首页 | 官方网站   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   106篇
  免费   11篇
工业技术   117篇
  2023年   4篇
  2022年   1篇
  2021年   11篇
  2020年   5篇
  2019年   3篇
  2018年   7篇
  2017年   6篇
  2016年   8篇
  2015年   4篇
  2014年   5篇
  2013年   7篇
  2012年   8篇
  2011年   12篇
  2010年   9篇
  2009年   7篇
  2008年   2篇
  2007年   2篇
  2006年   5篇
  2005年   3篇
  2002年   1篇
  2001年   2篇
  1999年   1篇
  1998年   1篇
  1997年   1篇
  1991年   1篇
  1988年   1篇
排序方式: 共有117条查询结果,搜索用时 15 毫秒
1.
Food shortages often threaten central Tanzania. Sustainable action adapted to local environmental conditions is desperately needed. In the framework of the TransSEC project, two food value chains in the Dodoma region of Tanzania were inspected in order to make propositions for improvement , spanning from soil preparation to product consumption. Therefore, soil mapping approaches were required to obtain rapid and reliable information. This would enable local farmers to participate in the development of upgrading strategies and extensionists to develop recommendations that take local soil conditions into account. In this study, a combination of participatory soil mapping and gamma ray spectrometry-assisted transect mapping was applied to establish local soil maps of two villages in the Dodoma region. Participatory mapping included key informant interviews, group discussions and transect walks. Local farmers indicated reference profiles for local soil types. Their gamma radiation signatures delivered base information for further soil exploration and soil unit delineation in the field. Finally, high resolution satellite images were used to establish the village soil maps. This approach allows capture of the major soil differences within a village territory and reduction of the costs of chemical analyses. Challenges were soil unit separation with gamma ray spectrometry due to erosional redistribution processes at the surface, correct translation of specific terms from local tongues as well as variable individual soil knowledge of local participants. Ultimately, the combination of local soil knowledge with innovative scientific mapping yielded quick results with sufficient spatial resolution for extension work.  相似文献   
2.
The relationship between Y2O3 content in tetragonal and cubic ZrO2 phases and the shift of the Raman band at ~645/cm was investigated. With increasing Y2O3 content, the 645/cm Raman band position decreases to lower Raman shift values. A fit of x = Y2O3 content in wt% and y = Raman band position in per cm, was found to be valid for low Y2O3‐stabilized t‐ZrO2, t′′‐ZrO2 transition, and fully stabilized c‐ZrO2. Modeling the change in lattice parameters due to the incorporation of Y2O3 in ZrO2 as obtained from Rietveld‐refined XRD data confirms that the peculiar sigmoidal form of the band shift with Y2O3 content is mainly due to a variation of the amount of oxygen vacancies. The resultant method is highly attractive in fields of Y2O3 determination in ZrO2 materials where a fast, spatially resolved, and nondestructive analysis is required.  相似文献   
3.
4.
An appropriate insulin secretion by pancreatic beta-cells is necessary to maintain glucose homeostasis. A rise in plasma glucose leads to increased metabolism and an elevated cytoplasmic ATP/ADP ratio that finally triggers insulin granule exocytosis. In addition to this triggering pathway, one or more amplifying pathways—activated by amino acids or fatty acid—enhance secretion by promoting insulin granule recruitment to, and priming at, the plasma membrane. The aim of this study was to clarify the impact of the mitochondrial respiratory activity on fatty acid-induced insulin secretion that was assessed by an extracellular flux analyzer. Treatment of isolated mouse islets with glucose (20 mM) increased insulin secretion 18-fold and correlated with ATP-synthesizing respiration. Furthermore, oxygen consumption rate (OCR) significantly increased by 62% in response to glucose, whereas the addition of palmitate resulted only in a minor increase of OCR at both 2.8 mM (11%) and 20 mM glucose (21%). The addition of palmitate showed a pronounced increase of coupling efficiency (CE) at 2.8 mM glucose but no further insulin secretion. However, treatment with palmitate at 20 mM glucose increased insulin secretion about 32-fold accompanied by a small increase in CE. Thus, fatty acid induced respiration has a minor impact on insulin secretion. Our data clearly demonstrate that fatty acids in contrast to glucose play a minor role for respiration-mediated insulin secretion. In the presence of high glucose, fatty acids contribute partially to amplifying pathways of insulin secretion by further increasing mitochondrial activity in the islets of Langerhans.  相似文献   
5.
