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   58篇
  免费   4篇
测绘学   7篇
大气科学   7篇
地球物理   12篇
地质学   17篇
海洋学   1篇
天文学   5篇
自然地理   13篇
  2019年   2篇
  2017年   2篇
  2016年   2篇
  2015年   2篇
  2013年   4篇
  2012年   1篇
  2011年   2篇
  2010年   2篇
  2009年   3篇
  2008年   1篇
  2007年   1篇
  2006年   1篇
  2005年   1篇
  2004年   1篇
  2003年   3篇
  2002年   1篇
  2001年   2篇
  2000年   2篇
  1998年   2篇
  1996年   1篇
  1994年   1篇
  1990年   1篇
  1989年   3篇
  1988年   2篇
  1981年   1篇
  1980年   1篇
  1979年   1篇
  1978年   4篇
  1976年   1篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1972年   2篇
  1971年   3篇
  1969年   1篇
  1968年   1篇
  1951年   1篇
排序方式: 共有62条查询结果,搜索用时 937 毫秒
11.
12.
Geographical indications, as a form of intellectual property, are becoming increasingly important in global trade. In South Africa's trade and cooperation agreement with the European Union, problems over the use of names such as 'port' and 'sherry' provided an important obstacle to the conclusion of the trade deal. This paper argues that the conflict over geographical indications in this trade agreement must be seen in the context of broader initiatives to establish a system of protecting this form of intellectual property through the World Trade Organisation.  相似文献   
13.
John P. Cole  P.M. Mather 《Geoforum》1979,10(3):235-241
The effects of wide availability of small, cheap, portable minicomputers on geography teaching and on the content of geography syllabuses in higher education are considered. Simulation, visual display, and computer aided instruction are identified as the features of minicomputers that are most likely to affect teaching methods, while the need to appreciate and to use computers will lead to a greater emphasis on training geography students in the skills required. Four simple examples of the use of the minicomputer in geography teaching are given, and the final section of the paper contains some recommendations for future developments.  相似文献   
14.
15.
We present the first application of a multi-stage impactor to study volcanic particle emissions to the troposphere from Masaya volcano, Nicaragua. Concentrations of soluble SO4 2–,Cl, F, NO3 , K+, Na+,NH4 +, Ca2+ and Mg2+ were determined in 11 size bins from 0.07 m to >25.5 m. The near-source size distributions showed major modes at 0.5m (SO4 2–, H+,NH4 +); 0.2 m and 5.0 m (Cl) and 2.0–5.0 m(F). K+ and Na+ mirrored the SO4 2– size-resolvedconcentrations closely, suggesting that these were transported primarily asK2SO4 and Na2SO4 in acidic solution, while Mg2+ andCa2+ presented modes in both <1 m and >1 m particles. Changes in relative humidity were studied by comparing daytime (transparent plume) and night-time (condensed plume) results. Enhanced particle growth rates were observed in the night-time plume as well as preferential scavenging of soluble gases, such as HCl, by condensed water. Neutralisation of the acidic aerosol by background ammonia was observed at the crater rim and to a greater extent approximately 15 km downwind of the active crater. We report measurements of re-suspended near-source volcanic dust, which may form a component of the plume downwind. Elevated levels ofSO4 2–, Cl, F,H+, Na+, K+ and Mg2+ were observed around the 10 m particle diameter in this dust. The volcanic SO4 2– flux leaving the craterwas 0.07 kg s–1.  相似文献   
16.
17.
18.
19.
20.
 Two karst areas within Permian and Triassic carbonate rocks of the Codru Moma Mountains in the northwestern part of Romania yield thermal waters. Major karst springs occur where groundwater flow is intercepted by hydraulic barriers, which also results in the movement of water from deeper levels. At Moneasa, thermal groundwater rises along faults and fractures associated with a thrust, and at Vascau Town, water rises along faults marginal to the Beius Basin. Geochemistry suggests that the thermal component of the Moneasa groundwaters is derived from dolomites and that at least a proportion of the Vascau thermal waters originates from deeply buried Permian sandstones. Received, August 1999 / Revised, March 2000 / Accepted, March 2000  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