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   113篇
  免费   11篇
综合类   1篇
化学工业   12篇
金属工艺   2篇
机械仪表   6篇
建筑科学   3篇
能源动力   11篇
轻工业   11篇
水利工程   2篇
石油天然气   5篇
无线电   17篇
一般工业技术   28篇
冶金工业   13篇
自动化技术   13篇
  2023年   2篇
  2022年   3篇
  2021年   2篇
  2020年   5篇
  2019年   4篇
  2018年   2篇
  2017年   6篇
  2016年   8篇
  2015年   1篇
  2014年   7篇
  2013年   8篇
  2012年   8篇
  2011年   7篇
  2010年   8篇
  2009年   5篇
  2008年   5篇
  2007年   5篇
  2006年   4篇
  2005年   4篇
  2004年   4篇
  2003年   5篇
  2000年   1篇
  1999年   2篇
  1998年   6篇
  1997年   3篇
  1996年   3篇
  1995年   1篇
  1994年   2篇
  1993年   1篇
  1988年   1篇
  1980年   1篇
排序方式: 共有124条查询结果,搜索用时 15 毫秒
61.
Many methods have been described for preventing or reducing postoperative adhesions. In this work, we evaluated the effectiveness of Budesonide in combination with SprayGel in a reducing postoperative adhesion in rats as the model. Cecal abrasion was achieved in 60 male Sprague-Dawley rats, by brushing and by applying 70% alcohol. The rats were separated into six groups and treated with six solutions (Group I – saline; II – Budesonide 50?μg; III – Budesonide 250?μg; IV – SprayGel; V and VI – SprayGel?+?Budesonide 50 and 250?μg). Serum Budesonide, glucose, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and blood urea nitrogen levels were measured at postoperative day (POD) 2 and 14. The rats were killed on POD 14, and intra-abdominal adhesion formation was scored. Histopathological samples were obtained from the cecum and terminal ileum to evaluate microscopic adhesion formation. Our results showed that Group VI had both the minimum macroscopic adhesion score and the minimum microscopic score. All other groups had significantly lower microscopic adhesion scores than Group I. However, there was no statistical significance among any other groups. Serum AST levels of Group III were significantly higher than in Groups I, II, IV, and V (p?<?0.046). Serum AST levels of Group III on POD 14 were also significantly higher than that of all other groups (p?<?0.02). On POD 14, there was no Budesonide in the sera of Groups II and V. However, Groups III and VI had trace amounts of Budesonide (0.009 and 0.007?μg, respectively). In conclusion, we have showed that the effect of Budesonide is dosedependent. Both anti-adhesive and hepatotoxic side effects of Budesonide increased as the dose increased. Combining Budesonide with SprayGel synergistically increased the anti-adhesive benefits and prevented hepatotoxicity from the slower release of Budesonide.  相似文献   
62.
We propose and demonstrate the fabrication of flexible, freestanding films of InP/ZnS quantum dots (QDs) using fatty acid ligands across very large areas (greater than 50 cm × 50 cm), which have been developed for remote phosphor applications in solid-state lighting. Embedded in a poly(methyl methacrylate) matrix, although the formation of stand-alone films using other QDs commonly capped with trioctylphosphine oxide (TOPO) and oleic acid is not efficient, employing myristic acid as ligand in the synthesis of these QDs, which imparts a strongly hydrophobic character to the thin film, enables film formation and ease of removal even on surprisingly large areas, thereby avoiding the need for ligand exchange. When pumped by a blue LED, these Cd-free QD films allow for high color rendering, warm white light generation with a color rendering index of 89.30 and a correlated color temperature of 2298 K. In the composite film, the temperature-dependent emission kinetics and energy transfer dynamics among different-sized InP/ZnS QDs are investigated and a model is proposed. High levels of energy transfer efficiency (up to 80%) and strong donor lifetime modification (from 18 to 4 ns) are achieved. The suppression of the nonradiative channels is observed when the hybrid film is cooled to cryogenic temperatures. The lifetime changes of the donor and acceptor InP/ZnS QDs in the film as a result of the energy transfer are explained well by our theoretical model based on the exciton-exciton interactions among the dots and are in excellent agreement with the experimental results. The understanding of these excitonic interactions is essential to facilitate improvements in the fabrication of photometrically high quality nanophosphors. The ability to make such large-area, flexible, freestanding Cd-free QD films pave the way for environmentally friendly phosphor applications including flexible, surface-emitting light engines.  相似文献   
63.
