全文获取类型
收费全文 | 1655篇 |
免费 | 133篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 665篇 |
金属工艺 | 15篇 |
机械仪表 | 30篇 |
建筑科学 | 63篇 |
矿业工程 | 3篇 |
能源动力 | 41篇 |
轻工业 | 407篇 |
水利工程 | 8篇 |
石油天然气 | 8篇 |
无线电 | 70篇 |
一般工业技术 | 177篇 |
冶金工业 | 106篇 |
原子能技术 | 4篇 |
自动化技术 | 190篇 |
出版年
2024年 | 4篇 |
2023年 | 19篇 |
2022年 | 138篇 |
2021年 | 134篇 |
2020年 | 58篇 |
2019年 | 69篇 |
2018年 | 73篇 |
2017年 | 57篇 |
2016年 | 71篇 |
2015年 | 55篇 |
2014年 | 73篇 |
2013年 | 112篇 |
2012年 | 117篇 |
2011年 | 113篇 |
2010年 | 92篇 |
2009年 | 80篇 |
2008年 | 97篇 |
2007年 | 76篇 |
2006年 | 54篇 |
2005年 | 43篇 |
2004年 | 45篇 |
2003年 | 27篇 |
2002年 | 26篇 |
2001年 | 25篇 |
2000年 | 13篇 |
1999年 | 12篇 |
1998年 | 9篇 |
1997年 | 13篇 |
1996年 | 11篇 |
1995年 | 13篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1972年 | 2篇 |
排序方式: 共有1789条查询结果,搜索用时 46 毫秒
141.
John W. Finley Carla Sandlin Darryl L. Holliday Michael J. Keenan Witoon Prinyawiwatkul Jolene Zheng 《Journal of Functional Foods》2013,5(3):1487-1493
Wild type Caenorhabditis elegans (C. elegans) were fed with powdered legumes (1%, w/v): light red kidney, black, navy, white kidney, cranberry, great northern, lentil, lima, or dark red kidney (20%, 33% and 50% of a 1% suspension). Lipophilic fluorescent Nile red dye-stained intestinal fat deposition (IFD) indicated an IFD reduction by legumes in a descending order: light red kidney, black, navy, white kidney, cranberry, great northern, lentil, lima, or dark red kidney. Increased pharyngeal pumping rate (PPR), a surrogate marker of aging, was observed in all legumes at 50% dosage. Both inverse and direct relationships between IFD and PPR were detected in the wild type C. elegans in this study. These results suggested that whole legumes may promote health through regulation of lipid metabolism and lifespan in the model system C. elegans, which enhances our understanding of the effect of legumes and suggests further legumes study in human health. 相似文献
142.
Priscila M.A. Alves Rosemary A. CarvalhoIzabel C.F. Moraes Carla G. LucianoAna Mônica Q.B. Bittante Paulo J.A. Sobral 《Food Hydrocolloids》2011
Both gelatin and poly(vinyl alcohol) (PVA) can be cross linked with glutaraldehyde (GLU). In the case of gelatin, the GLU reacts with each ε-NH2 functional group of adjacent lysine residues, while for PVA, the GLU reacts with two adjacent hydroxyl groups, forming acetal bridges. Thus it can be considered possible to cross link adjacent macromolecules of gelatin and PVA using GLU. In this context, the aims of this work were the development of biodegradable films based on blends of gelatin and poly(vinyl alcohol) cross linked with GLU, and the characterization of some of their main physical and functional properties. All the films were produced from film-forming solutions (FFS) containing 2 g macromolecules (PVA + gelatin)/100 g FFS, 25 g glycerol/100 g macromolecules, and 4 g GLU (25% solution)/100 g FFS. The FFS were prepared with two concentrations of PVA (20 or 50 g PVA/100 g macromolecules) and two reaction temperatures: 90 or 55 °C, applied for 30 min. The films were obtained after drying (30 °C/24 h) and conditioning at 25 °C and 58% of relative humidity for 7 days, and were then characterized. The results for the color parameters, mechanical properties, phase transitions and infrared spectra showed that some chemical modifications occurred, principally for the gelatin. However, in general, all the characteristics of the films were either typical of films based on blends of these macromolecules without cross linking, or slightly higher. A greater improvement in the properties of this material was probably not observed due to the crystallinity of the PVA, which has a melting point above 90 °C. The presence of microcrystals in the polymer chain probably reduced macromolecular mobility, hindering the reaction. Thus more research is necessary to produce biodegradable films with improved properties. 相似文献
143.
