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61.
62.
Contributions of groundwater conditions to soil and water salinization 总被引:21,自引:2,他引:21
Salinization is the process whereby the concentration of dissolved salts in water and soil is increased due to natural or
human-induced processes. Water is lost through one or any combination of four main mechanisms: evaporation, evapotranspiration,
hydrolysis, and leakage between aquifers. Salinity increases from catchment divides to the valley floors and in the direction
of groundwater flow. Salinization is explained by two main chemical models developed by the authors: weathering and deposition.
These models are in agreement with the weathering and depositional geological processes that have formed soils and overburden
in the catchments. Five soil-change processes in arid and semi-arid climates are associated with waterlogging and water. In
all represented cases, groundwater is the main geological agent for transmitting, accumulating, and discharging salt. At a
small catchment scale in South and Western Australia, water is lost through evapotranspiration and hydrolysis. Saline groundwater
flows along the beds of the streams and is accumulated in paleochannels, which act as a salt repository, and finally discharges
in lakes, where most of the saline groundwater is concentrated. In the hummocky terrains of the Northern Great Plains Region,
Canada and USA, the localized recharge and discharge scenarios cause salinization to occur mainly in depressions, in conjunction
with the formation of saline soils and seepages. On a regional scale within closed basins, this process can create playas
or saline lakes. In the continental aquifers of the rift basins of Sudan, salinity increases along the groundwater flow path
and forms a saline zone at the distal end. The saline zone in each rift forms a closed ridge, which coincides with the closed
trough of the groundwater-level map. The saline body or bodies were formed by evaporation coupled with alkaline-earth carbonate
precipitation and dissolution of capillary salts.
Received, May 1998 · Revised, July 1998 · Accepted, September 1998 相似文献
63.
This study considered the rate at which striped bass larvae disintegrate following death as well as the ability of experienced taxonomists to distinguish larvae which were liver or dead on collection from preserved samples. The rate of disintegration was dependent on age (size) of the larvae with pro-larvae being unrecognizable in 8 to 16 h following death (17 to 19°C). Post-larvae decomposed somewhat more slowly, but were unrecognizable as to species after 16 h. Experienced taxonomists were unable to distinguish pro- and post-larvae which had been live or dead prior to preservation. However, the viability of metamorphosed larvae could readily be distinguished. 相似文献
64.
Leszek Marynowski Michał Zatoń Bernd R.T. Simoneit Angelika Otto Mariusz O. Jędrysek Cezary Grelowski Slawomir Kurkiewicz 《Applied Geochemistry》2007
The comprehensive biomarker characteristics from previously undescribed Middle Jurassic clays of Poland are presented. The molecular composition of the organic matter (OM) derived from clays of Aalenian to Callovian age has not changed significantly through time. High relative concentrations of many biomarkers typical for terrestrial material suggest a distinct dominance of OM derived from land plants. Increasing concentrations of C29-diaster-13(17)-enes towards the northern part of the basin indicate an increase in terrestrial input. This terrestrial material would have originated from the enhanced transport of organic matter from land situated at the northern bank of the basin, i.e., the Fennoscandian Shield. The organic matter was deposited in an oxic to suboxic environment, as indicated by relatively low concentrations of C33–C35 homohopanes, moderate to high Pr/Ph ratio values, an absence of compounds characteristic for anoxia and water column stratification, such as isorenieratane, aryl isoprenoids and gammacerane, as well as common benthic fauna and burrows. δ18O measurements from calcitic rostra of belemnites suggest that the mean value of the Middle Jurassic sea-water temperature of the Polish Basin was 13.1 °C. It is suggested that this mirrored the temperature of the lower water column because belemnites are considered here to be necto-benthic. The organic matter from the Middle Jurassic basin of Poland is immature. This is clearly indicated by a large concentration of biomarkers with the biogenic configurations, such as ββ-hopanes, hop-13(18)-enes, hop-17(21)-enes, diasterenes and sterenes. The identification of preserved, unaltered biomolecules like ferruginol, 6,7-dehydroferruginol and sugiol in Protopodocarpoxylon wood samples from these sediments present particularly strong evidence for the presence of immature OM in the Middle Jurassic sediments. Moreover, the occurrence of these polar diterpenoids is important due to the fact that they are definitely the oldest known natural products detected in geological samples. 相似文献
65.
Jan‐Christoph Otto Lothar Schrott Michel Jaboyedoff Richard Dikau 《地球表面变化过程与地形》2009,34(13):1726-1742
The determination of sediment storage is a critical parameter in sediment budget analyses. But, in many sediment budget studies the quantification of magnitude and time‐scale of sediment storage is still the weakest part and often relies on crude estimations only, especially in large drainage basins (>100 km2). We present a new approach to storage quantification in a meso‐scale alpine catchment of the Swiss Alps (Turtmann Valley, 110 km2). The quantification of depositional volumes was performed by combining geophysical surveys and geographic information system (GIS) modelling techniques. Mean thickness values of each landform type calculated from these data was used to estimate the sediment volume in the hanging valleys and the trough slopes. Sediment volume of the remaining subsystems was determined by modelling an assumed parabolic bedrock surface using digital elevation model (DEM) data. A total sediment volume of 781·3×106–1005·7×106 m3 is deposited in the Turtmann Valley. Over 60% of this volume is stored in the 13 hanging valleys. Moraine landforms contain over 60% of the deposits in the hanging valleys followed by sediment stored on slopes (20%) and rock glaciers (15%). For the first time, a detailed quantification of different storage types was achieved in a catchment of this size. Sediment volumes have been used to calculate mean denudation rates for the different processes ranging from 0·1 to 2·6 mm/a based on a time span of 10 ka. As the quantification approach includes a number of assumptions and various sources of error the values given represent the order of magnitude of sediment storage that has to be expected in a catchment of this size. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
66.
