全文获取类型
收费全文 | 204篇 |
免费 | 6篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 15篇 |
地球物理 | 57篇 |
地质学 | 83篇 |
海洋学 | 35篇 |
天文学 | 9篇 |
综合类 | 1篇 |
自然地理 | 6篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 5篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2017年 | 7篇 |
2016年 | 6篇 |
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 8篇 |
2012年 | 8篇 |
2011年 | 26篇 |
2010年 | 12篇 |
2009年 | 27篇 |
2008年 | 13篇 |
2007年 | 6篇 |
2006年 | 10篇 |
2005年 | 6篇 |
2004年 | 13篇 |
2003年 | 10篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有210条查询结果,搜索用时 31 毫秒
181.
Stefania Bilardi Paolo S. Calabrò Sabine Caré Nicola Moraci Chicgoua Noubactep 《洁净——土壤、空气、水》2013,41(9):835-843
Current knowledge of the basic principles underlying the design of Fe0 beds is weak. The volumetric expansive nature of iron corrosion was identified as the major factor determining the sustainability of Fe0 beds. This work attempts to systematically verify developed concepts. Pumice and sand were admixed to 200 g of Fe0 in column studies (50:50 volumetric proportion). Reference systems containing 100% of each material have been also investigated. The mean grain size of the used materials (in mm) were 0.28 (sand), 0.30 (pumice), and 0.50 (Fe0). The five studied systems were characterized (i) by the time dependent evolution of their hydraulic conductivity (permeability) and (ii) for their efficiency for aqueous removal of CuII, NiII, and ZnII (about 0.3 mM of each). Results showed unequivocally that (i) quantitative contaminant removal was coupled to the presence of Fe0, (ii) additive admixture lengthened the service life of Fe0 beds, and (iii) pumice was the best admixing agent for sustaining permeability while the Fe0/sand column was the most efficient for contaminant removal. The evolution of the permeability was well‐fitted by the approach that the inflowing solution contained dissolved O2. The achieved results are regarded as starting point for a systematic research to optimize/support Fe0 filter design. 相似文献
182.
The CNES/ISRO mission SARAL/AltiKa was successfully launched on 25 February 2013. It reached its nominal orbit on 13 March 2013. AltiKa is the first altimeter using the Ka-band frequency. This article presents the results of the calibration and validation activities perfromed on the first year of the SARAL/AltiKa mission. The main objective of the article is to assess the SARAL/AltiKa data quality and to estimate the altimeter system performance using GDR products. To achieve this goal, we present mono-mission metrics and compare them with Jason-2 over the same period. Even if these missions do not have the same ground track, precise comparisons are still possible. They allow assessing parameter discrepancies and SSH consistency between both missions in order to detect geographically correlated biases, jumps or drifts. These results show that SARAL/AltiKa data quality is excellent: ocean data coverage is greater than 99.5%, standard deviation at cross-overs is 5.4 cm. The mission therefore fulfills the requirements of high precision altimetry and can be used (in conjunction with Jason-2) to monitor the global mean sea level, ensuring the continuity of the record over ERS/Envisat historical ground track. Possible improvements and open issues are also identified, foreseeing an even better mission performance. 相似文献
183.
Sebastian Müller Carsten Leven Peter Dietrich Sabine Attinger Alraune Zech 《Ground water》2022,60(1):137-144
We present a workflow to estimate geostatistical aquifer parameters from pumping test data using the Python package welltestpy . The procedure of pumping test analysis is exemplified for two data sets from the Horkheimer Insel site and from the Lauswiesen site, Germany. The analysis is based on a semi-analytical drawdown solution from the upscaling approach Radial Coarse Graining, which enables to infer log-transmissivity variance and horizontal correlation length, beside mean transmissivity, and storativity, from pumping test data. We estimate these parameters of aquifer heterogeneity from type-curve analysis and determine their sensitivity. This procedure, implemented in welltestpy , is a template for analyzing any pumping test. It goes beyond the possibilities of standard methods, for example, based on Theis' equation, which are limited to mean transmissivity and storativity. A sensitivity study showed the impact of observation well positions on the parameter estimation quality. The insights of this study help to optimize future test setups for geostatistical aquifer analysis and provides guidance for investigating pumping tests with regard to aquifer statistics using the open-source software package welltestpy . 相似文献
184.
Sabine Schmidt Hélène Howa Aurelia Mouret Fabien Lombard Pierre Anschutz Laurent Labeyrie 《Continental Shelf Research》2009,29(8):1044-1052
As a part of the ANR-Forclim experiment, particle mass fluxes and sedimentation processes were investigated on the slope of Aquitanian margin of the Bay of Biscay, between the canyons of Cap-Breton and Cap-Ferret. Interface sediments were collected along a depth transect from 145 to 2000 m; simultaneously a mooring line was deployed at the deepest station (WH, 2000 m) with two traps (800 and 1700 m) for a 16-month period (June 2006–November 2007). 210Pb activities of settling particles and of interface sediments were determined to study transport processes of particles. Sediment and mass accumulation rates, calculated from excess 210Pb profiles in the sediment column, show the expected decreasing trend with depth, as usually observed on margins. Mean particulate mass fluxes at 800 and 1700-m depth at site WH are, respectively, 27 and 70 g m?2 a?1.The 210Pb budget points out events of temporary high lateral input of particles. The comparison of mass and 210Pb fluxes between the water column and the seabed indicates that lateral transport plays an important role in particle accumulation on the Aquitanian margin. Regarding the objectives of the ANR-Forclim program, which aims to improve significantly the interpretation of fossil foraminifera signals, as a proxy for hydrological changes in the North Atlantic ocean, these results highlight advection processes must be considered when interpreting fluxes of foraminifers on the Aquitanian margin. 相似文献
185.
