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321.
Alphonse Nahon Déborah Idier Nadia Sénéchal Hugues Féniès Cyril Mallet Julie Mugica 《地球表面变化过程与地形》2019,44(11):2112-2125
In coastal areas, sea level rise (SLR) and changing wave climates are expected to be the main oceanic drivers of shoreline adjustments. These drivers have been shown to vary on a wide spectrum of spatial and temporal scales. Nonetheless, a general rule about how this variability impacts global shorelines remains to be articulated. Here, we discuss the impacts of wave climate changes and SLR on the evolution of a barrier spit–inlet system over the last 250 years. The distal end of the Cap Ferret barrier spit, SW France, has undergone large-scale oscillations that were well correlated with variations of the decadal average of the winter North Atlantic Oscillation (NAO) index. The local wave climate hindcast supports that increased alongshore wave energy fluxes associated with the positive phase of the NAO were responsible for the updrift retreat of the spit. By opposition, the spit has elongated downdrift when waves were less energetic and more shore normal, as during the negative phase of the NAO. In addition, lower rates of SLR appeared to be necessary for the spit to develop, as higher rates of SLR very likely forced the adjacent inlet to enlarge, at the expense of the spit. These results should help to predict and detect coastal adjustments driven by climate change and by climate variability. © 2019 John Wiley & Sons, Ltd. 相似文献
322.
Karin Maierhofer Christian Koeberl Julie Brigham‐Grette 《Meteoritics & planetary science》2019,54(10):2510-2531
The 3.6 Ma El'gygytgyn impact structure, located in northeast Chukotka in Arctic Russia, was largely formed in acidic volcanic rocks. The 18 km diameter circular depression is today filled with Lake El'gygytgyn (diameter of 12 km) that contains a continuous record of lacustrine sediments of the Arctic from the past 3.6 Myr. In 2009, El'gygytgyn became the focus of the International Continental Scientific Drilling Program (ICDP) in which a total of 642.4 m of drill core was recovered. Lithostratigraphically, the drill cores comprise lacustrine sediment sequences, impact breccias, and deformed target rocks. The impactite core was recovered from 316.08 to 517.30 meters below lake floor (mblf). Because of the rare, outstanding recovery, the transition zone, ranging from 311.47 to 317.38 m, between the postimpact lacustrine sediments and the impactite sequences, was studied petrographically and geochemically. The transition layer comprises a mixture of about 6 m of loose sedimentary and volcanic material containing isolated clasts of minerals and melt. Shock metamorphic effects, such as planar fractures (PFs) and planar deformation features (PDFs), were observed in a few quartz grains. The discoveries of silica diaplectic glass hosting coesite, kinked micas and amphibole, lechatelierite, numerous impact melt shards and clasts, and spherules are associated with the impact event. The occurrence of spherules, impact melt clasts, silica diaplectic glass, and lechatelierite, about 1 m below the onset of the transition, marks the beginning of the more coherent impact ejecta layer. The results of siderophile interelement ratios of the transition layer spherules give indications of the relative contribution of the meteoritical component. 相似文献
323.
Philipson Bani Clive Oppenheimer Vitchko I. Tsanev Simon A. Carn Shane J. Cronin Rachel Crimp Julie A. Calkins Douglas Charley Michel Lardy Tjarda R. Roberts 《Bulletin of Volcanology》2009,71(10):1159-1168
Volcanoes provide important contributions to atmospheric budgets of SO2 and reactive halogens, which play significant roles in atmospheric oxidative capacity and radiation. However, the global
source strengths of volcanic emissions remain poorly constrained. These uncertainties are highlighted here by the first measurements
of gas emission rates from Ambrym volcano, Vanuatu. Our initial airborne ultraviolet spectroscopic measurements made in January
2005 indicate fluxes of 18–270 kg s-1 of SO2, and 62–110 g s-1 of BrO, into the atmosphere, placing Ambrym amongst the largest known contemporary point sources of both these species on
Earth. We also estimate high Cl and F fluxes of ~8–14 and ~27–50 kg s-1, respectively, for this period. Further observations using both airborne and spaceborne remote sensing reveal a fluctuating
SO2 output between 2004 and 2008, with a surge in the first half of 2005, and underline the substantial contribution that a single
passively degassing volcano can make to the atmospheric budget of sulfur and halogens. 相似文献
324.
