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   256篇
  免费   13篇
电工技术   6篇
综合类   2篇
化学工业   56篇
金属工艺   3篇
机械仪表   23篇
建筑科学   6篇
矿业工程   1篇
能源动力   11篇
轻工业   21篇
水利工程   2篇
石油天然气   2篇
无线电   10篇
一般工业技术   70篇
冶金工业   17篇
原子能技术   1篇
自动化技术   38篇
  2023年   2篇
  2022年   3篇
  2021年   8篇
  2020年   4篇
  2019年   7篇
  2018年   9篇
  2017年   17篇
  2016年   13篇
  2015年   9篇
  2014年   18篇
  2013年   28篇
  2012年   19篇
  2011年   17篇
  2010年   15篇
  2009年   11篇
  2008年   9篇
  2007年   19篇
  2006年   6篇
  2005年   12篇
  2004年   4篇
  2003年   7篇
  2001年   3篇
  1999年   2篇
  1998年   5篇
  1997年   1篇
  1996年   1篇
  1995年   1篇
  1994年   2篇
  1993年   4篇
  1991年   2篇
  1985年   4篇
  1983年   6篇
  1980年   1篇
排序方式: 共有269条查询结果,搜索用时 31 毫秒
91.
Emotion recognition systems are helpful in human–machine interactions and clinical applications. This paper investigates the feasibility of using 3-channel forehead biosignals (left temporalis, frontalis, and right temporalis channel) as informative channels for emotion recognition during music listening. Classification of four emotional states (positive valence/low arousal, positive valence/high arousal, negative valence/high arousal, and negative valence/low arousal) in arousal–valence space was performed by employing two parallel cascade-forward neural networks as arousal and valence classifiers. The inputs of the classifiers were obtained by applying a fuzzy rough model feature evaluation criterion and sequential forward floating selection algorithm. An averaged classification accuracy of 87.05 % was achieved, corresponding to average valence classification accuracy of 93.66 % and average arousal classification accuracy of 93.29 %.  相似文献   
92.
For the first time, pristine graphene can be controllably crumpled and unfolded. The mechanism for graphene is radically different than that observed for graphene oxide; a multifaced crumpled, dimpled particle morphology is seen for pristine graphene in contrast to the wrinkled, compressed surface of graphene oxide particles, showing that surface chemistry dictates nanosheet interactions during the crumpling process. The process demonstrated here utilizes a spray‐drying technique to produce droplets of aqueous graphene dispersions and induce crumpling through rapid droplet evaporation. For the first time, the gradual dimensional transition of 2D graphene nanosheets to a 3D crumpled morphology in droplets is directly observed; this is imaged by a novel sample collection device inside the spray dryer itself. The degree of folding can be tailored by altering the capillary forces on the dispersed sheets during evaporation. It is also shown that the morphology of redispersed crumpled graphene powder can be controlled by solvent selection. This process is scalable, with the ability to rapidly process graphene dispersions into powders suitable for a variety of engineering applications.  相似文献   
93.
BACKGROUND: We evaluated glycaemic response of a brown rice variant (BR) developed by cross‐breeding. Subjects (n = 9) consumed 50 g carbohydrate equivalents of BR, white rice (WR) and the polished brown rice (PR) in comparison to 50 g glucose reference (GLU) in a cross‐over design. Plasma glucose and insulin at 0, 15, 45, 60, 90, 120 and 180 min were measured and incremental area under the curve (IAUC) and indices for glucose (GI) and insulin (II) calculated. RESULTS: BR compared to PR or WR produced the lowest postprandial glycaemia (GI: 51 vs 79 vs 86) and insulinaemia (II: 39 vs 63 vs 68) irrespective of amylose content (19 vs 23 vs 26.5%). Only BR was significantly different from GLU for both plasma glucose (P = 0.012) and insulin (P = 0.013) as well as IAUCglu (P = 0.045) and IAUCins (P = 0.031). Glycaemic and insulinaemic responses correlated positively (r = 0.550, P < 0.001). Linear trends for IAUCglu and IAUCins indicated a greater secretion of insulin tied in with a greater glycaemic response for WR (r2 = 0.848), moderate for PR (r2 = 0.302) and weakest for BR (r2 = 0.122). CONCLUSION: The brown rice variant had the lowest GI and II values but these advantages were lost with polishing. Copyright © 2011 Society of Chemical Industry  相似文献   
94.
This paper addresses a special class of deterministic dynamic programming problems which can be formulated as a generalized network problem. Because of the similarities between this class of dynamic programming problems and shortest path problems, we are naming it the Generalized Shortest Path problem. A new primal extreme point algorithm and a new special dual algorithm are proposed here. While researchers have presented a variety of algorithms to solve this class of problems, there has been no comuptational analysis of these algorithms. An in-depth computational analysis is performed to determine the most efficient set of rules for implementing the algorithms of this paper.  相似文献   
95.
