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51.
Elsie Araujo Juan Manuel Martínez-Huerta Luc Piraux Armando Encinas 《Journal of Superconductivity and Novel Magnetism》2018,31(12):3981-3987
A method is presented that allows quantifying the average value of the interaction field in arrays of magnetic nanowires from the field difference between the isothermal remanence (IRM) and the DC demagnetizing (DCD) remanence curves when the normalized magnetization is equal to one third. Arrays of magnetic nanowires of different diameters and packing fractions are used to experimentally test the method. The results have been compared with those obtained using the method based on the difference between the remanence coercivity fields and with a mean-field expression for the interaction field, providing a very good agreement and thus validating the method. Additionally, it is shown that both the position (m0) and the shift along the magnetization axis of the intersection between the remanence curves with respect to the value of one third (δm = m0 ??1/3) provide qualitative information about the interaction field. The former indicates the type of interaction depending if the intersection is above (m0 >?1/3) or below (m0 <?1/3), which corresponds to a ferro or anti-ferro magnetic interaction, respectively. While for the latter, it is shown that the maximum deviation of the Delta-M plot from zero (ΔMmax) corresponds to three times the shift (ΔMmax =?3δm). 相似文献
52.
David A. Quansah Muyiwa S. Adaramola Emmanuel K. Anto 《Clean Technologies and Environmental Policy》2017,19(10):2431-2442
Driven by improvements in solar photovoltaic (PV) technology, policy initiatives and module cost reduction, electricity from solar PV is becoming increasingly cost-competitive with conventional energy systems. In this paper, an economic assessment is conducted on a 4.05 kWp, polycrystalline silicon photovoltaic system installed at the College of Engineering of the Kwame Nkrumah University of Science and Technology, Kumasi, Ghana, located at latitude 6°40′N and longitude 1°37′W, and elevation of 250 m, with a hot and humid climatic condition. The concept of grid-parity, which compares the levelized cost of electricity (LCOE) from solar PV to the retail price of electricity is used in this assessment. The results show, that, at installed cost of €3567/kW and an LCOE of €0.28/kWh, the non-residential category of electricity consumers requires investment support/subsidy of up to 22.9% to achieve parity. Solar PV is already competitive for non-residential customers consuming above 600 kWh in a month, without any support. Residential electricity consumers require investment support of 40.6–92.5% to attain parity with grid electricity, while special load tariff customers (> 100 kVA maximum demand) require between 4 and 50.5% subsidy on capital investment to reach parity. This paper concludes by recommending a two-pronged approach (incentive- and legislation-based) for promoting distributed grid-connected solar PV energy system in Ghana. 相似文献
53.
Dimitrios Bitounis Dorsa Parviz Xiaoqiong Cao Carlo A. Amadei Chad D. Vecitis Elsie M. Sunderland Brian D. Thrall Mingliang Fang Michael S. Strano Philip Demokritou 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(21)
In the last decade, along with the increasing use of graphene oxide (GO) in various applications, there is also considerable interest in understanding its effects on human health. Only a few experimental approaches can simulate common routes of exposure, such as ingestion, due to the inherent complexity of the digestive tract. This study presents the synthesis of size‐sorted GO of sub‐micrometer‐ or micrometer‐sized lateral dimensions, its physicochemical transformations across mouth, gastric, and small intestinal simulated digestions, and its toxicological assessment against a physiologically relevant, in vitro cellular model of the human intestinal epithelium. Results from real‐time characterization of the simulated digestas of the gastrointestinal tract using multi‐angle laser diffraction and field‐emission scanning electron microscopy show that GO agglomerates in the gastric and small intestinal phase. Extensive morphological changes, such as folding, are also observed on GO following simulated digestion. Furthermore, X‐ray photoelectron spectroscopy reveals that GO presents covalently bound N‐containing groups on its surface. It is shown that the GO employed in this study undergoes reduction. Toxicological assessment of the GO small intestinal digesta over 24 h does not point to acute cytotoxicity, and examination of the intestinal epithelium under electron microscopy does not reveal histological alterations. Both sub‐micrometer‐ and micrometer‐sized GO variants elicit a 20% statistically significant increase in reactive oxygen species generation compared to the untreated control after a 6 h exposure. 相似文献
54.