Daniel R. Engstrom James E. Almendinger Julie A. Wolin 《Journal of Paleolimnology》2009,41(4):563-588
Long-term changes in sediment and phosphorus loading to the upper Mississippi River were quantified from an array of 25 sediment
cores from Lake Pepin, a large natural impoundment downstream of the Minneapolis-St Paul metropolitan area. Cores were dated
and stratigraphically correlated using 210Pb, 137Cs, 14C, magnetic susceptibility, pollen analysis, and loss-on-ignition. All cores show a dramatic increase in sediment accumulation
beginning with European settlement in 1830. Accumulation rates are highest and show the greatest post-settlement increases
in the upper end of the lake. Present-day sediment-phosphorus concentrations are roughly twice those of pre-settlement times,
and the Fe/Al-bound fraction makes up a greater portion of the total. Diatom assemblages record a marked increase in nutrient
availability over the last 200 years, changing from clear-water benthic forms and mesotrophic planktonic taxa in pre-settlement
times to exclusively planktonic assemblages characteristic of highly eutrophic conditions today. Lake-water total-phosphorus
concentrations, estimated by weighted averaging regression and calibration, increased from 50 to 200 μg l−1 during this period. Sediment loading to Lake Pepin from the Mississippi River has increased by an order of magnitude since
1830. Modern fluxes are about 900,000 metric tons annually, and are more than 80% detrital mineral matter. About 17% of the
lake’s volume in 1830 has been replaced by sediment, and at current accumulation rates the remainder will be filled in another
340 years. Phosphorus accumulation in Lake Pepin sediments has increased 15-fold since 1830, rising from 60 to 900 metric
tons annually. This rise represents a sevenfold increase in phosphorus loading from the Mississippi River coupled with more
efficient retention of phosphorus inflows by bottom sediments. More efficient trapping of phosphorus in Lake Pepin over the
last century resulted from higher rates of sediment burial. The most dramatic changes in nutrient and sediment inputs to Lake
Pepin have occurred since 1940, although gradual increases began shortly following European settlement. Sediment accumulation
rates rose sharply between 1940 and 1970 and then leveled off, while phosphorus inflows record their largest increases after
1970.
This is one of eight papers dedicated to the “Recent Environmental History of the Upper Mississippi River” published in this
special issue of the Journal of Paleolimnology. D. R. Engstrom served as guest editor of the special issue. 相似文献
325.
Mathematical Geosciences - The aim of this work is to demonstrate how geologically interpretative features can improve machine learning facies classification with uncertainty assessment. Manual... 相似文献
326.
This article explores the urban governmentalities that are emerging through the discursive constitution of cycling as a form of sustainable transport. It has two main aims. The first is to explore and critique the strategies and discourses used to promote cycling as a sustainable form of transport. We argue that cycling advocacy displays totalising tendencies which obscure social and cultural difference, ignore the embodied and affective dimensions of transport practices and fail in part to apprehend the heterogeneity of environmental responsibility. Our second aim is to tentatively suggest a more productive way of knowing and talking about cycling that might be constitutive of a less exclusionary affective ethical sensibility. 相似文献
327.
The Monitoring Network of the Vancouver 2010 Olympics 总被引:1,自引:0,他引:1
Paul Joe Bill Scott Chris Doyle George Isaac Ismail Gultepe Douglas Forsyth Stewart Cober Edwin Campos Ivan Heckman Norman Donaldson David Hudak Roy Rasmussen Paul Kucera Ron Stewart Julie M. Thériault Teresa Fisico Kristen L. Rasmussen Hannah Carmichael Alex Laplante Monika Bailey Faisal Boudala 《Pure and Applied Geophysics》2014,171(1-2):25-58
328.
329.
Environmental management of military activities is of growing global concern by defence forces. As one of the largest landholders
in Australia, the Australian Defence Force (ADF) is increasingly concerned with sustainable environmental management. This
paper focuses on how the ADF is maintaining effective environmental management, especially in environmentally sensitive marine
protected areas. It uses Shoalwater Bay Training Area (SWBTA) as a research example to examine environmental management strategies
conducted by the ADF. SWBTA is one of the most significant Defence training areas in Australia, with a large number of single,
joint and combined military exercises conducted in the area. With its maritime component contained in the Great Barrier Reef
Marine Park (GBRMP), the Great Barrier Reef World Heritage Area (GBRWHA), and abutting Queensland’s State Marine Parks, it
has high protection values. It is therefore vital for the ADF to adopt environmentally responsible management while they are
conducting military activities. As to various tools employed to manage environmental performance, the ISO 14001 Environmental
Management System (EMS) is widely used by the ADF. This paper examines military activities and marine environmental management
within SWBTA, using the Talisman Saber (TS) exercise series as an example. These are extensive joint exercises conducted by
the ADF and the United States defence forces. The paper outlines relevant legislative framework and environmental policies,
analyses how the EMS operates in environmental management of military activities, and how military activities comply with
these regulations. It discusses the implementation of the ADF EMS, including risk reduction measures, environmental awareness
training, consultation and communication with stakeholders. A number of environmental management actions used in the TS exercises
are presented to demonstrate the EMS application. Our investigations to this point indicate that the ADF is complying with
all relevant legislation and policies. Further research is required to confirm compliance and conclude that military activities
have good accord with environmental management objectives. 相似文献
330.