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31.
Hayet Ben Khaled Ali Bougatef Rafik Balti Yosra Triki‐Ellouz Nabil Souissi Moncef Nasri 《Journal of the science of food and agriculture》2008,88(15):2654-2662
BACKGROUND: In Tunisia, sardinelle (Sardinella aurita) catches totalled about 13 300 t in 2002. During processing, solid wastes including heads and viscera are generated, representing about 30% of the original raw material. Viscera, one of the most important by‐products of the fishing industry, are recognised as a potential source of digestive enzymes, especially proteases with high activity over a wide range of pH and temperature conditions. This paper describes the purification procedure and some biochemical characterisation of trypsin from S. aurita viscera. RESULTS: Trypsin from the viscera of sardinelle (S. aurita) was purified by fractionation with ammonium sulphate, Sephadex G‐75 gel filtration, Sepharose mono Q anion exchange chromatography, ultrafiltration and a second Sephadex G‐75 gel filtration, resulting in a 5.42‐fold increase in specific activity and 6.1% recovery. The molecular weight of the purified enzyme was estimated to be 24 kDa using size exclusion chromatography and sodium dodecyl sulfate polyacrylamide gel electrophoresis. The purified enzyme showed esterase‐specific activity on N‐α‐benzoyl‐L ‐arginine ethyl ester (BAEE) that was four times greater than its amidase‐specific activity on N‐α‐benzoyl‐DL ‐arginine‐p‐nitroanilide (BAPNA). The optimal pH and temperature for enzyme activity were pH 8 and 55 °C respectively using BAEE as a substrate. The trypsin kinetic constants Km and kcat on BAPNA were 1.67 mmol L?1 and 3.87 s?1 respectively, while the catalytic efficiency kcat/Km was 2.31 s?1 L mmol?1. CONCLUSION: Trypsin was purified from sardinelle (S. aurita) viscera. Biochemical characterisation of S. aurita trypsin showed that this enzyme can be used as a possible biotechnological tool in the fish‐processing and food industries. Copyright © 2008 Society of Chemical Industry 相似文献
32.
Mohamed Ben Abdelhamid Chaker Aloui Corinne Chaton Jomâa Souissi 《Journal of Fusion Energy》2010,29(2):202-207
This paper applies real options and mean–variance portfolio theories to analyze the electricity generation planning into presence
of nuclear power plant for the Tunisian case. First, we analyze the choice between fossil fuel and nuclear production. A dynamic
model is presented to illustrate the impact of fossil fuel cost uncertainty on the optimal timing to switch from gas to nuclear.
Next, we use the portfolio theory to manage risk of the electricity generation portfolio and to determine the optimal fuel
mix with the nuclear alternative. Based on portfolio theory, the results show that there is other optimal mix than the mix
fixed for the Tunisian mix for the horizon 2010–2020, with lower cost for the same risk degree. In the presence of nuclear
technology, we found that the optimal generating portfolio must include 13% of nuclear power technology share. 相似文献
33.
Fatima Said Nébil Souissi Karima Es-Salah Najat Hajjaji Ezzeddine Triki Abdullah Srhiri 《Journal of Materials Science》2007,42(21):9070-9074
The inhibiting action of alkyltriphenylphosphonium iodine salt ((C8H17)Ph3P+,I−) towards the corrosion behaviour of nickel in 1 M H2SO4 solution has been studied. This compound was found to retard both anodic and cathodic reactions of nickel corrosion. At constant
temperature, the corrosion rate decreases with increasing inhibitor concentration. On the other hand, the increase in temperature
leads to an increase in the corrosion rate. The activation energy, ΔE
a, were calculated. They were found 19.3 kJ mol−1 and 71.1 kJ mol−1, respectively for the uninhibited solution and in the presence of 10−3 M of phosphonium salt. The inhibitor adsorption was identified to occur according to Langmuir isotherm. The equilibrium constant,
k, as well as the free energy of adsorption, Δads
G°, for inhibitor process were then calculated. Phosphonium iodine exhibited a singular behaviour for T ≥ 318 K where inhibitor desorption increases. 相似文献
34.
