全文获取类型
收费全文 | 569篇 |
免费 | 37篇 |
国内免费 | 12篇 |
专业分类
测绘学 | 17篇 |
大气科学 | 46篇 |
地球物理 | 187篇 |
地质学 | 150篇 |
海洋学 | 50篇 |
天文学 | 83篇 |
综合类 | 4篇 |
自然地理 | 81篇 |
出版年
2024年 | 1篇 |
2023年 | 7篇 |
2022年 | 6篇 |
2021年 | 10篇 |
2020年 | 12篇 |
2019年 | 14篇 |
2018年 | 7篇 |
2017年 | 14篇 |
2016年 | 12篇 |
2015年 | 20篇 |
2014年 | 20篇 |
2013年 | 34篇 |
2012年 | 30篇 |
2011年 | 23篇 |
2010年 | 26篇 |
2009年 | 46篇 |
2008年 | 36篇 |
2007年 | 38篇 |
2006年 | 26篇 |
2005年 | 21篇 |
2004年 | 30篇 |
2003年 | 21篇 |
2002年 | 33篇 |
2001年 | 14篇 |
2000年 | 18篇 |
1999年 | 9篇 |
1998年 | 22篇 |
1997年 | 11篇 |
1996年 | 4篇 |
1995年 | 11篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1952年 | 1篇 |
排序方式: 共有618条查询结果,搜索用时 140 毫秒
571.
W. Hamish Mitchell Alexander C. Whittaker Mike Mayall Lidia Lonergan Marco Pizzi 《Basin Research》2021,33(1):186-209
The processes and deposits of deep‐water submarine channels are known to be influenced by a wide variety of controlling factors, both allocyclic and autocyclic. However, unlike their fluvial counterparts whose dynamics are well‐studied, the factors that control the long‐term behaviour of submarine channels, particularly on slopes undergoing active deformation, remain poorly understood. We combine seismic techniques with concepts from landscape dynamics to investigate quantitatively how the growth of gravitational‐collapse structures at or near the seabed in the Niger Delta have influenced the morphology of submarine channels along their length from the shelf edge to their deep‐water counterpart. From a three dimensional (3D), time‐migrated seismic‐reflection volume, which extends over 120 km from the shelf edge to the base of slope, we mapped the present‐day geomorphic expression of two submarine channels and active structures at the seabed, and created a Digital Elevation Model (DEM). A second geomorphic surface and DEM raster—interpreted to closer approximate the most recent active channel geometries—were created through removing the thickness of hemipelagic drape across the study area. The DEM rasters were used to extract the longitudinal profiles of channel systems with seabed expression, and we evaluate the evolution of channel widths, depths and slopes at fixed intervals downslope as the channels interact with growing structures. Results show that the channel long profiles have a relatively linear form with localized steepening associated with seabed structures. We demonstrate that channel morphologies and their constituent architectural elements are sensitive to active seafloor deformation, and we use the geomorphic data to infer a likely distribution of bed shear stresses and flow velocities from the shelf edge to deep water. Our results give new insights into the erosional dynamics of submarine channels, allow us to quantify the extent to which submarine channels can keep pace with growing structures, and help us to constrain the delivery and distribution of sediment to deep‐water settings. 相似文献
572.
573.
Mike Bode, Phil Charles and Carlos Frenk report on a Standing Conference of Astronomy Professors meeting to consider the UK–ESO question, held at the Royal Astronomical Society on 22 June 2000. 相似文献
574.
575.
