全文获取类型
收费全文 | 7453篇 |
免费 | 951篇 |
国内免费 | 810篇 |
专业分类
测绘学 | 1157篇 |
大气科学 | 696篇 |
地球物理 | 1266篇 |
地质学 | 2122篇 |
海洋学 | 2327篇 |
天文学 | 40篇 |
综合类 | 611篇 |
自然地理 | 995篇 |
出版年
2024年 | 22篇 |
2023年 | 50篇 |
2022年 | 130篇 |
2021年 | 202篇 |
2020年 | 230篇 |
2019年 | 252篇 |
2018年 | 188篇 |
2017年 | 341篇 |
2016年 | 281篇 |
2015年 | 335篇 |
2014年 | 432篇 |
2013年 | 496篇 |
2012年 | 443篇 |
2011年 | 462篇 |
2010年 | 431篇 |
2009年 | 462篇 |
2008年 | 499篇 |
2007年 | 510篇 |
2006年 | 489篇 |
2005年 | 401篇 |
2004年 | 377篇 |
2003年 | 288篇 |
2002年 | 310篇 |
2001年 | 252篇 |
2000年 | 198篇 |
1999年 | 234篇 |
1998年 | 158篇 |
1997年 | 147篇 |
1996年 | 89篇 |
1995年 | 86篇 |
1994年 | 88篇 |
1993年 | 72篇 |
1992年 | 52篇 |
1991年 | 44篇 |
1990年 | 32篇 |
1989年 | 29篇 |
1988年 | 28篇 |
1987年 | 15篇 |
1986年 | 6篇 |
1985年 | 16篇 |
1984年 | 12篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1971年 | 1篇 |
排序方式: 共有9214条查询结果,搜索用时 31 毫秒
101.
102.
Jesper Raakjær Dao Manh Son Karl-Johan Stæhr Holger Hovgård Nguyen Thi Dieu Thuy Kristine Ellegaard Frank Riget Dang Van Thi Phung Giang Hai 《Marine Policy》2007
Vietnam is in the process of introducing adaptive management based on indicators and time-series to manage its marine fisheries. The development of indicator-based frameworks for fisheries management has accelerated in recent years. This article describes the suite of indicators being suggested or used in Vietnam including the data-collection system. The Vietnamese approach is supported by an institutional structure consisting of a multi-disciplinary advisory system to facilitate the process of using indicators and to introduce knowledge-based management. The article concludes by identifying current problems and weaknesses and by providing suggestions for future improvement of the system. 相似文献
103.
104.
The Continuous Plankton Recorder (CPR) survey was conceived from the outset as a programme of applied research designed to assist the fishing industry. Its survival and continuing vigour after 70 years is a testament to its utility, which has been achieved in spite of great changes in our understanding of the marine environment and in our concerns over how to manage it. The CPR has been superseded in several respects by other technologies, such as acoustics and remote sensing, but it continues to provide unrivalled seasonal and geographic information about a wide range of zooplankton and phytoplankton taxa. The value of this coverage increases with time and provides the basis for placing recent observations into the context of long-term, large-scale variability and thus suggesting what the causes are likely to be. Information from the CPR is used extensively in judging environmental impacts and producing quality status reports (QSR); it has shown the distributions of fish stocks, which had not previously been exploited; it has pointed to the extent of ungrazed phytoplankton production in the North Atlantic, which was a vital element in establishing the importance of carbon sequestration by phytoplankton.The CPR continues to be the principal source of large-scale, long-term information about the plankton ecosystem of the North Atlantic. It has recently provided extensive information about the biodiversity of the plankton and about the distribution of introduced species. It serves as a valuable example for the design of future monitoring of the marine environment and it has been essential to the design and implementation of most North Atlantic plankton research. 相似文献
105.
We describe industry funded contributions to the assessment of the SNA1 snapper (Pagrus auratus) fishery during the 1990s and discuss the advantages and disadvantages of industry funded research. We also provide background on the history of fisheries management in New Zealand, on the current assessment and management processes, and on the SNA1 snapper fishery. In the SNA1 fishery, the contributions of industry and the cooperation with Government scientists has resulted in high quality assessments. In our opinion, the advantages of industry funded research out weigh the disadvantages and suggest that industry funded assessments are highly desirable and should be an integral part of any management system. 相似文献
106.
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
107.
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
108.
109.
Zhang Jinshan Yu Guohua
Research Engineer River Harbour Department Nanjing Hydraulic Research Institute Nanjing Research Senior Engineer River Harbour Department Nanjing Hydraulic Research Institute Nanjing 《中国海洋工程》1995,(3)
- Based on field investigations, this paper analyzes three types of harbour basinns and navigation channel excavated on seabed in Jiaozhou Bay, get a general rule of deposition for excavated trough, it found that pollution is one of crucial factors resulting in the deposition of the excavated trough in the east shore of Jiaozhou Bay. With these results, it predicted the annual deposition thickness for the excavated trough and disclosed the fact that it can't be deposited deadly during one storm. At the same time, with two-dimensional numerical model, it studied the effects of the excavated trough and the reclamation near shore on tidal cureent and said that the excavated trough can decrease the current velocity passing through the trough about 10- 15%, but only limited inside and near the trough and there are no effect on other regions; reclamation can cut off the pollution sources and no obvious effect on the currents of the Jiaozhou Bay. Connecting the deep trough and Cangkou tidal channel with a new 相似文献
110.
本文对青岛—石臼所沿岸潮流特征进行了分析。实际观测资料表明,这一带潮流具有典型的往复流性质,并有较明显的不对称性和较大的垂直变化。文中指出涨落潮流不对称性是由于余流和分潮流影响的结果。讨论了不对称性随余流和分潮流的变化和潮流垂直梯度的特征。不对称和垂直梯度对泥沙运动和污染扩散的影响在文中也作了阐述。 相似文献