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Measurements of area porosity in layered beds by a technique utilizing the pressure of liquid head measurement. Processing of the area porosity profiles in “interfacial” regions between layers of coke and agglomerate to obtain the coefficients for the calculation of the excess pressure drop in these regions. A comparison of results with earlier data for layers of monodisperse spheres. 相似文献
23.
The kinetics of hydration of five C2SS cements at 0.83C/S were studied at 175 to 300°C. CSH(I) formed as the initial hydration phase in four cements and tobermorite in the other. Amounts of 1.32 and 1.74% CO2 in two cements caused total replacement of xonotlite by scawtite, while 0.34 and 0. 37 CO2 yielded negligible amounts of scawtite (if any). The equilibrium products in the two cements were scawtite and gyrolite at 175 and 200°C and scawtite and truscottite at 250 and 300°C. 相似文献
24.
Catalytic efficiency, stability and environmental applicability of five iron(III) oxide nanopowders differing in surface area and crystallinity were tested in degradation of concentrated phenolic aqueous solutions (100 g/L) at mild temperature (30 °C), initially almost neutral pH and equimolar ratio of hydrogen peroxide and phenol. The catalyst properties were easily controlled by varying in reaction time during isothermal treatment of ferrous oxalate dihydrate in air at 175 °C. Although the catalytic efficiency clearly increases with the surface area of the nanopowders, it is not due to the solely heterogeneous catalytic mechanism as would be expected. The amorphous Fe2O3 nanopowders possessing the largest surface areas (401 m2 g−1, 386 m2 g−1) are the most efficient catalysts evidently due to their highest susceptibility to leaching in acidic environment arising as a consequence of phenol degradation products. Thus, these amorphous samples act partially as homogeneous catalysts, which was confirmed by a high concentration of leached Fe(III) ions in the solution (19 ppm). The crystalline hematite (α-Fe2O3) samples, varying in surface area between 337 m2 g−1 and 245 m2 g−1, are generally less efficient when compared to the amorphous powders, however their catalytic action is almost exclusively heterogeneous as only 3 ppm of leached Fe(III) was found in the reaction systems catalyzed by nanohematite samples. A significant difference in relative contributions of heterogeneous and homogenous catalysis was definitely established in buffered reaction systems catalyzed by amorphous Fe2O3 and nanocrystalline hematite. The nanohematite sample exhibiting the highest heterogeneous action was tested at decreased initial phenol concentration (10 g/L), which is closer to the real contents of phenol in waste waters, and at different hydrogen peroxide/phenol molar ratios to consider its environmental applicability. At the hydrogen peroxide/phenol ratio equal to 5, no traces of the leached iron were detected and the phenol conversion of 84% was reached. Moreover, such a high degree of conversion is accompanied by a decrease of the chemical oxygen demand (COD) from the initial value of 11.23 g/L to 4.22 g/L after 125 min. This fact indicates that the considerable fraction of primary reaction products was totally degraded. 相似文献
25.
The extraction of indium from a synthetic sulfate‐containing solution using commercial reagents (Cyanex 272, DEHPA, and Cyanex 923) is evaluated on a comparative basis. The extraction profiles of indium (III) were examined with regard to the reagent concentration, the pH value of the aqueous solution, and the indium concentration in a low phase ratio of 1:10. DEHPA and Cyanex 272 are, in contrast to Cyanex 923, very well suited for the extraction of indium. Re‐extraction with HCl and H2SO4 is compared. 相似文献
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27.
Kolleboyina Jayaramulu Deepak P. Dubal Andreas Schneemann Vclav Ranc Cecilia Perez‐Reyes Jana Strsk tpn Kment Michal Otyepka Roland A. Fischer Radek Zboil 《Advanced functional materials》2019,29(38)
Herein, a novel polymer‐templated strategy is described to obtain 2D nickel‐based MOF nanosheets using Ni(OH)2, squaric acid, and polyvinylpyrrolidone (PVP), where PVP has a dual role as a structure‐directing agent, as well as preventing agglomeration of the MOF nanosheets. Furthermore, a scalable method is developed to transform the 2D MOF sheets to Ni7S6/graphene nanosheet (GNS) heterobilayers by in situ sulfidation using thiourea as a sulfur source. The Ni7S6/GNS composite shows an excellent reversible capacity of 1010 mAh g?1 at 0.12 A g?1 with a Coulombic efficiency of 98% capacity retention. The electrochemical performance of the Ni7S6/GNS composite is superior not only to nickel sulfide/graphene‐based composites but also to other metal disulfide–based composite electrodes. Moreover, the Ni7S6/GNS anode exhibits excellent cycle stability (≈95% capacity retention after 2000 cycles). This outstanding electrochemical performance can be attributed to the synergistic effects of Ni7S6 and GNS, where GNS serves as a conducting matrix to support Ni7S6 nanosheets while Ni7S6 prevents restacking of GNS. This work opens up new opportunities in the design of novel functional heterostructures by hybridizing 2D MOF nanosheets with other 2D nanomaterials for electrochemical energy storage/conversion applications. 相似文献
28.
