全文获取类型
收费全文 | 93篇 |
免费 | 4篇 |
专业分类
化学工业 | 14篇 |
金属工艺 | 1篇 |
机械仪表 | 1篇 |
建筑科学 | 4篇 |
能源动力 | 1篇 |
轻工业 | 15篇 |
水利工程 | 1篇 |
无线电 | 9篇 |
一般工业技术 | 22篇 |
冶金工业 | 9篇 |
原子能技术 | 1篇 |
自动化技术 | 19篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 6篇 |
2012年 | 3篇 |
2011年 | 5篇 |
2010年 | 4篇 |
2009年 | 6篇 |
2008年 | 7篇 |
2007年 | 2篇 |
2006年 | 6篇 |
2005年 | 4篇 |
2004年 | 4篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2000年 | 1篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1992年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1975年 | 3篇 |
1974年 | 3篇 |
排序方式: 共有97条查询结果,搜索用时 15 毫秒
61.
For silicon, changes in zone size and shape altered only slightly the appearance of the streamlines for a fixed value of the dimensionless thermocapillary flow parameter. However significant changes were noted in the heat and mass transfer and in the magnitude of the dimensionless vorticity.Steady state solutions were also obtained for sapphire with electron beam heating, but could not be obtained with radiant heating. This suggests that oscillatory flow might easily be produced with radiant heating of high Prandtl number materials. 相似文献
62.
Imaging secondary ion mass spectrometry (SIMS) is applied for the first time to paint cross sections with degraded vermilion (red mercury sulfide) paint to cast new light on the well-known problem of its light-induced darkening. The static SIMS data are combined with light microscopic, electron microscopic studies and energy-dispersive X-ray analysis to identify and localize the various reaction products. The spatial distribution of atomic and molecular species in paint cross sections of the native vermilion and the reaction products leads to the formulation of a new hypothesis on the reaction mechanism of the photodegradation of vermilion where two black and white reaction products are formed sequentially. Under the influence of light, some of the vermilion (HgS) is converted into Hg(0) and S(0). In this process, the chlorine ions, present in the native vermilion, act as a catalyst. We propose that the Hg(0) is deposited on the surface of the remaining HgS as elementary mercury nanoparticles, which turns the vermilion black. Chloride, derived from an external source, is accumulating in the black phase. The metallic mercury and the remaining HgS react away with the excess of chloride. Two intermediate products and a white end product, mercuric chloride (HgCl2), are formed. 相似文献
63.
Static secondary ion mass spectrometry (SIMS) is introduced as an analytical technique for the examination of paint cross sections to obtain simultaneous information about the nature and distribution of pigments and the binding medium from a single sample. A sample taken from the virgin's blue robe in the panel painting The Descent from the Cross (Museo del Prado, Madrid) of the Early Netherlandish painter Rogier van der Weyden (1399/1400-1464) was selected for investigation. Data were compared with reference compounds and reference lead white linseed oil paint and egg tempera paint. The static SIMS technique gave position-sensitive mass spectra that were used to image the elemental distribution of pigments and the molecular signature of components of the oleaginous binding medium. SIMS ion images of sodium and aluminum superimposed with the blue pigment ultramarine and those of copper, lead, and calcium with the position of the mineral pigments of azurite, lead white, and chalk, respectively. Preserved monocarboxylic acids of palmitic and stearic acids present as fatty acids and fatty acid lead soaps pointed to the use of linseed oil as a binding medium. Images from the oleaginous binding medium fatty acids show a correlation with the three main paint layers. The observed palmitic/stearic acid ratios for the two ultramarine layers and azurite layers are 1.3, 1.4, and 1.8, respectively. Fatty acids and fatty acid soaps show highest ion yields near lead white, a mineral pigment that serves as a natural chemical drier and is proposed to act as a template for the initial grafting of the polyunsaturated triglycerides of the linseed oil. Almost no fatty acids were detected in other layers visible by light microscopy. The fatty acid lead soaps point toward a mature ionomeric oil paint system that developed over centuries. SIMS evidence for egg tempera, still used in the 15th century, is not detected in the paint cross section. SIMS images correlate well with SEM/EDX, FT-IR and light microscopic images and the SIMS spectral data additionally support the identification of pigment particles, lead soaps, and other binding medium components. 相似文献
64.
Ernest W. Lefever 《The Journal of communication》1975,25(4):181-185
65.
Application of a thermostable Baeyer–Villiger monooxygenase for the synthesis of branched polyester precursors
下载免费PDF全文
![点击此处可从《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Marie AF Delgove Matthew T Elford Katrien V Bernaerts Stefaan MA De Wildeman 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2018,93(8):2131-2140
BACKGROUND
It is widely accepted that the poor thermostability of Baeyer–Villiger monooxygenases limits their use as biocatalysts for applied biocatalysis in industrial applications. The goal of this study was to investigate the biocatalytic oxidation of 3,3,5‐trimethylcyclohexanone using a thermostable cyclohexanone monooxygenase from Thermocrispum municipale (TmCHMO) for the synthesis of branched ?‐caprolactone derivatives as building blocks for tuned polymeric backbones. In this multi‐enzymatic reaction, the thermostable cyclohexanone monooxygenase was fused to a phosphite dehydrogenase (PTDH) in order to ensure co‐factor regeneration.RESULTS
Using reaction engineering, the reaction rate and product formation of the regio‐isomeric branched lactones were improved and the use of co‐solvents and the initial substrate load were investigated. Substrate inhibition and poor product solubility were overcome using continuous substrate feeding regimes, as well as a biphasic reaction system with toluene as water‐immiscible organic solvent. A maximum volumetric productivity, or space–time‐yield, of 1.20 g L‐1 h‐1 was achieved with continuous feeding of substrate using methanol as co‐solvent, while a maximum product concentration of 11.6 g L‐1 was achieved with toluene acting as a second phase and substrate reservoir.CONCLUSION
These improvements in key process metrics therefore demonstrate progress towards the up‐scaled Baeyer–Villiger monooxygenase‐biocatalyzed synthesis of the target building blocks for polymer application. © 2018 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.66.
