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121.
Résumé Nous avons étendu aux températures négatives les mesures de l'humidité relative critiqueh
c
juste suffisante pour permettre la condensation de vapeur d'eau sur des noyaux géants constitués par divers sels.Pour chaque sel étudié, un point de la courbe donnanth
c
en fonction de la températuret° C est facilement obtenu en recherchant pour quelle valeurt
c
de la températureh
c
coïncide avec l'humidité relative en équilibre avec la glace à la même températuret
c
.Les valeurs obtenues pour NaCl, NH4Cl, KCl, KNO3 tendent à valider l'extrapolation des valeurs déjà connues pour les températures positives.
Summary We have enlarged to negative temperatures the measures of critical relative humidityh c just sufficient to allow the condensation of water vapour on giant nuclei constituted by different salts.For every salt studied, a point of the curve givingh c as a function of the temperaturet° C is easily obtained by measuring for what valuet c of the temperature,h c coincides with the relative humidity in equilibrium with ice at the same temperaturet c .The values obtained for NaCl, NH4Cl, KCl, KNO3 tend to validate the extrapolation of the values known for positive temperatures.相似文献
122.
C. Hans Nelson Andres Maldonado Francis Coumes Henri Got Andre Manaco 《Geo-Marine Letters》1983,3(2-4):125-131
The Ebro Fan System consists of en echelon channel-levee complexes, 50×20 km in area and 200-m thick. A few strong reflectors in a generally transparent seismic facies identify the sand-rich channel floors and levee crests. Numerous continuous acoustic reflectors characterize overbank turbidites and hemipelagites that blanket abandoned channel-levee complexes. The interlobe areas between channel complexes fill with homogeneous mud and sand from mass flow and overbank deposition; these exhibit a transparent seismic character. The steep continental rise and sediment “drainage” of Valencia Trough at the end of the channel-levee complexes prevent the development of distributary channels and midfan lobe deposits. 相似文献
123.
Gilbert Mille Yan Yu Chen Gérard Giusti Henri Dou Evelyne Vacelet Marie-Reine Plante-Cuny 《Marine environmental research》1984,11(3):213-232
The evolution of hydrocarbons in sediments was studied from 1978 to 1980 at eight stations in the Ile Grande marshes (Brittany) polluted by the Amoco Cadiz oil spill. Generally, in 1980 (except for one heavily polluted site) the amounts of hydrocarbons were found to be far less important than in 1978 and sometimes biogenic hydrocarbons were found. In the superficial layer of the sediments biodegradation processes were generally important with the preferential degradation of n-alkanes. On the other hand, aromatic hydrocarbons seem not to have been altered after three years. Degradation of percolated hydrocarbons proceeds more slowly than in the surface layer. The number of degrading bacteria decreases when n-alkanes disappear. 相似文献
124.
Mounir Karim Mehdi Maanan Mohamed Maanan Hassan Rhinane Henri Rueff Lahssen Baidder 《国际泥沙研究》2019,34(1):65-72
Coastal lagoons have significant biodiversity and ecologic and socio-economic interest. Several resident and migratory birds live in coastal lagoons as well as fish and other aquatic biota. Over the years, lagoons worldwide have been subject to considerable sediment deposition coming especially from soil erosion due of agricultural activities, and the lagoon's inflows have resulted in an accelerated sedimentation which can drastically affect the aquatic ecosystem balance. A new, fast, and cost-effective approach was developed, using water surface change as a proxy, to evaluate the sediment deposition rate. In the current research, this methodology was applied in the Moulay Bousselham Lagoon in Morocco, and a combination of Landsat 8 and Landsat 5 imagery acquired at four points in time over 30 years(1985-2015) was used. Following geometric correction and enhancement, the interpretation of the acquired images provided important insight on the current conditions of the water surface change using the Normalized Difference Water Index(NDWI). Several iterations were done to determine a suitable threshold for effective water surface detection. In order to validate the automatically extracted water surface features, many band combinations of Landsat and Sentinel 2 were used as references to run the accuracy assessment. The results show that the Moulay Bousselham Lagoon lost 17.60%(106 ha) of its water surface area, and 530,000 m^3 to 1,060,000 m^3 of its water volume during the last three decades.Converting water surface loss into sedimentation returned a rate of 0.58 cm/yr. These results have been confirmed by previous field work using sedimentological approaches. Proper management should be applied to sustain the vitality of this lagoon environment. 相似文献
125.
Due to mechanisms such as impact heating, early atmospheric thermal blanketing, and radioactive heating, the presence of at least one global magma ocean stage in the early histories of terrestrial planets seems unavoidable. In such a context, a key question to constrain the early thermo–chemical evolution of the Earth is how much iron diapirs provided by differentiated impactors emulsified during their sinking towards the bottom of an early magma ocean.In the past years, several workers have focused on this question, using however various approaches and making different assumptions. While most studies favor rapid breakup and equilibration of iron bodies during their sinking through the magma ocean, recent work suggests that iron bodies of size comparable or greater than a few tens of kilometers may preserve most of their initial volume as they reach the bottom of a magma ocean, therefore leading to metal–silicate disequilibrium.To clarify the discrepancies and the differences among studies I have conducted a series of numerical simulations and theoretical calculations to derive the conditions and the timing for the breakup of metal diapirs of any size, sinking through a silicate magma ocean, with a large range of plausible viscosity values. The obtained breakup criterion is used to derive stable diapir sizes and their ability to equilibrate with the surrounding silicates. I show that for plausible magma ocean viscosities, diapirs with initial radii smaller than the thickness of a magma ocean rapidly break up into stable diapir sizes smaller than 0.2 m, at which metal–silicate equilibration is rapidly achieved. 相似文献
126.
