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91.
本区6个砂金富集区与6个岩金集中区的空间分布完全相吻合;新构造运动频繁,地质环境动荡,金的次生富集作用效果较差;一部分砂金金粒与石英、蚀变岩石等脉石连生在一起;一部分砂金金粒的成色偏低;有的砂金矿体中部分砾石含金,有的高达3×10-6~10×10-6.据此认为研究区内砂金物质来源是以高含金地质体——岩金矿床(点)补给为主,低含金地质体补给为辅.碧口群、志留系、泥盆系作为矿源层,构造条件、岩浆活动均有利于本区岩金矿的形成,而且在矿源层的出露区已有近百处岩金矿床点分布.研究区化探异常、重砂异常30多处且分布较密集,异常峰值较高.研究认为本区确已具备形成更多更大的岩金矿床的地质条件,为此笔者提出勉县-平武找矿远景区. 相似文献
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93.
磁化率与粒度,矿物的关系及其古环境意义 总被引:80,自引:1,他引:80
根据实测数据,对磁化率与粒度、矿物之间的关系进行了探讨。结果表明,沉积物粒度与磁化率的关系,与物源及沉积动力密切相关。因此,在一定条件下,可利用两者关系来反映物源或沉积动力。碎屑沉积物的磁化率主要取决于磁铁矿的含量,并由此建立了磁化率(S,10^-7m^3kg^-1)与磁铁矿的百分含量(Pm)之间的回归方程S=49.18Pm+49.5。由于磁铁矿为重矿物,在沉积物中常常与钛铁矿、磷钇矿、独居石、锆 相似文献
94.
本文对砂金矿物的形态、表生显微结构及残留原生结构、化学成分及杂质元素、气液包体成分及爆裂温度进行了研究。认为该区的砂金以碎屑成因为主,化学成因仅占很次要的地位,砂金的原生来源为海西-燕山期的斑岩型和火山岩型金矿床。 相似文献
95.
96.
浅谈冲积型砂金矿床成矿模式——以陕西月河砂金矿床为例 总被引:2,自引:0,他引:2
本文通过对砂金矿床形成过程的分析认为:在地壳局部下沉过程中,砂金在水等强应力作用下,与砾石、砂一起进入沉积盆地,形成砂金的中间储存体;随着地壳的间歇性上升,在蛇曲河流的作用下由于砂金与砾石的运动规律相仿,故和砾面一起被保留在河流冲刷面上的河床滞留砾石沉积中。当地壳多次间歇性上升后,使砂金中间储存体中分散的砂金集中富集在河床滞留砾石层中,从而形成砂金矿床。 相似文献
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P.K. Dinesh Kumar R. Manimurali M.T. Babu K. Sudheesh P. Vethamony K.R. Naveen Kumar 《自然地理学》2014,35(5):411-428
An in-depth analysis has been made to simulate hydrodynamic scenarios for understanding the nearshore sediment transport controls of placer mineral depletion at Manavalakurichi, India. From the analyses of topographic configuration (extracted from Hydrographic Nautical Chart No. 2048 and data generated during year 2010), we inferred that the 5-m isobaths had broadened and exhibited shallowness. Distances between the coastline and the isobaths were found to have increased significantly over the past five decades. Along with this, the 10 and 20-m contours were found to have shifted about 35–100?m horizontally landward. These changes led to severe sediment deposition in these regions due to the changed wave energy levels and refraction patterns. Numerical simulations linking bathymetry, hydrodynamics, sediment load, and significant wave heights revealed that changes in bathymetry would amplify the wave heights and convergence of wave energy. Associated removal of sand from the high-energy zones will eventually lead to sediment starvation situations and depletion of placers in the adjacent beaches. As the observed trends of depletion generate great concern, detailed oceanographic investigations should be taken up immediately in the region. Fine-resolution hydrodynamic data-sets should prove useful for further evaluating the physical responses of the system to the altered geometry and for exploring remedial measures for restoring the heavy mineral content of the beach sand. 相似文献
99.
The practice has proved that it is an economic and effective method to investigate placer gold deposit by using multi-level information sources of remote sensing and multi-variate analysis methods, especially for the area with a sparse population and difficult condition like the Da Hinggan Mountains, China.The information sources used in our work includes Landsat TM, aerial infrared photography and their mosaic image maps and enlarged photos with different scales. According to statistic data, in the study area the gold-bearing rocks are mainly granite, alaskite, granodiorite and some old metamorphic rocks. On gold-bearing geological structures, the fault zones in the four directions (NE, NNE, NW and EW) are obvious, in which NNE and EW are the most key fault zones. On fluvial geomorphology the flow courses stored placer are in the tributaries of the 4th and 5th levels, especially in straight or slight curve reaches. On the basis of analysis the interpretative signs were set up, and the interpretative wo 相似文献
100.
Ballarat in western Victoria hosts substantial hard‐rock and palaeoplacer gold deposits. The most famous placers are the deep leads—channel deposits of a middle Cenozoic drainage system that were buried by voluminous basalt flows over the past few million years. The basalt has also shielded large areas of the highly prospective bedrock from exploration for more of the hard‐rock gold deposits. Although difficult to explore for, such deposits could express themselves as geochemical plumes in the major aquifer system hosted by the deep leads. Groundwater sampling may provide a vector to such deposits, but around Ballarat debate has long surrounded the distribution and flow directions of the deep leads, which are critical for this exploration methodology. The present landscape around Ballarat began to develop in the Early Cenozoic when a pre‐existing Mesozoic landscape was severely dissected during Australia‐Antarctica breakup. Several cycles of erosion left several generations of fluvial placer deposits scattered across the present landscape. New data from regional mapping, boreholes and compilation of historical records elucidates the positions and flow directions of the deep leads. The distribution and flow directions of the deep leads beneath the basalt are different to, and cannot be inferred from, the present drainage upon the basalt. The deep‐lead drainage divide runs beneath the city of Ballarat with divergence of up to 30 km between the deep lead and the present drainage divides. The divide was shifted northward to its present position by the process of drainage diversion because the basalt eruptions built new topography to greater heights than along the pre‐existing deep‐lead divide. 相似文献