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321.
重庆城口黑色岩系以往资料的分析与评价   总被引:2,自引:0,他引:2       下载免费PDF全文
追述了1999年与2000年对城口黑色岩系中Pt的分析数据出现了2~3个数量级的差异;分析了以往地质工作和分析工作存在的问题,进而剖析了分析数据出现2~3个数量级差异的原因,最后指出了目前黑色岩系成矿性研究存在的主要问题.  相似文献   
322.
In an old, species-rich hay meadow in Varalds?y in Hardanger, the only known remaining managed site of its kind in West Norway, the moss layer is increasing in thickness in some places. Thick moss is associated with a high cover of monocotyledons, while a low cover of monocotyledons is associated with high numbers of herbs, including vulnerable species, which mainly occur in herb-rich areas. The increase in moss is probably caused by a reduction in both traditional means of moss removal and in sheep trampling and it may represent a potential threat to plant species diversity in traditionally managed hay meadows in the region. In order to increase the area of open, species-rich hay meadows, and thus the potential population sizes for indicator species of traditional management, increased grazing intensity (back to traditional levels) and removal of mosses during haymaking is recommended. The study demonstrates that, for conservation purposes, it is not easy to replicate past conditions unless the details of traditional management practices are known and understood, and these are now passing from general knowledge.  相似文献   
323.
国外传统村落旅游研究及对我国的启示   总被引:3,自引:0,他引:3  
文献①分析发现,国外传统村落旅游存在多种驱动模式,研究的内容有传统村落旅游影响、传统村落社区与旅游、传统村落游客体验等,旅游研究的区域性很明显.基于国外传统村落旅游研究现状与国内传统村落旅游资源特点,认为国内传统村落旅游研究在如下方面有待深入:个案研究的拓展;旅游资源本体可持续性研究;旅游资源的再创造性;游客体验和游客感知;国内传统村落旅游现象的多学科研究.  相似文献   
324.
Approximately ten years have passed since Globally Important Agricultural Heritage Systems (GIAHS) was introduced to Japan in 2011, with 11 GIAHS sites designated so far. The Japan Nationally Important Agricultural Heritage Systems (J-NIAHS), which considers resilience, multi-stakeholder participation and sixth industrialization, was subsequently established in 2016, and has designated 15 J-NIAHS sites. GIAHS sites can be classified into three major types: Landscape, farming method, and genetic resource conservation types, and most Japanese GIAHS sites are of the landscape type. Since there is almost no national subsidy for GIAHS or J-NIAHS, designated sites are expected to secure funding for conservation from their own efforts. For this reason, a voluntary network of the Japanese GIAHS sites has been active in promoting cooperation on GIAHS conservation. The priorities of the Japanese GIAHS have focused on raising public awareness about GIAHS and J-NIAHS, improving livelihoods, as well as fostering the international exchange of experience and knowledge regarding Agricultural Heritage Systems, especially among Japan, China and Korea.  相似文献   
325.
当前国外政治地理学边境安全研究进展   总被引:2,自引:0,他引:2  
如何在边境地区最大限度地实现人流、物流和资金流等自由、快速的有效流动,从而促进国家经济快速发展的同时,防止国际犯罪集团、恐怖主义、非法移民、毒品和大量破坏性武器通过边境地区进入本国,以保证边境和国家的安全,已经成为各国对边境安全研究的核心。当前围绕这一主题国外政治地理学对边境安全的研究主要集中在:对边境安全研究的基本理论探讨、自由贸易与边境安全、恐怖主义与边境安全和先进技术应用与边境安全等4个方面。文章在梳理这4个专题已有研究的基础上,总结了今后边境安全需要进一步深入探讨的基本问题:1)边境安全的理论与实践之间的不一致性;2)高新技术在边境安全管理中的应用;3)边境安全管理中的双边合作;4)边境安全预警体系构建。最后,提出了国外边境安全研究对中国边境安全的一些启示。  相似文献   
326.
In order to investigate the relationship between the trace elements and the characteristics of the oysters, we analyzed the trace elements present in the germplasm of oysters from different producing areas in the Jiaozhou Bay. The element fingerprints were established to reflect the elemental characteristics of the oysters. Concentration patterns of the elements were deciphered by principle component analysis (PCA) and hierarchical cluster analysis (HCA). The six regions were discriminated with accuracy using HCA and PCA based on the concentration of 16 trace elements. The elements were viewed as characteristic elements of the oysters and the fingerprints of these elements could be used to distinguish the quality of the oysters.  相似文献   
327.
基于演化经济地理学视角,运用实地调研获得的第一手数据,构建由核心网络-支持网络-环境网络构成的创新网络结构模型,提出网络演化的分析框架,并对广州新塘牛仔服装制造产业集群创新网络演化过程、特征及动因进行实证研究。结果表明:1)新塘牛仔服装制造产业集群创新网络经历了萌芽(1980—1990年)、结网(1990—2000年)、成长(2000—2012年)和发展(2012—2018年)4个阶段。在萌芽期,企业间的生产和创新联系开始出现,集群创新网络初步建立;在结网期,大批量企业衍生加深了企业间的非正式联系,创新核心网络稳固发展;在成长期,政策及规划定位的调整重塑产业发展策略,创新联系增强,创新网络规模扩大;在发展期,政府与高校、研究机构和企业间的合作加强,龙头企业在牛仔服装生产上的技术创新能力得到提升,线上线下相结合的商业模式创新突显,创新网络规模稳定。2)不同子网络在推动整体网络演化过程中发挥不同作用。在萌芽期,创新环境子网络直接诱发创新网络的形成;在结网期,创新环境网络与创新核心网络共同推动创新网络的进一步发展;在成长期,创新支持网络是加速创新网络成长的主要因素。在发展期,创新环境网络再次成为创新网络演化中的关键。3)从演化动力上看,内生和外生动力共同推动集群创新网络的发展。集群外向型的经济特征使得初期网络由全球力量主导,在本地形成规模后向国内扩张。核心网络、支持网络、环境网络作为集群创新网络的重要组成部分,三者之间互为因果、互相作用,共同推进整体网络的演化。  相似文献   
328.
Abstract

