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通过对陆羽逆断层系上1896年同震地表破裂特征、长期活动习性和断错地貌等的研究,给出了可识别的逆断层型段落边界的标志,它们是断层崖形态持久性变化的过渡地段、断层抬升盘山地分水岭高程明显变化的转折部位、剖面几何结构转换区和断层下降盘盆地内的隐伏横向基岩脊等;指出逆断层上公里量级的空缺和阶区不能有效地终止或延缓逆断层型同震地表破裂的横向扩展,因此,不能作为逆断层型段落的边界,最后对陆羽逆断层系的千屋段和横手段的地震危险性进行了简要评估 相似文献
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1626年灵丘地震烈度分布特征与阻震构造初步讨论 总被引:1,自引:0,他引:1
对1626年灵丘地震的破坏情况进行了重新考证,着重指出了灵丘地震烈度沿唐河大断裂的高值异常和向西的快速衰减特征。在此基础上,提出了阻震构造的概念并进行了相应的理论分析。文章最后指出:唐河大断裂是1626年灵丘地震的阻震构造。 相似文献
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太白维山山前断裂活动特征的初步研究 总被引:1,自引:0,他引:1
本文立足于大量的野外第一手资料,综合解剖了太白维山山前断裂的几何结构,并就其运动学特征进行了初步探讨。认为:太白维山山前断裂第四纪以来的活动表现为正断型,其几何结构和运动特征都有着相同的分段性。我们将其划分为三段,西段结构简单,晚更新世以来无明显活动;中段结构复杂,一直强烈活动;东段活动强度较低。晚更新世晚期以来断裂(中段)的平均滑动速率0.4mm/a,全新世以来达到0.67mm/a,而且这种速率 相似文献
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景益鹏 《中国天文和天体物理学报》1989,(1)
本文对D≤4,R≥0的Abell团样品和整个R≥3的Abell团样品的空间两点相关函数做了统计分析,结果表明R≥0,R=0和R≥3的Abell团的相关函数分别为175r~(-1.8),150r~(-1.8)和1900r~(-1.8)利用已有的R≥1和R≥2团的相关函数的统计结果,我们得到了Abell团的相关性幅度α与富度N之间的关系:α∝N~(1.6)。在相关性幅度的统计误差所允许的范围内,α与N之间的关系可以在宇宙弦理论中得到解释。 相似文献
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洋内岛弧及微陆块的俯冲增生是形成增生杂岩的重要机制。本文通过对南羌塘地区日湾茶卡组进行野外实测地质剖面,开展沉积特征、古生物化石、碎屑组分模式、碎屑锆石测年等研究,发现:(1)日湾茶卡为近源沉积,最年轻碎屑锆石年龄峰值为325~375 Ma,但在龙木错-双湖古特提斯大洋周边陆块均未发现源区,其真正物源应为其下伏的望果山组火山岩;(2)日湾茶卡组内珊瑚化石丰度虽然高,但分异度非常低,其沉积位置应是一个相对突出的孤立位置。根据日湾茶卡组下伏望果山组火山岩所具有的洋内岛弧地球化学特征,并与同期SSZ型蛇绿岩组成的类似洋内俯冲的大地构造体系对比,本文认为日湾茶卡组与其下伏的望果山组火山岩共同组成了泥盆纪—石炭纪由洋内俯冲形成的古岛弧地体。根据碎屑锆石分布型式的相似性,本文进一步认为猫儿山地区部分南羌塘增生杂岩的源岩为日湾茶卡组。因此,日湾茶卡洋岛应曾经历过俯冲增生作用:浅部发生前端"刮削作用"形成冈玛错地区有变形但无变质的日湾茶卡组及望果山组,俯冲到深部的日湾茶卡组则发生高压变质作用并在后期折返至增生杂岩的浅部层次。因此,本文认为在南羌塘增生杂岩的形成过程中,日湾茶卡古岛弧地体的俯冲与增生也起到了重要的作用。 相似文献
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Migration of strong earthquakes (M≥ 7.0) along the North-South Seismic Belt of China since 1500 AD shows three patterns: Approximately equal time and distance interval migration from N to S, varied patterns of migration from S to N and grouped strong earthquake activity in a certain period over the entire seismic belt. Analysis of strong earthquakes in the past hundred years shows that the seismicity on the North-South Seismic Belt is also associated with strong earthquake activities on the South Asia Seismic Belt which extends from Myanmar to Sumatra, Indonesia. Strong earthquakes on the former belt often lag several months or years behind the quakes occurring on the later belt. So, after the occurrence of the December 26, 2004 Ms8.7 great earthquake off the western coast of Sumatra, Indonesia, the possibility of occurrence of strong earthquakes on the North-South Seismic Belt of China cannot be ignored. The abovementioned migration characteristics of strong earthquakes are related to the northeastward collision and subduction of the India Plate as well as the interaction between the Qinghai-Xizang (Tibet) Plateau and the stable and hard Ordos and Alashan Massifs at its northeastern margin. 相似文献
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Understanding land use and cover change impacts on run‐off and sediment load at flood events on the Loess Plateau,China 下载免费PDF全文
Xiaoping Zhang Pengfei Lin Hao Chen Rui Yan Jianjun Zhang Yipeng Yu Erjia Liu Yahui Yang Wenhui Zhao Du Lv Siyue Lei Baoyuan Liu Xihua Yang Zhiguang Li 《水文研究》2018,32(4):576-589
The Loess Plateau has been experiencing large‐scale land use and cover changes (LUCCs) over the past 50 years. It is well known about the significant decreasing trend of annual streamflow and sediment load in the catchments in this area. However, how surface run‐off and sediment load behaved in response to LUCC at flood events remained a research question. We investigated 371 flood events from 1963 to 2011 in a typical medium‐sized catchment within the Plateau in order to understand how LUCC affected the surface run‐off generation and sediment load and their behaviours based on the analysis of return periods. The results showed that the mean annual surface run‐off and sediment load from flood events accounted for 49.6% and 91.8% of their mean annual totals. The reduction of surface run‐off and associated sediment yield in floods explained about 85.0% and 89.2% of declines in the total annual streamflow and sediment load, respectively. The occurrences of flood events and peak sediment concentrations greater than 500 kg/m3 showed a significantly downward trend, yet the counterclockwise loop events still dominated the flood event processes in the catchment. The results suggest that LUCC over the past 50 years resulted in significant changes in the water balance components and associated soil erosion and sediment transportation in the catchment. This was achieved mainly by reducing surface run‐off and sediment yield during floods with return period of less than 5 years. Run‐off–sediment load behaviour during the extreme events with greater than 10‐year return periods has not changed. Outcomes from this study are useful in understanding the eco‐hydrological processes and assisting the sustainable catchment management and land use planning on the Loess Plateau, and the methodologies are general and applicable to similar areas worldwide. 相似文献