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   108篇
  免费   2篇
电工技术   1篇
化学工业   17篇
金属工艺   4篇
机械仪表   3篇
建筑科学   2篇
能源动力   8篇
轻工业   14篇
无线电   14篇
一般工业技术   23篇
冶金工业   13篇
自动化技术   11篇
  2022年   5篇
  2021年   6篇
  2020年   6篇
  2018年   3篇
  2017年   4篇
  2016年   7篇
  2015年   3篇
  2014年   5篇
  2013年   13篇
  2012年   3篇
  2011年   2篇
  2010年   1篇
  2009年   4篇
  2008年   1篇
  2007年   2篇
  2006年   1篇
  2005年   2篇
  2004年   2篇
  2003年   1篇
  1999年   1篇
  1998年   4篇
  1997年   5篇
  1996年   2篇
  1995年   4篇
  1994年   2篇
  1993年   2篇
  1992年   3篇
  1991年   1篇
  1989年   1篇
  1987年   2篇
  1986年   4篇
  1985年   2篇
  1984年   1篇
  1983年   1篇
  1981年   1篇
  1978年   1篇
  1974年   1篇
  1969年   1篇
排序方式: 共有110条查询结果,搜索用时 15 毫秒
1.
2.
The maximum acceptable weights of lift (MAWL) of obese and non-obese participants were empirically investigated. Three obesity levels were considered: non-obese (18.5 kg/m(2)< or= body mass index (BMI)or= 40 kg/m(2)). Ten male and 10 female participants were recruited for each obesity level. The participants determined their MAWL for 18 different lifting task conditions (six lifting frequencies x three lifting heights). An analysis of variance (ANOVA) was conducted to determine the effects of obesity level, gender, lifting height, lifting frequency and their interactions on MAWL. Overall, the ANOVA results indicated that obesity does not reduce MAWL, and thus, suggested that the existing MAWL data can be used to accommodate both general and obese workers. However, further studies based on the biomechanical and physiological approaches are required to provide more complete understanding of obesity effects on lifting tolerance limits.  相似文献   
3.
4.
The evolution of luminescent materials has witnessed rapid advancement in research and development. Solid inorganic light-emitting materials or phosphors are the optoelectronic material of the 21st century because of their power-efficient potential over various illumination sources, eco-friendliness and resourceful display perspectives. The inorganic phosphors have been extensively explored to meet the demand of low voltage stimulated lighting sources owing to increased global energy consumption. Due to environmental friendliness, advantages long lifetime, lower energy consumption, reliability and high luminous efficiency, modern white light-emitting diodes (WLEDs) have replaced less effective incandescent and mercury-enclosing conventional fluorescent lighting sources. This review highlights the developments in preparation, luminescence and potential perceptions of rare-earth activated phosphors for solid-state lighting technologies. The role of RE ions as an activator as well as a sensitizer in doped materials and possible transitions within their energy levels are reviewed in detail. The paper reviews the substantial influence of host lattices such as aluminate, oxide, phosphate, silicate, sulfide, etc on the optical transitions of doped RE ions. Studies on the advancement into the design of novel phosphors are very crucial as they will provide an opportunity to boom prospects in the course of promising applications. The sustainable energy facilities include clean technologies providing a cheaper lighting source which can produce significant indirect economic benefits via limiting the deforestation and use of scrubbing technology to mitigate air pollution.  相似文献   
5.
Renewable Energy (RE) sources form a minuscule portion of India’s overall Energy consumption today. India continues to rely on fast depleting fossil fuel and expensive Oil imports to satisfy the energy demands of the economy. But this is hardly sustainable and India has to quickly get RE sources to play a major role in servicing the energy needs of its population. Despite the best efforts the adoption of RE sources by consumer communities in India is patchy. This article will focus on what needs to be done to create a pull from the market for RE sources, by looking at Consumer Behaviour literature available in the area of Diffusion of Innovation[1]. Demand for RE sources from consumer communities must reach a tipping point[4] quickly; for the sector to take-off on its own and become a self-sustaining business.  相似文献   
6.
