全文获取类型
| 收费全文 | 2886篇 |
| 免费 | 46篇 |
| 国内免费 | 5篇 |
学科分类
| 工业技术 | 2937篇 |
出版年
| 2024年 | 45篇 |
| 2023年 | 41篇 |
| 2022年 | 106篇 |
| 2021年 | 132篇 |
| 2020年 | 108篇 |
| 2019年 | 99篇 |
| 2018年 | 83篇 |
| 2017年 | 92篇 |
| 2016年 | 92篇 |
| 2015年 | 95篇 |
| 2014年 | 76篇 |
| 2013年 | 184篇 |
| 2012年 | 178篇 |
| 2011年 | 184篇 |
| 2010年 | 116篇 |
| 2009年 | 129篇 |
| 2008年 | 113篇 |
| 2007年 | 112篇 |
| 2006年 | 106篇 |
| 2005年 | 86篇 |
| 2004年 | 73篇 |
| 2003年 | 59篇 |
| 2002年 | 69篇 |
| 2001年 | 40篇 |
| 2000年 | 25篇 |
| 1999年 | 35篇 |
| 1998年 | 83篇 |
| 1997年 | 61篇 |
| 1996年 | 31篇 |
| 1995年 | 26篇 |
| 1994年 | 21篇 |
| 1993年 | 25篇 |
| 1992年 | 14篇 |
| 1991年 | 15篇 |
| 1990年 | 10篇 |
| 1989年 | 19篇 |
| 1988年 | 10篇 |
| 1987年 | 16篇 |
| 1986年 | 14篇 |
| 1985年 | 8篇 |
| 1984年 | 14篇 |
| 1983年 | 10篇 |
| 1982年 | 5篇 |
| 1981年 | 7篇 |
| 1980年 | 15篇 |
| 1977年 | 5篇 |
| 1976年 | 13篇 |
| 1975年 | 4篇 |
| 1974年 | 7篇 |
| 1972年 | 4篇 |
排序方式： 共有2937条查询结果，搜索用时 31 毫秒
991.
Gabriel Rampazzo Magalhães;Gabriely Fernanda Groto Militão;Natália Oliveira de Farias;Anjaina Fernandes de Albuquerque;Marina Tenório Botelho;Riikka Räisänen;Harold S. Freeman;Gisela de Aragão Umbuzeiro; 《Coloration Technology》2024,140(4):620-628
Traditional textile dyeing processes usually require large quantities of water and energy and generate wastewater that can be harmful to the environment. Dyeing in supercritical carbon dioxide (sc-CO2) media is promising in textile coloration due especially to it providing a waterless process and eliminating the need for an energy intensive drying step. The natural anthraquinone emodin showed promising results for dyeing different fibres through sc-CO2 process. However, emodin is mutagenic. The aim of this study was to develop non-mutagenic derivatives of emodin that can be applied to textiles using sc-CO2. Emodin structure was modified incorporating acryloyl groups, which are considered suitable for decreasing potential for DNA intercalation, and thus mutagenicity. The presence of acryloyl groups would also enable atmospheric plasma induced bonding with fibres. Molecular modelling studies showed that emodin derivatives became less planar with increasing number of attached acryloyl groups, making intercalation unlikely. The derivatives produced were tested to assess mutagenicity in vitro (Salmonella/microsome assay, TA1537, 10% S9) and in vivo (micronucleus test in hemocytes of aquatic crustacean). We found that emodin can be derivatised using acryloyl chlorides to give mono- and di-acrylate esters suitable for dyeing polyester fibres in sc-CO2. However, the new dyes presented mutagenicity for both in vitro and in vivo. Although the derivatives provided greenish-yellow alternatives to emodin for dyeing synthetic fibres, they do not appear to be viable alternatives from the point of view of preserving human and environmental health. Plasma bonding studies are underway. 相似文献
992.
The solubility parameter and the Flory–Huggins interaction parameter of two EVA (ethylene–vinyl acetate) copolymers, each one with different vinyl acetate content, are calculated by using inverse gas chromatography technique. The influence of the vinyl acetate percentage is analyzed and indicates that the polymer–solvent interactions are stronger in the case of the copolymer with the highest vinyl acetate percentage. The results also point to the fact that the most favorable solvents for the studied materials are the aromatic‐type ones. Finally, from the calculated values of the polymer solubility parameter (16.3 MPa0.5 for EVA 460 and 15.1 MPa0.5 for EVA410, at 50°C), it can be noticed that the solubility parameter of the EVA copolymer with the largest vinyl acetate content is the closest to the solubility parameter of pure vinyl acetate. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
993.
