全文获取类型
收费全文 | 2374篇 |
免费 | 187篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 27篇 |
化学工业 | 599篇 |
金属工艺 | 71篇 |
机械仪表 | 79篇 |
建筑科学 | 123篇 |
矿业工程 | 8篇 |
能源动力 | 226篇 |
轻工业 | 478篇 |
水利工程 | 11篇 |
石油天然气 | 7篇 |
无线电 | 106篇 |
一般工业技术 | 357篇 |
冶金工业 | 32篇 |
原子能技术 | 58篇 |
自动化技术 | 380篇 |
出版年
2024年 | 18篇 |
2023年 | 44篇 |
2022年 | 77篇 |
2021年 | 143篇 |
2020年 | 101篇 |
2019年 | 82篇 |
2018年 | 180篇 |
2017年 | 154篇 |
2016年 | 163篇 |
2015年 | 92篇 |
2014年 | 142篇 |
2013年 | 362篇 |
2012年 | 161篇 |
2011年 | 171篇 |
2010年 | 188篇 |
2009年 | 168篇 |
2008年 | 100篇 |
2007年 | 125篇 |
2006年 | 42篇 |
2005年 | 13篇 |
2004年 | 6篇 |
2003年 | 8篇 |
2002年 | 11篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
排序方式: 共有2562条查询结果,搜索用时 15 毫秒
101.
Black carrots (BCs) are a rich source of stable anthocyanins (ACNs). The purpose of this study was to evaluate the effects of clarification and pasteurisation on ACNs of black carrot juice (BCJ). Monomeric ACNs, ACN profile and percent polymeric colour were determined during processing of BCJ. While depectinisation and bentonite treatments resulted in 7% and 20% increases in monomeric ACN content of BCJ, respectively, gelatine–kieselsol treatment and pasteurisation resulted in 10% and 3–16% reduction. Percent polymeric colour decreased after clarification, but substantially increased in samples subjected to heat. ACNs of BCJ samples were identified by HPLC–MS. Unclarified BCJ contained cyanidin-3-galactoside-xyloside-glucoside-ferulic acid as the major ACN, followed by cyanidin-3-galactoside-xyloside-glucoside-coumaric acid, and cyanidin-3-galactoside-xyloside-glucoside. After depectinisation, two more ACNs (cyanidin-3-galactoside-xyloside and cyanidin-3-galactoside-xyloside-glucoside-sinapic acid) were also identified. These results indicated that depectinisation and bentonite treatment had positive effect on the colour of BCJ, while gelatin–kieselsol treatment and pasteurisation had negative effect. 相似文献
102.
Ahenk Yılmaz 《Color research and application》2017,42(3):378-387
Abstract: This article explores the effects of using black on spatial experience by means of phenomenological analysis of its architectural examples with a special focus on Serpentine Gallery Pavilion designed by Peter Zumthor. Contrary to the growing interest in the color in contemporary architecture, black rarely found a place in architectural history and in studies on color design. Whereas, the distinct achromatic qualities of the color that appear highly self‐contradictory swinging back and forth from absence to presence cover a wide range of potentials to be used in architectural design. Through insights delved into the spatial experience constructed around these qualities, this paper attempts to analyze how black is used as a design element in built environments. This analysis revolves around Zumthor s pavilion, which stood as a uniform black box on the expanse of green grass of London Kensington Gardens for more than three months in 2011. Encompassing various oppositions, the box built to surround a hortus conclusus, an enclosed garden inside, provided its visitors with a unique spatial experience depending predominantly on the combination of its form, tectonics and the qualities of its color, black. The phenomenological analysis of these qualities manifests that the architect utilized the contradictory characteristics of the color intentionally in order to create a complex and manifold spatial experience for visitors in and outside the box. In an interplay of absence and presence, momentary crystallizations of the vision of black provide architects with uncharted opportunities for creative use of color in the design of built environments. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 378–387, 2017 相似文献
103.
104.
105.
Tulay Y. İnan Emel Yıldız Birsen Karaca Hacer Dogan Alican Vatansever Muhammed Nalbant Koray Eken 《Journal of materials science. Materials in medicine》2014,25(8):2027-2039
We produced UV curable lenses with properties blocking short wave UV light. In the UV-curable formulations, we used an oligomer (Ac-PEEK) with another urethan oligomer (Mw = 2000). Radically active, molecular weight controlled Ac-PEEK was obtained by reacting 2-hydroxyl ethyl methacrylate with molecular- weight- controlled and isocyanate terminated PEEK (Mn = 4500). We characterized all synthesized monomer, oligomer and optical materials with UV/Vis spectrophotometer with interferogram, elemental analyser, mass spectrophotometer, proton nuclear magnetic resonance, Fourier transform infrared spectroscopy, thermal gravimetric analyzer, differential scanning calorimeter, scanning electron microscopy and gas chromatography. Results suggested that newly synthesized oligomer with the structure of PEEK absorbs short wave UV-light. Ageing tests [ISO 11979-5, Ophthalmic implants—intraocular lenses (IOL)—Part 5: Biocompatibility] performed on the IOL materials were successful. High contact angle of the obtained lenses suggests that all lenses were hydrophobic and SEM results revealed that lenses are morphologically homogeneous. Based on all positive properties just mentioned, we safely conclude that the lenses produced in this study are very promising for IOL production. 相似文献
106.
