全文获取类型
收费全文 | 6939篇 |
免费 | 625篇 |
国内免费 | 428篇 |
专业分类
测绘学 | 1122篇 |
大气科学 | 330篇 |
地球物理 | 835篇 |
地质学 | 1818篇 |
海洋学 | 1429篇 |
天文学 | 13篇 |
综合类 | 630篇 |
自然地理 | 1815篇 |
出版年
2024年 | 12篇 |
2023年 | 37篇 |
2022年 | 122篇 |
2021年 | 179篇 |
2020年 | 209篇 |
2019年 | 219篇 |
2018年 | 181篇 |
2017年 | 292篇 |
2016年 | 228篇 |
2015年 | 267篇 |
2014年 | 341篇 |
2013年 | 453篇 |
2012年 | 349篇 |
2011年 | 407篇 |
2010年 | 353篇 |
2009年 | 368篇 |
2008年 | 424篇 |
2007年 | 432篇 |
2006年 | 451篇 |
2005年 | 397篇 |
2004年 | 368篇 |
2003年 | 278篇 |
2002年 | 296篇 |
2001年 | 275篇 |
2000年 | 221篇 |
1999年 | 228篇 |
1998年 | 161篇 |
1997年 | 126篇 |
1996年 | 63篇 |
1995年 | 62篇 |
1994年 | 37篇 |
1993年 | 33篇 |
1992年 | 19篇 |
1991年 | 13篇 |
1990年 | 15篇 |
1989年 | 11篇 |
1988年 | 18篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有7992条查询结果,搜索用时 46 毫秒
81.
This paper outlines the structure of the institutions involved in scientific and technological development in France. It points to new trends in French marine policy, and gives details of the country's offshore petroleum technology and nodule mining. 相似文献
82.
Combining indicator trends to assess ongoing changes in exploited fish communities: diagnostic of communities off the coasts of France 总被引:1,自引:1,他引:1
83.
XU Qingyan WANG Jianfeng HUANG Yaojian ZHENG Zhonghui SONG Siyang ZHANG Yongmin SU Wenjin 《海洋学报(英文版)》2004,23(3):541-547
Mangroves are special woody plant communities in the intertidal zone of tropical and subtropical coasts. They prove to be a natural microorganisms and new metabolites storage. In the study of mangrove endophytic fungi metabolites, four new compounds, Compounds 1, 2, 3 and 4, as well as a known octaketide, cytosporone B (5), are isolated from an endophytic fungus, Dothiorella sp., HTF3. They all show cytotoxic activities. The elucidation of these structures is mainly based on 1D/2D NMR and ESI-MS spectral analyses. 相似文献
84.
85.
86.
We propose a framework for enabling a systematic evaluation of a fisheries resource management system, which we define as a feed-back mechanism coupled to a fishery. The resource management system includes four basic functions: diagnostics, intervention, goal setting, and decision making. This model allows for the development of an evaluation framework for fisheries resource management by facilitating a typology of failures. We suggest that the potential for systemic and interdisciplinary learning will be significantly enhanced through the process of developing such a framework. 相似文献
87.
This paper explores the application of the US Sea Grant model of applied research, extension, and education to two case studies in Latin America: Coastal Ecuador and the Gulf of Fonseca. The analysis is based on a series of meetings and roundtables with in-country partners and leaders of the US Sea Grant program. We conclude that the Sea Grant model provides an institutional structure that Latin America lacks and the model's features would improve governance of marine and coastal resources through more effective linkages between coastal communities, universities, and policy/decision makers at local, national, and international levels. 相似文献
88.
89.
Vegetation change and surface elevation dynamics in estuarine wetlands of southeast Australia 总被引:1,自引:1,他引:1
Vertical accretion and surface elevation trends were studied in mangrove and saltmarsh wetlands in southeast Australia. A total of 69 surface elevation tables, each associated with three feldspar marker horizons, was deployed in 10 wetlands across 7 estuaries, and monitored for three years. Saltmarsh and mangrove vegetation distributions were mapped for the same estuaries, and elevation characteristics of the wetlands were modelled. Rates of vertical accretion were found to correlate with tidal range. No relationship was found between rates of vertical accretion and surface elevation increase. A positive relationship was demonstrated between contemporary rates of saltmarsh surface elevation change and longer-term rates of mangrove encroachment into saltmarsh. We conclude that landward mangrove encroachment may be facilitated by local factors contributing to saltmarsh compaction during drought conditions. 相似文献
90.