全文获取类型
收费全文 | 2214篇 |
免费 | 440篇 |
国内免费 | 536篇 |
专业分类
测绘学 | 163篇 |
大气科学 | 305篇 |
地球物理 | 550篇 |
地质学 | 1345篇 |
海洋学 | 364篇 |
天文学 | 107篇 |
综合类 | 152篇 |
自然地理 | 204篇 |
出版年
2024年 | 21篇 |
2023年 | 62篇 |
2022年 | 116篇 |
2021年 | 162篇 |
2020年 | 130篇 |
2019年 | 152篇 |
2018年 | 141篇 |
2017年 | 155篇 |
2016年 | 163篇 |
2015年 | 161篇 |
2014年 | 173篇 |
2013年 | 179篇 |
2012年 | 145篇 |
2011年 | 163篇 |
2010年 | 149篇 |
2009年 | 137篇 |
2008年 | 122篇 |
2007年 | 105篇 |
2006年 | 72篇 |
2005年 | 74篇 |
2004年 | 40篇 |
2003年 | 67篇 |
2002年 | 69篇 |
2001年 | 47篇 |
2000年 | 51篇 |
1999年 | 38篇 |
1998年 | 31篇 |
1997年 | 36篇 |
1996年 | 26篇 |
1995年 | 19篇 |
1994年 | 11篇 |
1993年 | 12篇 |
1992年 | 18篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 13篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 9篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 10篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1954年 | 6篇 |
排序方式: 共有3190条查询结果,搜索用时 15 毫秒
21.
22.
Combined Digital Photogrammetry and Time-of-Flight Laser Scanning for Monitoring Cliff Evolution 总被引:4,自引:0,他引:4
Michael Lim David N. Petley Nicholas J. Rosser Robert J. Allison Antony J. Long David Pybus 《The Photogrammetric Record》2005,20(110):109-129
Although cliffs form approximately 75% of the world's coastline, the understanding of the processes through which they evolve remains limited because of a lack of quantitative data on the morphological changes they undergo. In this paper the combination of terrestrial time-of-flight laser scanning with high-resolution digital photogrammetry is examined to generate high-quality data-sets pertaining to the geomorphic processes governing cliff development. The study was undertaken on a section of hard rock cliffs in North Yorkshire, UK, which has been monitored over a 12-month period. High-density, laser-scanned point clouds have been used to produce an accurate representation of these complex surfaces, free from the optical variations that degrade photographic data. These data-sets have been combined with high-resolution photographic monitoring, resampled with the fixed accuracies of the terrestrial laser survey, to generate a new approach to recording the volumetric changes in complex coastal cliffs. This has led to significant improvements in the understanding of the activity patterns of coastal cliffs. 相似文献
23.
24.
一种新的储层孔隙成因类型--石英溶解型次生孔隙 总被引:26,自引:2,他引:26
石英作为碎屑岩储层中的一种难溶组分,普遍认为它和次生孔隙的形成关系不十分密切。研究认为泌阳凹陷核桃园组储层中的碎屑石英颗粒存在明显的溶解现象,并形成以石英直接溶解型孔隙为主的储集空间特征。石英颗粒被溶解的部分在薄片中所占的范围为 2 %~ 7%者常见,高者达 8%以上,在总孔隙中所占的相对含量也多数在10 %~ 35 %之间,早成岩B期是其最主要形成期。石英溶解型次生孔隙的大量存在为碎屑岩储层中SiO2 胶结物及次生孔隙成因等问题的解释以及储层预测和评价提供了新的可能性。 相似文献
25.
Core A9-EB2 from the eastern Bransfield Basin, Antarctic Peninsula, consists of pelagic (diatom ooze-clay couplets and bioturbated diatom ooze) and hemipelagic (bioturbated mud) sediments interbedded with turbidites (homogeneous mud and silt–clay couplets). The cyclic and laminated nature of these pelagic sediments represents alternation between the deposition of diatom-rich biogenic sediments and of terrigenous sediments. Sediment properties and geochemical data explain the contrasting lamination, with light layers being finer-grained and relatively rich in total organic carbon and biogenic silica content. Also, the high-resolution magnetic susceptibility (MS) variations highlight distinct features: high MS values coincide with clastic-rich sections and low MS values correspond to biogenic sections. The chronology developed for core A9-EB2 accounts for anomalous ages associated with turbidites and shows a linear sedimentation rate of approximately 87 cm/103 yr, which is supported by an accumulation rate of 80 cm/103 yr calculated from 210Pb activity. The late Holocene records clearly identify Neoglacial events of the Little Ice Age (LIA) and Medieval Warm Period (MWP). Other unexplained climatic events comparable in duration and amplitude to the LIA and MWP events also appear in the MS record, suggesting intrinsically unstable climatic conditions during the late Holocene in the Bransfield Basin of Antarctic Peninsula. 相似文献
26.
27.
28.
Through the accurate determination of hypocenter location,the measurement of the main focal mechanism solutions and the analyses of time dependent processes for Sichuan Mianzhu earthquake sequence with Ms=5.0 occurred along the middle segment of Longmenshan fault zone on November 30,1999,the distribution of focal depth section,the stress relase and seismicity features are given to reveal the earthquake-geneating structure of the earthquake sequence.The obtained results show the activity features for this sequence as follows:(1) There is no obvious foreshock,the accumulated strain energy releases in nearly pulse way,fluctuation of the seismic activity level is not quite evident during the duration of the sequence,and the statistical relation between the large events and the small events is less compatible with the traditional G-R estimation;(2) The epicenters of the earthquake sequence are not distributed on the main Longmenshan piedmont faults emerging out ground,but near the hidden Longmenshan piedmont faults.The direction of epicenter distribution is not very coincident with the fault strikes.The microscopic epicenters are relatively far from the macroscopic epicenters,The focal depths range from 5km to 16km;(3) The fractures of focal fault plane with the NE strike appear out the strike-slip displacement with a few overthrust components under the major principal compressive stress of NNE direction.From these,we consider it should be paid more attentions to the underground hidden faults near the ground fault zone on a large scale for their generating earthquake risk. 相似文献
29.
以大平山铜矿、天台山黄铁矿矿为例,阐述了该区的矿区、矿床地质及火山机构特征,并从成矿时间、空间及成因三个方面论述了矿床成矿与古火山机构的关系。 相似文献
30.