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排序方式: 共有978条查询结果,搜索用时 15 毫秒
891.
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PERMAFROSTDEGENERATIONINTHEEASTOFQINGHAI-XIZANGPLATEAU¥ZhuLinnan;WuZiwang;LiuYongzhi;LiDongqing(StateKeyLaboratoryofFrozenSoi... 相似文献
894.
Fissure-fill and tunnel-fill sediments: expressions of permafrost and increased hydrostatic pressure
Risto A. Kumpulainen 《第四纪科学杂志》1994,9(1):59-72
A spectacular network of fissure fillings and pipes (tunnels) cuts Quaternary gravelly delta deposits northeast of Myvatn, precisely on the spreading axis of the North Icelandic rift zone. The delta was formed in an ice-contact lake during deglaciation towards the end of the last glaciation. Subsequently the lake was drained and permafrost conditions developed in these poorly sorted gravel deposits. Hydrostatic pressure was transmitted from the adjacent glacier to the non-frozen core of the delta beneath the discontinuous permafrost crust and the seasonally frozen active layer. Owing to increased hydrostatic pressure, a network of subhorizontal to vertical fissures was opened along the taliks. In these fissures free ground-water flow and sediment transport were established. Tunnel erosion and probably also seepage erosion were associated with these fissures. Subsequently, the fissures and tunnels were filled by laminated fine sediments interbedded with poorly sorted material resulting in the formation of fissure-fill sediments and tunnel-fill sediments. 相似文献
895.
青藏高原东北部15万年来的多年冻土演化 总被引:7,自引:3,他引:7
青藏高原东北部最近15万年中至少存在4次多年冻土强烈扩展时期。第一次发生在140kaBP的倒数第二次冰期,各地广泛发育冰楔;第二次发生在末次冰期早期(80~53kaBP),若尔盖盆地发育融冻扰曲;第三次发生在27~23kaBP,高原东北缘出现冰楔;第四次发生在21~10kaBP,巴颜喀拉山以南地区和若尔盖盆地发育冰楔,黄河源、共和及青海湖周围出现原生砂楔。不考虑构造上升,上述冻土扩展时期多年冻土带下界高度较现代低1700~1800m 相似文献
896.
唐古拉山南麓多年冻土退化与嵩草草甸变化的关系 总被引:9,自引:4,他引:9
测定了分布于唐古拉山南木麓两道河-聂荣高地多年冻土岛和冻土退化后,季节冻土区的两种嵩草草甸群落中各物种的重要值以及群落生态优势度,物种多样性,结合冻土环境对比分析得出,诸多物种重要值发生了明显变化,物种多样性,生态优势度有所增高,这是该区独特的生境特征所导致,另外,草场的特性也发生了改变,应引起畜牧生产者的关注。 相似文献
897.
多年冻土地区线性工程建设 总被引:62,自引:50,他引:62
多年冻土地区修筑建筑物、都会受到冻土稳定性的影响。冻胀、融沉以及由此带来的其它工程冻害问题必须得到重视,处理措施是否得当,直接关系到建筑物的运营安全,在北美及俄罗斯等高纬度多年冻土地区,从已修筑的铁路、公路及输油、气管道等线性工程建筑来看,有成功地的处理冻害的经验,也有对冻害认识不足而造成工程不能运营的失败经验,总结了这些既有工程的建设经验和工程问题治理措施,对我国多年冻土地区线性工程的建设,尤其对青藏铁路建设具有积极的指导意义。 相似文献
898.
Stephen D. Gurney & Peter Worsley 《Geografiska Annaler: Series A, Physical Geography》1997,79(1-2):41-56
An unusually wide variety of pingo landforms located within a relatively restricted 50 km2 area of thick surficial sediments and permafrost is documented. Pingo growth and decay may occur independent of climatic change as witnessed by examples of embryonic, active and collapsed/collapsing features. The presence of deep kettle lakes in the area probably creates a dynamic system of interlinked taliks which influence the groundwater supply to centres of ground ice growth. The field relationships suggest that the pingo growth mechanisms may embrace both hydrostatic and hydraulic processes. All the pingos post-date the Last Glacial Maximum ice retreat and the youngest was actively growing in AD 1981. 相似文献
899.
900.
CHRISTOF KNEISEL Þ. SÆMUNDSSON A.A. BEYLICH 《Geografiska Annaler: Series A, Physical Geography》2007,89(1):41-50
Four different sites in the highlands of central Iceland have been investigated for permafrost occurrence using two‐dimensional resistivity imaging. The results of the surveys indicate the presence of shallow permafrost of low to medium resistivity. The distribution pattern is spatially heterogeneous which is consistent with permafrost at the fringe of seasonal frost. These sites are likely to react rapidly to changes of the environmental boundary conditions, therefore future research should include monitoring for detecting the early impact of climate change on permafrost degradation. The extent to which periglacial morphodynamics and sediment fluxes are influenced by permafrost and/or seasonal frost and potential permafrost degradation is hard to determine. Hence, long‐term monitoring approaches for both permafrost and sediment dynamics are essential. 相似文献