全文获取类型
收费全文 | 952篇 |
免费 | 119篇 |
国内免费 | 144篇 |
专业分类
测绘学 | 30篇 |
大气科学 | 1篇 |
地球物理 | 105篇 |
地质学 | 978篇 |
海洋学 | 39篇 |
天文学 | 2篇 |
综合类 | 31篇 |
自然地理 | 29篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 9篇 |
2021年 | 14篇 |
2020年 | 29篇 |
2019年 | 30篇 |
2018年 | 21篇 |
2017年 | 30篇 |
2016年 | 51篇 |
2015年 | 22篇 |
2014年 | 60篇 |
2013年 | 43篇 |
2012年 | 38篇 |
2011年 | 46篇 |
2010年 | 46篇 |
2009年 | 55篇 |
2008年 | 42篇 |
2007年 | 45篇 |
2006年 | 56篇 |
2005年 | 50篇 |
2004年 | 43篇 |
2003年 | 30篇 |
2002年 | 32篇 |
2001年 | 25篇 |
2000年 | 37篇 |
1999年 | 30篇 |
1998年 | 33篇 |
1997年 | 36篇 |
1996年 | 41篇 |
1995年 | 27篇 |
1994年 | 17篇 |
1993年 | 23篇 |
1992年 | 20篇 |
1991年 | 15篇 |
1990年 | 18篇 |
1989年 | 19篇 |
1988年 | 22篇 |
1987年 | 16篇 |
1986年 | 17篇 |
1985年 | 13篇 |
1984年 | 5篇 |
1981年 | 2篇 |
1979年 | 2篇 |
排序方式: 共有1215条查询结果,搜索用时 15 毫秒
101.
本文论述用地面伽玛能谱资料估计地层(体)含铀性和资源量方法,并提出富铀富集体、铀源富集体、尤其富铀源富集体是最有利于成矿的结论。 相似文献
102.
对砚石台地区地层构造及滑覆构造组成要素、特征、形成机制进行了系统分析,论述了滑覆构造对煤层的影响,预测了-500m标高以下构造形态,提出-500m标高以下无须工作的建议。 相似文献
103.
根据30多年矿井生产实测资料,对中梁山煤矿地质构造进行了分析研究,认为该矿地质构造虽然复杂,但也具有一定的规律,可分为简单、中等、复杂等不同构造区,大断层虽较多但对矿井开采影响不大,只是小型压扭性断层对采矿造成一定困难,故提出开采时应对症下药及保护资源的建议。 相似文献
104.
Summary The Delivery Tunnel South forms part of a system of tunnels for conveying water from Lesotho to South Africa. The tunnel was excavated primarily by tunnel boring machine in the sandstones of the Clarens Formation. These sandstones are uniformly graded and fine grained with quartz being the most abundant mineral. They are mostly of aeolian origin. Their unconfined compressive strength varies appreciably, from moderately strong to extremely strong. The boreability of the sandstones was investigated by the Norwegian Institute of Technology tests and the total hardness. These tests showed that these sandstones would be relatively easy to bore, although moderately abrasive. The prediction proved correct. In fact, excavation of the tunnel was completed 20 months ahead of schedule, the rock conditions being better than expected. The long-term durability of these sandstones was investigated to establish criteria for concrete lining of the tunnel. A series of tests were undertaken to evaluate the durability. These included a number of soaking tests using different fluid media, wet and dry testing, erosion tests and brushing tests. This testing programme suggested that concrete lining of the intact sandstone was probably only required where the strength of the sandstone was less than 20 MPa and that therefore only a small percentage of the tunnel need be lined. 相似文献
105.
Mineral extraction and processing, especially metal mining, produces crushed and milled waste; such material, exposed to weathering, poses the potential threat of environmental contamination. In this study, mill tailings from inactive Pb-Zn mines in New Mexico, southwest USA, have been examined for their potential environmental impacts by means of detailed mineralogical and geochemical characterization. The principal ore minerals remaining in the tailings material are sphalerite, chalcopyrite, and very minor galena, smithsonite, and cerrusite, accompanied by the gangue minerals pyrite, pyrrhotite, magnetite, hematite, garnet, pyroxene, quartz, and calcite. White precipitate occurring on tailings surfaces is composed of gypsum and hydrated magnesium sulfates. Pyrite is mostly unaltered or shows only micron-scale rims of oxidation (goethite/hematite) in some surface samples. This iron oxide rim on pyrite is the only indication of weathering-derived minerals found by microscopy. There are variations in element concentrations with depth that reflect primary variations through time as the tailings ponds were filled. Cadmium and Zn concentrations increase with depth and Ag and Pb are low for the uppermost core samples, while Cu, Ni, and Co concentrations are generally high for the uppermost core samples. These elemental distributions indicate that little or no leaching has taken place since emplacement of the tailings because no accumulation or enrichment of these metals is observed in Hanover tailings, even in reducing portions of tailings piles. Element concentrations of surface samples surrounding the tailings reflect underlying mineralized zones rather than tailings-derived soil contamination. We observed no successive decreasing metal concentrations in prevalent wind directions away from the tailings. Stream sediment samples from Hanover Creek have somewhat elevated Zn, Cd, and Pb concentrations in areas that receive sediments from erosion of the tailings. However, input from tributaries downstream of the ponds appears to be principal source of heavy metals in Hanover Creek. The results of this study indicate that there is low risk for groundwater heavy-metal contamination from Hanover tailings. Tailings material do not show significant geochemical oxidation/alteration or metal leaching with depth. Our studies indicate that neutralizing minerals present in the tailings are sufficient to keep the tailings material chemically stable. Geochemically, however, tailings materials are being eroded and may pose a threat to Hanover Creek via siltation. 相似文献
106.
论当前我国北西部铀矿勘查关键技术 总被引:1,自引:1,他引:1
本文提出当前我国北西部铀矿勘查两项关键技术──中国北西部寻找大型超大型可地浸砂岩铀矿勘查技术和找矿勘探过程中地浸可行性评价技术,并论述了技术内容和技术开发目标。两项关键技术的开发研究和落实对扩大我国铀矿资源有现实意义。 相似文献
107.
108.
109.
煤矿矿图的GIS管理、更新与共享 总被引:5,自引:0,他引:5
矿山地学信息时刻处于时空动态变化中,矿图的及时维护与更新十分重要。该文针对矿山需求,基于矿山GIS(MGIS)、Web-GIS和办公自动化(OA)技术,结合矿山GIS基础平台TT-MGIS^2002,介绍了矿图管理、绘制、更新及网络共享问题。 相似文献
110.
云南铜矿是历史上开发最早的地区之一,至今已知的大-中型矿区(除边远的羊拉、托顶之外),历史上几乎都不同程度地被开采过。也有历史上曾采冶辉煌,但至今却没有铜矿产出,找铜工作者也不知道的“古老铜矿”,俞元(澄江)铜矿即是一例。研究、考证采铜史料,认为澄江铜矿、东川茂麓厂、寻甸铜矿、永平宁台厂等,应列为新世纪重新评价的找铜目标。 相似文献