Estela Tapia-Venegas Juan Esteban Ramirez Andrés Donoso-Bravo Lorena Jorquera Jean-Phillipe Steyer Gonzalo Ruiz-Filippi 《International Journal of Hydrogen Energy》2013
The objective of this study was to evaluate the production of hydrogen in a two-stage CSTR system – both reactors having the same volume – and compare its performance with a conventional one-stage process. The lab-scale two-stage and one-stage systems were operated at five pHs and five hydraulic retention time (HRTs). The maximum volumetric hydrogen productivity and yield obtained with the two-stage system were 5.8 mmol L−1 h−1 and 2.7 mol H2 mol glucose−1, respectively, at an HRT of 12 h and pH 5.5. Overall, the two-stage system showed, at steady state, a better performance that the one-stage system for all the evaluated pHs. However, a comparison between the one-stage system, operating at 6 h of HRT, and the first reactor of the two-stage system at the same HRT did not show any significant difference, highlighting the positive impact of having a two-stage process. The determination of the ratio between the experimental measured H2 in the gas phase and the theoretical H2 generated in the liquid phase (discrepancy factor) indicated that an important part of the hydrogen produced in the first reactor was transferred into the second reactor instead of being desorbed in the headspace. Therefore, the improving of hydrogen production in the two-stage system is rather attributed to the increased transfer of hydrogen from liquid to gas than an actual total hydrogen production increase. 相似文献
144.
The study investigated the effect of wearing chipper knives on machine productivity, fuel consumption and particles size distribution. The test included two different tree species (poplar and pine), two tree parts (branches and logs) and two screen types (large and medium). Chip quality was defined by CEN international technical standards. Knife wear causes a significant reduction of chipping productivity and a remarkable increase of fuel consumption. The replacement of the standard wide mesh screen with a narrower screen has a similar effect, further decreasing productivity and increasing fuel consumption. For the same screen type and knife wear level, productivity and fuel consumption are the same for poplar and pine. Knife, tree species and tree part also have a significant impact on chip size distribution. Chips produced from logs always contain a smaller proportion of oversize particles and a higher proportion of accepts. For the same large mesh screen, poplar chips tend to be larger than pine chips and to contain a higher proportion of oversize particles. On the contrary, pine chips tend to be smaller and to contain a higher proportion of fines. The use of a narrower mesh screen on pine material does not seem to offer any significant reduction of oversize particles, whose presence is already very limited. Therefore, a standard large mesh screen should be used when chipping pine material. 相似文献
145.
Carla Da Porto Deborha Decorti Andrea Natolino 《International Journal of Food Science & Technology》2013,48(10):2127-2132
Conventional solvent extraction (CE) and ultrasound‐assisted extraction (UAE) in hexane for oil from untreated and enzyme‐treated grape seeds were investigated and compared. Among the output power tested (50, 100 and 150 W) in UAE on untreated seeds, UAE at 150 W for 30 min with liquid‐to‐solid ratio 8:1 (v/w) gave oil extraction yield comparable to CE (ca. 14% w/w) for 6 h with liquid‐to‐solid ratio 12:1 (v/w). CE and UAE at 150 W did not influence the fatty acid profiles of oil. CE oil was found to be the most oxidised. The enzymatic treatments (2, 4 and 6 g per 100 g seeds of Rapidase® Expression) prior to CE enhanced by 2.5% of the oil yield. Enzymatic treatments higher than 2 g per 100 g seeds increased relative value of some fatty acids both in CE and UAE. Enzymatic pretreatment from 2 to 4 g per 100 g seeds significantly improved some physicochemical parameters of oil quality when extracted by CE, but not by UAE. 相似文献
146.