This article addresses the preparation and characterization of composite materials obtained with compression molding of mixtures of aluminum powder and a commercial grade thermosetting resin of poly(urea‐formaldehyde) filled with α‐cellulose in powder form. The homogeneity of these composites was checked by the morphologies of the constituents (filler and matrix) by optical microscopy. The density of the composites was measured and compared with values calculated by assuming different void levels within the samples, to discuss the porosity effect, in connection with optical microscopy observations. Then, the dependence of electrical conductivity of the composites on volume fraction of the metal filler was investigated. The conductivity of the composites is <10−12 S/cm unless the metal content reaches the percolation threshold at a volume fraction of Vc = 38.6 vol%, beyond which the conductivity increases markedly by as much as nine orders of magnitude, indicating an insulator–conductor phase transition. The obtained results on electrical conductivity have been well interpreted with the statistical percolation theory. The deduced critical parameters, such as the threshold of percolation, Vc, the critical exponent, t, and the packing density coefficient, F, were in good accord with earlier studies. In addition, the hardness of samples remained almost constant with the increase of metal concentration. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers 相似文献
994.
The quantitative syntheses of α‐bis and α,ω‐tetrakis tertiary diamine functionalized polymers by atom transfer radical polymerization (ATRP) methods are described. A tertiary diamine functionalized 1,1‐diphenylethylene derivative, 1,1‐bis[(4‐dimethylamino)phenyl]ethylene (1), was evaluated as a unimolecular tertiary diamine functionalized initiator precursor as well as a functionalizing agent in ATRP reactions. The ATRP of styrene, initiated by a new tertiary diamine functionalized initiator adduct (2), affords the corresponding α‐bis(4‐dimethylaminophenyl) functionalized polystyrene (3). The tertiary diamine functionalized initiator adduct (2) was prepared in situ by the reaction of (1‐bromoethyl)benzene with 1,1‐bis[(4‐dimethylamino)phenyl]ethylene (1) in the presence of a copper (I) bromide/2,2′‐bipyridyl catalyst system. The ATRP of styrene proceeded via a controlled free radical polymerization process to afford quantitative yields of the corresponding α‐bis(4‐dimethylaminophenyl) functionalized polystyrene derivative (3) with predictable number‐average molecular weight (Mn) and narrow molecular weight distribution (Mw/Mn) in a high initiator efficiency reaction. The polymerization process was monitored by gas chromatography analysis. Quantitative yields of α,ω‐tetrakis(4‐dimethylaminophenyl) functionalized polystyrene (4) were obtained by a new post ATRP chain end modification reaction of α‐bis(4‐dimethylaminophenyl) functionalized polystyrene (3) with excess 1,1‐bis[(4‐dimethylamino)phenyl]ethylene (1). The tertiary diamine functionalized initiator precursor 1,1‐bis[(4‐dimethylamino)phenyl]ethylene (1) and the different tertiary amine functionalized polymers were characterized by chromatography, spectroscopy and non‐aqueous titration measurements. Copyright © 2012 Society of Chemical Industry 相似文献
995.
Abd El‐Shafey I. Ahmed John N. Wardell Alfred E. Thumser Claudio A. Avignone‐Rossa Gabriel Cavalli John N. Hay Michael E. Bushell 《应用聚合物科学杂志》2011,119(2):709-718
The effects of two halogenated compounds (sodium hypochlorite and N‐halamine polymers) on the Escherichia coli metabolome were investigated. Changes in the intracellular metabolite pools of bacterial cells treated with different formulations of these compounds were analysed using FTIR (Fourier Transform Infra Red) spectroscopy and LC‐MS (Liquid Chromatography‐Mass Spectroscopy). Principal component analysis was used to generate metabolic profiles of the intracellular metabolites to investigate the effect of sublethal concentrations on the metabolome of treated cells. The effect of treatment with sodium hypochlorite was quantitatively dependent on the exposure time. The resulting metabolic profiles supported our previous hypothesis that the mode of action of some halogenated compounds, such as N‐halamine polymers, can be initiated by release of halogen ions into the aqueous environment, in addition to direct contact between the solid polymer material and the bacterial cells. Moreover, the metabolic profiles were able to differentiate between the effect of free and polymer‐bound halogen. Our metabolomic approach was used for hypothesis generation to distinguish apparently different bactericidal effects of free and polymer‐bound halogen. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
996.
Swelling behavior of a commercial linear polystyrene, containing a small amount (<5% wt) of mineral oil, has been studied in three different classes of organic solvents (alkanes, alcohols and carboxylic acids) using both gravimetry and light microscopy. A comparison has been made with the results presented in earlier publications using a different linear polystyrene, without mineral oil. It is shown that the polystyrene containing mineral oil absorbs much higher amounts of solvent at lower temperatures then at higher temperatures. This anomalous behavior sharply contrasts with the polystyrene without mineral oil, which at lower temperatures absorbs much less solvent. Light microscopy of the diffusion layer reveals that in the polymer with mineral oil precipitation occurs during diffusion at low temperatures, but not at high temperatures. These results clearly show that the presence of small amounts of mineral oil (in quantities below the detection limit of FTIR) can cause significant changes in the sorption behavior of polymers. These results are interpreted by pre‐existing nano‐inhomogeneities, formed by the mineral oil, limited miscibility of oil in the polymer phase and high miscibility of solvent in the oil phase. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
997.
