA has been characterized by GPC, FTIR, and NMR spectroscopy. 相似文献
3.
Kongkona Saikia Ponnusamy Senthil Kumar Abiram Karanam Rathankumar Sundar SaiLavanyaa Lakshmi Srinivasan Sivanesan Subramanian Hubert Cabana Mathilde Gosselin Vaidyanathan Vinoth Kumar 《IET nanobiotechnology / IET》2020,14(8):732
In the present study, amino‐functionalised mesoporous silica microspheres were utilised as support for the covalent immobilisation of Candida antarctica lipase B (CaLB) for the subsequent production of 2,5‐furandicarboxylic acid (FDCA) from 2,5‐diformylfuran (DFF). Under the optimised operating conditions of pH 6.5, particle/enzyme ratio of 1.25:1.0 and glutaraldehyde concentration of 4 mM, a maximum CaLB immobilisation yield of 82.4% on silica microspheres was obtained in 12.25 h. The immobilised CaLB was used for the synthesis of alkyl esters, which were utilised along with hydrogen peroxide for FDCA synthesis. The biocatalytic conversion of 30 mM DFF dictated a 77–79% FDCA in 48 h at 30°C; where the turnover number and turnover frequency of immobilised CaLB were 6220.73 mol mol−1 and 129.59 h−1, respectively, for ethyl acetate, against 6297.65 mol mol−1 and 131.2 h−1, respectively, for ethyl butyrate. Upon examining the operational stability, the immobilised CaLB exhibited high stability till five cycles of FDCA production.Inspec keywords: mesoporous materials, organic compounds, biotechnology, silicon compounds, renewable materials, catalysis, catalysts, enzymes, thermal stability, biofuelOther keywords: FDCA production, amino‐functionalised mesoporous silica microspheres, greener production, 2,5‐furandicarboxylic acid, covalent immobilisation, 2,5‐diformylfuran, CaLB immobilisation, Candida antarctica lipase B immobilisation, ethyl butyrate, time 48.0 hour, temperature 30.0 degC, time 12.25 hour 相似文献
4.
Somip Borphukan Maitrayee Saikia Urmilla Baruah Arvind Gautam Shashi D. Baruah Prakash J. Saikia 《应用聚合物科学杂志》2019,136(39):47994
The emulsion copolymerization of ethylene with butyl methacrylate (BMA) was carried out in an aqueous medium at 60 °C under moderate reaction conditions. The polymer system is well controlled with a linear increase in the molecular weight (Mn) versus ethylene feed pressure and narrow molecular weight distributions (>1.36) were observed throughout the copolymerization reaction. The spectroscopic analyses confirm the presence of acrylate functional as well as methylene group in the synthesized poly(ethylene-co-BMA) copolymer. Morphological behavior of poly(ethylene-co-BMA) has been studied using SEM and TEM analyses. Thermal stability of the copolymers was investigated by thermogravimetric analysis and it was observed that the copolymer is stable up to 380 °C. X-ray diffraction analysis confirmed the amorphous behavior of poly(ethylene-co-BMA). Dynamic light scattering measurement confirms the formation of poly(ethylene-co-BMA) nanoparticles. The particle size of copolymer nanoparticles were in the range of 85–108 nm with low polydispersity indexes (>0.2). The viscous and the elastic property of the copolymer were investigated and established that at high temperature elastic behavior predominant over viscous effect. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47994. 相似文献
5.
The paper reports the synthesis of nano-crystalline ceramics like titanium dioxide and titanium nitride using a plasma chemical experimental reactor powered by a multi-segment (cascaded) arc plasma torch. The precursor-laden plasma beam emerging from the torch anode section expands supersonically through a converging nozzle to a low-pressure collection chamber. This results in a uniform and controlled gas dynamic quenching ensuring rapid synthesis of pure, un-coagulated free-flowing particles with a narrow size distribution. Simple Langmuir probes and calorimetric energy balance methods are used for plasma and reactor characterization, while X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), Raman and X-ray photoelectron spectroscopy (XPS) techniques have been used for product analysis. It is shown that size distribution of both the product particles is comparatively narrower than that found in most thermal plasma assisted laboratory synthesis studies. The expansion process was observed to produce a non-equilibrium electron population, which could charge up the particles after nucleation and hence could curb unwanted coagulation. 相似文献
6.
