首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   133篇
  免费   2篇
化学工业   22篇
建筑科学   4篇
矿业工程   1篇
能源动力   3篇
轻工业   45篇
无线电   5篇
一般工业技术   21篇
冶金工业   11篇
自动化技术   23篇
  2024年   1篇
  2022年   2篇
  2021年   4篇
  2020年   1篇
  2019年   1篇
  2017年   2篇
  2016年   3篇
  2015年   6篇
  2014年   6篇
  2013年   16篇
  2012年   7篇
  2011年   11篇
  2010年   9篇
  2009年   4篇
  2008年   3篇
  2007年   3篇
  2006年   8篇
  2005年   5篇
  2004年   8篇
  2003年   3篇
  2002年   5篇
  2001年   1篇
  2000年   3篇
  1998年   3篇
  1997年   2篇
  1996年   2篇
  1995年   3篇
  1994年   2篇
  1993年   1篇
  1992年   4篇
  1991年   1篇
  1989年   2篇
  1988年   1篇
  1985年   1篇
  1976年   1篇
排序方式: 共有135条查询结果,搜索用时 15 毫秒
51.
52.
The authors examined individual differences in reading development in English and Finnish. English-speaking Canadian children were assessed once per year in Grades 1-5, and Finnish children were assessed twice per year in Grades 1-2. Results from latent growth curve and simplex analyses showed that initial status was generally negatively associated with subsequent growth and that, although stable, individual differences were more likely to significantly decrease than to increase across the measurement points. Growth mixture models identified multiple groups of children whose reading development followed distinct patterns. The results indicate that it is possible for educational systems to significantly reduce individual differences in basic reading skills during early reading development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
53.
An organic matrix diode backplane for driving an electrophoretic display with an unpatterned front plane electrode is reported. Using thin film diodes instead of transistors as the active components in the pixels enable the backplane to be manufactured using roll-to-roll compatible printing processes. The backplane functionality is demonstrated in an electrophoretic display using 16 copper pixel electrodes, each of which is connected to two printed organic diodes. The printed diodes have sputtered copper cathodes and printed silver anodes. The diodes and pixels are arranged in a lateral 4 by 4 matrix structure with a dielectric layer separating the row and column electrodes. The dielectric, semiconductor and silver layers are all printed using a laboratory-scale rotary gravure press. The display module is finalized by laminating the front plane material onto the backplane.  相似文献   
54.
Bilberries (Vaccinium myrtillus L.) and black currants (Ribes nigrum L.), dark blue berries rich in anthocyanins, were processed with an aid of commercial pectinolytic enzyme preparations, and the effect of processing on berry anthocyanins was investigated. The enzyme preparations were dosed based on their polygalacturonase activity from 1 to 100 nkat/g of berry mash. The juice yields were determined by weighing, and anthocyanin analyses were performed with HPLC. The bilberry and black currant juice yields increased significantly in enzyme-aided treatments with comparison to control, even with the lowest (1 nkat/g) polygalacturonase dosage. The anthocyanin yield increased by up to 83% for bilberries and up to 58% for black currants in enzyme-aided treatments as compared to control. The results showed that higher polygalacturonase dosage was needed for black currant to achieve the maximal juice and anthocyanin yields than for bilberries. The stability and the profile of extracted anthocyanins were greatly affected by the glycosidase side activities present in the enzyme preparations, which were able to hydrolyze certain anthocyanins to the corresponding aglycones. In addition, the data indicate that anthocyanidin rutinosides were more easily extracted than those of glucosides, which prevailed over the arabinosides and galactosides. Thus, prior to processing it is important to know the intact anthocyanin structures of the raw material, and the activity profile of the enzyme preparation to obtain optimal anthocyanin extractability and enzyme dosage.  相似文献   
55.
Removal of metals and anions from drinking water by ion exchange   总被引:1,自引:0,他引:1  
Five organic and two inorganic ion exchangers were evaluated for the removal of metals and anions from water of two drilled wells. Sodium titanate (CoTreat) and a chelating aminophosphonate resin were the most efficient exchangers in removing transition metals from the total of 1800 bed volumes processed. CoTreat was the best for almost all of the transition metals. The breakthrough level of manganese was below 1% with CoTreat even when its concentration in the feed water was high (1 mg/l). The weak acid cation resin took up transition metals relatively efficiently. Somewhat unexpectedly, the cation exchangers also removed arsenic from water. Arsenic may have been sorbed on iron species, which again was adsorbed and filtered by the exchanger beds. Most of the cation exchangers took up calcium and magnesium at low processing capacities (<400 BV), and the strong base anion resin took up nitrate, bromide and sulphate very efficiently below 700 bed volumes. Neither chloride nor fluoride was taken up by the exchangers tested.  相似文献   
56.
