全文获取类型
收费全文 | 443篇 |
免费 | 18篇 |
专业分类
电工技术 | 6篇 |
化学工业 | 104篇 |
金属工艺 | 13篇 |
机械仪表 | 12篇 |
建筑科学 | 9篇 |
能源动力 | 22篇 |
轻工业 | 77篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 57篇 |
一般工业技术 | 70篇 |
冶金工业 | 10篇 |
自动化技术 | 79篇 |
出版年
2024年 | 4篇 |
2023年 | 9篇 |
2022年 | 11篇 |
2021年 | 23篇 |
2020年 | 25篇 |
2019年 | 17篇 |
2018年 | 24篇 |
2017年 | 13篇 |
2016年 | 23篇 |
2015年 | 20篇 |
2014年 | 15篇 |
2013年 | 39篇 |
2012年 | 28篇 |
2011年 | 29篇 |
2010年 | 27篇 |
2009年 | 23篇 |
2008年 | 20篇 |
2007年 | 14篇 |
2006年 | 8篇 |
2005年 | 11篇 |
2004年 | 14篇 |
2003年 | 12篇 |
2002年 | 6篇 |
2001年 | 10篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1983年 | 1篇 |
1979年 | 2篇 |
排序方式: 共有461条查询结果,搜索用时 15 毫秒
71.
72.
Hocine Djidjelli Mustapha Kaci Tahar Sadoun Djafer Benachour Jean Farenc Juan‐Jog Martinez‐Vega 《大分子材料与工程》2001,286(7):407-411
An accelerated hydrothermic ageing (according to N.F.T. 54043 method) was performed on samples of rigid poly(vinyl chloride). The test consisted of sample immersion in boiling water at 100°C for different exposure periods up to 480 h. The samples were removed from the boiling water every two hours for mechanical and dielectric characterization and color test. The dielectric measurements carried out on aged samples, up to 40 h, showed that the permittivity remained almost constant and its value was found to be 2.3 in the range –100 to +62.8°C. However, as the temperature approaches the glass transition (Tg = 88.3°C), the permittivity was observed to increase rapidly. It was also found that the permittivity of aged samples was lower than that of the non‐aged samples. The dielectric loss factor (tan δ) measurements with respect to temperature have confirmed the presence of two relaxations: β at low temperature (around –35°C) and α near the Tg. The combined action of water and temperature reduced the intensity of the corresponding relaxation peaks. The sample color index was evaluated up to 480 h using the SYNMERO scale in order to estimate the degradation extent. Unexpectedly, elongation at break under uniaxial traction remained unaffected by the hydrothermic ageing, meaning that two competing processes were involved simultaneously (sample degradation via chain scission and sample plastification via water absorption). 相似文献
73.
This paper deals with the effects of excluded volume interactions on the thermodynamic and structural properties of cyclic polymers in good solvents. Several thermodynamic properties are discussed with particular emphasis on excluded volume interactions and their effects on the radii of gyration and the form factors. An empirical model describing the mean square distance between two points along a cyclic polymer is proposed and its predictions compared with those of other models. Comparison between cyclic and linear chain properties highlights the effects of chain closure under good solvent conditions. © 2000 Society of Chemical Industry 相似文献
74.
Aline Olivier Tadeusz Pakula Bernd Ewen Xavier Coqueret Mustapha Benmouna Ulrich Maschke 《大分子材料与工程》2002,287(10):656-659
This article reports on mechanical properties of electron beam cured tripropylene glycol diacrylate (TPGDA) and propoxylated glycerol triacrylate (GPTA) films. This study has been motivated by the need to have direct access to those properties for analyzing the thermo‐mechanical behavior and electro‐optical properties of polymer dispersed liquid crystal systems in general, and systems made either of TPGDA or GPTA and low molecular weight liquid crystals in particular. Representative examples of these systems are considered in this work. The effects of the degree of crosslinking on the mechanical strength of the polymer network are analyzed by considering different doses of the electron beam irradiation. As the radiation dose increases, the mechanical strength of the film is enhanced. Addition of a small amount of liquid crystals leads to remarkable plasticizing effects.
75.
76.
Healthcare organizations strive to make the best use of their organizational knowledge. The collective know-hows of the medical workers directly affect the quality of the delivered healthcare services. This study addresses the healthcare knowledge-sharing among a community of specialized physicians. An extensive study of the literature on knowledge-sharing in industries generally and healthcare organizations specifically were presented. Six focal elements were detected in previous attempts to address the knowledge-sharing status in healthcare organizations. Additionally, three previous models for healthcare knowledge management were analyzed. The studied literature along with the three studied models helped in constructing the framework and suggesting a suitable research methodology for primary data collection. Qualitative approach of in-depth interview technique was used for interviewing eight specialized physicians. The data collected from the interviewees were then analyzed and produced explanatory themes and codes. These themes are physicians’ acquisition of medical knowledge, staff participating in the knowledge sharing, knowledge-sharing culture, ICT-based knowledge sharing and top management involvement. The findings resulted in recognizing four considerations which ought to be taken into account for successful knowledge-sharing activities and learning initiatives in the healthcare organization. Conclusions and recommendations for future studies were presented based on the implications of this research study. 相似文献
77.
