全文获取类型
收费全文 | 4324篇 |
免费 | 948篇 |
国内免费 | 871篇 |
专业分类
测绘学 | 627篇 |
大气科学 | 118篇 |
地球物理 | 1415篇 |
地质学 | 2352篇 |
海洋学 | 407篇 |
天文学 | 79篇 |
综合类 | 639篇 |
自然地理 | 506篇 |
出版年
2024年 | 12篇 |
2023年 | 46篇 |
2022年 | 95篇 |
2021年 | 129篇 |
2020年 | 171篇 |
2019年 | 204篇 |
2018年 | 177篇 |
2017年 | 216篇 |
2016年 | 214篇 |
2015年 | 246篇 |
2014年 | 268篇 |
2013年 | 306篇 |
2012年 | 287篇 |
2011年 | 271篇 |
2010年 | 201篇 |
2009年 | 240篇 |
2008年 | 259篇 |
2007年 | 295篇 |
2006年 | 278篇 |
2005年 | 215篇 |
2004年 | 219篇 |
2003年 | 191篇 |
2002年 | 162篇 |
2001年 | 160篇 |
2000年 | 142篇 |
1999年 | 132篇 |
1998年 | 145篇 |
1997年 | 125篇 |
1996年 | 138篇 |
1995年 | 110篇 |
1994年 | 102篇 |
1993年 | 88篇 |
1992年 | 69篇 |
1991年 | 52篇 |
1990年 | 41篇 |
1989年 | 54篇 |
1988年 | 30篇 |
1987年 | 16篇 |
1986年 | 13篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1954年 | 7篇 |
排序方式: 共有6143条查询结果,搜索用时 15 毫秒
111.
112.
113.
114.
115.
The Serra Gelada sea cliffs are carved in Mesozoic carbonate rocks belonging to the External Zones of the eastern Betic Cordillera (Alicante, SE Spain). Several normal faults with vertical slips of more than a hundred metres have played an important role in the origin of this coastline. Some previous studies propose that the present cliff morphology was mainly originated by Quaternary fault activity. However, the integration of geomorphological features, stratigraphical and sedimentological data, together with the results of the tectonic analysis of fractures occurring in Serra Gelada, and a detailed study of seismic reflection profiles carried out in the adjacent continental shelf, indicate that these normal faults were active mainly during the late Miocene. Therefore, the Serra Gelada sea cliffs represent a tectonically controlled long-term landscape. Thus, normal faults have not significantly modified the Serra Gelada relief since then. Furthermore, the northern part of the Serra Gelada cliff may be considered as an inherited pre-Quaternary relict palaeocliff since it has only undergone very little erosive recession. 相似文献
116.
Effective timescales of coupling within fluvial systems 总被引:1,自引:0,他引:1
This paper presents a review of the coupling concept in fluvial geomorphology, based mainly on previously published work. Coupling mechanisms link the components of the fluvial system, controlling sediment transport down the system and the propagation of the effects of base-level change up the system. They can be viewed at several scales: at the local scale involving within-hillslope coupling, hillslope-to-channel coupling, and within-channels, tributary junction and reach-to-reach coupling. At larger scales, coupling can be considered as zonal coupling, between major zones of the system or as regional coupling, relating to complete drainage basins. These trends are illustrated particularly by the examples of hillslope-to-channel coupling in the Howgill Fells, northwest England, badland systems in southeast Spain, alluvial fans in Spain, USA and UAE, and base-level-induced dissection of Neogene sedimentary basins in southeast Spain. As the spatial scales increase, so do the timescales involved. Effective temporal scales relate to magnitude and frequency characteristics, recovery time and propagation time, the relative importance changing with the spatial scale. For downsystem coupling at the local scale, the first two are important, with propagation time increasing in importance in larger systems, especially in those involving upsystem coupling related to base-level change. The effective timescales range from the individual event, with a return period of decades, through decadal to century timescales for downsystem coupling, to tens to hundreds of thousands of years for the basinwide response to base-level change. The effective timescales influence the relative importance of factors controlling landform development. 相似文献
117.
118.
119.
冯俊录 《中国地质灾害与防治学报》2003,14(3):136-137,141
北碚醪糟坪泥石流防治工程,在施工中使用了多工艺方法,泥石流前缘采用桩、粱、锚支挡工程,相互连接及帷幕灌浆,改变土质性能,加强稳定性,泥石流中段大胆采用碎石毛石重力坝,阻拦上部泥石流,加上盲沟连接碎石桩和重力坎,排泄地下水、地表水。为了防止泥石流上段北岸继续造成滑塌,在北岸进行护坡桩保护。后缘是根据彻底根治原则,用人工挖孔抗滑桩,桩上端与横粱相连,粱与锚桩连接,切断了泥石流物质来源。该泥石流是地表水和地下水不畅通而引起的,在泥石流中下部修建了盲沟网格,明渠修建在下部外围稳定的土体上,水渠沟沟相通,最后集中排泄到明渠中流走。该泥石流采用综合整治方法,大胆使用碎石桩毛石重力坎,这一工艺获得了理想效果。 相似文献
120.
地表剥蚀作用对地应力场反演的影响 总被引:2,自引:4,他引:2
岩体自重和剥蚀作用都是形成岩体初始应力场的重要因素。在地应力回归分析中,反演所得岩体重度往往大于实测重度。通过算例说明,地表剥蚀作用因素是导致该结果的主要原因,并分析了由此产生的一些工程应用问题。 相似文献