Antonio Ramírez Fajardo Luis Esteban Cerdán Alfonso Robles Medina Fracisco Gabriel Acién Fernández Pedro A. González Moreno Emilio Molina Grima 《European Journal of Lipid Science and Technology》2007,109(2):120-126
Ethanol was used for the extraction and purification of lipids from the biomass of the microalga Phaeodactylum tricornutum. This microalga is an oil‐rich substrate with a high proportion of eicosapentaenoic acid (EPA). The process consisted of two steps. First, ethanol (96% vol/vol) was used to extract the lipids from the lyophilized biomass. Second, a biphasic system was formed by adding water and hexane to the extracted crude oil. In this way, most of the lipids were transferred to the hexanic phase while most impurities remained in the hydroalcoholic phase. The first step was carried out by two consecutive extractions at room temperature, each with 5 mL ethanol per gram of biomass, for 10 and 1.25 h, respectively. Under these conditions, over 90% of the saponifiable lipids in the biomass were extracted. In the second step, the percentage of water in the hydroalcoholic phase, the hexane/hydroalcoholic phase ratio and the number of extraction steps were optimized. A water content of 40% vol/vol in the hydroalcoholic phase provided the highest lipid recovery. A recovery yield of 80% was obtained by four consecutive extractions with a hexane/hydroalcoholic phase ratio of 0.2 (vol/vol). Equilibrium distribution data of the lipids between the hydroethanolic and the hexanic phases were also obtained in order to predict the lipid recovery yield of the extraction. This process is an alternative to the traditional methods of lipid extraction, which uses less toxic solvents and reduces the total amount of solvents used. 相似文献
998.
In this work, we present a comparative study of the energy‐efficiency performance between conventional distillation sequences and thermally coupled distillation arrangements (TCDS) for the separation of ternary mixtures of hydrocarbons under the action of feedback control loops. The influence of the relative ease of separation of the feed mixture and its composition was analyzed. The feedback analysis was conducted through servo tests with individual changes in the set points for each of the three product streams. Standard PI controllers were used for each loop. The results show an apparent trend regarding the sequence with a better dynamic performance. Generally, TCDS options performed better for the control of the extreme components of the ternary mixture (A and C), while the conventional sequences offered a better dynamic behaviour for the control of the intermediate component (B). The only case in which there was a dominant structure for all control loops was when the feed contained low amounts of the intermediate component and the mixture had similar relative volatilities. The Petlyuk column provided the optimal choice in such case, which contradicts the general expectations regarding its control behaviour. In addition, the energy demands during the dynamic responses were significantly lower than those observed for the other distillation sequences. TCDS options, therefore, are not only more energy efficient than the conventional sequences, but there are cases in which they also offer better feedback control properties. 相似文献
999.
P. Nogueira C. Ramírez A. Torres M. J. Abad J. Cano J. Lpez I. Lpez‐Bueno L. Barral 《应用聚合物科学杂志》2001,80(1):71-80
The characteristics of sorption and diffusion of water in an amine‐cured epoxy system based on tetraglycidyl diaminodiphenylmethane and a novolac glycidyl ether resin were studied as a function both of the polymer microstructure, known from previous works, and the temperature. Water‐sorption experiments and dynamic mechanical analysis (DMA) were performed. Tensile stress–strain and Rockwell hardness tests were conducted to investigate the effects of absorbed water on the mechanical properties of the material. Competing effects of the sorption of water in the free volume and of strong interactions between water molecules and polar groups of the network were used to explain the diffusional behavior observed, which followed Fick's second law. DMA analysis seemed to be sensitive to the water effects and the viscoelastic behavior was related both to the water‐sorption processes and to the microstructure of the system. An important impact of water uptake on the tensile properties at break was also appreciated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 71–80, 2001 相似文献
1000.
Elvira Oliva Sánchez-Sáenz Julian Cruz-Olivares Angélica Román-Guerrero Juan Gabriel Baéz-González María Eva Rodríguez-Huezo 《Drying Technology》2013,31(8):863-872
The adsorption isotherms of allspice essential oil microencapsulated in biopolymers blend (whey protein concentrate [WPC], mesquite gum [MG], and maltodextrin DE10 [MD]) in different proportions (WPC17%-MG17%-MD66% w/w and WPC66%-MG17%-MD17% w/w) with wall-to-core material ratios of 4:1 were determined at 25, 35, and 40°C. The isotherms were fitted using the Guggenheim-Anderson-de Boer (GAB) model and the enthalpies and entropies, both differential and integral, were estimated by the Clausius-Clapeyron method. The minimum integral entropy was considered as the point of maximum stability where strong bonds between the adsorbate and adsorbent occurred, and water would be less available and likely to participate in spoilage reactions. The point of maximum stability was found between 13.79 and 15.11 kg H2O/100 kg d.s. (corresponding to water activity, a W , of 0.444–0.551) for the microcapsules with WPC17%-MG17%-MD66% w/w as wall material and 18.71–19.63 kg H2O/100 kg d.s. (a W = 0.591–0.713) for the microcapsules with WPC66%-MG17%-MD17% w/w as wall material in the temperature range studied. 相似文献
