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   3篇
  免费   0篇
地球物理   1篇
地质学   1篇
海洋学   1篇
  2013年   1篇
  2006年   1篇
  1979年   1篇
排序方式: 共有3条查询结果,搜索用时 0 毫秒
1
1.
2.
This study analyzes how overall changes in political and economic life during the last decade have affected the Estonian coastal fishery of the Baltic Sea. At the beginning of the nineties, the opportunity to export fish to the European market emerged. Opening of this new market resulted in rapidly increasing pressure on fish stocks. Some of the most important coastal fishery resources were over-fished because of high export market demand coupled with insufficient resource management and ineffective control and enforcement mechanisms. The costs associated with fishery have grown much more than the first-buyer prices. Additionally, dynamic development of the Estonian economy has resulted in substantial increases in earnings in other economic sectors and therefore the relative wealth of fishermen has steadily declined. This has resulted in increasing social problems. In conclusion, countries in transition may encounter serious difficulties in the fisheries sector, arising from privatization and economic reforms, which may affect the fisheries even years after the establishment of new ruling principles.  相似文献   
3.
Polished and thin section examinations of samples from Indiana Coal Bed V (Springfield) have shown three sulfides to be present; namely pyrite, marcasite and sphalerite. Pyrite and marcasite are dominant forms whereas sphalerite is very minor. These sulfides appear to have formed in four distinct stages as judged on the basis of mineralogy and mineral texture. Pyrite occurs as framboids throughout the coal seam, as fibrous crystals in two horizons of the coal and in massive form as cleat fillings and cell fillings in fusinite and semi-fusinite. Marcasite occurs in spherical polycrystalline and twinned grains, as polycrystalline overgrowths on framboids, as cementing material for clusters of framboids, as blocky polycrystalline grains and with pyrite as cell fillings in fusinite and semi-fusinite. Sphalerite occurs exclusively as cell fillings in semi-fusinite. The paragenetic sequence indicates fluctuations in the overall coal bed chemistry. Individual sections display evidence of chemical variation on the micro scale.  相似文献   
1
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