全文获取类型
收费全文 | 463篇 |
免费 | 62篇 |
国内免费 | 109篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 35篇 |
地球物理 | 90篇 |
地质学 | 57篇 |
海洋学 | 389篇 |
天文学 | 10篇 |
综合类 | 27篇 |
自然地理 | 24篇 |
出版年
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 11篇 |
2020年 | 12篇 |
2019年 | 11篇 |
2018年 | 6篇 |
2017年 | 17篇 |
2016年 | 24篇 |
2015年 | 19篇 |
2014年 | 26篇 |
2013年 | 41篇 |
2012年 | 10篇 |
2011年 | 40篇 |
2010年 | 27篇 |
2009年 | 35篇 |
2008年 | 43篇 |
2007年 | 36篇 |
2006年 | 31篇 |
2005年 | 28篇 |
2004年 | 23篇 |
2003年 | 21篇 |
2002年 | 27篇 |
2001年 | 20篇 |
2000年 | 21篇 |
1999年 | 20篇 |
1998年 | 16篇 |
1997年 | 14篇 |
1996年 | 9篇 |
1995年 | 10篇 |
1994年 | 12篇 |
1993年 | 7篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1989年 | 4篇 |
1986年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有634条查询结果,搜索用时 109 毫秒
41.
Zooplankton research off Peru: A review 总被引:2,自引:1,他引:1
Patricia Ayn Maria I. Criales-Hernandez Ralf Schwamborn Hans-Jürgen Hirche 《Progress in Oceanography》2008,79(2-4):238
A review of zooplankton studies conducted in Peruvian marine waters is given. After a short history of the development of zooplankton research off Peru, we review zooplankton methodology, taxonomy, biodiversity, spatial distribution, seasonal and interannual variability, trophodynamics, secondary production, and modelling. We review studies on several micro-, meso-, macro-, and meroplankton groups, and give a species list from both published and unpublished reports. Three regional zooplankton groups have been identified: (1) a continental shelf group dominated by Acartia tonsa and Centropages brachiatus; (2) a continental slope group characterized by siphonophores, bivalves, foraminifera and radiolaria; (3) and a species-rich oceanic group. The highest zooplankton abundances and biomasses were often found between 4–6°S and 14–16°S, where continental shelves are narrow. Species composition changes with distance from the shore. Species composition and biomass also vary strongly on short time scales due to advection, peaks of larval production, trophic interactions, and community succession. The relation of zooplankton to climatic variability (ENSO and multi-decadal) and fish stocks is discussed in the context of ecological regime shifts. An intermediate upwelling hypothesis is proposed, based on the negative effects of low upwelling intensity in summer or extremely strong and enduring winter upwelling on zooplankton abundance off Peru. According to this hypothesis, intermediate upwelling creates an optimal environmental window for zooplankton communities. Finally, we highlight important knowledge gaps that warrant attention in future. 相似文献
42.
Revisiting Peruvian anchovy (Engraulis ringens) trophodynamics provides a new vision of the Humboldt Current system 总被引:6,自引:4,他引:2
The Peruvian anchovy or anchoveta (Engraulis ringens) forages on plankton and is a main prey for marine mammals, seabirds, fish, and fishers, and is therefore a key element of the food web in the Humboldt Current system (HCS). Here, we present results from the analysis of 21,203 anchoveta stomach contents sampled during 23 acoustic surveys over the period 1996–2003. Prey items were identified to the genus level, and the relative dietary importance of different prey was assessed by determination of their carbon content. Variability in stomach fullness was examined relative to the diel cycle, the distance from the coast, sea surface temperature, and latitude, using generalized additive models (GAMs). Whereas phytoplankton largely dominated anchoveta diets in terms of numerical abundance and comprised >99% of ingested prey items, the carbon content of prey items indicated that zooplankton was by far the most important dietary component, with euphausiids contributing 67.5% of dietary carbon followed by copepods (26.3%). Stomach fullness data showed that anchoveta feed mainly during daytime between 07h00 and 18h00, although night-time feeding also made a substantial contribution to total food consumption. Stomach fullness also varied with latitude, distance from the coast, and temperature, but with substantial variability indicating a high degree of plasticity in anchoveta feeding behaviour. The results suggest an ecological role for anchoveta that challenges current understanding of its position in the foodweb, the functioning of the HCS, and trophic models of the HCS. 相似文献
43.
