全文获取类型
收费全文 | 106篇 |
免费 | 16篇 |
国内免费 | 14篇 |
专业分类
大气科学 | 2篇 |
地球物理 | 18篇 |
地质学 | 83篇 |
海洋学 | 18篇 |
天文学 | 2篇 |
综合类 | 5篇 |
自然地理 | 8篇 |
出版年
2023年 | 1篇 |
2022年 | 6篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2014年 | 4篇 |
2013年 | 2篇 |
2012年 | 8篇 |
2011年 | 6篇 |
2010年 | 4篇 |
2009年 | 3篇 |
2008年 | 6篇 |
2007年 | 2篇 |
2006年 | 11篇 |
2005年 | 4篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2002年 | 5篇 |
2001年 | 6篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1985年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1977年 | 1篇 |
排序方式: 共有136条查询结果,搜索用时 15 毫秒
21.
中国大陆科学钻探主孔自然放射性测井及其解释 总被引:3,自引:0,他引:3
为了认识江苏东海超高压变质带上地壳岩石自然放射性的垂向分布特征, 榴辉岩退变质程度对放射性元素浓度的影响, 以及放射性产热率对地温梯度的影响, 利用中国大陆科学钻探(CCSD) 主孔100~5000m自然放射性测井(自然伽马和自然伽马能谱) 资料统计了CCSD主孔各类岩石的自然放射性强度和铀、钍、钾元素的浓度, 计算出产热率曲线.自然伽马, 铀、钍、钾浓度和产热率从蛇纹岩到榴辉岩、角闪岩、副片麻岩、正片麻岩依次增大.随着榴辉岩退变质程度的增强, 其铀、钍、钾元素的浓度值逐渐增大.CCSD主孔自然放射性的垂向分布特征主要受岩性控制, 自然放射性随深度增加有增强趋势.产热率与自然伽马测井值之间有很好的线性关系, 在高放射性岩层的上部, 地温梯度会出现较强扰动和低值异常. 相似文献
22.
Deriving hillslope sediment budgets in wildfire-affected forests using fallout radionuclide tracers 总被引:3,自引:1,他引:2
W.H. Blake P.J. Wallbrink S.N. Wilkinson G.S. Humphreys S.H. Doerr R.A. Shakesby K.M. Tomkins 《Geomorphology》2009,104(3-4):105-116
Information on post-fire sediment and nutrient redistribution is required to underpin post-fire catchment management decisions. Fallout radionuclide budgets (210Pbxs, 137Cs and 7Be) were derived to quantify soil redistribution and sediment yield in forested terrain following a moderately severe wildfire in a small (89 ha) water supply catchment in SE Australia. Application of these techniques in burnt terrain requires careful consideration of the partitioning of radionuclides between organic and mineral soil components. Beryllium-7 and 210Pbxs were shown to be closely associated with ash, litter and soil organic matter whereas 137Cs was more closely associated with subsurface coarse mineral soil. Comparison of the three tracer budgets indicated that the dominant sediment source areas were ridgetops and steep valley sideslopes, from which burnt surface material was conveyed to the stream network via pre-existing gullies. Erosion was predominantly driven by sheetwash, enhanced by soil water repellency, and modified by bioturbation which both supplies subsurface sediment and provides sinks for erosive overland flow. Footslope and riparian zones were not important sediment source areas. The estimated event-based (wildfire and subsequent rainfall) sediment yield is 58 ± 25 t km− 2, based on fallout 7Be measurements. The upper estimate of total particulate phosphorus yield (0.70 kg ha− 1) is more than 10 times that at equivalent unburnt sites. This illustrates that, soon after fire, burnt eucalypt forest can produce nutrient loads similar to those of agricultural catchments. The tracer budgets indicate that wildfire is an important control on sediment and phosphorus inputs to the stream network over the decadal timeframe and the pulsed nature of this release is an important concern for water quality management. 相似文献
23.
25.
26.
The occurrence of thermal/spa waters on Lesvos Island is related to the presence of a major faulting system. Thermal waters are the result of mixing of meteoric and infiltrating seawater at great depth, and their total salinity depends on the percentage of seawater in their composition. According to the diagrams of main elements, trace elements and environmental isotopes, most of the components that determine the chemical composition of thermal waters such as sodium, chloride and sulphates originate from seawaters. On the other hand, the concentration of calcium, magnesium, boron, lithium, etc., was affected by water–rock interaction under high temperature conditions. Moving towards the surface, thermal waters may become polluted by influx of recent seawater, allowing their chemical composition to become similar to that of seawater. The thermal waters of Lesvos Island present relatively high concentrations of ammonia and redox sensitive metals because they are hosted in a reducing environment. They also exhibit low nitrate concentrations due to their mixture with recent fresh water. Finally, they show increased radon concentrations, ranging from 20 to 60 kBq m?3 in the eastern and southern parts of the island, and about 230 kBq m?3 in the north, in the area of Eftalou–Argenos. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
27.