The flavor inclusion powder was prepared by spray drying, using the combined encapsulation method of inclusion by β-cyclodextrin (β-CD) and emulsified by gum arabic (GA). d-Limonene and ethyl n-hexanoate were used as model flavors. The application of high pressure by Microfluidizer to the mixture of flavors and β-CD slurry was an effective means of forming inclusion complex. Flavor retention during spray drying under various compositions of the encapsulants was investigated. The flavor retention using the blended encapsulant was increased by adding GA in the encapsulant. The characteristics of release of encapsulated flavor during storage were evaluated at 50°C and 75% of relative humidity. The release rate of flavor in spray-dried powder depended on kinds of the flavors and composition of the encapsulant. The blending MD and β-CD in the feed liquid decreased the release rate of flavors. The rate of release of flavor was analyzed by Avrami's Equation.  相似文献   
57.
In Western languages, text is traditionally presented in horizontal lines. However, reading of vertically arranged text might be more efficient because of the elimination of horizontal eye movements. We investigated the effect of vertical arrangement upon reading text presented on a computer screen. Even though vertically aligned text was read at a slower rate than horizontally aligned text, the difference was smaller than in previous studies. Analysis of eye-movement data revealed that there were no differences in fixation numbers and numbers of regressions between vertical formats and the standard-text format. But fixation durations were shorter for the standard-text format than for the vertical formats. Taken together, the results indicate that reading vertically presented text from a display device may be nearly as efficient as reading normal horizontal text. Therefore, the fact that text is normally vertically arranged in small-screen devices is not a usability problem.  相似文献   
58.
Wild berries of Hippophaë rhamnoides ssp. sinensis were collected from nine natural growth sites in China in three consecutive years in order to get an overall profile of the sugars, sugar alcohols, fruit acids, and ascorbic acid, and especially of the influence of the latitude and altitude of the growth place on these components. The contents of fructose, glucose, and l-quebrachitol in the berry juice varied in the ranges of 0.01-7.17, 0.05-7.85 and 0.21-1.09 g/100 mL, respectively, those of malic, quinic, and ascorbic acids were 1.55-8.84, 0.07-2.94, and 0.25-1.66 g/100 mL, respectively. The berries from Hebei and Inner Mongolia were characterized by high contents of sugars and l-quebrachitol and low contents of malic acid and ascorbic acid. In contrast, the berries from Sichuan and Qinghai contained lower contents of sugars and higher contents of malic acid and ascorbic acid than the berries from other growth areas. The berries from Sichuan differed considerably from others by the remarkably low contents of sugars and the exceptionally high contents of acids. The contents of fructose, glucose, and total sugar decreased as the altitude increased and as the latitude decreased (p < 0.05). In contrast, the contents of malic acid and ascorbic acid increased as the altitude increased and as the latitude decreased (p < 0.05). The contents of quinic acid and l-quebrachitol correlated strongly and positively with the latitude (p < 0.01).  相似文献   
59.
60.
The behaviour of arsenic (As) derived from tailings was investigated at the Yara Siilinjärvi apatite mine and industrial site in eastern Finland. The study assessed factors influencing the migration and fate of As and compared the anthropogenic As load to the natural geogenic background. Environmental risks related to As were assessed by examining the As concentrations in humus, glacial till, aquatic sediments, groundwater, and surface water. The occurrence and fractionation of As and the presence of secondary precipitates and geochemical transformations in the tailings and in the ambient soil and sediment were evaluated by selective extraction. The water-derived emissions were evaluated by field measurements, hydrogeochemical analysis, and modelling. Results indicate elevated environmental risks due to dust and seepage emissions from the tailings since the concentrations and mobility of As and other potentially harmful elements (PHEs) such as Co, Ni, and Zn were elevated relative to the geogenic background. These elements were mainly associated with Fe (oxy)hydroxides in the soil and their mobility was closely linked to Fe biogeochemistry. Additionally, although the concentrations of As and PHEs were high in the tailings pond and seepage water, they decreased in ambient groundwater and surface water, indicating Fe (oxy)hydroxide stability. This was supported by hydrogeochemical modelling, which indicated precipitation of Fe oxides and hydroxides. According to speciation modelling, As was present mainly as toxic trivalent arsenious acid (H3AsO3) in groundwater and as the less toxic pentavalent As acid (H2AsO4 ? and HAsO4 2?) in surface water.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号