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   70篇
  免费   3篇
化学工业   13篇
金属工艺   2篇
机械仪表   1篇
建筑科学   4篇
能源动力   3篇
轻工业   11篇
水利工程   4篇
石油天然气   1篇
无线电   3篇
一般工业技术   15篇
冶金工业   6篇
自动化技术   10篇
  2023年   2篇
  2022年   2篇
  2021年   4篇
  2020年   3篇
  2019年   4篇
  2018年   2篇
  2017年   2篇
  2015年   1篇
  2014年   6篇
  2013年   7篇
  2012年   3篇
  2011年   7篇
  2010年   3篇
  2009年   5篇
  2008年   2篇
  2007年   2篇
  2006年   3篇
  2005年   3篇
  2004年   3篇
  2003年   2篇
  2000年   1篇
  1999年   2篇
  1989年   1篇
  1985年   1篇
  1980年   1篇
  1979年   1篇
排序方式: 共有73条查询结果,搜索用时 15 毫秒
1.
We estimated the tree structural variables (density, frequency and basal area) of true mangroves and soil variables like particle size distribution, carbon, available nitrogen and phosphorus, sulphur, nutrient cations (K, Na, Ca, Mg) of Cochin mangroves and examined the relationship between vegetation and environment. The study sites were classified as seaward fringe, riverine and interior. Of the thirteen true mangrove species present, Avicennia officinalis, Sonneratia caseolaris and Excoecaria agallocha showed higher Importance Value Index. The mean stem density varied from 80 to 25,000 no./ha and basal area from 0.1 to 39.68 m2/ha. Seaward mangroves showed maximum stand basal area and biomass production while riverine exhibited maximum density. Maturity Index value of Cochin mangroves revealed a very low degree of structural maturity. Interior mangroves were characterized by silty soil with higher nutrient concentrations. Principal component analysis of soil data revealed that the major factors influencing mangrove vegetation were soil texture, nutrients, salinity and oxidation–reduction potential. The stem density and basal area of different species correlated highly with soil nutrients and texture (p < .001) while salinity showed negative correlations with vegetation characteristics. The data generated in the study would be fundamental in site‐specific management and conservation efforts of these degrading mangroves.  相似文献   
2.
本文简述了我国锌工业生产、消费和再生锌工业发展的现状,指出了我国再生锌工业发展缓慢,技术装备水平低,企业生产规模小等问题。提出了建立规范化的管理制度,在政策上鼓励发展废锌材料的回收利用,加速我国废锌材料的回收利用程度。  相似文献   
3.
The present paper evaluates the use of software agents to identify relevance of information, called awareness. This evaluation is based on existing policies and scenarios in the context of wireless communication of a hospital in Norway. The study is to address the lack of literature for experimental studies on a method to employ software agents for awareness identification. Research in computer supported cooperative work indicates the significant contributions of software agents to assist individuals. There are bodies of work that show awareness provides the means for software agents in which effective cooperation can take place. In addition, the role of the methods to identify awareness is emphasized in the literature of both computer supported cooperative work and software agents. This paper explains a step-wise process, called Policy-based Awareness Management, which allows agents to use policies as a source to identify awareness and thus change their behaviors accordingly. The contribution of this method is based on the concepts proposed by the logic of general awareness. The present study applies Directory Enabled Networks-next generation as the policy structure for the method. The paper evaluates the process via its application to identify the relevance of information in wireless communication scenarios in a hospital. The present study conducts observations, interviews and discussions on the wireless communication system of the hospital to identify the different scenarios happening in the system. The paper presents a set of simulations on these scenarios and concludes that the method is effective and cost-efficient.  相似文献   
4.