为探索和改进综合航空物探深部找矿模式,在南秦岭研究区最新航空数据基础上,结合岩性、构造及周边矿化点等特征,按一定条件优选出上高家庄磁、放综合异常进行重点研究。所选异常位于陕西省安康市石泉县北,经地面磁力、γ能谱、岩(矿)石物性等剖面测量及基础地质工作,知异常东北侧主要岩性为变质砂岩,西南侧多为云母石英片岩。铀元素放射性含量在两类岩性交界面的变质砂岩一侧最高,地表测得的最高含量超过70×10-6 eU。推测铀异常主要为变质砂岩造成,磁异常由一定埋深的区域变质片岩(原岩为火山岩)引起。以样品鉴定的矿化迹象为佐证,此处具有形成铁、铜、铀等矿产的前景。由空中数据优选异常,进而有效聚焦至地面重点区域,通过数据分析、实地测量、采样等验证手段,探究异常成因,是一种研究隐伏矿体,圈定找矿远景区的高效工作模式。 相似文献
28.
The Fukushima nuclear accident in 2011 released large amounts of radionuclides, including ~(137)Cs, into the Pacific Ocean. A quasi-global ocean radioactive transport model with horizontal grid spacing of 0.5°×0.5° and 21 vertical layers was thereafter established to study the long-term transport of the Fukushima-derived ~(137)Cs in the ocean.The simulation shows that the plume of ~(137)Cs would be rapidly transported eastward alongside the Kuroshio Current and its extensions. Contaminated waters with concentrations lower than 2 Bq/m3 would reach the west coast of North America 4 or 5 years after the accident. The ~(137)Cs tends to be carried, despite its very low concentration, into the Indian and South Pacific Oceans by 2016 via various branches of ocean currents.Meanwhile, the ~(137)Cs concentrations in the western part of the North Pacific Ocean decrease rapidly with time. Up to now the highly contaminated waters have remained in the upper 400 m, showing no evidence of significant penetration to deeper layers. 相似文献
29.
30.
Chandrayaan-1: Science goals 总被引:1,自引:0,他引:1
N. Bhandari 《Journal of Earth System Science》2005,114(6):701-709
The primary objectives of the Chandrayaan-1 mission are simultaneous chemical, mineralogical and topographic mapping of the
lunar surface at high spatial resolution. These data should enable us to understand compositional variation of major elements,
which in turn, should lead to a better understanding of the stratigraphic relationships between various litho units occurring
on the lunar surface. The major element distribution will be determined using an X-ray fluorescence spectrometer (LEX), sensitive
in the energy range of 1–10 keV where Mg, Al, Si, Ca and Fe give their Kα lines. A solar X-ray monitor (SXM) to measure the
energy spectrum of solar X-rays, which are responsible for the fluorescent X-rays, is included. Radioactive elements like
Th will be measured by its 238.6 keV line using a low energy gamma-ray spectrometer (HEX) operating in the 20–250 keV region.
The mineral composition will be determined by a hyper-spectral imaging spectrometer (HySI) sensitive in the 400–920 nm range.
The wavelength range is further extended to 2600 nm where some spectral features of the abundant lunar minerals and water
occur, by using a near-infrared spectrometer (SIR-2), similar to that used on the Smart-1 mission, in collaboration with ESA.
A terrain mapping camera (TMC) in the panchromatic band will provide a three-dimensional map of the lunar surface with a spatial
resolution of about 5 m. Aided by a laser altimeter (LLRI) to determine the altitude of the lunar craft, to correct for spatial
coverage by various instruments, TMC should enable us to prepare an elevation map with an accuracy of about 10 m.
Four additional instruments under international collaboration are being considered. These are: a Miniature Imaging Radar Instrument
(mini-SAR), Sub Atomic Reflecting Analyser (SARA), the Moon Mineral Mapper (M3) and a Radiation Monitor (RADOM). Apart from
these scientific payloads, certain technology experiments have been proposed, which may include an impactor which will be
released to land on the Moon during the mission.
Salient features of the mission are described here. The ensemble of instruments onboard Chandrayaan-1 should enable us to
accomplish the science goals defined for this mission. 相似文献