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排序方式: 共有713条查询结果,搜索用时 312 毫秒
291.
Ann M. Oberhauser 《The Professional geographer》1991,43(4):431-445
Since World War II, migrant labor has contributed significantly to Western Europe's economic growth. Initially, industries recruited and hired migrant workers to overcome labor shortages and downward demographic trends within the domestic work force. Since the recession of the mid-1970s, however, migrant labor has faced increasing job loss and restricted entry to many Western European countries. Throughout the postwar period, state immigration policy has supported industry, initially by assisting in the recruitment, and more recently, facilitating the repatriation of migrant workers. Economic and social disparities between developed core and underdeveloped peripheral countries are linked to international labor mobility. Certain sectors in the core benefit from the reserve labor force while emigration from peripheral countries partially contributes to these countries' economic problems. These issues are explored through a case study of the employment of North Africans in the French automobile industry. 相似文献
292.
293.
冻土工程国家重点实验室的回顾与展望 总被引:7,自引:2,他引:5
冻土工程国家重点实验室是我国唯一的一个以冻土工程为主要研究内容的综合性实验室,其建设和发展对促进我国冻土学的发展有非常重要的意义,在迎来兰州冰川冻土研究所建所40周年之际,冻土工程国家重点实验室也走过了近9年的历程,回顾昨天,展望未来,只有紧紧把握粘土学科前沿,创新超前,解决国家在寒区经济和社会发展中提出的基础性,关键性和综合性的工程和资源环境问题,才能创建一流的国家重点实验室,使我国冻土工程研究 相似文献
294.
Abstract. The polychaetc fauna was studied in 18 soft-bottom stations in Amvrakikos Bay of the Ionian Sea. Of the 146 species found many had single occurrences, which caused low similarity between stations. Mixing and renewal of water influenced the distribution of species and feeding types of polychaetes, while their diversity correlated with sedimentary structure. Water depth was the factor which accounted for the greatest variability in the data, whereas salinity had no discernible effect on the polychaetc fauna. 相似文献
295.
Abstract. The population ecology and dynamics of Cuprella equilibra were studied in a lagoon estuary of the Northern Adriatic Sea during 1985 to 1986. The breeding activity showed peaks in April and September and a decrease in summer due both to high temperatures and a dystrophic crisis; breeding stops in winter. Females produced more than one brood per year. 相似文献
296.
Renewable energy from the ocean 总被引:3,自引:0,他引:3
Growing concern over the threat of global climate change has led to an increased interest in research and development of renewable energy technologies. The ocean provides a vast source of potential energy resources, and as renewable energy technology develops, investment in ocean energy is likely to grow. Research in ocean thermal energy conversion, wave energy, tidal energy, and offshore wind energy has led to promising technologies and in some cases, commercial deployment. These sources have the potential to help alleviate the global climate change threat, but the ocean environment should be protected while these technologies are developed. Renewable energy sources from the ocean may be exploited without harming the marine environment if projects are sited and scaled appropriately and environmental guidelines are followed. 相似文献
297.
毛学荣 《南京气象学院学报》2017,9(3):246-261
本文对混杂随机时滞微分方程的当前发展及最新的研究成果进行了概述.主要回顾了混杂随机微分方程解的存在唯一性定理、稳定性、鲁棒有界性以及离散时间反馈镇定性等部分对混杂随机微分方程的研究起到关键推动作用的成果. 相似文献
298.
Wendy Harte 《The Journal of geography》2017,116(5):226-236
This study evaluated the efficacy of geospatial technology (GT) learning experiences in two geography curriculum courses to determine their effectiveness for developing preservice teacher confidence and preparing preservice teachers to incorporate GT in their teaching practices. Surveys were used to collect data from preservice teachers at three intervals over one semester. Results indicate preservice teachers' confidence and competencies to successfully integrate GT in their teaching increased over the duration of the study. The findings highlight the value of providing GT learning experiences in geography curriculum courses and contribute to the literature on preparing preservice teachers to incorporate GT in teaching geography. 相似文献
299.
大气边界层物理学的研究进展和面临的科学问题 总被引:26,自引:3,他引:26
回顾了大气边界层物理学的发展历史,总结了该领域国际上目前所取得的主要研究进展,提出国内外在未来大气边界层物理学研究方面可能面临的一些主要科学问题,还对未来大气边界层物理学的发展方向提出若干建议,同时也指出了大气边界层物理学研究在思想和方法上应该注意的一些相关问题。 相似文献
300.
Michal Klobučník Vladimír Bačík 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2016,116(2):159-175
The aim of the submitted study was to illustrate the development of the number of local authorities in all current EU states in the long period between 1950 and 2011 comprehensively, and also by particular decades, thus demonstrating the originality and uniqueness of the topic analysed in this context. Thus, we obtain a more detailed picture of the development of the number of local authorities in EU countries, and we can monitor how local authorities within a specific country gradually developed. (The stabilisation of the number of local units and an increase or gradual or sudden drop in local units are shown, for example). A sudden drop in local units can be associated with significant administrative reforms and with the development of large units of the so-called municipalities. When it becomes necessary to merge local authorities, many countries look to other countries where extensive reforms took place in the past for inspiration. However, it must be borne in mind that in a general European context, we cannot apply a universal system of public administration reforms, and solutions in the form of these reforms inspired by other countries may not always be appropriate. 相似文献