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41.
Andrensek S Simonovska B Vovk I Fyhrquist P Vuorela H Vuorela P 《International journal of food microbiology》2004,92(2):181-187
The multifunctional ExtraChrom instrument was used in the extraction of antimicrobial and radical scavenging components from oak (Quercus robur L.) bark. Milled and sieved oak bark was extracted with 80% (v/v) methanol solution in water on the ExtraChrom instrument using step-gradient in the preparative separation. Extracts were tested using agar diffusion method on Staphylococcus aureus, Enterobacter aerogenes and Candida albicans. Some extracts showed moderate bactericidal, fungicidal, bacteriostatic and fungistatic activity. The composition related to activity of the fractions and extracts was screened simultaneously by thin-layer chromatography (TLC) detected by UV and by spraying the plate with radical scavenging reagent 1,1-diphenyl-2-picrylhydrazyl (DPPH) to detect antioxidant activity. Thus, we could demonstrate the antiradical and antimicrobial activity of oak beneficial in the storage of wine against the oxidation and human microbial exposure. 相似文献
42.
St. John’s wort (Hypericum perforatum L.) herb is used as a herb-tea or as a food supplement because of its antidepressive properties. St. John’s wort, grown under different levels of UV-B radiation, was analysed for its concentrations of flavonoids, tannins and hypericin. A high level of UV-B radiation increased leaf concentrations of flavonoids from 6.31 to 9.00/100 g in dry matter (DM) and of tannins from 26.6 to 31.4/100 g in DM. The concentration of hypericin in leaves exposed to enhanced UV-B radiation (0.08/100 g in DM) was lower than that of leaves exposed to reduced UV-B radiation (0.09/100 g in DM). We conclude that the concentrations of bioactive substances in St. John’s wort herb can be altered by regulating the environment during plant growth. 相似文献
43.
A mechanistic study to provide diagnostics of anodic stripping electrode processes at bismuth-film electrodes is presented from both theoretical and experimental points of view. Theoretical models for three types of electrode mechanisms are developed under conditions of square-wave voltammetry, combining rigorous modeling based on integral equations and the step function method, resulting in derivation of a single numerical recurrent formula to predict the outcome of the voltammetric experiment. In the course of the deposition step, it has been assumed that a uniform film of the metal analyte is formed on the bismuth substrate, in situ deposited onto a glassy carbon electrode surface, without considering mass transfer within either the bismuth or the metal analyte film. Theoretical data are analyzed in terms of dimensionless critical parameters related with electrode kinetics, mass transfer, adsorption equilibria, and possible lateral interactions within the deposited metal particles. Theoretical analysis enables definition of simple criteria for differentiation and characterization of electrode processes. Comparing theoretical and experimental data, anodic stripping processes of zinc(II), cadmium(II), and lead(II) are successfully characterized, revealing significant differences in their reaction pathways. The proposed easy-to-perform diagnostic route is considered to be of a general use while the bismuth film exploited in this study served as a convenient nonmercury model substrate surface. 相似文献
44.
Tihomir Tomašić Nace Zidar Andreja Kovač Dr. Samo Turk Mihael Simčič Didier Blanot Dr. Manica Müller‐Premru Prof. Dr. Metka Filipič Prof. Dr. Simona Golič Grdadolnik Prof. Dr. Anamarija Zega Prof. Dr. Marko Anderluh Prof. Dr. Stanislav Gobec Prof. Dr. Danijel Kikelj Prof. Dr. Lucija Peterlin Mašič Prof. Dr. 《ChemMedChem》2010,5(2):286-295
Mur ligases participate in the intracellular path of bacterial peptidoglycan biosynthesis and constitute attractive, although so far underexploited, targets for antibacterial drug discovery. A series of hydroxy‐substituted 5‐benzylidenethiazolidin‐4‐ones were synthesized and tested as inhibitors of Mur ligases. The most potent compound 5 a was active against MurD–F with IC50 values between 2 and 6 μm, making it a promising multitarget inhibitor of Mur ligases. Antibacterial activity against different strains, inhibitory activity against protein kinases, mutagenicity and genotoxicity of 5 a were also investigated, and kinetic and NMR studies were conducted. 相似文献
45.
Due to the increasing number of traffic accidents involving the collisions of vehicles with the emergency-stop-area head walls in tunnels, a comparative numerical analysis in accordance with the EN 1317 standard has been performed in order to assess the quality of the available protective safety barriers. Based on the simulation results, the values of the relevant injury criteria – the acceleration severity index (ASI), the theoretical head impact velocity (THIV) and the post-impact head deceleration (PHD) – were computed for several collision scenarios involving two different passenger vehicles colliding with two different safety barriers in various ways. The results show that due to the geometrical restrictions in the tunnel's emergency stop area none of the barriers can provide total protection for the occupants of the vehicle in the event of a collision. The installation of a steel-sheet-tube crash cushion was, however, found to provide the best possible protection within the given limitations. The results of the analysis were the basis for selecting a safety-barrier design for existing tunnel installations and for the proposed changes in regulations governing the geometry of the tunnel's emergency stop area. 相似文献
46.
