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   63篇
  免费   23篇
  国内免费   1篇
综合类   1篇
化学工业   8篇
金属工艺   1篇
建筑科学   33篇
矿业工程   3篇
能源动力   7篇
轻工业   8篇
水利工程   6篇
石油天然气   5篇
无线电   1篇
一般工业技术   3篇
冶金工业   6篇
原子能技术   1篇
自动化技术   4篇
  2024年   1篇
  2023年   1篇
  2022年   1篇
  2021年   4篇
  2020年   8篇
  2019年   10篇
  2018年   5篇
  2017年   8篇
  2016年   6篇
  2015年   4篇
  2014年   3篇
  2013年   10篇
  2012年   2篇
  2011年   1篇
  2010年   4篇
  2009年   3篇
  2008年   3篇
  2007年   3篇
  2006年   2篇
  2004年   2篇
  2003年   1篇
  2000年   1篇
  1999年   3篇
  1996年   1篇
排序方式: 共有87条查询结果,搜索用时 15 毫秒
1.
Abstract

Many small-scale irrigation systems are characterized by low yields and deteriorating infrastructure. Interventions often erroneously focus on increasing yields and rehabilitating infrastructure. Small-scale irrigation systems have many of the characteristics of complex socio-ecological systems, with many different actors and numerous interconnected subsystems. However, the limited interaction between the different subsystems and their agents prevents learning and the emergence of more beneficial outcomes. This article reports on using Agricultural Innovation Platforms to create an environment in which irrigation scheme actors can engage, experiment, learn and build adaptive capacity to increase market-related offtake and move out of poverty.  相似文献   
2.
Incompatible land use is a major contributor to ecosystem degradation, and is often exacerbated by climate change impacts. We investigate Lake Basotu, Tanzania as a case study where natural lake variability has been affected by agricultural land use. Comparisons between a satellite-derived history of lake surface area, local precipitation records, and corresponding anthropogenic activity show the impacts of agricultural and historical practices. We argue that insufficient consideration to the wider ecological impacts of large agricultural projects has lasting implications. This is particularly true in semi-arid environments where food production demands need to be continuously met. In the future, major conservation strategies should be investigated to maintain the environmental integrity and sustainability of freshwater resources.  相似文献   
3.
隐伏矿产勘查是我国乃至世界现今的主要任务,电阻率测深法和大地电磁测深法是寻找深部矿和隐伏矿的主要工作手段;根据大功率视电阻率测深与音频大地电磁测深在坦桑尼亚某金矿区的实际应用,结合钻孔地质剖面对两者的测量结果反演后进行了对比研究,分析了两种测深方法在构造蚀变岩型金矿上各自的探测效果,研究认为:采用视电阻率测深和音频大地电磁测深可以推测地下构造带电性分布特征、地质结构、构造产状及矿(化)体的赋存空间,音频大地电磁测深对矿区深部构造形态反映效果较好,显示了构造蚀变带的垂向延伸情况;视电阻率测深在反映中、浅部地质体特征方面效果较好,并进一步提高了对大地电磁异常的横向分辨能力,能够为布置钻探工程提供更加充分的依据。  相似文献   
4.
This study employs participatory disaster risk and vulnerability assessment to analyse vulnerability to disasters in informal settlements in Mwanza city, Tanzania. The results show that a plethora of factors – human, physical, social, economic and natural – interact in complex non-linear ways to shape vulnerability to disaster in informal settlements in Mwanza city. The study shows that coping strategies of some individuals in informal settlements reinforce their risks to disaster. For example, the stones that are positioned on weak roof structures for protection may become projectiles in the event of storm: a kind of disaster by design. This quick-fix coping strategy is unlikely to be sustainable.  相似文献   
5.
ABSTRACT

We combine satellite imagery, urban growth modelling, groundwater modelling and hydrogeological field expeditions to estimate the potential impacts in 2050 of rapid urbanization and climate change on groundwater in Arusha, Tanzania, and by extension similar areas in Sub-Saharan Africa. Our analysis suggests that a reduction of groundwater recharge by 30–44% will cause groundwater levels to drop by up to 75 m, mainly due to increased evapotranspiration and to an expansion in paved surface. If this scenario becomes reality, we predict that wells will run dry, creating health, social and environmental risks.  相似文献   
6.
