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81.
Stubbins A Hubbard V Uher G Law CS Upstill-Goddard RC Aiken GR Mopper K 《Environmental science & technology》2008,42(9):3271-3276
Aqueous solutions of humic substances (HSs) and pure monomeric aromatics were irradiated to investigate the chemical controls upon carbon monoxide (CO) photoproduction from dissolved organic matter (DOM). HSs were isolated from lakes, rivers, marsh, and ocean. Inclusion of humic, fulvic, hydrophobic organic, and hydrophilic organic acid fractions from these environments provided samples diverse in source and isolation protocol. In spite of these major differences, HS absorption coefficients (a) and photoreactivities (a bleaching and CO production) were strongly dependent upon HS aromaticity (r2 > 0.90; n = 11), implying aromatic moieties are the principal chromophores and photoreactants within HSs, and by extension, DOM. Carbonyl carbon and CO photoproduction were not correlated, implying that carbonyl moieties are not quantitatively important in CO photoproduction. CO photoproduction efficiency of aqueous solutions of monomeric aromatic compounds that are common constituents of organic matter varied with the nature of ring substituents. Specifically, electron donating groups increased, while electron withdrawing groups decreased CO photoproductivity, supporting our conclusion that carbonyl substituents are not quantitatively important in CO photoproduction. Significantly, aromatic CO photoproduction efficiency spanned 3 orders of magnitude, indicating that variations in the CO apparent quantum yields of natural DOM may be related to variations in aromatic DOM substituent group chemistry. 相似文献
82.
Jacek Mochowski Miroslaw Giurg Michal Uher Anna Korenova Daniel Vegh 《Advanced Synthesis \u0026amp; Catalysis》1996,338(1):65-68
It has been revealed that N,N-dimethylhydrazones ( 1a - c , 3a , b ) derived from kojic acid analogs, such as substituted furans ( 3a , b ), 4-pyrones ( 1a , b ) and 4-pyridine ( 1c ), on oxididation with 3-chloroperoxybenzoic acid afford the corresponding nitriles ( 2a-c , 4a , b ). The method has preparative value. The mechanism of the reaction is presented. 相似文献
83.
High Strength Conductive Composites with Plasmonic Nanoparticles Aligned on Aramid Nanofibers
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Jing Lyu Xinzhi Wang Lehao Liu Yoonseob Kim Ekembu K. Tanyi Hang Chi Wenchun Feng Lizhi Xu Tiehu Li Mikhail A. Noginov Ctirad Uher Mark D. Hammig Nicholas A. Kotov 《Advanced functional materials》2016,26(46):8435-8445
Rapidly evolving fields of biomedical, energy, and (opto)electronic devices bring forward the need for deformable conductors with constantly rising benchmarks for mechanical properties and electronic conductivity. The search for conductors with improved strength and strain have inspired the multiple studies of nanocomposites and amorphous metals. However, finding conductors that defy the boundaries of classical materials and exhibit simultaneously high strength, toughness, and fast charge transport while enabling their scalable production, remains a difficult materials engineering challenge. Here, composites made from aramid nanofibers (ANFs) and gold nanoparticles (Au NPs) that offer a new toolset for engineering high strength flexible conductors are described. ANFs are derived from Kevlar macrofibers and retain their strong mechanical properties and temperature resilience. Au NPs are infiltrated into a porous, free‐standing aramid matrix, becoming aligned on ANFs, which reduces the charge percolation threshold and facilitates charge transport. Further thermal annealing at 300 °C results in the Au‐ANF composites with an electrical conductivity of 1.25 × 104 S cm?1 combined with a tensile strength of 96 MPa, a Young's modulus of 5.29 GPa, and a toughness of 1.3 MJ m?3. These parameters exceed those of most of the composite materials, and are comparable to those of amorphous metals but have no volume limitations. The plasmonic optical frequencies characteristic for constituent NPs are present in the composites with ANFs enabling plasmon‐based optoelectronic applications. 相似文献
84.
85.
K Loughney TR Hill VA Florio L Uher GJ Rosman SL Wolda BA Jones ML Howard LM McAllister-Lucas WK Sonnenburg SH Francis JD Corbin JA Beavo K Ferguson 《Canadian Metallurgical Quarterly》1998,216(1):139-147
An attempt has been made to suppress the ethanol-induced formation of megamitochondria (MG) in the rat liver by 4-hydroxy-2,2,6,6-tetramethyl-piperidine-1-oxyl (4-OH-TEMPO), a free radical scavenger, and by allopurinol (AP), a xanthine oxidase inhibitor. Changes observed in the liver of animals given ethanol (EtOH) for 1 month were remarkable decreases both in the body weight gains during the course of the experiment and in the liver weight at the time of sacrifice compared to those of the control; remarkable increases in the level of thiobarbituric acid reactive substances and lipid soluble fluorophores both in microsomes and mitochondria; decreases in the content of cytochrome a+a3 and b and lowered phosphorylating ability of mitochondria; and formation of MG in the liver. A combined treatment of animals with EtOH plus 4-OH-TEMPO completely suppressed the formation of MG in the liver induced by EtOH and distinctly improved the changes caused by EtOH, as specified above, while AP partly suppressed the MG formation. Results described herein provide additional insight into chronic hepatotoxicity of EtOH besides that previously reported. A novelty of the present work is that we were able for the first time to demonstrate reversibility of EtOH-mediated ultrastructural changes of the liver by a simple administration of aminoxyl-type free radical scavenger, 4-OH-TEMPO. Our results suggest that free radicals may be involved in the mechanism of the formation of MG induced by EtOH. 相似文献
86.