The study area is located on the Harat plain, in the central region of Iran. Four local-soil filled, free-drainage lysimeters were installed in wheat and barley farms operating under traditional farm management practices. The volume, electrical conductivity (EC), nitrate and major ions of the applied irrigation water and irrigation return flow (IRF) were measured during the growing season. The total dissolved solids (TDS) of IRF increased three to five times compared to that of the applied water. This enhancement was the same as for the chloride ion ratio, indicating the major impact of evapotranspiration in IRF salinity enhancement. Geochemical modelling using PHREEQCI confirmed the significant role of evapotranspiration and the minor effects of processes such as calcite precipitation, gypsum dissolution, fertilizer nitrification and ion exchange on the values of the IRF TDS. Time variations of EC were functions of the type of flow (preferential or matrix), lithology and soil type. The controlling parameters of the nitrate time series were the frequent applications of N fertilizer and the nitrification process. The annual N loads (NO3-N) of IRF varied from 22 to 195 kg ha-1. These variations were due to the different N loads in the applied water, the amount of fertilizer, soil texture, N uptake and volume of IRF. The annual salt loads of IRF were mainly controlled by the volume of IRF.

Editor Z.W. Kundzewicz

Citation Jafari, H., Raeisi, E., Hoehn, E. and Zare, M., 2012. Hydrochemical characteristics of irrigation return flow in semi-arid regions of Iran. Hydrological Sciences Journal, 57 (1), 173–185.  相似文献   
329.
以产业转移和劳动力回流为主要特征的“双转移”是当前中国经济进入中速增长背景下一个新的发展趋势,是市场机制下产业和劳动力的理性选择。在此背景下,以河南周口市为案例地,通过实地调研和问卷访谈,分析了传统农区外出劳动力空间流向和回流意愿,重点对外出劳动力的回流动力、行为选择进行了调查分析,并从政府和制度层面提出回流地的规划响应。结果表明:①周口市外出劳动力回流意愿强烈,且有近期返乡的打算;②外出劳动力的回流动力呈现多元化,县城是除本村外回流劳动力居住和生活的重要空间选择;③就业机会、教育和医疗水平是外出劳动力回流最为关注的城镇吸引要素。最后,从地方政府和制度层面提出放权强县、促进“双转移”良性循环互动、公共服务设施均等化配置和推进土地户籍制度改革的规划响应措施。  相似文献   
330.
Abstract

In this paper, we describe and analyze the co-management institutional framework at 21 Brazilian Marine Extractive Reserves (MERs) and present the dramas of its implementation from the local manager’s perspective. We categorized the governance instruments of MERs into (i) instruments for land/sea tenure and beneficiaries’ recognition, (ii) territorial use planning, (iii) institutional arenas for discussion and deliberation, as well as (iv) public policies. Although the legal arrangements of these protected areas address fundamental dimensions of governance, we present the challenges of its implementation based on the voice of local managers. The managers are the bridge between the central government and communities, dealing with the implementation of the institutional framework in a reality of multi-level and multi-scale drama: from local to national dilemmas, from organizational to structural ones. We explore these dramas and highlight the institutional dilemmas based on the paradoxes between legalism and social emancipation.  相似文献   
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