Ulrich C. Müller Jörg Pross Polychronis C. Tzedakis Clive Gamble Ulrich Kotthoff Gerhard Schmiedl Sabine Wulf Kimon Christanis 《Quaternary Science Reviews》2011,30(3-4):273-279
The spread of anatomically modern humans (AMH) into Europe occurred when shifts in the North Atlantic meridional overturning circulation triggered a series of large and abrupt climate changes during the last glacial. However, the role of climate forcing in this process has remained unclear. Here we present a last glacial record that provides insight into climate-related environmental shifts in the eastern Mediterranean region, i.e. the gateway for the colonisation of Europe by AMH. We show that the environmental impact of the Heinrich Event H5 climatic deterioration c. 48 kyr ago was as extreme as that of the glacial maximum of Marine Isotope Stage (MIS) 4 when most of Europe was deserted by Neanderthals. We argue that Heinrich H5 resulted in a similar demographic vacuum so that invasive AMH populations had the opportunity to spread into Europe and occupy large parts before the Neanderthals were able to reoccupy this territory. This spread followed the resumption of the Atlantic meridional overturning circulation at the beginning of Greenland Interstadial (GIS) 12 c. 47 kyr ago that triggered an extreme and rapid shift from desert-steppe to open woodland biomes in the gateway to Europe. We conclude that the extreme environmental impact of Heinrich H5 within a situation of competitive exclusion between two closely related hominids species shifted the balance in favour of modern humans. 相似文献
186.
Does ratification matter and do major conventions improve safety and decrease pollution in shipping?
This article develops a method to measure the effect of the major international conventions in the area of safety, pollution, search and rescue and work related measures. It further distinguishes between the effect of entry into force and the status of ratification of a convention by its parties. Standard econometric models are used and the analysis is based on a unique dataset of 30 years of monthly data where the models also correct for other factors which can influence safety such as safety inspections and ship economic cycles. The results show a complex picture where the average time between adoption and entry into force was calculated to be 3.1 years. Overall, the more parties ratify a convention, the more likely safety is improved and pollution is decreased although one can detect a certain level of non-compliance. The immediate effect of entry into force presents a mixed picture where most negative effects can be found with legislation in the area of safety management and pollution, followed by technical areas. The effect of legislation in the areas related to working and living conditions and certification and training is smallest. Seasonality can be found with peaks in December and January for all conventions but are less important for pollution. 相似文献
187.
Aymeric Dabrin Jrg Schfer Grard Blanc Emilie Strady Matthieu Masson Ccile Bossy Sabine Castelle Naïg Girardot Alexandra Coynel 《Estuarine, Coastal and Shelf Science》2009,84(4):429-439
Dissolved Cd (CdD) concentrations along the salinity gradient were measured in surface water of the Gironde Estuary during 15 cruises (2001–2007), covering a wide range of contrasting situations in terms of hydrology, turbidity and season. During all situations dissolved Cd concentrations displayed maximum values in the mid-salinity range, reflecting Cd addition by chloride-induced desorption and complexation. The daily net CdD fluxes from the Gironde Estuary to the coastal ocean were estimated using Boyle's method. Extrapolating CdD concentrations in the high salinity range to the freshwater end member using a theoretical dilution line produced 15 theoretical Cd concentrations (CdD0), each representative of one distinct situation. The obtained CdD0 concentrations were relatively similar (201 ± 28 ng L−1) when freshwater discharge Q was >500 m3 s−1 (508 ≤ Q ≤ 2600 m3 s−1), but were highly variable (340 ± 80 ng L−1; 247–490 ng L−1) for low discharge situations (169 ≤ Q ≤ 368 m3 s−1). The respective daily CdD net fluxes were 5–39 kg day−1, mainly depending on freshwater discharge. As this observation invalidates the existing method of estimating annual CdD net fluxes, we proposed an empirical model, using representative CdD0 values and daily freshwater discharges for the 2001–2007 period. Subsequent integration produced reliable CdD net flux estimates for the Gironde Estuary at the annual timescale that ranged between 3.8–5.0 t a−1 in 2005 and 6.0–7.2 t a−1 in 2004, depending on freshwater discharge. Comparing CdD net fluxes with the incoming CdD fluxes suggested that the annual net CdD addition in the Gironde Estuary ranged from 3.5 to 6.7 t a−1, without any clear temporal trend during the past seven years. The annual CdD net fluxes did not show a clearly decreasing trend in spite of an overall decrease by a factor 6 in Cd gross fluxes during the past decade. Furthermore, in six years out of seven (except 2003), the annual CdD net fluxes even exceeded river borne total (dissolved + particulate) gross Cd fluxes into the estuary. These observations were attributed to progressive Cd desorption from both suspended particles and bottom sediment during various sedimentation–resuspension cycles induced by tidal currents and/or continuous dredging (navigation channel) and diverse intra-estuarine sources (wet deposition, urban sources, and agriculture). Provided that gross fluxes remain stable over time, dissolved Cd exportation from the Gironde Estuary to the coastal ocean may remain at the present level for the coming decade and the estuarine sedimentary Cd stock is forecast to decrease slowly. 相似文献
188.
