全文获取类型
收费全文 | 792篇 |
免费 | 74篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 4篇 |
化学工业 | 459篇 |
金属工艺 | 9篇 |
机械仪表 | 4篇 |
建筑科学 | 23篇 |
矿业工程 | 1篇 |
能源动力 | 18篇 |
轻工业 | 147篇 |
水利工程 | 2篇 |
无线电 | 46篇 |
一般工业技术 | 75篇 |
冶金工业 | 26篇 |
自动化技术 | 53篇 |
出版年
2024年 | 2篇 |
2023年 | 18篇 |
2022年 | 137篇 |
2021年 | 136篇 |
2020年 | 44篇 |
2019年 | 36篇 |
2018年 | 32篇 |
2017年 | 32篇 |
2016年 | 43篇 |
2015年 | 28篇 |
2014年 | 32篇 |
2013年 | 53篇 |
2012年 | 48篇 |
2011年 | 56篇 |
2010年 | 30篇 |
2009年 | 21篇 |
2008年 | 21篇 |
2007年 | 24篇 |
2006年 | 17篇 |
2005年 | 9篇 |
2004年 | 9篇 |
2003年 | 10篇 |
2002年 | 8篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
排序方式: 共有867条查询结果,搜索用时 15 毫秒
61.
Lukasz Drewniak Robert Stasiuk Witold Uhrynowski Aleksandra Sklodowska 《International journal of molecular sciences》2015,16(7):14409-14427
The purpose of this study was a detailed characterization of Shewanella sp. O23S, a strain involved in arsenic transformation in ancient gold mine waters contaminated with arsenic and other heavy metals. Physiological analysis of Shewanella sp. O23S showed that it is a facultative anaerobe, capable of growth using arsenate, thiosulfate, nitrate, iron or manganite as a terminal electron acceptor, and lactate or citrate as an electron donor. The strain can grow under anaerobic conditions and utilize arsenate in the respiratory process in a broad range of temperatures (10–37 °C), pH (4–8), salinity (0%–2%), and the presence of heavy metals (Cd, Co, Cr, Cu, Mn, Mo, Se, V and Zn). Under reductive conditions this strain can simultaneously use arsenate and thiosulfate as electron acceptors and produce yellow arsenic (III) sulfide (As2S3) precipitate. Simulation of As-removal from water containing arsenate (2.5 mM) and thiosulfate (5 mM) showed 82.5% efficiency after 21 days of incubation at room temperature. Based on the obtained results, we have proposed a model of a microbially mediated system for self-cleaning of mine waters contaminated with arsenic, in which Shewanella sp. O23S is the main driving agent. 相似文献
62.
63.
The properties of amphiphilic polyether macromonomers and their behaviour during homo-polymerisation in water and in water/benzene mixture are reported. Homo-poly(glycidol) macromonomer bearing polymerisable p-vinyl benzyl end groups (PGl55-St) and two block poly(glycidol)-b-poly(glycidyl phenyl ether) macromonomers, containing polymerisable p-vinyl benzyl end groups attached to the hydrophobic (PGl52-b-PGlPhE8-St) or hydrophilic (PGlPhE9-b-PGl54-St) block were used for investigations. DLS measurements showed formation of micelles by all macromonomers, what is the reason for enhanced homo-polymerisation. In water the polymerisation initiated with 4,4′-azobis(4-cyanovaleric acid) was fast, while macromonomer conversion was over 90%. Introduction of benzene to the polymerisation system resulted in formation of swollen (less packed) micelles and to a decrease of the local concentration of double bonds in the micelle core. As a result the decrease of reaction rate followed by longer polymerisation time in case of PGl55-St and PGl52-b-PGlPhE8-St was observed. Nevertheless, their conversion remained high and varied from 95 to 10. In contrast for PGlPhE9-b-PGl54-St increase of polymerisation rate, accompanied by slight increase of conversion was observed for homo-polymerisation in water/benzene mixture. 相似文献
64.
Safety aspects in modelling of batch and semibatch stirred tank reactors as well as a model based safety analysis have been considered. Applicability of two basic types of models – i.e. the perfectly mixed reactor model and the CFD model, both formulated for laboratory scale as well as pilot plant scale reactors – has been discussed. A formulation of the appropriate reactor model, which is adequate to the considered case study has been demonstrated and tested experimentally. Particular attention has been devoted to the formulation of robust CFD models employed to simulate a performance of the stirred tank reactors. It has been found that models for perfectly mixed reactors may have quite wide range of application, while the CFD models should be definitely used in case of fast reactions, high viscosity of the reacting mixture as well as of failure leading to stopping of the impeller. The CFD models are able to predict a dynamic behaviour of reactors at any circumstances, so they can play a significant role in safety analysis carried out for industrial scale reactors, for which experimental safety tests are expensive and dangerous. 相似文献
65.
66.