The field of computer supported cooperative work aims at providing information technology models, methods, and tools that assist individuals to cooperate. The presented paper is based on three main observations from literature. First, one of the problems in utilizing information technology for cooperation is to identify the relevance of information, called awareness. Second, research in computer supported cooperative work proposes the use of agent technologies to aid individuals to maintain their awareness. Third, literature lacks the formalized methods on how software agents can identify awareness. This paper addresses the problem of awareness identification. The main contribution of this paper is to propose and evaluate a formalized structure, called Policy-based Awareness Management (PAM). PAM extends the logic of general awareness in order to identify relevance of information. PAM formalizes existing policies into Directory Enabled Networks-next generation structure and uses them as a source for awareness identification. The formalism is demonstrated by applying PAM to the space shuttle Columbia disaster occurred in 2003. The paper also argues that efficacy and cost-efficiency of the logic of general awareness will be increased by PAM. This is evaluated by simulation of hypothetical scenarios as well as a case study.  相似文献   
5.
Effect of ultrasound pretreatment on yield and functional properties of taro starch was investigated. A three-factor two-level factorial design was employed with treatment time (5 and 10 min), treatment cycle (0.5 and 1), and amplitude of ultrasound (50 and 100 %). Starch yield from ultrasonic treatment varied from 17.45 to 18.97 % compared to 15.29 % in conventional method. The highest yield of 18.97 % was obtained with treatment time 10 min, treatment cycle 0.5, and amplitude 50 %. A significant increase in swelling, solubility, pasting, and texture properties of the ultrasonically extracted starch was observed. A slight decrease in clarity of the starch pastes was also observed after ultrasonic pretreatment, but the differences were not much significant. Freeze-thaw stability of the ultrasonically extracted starches was found to be better compared to starch extracted using conventional method, making them suitable for foods subjected to refrigeration. The whiteness of the ultrasonically extracted starch powders was lower compared to conventionally extracted starch, but the differences were not statistically significant.  相似文献   
6.
BACKGROUND: An experiment was conducted to study the effects of boiling water, methanol and ethanol extracts (0, 0.25 and 0.50 mL) of seeds of Foeniculum vulgare (fennel), flower buds of Syzygium aromaticum (clove), bulbs of Allium sativum (garlic), bulbs of Allium cepa (onion) and roots of Zingiber officinalis (ginger) on rumen methanogenesis, fibrolytic enzyme activities and fermentation characteristics in vitro. RESULTS: Ethanol and methanol extracts of fennel, clove and garlic at 0.50 mL and clove at 0.25 mL inhibited (P < 0.05) methane production. Carboxymethylcellulase activity was reduced (P < 0.05) by ethanol and methanol extracts (0.50 mL) of fennel and clove (0.25 and 0.50 mL). The extracts of clove reduced (0.25 and 0.50 mL) xylanase and acetylesterase activities, and the fennel extract (0.50 mL) reduced (P < 0.05) xylanase activity. However, the extracts of garlic (0.50 mL) increased (P < 0.05) acetylesterase activity. Concentrations of volatile fatty acids were reduced (P < 0.05) by the extracts of garlic and onion. The extracts of garlic caused a decrease (P < 0.05) in acetate:propionate ratio (A:P) at 0.50 mL, whereas A:P was increased (P < 0.05) by the inclusion of 0.50 mL extracts of clove. Methanol and ethanol extracts of clove decreased (P < 0.05) in vitro organic matter degradability. Extracts (0.50 mL) of clove decreased (P < 0.05) the numbers of total protozoa, small entodiniomorphs and holotrichs, whereas extracts of onion, ginger and garlic enhanced (P < 0.05) protozoal numbers (both entodiniomorphs and holotrichs). CONCLUSION: Ethanol and methanol extracts of fennel and garlic have potential to inhibit rumen methanogenesis without adversely affecting rumen fermentation. Copyright © 2009 Society of Chemical Industry  相似文献   
7.
