全文获取类型
收费全文 | 116篇 |
免费 | 4篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 9篇 |
地球物理 | 25篇 |
地质学 | 45篇 |
海洋学 | 19篇 |
天文学 | 14篇 |
综合类 | 2篇 |
自然地理 | 6篇 |
出版年
2022年 | 2篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 1篇 |
2016年 | 4篇 |
2015年 | 4篇 |
2014年 | 9篇 |
2013年 | 9篇 |
2012年 | 11篇 |
2011年 | 7篇 |
2010年 | 6篇 |
2009年 | 9篇 |
2008年 | 6篇 |
2007年 | 6篇 |
2006年 | 5篇 |
2005年 | 5篇 |
2004年 | 2篇 |
2003年 | 3篇 |
2002年 | 5篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1993年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1974年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有123条查询结果,搜索用时 15 毫秒
1.
Mercedes García-Muoz Javier Arístegui María F. Montero Eric D. Barton 《Progress in Oceanography》2004,62(2-4):115
The distribution and transport of chlorophyll a (Chla), particulate (POC) and dissolved (DOC) organic carbon, and the respiratory ETS activity of the microplankton community were studied along a filament-eddy system located in the transition zone between the NW Africa upwelling and Canary Islands waters. Two independent filaments (F1 and F2) stemming from the coastal jet, between Cape Juby and Cape Bojador, merged about 100 km offshore, turning southward and onshore forced by the circulation of a recurrent oceanic cyclonic eddy. In general, the coastal upwelling waters presented higher Chla, but lower POC, DOC and ETS activity than filament waters. However, differences in organic carbon distribution and respiratory activity were observed among stations from the two filaments. The bio-chemical fields were strongly influenced by a complex sub-mesoscale hydrography resulting from the interaction of cyclonic and anticyclonic island eddies with the filaments. The combined F1 + F2 filament system transported 97.1 kg s−1 of excess (non-refractory) total organic carbon (e-TOC), a value comparable to other published estimates from upwelling filaments in the NE Atlantic. About 90% of e-TOC was exported as DOC, since eddy re-circulation precluded the offshore transport of POC. Assuming that the calculated transport of e-TOC is representative of the annual average, the yearly offshore transport (3.1 x 109 kg C) would represent about 25% of the upwelling primary production of the region of study. 相似文献
2.
During October 2003 an intensive oceanographic survey (BIOMEGA) was carried out in the Alboran Sea, coinciding with a migration event of the Western Alboran Sea Gyre (WAG). The observations gathered during that cruise constitute the first field evidence of a migrated stage of the WAG. In this work we present the main differences between the 3D hydrodynamic fields observed during BIOMEGA and those corresponding to a WAG located at its usual position. The migration of the gyre was followed by satellite (altimetry and sea surface temperature) imagery. The causes of the gyre migration are explored in terms of the quasi-geostrophic tendency equation, in particular of the dynamics governing scales larger than the Rossby radius of deformation. It is shown that the steady state gyre must be almost equivalent barotropic and that the key process to break down the stationarity would be a density advection at gyre scale. The mechanisms to explain the migration of the WAG proposed by previous authors are discussed in light of the explanation proposed in this work. 相似文献
3.
4.
Artur Chahud Gisele Ferreira Figueiredo Gabriela Sartori Mingatos Mercedes Okumura 《第四纪科学杂志》2021,36(7):1268-1278
The Lapa do Santo archaeological site, located in the Lagoa Santa region, Brazil, represents an important hunter-gatherer occupation dated from the Early and Middle Holocene. Prior studies of archaeofauna dating to this period are few and most of them only provide basic faunal identification with limited information on taphonomic processes. The main goal of this study is to identify the archaeofauna, record the taphonomic processes, and make inferences about its natural (interpreted as the death of the animal in the rockshelter area due to natural causes or due to predation) or anthropic origins. No extinct species (including megamastofauna) were identified. Taxonomic analysis indicated that most faunal remains consist of taxa that may be of mixed origin (natural or anthropic), such as microvertebrates and carnivorous mammals. The Cervidae are the main vertebrate family found in the studied material and these are likely the result of hunting. The Cervidae Ozotoceros support the presence of a fauna that is typical of savannah environments, although the assemblage contains mostly generalist fauna that can thrive in a variety of environments. Very few remains showed clear evidence for taphonomic processes related to human interaction, such as burnt bones. 相似文献
5.