Balci O  Kocabas C 《Nanotechnology》2012,23(24):245202
We have studied the high frequency performance limits of single-walled carbon nanotube (SWNT) transistors in the diffusive transport regime limited by the acoustic phonon scattering. The relativistic band structure of single-walled carbon nanotubes combined with the acoustic phonon scattering provides an analytical model for the charge transport of the radio frequency transistors. We were able to obtain the intrinsic high frequency performance such as the cut-off frequency and the linearity of the SWNT transistors. We have extended our model to include transistors based on arrays of SWNTs. The effect of electrostatic screening in a dense array of SWNTs on the cut-off frequency is studied.  相似文献   
64.
One technique that may facilitate group brainstorming is decomposition of the task so that categories of the problem are considered one at a time rather than simultaneously (A. R. Dennis, J. S. Valacich, T. Connolly, & B. E. Wynne, 1996). Two studies examined this possibility for both solitary and interactive brainstorming in which major categories of a brainstorming problem were presented simultaneously or sequentially. In the 1st study, participants in the sequential presentation condition generated more ideas than did those in the simultaneous condition in both the individual and the group conditions. In the 2nd study, individuals exposed to either a high number or low number of idea categories demonstrated enhanced performance. Simulations of the data demonstrated that the results were consistent with an associative memory model of the idea generation process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
65.
66.
The quarantine region scheme (QRS) is introduced to defend against spam attacks in wireless sensor networks where malicious antinodes frequently generate dummy spam messages to be relayed toward the sink. The aim of the attacker is the exhaustion of the sensor node batteries and the extra delay caused by processing the spam messages. Network-wide message authentication may solve this problem with a cost of cryptographic operations to be performed over all messages. QRS is designed to reduce this cost by applying authentication only whenever and wherever necessary. In QRS, the nodes that detect a nearby spam attack assume themselves to be in a quarantine region. This detection is performed by intermittent authentication checks. Once quarantined, a node continuously applies authentication measures until the spam attack ceases. In the QRS scheme, there is a trade-off between the resilience against spam attacks and the number of authentications. Our experiments show that, in the worst-case scenario that we considered, a not quarantined node catches 80 percent of the spam messages by authenticating only 50 percent of all messages that it processes.  相似文献   
67.
The aim of this study is to evaluate the performance of horizontal GSHP by considering various system parameters for winter climatic condition of Bursa, Turkey. For this purpose, a previously used experimental facility on cooling cycle [Coskun S, Pulat E, Unlu K, Yamankaradeniz R. Experimental performance investigation of a horizontal ground source compression refrigeration machine. International Journal of Energy Research 2008; 32: 44–56] was modified for the heating cycle. Soil thermal conductivity estimation was expanded and discussed. Preliminary numerical temperature distribution around GHE pipes was obtained. Tests were performed under laboratory conditions for space heating from December 2004 to March 2005. Variations of entering and leaving antifreeze solution temperatures, extracted heat from ground and rejected heat to the test room, super heat rate in evaporator and subcooling rate in condenser, total power consumption and coefficient of performance (COP) values for both the entire system and only heat pump unit (HPU) were obtained. Effect of outdoor temperature on system capacities and COP values with respect to outdoor air and mean soil temperatures were also presented. The COP of the entire system and HPU lie between 2.46–2.58 and 4.03–4.18, respectively. GSHP system was compared to conventional heating methods in the economical analysis and it was shown that the GSHP system is more cost effective than the all other conventional heating systems.  相似文献   
68.