Concentrations of copper, zinc, chromium, lead, cadmium, and phosphorus were obtained from 81 samples of unconsolidated estuarine
sediment from Great Bay, New Hampshire. Dispersal of aqueous chromium from localized industrial effluent is believed responsible
for an increase in sediment chromium throughout the entire estuary. High phosphorus concentrations exist in sediment near
the outfalls from several waste-water treatment plants. There is no evidence for any increase of copper, zinc, lead, or cadmium
in this estuary, except for localized high concentrations close to industrial outfalls.
Fine-grained sediments and organic carbon correlate highly with all the elements studied, except for chromium. This suggests
that conventional agents of sedimentary adsorption are not adequate to explain the incorporation of chromium into sediment
under the conditions of heavy industrial discharge which exist in this estuary. Sediment phosphorus correlates highly with
minor elements, suggesting that it is an adsorption agent, similar to more typical sedimentary parameters such as organic
matter and clay minerals. In such a capacity phosphorus may enhance the sedimentary uptake of other aqueous species, and account
for higher chromium sediment concentrations. Comparative data from other sedimentary environments emphasize the environmental
significance of these elements in Great Bay. 相似文献
127.
Laurie Boithias Yves Auda Stéphane Audry Jean-Pierre Bricquet Alounsavath Chanhphengxay Vincent Chaplot Anneke de Rouw Thierry Henry des Tureaux Sylvain Huon Jean-Louis Janeau Keooudone Latsachack Yann Le Troquer Guillaume Lestrelin Jean-Luc Maeght Pierre Marchand Pierre Moreau Andrew Noble Anne Pando-Bahuon Kongkeo Phachomphon Khambai Phanthavong Alain Pierret Olivier Ribolzi Jean Riotte Henri Robain Emma Rochelle-Newall Saysongkham Sayavong Oloth Sengtaheuanghoung Norbert Silvera Nivong Sipaseuth Bounsamay Soulileuth Xaysatith Souliyavongsa Phapvilay Sounyaphong Sengkeo Tasaketh Chanthamousone Thammahacksa Jean-Pierre Thiebaux Christian Valentin Olga Vigiak Marion Viguier Khampaseuth Xayyathip 《水文研究》2021,35(5):e14126
Mountain regions of the humid tropics are characterized by steep slopes and heavy rains. These regions are thus prone to both high surface runoff and soil erosion. In Southeast Asia, uplands are also subject to rapid land-use change, predominantly as a result of increased population pressure and market forces. Since 1998, the Houay Pano site, located in northern Lao PDR (19.85°N 102.17°E) within the Mekong basin, aims at assessing the long-term impact of the conversion of traditional slash-and-burn cultivation systems to commercial perennial monocultures such as teak tree plantations, on the catchment hydrological response and sediment yield. The instrumented site monitors hydro-meteorological and soil loss parameters at both microplot (1 m2) and small catchment (0.6 km2) scales. The monitored catchment is part of the network of critical zone observatories named Multiscale TROPIcal CatchmentS (M-TROPICS). The data shared by M-TROPICS in Houay Pano are (1) rainfall, (2) air temperature, air relative humidity, wind speed, and global radiation, (3) catchment land use, (4) stream water level, suspended particulate matter, bed particulate matter and stones, (5) soil surface features, and (6) soil surface runoff and soil detachment. The dataset has already been used to interpret suspended particulate matter and bed particulate matter sources and dynamics, to assess the impact of land-use change on catchment hydrology, soil erosion, and sediment yields, to understand bacteria fate and weed seed transport across the catchment, and to build catchment-scale models focused on hydrology and water quality issues. The dataset may be further used to, for example, assess the role of headwater catchments in large tropical river basin hydrology, support the interpretation of new variables measured in the catchment (e.g., contaminants other than faecal bacteria), and assess the relative impacts of both climate and land-use change on the catchment. 相似文献
128.
Michel Ritz Henri Robain Evgeni Pervago Yves Albouy Christian Camerlynck Marc Descloitres Adama Mariko 《Geophysical Prospecting》1999,47(2):85-101
Near-surface inhomogeneities (NSIs) can lead to severe problems in the interpretation of apparent resistivity pseudosections because their effects significantly complicate the image aspect. In order to carry out a more efficient and reliable interpretation process, these problematic features should be removed from field data. We describe a filtering scheme using two-sided half-Schlumberger array data. The scheme was tested on synthetic data, generated from a simple 2D resistivity model contaminated by NSIs, and is shown to be suitable for eliminating such contaminations from apparent resistivity data. Furthermore, the original model without NSIs can be recovered satisfactorily from the inversion of filtered apparent resistivity data. The algorithm is also applied efficiently to a real data set collected at Nsimi, in southern Cameroon, along a 200-m shallow depth profile crossing a complex transitional zone. For this case, the filtering scheme provides accurate structural and behavioural interpretations of both the geometry of the major soil constituents and the groundwater partitioning. 相似文献
129.
The Cap Creus and Lacaze-Duthiers canyons, cut on the narrow subsiding margin off the eastern Pyrenees, play an important role in downslope sediment transport in the northwestern Mediterranean. This conclusion is based on an evaluation of the surficial sediment distribution patterns, cores, direct visual observations of the sea floor made in 24 submersible dives and tight-grid seismic survey data. Down-canyon sediment movement (mostly by slump and gravity flow mechanisms) since the end of the Pliocene has resulted in the formation of the Catalonia Fan at the base of the slope west of the Rhone Cone. 相似文献
130.