全文获取类型
收费全文 | 56篇 |
免费 | 7篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 13篇 |
机械仪表 | 1篇 |
能源动力 | 7篇 |
轻工业 | 9篇 |
水利工程 | 1篇 |
无线电 | 5篇 |
一般工业技术 | 17篇 |
冶金工业 | 2篇 |
原子能技术 | 1篇 |
自动化技术 | 5篇 |
出版年
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 6篇 |
2014年 | 2篇 |
2013年 | 8篇 |
2012年 | 5篇 |
2011年 | 4篇 |
2010年 | 3篇 |
2009年 | 1篇 |
2008年 | 3篇 |
2007年 | 1篇 |
2006年 | 2篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2002年 | 1篇 |
1998年 | 1篇 |
1996年 | 2篇 |
1994年 | 1篇 |
排序方式: 共有63条查询结果,搜索用时 9 毫秒
1.
Thin silicon nitride (Si(1_x)N(x)) films were synthesized without substrate heating by means of reactive argon-ion sputtering of either silicon or a silicon nitride target in the 1000-1500-eV energy range at a nitrogen partial pressure of 1.3 × 10(-2) Pa and with simultaneous nitrogen ion-assisted bombardment in the 300-500-eV low energy range. The extinction coefficient and refractive index of the films were directly dependent on the N(+) ion-to-atom arrival ratio, assisted ion energy, film growth rate, and indicated a correlation with film stoichiometry and disorder. Si(3)N(4) films were obtained for N(+) ion/Si atom arrival ratios from 0.6 to 1.7 and for different Si:N atom arrival rates and had a refractive index as high as 2.04 (633 nm) and a low hydrogen content as indicated by IR spectra. 相似文献
2.
The electrospinning of the biopolymer chitosan (CS) and poly(vinyl alcohol) (PVA) was investigated with 90% acetic acid as the solvent and with different CS/PVA ratios. The long chains of high‐molecular‐weight CS prevented it from forming nanofibers in a high‐voltage field. The treatment of CS under high‐temperature alkali conditions reduced its molecular weight exponentially with the treatment time and caused a reduction of the viscosity consequently. PVA, acting as a plasticizer and accompanied by the alkali‐treated CS of lower viscosity, made the electrospinning of CS/PVA blends possible. The effects of the duration of the alkali treatment on the molecular weight of CS and its viscosity were investigated and optimized. The diameter of the bicomponent nanofiber decreased proportionally with the increase in the CS portion, whereas the surface porosity increased inversely. Fourier transform infrared studies illustrated that the alkali treatment or blending of CS with PVA had no effect on its chemical nature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
3.
All the solar powered cookers presently available in the world market are of the so-called “Reflector Box” type. Despite the fact that they have been presented, for a good few years, to the market and are very simple and low cost they have not managed to establish any meaningful and noticeable presence in a viable commercial sense. This fact is even more in evidence in those markets they are primarily designed for. The reasons to the lack of commercial success for the reflector box type cookers are analysed in some details. The assessment of general features and performance of the reflector box type cooker led to the design of the Fast Response Storage Type Cooker presented in this paper.The new cooker is the result of combination of non-tracking compound parabolic reflector, fast response heat pipes, high-quality and low-cost thermal insulator, low-loss thermal storage battery, glass to metal seals, vacuum technology and bimetal automatic switches. It is capable of storing the solar energy during the day to facilitate cooking during the evenings and nights. A prototype is made and the performance of the elements of the system are presented. It shows how the “waste-energy” of the cooker can be used for other applications. 相似文献
4.
5.
Hadi Valizadeh Mohammad Pourmahmood Javid Shahbazi Mojarrad Mahboob Nemati Parvin Zakeri-Milani 《Drug development and industrial pharmacy》2013,39(4):396-407
The objective of this study was to forecast and optimize the glucosamine production yield from chitin (obtained from Persian Gulf shrimp) by means of genetic algorithm (GA), particle swarm optimization (PSO), and artificial neural networks (ANNs) as tools of artificial intelligence methods. Three factors (acid concentration, acid solution to chitin ratio, and reaction time) were used as the input parameters of the models investigated. According to the obtained results, the production yield of glucosamine hydrochloride depends linearly on acid concentration, acid solution to solid ratio, and time and also the cross-product of acid concentration and time and the cross-product of solids to acid solution ratio and time. The production yield significantly increased with an increase of acid concentration, acid solution ratio, and reaction time. The production yield is inversely related to the cross-product of acid concentration and time. It means that at high acid concentrations, the longer reaction times give lower production yields. The results revealed that the average percent error (PE) for prediction of production yield by GA, PSO, and ANN are 6.84, 7.11, and 5.49%, respectively. Considering the low PE, it might be concluded that these models have a good predictive power in the studied range of variables and they have the ability of generalization to unknown cases. 相似文献
6.