Fluorescent microscopy and flow cytometry are widely used tools in biomedical sciences. Cost-effective translation of these technologies to remote and resource-limited environments could create new opportunities especially for telemedicine applications. Toward this direction, here we demonstrate the integration of imaging cytometry and fluorescent microscopy on a cell phone using a compact, lightweight, and cost-effective optofluidic attachment. In this cell-phone-based optofluidic imaging cytometry platform, fluorescently labeled particles or cells of interest are continuously delivered to our imaging volume through a disposable microfluidic channel that is positioned above the existing camera unit of the cell phone. The same microfluidic device also acts as a multilayered optofluidic waveguide and efficiently guides our excitation light, which is butt-coupled from the side facets of our microfluidic channel using inexpensive light-emitting diodes. Since the excitation of the sample volume occurs through guided waves that propagate perpendicular to the detection path, our cell-phone camera can record fluorescent movies of the specimens as they are flowing through the microchannel. The digital frames of these fluorescent movies are then rapidly processed to quantify the count and the density of the labeled particles/cells within the target solution of interest. We tested the performance of our cell-phone-based imaging cytometer by measuring the density of white blood cells in human blood samples, which provided a decent match to a commercially available hematology analyzer. We further characterized the imaging quality of the same platform to demonstrate a spatial resolution of ~2 μm. This cell-phone-enabled optofluidic imaging flow cytometer could especially be useful for rapid and sensitive imaging of bodily fluids for conducting various cell counts (e.g., toward monitoring of HIV+ patients) or rare cell analysis as well as for screening of water quality in remote and resource-poor settings.  相似文献   
69.
The effects of dietary supplementation of a commercial probiotic (BioPlus 2B) on daily feed consumption, egg yield, egg weight, specific gravity, body weight, feed conversion ratio, serum and egg yolk cholesterol, and serum trigylceride in layer hens were investigated. In 12 replicates, 480 27-week-old Brown-Nick layers were fed with diets containing 0, 250, 500 or 750 mg kg(-1) probiotic for 90 days. When compared with the controls, supplementation of 250, 500 and 750 mg kg(-1) probiotic increased egg production, but decreased the damaged egg ratio (p < 0.05), egg yolk cholesterol and serum cholesterol (p < 0.001) levels. In addition, serum triglyceride levels were reduced by using 500 and 750 mg kg(-1) probiotic supplementation (p < 0.001). Feed conversion ratios were positively affected by supplementation of 250 and 500 mg kg(-1) probiotic compared with controls (p < 0.05). There was no statistically significant difference between the control and all treatment groups on feed consumption, egg weight, specific gravity, body weight, and egg yolk weight.  相似文献   
70.

Advanced vehicular control technologies rely on accurate speed prediction to make ecological and safe decisions. This paper proposes a novel stochastic speed prediction method for connected vehicles by incorporating a Bayesian network (BN) and a Back Propagation (BP) neural network. A BN model is first designed for predicting the stochastic vehicular speed in a priori. To improve the accuracy of the BN-based speed prediction, a BP-based predicted speed error compensation module is constructed by formulating a mapping between the predicted speed and whose corresponding prediction error. In the end, a filtering algorithm is developed to smoothen the compensated stochastic vehicular speed. To validate the workings of the proposed approaches in experiments, two typical scenarios are considered: one predecessor vehicle in a double-vehicle scenario and two predecessor vehicles in a multi-vehicle scenario. Simulation results under the considered scenarios demonstrate that the proposed BN-BP fusion method outperforms the BN-based method with respect to the root mean square error, standardized residuals, R-squared, and the online prediction time of proposed fusion prediction can satisfy a real-time application requirement. The main highlighted contributions of this article are threefold: (1) We put forward an improved BN method, which is combined with a BP neural network, to construct a stochastic vehicular speed prediction method under connected driving; (2) different from existing methods, a unique interconnected framework that consists of a stochastic vehicular speed prediction module, a compensation module, and a speed smoothing module is proposed; (3) extensive simulation studies based on a set of evaluation metrics are illustrated to reveal the advantages and merits of the proposed approaches.

  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