6.
Serpentinites are metamorphic rocks formed from the alteration of ultramafic igneous rocks. Their precursors largely consist of clinopyroxene, orthopyroxene, olivine and a member of the spinel group, along with other accessory minerals. Serpentinization can be produced through the percolation of fluids of different origins. The transformation gives rise to other rocks, serpentinites, that are characterized by a high‐water content mineralogy (serpentine) and, sometimes, remnants of the original phases. However, serpentinites may also undergo a subsequent carbonation process, transforming most of the mineral phases into carbonates. This is why confusion may arise when dealing with these rocks in the industrial sector, where geologists are not often involved. Serpentinites are often found in natural stone catalogues under the name of ‘green marble’ and this can be misinterpreted by builders and architects, causing misuse of this rock as an ornamental stone. 相似文献
7.
Nathalie van Vliet Ole Mertz Andreas Heinimann Tobias Langanke Unai Pascual Birgit Schmook Cristina Adams Dietrich Schmidt-Vogt Peter Messerli Stephen Leisz Jean-Christophe Castella Lars Jørgensen Torben Birch-Thomsen Cornelia Hett Thilde Bech-Bruun Amy Ickowitz Kim Chi Vu Kono Yasuyuki Jefferson Fox Christine Padoch Alan D. Ziegler 《Global Environmental Change》2012,22(2):418-429
This meta-analysis of land-cover transformations of the past 10–15 years in tropical forest-agriculture frontiers world-wide shows that swidden agriculture decreases in landscapes with access to local, national and international markets that encourage cattle production and cash cropping, including biofuels. Conservation policies and practices also accelerate changes in swidden by restricting forest clearing and encouraging commercial agriculture. However, swidden remains important in many frontier areas where farmers have unequal or insecure access to investment and market opportunities, or where multi-functionality of land uses has been preserved as a strategy to adapt to current ecological, economic and political circumstances. In some areas swidden remains important simply because intensification is not a viable choice, for example when population densities and/or food market demands are low. The transformation of swidden landscapes into more intensive land uses has generally increased household incomes, but has also led to negative effects on the social and human capital of local communities to varying degrees. From an environmental perspective, the transition from swidden to other land uses often contributes to permanent deforestation, loss of biodiversity, increased weed pressure, declines in soil fertility, and accelerated soil erosion. Our prognosis is that, despite the global trend towards land use intensification, in many areas swidden will remain part of rural landscapes as the safety component of diversified systems, particularly in response to risks and uncertainties associated with more intensive land use systems. 相似文献
8.
9.
Xavier Rodó Mercedes Pascual Francisco J. Doblas-Reyes Alexander Gershunov Dáithí A. Stone Filippo Giorgi Peter J. Hudson James Kinter Miquel-Àngel Rodríguez-Arias Nils Ch. Stenseth David Alonso Javier García-Serrano Andrew P. Dobson 《Climatic change》2013,118(3-4):625-640
The next generation of climate-driven, disease prediction models will most likely require a mechanistically based, dynamical framework that parameterizes key processes at a variety of locations. Over the next two decades, consensus climate predictions make it possible to produce forecasts for a number of important infectious diseases that are largely independent of the uncertainty of longer-term emissions scenarios. In particular, the role of climate in the modulation of seasonal disease transmission needs to be unravelled from the complex dynamics resulting from the interaction of transmission with herd immunity and intervention measures that depend upon previous burdens of infection. Progress is also needed to solve the mismatch between climate projections and disease projections at the scale of public health interventions. In the time horizon of seasons to years, early warning systems should benefit from current developments on multi-model ensemble climate prediction systems, particularly in areas where high skill levels of climate models coincide with regions where large epidemics take place. A better understanding of the role of climate extremes on infectious diseases is urgently needed. 相似文献
10.
An infinitestimal contact transformation is proposed to simplify at first order the Hamiltonian representing the attitude of a triaxial rigid body on a Keplerian orbit around a mass point. The simplified problem reduces to the Euler-Poinsot model, but with moments of inertia depending on time through the longitude in orbit. Should the orbit be circular, the moments of inertia would be constant. 相似文献