全文获取类型
收费全文 | 707篇 |
免费 | 19篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 12篇 |
大气科学 | 78篇 |
地球物理 | 167篇 |
地质学 | 271篇 |
海洋学 | 57篇 |
天文学 | 86篇 |
综合类 | 3篇 |
自然地理 | 54篇 |
出版年
2021年 | 7篇 |
2020年 | 7篇 |
2018年 | 11篇 |
2016年 | 12篇 |
2014年 | 17篇 |
2013年 | 26篇 |
2012年 | 20篇 |
2011年 | 20篇 |
2010年 | 13篇 |
2009年 | 29篇 |
2008年 | 30篇 |
2007年 | 24篇 |
2006年 | 31篇 |
2005年 | 23篇 |
2004年 | 22篇 |
2003年 | 17篇 |
2002年 | 22篇 |
2001年 | 19篇 |
2000年 | 7篇 |
1999年 | 15篇 |
1998年 | 10篇 |
1997年 | 10篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 10篇 |
1987年 | 8篇 |
1985年 | 5篇 |
1984年 | 8篇 |
1983年 | 11篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1978年 | 8篇 |
1977年 | 12篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1974年 | 9篇 |
1972年 | 11篇 |
1970年 | 7篇 |
1968年 | 6篇 |
1964年 | 5篇 |
1959年 | 5篇 |
1955年 | 7篇 |
1954年 | 9篇 |
1952年 | 6篇 |
1950年 | 8篇 |
1948年 | 8篇 |
排序方式: 共有728条查询结果,搜索用时 640 毫秒
241.
Menzel Peter Teichmann Jakob van den Boogaart Karl Gerald 《Mathematical Geosciences》2020,52(6):731-757
Mathematical Geosciences - Laguerre mosaics have been an important modeling approach in astronomy, physics, crystallography, geology and mathematics for several decades. In materials science, they... 相似文献
242.
Mussel farming is considered a viable means for reducing coastal eutrophication. This study assessed the importance of bioturbation by recolonizing fauna for benthic solute fluxes and porewater distributions in manipulated mussel farm sediments. Three consecutive time-series flux incubations were performed during an experimental period of three weeks in sieved farm sediment treated with the brittle star Amphiura filiformis and the polychaete Nephtys sp. The functional behavior of Nephtys sp. and interactions between Nephtys sp. and the spontaneously colonizing spionid Malacoceros fuliginosus determined the biogeochemical response in the Nephtys sp. treatment. For example, the oxic zone was restricted and benthic nitrate and silicate fluxes were reduced compared to the brittle star treatment. A. filiformis seemed to enhance the bioadvective solute transport, although an increased supply of oxygen was due to the highly reducing conditions of the sediment mainly seen as secondary effects related to porewater distributions and benthic nutrient fluxes. 相似文献
243.
The narrow shelf along the coast of central Vietnam is seasonally supplied by large amounts of sediment from the adjacent
mountainous hinterland following monsoonal precipitation. This study examines the fate of these sediments, and their accumulation
rates along two transects across the shelf, based on analyses of radionuclides (210Pb, 137Cs), sediment texture and structure, as well as carbonate content. The inner shelf is covered by sands, and probably serves
as bypass zone for fine sediments transported offshore. Sediment characteristics suggest that the transport to the mid and
outer shelf is related to flood events. Averaged over the last century, the 210Pb-based mud mass accumulation rates on the mid and outer shelf vary between 0.25 g cm −2 and 0.56 g cm −2 year −1 (corresponding to linear sediment accumulation rates of 0.20–0.47 cm year −1). Along with high excess 210Pb inventories, these high accumulation rates suggest a significant sediment depocentre on the mid shelf. The 210Pb-derived sediment accumulation rates were found to be several times higher than 14C-derived rates previously reported for the Holocene, at the same location on the outer shelf. This is probably due to the
incompleteness of the Holocene record, and an overestimation of the modern rate. Another explanation would be increased erosion
within the rivers’ drainage basins, due to 20th century deforestation. This hypothesis is supported by the difference between
recent (less sand, more lithic grains in the sand fraction) and older sediments. In terms of modern sedimentation processes
and rates, the central Vietnam shelf, although being a part of a narrow passive continental margin, is similar to active flood-dominated
continental margins. 相似文献
244.