Smita V. Talande Aristides Bakandritsos Petr Jakubec Ondej Malina Radek Zboil Jii Tu
ek 《Advanced functional materials》2019,29(51)
Supercapacitors are a promising energy storage technology owing to their unparalleled power and lifetime. However, to meet the continuously rising demands of energy storage, they must be equipped with higher energy densities. For this purpose, the seamless integration of metal oxides on carbon matrices, such as iron oxides/oxyhydroxides, has been pursued through hydrothermal, atomic layer and electro‐deposition methods directly on current collectors. Nevertheless, such methods present limited compatibility with commercial paste‐coating processes on the current collectors. Furthermore, iron oxides/oxyhydroxides lack conductivity and are hydrophilic, operating with low‐voltage aqueous electrolytes, limiting their power and energy and requiring corrosion‐resistant H2O current collectors. To mitigate these challenges, a seamless and paste‐ready material is successfully developed through a 15 min wet‐chemical method, via the coordination of ultrasmall β‐FeOOH (akaganéite) nanoparticles to the nitrile groups of a covalent graphene derivative. Endowed with graphene‐like impedance response and very high wettability in organic electrolytes, combined high power and energy densities are obtained, with respect to the total mass of both electrode materials and current collectors, overcoming the identified challenges. This offers future prospects for the exploration of alternative molecular handles for improved interfaces and their application in different energy‐storage chemistries. 相似文献
29.
Tomáš Suchý Monika Šupová Martin Bartoš Radek Sedláček Marco Piola Monica Soncini Gianfranco Beniamino Fiore Pavla Sauerová Marie Hubálek Kalbáčová 《Journal of materials science. Materials in medicine》2018,29(2):20
Collagen composite scaffolds have been used for a number of studies in tissue engineering. The hydration of such highly porous and hydrophilic structures may influence mechanical behaviour and porosity due to swelling. The differences in physical properties following hydration would represent a significant limiting factor for the seeding, growth and differentiation of cells in vitro and the overall applicability of such hydrophilic materials in vivo. Scaffolds based on collagen matrix, poly(DL-lactide) nanofibers, calcium phosphate particles and sodium hyaluronate with 8 different material compositions were characterised in the dry and hydrated states using X-ray microcomputed tomography, compression tests, hydraulic permeability measurement, degradation tests and infrared spectrometry. Hydration, simulating the conditions of cell seeding and cultivation up to 48?h and 576?h, was found to exert a minor effect on the morphological parameters and permeability. Conversely, hydration had a major statistically significant effect on the mechanical behaviour of all the tested scaffolds. The elastic modulus and compressive strength of all the scaffolds decreased by ~95%. The quantitative results provided confirm the importance of analysing scaffolds in the hydrated rather than the dry state since the former more precisely simulates the real environment for which such materials are designed. 相似文献
30.
High‐Performance Supercapacitors Based on a Zwitterionic Network of Covalently Functionalized Graphene with Iron Tetraaminophthalocyanine 下载免费PDF全文
Aristides Bakandritsos Demetrios D. Chronopoulos Petr Jakubec Martin Pykal Klára Čépe Theodore Steriotis Sergii Kalytchuk Martin Petr Radek Zbořil Michal Otyepka 《Advanced functional materials》2018,28(29)
Graphene derivatives are promising candidates as electrode materials in supercapacitor cells, therefore, functionalization strategies are pursued to improve their performance. A scalable approach is reported for preparing a covalently and homogenously functionalized graphene with iron tetraaminophthalocyanine (FePc‐NH2) with a high degree of functionalization. This is achieved by exploiting fluorographene's reactivity with the diethyl bromomalonate, producing graphene‐dicarboxylic acid after hydrolysis, which is conjugated with FePc‐NH2. The material exhibits an ultrahigh gravimetric specific capacitance of 960 F g?1 at 1 A g?1 and zero losses upon charging–discharging cycling. The energy density of 59 Wh kg?1 is eminent among supercapacitors operating in aqueous electrolytes with graphene‐based electrode materials. This is attributed to the structural and functional synergy of the covalently bound components, giving rise to a zwitterionic surface with extensive π–π stacking, but not graphene restacking, all being very beneficial for charge and ionic transport. The safety of the proposed system, owing to the benign Na2SO4 aqueous electrolyte, the high capacitance, energy density, and potential of preparing the electrode material on a large‐scale and at low cost make the reported strategy very attractive for development of supercapacitors based on the covalent attachment of suitable molecules onto graphene toward high‐synergy hybrids. 相似文献