Packaging is a core technology for the advancement of microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS). We discuss MEMS packaging challenges in the context of functional interfaces, reliability, modeling and integration. These challenges are application-dependent; therefore, two case studies on accelerometers and BioMEMS are presented for an in-depth illustration. Presently, most NEMS are in the exploratory stage and hence a unique path to identify the relevant packaging issues for these devices has not been determined. We do, however, expect the self-assembly of nano-devices to play a key role in NEMS packaging. We demonstrate this point in two case studies, one on a silicon nanowire biosensor, and the other on self-assembly in molecular biology. MEMS/NEMS have the potential to have a tremendous impact on various sectors such as automotive, aerospace, heavy duty applications, and health care. Packaging engineers have an opportunity to make this impact a reality by developing low-cost, high-performance and high-reliability packaging solutions.  相似文献   
96.
97.
Wang CJ  Parviz BA  Lin LY 《Nanotechnology》2008,19(29):295201
We model and demonstrate the behavior of two-dimensional (2D) self-assembled quantum dot (QD) sub-diffraction waveguides. By pumping the gain-enabled semiconductor nanoparticles and introducing a signal light, energy coupling of stimulated photons from the QDs enables light transmission along the waveguide. Monte Carlo simulation with randomized inter-dot separation reveals that the optical gain necessary for unity transfer is 3.1 × 10(7)?m(-1) for a 2D (2?μm length by 500?nm width) array compared to 11.6 × 10(7)?m(-1) for a 1D (2?μm length) given 8?nm diameter quantum dots. The theoretical results are borne out in experiments on 2D arrays by measurement of negligible crosstalk component with as little as 200?nm waveguide separation and is indicative of near-field optical coupling behavior. The transmission loss for 500?nm wide structures is determined to be close to 3?dB/4?μm, whereas that for 100?nm width is 3?dB/2.3?μm. Accordingly, higher pump power and gain would be necessary on the narrower device to create similar throughput. Considering existing nanoscale propagation methods, which commonly use negative dielectric materials, our waveguide shows an improved loss characteristic with comparable or smaller dimensions. Thus, the application of QDs to nanophotonic waveguiding represents a promising path towards ultra-high density photonic integrated circuits.  相似文献   
98.
A number of various organic and inorganic contaminants are commonly present in the technological fluids hindering production quality. Importantly, waste influents must be purified to meet the appropriate environmental standards for their disposal. This paper deals with the development of a treatment technique for technological and wastewater streams allowing the separation of microscopic droplets of water, sand, oil and other organic and inorganic contaminants. Some existing approaches and processes for treatment of contaminated fluids are briefly reviewed and the design of an electromagnetic hydrocyclone separator is presented in this paper. The effect of the main forces on the separation of small‐sized impurities (<10 μm) is analysed. The experimental tests demonstrated the efficiency of the developed apparatus in purifying the industrial wastewaters of the textile dyeing industry.  相似文献   
99.
The effects of extended milling in a stirred media mill and a tumbling mill on the structural changes in hematite have been examined using a combination of particle size analysis, BET surface areas, X-ray diffraction (XRD), thermal (TG and DSC) and FTIR measurements. Rietveld's whole profile fitting based on crystal structure refinement and the Warren-Averbach's method of X-ray line profile analysis were applied to monitor the microstructural evolution of the hematite phase.It is found that the BET surface area, X-ray amorphization phase content and XRD line breadths increase over the specific energy input. The use of stirred media mill exhibits larger surface areas, smaller particle sizes, more XRD line broadening and subsequently greater structural distortions compared to the tumbling mill for a given energy input; although the X-ray amorphous phase content remains unaffected by the grinding environments. The maximum X-ray amorphization degree of about 80 and 95% were calculated at a specific energy of 22,400 and 82,000 kJ/kg in the tumbling and stirred media mills respectively. The maximum specific BET surface area in the stirred media and tumbling milling increases to about 72.5 and 6.8 m2/g after 82,000 and 22,400 kJ/kg energy consumption respectively. As a result of structural refinement during milling, the surface-weighted crystallite size in ground hematite are 17 and 4 nm after consuming 22,400 and 82,000 kJ/kg in the tumbling and stirred media mills respectively, corresponding to the volume-weighted crystallite size of 17 and 11 nm. For the same energy consumption in the mills, in turn, the root mean square strain, , increases to about 4.4 × 10− 3 and 4.9 × 10− 3. The results of the two applied methods are compared and discussed in details.In addition, thermogravimetric analysis of the wet ground samples reveals that the TG curves represent two weight loss steps. A weight loss is observed around 100 °C in the sample which is attributed to the removal of adsorbed water due to the wet milling operations. A strong weight loss step starting from 100 to 400 °C is attributed to surface/bulk dehydroxilation of iron hydroxides. The weight loss increases with extending of the milling. In contrast, the dry milled samples yield negligible weight losses comparing with the wet ground samples.  相似文献   
100.
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