Microwave‐assisted YBa2Cu3O7 precursors: A fast and reliable method towards chemical precursors for superconducting films
下载免费PDF全文
![点击此处可从《Journal of the American Ceramic Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Hannes Rijckaert Jonathan De Roo Kevin Roeleveld Glenn Pollefeyt Jan Bennewitz Michael Bäcker Frederic Lynen Katrien De Keukeleere Isabel Van Driessche 《Journal of the American Ceramic Society》2017,100(6):2407-2418
Highly stable, pure, and anhydrous organometallic YBa2Cu3O7‐δ (YBCO) precursor solutions were prepared by dissolving commercial YBCO powder in acetone by trifluoroacetic anhydride (TFAA) or a mixture of TFAA with propionic acid for low fluorine precursors. It is shown that compared to conventional oil bath heating reported in literature, the reaction to produce YBCO precursor occurs 72 times faster by microwave heating. More importantly, the formation of byproducts is suppressed, as shown by nuclear magnetic resonance (NMR) and mass spectrometry (MS). This approach allows a highly reproducible preparation of superconducting coatings which is of interest for low‐cost manufacturing processes capable of large‐scale production of the coated conductors via chemical solution deposition (CSD). This technology requires reliable and stable precursor solutions for continuous deposition. In this work, we obtained YBCO thin films on single‐crystal substrates ((100)‐LaAlO3) with a high critical current density (Jc) of 3‐4 MA/cm² in self‐field at 77 K using TFA‐based YBCO precursors and Jc of 5‐6 MA/cm² using low fluorine YBCO precursors. 相似文献
67.
Nathalie Duvigneaud Katrien Wijndaele Lynn Matton Renaat Philippaerts Johan Lefevre Martine Thomis Christophe Delecluse William Duquet 《Nutrition journal》2007,6(1):26
Background
Obesity develops when energy intake continuously exceeds energy expenditure, causing a fundamental chronic energy imbalance. Societal and behavioural changes over the last decades are held responsible for the considerable increase in sedentary lifestyles and inappropriate dietary patterns. The role of dietary fat and other dietary factors in the aetiology and maintenance of excess weight is controversial. The purposes of the present study were to investigate the dietary factors associated with body mass index (BMI) and waist circumference (WC), and to analyse whether dietary intake varies between subjects with different levels of sports participation. 相似文献68.
Simultaneously Excited Downshifting/Upconversion Luminescence from Lanthanide‐Doped Core/Shell Fluoride Nanoparticles for Multimode Anticounterfeiting
下载免费PDF全文
![点击此处可从《Advanced functional materials》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Jing Liu Hannes Rijckaert Min Zeng Katrien Haustraete Brecht Laforce Laszlo Vincze Isabel Van Driessche Anna M. Kaczmarek Rik Van Deun 《Advanced functional materials》2018,28(17)
This work presents a novel anticounterfeiting strategy based on a material changing its emission color in response to a change in the excitation sources—where a single ultraviolet (UV) or near‐infrared (NIR) light source are employed or simultaneously using two excitation sources (xenon lamp and NIR laser). Following this approach, various combinations of lanthanide (Ln3+)‐doped LiLuF4/LiYF4 core/shell nanoparticles are prepared, providing a promising route to design flexible nanomaterials, as well as already a small library of luminescent materials, which change color when varying the excitation source (UV, NIR or both UV and NIR). Aside from excitation source‐dependent color change, these materials additionally show excitation‐source power‐dependent color change. This work exploits the possibility of developing a new class of multimode anticounterfeit nanomaterials, with excellent performance, which would be almost impossible to mimic or replicate, providing a very high level of security. 相似文献
69.
e-Learning organizations are focusing heavily on learning content reusability. The ultimate objective is a learning object
economy characterized by searchable digital libraries of reusable learning objects that can be exchanged and reused across
various learning systems. To enable such approach, basic questions of learning content interoperability need to be addressed.
This paper investigates the interoperation of learning content defined according to different specifications. A number of
content models are reviewed that define learning objects and their components. On the basis of a comparative analysis, the
content models are mapped to a generic model for learning objects to address interoperability questions and to enable share
and reuse on a global scale. 相似文献
70.
Automatic high-dynamic range image generation from low-dynamic range images offers a solution to conventional methods, which require a static scene. The method consists of two modules: a camera-alignment module and a movement detector, which removes the ghosting effects in the HDRI created by moving objects. 相似文献