Occurrence of some hazardous metals in Indian coals 总被引:1,自引:0,他引:1
Studies on hazardous metals pollution through various processes of utilization of the Assam (India) coals suffer from the
lack of reliable information on the level of trace and heavy metals in them. Four representative coal samples with high sulphur
from Ledo, Tikak, Tipong and Baragolai collieries of Makum coalfield, Assam, India were studied for the occurrence of Al,
Bi Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Se, V, and Zn by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES)
methods. Six of the metals (Cd, Cr, Co, Mn, Ni, and Pb) found to be present in low to moderate concentrations were identified
as Hazardous Air Pollutants (HAPs) in the 1990 Clean Air Act Amendments (CAAA) USA. The concentration of Fe, Mg and Al was
observed to be higher than the rest of the metals. Significant variation of these metal contents in the four coals samples
was observed with no noteworthy statistical relationship with the ash and carbon contents of the coals. The concentrations
of metals in the samples are within the average world coal range. It was also observed that there is no definite trend of
metal concentration with reference to different collieries of Assam. The association of some metals in the coal matrix was
also discussed. XRD and FT-IR patterns of the coals also supported the presence of these metals.
Published in Russian in Koks i Khimiya, 2009, no. 2, pp. 12–17.
The article is published in the original. 相似文献
7.
Bhuyan Pubanita Bhuyan Amar Jyoti Gogoi Palash Jyoti Mahanta Abhijit Tamuly Chandan Saikia Lakhinath 《Catalysis Letters》2022,152(9):2705-2715
Catalysis Letters - Due to high surface area and low swelling property, Montmorillonite–K10 (MMT–K10) has been gaining widespread applications in heterogeneous catalysis as a material... 相似文献
8.
9.
Dimpi Paul Rajib Biswas Gunjan Saikia 《International Journal of Communication Systems》2021,34(1):e4669
We report here the development of two computational tools PCFPS (Photonic Crystal Fiber Parameter Study) and PCFPA (Photonic Crystal Fiber Parameter Analysis), equipped with graphical user interface (GUI) for modeling of photonic crystal fiber. The tools are based on different structural parameters, and they provide characteristic analysis of the modal parameters from the structural parameters. The main feature of PCFPS is that it enables the user to find out the values of each defining modal parameter that has an immense contribution towards the manufacture of photonic crystal fiber. Additionally, PCFPA allows the user to observe the variation in the modal parameters with respect to the changes in structural parameters (such as d, Λ, d/Λ, and λ/>Λ). Besides their ease of use, these two schemes have high computational precision and adaptability, giving a novel platform to optical engineers to modulate the microstructured fibers according to their requirement. 相似文献
10.
Malachite nanoparticles of 100-150 nm have been efficiently and for the first time used as an adsorbent for the removal of toxic arsenate and chromate. We report a high adsorption capacity for chromate and arsenate on malachite nanoparticle from both individual and mixed solution in pH ~4-5. However, the adsorption efficiency decreases with the increase of solution pH. Batch studies revealed that initial pH, temperature, malachite nanoparticles dose and initial concentration of chromate and arsenate were important parameters for the adsorption process. Thermodynamic analysis showed that adsorption of chromate and arsenate on malachite nanoparticles is endothermic and spontaneous. The adsorption of these anions has also been investigated quantitatively with the help of adsorption kinetics, isotherm, and selectivity coefficient (K) analysis. The adsorption data for both chromate and arsenate were fitted well in Langmuir isotherm and preferentially followed the second order kinetics. The binding affinity of chromate is found to be slightly higher than arsenate in a competitive adsorption process which leads to the comparatively higher adsorption of chromate on malachite nanoparticles surface. 相似文献