The Austrian blackfly fauna were analysed with regard to spatial (ecoregions, bioregions), vertical (altitude classes) and longitudinal zonation characteristics [stream order, biocoenotic (= fish) regions] on the basis of 2600 investigation sites. Of a total of 45 species recorded, Simulium ornatum, S. variegatum, S. argyreatum and S. reptans are the most common and most frequently distributed species, occurring in 60% of the investigated sites. Although the Austrian blackfly fauna seem to be quite well documented (on average one investigation site per 32 km2) the jackknife analyses indicates that there are still some fauna deficits. Whereas the species diversity of the main ecoregions is quite similar, the number of species differs clearly between the bioregions. Within the typological context of the Water Framework Directive, the Austrian Simuliidae confirm the bioregions as the most useful spatial units for river typology. A further optimisation in predicting a target list of blackfly species of a site can be achieved by subdividing the bioregions into either catchment area and altitude classes or into longitudinal zonation types (biocoenotic regions). 相似文献
67.
Otto Pratje 《International Journal of Earth Sciences》1934,25(3):145-160
Zusammenfassung Fassen wir zum Schluß die Ergebnisse unserer Betrachtungen zusammen, die im einzelnen keine Vollständigkeit erstrebt haben, sondern nur die Möglichkeiten aufzeigen wollten, wie die sedimentbeeinflussenden Strömungen verändert und wie ihre Wirkungen überdeckt werden können. Sie sind starken Beeinflussungen durch Hindernisse unterworfen, so daß sie sich örtlich ändern können und damit auch einen Wechsel in den Sedimenten bedingen. Die Beziehungen zwischen Strömung und Sediment können erst dann erwartet werden, wenn die Zeit der Wechselwirkung ausgereicht hat, um das Gleichgewicht herzustellen. Eine weitere Voraussetzung ist das Material, das durch seine Korngrößen in der Lage sein muß, die Strömungsgeschwindigkeiten eindeutig abzubilden. Das bezieht sich sowohl auf das zurückbleibende Sediment wie auf die bewegten Sinkstoffe. Abweichungen von der normalen Transportkraft der Strömungen werden durch das Relief in auf- und absteigenden Strömen und durch die Wassereigenschaften in verschieden dichten Wasserarten gefunden. Weitere, mehr willkürliche Verfälschungen gehen von den Organismen aus.Verschleierungen durch andere Einflüsse sind also bei den Beziehungen zwischen Strömung und Sediment möglich, dennoch sind die Beziehungen überall vorhanden, und die Strömungen sind, allgemein gesprochen, der stärkste Faktor bei der Gestaltung der Ablagerungen.24. Beitrag: Annalen der Hydrographie usw., 1934. 相似文献
68.
Roland Otto 《Hydrogeology Journal》2001,9(5):498-511
In the southeastern Holstein region, located to the east of the metropolitan zone of Hamburg, northern Germany, a groundwater
investigation program was conducted from 1984 to 2000 by the State Agency for Nature and Environment (Landesamt für Natur
und Umwelt, LANU) of Schleswig-Holstein, Germany, with the aim of providing long-term, ecologically acceptable groundwater
management plans for the region. The focal point of the investigation comprised the determination of groundwater recharge
rates. The investigation method was based on the transfer of available lysimeter results from other regions to comparable
regions within the area studied. With the help of lysimeter equations, potential amounts of percolation water were calculated.
The groundwater recharge rate was then determined after subtraction of the surface runoff which was calculated for the entire
area. All computations were performed with a spreadsheet program. Groundwater recharge rates were calculated for two areas.
One consisted of roughly determining groundwater recharge rates for the total region (1,392 km2) of southeastern Holstein. The overall goal of these investigations was to identify potential areas of water exploitation.
Areas in which groundwater recharge rates are high and groundwater outflow is low are particularly suited to water exploitation,
since inflow rates into deeper aquifers are high. These areas are located on the flanks of the Elbe and Stecknitz River valleys.
Subsurface groundwater runoff to these lowlands would be reduced through groundwater withdrawal. However, the resulting decline
in shallow groundwater tables would be so small that it would have no detrimental ecological effects. Groundwater recharge
rates were also calculated for a 110-km2 area in the outskirts of Hamburg (Grosshansdorf model area) which is intensively developed for water supply. These investigations
showed that the amount of groundwater recharge is already being withdrawn to a large extent. Approximately 65% of the recharge
rate is currently withdrawn by the waterworks in this area, thus making further increases in exploitation rates unjustifiable
from an ecological point of view.
Electronic Publication 相似文献
69.
70.