Phosphorus is a major yield limiting nutrient in rice production and yet most soil test methods for predicting P availability to plants have a number of shortcomings especially under flooded conditions. The objective of this study was to evaluate the iron oxide impregnated filter paper (Pi) method for assessing changes in P availability in soils subsequent to flooding and to determine the suitability of the method in assessing P status in paddy soils. The results indicated that available P increases considerably (between 34% and 256%) subsequent to flooding and this affected responsiveness of the soils to P application. Two versions of the Pi method namely; the Pi method used under flooded conditions (Pi-Pf) and Pi strips embedded directly in flooded soils (Pi-Pfe) were effective in assessing P availability in paddy soils. The two Pi methods were better correlated with rice dry matter yield than the traditional soil tests and are hence recommended for use in soil testing under flooded conditions. The tentative critical levels of P for the two procedures under pot conditions were 22 mg/kg for Pi-Pf and 15 mg/strip for Pi-Pef.  相似文献   
7.
太古宙卡哈马(Kahama)绿岩带为坦桑尼亚环维多利亚湖区域八大绿岩带之一,长约100 km,是坦桑尼亚重要的成矿带之一,带上分布有盖塔(Geita)、布鲁杨葫芦(Bulyanuhulu)、高登瑞德(Golden Ridge)、朱比利里夫(Jubilee Reef)等大型、特大型金矿床和众多金矿(化)点,具有很大的找矿前景。芒果(Manangu)金矿体分别赋存于矿区北西部条带状含铁建造(磁铁石英岩)与酸性火山沉积岩(凝灰岩)的上下接触带部位,矿体形态简单,具不规则层状、似层状,金属矿物自然金呈他形粒状,亮金黄色,高反射率,均质性,多属于粒间金。  相似文献   
8.
A food safety management system (FSMS)‐diagnostic instrument was applied in 22 dairy processing companies to analyse the set‐up and operation of core control and assurance activities in view of the risk characteristics of the systems' context. Three clusters of companies were identified differing in levels of set‐up and operation of this FSMS and system outputs, but all operated in a similar moderate‐risk context. Microbiological assessment of products, environmental and hand samples indicated a poor to moderate food safety level. A two stage intervention approach has been proposed to enable commitment and sustainable improvement for the longer term.  相似文献   
9.
In this paper, we examine the intertemporal causal relationship between energy consumption and economic growth in Tanzania during the period of 1971–2006. Unlike the majority of the previous studies, we employ the newly developed autoregressive distributed lag (ARDL)-bounds testing approach by Pesaran et al. [2001. Bounds testing approaches to the analysis of level relationships. Journal of Applied Econometrics 16, 289–326] to examine this linkage. We also use two proxies of energy consumption, namely total energy consumption per capita and electricity consumption per capita. The results of the bounds test show that there is a stable long-run relationship between each of the proxies of energy consumption and economic growth. The results of the causality test, on the other hand, show that there is a unidirectional causal flow from total energy consumption to economic growth and a prima-facie causal flow from electricity consumption to economic growth. Overall, the study finds that energy consumption spurs economic growth in Tanzania.  相似文献   
10.
This study assesses the profitability of selected improved grain storage technologies and the potential impact of their adoption on food security and income of smallholder maize producers in Tanzania. We used on-farm experiment data, time series maize price data, and household survey data to address the objectives. For the improved technologies, we considered Purdue Improved Crop Storage (PICS) bags, metallic silos of different sizes, and polypropylene (PP) bags treated with Actellic Super®. We compared them with PP bags without insecticide treatment as the control. Results show that PICS bags and PP bags plus Actellic Super are profitable in all locations and not significantly different. While the feasible period varies by location, profit is most likely negative if farmers sell their maize in the first two months after harvest and in the last two months before the next harvest. There are mixed results with regards to the profitability of metallic silos; bigger silos are profitable for farmers who have economies of scale to use them while smaller ones are profitable only within the context of higher grain price and bigger seasonal price gap. The results also show that PICS bags (or PP bags plus Actellic Super) are useful to address food security and income objectives among poor rural households whereas metallic silos with bigger storage capacity can increase the income of those farmers who have bigger surplus grain to sale.  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