Afua Adwubi Bright Kofi Amegashie Wilson Agyei Agyare Lulseged Tamene Samuel Nii Odai Charles Quansah Paul Vlek 《Lakes & Reservoirs: Research and Management》2009,14(4):279-287
Many small dams and dugouts have been constructed in the Upper East Region of Ghana to address the problem of regional water scarcity. The reservoirs were constructed primarily as water supplies for agricultural irrigation and livestock watering, aquaculture and domestic use. However, many of the reservoirs dry up during the dry season, affecting the livelihoods of their basin inhabitants. A major cause for the dried reservoirs is siltation, which reduces the reservoir’s storage capacities. The goal of this study is to quantify the annual siltation rate of four study reservoirs, using a bathymetric survey and reservoir soil sampling. The sediment yield and its relation to catchment area also were assessed. The results of this study indicate that the annual siltation rates are 1272, 3518, 2764 and 6135 t year?1 for Doba, Dua, Zebilla and Kumpalgogo reservoirs, respectively. Analyses of the sediment yield and catchment areas illustrated that the sediment yields decreased with increasing catchment area. All the study reservoirs have lost their dead storage capacity, which was meant to store sediment until the end of their anticipated design lives. The decreasing storage capacity because of siltation will affect the livelihoods of the local basin inhabitants, as the reservoirs will not be able to achieve all their intended purposes. The results of this study indicate that, because siltation is not the only factor threatening the benefits gained from the reservoirs, the integrated assessment of all relevant factors is required. 相似文献
55.
Hesham M. Tawfeek Sayed H. Khidr Eman M. Samy Sayed M. Ahmed Elsie E. Gaskell 《Drug development and industrial pharmacy》2014,40(9):1213-1222
Poly(glycerol adipate-co-ω-pentadecalactone) (PGA-co-PDL) was previously evaluated for the colloidal delivery of α-chymotrypsin. In this article, the effect of varying polymer molecular weight (MW) and chemistry on particle size and morphology; encapsulation efficiency; in vitro release; and the biological activity of α-chymotrypsin (α-CH) and lysozyme (LS) were investigated. Microparticles were prepared using emulsion solvent evaporation and evaluated by various methods. Altering the MW or monomer ratio of PGA-co-PDL did not significantly affect the encapsulation efficiency and overall poly(1,3-propanediol adipate-co-ω-pentadecalactone) (PPA-co-PDL) demonstrated the highest encapsulation efficiency. In vitro release varied between polymers, and the burst release for α-CH-loaded microparticles was lower when a higher MW PGA-co-PDL or more hydrophobic PPA-co-PDL was used. The results suggest that, although these co-polyesters could be useful for protein delivery, little difference was observed between the different PGA-co-PDL polymers and PPA-co-PDL generally provided a higher encapsulation and slower release of enzyme than the other polymers tested. 相似文献
56.
59.
Previous work has shown that the intermediates in the formation of resins from phenol and formaldehyde— the 2,2′-, 2,4′- and 4,4′-dihydroxydiphenylmethanes can only be isolated from the reaction products in small yields and with difficulty. It is now shown that after distillation of excess phenol and formaldehyde from the initial reaction mass at atmospheric pressure, a further high-temperature steam distillation yields approximately 60% of the remaining product as white crystalline dihydroxydiphenylmethanes, 20% as triphenylols varying from hard crystalline masses to slowly crystallising oils, and 20% of fusible and soluble novolac resin of high melting point. Some lens-shaped crystals were also obtained. 相似文献
60.
Streets DG Devane MK Lu Z Bond TC Sunderland EM Jacob DJ 《Environmental science & technology》2011,45(24):10485-10491
Understanding the biogeochemical cycling of mercury is critical for explaining the presence of mercury in remote regions of the world, such as the Arctic and the Himalayas, as well as local concentrations. While we have good knowledge of present-day fluxes of mercury to the atmosphere, we have little knowledge of what emission levels were like in the past. Here we develop a trend of anthropogenic emissions of mercury to the atmosphere from 1850 to 2008-for which relatively complete data are available-and supplement that trend with an estimate of anthropogenic emissions prior to 1850. Global mercury emissions peaked in 1890 at 2600 Mg yr(-1), fell to 700-800 Mg yr(-1) in the interwar years, then rose steadily after 1950 to present-day levels of 2000 Mg yr(-1). Our estimate for total mercury emissions from human activities over all time is 350 Gg, of which 39% was emitted before 1850 and 61% after 1850. Using an eight-compartment global box-model of mercury biogeochemical cycling, we show that these emission trends successfully reproduce present-day atmospheric enrichment in mercury. 相似文献