The present study describes the chemical composition, and antimicrobial, antioxidant and angiotensin I-converting enzyme (ACE) inhibitory activities of essential oil from Periploca laevigata root barks (PLRB), an aromatic plant widely distributed in Tunisia and used as a traditional medicinal plant. Gas chromatography/mass spectrometry was used to determine the composition of the PLRB oil. Forty-three components were identified in the essential oil and the main compounds were benzaldehyde (56%), methyl 4-methoxysalicylate (6.55%) and carvacrol (4.75%). The PLRB essential oil exhibited a dose-dependent manner of inhibitory activity toward ACE. The highest ACE inhibitory activity (54%) was observed at a concentration of 30 μg/ml. The PLRB oil was also found to possess antioxidant activities, as evaluated by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical method, β-carotene bleaching and reducing power assays. The antimicrobial activity of the essential oil was also investigated on several microorganisms. The inhibition zones and minimal inhibitory concentration (MIC) values of bacterial strains were in the range of 12–46 mm and 50–300 μg/ml, respectively. The inhibitory activity of the PLRB essential oil against Gram-positive bacteria was significantly higher than against Gram-negative. It also exhibited remarkable activity against several fungal strains. 相似文献
35.
36.
This paper establishes a comparison between the interface exhibited by an archaeological bronze alloy when previously submitted to a burial environment and a chloride electrolyte. The SEM‐EDAX analysis shows that the archaeological surface exhibited a three layered structure characterized by a tin enrichment at the inner layer, the succeeding layer being only by copper species, the outer layer is relevant of the burial environment. This corrosion structure is to be regarded as Type I morphology described in the literature for bronzes exhumed in the northern side of the Mediterranean Sea. When submitted to chloride solution, the open circuit potential of material tends to constant values after five days of immersion time. The evolution of the resulting interface was characterized using EIS and the spectra obtained were tentatively fitted using a simple electrical equivalent circuit. When, the interface attained the steady state, the interface shows a patina with two layered morphology similar to the archaeological one. 相似文献
37.
38.
Résumé Pour étudier le problème du diffuseur d'une turbine hydraulique, nous avons utilisé le lagrangien pour établir formellement
les équations adjointes et faire un calcul rapide du gradient de la fonctionnelle. En utilisant la dérivée particulaire, nous
avons calculé ce gradient permettant d'effectuer un déplacement de la frontière sans perte de régularité sur le domaine. L'application
d'une variante du théorème de Min-Max permet de se passer du théorème des fonctions implicites. Des résultats numériques étayant
la validité du modèle sont présentés. 相似文献
39.
Mathematical models were built to predict sodium phosphate inhibition of copper corrosion in aqueous chloride and sulphate media. SEM-EDXS and AFM were used to characterize material surfaces without and with inorganic salt addition. Inhibitor efficiency was compared with that exhibited by benzotriazole. 相似文献
40.
Ali Bougatef Rafik Balti Naïma Nedjar-Arroume Rozenn Ravallec Estelle Yaba Adjé Nabil Souissi Imen Lassoued Didier Guillochon Moncef Nasri 《European Food Research and Technology》2010,231(1):127-135
In this study, smooth hound protein hydrolysates (SHPHs), obtained by treatment with various gastrointestinal proteases, were
analyzed for their angiotensin I-converting enzyme (ACE) inhibitory activities. Protein hydrolysates were obtained by treatment
with crude alkaline enzyme extract, low molecular weight (LMW) alkaline protease, trypsin-like protease and pepsin from Mustelus mustelus, and bovine trypsin. All hydrolysates exhibited inhibitory activity toward ACE. Hydrolysate generated with alkaline protease
extract displayed the highest ACE inhibitory activity, and the higher inhibition activity (82.6% at 2 mg/mL) was obtained
with a hydrolysis degree of 18.8%. This hydrolysate was then fractionated by size exclusion chromatography on a Sephadex G-25
into five major fractions (P1–P5). ACE inhibitory activities of all fractions were assayed, and P3 was found to display a high ACE inhibitory activity (62.24% at 1 mg/mL). P3 was then fractionated by reversed-phase high-performance liquid chromatography (RP-HPLC) and ten fractions of ACE inhibitors
were found (F1–F10). Sub-fraction F3 showed the strongest ACE inhibitory activity, being able to suppress more than 60% of initial enzyme activity at a concentration
of 100 μg/mL. The amino acid sequence of peptide F3 was determined by ESI/MS and ESI–MS/MS as Ala-Gly-Ser, and the IC50 value for ACE inhibitory activity was 0.13 ± 0.03 mg/mL. Further, purified peptide F3 maintained inhibitory activity even after in vitro digestion with gastrointestinal proteases in order to demonstrate gastrointestinal
stability digestion to enable oral application. These results indicate that smooth hound protein hydrolysate possesses potent
antihypertensive activity. 相似文献