3.提高可靠性的方法可以系统提高整个寿命周期内技术系统可靠性的方法称为可靠性改进法,它包括以下主要步骤:A.评估设备可靠性情况。B.确定可靠性目标。C.引进提高可靠性的活动。D.进行评估。E.将评估结果与目标比较,制定后续措施。F.查出问题以及主要的造成不可靠性的原因。重复执行从步骤C到F,直到实现可靠性目标。设备的寿命周期可以粗略地分为如下阶段:方案和可行性、设计和研制、生产和使用。如果增加用于提高可靠性的费用,则对设备可靠性可能的不利影响会显著下降。3.1在使用阶段可靠性的提高大多数设备的可靠性是在使用阶段前定… 相似文献
47.
To investigate the heat removal capability of conceptual divertor cooling fingers, accurate computational fluid dynamics (CFD) analyses are indispensable. Although the cooling performance of the divertor finger has been successfully high-heat-flux tested under real DEMO conditions in a combined helium loop and electron beam facility at the Efremov Institute, Russia, an accompanying numerical simulation of the experiments is of great importance. This might help to better understand the complex thermo-hydraulic conditions with the aim of predicting other different load cases. To accurately reproduce the experimental boundary conditions, the Gaussian-like shape of the absorbed power was taken into account and the heat losses were estimated. Modeling of the structure thermal conductivity was also found to be an important source of modeling uncertainty. In the context of accurate modeling of experimental conditions, the effect of some modeling assumptions was evaluated. Transient simulations of the cyclic heat flux experiment were performed only for the solid part of the cooling finger to avoid excessively long computation times. The helium cooling was taken into account by the heat transfer coefficient (HTC) on the fluid–structure interface, obtained from the steady-state simulations of the full solid–fluid model. The HTC distribution did not vary with time throughout the entire transient simulation. The modeling error associated with such HTC approximation was estimated for the particular cyclic experiment. It is shown that the simulated temperature cycles on the top of experimental mock-up agree well with the measured data. 相似文献
48.
49.
Z. A. Samoĭlenko N. N. Belousov N. N. Ivakhnenko E. I. Pushenko 《Technical Physics Letters》2009,35(7):629-632
The structure of compacted Cu60Fe40 powder in various stages of thermomechanical processing (with a logarithmic strain varied within e = 0?7.4) has been studied by X-ray diffraction. It is established that the atomic order evolution in this system is characterized by a certain critical strain (e = 4.6), at which a specific deformation-induced nanostructure is formed. In this structure, clusters of a bcc α-Fe phase with dimensions on the order of 200 Å are coherently conjugated with a polycrystalline fcc structure of copper, thus representing a new class of materials. 相似文献
50.
Bismuth film electrodes (BiFEs) prepared ex situ with and without complexing bromide ions in the modification solution were investigated using scanning electrochemical microscopy (SECM) and atomic force microscopy (AFM). A feedback mode of the SECM was employed to examine the conductivity and reactivity of a series of thin bismuth films deposited onto disk glassy carbon substrate electrodes (GCEs) of 3 mm in diameter. A platinum micro-electrode (? = 25 μm) was used as the SECM tip, and current against tip/substrate distance was recorded in solutions containing either Ru(NH3)63+ or Fe(CN)64− species as redox mediators. With both redox mediators positive feedback approach curves were recorded, which indicated that the bismuth film deposition protocol associated with the addition of bromide ions in the modification solution did not compromise the conductivity of the bismuth film in comparison with that prepared without bromide. However, at the former Bi film a slight kinetic hindering was observed in recycling Ru(NH3)63+, suggesting a different surface potential. On the other hand, the approach curves recorded by using Fe(CN)64− showed that both types of the aforementioned bismuth films exhibited local reactivity with the oxidised form of the redox mediator, and that bismuth film obtained with bromide ions exhibited slightly lower reactivity. The use of SECM in the scanning operation mode allowed us to ascertain that the bismuth deposits were uniformly distributed across the whole surface of the glassy carbon substrate electrode. Comparative AFM measurements corroborated the above findings and additionally revealed a denser growth of smaller bismuth crystals over the surface of the substrate electrode in the presence of bromide ions, while the crystals were bigger but sparser in the absence of bromide ions in the modification solution. 相似文献