全文获取类型
收费全文 | 1178篇 |
免费 | 356篇 |
国内免费 | 170篇 |
专业分类
测绘学 | 38篇 |
大气科学 | 46篇 |
地球物理 | 664篇 |
地质学 | 674篇 |
海洋学 | 45篇 |
天文学 | 14篇 |
综合类 | 69篇 |
自然地理 | 154篇 |
出版年
2024年 | 3篇 |
2023年 | 9篇 |
2022年 | 29篇 |
2021年 | 34篇 |
2020年 | 40篇 |
2019年 | 65篇 |
2018年 | 40篇 |
2017年 | 46篇 |
2016年 | 52篇 |
2015年 | 52篇 |
2014年 | 86篇 |
2013年 | 60篇 |
2012年 | 83篇 |
2011年 | 78篇 |
2010年 | 59篇 |
2009年 | 89篇 |
2008年 | 69篇 |
2007年 | 95篇 |
2006年 | 97篇 |
2005年 | 87篇 |
2004年 | 54篇 |
2003年 | 56篇 |
2002年 | 51篇 |
2001年 | 36篇 |
2000年 | 43篇 |
1999年 | 37篇 |
1998年 | 44篇 |
1997年 | 39篇 |
1996年 | 43篇 |
1995年 | 26篇 |
1994年 | 22篇 |
1993年 | 23篇 |
1992年 | 8篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 4篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1954年 | 2篇 |
排序方式: 共有1704条查询结果,搜索用时 15 毫秒
31.
运用烃类勘察地球化学方法,对鄂尔多斯盆地南部彬县大佛寺井田钻遇中休罗统煤层的耽钻孔,进行了垂向剖面多指标的综合地球化学研究。结果表明:剖面中所有岩样中的烃类物质均为热解烃生成初期演化阶段的煤成烃产物,具明显的同一性;由煤层至地表黄土,所有岩样中的烃类呈明显的、规律性垂直向上运移。这证实地下煤层烃类在近地表具有很好的地球化学信息显示,利用勘察地球化学方法找煤/煤层气是可行的。 相似文献
32.
青海平安电磁辐射在中强震前短期前兆异常特征及预报效能研究 总被引:2,自引:0,他引:2
分析和整理了青海平安电磁辐射台自1993年7月以来的资料,发现震前平安单台电磁辐射在中强地震临震前有最大脉冲信号,并通过对无震异常,地震异常的分析判断,对其预报效能进行了R值评价。 相似文献
33.
2001年10月底广州东山湖水面出现宏观异常现象,市民怀疑为地震前兆异常。经过对异常的调查落实,结合广东省地震形势及前兆资料的分析研究,准确判断东山湖的异常现象并非地震宏观异常现象,消除了市民的不安与恐慌。 相似文献
34.
George F. Risk T. Grant Caldwell Hugh M. Bibby 《Journal of Volcanology and Geothermal Research》2003,127(1-2):33-54
Experimental measurements in the Ngatamariki geothermal field, North Island, New Zealand were made to test the applicability of the time domain electromagnetic method for detailed investigation of the resistivity structure within a geothermal field. Low-frequency square wave signals were transmitted through three grounded bipole current sources sited about 8 km from the measurement lines. Despite high levels of electrical noise, transient electric field vectors could be determined reliably for times between 0.02 and 3.3 s after each step in the source current. Instantaneous apparent resistivity tensors were then calculated. Apparent resistivity pseudosections along the two measurement lines show smooth variations of resistivity from site to site. Over most of the field the images consistently show a three-layer resistivity structure with a conductive middle layer (3–10 Ωm) representing the conductive upper part of the thermal reservoir. A deep-seated region of low resistivity in the northwest of the field may indicate a conductive structure at about 1 km associated with a deeper diorite intrusion. Measurements sited closer than about 100 m to drillholes appear to have been disturbed by metallic casing in the holes. A change in resistivity structure in the east of the field may indicate a major geological or hydrothermal boundary. 相似文献
35.
Buried Quaternary valleys in Denmark are complex structures filled with various deposits consisting primarily of glacio-lacustrine clay, till and meltwater sand, and gravel. The valleys are important geophysical targets, because they often contain significant volumes of groundwater used for public water supply. About 700 km of buried valley structures have been imaged in the western part of Denmark by the transient electromagnetic (TEM) method. The ability to map the valleys depends primarily on valley geometry, infill architecture and the resistivity of the fill sediments as well as the substratum. One-dimensional (1-D) inversion models of the TEM soundings have been used to construct contour maps of 20 m average resistivities and depth to a good conductor, which provide images for geological interpretation. Images of buried valley morphology, fill properties, infill architecture, such as cut-and-fill structures, valley distribution and valley generations, are characterized for case studies from Hornsyld, Holstebro and the Vonsild/Agtrup areas of Denmark. 相似文献
36.
时间谱电阻率法中的剩余电磁效应研究 总被引:2,自引:0,他引:2
根据频谱激电(SIP)法或复电阻率(CR)法中研究剩余电磁(REM)效应的思想,通过分析时间谱电阻率(TSR)法中场的基本特征,在TSR法中建立了与SIP(或CR)法中参数Φmax/Φ0max相类似的参数-Emax/E0,用来描述了TSR法中的REM效应。通过对一维可极化大地模型的REM效应的理论计算,验证了用Emax/E0表示的REM异常可用来形象地反映地电断面电阻率的高低。 相似文献
37.
In Italy, the horizontal stress directions are well constrained in many regions, but the tectonic regime is not well known because the stress magnitudes are unknown. Our intention is to improve the knowledge of crustal stress in Italy, both at shallow depth and in low seismicity areas. Therefore, we inferred the tectonic regime from the comparison between the depth of breakout occurrence and the physical properties of the rocks in 20 boreholes. The critical value of the maximum horizontal stress, for which the effective tangential stress at the borehole wall overcomes the rock strength to form breakouts, could be computed from rock strength and density. Comparing the theoretical stress distributions for different tectonic regimes with the depth distribution of breakout occurrence, it is possible to infer the tectonic regime that fits best to the breakout depth distribution. We investigated boreholes up to 6 km deep located in different tectonic environments over the Italian peninsula: the Po Plain, the Apenninic chain, the Adriatic foredeep and the Tyrrhenian Quaternary volcanic region. These wells are characterised by breakout data of good quality (A, B and C, according to World Stress Map quality ranking system). The results are in general agreement with the style of faulting derived from earthquake focal mechanisms and other stress indicators. Our results show a predominance of a normal faulting (NF) regime in the inner Apennines and both normal faulting and strike–slip faulting (SS) style in the surrounding regions, possibly also associated with changes in the tectonic regime with depth. 相似文献
38.
39.
40.
瞬变电磁法的野外资料解释基本上停留在一维水平,本文从生产实践中常用的中心回线法入手,基于电磁场本身的叠加原理,从麦克斯韦方程组出发,导出了中心回线瞬变电磁2.5维二次场(纯异常)的有限单元计算公式. 该算法采用三角形有限元网格,在尽可能拟合地下电性断面的情况下减少有限元网格的节点数和单元数;用选主元的LU分解法求解线性方程组,做到了在移动场源时只需改变右端项;在反傅氏变换中,使用新的波数选取方案,让波数m随时间t滑动. 最后给出的算例表明,该算法直接计算异常场,计算速度快、精度高. 相似文献