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   28篇
  免费   0篇
  国内免费   1篇
测绘学   3篇
大气科学   1篇
地球物理   12篇
地质学   5篇
海洋学   6篇
天文学   1篇
自然地理   1篇
  2011年   1篇
  2010年   2篇
  2008年   1篇
  2007年   3篇
  2002年   1篇
  2000年   3篇
  1998年   1篇
  1997年   2篇
  1996年   2篇
  1995年   4篇
  1994年   1篇
  1993年   2篇
  1992年   2篇
  1991年   1篇
  1989年   2篇
  1980年   1篇
排序方式: 共有29条查询结果,搜索用时 46 毫秒
1.
2.
地球的脉动和现阶段的扩展   总被引:1,自引:0,他引:1  
脉动理论是本世纪初提出来的,最近该理论又得到了进一步的完善和发展,它可以更好地解释构造,岩浆,海平面变化,沉积作用之间的关系。地球的脉动以下列形式表现:火山作用强度,海进一步海退升,降旋回,挤压与扩展的交替、地磁场特征的变化等。  相似文献   
3.
计算机辅助资源信息系统(CARIS)是一个以矢量为基础的,商品化的地理信息系统(GIS),它在NewBrunswick大不测量工程系已扩充了栅格数据处理的功能。这种混合式的GIS具有完整的栅格影像/矢量图形显示,供两种数据类型的交互式操作,栅格影像的命令包括波段选择,像元素值和直方图的显示,反差增强,彩色空间变换,微分增量几何校正,屏幕上数字化和训练统计量的产生,对于计算上强度大的操作和大型栅格数  相似文献   
4.
本文使用下列关系式测定和估计和沿北太平洋地震区12个震源的强和大的浅层主震重现间隔:logT:=0.30Mmin+0.15Mp-0.27logM0+5.24 Mt=1.05Mmin-0.47Mp+0.60logmO-12.39其中Tt为事件间隔时间,按年数测量;Mmin为所考虑最小主震的面波震级;Mp为前一个主震的震级;Mf为后面跟着发生的主震震级;M0为每年每个震海的矩率。Tt对M  相似文献   
5.
6.
7.
Biodiesel, a mixture of fatty acid methyl esters (FAMEs) derived from animal fats or vegetable oils, is rapidly moving towards the mainstream as an alternative source of energy. However, the behavior of biodiesel, or blends of biodiesel with fossil diesel, in the marine environment have yet to be fully understood. Hence, we performed a series of initial laboratory experiments and simple calculations to evaluate the microbial and environmental fate of FAMEs. Aerobic seawater microcosms spiked with biodiesel or mixtures of biodiesel and fossil diesel revealed that the FAMEs were degraded at roughly the same rate as n-alkanes, and more rapidly than other hydrocarbon components. The residues extracted from these different microcosms became indistinguishable within weeks. Preliminary results from physical-chemical calculations suggest that FAMEs in biodiesel mixtures will not affect the evaporation rates of spilled petroleum hydrocarbons but may stabilize oil droplets in the water column and thereby facilitate transport.  相似文献   
8.
To understand the spatial variation in concentrations and compositions of organic micropollutants in marine plastic debris and their sources, we analyzed plastic fragments (∼10 mm) from the open ocean and from remote and urban beaches. Polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), dichloro-diphenyl-trichloroethane and its metabolites (DDTs), polybrominated diphenyl ethers (PBDEs), alkylphenols and bisphenol A were detected in the fragments at concentrations from 1 to 10,000 ng/g. Concentrations showed large piece-to-piece variability. Hydrophobic organic compounds such as PCBs and PAHs were sorbed from seawater to the plastic fragments. PCBs are most probably derived from legacy pollution. PAHs showed a petrogenic signature, suggesting the sorption of PAHs from oil slicks. Nonylphenol, bisphenol A, and PBDEs came mainly from additives and were detected at high concentrations in some fragments both from remote and urban beaches and the open ocean.  相似文献   
9.
The author provides an analysis of trends in population distribution for selected areas of the Soviet Union. Changes in the degree of population concentration in the Russian SFSR are examined within various economic regions and micro-regions, and factors contribution to population decline are discussed  相似文献   
10.
The abundance and higher taxonomic composition of epizooic metazoan meiobenthic communities associated with mussel and tubeworm aggregations of hydrocarbon seeps at Green Canyon, Atwater Valley, and Alaminos Canyon in depths between 1400 and 2800?m were studied and compared to the infaunal community of non-seep sediments nearby. Epizooic meiofaunal abundances of associated meiobenthos living in tubeworm bushes and mussel beds at seeps were extremely low (usually <100?ind. 10?cm(-2)), similar to epizooic meiofauna at deep-sea hydrothermal vents, and the communities were composed primarily of nematodes, copepods, ostracods, and halacarids. In contrast, epizooic meiobenthic abundance is lower than previous studies have reported for infauna from seep sediments. Interestingly, non-seep sediments contained higher abundances and higher taxonomic diversity than epizooic seep communities, although in situ primary production is restricted to seeps.  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