全文获取类型
收费全文 | 41647篇 |
免费 | 19522篇 |
国内免费 | 44995篇 |
专业分类
测绘学 | 4567篇 |
大气科学 | 21880篇 |
地球物理 | 13689篇 |
地质学 | 39289篇 |
海洋学 | 17268篇 |
天文学 | 920篇 |
综合类 | 4941篇 |
自然地理 | 3610篇 |
出版年
2024年 | 304篇 |
2023年 | 717篇 |
2022年 | 1258篇 |
2021年 | 1708篇 |
2020年 | 2577篇 |
2019年 | 5931篇 |
2018年 | 6013篇 |
2017年 | 5718篇 |
2016年 | 5719篇 |
2015年 | 5281篇 |
2014年 | 4685篇 |
2013年 | 5341篇 |
2012年 | 5253篇 |
2011年 | 5047篇 |
2010年 | 5002篇 |
2009年 | 4231篇 |
2008年 | 3557篇 |
2007年 | 3497篇 |
2006年 | 3076篇 |
2005年 | 2868篇 |
2004年 | 3039篇 |
2003年 | 2699篇 |
2002年 | 2499篇 |
2001年 | 2208篇 |
2000年 | 1827篇 |
1999年 | 1667篇 |
1998年 | 1688篇 |
1997年 | 1761篇 |
1996年 | 1355篇 |
1995年 | 1304篇 |
1994年 | 1175篇 |
1993年 | 1153篇 |
1992年 | 987篇 |
1991年 | 730篇 |
1990年 | 699篇 |
1989年 | 583篇 |
1988年 | 494篇 |
1987年 | 387篇 |
1986年 | 311篇 |
1985年 | 247篇 |
1984年 | 274篇 |
1983年 | 163篇 |
1982年 | 199篇 |
1981年 | 143篇 |
1980年 | 109篇 |
1979年 | 114篇 |
1978年 | 48篇 |
1977年 | 46篇 |
1971年 | 53篇 |
1970年 | 44篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
23.
现代黄河三角洲粉土触变性研究及其应用 总被引:5,自引:0,他引:5
通过对现代黄河三角洲砂质粉土和粉质粘土触变性的对比试验研究,阐述了黄河口粉土的触变性。试验结果对解释粉土的失稳机制、解决工程地基的稳定性和防止地质灾害等具有重要的现实意义。 相似文献
24.
StudyonthecharacteristicsofthemarineboundarylayerintheEquatorialPacific¥ZhangZiyuandZhouMingyu(ReceivedAugust21,1993;accepted... 相似文献
25.
C. K. Paull W. Ussler H. G. Greene R. Keaten P. Mitts J. Barry 《Geo-Marine Letters》2003,22(4):227-232
A sediment gravity flow descended through the axis of Monterey Canyon on 20 December 2001 at 13:35 Pacific standard time.
The timing of this event is documented by a current-meter package which recorded an 11.9-dbar pressure increase in less than
10 min and was found 550 m down-canyon from its deployment site, buried completely within a >70-cm-thick gravity flow deposit.
This event is believed to have started in less than 290 m of water because an instrument at this location was also lost at
the same time. A 178-cm core collected after the event from the axis of the canyon at 1,297-m water depth contained fresh,
greenish, chlorophyll-rich organic material at 32-cm sub-bottom depth, suggesting the event extended to this water depth.
The only trigger identified for this mass movement event appears to be moderate sea and surf conditions. Thus, gravity flow
events of this magnitude do not require an exceptional triggering event. 相似文献
26.
- In order to employ cost effective frequency domain analysis for off-shore structures treatment of hydrodynamic loading is essential. Drag and inertia dominated, resonating and antiresonating cases under random sea states are analyzed to highlight the implications and relative merits of four salient linearization techniques. 相似文献
27.
The properties of salinity in the South China Sea (SCS), a significant marginal sea connecting the Pacific andIndian Oceans, are greatly influenced by the transport of fresh water flux between the two oceans. However, the long-termchanges in the intermediate water in the SCS have not been thoroughly studied due to limited data, particularly in relationto its thermodynamic variations. This study utilized reanalysis data products to identify a 60-year trend of freshening in theintermediate waters of the northern South China Sea (NSCS), accompanied by an expansion of low-salinity water. Thestudy also constructed salinity budget terms, including advection and entrainment processes, and conducted an analysis ofthe salinity budget to understand the impacts of external and internal dynamic processes on the freshening trend of theintermediate water in the NSCS. The analysis revealed that the freshening in the northwest Pacific Ocean and theintensification of intrusion through the Luzon Strait at intermediate levels are the primary drivers of the salinity changes inthe NSCS. Additionally, a weakened trend in the intensity of vertical entrainment also contributes to the freshening in theNSCS. This study offers new insights into the understanding of regional deep sea changes in response to variations in boththermodynamics and oceanic dynamic processes. 相似文献
28.
视电阻率定义在电法勘探中得到广泛的应用。目前在频率域电磁法中常常采用远区视电阻率定义。由于在频率域中收发距并非足够大,以致在低频段远区定义视电阻率往往不能反映地下电阻率值。我们定义全区电阻率及引入校正系数K,经二层三层模型及野外实测资料的计算,证明了方法的有效性。 相似文献
29.
30.