Marc H. Taylor Jorge Tam Vernica Blaskovic Pepe Espinoza R. Michael Balln Claudia Wosnitza-Mendo Juan Argüelles Erich Díaz Sara Purca Noemi Ochoa Patricia Ayn Elisa Goya Dimitri Gutirrez Luis Quipuzcoa Matthias Wolff 《Progress in Oceanography》2008,79(2-4):366
The Northern Humboldt Current Ecosystem is one of the most productive in the world in terms of fish production. Its location near to the equator permits strong upwelling under relatively low winds, thus creating optimal conditions for the development of plankton communities. These communities ultimately support abundant populations of grazing fish such as the Peruvian anchoveta, Engraulis ringens. The ecosystem is also subject to strong inter-annual environmental variability associated with the El Niño Southern Oscillation (ENSO), which has major effects on nutrient structure, primary production, and higher trophic levels. Here our objective is to model the contributions of several external drivers (i.e. reconstructed phytoplankton changes, fish immigration, and fishing rate) and internal control mechanisms (i.e. predator-prey) to ecosystem dynamics over an ENSO cycle. Steady-state models and time-series data from the Instituto del Mar del Perú (IMARPE) from 1995 to 2004 provide the base data for simulations conducted with the program Ecopath with Ecosim. In simulations all three external drivers contribute to ecosystem dynamics. Changes in phytoplankton quantity and composition (i.e. contribution of diatoms and dino- and silicoflagellates), as affected by upwelling intensity, were important in dynamics of the El Niño of 1997–98 and the subsequent 3 years. The expansion and immigration of mesopelagic fish populations during El Niño was important for dynamics in following years. Fishing rate changes were the most important of the three external drivers tested, helping to explain observed dynamics throughout the modeled period, and particularly during the post-El Niño period. Internal control settings show a mix of predator–prey control settings; however a “wasp-waist” control of the ecosystem by small pelagic fish is not supported. 相似文献
44.
Sachiko Oguma Tsuneo Ono Akira Kusaka Hiromi Kasai Yasuhiro Kawasaki Tomonori Azumaya 《Journal of Oceanography》2008,64(4):525-539
In this study we used two stable isotopes, δ13C and δ18O, for water mass classification in the coastal region off eastern Hokkaido. δ13C* values, which were corrected for the biological effect, and δ
18O values up to 300 m depth suggested that the isotopic character of the onshore and offshore water in the southern Okhotsk
Sea, the Nemuro Strait and the western North Pacific could be explained by the mixing of three source waters: the Oyashio
water (OYW), Soya Warm Current water (SWCW) and East Sakhalin Current water (ESCW). In summer, δ
13C*-δ
18O plots indicated mixing between SWCW from the southern Okhotsk Sea and OYW in the Pacific coast of southeastern Hokkaido,
while temperature-salinity plots of the onshore water showed minimal difference from the offshore OYW. In winter, on the other
hand, the mixed water of ESCW and OYW (or SWCW) appeared in the Pacific coastal region, distributed as cold, low salinity
onshore water. Finally, we estimated mixing ratios of OYW, SWCW and ESCW in the coastal region of western North Pacific using
their mean values of δ
13C* and δ
18O as endmembers. These results suggest seasonal and yearly changes of water mass combination en route from the southern Okhotsk
Sea to the western North Pacific. 相似文献
45.
The origin of the Ryukyu Current(RC) and the formation of its subsurface velocity core were investigated using a 23-year(1993–2015) global Hybrid Coordinate Ocean Model(HYCOM) dataset. The volume transport of the RC comes from the Kuroshio eastward branch(KEB) east of Taiwan and part of the North Pacific Subtropical Gyre(pNPSG). From the surface to 2 000 m depth, the KEB(p-NPSG) transport contributes 41.5%(58.5%) to the mean total RC transport. The KEB originally forms the subsurface velocity core of the RC east of Taiwan due to blockage of the subsurface Kuroshio by the Ilan Ridge(sill depth: 700 m). Above 700 m, the Kuroshio can enter the East China Sea(ECS) over the Ilan Ridge, meanwhile, the blocked Kuroshio below 700 m turns to the right and flows along the Ryukyu Islands. With the RC flowing northeastward, the p-NPSG contribution strengthens the subsurface maximum structure of the RC owing to the blockage of the Ryukyu Ridge. In the surface layer, the pNPSG cannot form a stable northeastward current due to frequent disturbance by mesoscale eddies and water exchange through the gaps(with net volume transport into ECS) between the Ryukyu Islands. 相似文献
46.
47.
48.
49.
Chang?-Woong?ShinEmail author Cheolsoo?Kim Sang?-Kyung?Byun Dongchull?Jeon Sang?-Chull?Hwang 《Ocean Science Journal》2006,41(4):291-299
Hydrographic surveys were carried out four times in the western channel of the Korea Strait in March and August 2003 and in
June and November 2004. The bottom cold water, which was lower than 10°C, appeared in the channel trough except in March 2003.
It flowed southwestward along the shelf of Korean coasts in August 2003 and in November 2004. The width and the maximum speed
of the intrusion current were about 20 km and approximately 25 cm s-1, respectively, off Ulsan, Korea. The volume transport of the bottom cold water was estimated 0.019 Sv (Sv≡106 m3 s-1) in August 2003 and 0.026 Sv in November 2004. 相似文献
50.
利用EN4(the UK Met Office EN4.2.1 analyses)盐度数据发现北太平洋副热带高盐中心——北太平洋热带水(NPTW)的海表面积与体积在2000—2008年、2014—2017年存在下降趋势,2008—2014年期间存在上升趋势,进一步的研究表明,这些变化与太平洋年代际震荡(PDO)的位相转换紧密相关。利用淡水通量数据以及ECCO2(Circulation and Climate of the Ocean, Phase II)流场数据计算分析后表明,淡水通量对NPTW的变化贡献较小,而水平输运对NPTW的表面积以及体积变化贡献较大,这与PDO正(负)位相期间北赤道流(NEC)的向北(南)摆动有关。 相似文献