Friction composites based on several combinations of flyash and inorganic mineral rock fibres such as lapinus™ fibre were fabricated, characterised and tribo-evaluated. The tribo-performance in terms of their friction-fade and friction-recovery behaviour has been rigorously evaluated while synchronously taking into account of the in situ braking induced temperature rise in the disc at the braking interface on a Krauss friction testing machine following pulse velocity wave (PVW) 3212 norms as per the Economic Commission for Europe (ECE) regulations. The fade behaviour has been observed to be highly dependent on the combination of flyash–lapinus fibre e.g. fade remained maximum (45%) in the composite with the highest amount of lapinus fibre content and lowest amount of flyash whereas the frictional fluctuations in terms of μmax − μmin has been observed to be higher in case of low flyash–high lapinus fibre combination. The recovery response seemed unaffected by the disparity of ingredients and remained consistently stable within the range of 112 ± 2%. The analysis of friction and wear performance has revealed that flyash along with lapinus fibre provide thermo-mechanical stability and overall mechanical integrity to the system causing reduction in friction-fade whereas wear was found to be more recovery-controlled and less fade controlled. Worn surface morphology investigation using SEM has been carried out which has revealed that the interplay of flyash–lapinus combination and topographical attributes vis-a-vis dynamics of contact patches (formation–destruction) largely influence the friction and wear performance of such composites.  相似文献   
8.
We demonstrate a new and simple route to fabricate highly dense arrays of hexagonally close packed inorganic nanodots using functional diblock copolymer (PS-b-P4VP) thin films. The deposition of pre-synthesized inorganic nanoparticles selectively into the P4VP domains of PS-b-P4VP thin films, followed by removal of the polymer, led to highly ordered metallic patterns identical to the order of the starting thin film. Examples of Au, Pt and Pd nanodot arrays are presented. The affinity of the different metal nanoparticles towards P4VP chains is also understood by extending this approach to PS-b-P4VP micellar thin films. The procedure used here is simple, eco-friendly, and compatible with the existing silicon-based technology. Also the method could be applied to various other block copolymer morphologies for generating 1-dimensional (1D) and 2-dimensional (2D) structures.  相似文献   
9.
Ensemble Methods are proposed as a means to extendbiAdaptive One‐Factor‐at‐a‐Time (aOFAT) experimentation. The proposed method executes multiple aOFAT experiments on the same system with minor differences in experimental setup, such as ‘starting points’. Experimental conclusions are arrived at by aggregating the multiple, individual aOFATs. A comparison is made to test the performance of the new method with that of a traditional form of experimentation, namely a single fractional factorial design which is equally resource intensive. The comparisons between the two experimental algorithms are conducted using a hierarchical probability meta‐model and an illustrative case study. The case is a wet clutch system with the goal of minimizing drag torque. In this study, the proposed procedure was superior in performance to using fractional factorial arrays consistently across various experimental settings. At the best, the proposed algorithm provides an expected value of improvement that is 15% higher than the traditional approach; at the worst, the two methods are equally effective, and on average the improvement is about 10% higher with the new method. These findings suggest that running multiple adaptive experiments in parallel can be an effective way to make improvements in quality and performance of engineering systems and also provides a reasonable aggregation procedure by which to bring together the results of the many separate experiments. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
10.
Patterned media for future ultrahigh-density magnetic data storage can be prepared by electrodeposition into ordered arrays of nanostructured templates. Diblock copolymer templates have been proposed as a promising alternative to alumina templates. They possess smaller feature sizes than alumina and thereby allow for higher storage densities. Templates with pore diameters of ∼8 nm have been fabricated by dip-coating a conducting substrate into a solution of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) and 2-(4′-hydroxybenzeneazo) benzoic acid (HABA). A vapor annealing step was interposed for better ordering. The pores are opened by dissolving the HABA from the supramolecular assembly and afterwards filled by electrodeposition.Fe-Pt and Co-Pt alloys are the materials of choice for filling the pores due to their hard magnetic properties like high coercivity and anisotropy. Co-rich Co80Pt20 was chosen for this study because it does not require post annealing as in the case of ordered L10 CoPt or FePt. Continuous films have been deposited in order to identify the optimum deposition conditions and the influence of deposition current density on chemical composition, growth morphology, and structural and magnetic properties has been studied systematically. The first results on templates electrochemically filled with Co-Pt are presented together with an analysis of their magnetic properties.  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