In North American Land Data Assimilation System Phase 2 (NLDAS‐2) Noah simulation, the NLDAS team introduced an intermediate ‘fix’ to constrain the surface exchange coefficient when the atmospheric boundary layer is stable. In the current NLDAS‐2 Noah version, this fix is used for all stable cases including snow‐free grid cells. In this study, we simply apply this fix to the grid cells in which both stable atmospheric boundary layer and snow exist simultaneously, excluding the snow‐free grid cells as we recognize that the fix in NLDAS‐2 is too strong. We conduct a 31‐year (1979–2009) NLDAS‐2 Noah interim (Noah‐I) run and use observed streamflow, evapotranspiration, land surface temperature, soil temperature, and ground heat flux to evaluate the results, including comparisons with the original NLDAS‐2 Noah run. The results show that Noah‐I has the same performance as NLDAS‐2 Noah for snow water equivalent; however, Noah‐I significantly improved the simulation of other hydrometeorological products as noted earlier when compared with NLDAS‐2 Noah and the observations. This simple modification is being included in the next Noah version used in NLDAS. The hydrometeorological products from the improved NLDAS‐2 Noah‐I are being staged on the National Centers for Environmental Prediction public server. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
576.
577.
578.
Episodic post‐rift deformation in the south‐eastern Australian passive margin: evidence from the Lapstone Structural Complex 下载免费PDF全文
Identifying the influence of neotectonics on the morphology of elevated passive margins is complicated in that major morpho‐structural patterns might plausibly be explained by processes related to late Mesozoic to early Cenozoic rifting and/or differential erosion induced by Cenozoic epeirogenic uplift. The proportional contribution of each process can vary from continent to continent, and potentially even within the same passive margin. In the passive margin setting of the southeast Australian highlands the documented occurrence of neotectonic deformation is rare, and accordingly its role in landscape evolution is difficult to establish. The results of investigations within the Lapstone Structural Complex, which forms the eastern range front of the Blue Mountains Plateau, provide evidence for two periods of Cenozoic neotectonic uplift in this part of the highlands. The first, demonstrated by seismic and structural evidence, is suggested to have occurred in the Paleogene, and is thus unrelated to Cretaceous rifting. The second period, demonstrated by evidence from the Kurrajong Fault (presented herein) suggests that uplift occurred in both the Mio‐Pliocene and the Middle Pleistocene. The cumulative Neogene and younger uplift of ~15 m determined for the Kurrajong Fault is less than 10% of the 130 m of total measured throw across the fault. The apparently minor contribution of neotectonism to the current elevation of the Blue Mountains Plateau supports a predominantly erosional exhumation origin for the topographic relief at the plateau's eastern edge. This finding contrasts with evidence from fault complexes associated with similar topographic relief elsewhere in the south‐eastern highlands, indicating that present‐day topography cannot be directly related to relief generated by Neogene and younger uplift, even from relatively closely‐spaced (< 150 km) structures within the same passive margin. These findings have implications for understanding the spatio‐temporal variability of post‐rift faulting in continental passive margin settings and the evolution of landscapes therein. © Commonwealth of Australia. Earth Surface Processes and Landforms © 2014 John Wiley & Sons, Ltd. 相似文献
579.
580.
During long-lived basaltic eruptions, overflows from lava channels and breaching of channel levées are important processes
in the development of extensive 'a'ā lava flow-fields. Short-lived breaches result in inundation of areas adjacent to the
main channel. However, if a breach remains open, lava supply to the original flow front is significantly reduced, and flow-field
widening is favoured over lengthening. The development of channel breaches and overflows can therefore exert strong control
over the overall flow-field development, but the processes that determine their location and frequency are currently poorly
understood. During the final month of the 2008–2009 eruption of Mt. Etna, Sicily, a remote time-lapse camera was deployed
to monitor events in a proximal region of a small ephemeral lava flow. For over a period of ~10 h, the flow underwent changes
in surface elevation and velocity, repeated overflows of varying vigour and the construction of a channel roof (a required
prelude to lava tube formation). Quantitative interpretation of the image sequence was facilitated by a 3D model of the scene
constructed using structure-from-motion computer vision techniques. As surface activity waned during the roofing process,
overflow sites retreated up the flow towards the vent, and eventually, a new flow was initiated. Our observations and measurements
indicate that flow surface stagnation and flow inflation propagated up-flow at an effective rate of ~6 m h−1, and that these processes, rather than effusion rate variations, were ultimately responsible for the most vigorous overflow
events. We discuss evidence for similar controls during levée breaching and channel switching events on much larger flows
on Etna, such as during the 2001 eruption. 相似文献