Semi-deciduous forest in the Amazon Basin is sensitive to temporal variation in surface water availability that can limit seasonal rates of leaf and canopy gas exchange. We estimated the seasonal dynamics of gross primary production (GPP) over 3 years (2005–2008) using eddy covariance and assessed canopy spectral reflectance using MODIS imagery for a mature tropical semi-deciduous forest located near Sinop, Mato Grosso, Brazil. A light-use efficiency model, known as the Vegetation Photosynthesis Model (VPM), was used to estimate seasonal and inter-annual variations in GPP as a function of the enhanced vegetation index (EVI), the land surface water index (LSWI), and local meteorology. Our results indicate that the standard VPM was incapable of reproducing the seasonal variation in GPP, primarily because the model overestimated dry-season GPP. In the standard model, the scalar function that alters light-use efficiency (εg) as a function of water availability (Wscalar) is calculated as a linear function of the LSWI derived from MODIS; however, the LSWI is negatively correlated with several measures of water availability including precipitation, soil water content, and relative humidity (RH). Thus, during the dry season, when rainfall, soil water content, and RH are low, LSWI, and therefore, Wscalar, are at a seasonal maximum. Using previous research, we derived new functions for Wscalar based on time series of RH and photosynthetic photon flux density (PPFD) that significantly improved the performance of the VPM. Whether these new functions perform equally well in water stressed and unstressed tropical forests needs to be determined, but presumably unstressed ecosystems would have high cloud cover and humidity, which would minimize variations in Wscalar and GPP to spatial and/or temporal variation in water availability.  相似文献   
6.
In 2 experiments (N?=?111 children), a suggestive technique for interviewing child witnesses called "inviting speculation" was examined. Children were presented with atypical actions for common objects in a clown show. One week later, the children were asked to speculate (e.g., "What else could he have done with the knife?") in a between-subjects design on all or none of the items (Experiment 1) and in a within-subjects design on part of the items (Experiment 2), thereby getting highly probable speculations (e.g., "to cut"). After a 3-week delay, the experimenters found more highly probable but not more other false answers for the experimental items (Experiment 2). After a 5–6-month delay, the rate of (unspecified) false answers increased compared with the baseline (Experiments 1 and 2). The short-term effect is explained by a speculation-as-misinformation assumption, whereas the long-term effect is explained by the use of a metastrategy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
7.
Water-based ionomer dispersions were formed by post-polymerization addition of zirconium species to polymer latices prepared from butyl methacrylate (BMA), butyl acrylate (BA) and acrylic acid (AA) by semicontinuous emulsion polymerization. The mole fraction of AA in the latex particles was kept at 10 mole% in all cases whereas the ratio of BA to BMA was varied. A method was established which allowed zirconium in the form of ammonium zirconium carbonate (AZC) to be successfully introduced into the latices without affecting their colloidal stability. Dynamic light scattering was used to determine average particle size in diluted latices. The structure and properties of cast ionomer films were investigated by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), tensile strength and swelling measurements. Fourier transform infrared spectroscopy (FTIR) was used to investigate the nature of the carboxylate bonding.  相似文献   
8.
Industry 4.0 is a buzzword in current research and in the manufacturing environment. However, despite this limited research has focused on how a company can determine the likely benefits of Industry 4.0 technologies and its influence on the supply chain. Additionally, the aspect of customer experience is gaining significant importance in the new Industry 4.0 supply chain. There is a research gap in implementation strategies of Industry 4.0 concepts for small and medium sized enterprises (SMEs). This paper addresses this gap through an in-depth case study of an SME and highlights how the company can develop competitive advantage. First, a framework was developed to determine the realization of Industry 4.0 predicted benefits for SMEs, which was tested in a case company. Based on input from the case the five-step framework for Industry 4.0 realization is adjusted. It enables practitioners to determine the actual status for their company towards Industry 4.0 realization and thereby functions as a guide for further implementation strategies.  相似文献   
9.
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   
10.
Shielding effects of the surrounding arms and the chain on the encounter probability of reactive sites taking part in the Z-RAFT star polymerization are investigated (a) by use of lattice based Monte Carlo simulations in combination with exact enumeration techniques and (b) by direct simulation applying an off-lattice coarse-grained molecular dynamics method (dissipative particle dynamics, DPD). Making use of the former method the chain-length dependence of the shielding factors is discussed for a broad range of thermodynamic conditions and compared to DPD results for the athermal (good solvent) and theta (bad solvent) case, i.e., for the limiting solvent qualities evaluated. In addition, changes of the size and shape of the reaction partners on approach and penetration are discussed in some detail. The results of both simulation methods fairly well coincide and reveal that shielding is smaller and chain-length dependence less pronounced under theta conditions as compared to good solvent conditions. Experimentally determined polydispersities of polystyrene generated by Z-RAFT star polymerizations in the poor solvent cyclohexane were found to be smaller than with the good solvent toluene, which is in full accordance to the theoretical predictions.  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-23

京公网安备 11010802026262号