Nowadays, diversion of products distribution from authorised channels to the gray markets is one of the main challenges of manufacturers. Suppose an international supplier distributes the products in several countries with different prices. In parallel importation, there are unauthorised distributers who supply products with a lower price and import them to a higher price market. The problem of parallel importation considering a manufacturer and a competitor is analysed using the game theory approach in this article. We investigate the pricing strategy for manufacturers and the effect of unauthorised distributer on price, market share and profit. We also investigate the performance of different policies in a numerical study and show managerial insights. 相似文献
7.
Alireza Valizadeh Haleh Mikaeili Mohammad Samiei Samad Mussa Farkhani Nosratalah Zarghami Mohammad kouhi Abolfazl Akbarzadeh Soodabeh Davaran 《Nanoscale research letters》2012,7(1):1-14
Ferrite nanoparticles of basic composition Ni0.7-x Zn x Cu0.3Fe2O4 (0.0 ?? x ?? 0.2, x = 0.05) were synthesized through auto-combustion method and were characterized for structural properties using X-ray diffraction [XRD], scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy [FT-IR]. XRD analysis of the powder samples sintered at 600°C for 4 h showed the cubic spinel structure for ferrites with a narrow size distribution from 28 to 32 nm. FT-IR showed two absorption bands (v 1 and v 2) that are attributed to the stretching vibration of tetrahedral and octahedral sites. The effect of Zn doping on the electrical properties was studied using dielectric and impedance spectroscopy at room temperature. The dielectric parameters (??', ????, tan??, and ?? ac) show their maximum value for 10% Zn doping. The dielectric constant and loss tangent decrease with increasing frequency of the applied field. The results are explained in the light of dielectric polarization which is similar to the conduction phenomenon. The complex impedance shows that the conduction process in grown nanoparticles takes place predominantly through grain boundary volume. PACS: 75.50.Gg; 78.20; 77.22.Gm. 相似文献
8.
Effects of alfalfa particle size and specific gravity on chewing activity, digestibility, and performance of Holstein dairy cows 总被引:2,自引:0,他引:2
Teimouri Yansari A Valizadeh R Naserian A Christensen DA Yu P Eftekhari Shahroodi F 《Journal of dairy science》2004,87(11):3912-3924
Two experiments were carried out to test the effects of alfalfa particle size and functional specific gravity (FSG) on chewing activity, digestibility, rumen kinetics, and production of lactating dairy cows fed corn silage based rations. In experiment 1, water-holding capacity (WHC), insoluble dry matter, hydration rate, and FSG changes were determined in alfalfa hay (varying in particle size) and corn silage. Reduction of particle size increased bulk density, FSG, and the rate of hydration, and decreased WHC of alfalfa. In experiment 2, 9 midlactation Holstein dairy cows fed total mixed rations containing 3 sizes of alfalfa hay (with geometric mean 7.83, 4.04, and 1.14 mm) were used in a replicated 3 x 3 Latin square design. The diets contained 20, 20, 35, 7, 7.5, 10, 0.3, 0.1, and 0.1% of DM alfalfa, corn silage, barley, soybean meal, beet pulp, wheat bran, dicalcium phosphate, vitamin premix, and salt, respectively. The geometric means (GM) of rations were 3.34, 2.47, and 1.66 mm in long, medium, and fine alfalfa treatments, respectively. Reduction of particle size increased daily NDF intake (kg), but decreased the proportion of physically effective factor (pef) and physically effective NDF (peNDF) in the ingested rations. Reduction of particle size increased the FSG of rations and intake of DM but reduced digestibility of NDF and ash. Reduction of particle size decreased ruminal mean retention time (RMRT), but increased the ruminal particulate passage rate. Milk and FCM yield were not affected by treatments. The rumen pH, total chewing activity, rumination, eating time, and milk fat were reduced as particle size decreased, but milk protein increased. This study showed that reduction of forage particle size increased bulk density, FSG, and hydration rate of alfalfa and was the most influential factor affecting DMI, milk composition, and chewing behavior. Reduction of forage particle size had minimal impact on digestibility and milk production. 相似文献
9.
Choukali Mohammad Amin Valizadeh Morteza Chehel Amirani Mehdi 《Multidimensional Systems and Signal Processing》2020,31(1):299-315
Multidimensional Systems and Signal Processing - This paper presents a novel algorithm which employs edge information to automatically improve the quality of low contrast images. This algorithm... 相似文献
10.
Marzieh Hajmohammadi Reza Valizadeh Abassali Naserian Mohammad E Nourozi Ramon S Rocha Carlos A F Oliveira 《International Journal of Dairy Technology》2020,73(1):40-45
The composition and occurrence of aflatoxin M1 (AFM1) were investigated in 60 samples of cow's raw milk samples from Razavi Khorasan Province of Iran. Only percentages of milk samples protein, lactose and total solids in samples collected during summer were slightly lower than the Iranian reference values. Compared with summer samples, higher percentages of milk samples components were observed in the winter. The overall mean AFM1 level was 61 ± 8 ng/L, with 24 samples (40%) showing concentrations above the maximum permitted level established in Iran (50 ng/L). Control measures are urgently needed to avoid aflatoxin in milk samples produced in Razavi Khorasan Province. 相似文献