Pavel Uher 《Tunnelling and Underground Space Technology incorporating Trenchless Technology Research》1987,2(3)
An underground sewage treatment plant in Pec pod Sněžkou is the first facility of its kind to be designed and constructed in Czechoslovakia. The underground alternative was selected owing both to environmental concerns and the promising geology of the proposed site. In addition to discussing the design and construction of the plant, the author includes technical and economic data for the project. 相似文献
87.
Liu H Shi X Xu F Zhang L Zhang W Chen L Li Q Uher C Day T Snyder GJ 《Nature materials》2012,11(5):422-425
Advanced thermoelectric technology offers a potential for converting waste industrial heat into useful electricity, and an emission-free method for solid state cooling. Worldwide efforts to find materials with thermoelectric figure of merit, zT values significantly above unity, are frequently focused on crystalline semiconductors with low thermal conductivity. Here we report on Cu(2-x)Se, which reaches a zT of 1.5 at 1,000 K, among the highest values for any bulk materials. Whereas the Se atoms in Cu(2-x)Se form a rigid face-centred cubic lattice, providing a crystalline pathway for semiconducting electrons (or more precisely holes), the copper ions are highly disordered around the Se sublattice and are superionic with liquid-like mobility. This extraordinary 'liquid-like' behaviour of copper ions around a crystalline sublattice of Se in Cu(2-x)Se results in an intrinsically very low lattice thermal conductivity which enables high zT in this otherwise simple semiconductor. This unusual combination of properties leads to an ideal thermoelectric material. The results indicate a new strategy and direction for high-efficiency thermoelectric materials by exploring systems where there exists a crystalline sublattice for electronic conduction surrounded by liquid-like ions. 相似文献
88.
89.
J Szebeni K Barna F Uher J Milosevits K Pálóczi D Gaál GG Petrányi E Kelemen 《Canadian Metallurgical Quarterly》1997,11(10):1769-1774
8-Carbamoyl-3-methylimidazo(5,1-d)-1,2,3,5-tetrazin-4(3H)-one (temozolomide) is a new imidazole tetrazinone compound with promising preclinical and clinical activity in nitrosourea-sensitive and -resistant models and manageable toxicity in Phase I and II clinical trials. In this study, we investigated the antiproliferative activity of temozolomide against a large variety of human tumors taken directly from patients in an in vitro soft agar tumor cloning system. Temozolomide was studied using a continuous exposure at final concentrations from 0.1 to 10.0 microM against a total of 222 tumor specimens, of which 101 (45%) were evaluable. A decrease in tumor colony formation was considered significant if survival of colonies treated with temozolomide was =50% of that in controls. In vitro responses were seen in 9 of 101 [9%; 95% confidence interval (CI), 3-14], 16 of 100 (16%; 95% CI, 8. 5-23), and 35 of 101 (35%; 95% CI, 26-45) tumor specimens at concentrations of 0.1, 1.0, and 10.0 microM, respectively (P < 0. 001). The level of O6-guanine-alkyl-transferase was evaluable in 19 specimens before treatment but did not correlate with a response to temozolomide. At a concentration of 10 microM, a good cytotoxic activity was seen in breast (42%; 95% CI, 15-72), ovarian (36%; 95% CI, 11-69), and non-small cell lung cancers (27%; 95% CI, 6-61). Interestingly, activity was also seen in renal cell carcinomas (50%; 95% CI, 19-81), colon cancers (42%; 95% CI, 15-72), melanomas (33%; 95% CI, 13-59), and some other tumors, including sarcomas and both prostatic and pancreatic carcinomas that are usually considered very resistant to several conventional chemotherapy agents. Moreover, we observed that a subset of tumors that were not sensitive to dacarbazine, carmustine, cisplatin, doxorubicin, 5-fluorouracil, etoposide, and vinblastine were sensitive to temozolomide. These data indicate both that temozolomide is an active drug in vitro against a large variety of human tumors, including some tumors usually resistant to conventional chemotherapy, and that further clinical evaluation is warranted. 相似文献
90.
Electric power systems for guided vehicles with speeds above 200 mi/h were investigated. Particular attention was paid to a high-speed steel wheel-driven train which has a cruise capability of 200 mi/h. Alternate propulsion, power conditioning, and power distribution systems were evaluated, and economically acceptable solutions were highlighted. The conclusion is that 25-kV single-phase ac distribution together with a vehicle propelled with dc motors, driven by a controlled rectifier, shows most promise for the near future. AC drives could be attractive candidates in five to ten years, with 25-kV 60-Hz power distributed along the wayside. However, with ac drives, there is strong incentive to distribute power using 15-kV dc if the switching could be developed. 相似文献