Seed kernels of two cultivars (Chausa and Dusheri) of mango (Mangifera indica) were analysed for chemical composition, lipid classes, fatty acid composition, amino acid profile and chemical evaluation of protein quality. The seed kernels constituted about 18% of the total fruit and had 5% protein, 6–7% crude fat, 0.19–0.44% tannins, iodine value of 34–44 and saponification number 202–213. Oleic acid (42%) and stearic acid (39%) were the principal fatty acids in the oil. The in vitro digestibility was low in these cultivars, possibly due to the presence of tannins. Sulphur-containing amino acids (methionine+cystine) and isoleucine were the limiting amino acids in Chausa and Dusheri, respectively. The essential amino acid index and protein quality index were high, thus indicating the good quality of the protein in mango seed kernel.  相似文献   
7.
The significance of different variables viz. temperature, time and solvent at constant power in microwave‐assisted extraction (MAE) process of ginger was studied and compared with conventional method. Aqueous ethanol (50%) provided higher yields of extract as well as the highest release of total polyphenols (TPP) than alcoholic solvents. The reason could be the high dielectric constant of aqueous ethanol as compared to alcohols. Microwave heating being a volumetric process, an exposure time of 1 min was found to be sufficient. The better penetration of microwaves and greater solubility at higher temperature resulted in higher yield of TPP and [6]‐gingerol. The resultant extract showed higher radical scavenging activity (RSA) values. Thus, MAE allowed higher recoveries compared to conventional extraction process, with improvement in the quantity and quality of extract in very short period of time.  相似文献   
8.
A finite element heat transport program has been modified to model the thermal behavior for a cylindrically symmetric salt gradient polar pond of the Rabl-Nielsen type. In this model transient phenomena as well as steady state behavior can be studied. Results are presented for a model of the solar pond at the University of New Mexico and are compared with actual measurements.  相似文献   
9.
Ca (or Sr)TiO3:Eu3+, M (Li+ or Na+ or K+) and CaTiO3:Pr3+, M (Li+ or Na+ or Ag+ or K+ or Gd3+ or La3+) powders were prepared by combustion synthesis method and the samples were further heated to ~1000 °C to improve the crystallinity. The structure and morphology of materials were examined by X-ray diffraction (XRD) and a scanning electron microscopy (SEM). The morphologies of SrTiO3:Eu3+, CaTiO3:Eu3+ or CaTiO3:Pr3+ powders co-doped with other metal ions were very similar. Small and coagulated particles of nearly cubical shapes with small size distribution having smooth and regular surface were formed. Photo-luminescence spectra of CaTiO3:Pr3+ and co-doped either with Li+, Na+, K+, Ag+, La3+ or Gd3+ ions showed red emissions at 613 nm due to the 1D2  3H4 transition of Pr3+. The variation of intensity of emission peak with different co-doping follows the order: K+ > Ag+ > Na+ > Li+ > La3+ > Gd3+. The characteristic emissions of CaTiO3:Eu3+ lattices had strong emission at 614 and 620 nm for 5D0  7F2 with other weak transitions observed at 580, 592, 654, 705 nm for 5D0  7Fn transitions where n = 0, 1, 3, 4 respectively in all host lattices. Photoluminescence intensity in SrTiO3:Eu3+ is more than CaTiO3:Eu3+ lattices. A remarkable increase of photoluminescence intensity (in 5D0  7F2 transition) was observed if co-doped with Li+ ions in CaTiO3:Eu3+ and SrTiO3:Eu3+.  相似文献   
10.
The present work focused on the glycerolysis of fatty acid methyl esters. The aim was to develop and test a kinetic model that could be used to reliably simulate different process alternatives for this reaction. A prerequisite was the identification and characterization of the factors that affect the reaction kinetics. Experiments were carried out in a batch reactor with and without forced removal of methanol, which is one of the reaction products. Concentrations of all components in the two-phase system were measured. It was found that the methanol concentration has a strong effect on the reaction rate and equilibrium conversion. Near-complete conversions were obtained by stripping methanol with an inert gas. The glycerol concentration in the ester phase was found to increase as the reaction proceeds, which also accelerates the reaction. Effects of mass transfer on the reaction rate were not found to control the reaction rate under well-agitated conditions. A semi-empirical model was used to simulate the reaction. The results from the semi-empirical model show good agreement with experimental results.  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