Suyeon Kim Carla Silva Andrea Zille Carmen Lopez Dmitry V Evtuguin Artur Cavaco‐Paulo 《Polymer International》2009,58(8):863-868
BACKGROUND: The ‘double function’ of laccase, from the ascomycete Myceliophthora, to depolymerise/polymerise lignin was studied in this work. A lignosulfonate (LS) compound was oxidised by enzymatic action and several techniques were applied to measure the polymeric changes obtained. This study was focused on the attachment level of the oxidised LS at the flax surface. RESULTS: Modified solutions were studied in terms of surface charge. Zeta potential values obtained showed an increase of polymerisation after several days of incubation. The change in molecular weight after LS polymerisation was detected using gel permeation chromatography. An increase of 1700 Da was achieved. Fourier transform infrared and UV‐visible spectroscopy techniques were applied and the results showed an increase of the degree of polymerisation. The colour strength of flax fabrics incubated with oxidised LS solutions was also measured and an increase of K/S (K, absorption coefficient; S, scattering coefficient) after enzymatic oxidation was observed. CONCLUSION: The oxidised lignin products obtained show good potential for use in natural surface modification of textile materials containing flavonoids. These findings have important practical implications for lignocellulosic fibre coloration, where new polymers can replace harsh chemicals in the textile industry. Copyright © 2009 Society of Chemical Industry 相似文献
147.
T. Canli et al., 2004 (see record 2004-19432-002) use functional MRI to explore the neural interface between personality, mood, and emotional responses. Their finding of a double dissociation in brain response to emotional stimuli based on personality and mood state has significant implications for our understanding of the effects of personality traits and mood states on the neural bases of emotion and cognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
148.
Nelio D. Pizzolato Fabricio Broseghini Barcelos Luiz Antonio Nogueira Lorena 《International Transactions in Operational Research》2004,11(6):667-681
This study is concerned with the location of primary public schools. The public system should have the capacity to satisfy all the demand, although students may choose between public and private schools if they can afford the corresponding costs. A number of factors, such as questionable education quality, limited capacity, poor location and social preferences, secure a participation of about 30% to the private school system. The purpose of this study is both the evaluation of the existing public school network and a relocation proposal. The result of the former was the identification of areas with shortage and excess in school offer. The latter suggests school relocation using capacitated and uncapacitated models. ArcView, a software of the geographic information system (GIS) family, was employed, allowing the efficient handling of large problems and improving the presentation and evaluation of the findings. This methodology was applied to the primary public school network in the area of Vitoria, a state capital located in the southeast region of Brazil with about 300,000 inhabitants. Finally, the practical use of this study and its importance for planning purposes are discussed. 相似文献
149.
Boone Kyle Brauer; Lesser Ira M.; Miller Bruce L.; Wohl Marcy; Berman Nancy; Lee Alison; Palmer Barton; Back Carla 《Canadian Metallurgical Quarterly》1995,9(3):390
Neuropsychological evaluation of 73 older healthy, unmedicated outpatients with major depression and 110 controls suggested that relatively distinct cognitive profiles may correspond to the presence vs. severity of depression. Specifically, the presence of depression was associated with subtle weaknesses in visual memory and nonverbal intelligence, with sparing of verbal skills (verbal intelligence, language, and verbal memory), constructional ability, attention, information processing speed, and executive functions. In contrast, increasing severity of depression was associated with mild weaknesses, primarily in information-processing speed and executive skills, but was essentially unrelated to memory (verbal or visual), intelligence, language skills, constructional ability, or basic attention. Findings are discussed in terms of a possible state vs. trait model of depression. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
150.
Lorena Tobares Carlos Guzmn Damin Maestri 《European Journal of Lipid Science and Technology》2003,105(12):749-753
The aim of the work was to evaluate the effect of extraction method and bleaching on the quality of jojoba waxes from Argentina. Jojoba waxes obtained by cold pressing, Golden wax (expeller‐pressed wax) and Lite wax (bleached wax) were analyzed using standard methods adopted as recommended practices by the American Oil Chemists Society. Physical parameters, fatty acid and alcohol compositions were unchanged among waxes. Cold‐pressed wax was noteworthy by its lower peroxide value, higher amounts of tocopherol and total phenol contents. Accordingly, it presented the best oxidative stability. Bleaching caused a strong decrease in both tocopherol and phenol contents; consequently the bleached wax showed poor oxidative stability. 相似文献