全文获取类型
收费全文 | 3198篇 |
免费 | 484篇 |
国内免费 | 711篇 |
专业分类
测绘学 | 501篇 |
大气科学 | 105篇 |
地球物理 | 433篇 |
地质学 | 2341篇 |
海洋学 | 225篇 |
天文学 | 11篇 |
综合类 | 377篇 |
自然地理 | 400篇 |
出版年
2024年 | 16篇 |
2023年 | 43篇 |
2022年 | 125篇 |
2021年 | 141篇 |
2020年 | 133篇 |
2019年 | 141篇 |
2018年 | 121篇 |
2017年 | 133篇 |
2016年 | 169篇 |
2015年 | 163篇 |
2014年 | 222篇 |
2013年 | 232篇 |
2012年 | 202篇 |
2011年 | 199篇 |
2010年 | 194篇 |
2009年 | 214篇 |
2008年 | 209篇 |
2007年 | 202篇 |
2006年 | 209篇 |
2005年 | 135篇 |
2004年 | 188篇 |
2003年 | 108篇 |
2002年 | 125篇 |
2001年 | 141篇 |
2000年 | 93篇 |
1999年 | 106篇 |
1998年 | 66篇 |
1997年 | 54篇 |
1996年 | 40篇 |
1995年 | 39篇 |
1994年 | 33篇 |
1993年 | 21篇 |
1992年 | 25篇 |
1991年 | 12篇 |
1990年 | 16篇 |
1989年 | 21篇 |
1988年 | 13篇 |
1987年 | 15篇 |
1986年 | 16篇 |
1985年 | 18篇 |
1984年 | 21篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1978年 | 1篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1973年 | 2篇 |
1972年 | 2篇 |
排序方式: 共有4393条查询结果,搜索用时 15 毫秒
11.
1 .IntroductionThe lifting systemis composed of pipes andtheir connectors .It is not onlythe lifting channel formanganese nodule betweenthe miningship andintermediate bin,but alsothe supporting massfor deepsea miningequipment and cables .Sothe reliability… 相似文献
12.
13.
14.
本文分析了厦门海沧海岸地区花岗岩资源开发利用现状和存在的问题,运用生态恢复理论讨论了矿山采石高难度地生态恢复技术途径和模式。 相似文献
15.
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
16.
17.
自行式海底作业车的研究 总被引:4,自引:0,他引:4
理论分析和试验研究是本文写作基础,它详细地总结了大洋多金属结核资源开发而研究自行式海底作业车取得中期成果,它对我国大洋采矿和其它海底工程车辆的发展有着重要的文献价值和指导意义。 相似文献
18.
19.
Hyung-suk HAN 《中国海洋工程》2003,17(3)
1 .IntroductionOnthedeepseabed ,30 0 0~ 50 0 0mbelowthePacificOcean ,manganesenodulesaresolidifiedandspread ,andmanycountriesintheworldarestudyinghowtominethem .AccordingtoYamazakietal.( 1 998)andAmannetal.( 1 991 ) ,theenvironmentofthedeepseabedisdifferentfromthedrylandinmanyways .Inparticular,thesurfaceoftheseabedisverysoft.Inordertoensuretheperformanceofrunningofamanganesenodulemineronsuchasoftsurface ,thetrackedvehiclemaybeapplied .Ac cordingtoHongandChoi ( 2 0 0 1 ) ,astudyisbeingdone… 相似文献
20.
李柱臣 《中国地理科学(英文版)》1992,2(1):56-63
The Loess Plateau is one of China s developing areas where socio-econ-omy is backward, ecological environment deteriorated and people's life difficult.The purpose of carrying out comprehensive development of the area's agriculture is, in essence, to open up new fields of agro-production, to intensify the utilization of related resources, to raise productivity and to win bigger output. The decision is important, as by so doing, the physical landscape could be tranformed, the local economy could be flourished, and the people's standard of living could be improved, and moreover the national development strategy of "depending on the East and shifting to the West" and building Shanxi Province into an energy and chemical industrial base could be realized.Based on field investigations in recent years, the auther proposed the purpose, target, principles, steps, tactics and strategies for the comprehensive development of the are's agriculture. 相似文献