Aurélia Mouret Pierre Anschutz Pascal Lecroart Gwénaëlle Chaillou Christelle Hyacinthe Jonathan Deborde Frans J. Jorissen Bruno Deflandre Sabine Schmidt Jean-Marie Jouanneau 《Geo-Marine Letters》2009,29(3):133-149
Manganese is a major redox reactive element of benthic metabolism. We have built a database of existing knowledge on the benthic
geochemistry of Mn in the Bay of Biscay, in order to comprehensively assess the behaviour of Mn in a variety of environments
during early diagenesis. The database contains vertical profiles of particulate and dissolved Mn species of 59 cores collected
during 17 cruises between 1997 and 2006 at nine stations positioned between 140 and 4,800 m water depths. At all studied stations,
Mn species follow the conventional distribution, where Mn(III,IV) species are enriched in the oxic layer, and dissolved Mn
is present in the anoxic sediments. A minor part of Mn-oxides originates from sedimenting particles. The major part is of
diagenetic origin, and derives from the oxidation of upward-diffusing dissolved Mn(II). Mn-oxide inventories are higher at
the deeper stations than at the shallower ones. This difference cannot be attributed to different sources of sedimenting particles,
but it must depend on sedimentation rate and diagenetic processes. At depth, dissolved Mn(II) concentrations are constant.
This probably reflects equilibrium with an authigenic Mn(II) phase, which is the ultimate phase into which Mn is fossilized.
The Mn content of deeper anoxic sediments is similarly low in all the cores studied, associated with corresponding trends
of Mn content in sedimenting particles of the Bay of Biscay. Bioturbation, rather than redox oscillations, can convey Mn(III,IV)
species downwards into the anoxic sediments where they are reduced, associated with a peak of dissolved Mn. Because dissolved
Mn(II) is re-oxidized when it diffuses towards the oxic layer, the inventory of the diagenetic Mn(III,IV) phase remains at
steady state, especially at stations where the oxic layer is thick. It then becomes possible to calculate the residence time
of diagenetic Mn(III,IV) particles within the oxic layer, using the upward-directed flux of pore water Mn(II). By applying
this residence time to the accumulation of sediments within the oxic layer, we obtain the sediment mass accumulation rate.
The values calculated for the sediments of the Bay of Biscay fit well with accumulation rates obtained from radionuclides
or sediment traps. The method has also been validated with data collected in other marine sedimentary environments.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
189.
以德拜特性温度为可调参量,用德拜理论近似分析了某些链状硅酸盐矿物在不同温度、压力下的^57Fe中心移数据。二级多普勒移δSOD用德拜理论估计,并由δCS的实验值与δSOD的估计值之差获得同质异能移δIS。结果表明,对中心移的主要贡献来自同质异能移,在室温下,二级多勒移仅为中心移的16%,室温下δSOD的压力系数比δIS的小一个数量级以上,故压力改变时δCS的变化主要是δIS的变化引起的。反之,在常 相似文献
190.
Steven Emerson Yutaka W. Watanabe Tsuneo Ono Sabine Mecking 《Journal of Oceanography》2004,60(1):139-147
We present a compilation of apparent oxygen utilization (AOU) changes observed in the upper pycnocline of the North Pacific
Ocean over the last several decades. The goal here is to place previously-published data in a common format, and assess the
causes of the observed changes. The general trend along repeat cross sections of the eastern and western subtropical ocean
and the subarctic ocean is an increase in AOU from the mid 1980s to the mid 1990s. AOU has also been increasing in a time-series
study in the northwest subarctic Ocean off of Japan since the late 1960s. Observed AOU changes south of 35°N in the subtropical
ocean are 10–20 μmol kg−1, with much greater changes, reaching 60–80 μmol kg−1 in isolated areas, in the subtropical/subarctic boundary and the subarctic ocean. Analysis of changes in both AOU and salinity
on isopycnals suggests that there are significant salinity-normalized increases that must be due to alteration in the rate
of ventilation or organic matter degradation. A common feature in the data is that the maximum increase in AOU is centered
near the density horizon σθ= 26.6. Time series results from the Oyashio Current region near the winter outcrop area of this density horizon indicate
that surface waters there have become fresher with time, which may mean this density surface has ceased to outcrop in the
latter decades of the 20th century. Whether this is due to natural decadal-scale changes or anthropogenic influences can be
decided by determining future trends in AOU on these density surfaces.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献