Mehmet Ali Yurdusev Ahmet Ali Kumanlıoğlu Yüksel Abalı M. Sadrettin Zeybek 《Construction and Building Materials》2009,23(5):1871-1877
In this study, usability of wastes produced in phosphoric acid plants in structural brick manufacture has been investigated. There are several parameters involved in using these wastes in brick production namely the rate of added waste, firing speed and firing temperature. The performance of these parameters can be measured by several criteria such as natural drying shortening, water absorption and weight loss. Therefore, so many experiments are needed to investigate the effects of these parameters on the bricks produced with these wastes. The result of a series of experiments were utilized to achieve this end. The results have shown that the industrial wastes considered improve the performance of the bricks in terms of the criteria mentioned above. However, the results have also shown that further investigations are needed to explore the effects of interim values on the performance of the bricks. To achieve that end, a neural experimental study is adopted. For this purpose, the results of the experiments conducted were used to construct an artificial neural network. The trained and tested network was then used to check the effects of 280 different combinations for each type of material mixtures mentioned. The outcome of these artificial tests have provided the optimal values for the waste addition rate, firing speed and firing temperature based on the four criteria mentioned previously. 相似文献
107.
Selçuk Kılınç Gökhan Çabuk 《International Journal of Circuit Theory and Applications》2015,43(3):390-400
In power electronics, the switching elements are controlled by pulse width modulated (PWM) signals making their currents on and off repeatedly. This might cause electromagnetic interference (EMI) problems especially in switched mode power supplies. One method for mitigating the EMI is to use the frequency modulation technique in the control signal of the switching metal–oxide–semiconductor field‐effect transistor. According to this approach, frequency of the PWM signal is modulated in order to spread its spectrum and hence reduce the EMI levels. This paper presents the theoretical analysis for the spectrum of a frequency modulated PWM signal. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
108.
The aim of this study was to fabricate needle like‐TiO2/polyrhodanine nanostructures by polymerizing rhodanine monomer on the TiO2 nanoparticles' surfaces and investigate their antibacterial activities. The structural, thermal, morphological, surface and electrical properties of non‐covalently functionalized nanoparticles were characterized by using FTIR, XPS, elemental analysis, TGA, XRD, SEM‐EDX, TEM, contact angle, and conductivity measurements. Characterization results confirmed the formation of needle like‐TiO2/polyrhodanine (PRh) core/shell hybrid nanostructures. Alterations on the surface and electrokinetic properties of the materials were characterized by zeta (ζ)‐potential measurements with the presence of various salts and surfactants. The ζ‐potential of needle like‐TiO2 was observed to increase from ?7.6 mV to +28.4 mV after forming a core/shell needle like‐TiO2/PRh nanocomposite structure and with the presence of cetyltrimethyl ammonium bromide (CTAB) surfactant. Thereby colloidally more stable dispersions were formed. Antibacterial properties of needle like‐TiO2/PRh were also tested against Staphylococcus aureus, Klebsiella pneumoniae, and Escherichia coli by various methods and they showed good antibacterial activity. The highest killing efficiency was determined for needle like‐TiO2/PRh against E. coli by colony‐counting method as 0.95. TEM experiments also showed the immobilizations of the nanoparticles on E. coli and revealed the interactions between E. coli and the nanoparticles. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41554. 相似文献
109.
Degradation kinetics of PVC plasticized with different plasticizers under isothermal conditions 下载免费PDF全文
The aim of the present work is to elucidate the degradation kinetics of polyvinyl chloride (PVC) plasticized with some phthalate and nonphthalate plasticizers. A PVC thermomat instrument was utilized to maintain the isothermal degradation conditions at 140 and 160°C, and to suppress the oxidative degradation by means of nitrogen flow. The conductivity measurements were performed to follow hydrogen chloride (HCl) gas which is released upon PVC degradation and trapped in water. Dehydrochlorination of plasticized PVC films occurred with activation energies of about 23–160 and 26–117 kJ mol?1 and the isokinetic temperatures, at which the dehydrochlorination rate constants of all p‐PVC films would have the same value, were found to be 171 and 128°C for initial and linear regions of dehydrochlorination curve, respectively. Plasticizer incorporation contributes to the stability of the films particularly after the consumption of stabilizer due to the dehydrochlorination. Influence of temperature rise by 20°C on the degradation rate constant is the lowest for DINCH having p‐PVC films as 0.36 and 0.42% increment at the initial region and linear region, respectively. On the other hand, DOTP reveals greater stability than the others do since the compensation ratio of the PVC film having DOTP is greater than the other films. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41579. 相似文献
110.
Ring Opening of Epoxidized Soybean Oil with Compounds Containing Two Different Functional Groups 下载免费PDF全文
Kemal Karadeniz Hatice Akı Mustafa Yasin Sen Yakup Çalıkoğlu 《Journal of the American Oil Chemists' Society》2015,92(5):725-731
Epoxidized vegetable oils are desirable chemicals due to their eco‐friendly characteristics and their being a major source of many green products. Ring opening is one of the ways to convert these epoxidized oils to some new intermediates. The use of mono‐functional amines, alcohols, acid anhydrides and thioethers for epoxy ring opening has been reported in the literature. In this study, thioglycolic acid (TGA) bearing thiol and carboxylic acid as two different functional groups and methyl ester of thioglycolic acid (TGAME) were used. Currently, there is no reported literature describing epoxy ring opening using chemicals bearing two different functional groups simultaneously. In this way, two new polyols were synthesized, one with TGA (polyol 1) and one with TGAME (polyol 2). FTIR and 1H‐ and 13C‐NMR spectroscopy confirmed that the ring was opened by the carboxylic acid group of TGA, and the thiol group was not involved in the ring opening whereas the ring was opened by the thiol group in the case of TGAME. 相似文献