Khaled Hriz Nejmeddine Jaballah Jean-Louis Fave Mustapha Majdoub 《Journal of Materials Science》2012,47(23):8067-8075
Two soluble anthracene-based organic materials (BPA-An1 and BPA-An2) have been synthesized and characterized. The optical properties of these π-conjugated systems were investigated by UV–Visible absorption and photoluminescence (PL) spectroscopies. The optical gaps were estimated from the absorption onsets of the thin polymer films; their values were 3.01 and 2.76?eV for BPA-An1 and BPA-An2, respectively. The PL spectrum of BPA-An2 exhibits a blue emission both in dilute solution and thin film. BPA-An1 showed a blue photoluminescence in dilute solution; in solid film, π–π interactions influence its optical behavior and a green emission was observed. The HOMO and LUMO levels were estimated using cyclic voltammetry analysis. Single-layer devices of the (indium-tin oxide/anthracene-based material/aluminum) configuration have been elaborated and showed relatively low turn-on voltages of 6.2–5.5?V for BPA-An1 and BPA-An2, respectively. 相似文献
78.
Mustapha Benjillali Leszek Szczecinski Sonia Aïssa Cristian Gonzalez 《Wireless Communications and Mobile Computing》2008,8(7):831-844
In this paper, we propose a method for evaluation of the bit error rate (BER) for packet combining based on constellation rearrangement (CoRe). Such mapping diversity scheme, adopted in the high speed downlink packet access (HSDPA), uses Gray‐mapped constellations and is based on suboptimal accumulation of the reliability metrics generated in each of the transmissions. We present an exact model for the logarithmic likelihood ratios (LLR) obtained by means of the so‐called max‐log approximation, and we show that their conditional probability density functions (pdf) are piecewise Gaussian. We then present the derivation of the uncoded BER and illustrate it with simulation results that confirm our formulation. Finally, we propose simplifications which significantly reduce the complexity of the evaluation method and provide results with a very good accuracy; an extension to transmissions over faded channel is also presented. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
79.
Engineered Nanoparticles as Potential Food Contaminants and Their Toxicity to Caco‐2 Cells 下载免费PDF全文
Xiaomo Mao Trang H.D. Nguyen Mengshi Lin Azlin Mustapha 《Journal of food science》2016,81(8):T2107-T2113
Engineered nanoparticles (ENPs), such as metallic or metallic oxide nanoparticles (NPs), have gained much attention in recent years. Increasing use of ENPs in various areas may lead to the release of ENPs into the environment and cause the contamination of agricultural and food products by ENPs. In this study, we selected two important ENPs (zinc oxide [ZnO] and silver [Ag] NPs) as potential food contaminants and investigated their toxicity via an in vitro model using Caco‐2 cells. The physical properties of ENPs and their effects on Caco‐2 cells were characterized by electron microscopy and energy dispersive X‐ray spectroscopic (EDS) techniques. Results demonstrate that a significant inhibition of cell viability was observed after a 24‐h of exposure of Caco‐2 cells to 3‐, 6‐, and 12‐mM ZnO NPs or 0.5‐, 1.5‐, and 3‐mM Ag NPs. The noticeable changes of cells include the alteration in cell shape, abnormal nuclear structure, membrane blebbing, and cytoplasmic deterioration. The toxicity of ZnO NPs, but not that of Ag NPs after exposure to simulated gastric fluid, significantly decreased. Scanning transmission electron microscopy shows that ZnO and Ag NPs penetrated the membrane of Caco‐2 cells. EDS results also confirm the presence of NPs in the cytoplasm of the cells. This study demonstrates that ZnO and Ag NPs have cytotoxic effects and can inhibit the growth of Caco‐2 cells. 相似文献
80.
This work aims to study the effects of date stone flour (DSF) on morphology, thermal, and mechanical properties of polypropylene (PP) composites in the absence and presence of ethylene‐butyl acrylate‐glycidyl methacrylate (EBAGMA) used as the compatibilizer. DSF was added to the PP matrix at loading rates of 10, 20, 30, and 40 wt %, while the amount of compatibilizer was fixed to the half of the filler content. The study showed through scanning electron microscopy analysis that EBAGMA compatibilizer improved the dispersion and the wettability of DSF in the PP matrix. Thermogravimetric analysis (TGA) indicated a slight decrease in the decomposition temperature at onset (Tonset) for all composite materials compared to PP matrix, whereas the thermal degradation rate was slower. Differential scanning calorimetry (DSC) data revealed that the melting temperature of PP in the composite materials remained almost unchanged. The nucleating effect of DSF was however reduced by the compatibilizer. Furthermore, the incorporation of DSF resulted in the increase of stiffness of the PP composites accompanied by a significant decrease in both the stress and strain at break. The addition of EBAGMA to PP/DSF composites improved significantly the ductility due to the elastomeric effect of EBAGMA. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献