A method is described for converting chitosan into a high surface area and porous active carbon using a Na2CO3 solution impregnated into a partly depolymerized, protonated and water soaked chitosan. The wet chitosan paste is heat treated and transformed into a nonporous solid i.e. a carbon-rich matrix with uniformly suspended Na2CO3 nanocrystallites. Subsequent HCl etching opens cavities in the matrix due to the removal of the Na2CO3. The active carbon is high surface area (above 400 m2/g), microporous (below 1 nm) and nitrogen-rich (above 6% atomic). 相似文献
67.
Nemanja Miletić Randi Rohandi Zorica Vuković Aleksandra Nastasović Katja Loos 《Reactive and Functional Polymers》2009,69(1):68-75
Crosslinked macroporous hydrophilic poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) [abbreviated poly(GMA-co-EGDMA)] with identical chemical structure (60% of glycidyl methacrylate) but with varied average pore sizes (from 30 to 560 nm), specific surface areas (from 13.2 to 106.0 m2/g), specific volumes (from 0.755 to 1.191 cm3/g) and particle sizes (<100 μm–630 μm) were synthesized via suspension polymerization. Modifications of poly(GMA-co-EGDMA) with various diamines (1,2-diaminoethane, 1,4-diaminobutane, 1,6-diaminohexane and 1,8-diaminooctane), 2-fluoroethylamine, glutaraldehyde and cyanuric chloride were carried out. The influence of the interaction between Candida antarctica lipase B (Cal-B) and various carriers during immobilization on the loading and hydrolytic activity (hydrolysis of para-nitrophenyl acetate) of the immobilized Cal-B were studied. Immobilization of Cal-B was performed at different temperatures and pH values. Cal-B immobilized at 30 °C and pH 6.8 was leading to increased activities. Purely physical adsorption between enzyme and copolymer was observed on carriers in which amine or fluorine groups were introduced into the carrier structure by modification with various diamines or 2-fluoroethylamine. As a consequence enzyme loading and activity decreases. In contrary, modification of the poly(GMA-co-EGDMA) with glutaraldehyde and cyanuric chloride results in a covalent connection between enzyme and carrier. The obtained results show a significant increase in Cal-B activity. The influence of the amount of glutaraldehyde and cyanuric chloride used for modification was screened. Increasing the amount of glutaraldehyde or cyanuric chloride used for modification resulted in an increase of the enzyme loading. Consequently, higher amount of glutaraldehyde used led to a higher fraction of the enzyme molecules that are covalently connected on to the carrier. As the amount of glutaraldehyde or cyanuric chloride used for modifications increases, activity of immobilized C. antarctica lipase B primarily increases, showing the highest value for 0.66% and 0.050% w/w, respectively, and subsequently decreases. We could show that Cal-B immobilized on epoxy-containing copolymer modified with glutaraldehyde and cyanuric chloride performs higher activity than free enzyme powder. 相似文献
68.
Osama Abboud Konstantin Pussep Aleksandra Kovacevic Katharina Mohr Sebastian Kaune Ralf Steinmetz 《Multimedia Systems》2011,17(3):177-197
Peer-to-Peer (P2P) techniques for multimedia streaming have been shown to be a good enhancement to the traditional client/server
methods when trying to reduce costs and increase robustness. Due to the fact that P2P systems are highly dynamic, the main
challenge that has to be addressed remains supporting the general resilience of the system. Various challenges arise when
building a resilient P2P streaming system, such as network failures and system dynamics. In this paper, we first classify
the different challenges that face P2P streaming and then present and analyze the possible countermeasures. We classify resilience
mechanisms as either core mechanisms, which are part of the system, or as cross-layer mechanisms that use information from
different communication layers, which might inflict additional costs. We analyze and present resilience mechanisms from an
engineering point of view, such that a system engineer can use our analysis as a guide to build a resilient P2P streaming
system with different mechanisms and for various application scenarios. 相似文献
69.
70.
Aleksandra Torbica Biljana Pajin Radovan Omorjan 《Journal of the American Oil Chemists' Society》2011,88(7):937-947
The physical characteristics and color of chocolate depend on the physical properties and crystallization behavior of the
fat phase. In this study, the fat phase of chocolate samples contains cocoa butter from Ghana and soft cocoa butter equivalent
(CBE). The laboratory-made chocolate samples were tempered at three different precrystallization temperatures (25, 27 and
29 °C), using three different concentrations of CBE (3, 5 and 7%), calculated as percentage of the chocolate. Physical characteristics
of chocolate, namely thermoreographic parameters and solid fat content (SFC), were measured. The color of the chocolate was
determined instrumentally, before and after thermo-cycle testing at 32/20 °C. It was found that CBE changed the melting properties
of chocolate produced with cocoa butter from Ghana, which is of moderate hardness. It was determined that the optimum precrystallization
temperature for chocolate mass with addition of CBE in the given conditions of measurement was 27 °C, the temperature that
resulted in the best fat bloom resistance. 相似文献