全文获取类型
| 收费全文 | 6812篇 |
| 免费 | 696篇 |
| 国内免费 | 566篇 |
专业分类
| 测绘学 | 191篇 |
| 大气科学 | 234篇 |
| 地球物理 | 2656篇 |
| 地质学 | 1615篇 |
| 海洋学 | 851篇 |
| 天文学 | 31篇 |
| 综合类 | 289篇 |
| 自然地理 | 2207篇 |
出版年
| 2024年 | 41篇 |
| 2023年 | 130篇 |
| 2022年 | 294篇 |
| 2021年 | 349篇 |
| 2020年 | 298篇 |
| 2019年 | 270篇 |
| 2018年 | 259篇 |
| 2017年 | 265篇 |
| 2016年 | 292篇 |
| 2015年 | 281篇 |
| 2014年 | 375篇 |
| 2013年 | 381篇 |
| 2012年 | 339篇 |
| 2011年 | 354篇 |
| 2010年 | 296篇 |
| 2009年 | 380篇 |
| 2008年 | 345篇 |
| 2007年 | 393篇 |
| 2006年 | 391篇 |
| 2005年 | 333篇 |
| 2004年 | 268篇 |
| 2003年 | 253篇 |
| 2002年 | 190篇 |
| 2001年 | 158篇 |
| 2000年 | 172篇 |
| 1999年 | 148篇 |
| 1998年 | 172篇 |
| 1997年 | 131篇 |
| 1996年 | 105篇 |
| 1995年 | 87篇 |
| 1994年 | 87篇 |
| 1993年 | 77篇 |
| 1992年 | 67篇 |
| 1991年 | 26篇 |
| 1990年 | 29篇 |
| 1989年 | 11篇 |
| 1988年 | 10篇 |
| 1987年 | 3篇 |
| 1986年 | 6篇 |
| 1985年 | 3篇 |
| 1984年 | 5篇 |
排序方式： 共有8074条查询结果，搜索用时 46 毫秒
61.
Fisheries in boreal ecosystems 总被引：2，自引：1，他引：2
62.
This study takes cognizance of the fact that the TIOMIN (TIOMIN Resources Inc. of Canada) project has resulted in controversy over its handling of environmental issues and especially the Environmental Impact Assessment (EIA). The authors address many of the protracted issues that have slowed the development of the mining project in Kwale. The main emphasis is on the impacts of the mining and mineral separation processes on the environment, including the governing legislation, the role of consultation and public participation, and socioeconomic issues. In their public documents TIOMIN has specified neither the type of minerals it wants to extract from the area nor their chemical composition. It is well known, however that the titanium minerals and zircon targeted have impurities of iron, thorium and uranium. In the absence of an Environmental Management Plan, the effects of stockpiling radioactive wastes and other impurities that could possibly lead to environmental degradation in both the terrestrial and marine environments have not been publically addressed. The measures proposed to mitigate ecological damage as a result of the establishment of a minerals processing plant in the area seem inadequate. Pollution resulting from accidental spillage or breakage could have significant impact on marine life and residents living near the mining site. Other issues that have not been addressed satisfactorily pertain to the use of surface and underground water. The area already faces a huge water deficit and the calculations presented on aquifer recharge and stream flow rates do not indicate the large quantities of water that would be required in the mineral processing plant. The project, if approved in its present state, risks violation of international conventions. Furthermore, it could cause a conflict between Kenya and Tanzania in the event of an oil spill at the proposed ship loading facility at Shimoni. The proposed mining area includes the district's most fertile land, is home to many fisherfolk and is a major tourist destination. An analysis of the effects of this project on other available opportunities must be thoroughly understood to ascertain the economic and environmental benefits and costs of the mining venture. The proposed compensation rate of $1,000 per acre, for resettlement for example, appears to be grossly inadequate. Compensation should take into account family size and structure family assets and the cost of relocation. 相似文献
63.
64.
65.
66.
67.
Combining indicator trends to assess ongoing changes in exploited fish communities: diagnostic of communities off the coasts of France 总被引：1，自引：1，他引：1
68.
69.
70.