全文获取类型
| 收费全文 | 20682篇 |
| 免费 | 3837篇 |
| 国内免费 | 4792篇 |
专业分类
| 测绘学 | 1048篇 |
| 大气科学 | 4165篇 |
| 地球物理 | 5339篇 |
| 地质学 | 10423篇 |
| 海洋学 | 2363篇 |
| 天文学 | 908篇 |
| 综合类 | 2450篇 |
| 自然地理 | 2615篇 |
出版年
| 2024年 | 28篇 |
| 2023年 | 307篇 |
| 2022年 | 880篇 |
| 2021年 | 981篇 |
| 2020年 | 856篇 |
| 2019年 | 943篇 |
| 2018年 | 1172篇 |
| 2017年 | 1048篇 |
| 2016年 | 1241篇 |
| 2015年 | 939篇 |
| 2014年 | 1223篇 |
| 2013年 | 1228篇 |
| 2012年 | 1136篇 |
| 2011年 | 1207篇 |
| 2010年 | 1136篇 |
| 2009年 | 1150篇 |
| 2008年 | 1022篇 |
| 2007年 | 987篇 |
| 2006年 | 780篇 |
| 2005年 | 839篇 |
| 2004年 | 584篇 |
| 2003年 | 617篇 |
| 2002年 | 608篇 |
| 2001年 | 571篇 |
| 2000年 | 677篇 |
| 1999年 | 1011篇 |
| 1998年 | 814篇 |
| 1997年 | 884篇 |
| 1996年 | 815篇 |
| 1995年 | 681篇 |
| 1994年 | 564篇 |
| 1993年 | 509篇 |
| 1992年 | 395篇 |
| 1991年 | 289篇 |
| 1990年 | 231篇 |
| 1989年 | 179篇 |
| 1988年 | 174篇 |
| 1987年 | 126篇 |
| 1986年 | 104篇 |
| 1985年 | 70篇 |
| 1984年 | 50篇 |
| 1983年 | 43篇 |
| 1982年 | 36篇 |
| 1981年 | 27篇 |
| 1980年 | 35篇 |
| 1979年 | 27篇 |
| 1978年 | 15篇 |
| 1976年 | 11篇 |
| 1975年 | 14篇 |
| 1958年 | 18篇 |
排序方式： 共有10000条查询结果，搜索用时 343 毫秒
991.
992.
993.
994.
995.
Q. H. Liu Y. Shu X. M. Zhu X. H. Yang M. Tan 《Australian Journal of Earth Sciences》2016,63(7):903-922
The effects of low- to high-angle (>30°) normal faults on sedimentary architectural units in the Eocene Wenchang Formation, Enping Sag, Pearl River Mouth Basin (PRMB), South China Sea were investigated utilising a high-quality 3D seismic data set and restored paleogeomorphology. It has been shown that sequence stratigraphic units and sedimentary architecture are significantly controlled by the low- to high-angle normal faults. The Wenchang Formation, a second-order sequence, can be subdivided into two para-second-sequences (the Lower and Upper Wenchang sequences, E2WL and E2WU) and seven third-order sequences (from base to top: SQ1～SQ7). The low-angle fault confined sequence architecture of the Wenchang Formation is mainly characterised by lateral stacking with the ratio of the vertical subsidence (V) to horizontal slip (H) being reduced from 1/2 for E2WL to 1/6 for E2WU. In contrast, the high-angle fault confined sequence is characterised by vertical stacking with the ratio of V/H close to 1 for sequences SQ1 to SQ7. In the 3D seismic area, the features of sediment-dispersal pattern were interpreted based on an integrated analysis of paleogeomorphology, seismic reflection characteristics, stratal thickness distribution and multiple attribute clustering. The results show that the large-scale fan delta, belt-shape lacustrine deposit and bird-foot braided delta systems mainly developed in the low-angle fault confined sequences, whereas small-scale fan delta, rhombus-shaped lacustrine deposit and lobe-shaped braided delta systems inherited tectono-sedimentary architectures in the high-angle fault confined sequences. 相似文献
996.
During the deposition of the Chang-7 (Ch-7) and Chang-6 (Ch-6) units in the Upper Triassic, gravity flows were developed widely in a deep lake in the southwestern Ordos Basin, China. Based on cores, outcrops, well-logs and well-testing data, this paper documents the sedimentary characteristics of the gravity-flow deposits and constructs a depositional model. Gravity-flow deposits in the study area comprise seven lithofacies types, which are categorised into four groups: slides and slumps, debris-flow-dominated lithofacies, turbidity-current-dominated lithofacies, and deep-water mudstone-dominated lithofacies. The seven lithofacies form two sedimentary entities: sub-lacustrine fan and the slump olistolith, made up of three and two lithofacies associations, respectively. Lithofacies association 1 is a channel–levee complex with fining-/thinning-upward sequences whose main part is characterised by sandy debris flow-dominated, thick-bedded massive sandstones. Lithofacies association 2 represents distributary channelised lobes of sub-lacustrine fans, which can be further subdivided into distributary channel, channel lateral margin and inter-channel. Lithofacies association 3 is marked by non-channelised lobes of sub-lacustrine fans, including sheet-like turbidites and deep-lake mudstones. Lithofacies association 4 is represented by proximal lobes of slump olistolith, consisting of slides and slumps. Lithofacies association 5 is marked by distal lobes of slump olistolith, comprising tongue-shaped debris flow lobes and turbidite lobes. It is characterised by sandy debris flow, muddy debris flow-dominated sandstone and sandstone with classic Bouma sequences. Several factors caused the generation of gravity flows in the Ordos Basin, including sediment supply, terrain slope and external triggers, such as volcanisms, earthquakes and seasonal floods. The sediment supply of sub-lacustrine fan was most likely from seasonal floods with a high net-to-gross and incised channels. Triggered by volcanisms and earthquakes, the slump olistolith is deposited by the slumping and secondary transport of unconsolidated sediments in the delta front or prodelta with a low net-to-gross and no incised channels. 相似文献
997.
The mechanisms behind the seasonal deepening of the mixed layer(ML) in the subtropical Southeast Pacific were investigated using the monthly Argo data from 2004 to 2012. The region with a deep ML(more than 175 m) was found in the region of(22?–30?S, 105?–90?W), reaching its maximum depth(～200 m) near(27?–28?S, 100?W) in September. The relative importance of horizontal density advection in determining the maximum ML location is discussed qualitatively. Downward Ekman pumping is key to determining the eastern boundary of the deep ML region. In addition, zonal density advection by the subtropical countercurrent(STCC) in the subtropical Southwest Pacific determines its western boundary, by carrying lighter water to strengthen the stratification and form a "shallow tongue" of ML depth to block the westward extension of the deep ML in the STCC region. The temperature advection by the STCC is the main source for large heat loss from the subtropical Southwest Pacific. Finally, the combined effect of net surface heat flux and meridional density advection by the subtropical gyre determines the northern and southern boundaries of the deep ML region: the ocean heat loss at the surface gradually increases from 22?S to 35?S, while the meridional density advection by the subtropical gyre strengthens the stratification south of the maximum ML depth and weakens the stratification to the north. The freshwater flux contribution to deepening the ML during austral winter is limited. The results are useful for understanding the role of ocean dynamics in the ML formation in the subtropical Southeast Pacific. 相似文献
998.
999.
1000.