The dual isotopes of deep nitrate as a constraint on the cycle and budget of oceanic fixed nitrogen 总被引:1,自引:0,他引:1
Daniel M. Sigman Peter J. DiFiore Mathis P. Hain Curtis Deutsch Yi Wang David M. Karl Angela N. Knapp Moritz F. Lehmann Silvio Pantoja 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(9):1419-1439
We compare the output of an 18-box geochemical model of the ocean with measurements to investigate the controls on both the mean values and variation of nitrate δ15N and δ18O in the ocean interior. The δ18O of nitrate is our focus because it has been explored less in previous work. Denitrification raises the δ15N and δ18O of mean ocean nitrate by equal amounts above their input values for N2 fixation (for δ15N) and nitrification (for δ18O), generating parallel gradients in the δ15N and δ18O of deep ocean nitrate. Partial nitrate assimilation in the photic zone also causes equivalent increases in the δ15N and δ18O of the residual nitrate that can be transported into the interior. However, the regeneration and nitrification of sinking N can be said to decouple the N and O isotopes of deep ocean nitrate, especially when the sinking N is produced in a low latitude region, where nitrate consumption is effectively complete. The δ15N of the regenerated nitrate is equivalent to that originally consumed, whereas the regeneration replaces nitrate previously elevated in δ18O due to denitrification or nitrate assimilation with nitrate having the δ18O of nitrification. This lowers the δ18O of mean ocean nitrate and weakens nitrate δ18O gradients in the interior relative to those in δ15N. This decoupling is characterized and quantified in the box model, and agreement with data shows its clear importance in the real ocean. At the same time, the model appears to generate overly strong gradients in both δ18O and δ15N within the ocean interior and a mean ocean nitrate δ18O that is higher than measured. This may be due to, in the model, too strong an impact of partial nitrate assimilation in the Southern Ocean on the δ15N and δ18O of preformed nitrate and/or too little cycling of intermediate-depth nitrate through the low latitude photic zone. 相似文献
245.
Roberto De Propris Matthew Colless Simon P. Driver Warrick Couch John A. Peacock Ivan K. Baldry Carlton M. Baugh Joss Bland-Hawthorn Terry Bridges Russell Cannon Shaun Cole Chris Collins Nicholas Cross Gavin B. Dalton George Efstathiou Richard S. Ellis Carlos S. Frenk Karl Glazebrook Edward Hawkins Carole Jackson Ofer Lahav Ian Lewis Stuart Lumsden Steve Maddox Darren S. Madgwick Peder Norberg Will Percival Bruce Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2003,342(3):725-737
246.
247.
Participatory and Integrated Research in Mountainous Regions of Thailand and Vietnam: Approaches and Lessons Learned 总被引:1,自引:1,他引:0
Andreas Neef Franz Heidhues Karl Stahr Pittaya Sruamsiri 《山地科学学报》2006,3(4):305-324
Introduction Until the late 1980s, the mountainous regions of northern Thailand and northern Vietnam were largely cut off from the rapid economic develop- ment in the urban centers such as Bangkok, Chiang Mai and Hanoi, and from the dynamics of the ‘gree… 相似文献
248.
249.
Chris Blake Michael B. Pracy Warrick J. Couch Kenji Bekki Ian Lewis Karl Glazebrook Ivan K. Baldry Carlton M. Baugh Joss Bland-Hawthorn Terry Bridges Russell Cannon Shaun Cole Matthew Colless Chris Collins Gavin Dalton Roberto De Propris Simon P. Driver George Efstathiou Richard S. Ellis Carlos S. Frenk Carole Jackson Ofer Lahav Stuart Lumsden Steve Maddox Darren Madgwick Peder Norberg John A. Peacock Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2004,355(3):713-727
250.
Impulse-response-function (IRF) models are designed for applications requiring a large number of climate change simulations,
such as multi-scenario climate impact studies or cost-benefit integrated-assessment studies. The models apply linear response
theory to reproduce the characteristics of the climate response to external forcing computed with sophisticated state-of-the-art
climate models like general circulation models of the physical ocean-atmosphere system and three-dimensional oceanic-plus-terrestrial
carbon cycle models. Although highly computer efficient, IRF models are nonetheless capable of reproducing the full set of
climate-change information generated by the complex models against which they are calibrated. While limited in principle to
the linear response regime (less than about 3 ∘C global-mean temperature change), the applicability of the IRF model presented has been extended into the nonlinear domain
through explicit treatment of the climate system's dominant nonlinearities: CO2 chemistry in ocean water, CO2 fertilization of land biota, and sublinear radiative forcing. The resultant nonlinear impulse-response model of the coupled
carbon cycle-climate system (NICCS) computes the temporal evolution of spatial patterns of climate change for four climate
variables of particular relevance for climate impact studies: near-surface temperature, cloud cover, precipitation, and sea
level. The space-time response characteristics of the model are derived from an EOF analysis of a transient 850-year greenhouse
warming simulation with the Hamburg atmosphere-ocean general circulation model ECHAM3-LSG and a similar response experiment
with the Hamburg carbon cycle model HAMOCC. The model is applied to two long-term CO2 emission scenarios, demonstrating that the use of all currently estimated fossil fuel resources would carry the Earth's climate
far beyond the range of climate change for which reliable quantitative predictions are possible today, and that even a freezing
of emissions to present-day levels would cause a major global warming in the long term.
Received: 28 January 2000 / Accepted: 9 March 2001 相似文献