全文获取类型
收费全文 | 119篇 |
免费 | 2篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 17篇 |
地球物理 | 21篇 |
地质学 | 49篇 |
海洋学 | 12篇 |
天文学 | 10篇 |
综合类 | 1篇 |
自然地理 | 9篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 4篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 13篇 |
2016年 | 2篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 8篇 |
2012年 | 6篇 |
2011年 | 4篇 |
2010年 | 10篇 |
2009年 | 9篇 |
2008年 | 2篇 |
2007年 | 5篇 |
2006年 | 4篇 |
2005年 | 9篇 |
2004年 | 6篇 |
2003年 | 4篇 |
2002年 | 1篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1998年 | 2篇 |
1996年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1975年 | 2篇 |
1968年 | 1篇 |
排序方式: 共有121条查询结果,搜索用时 406 毫秒
111.
Johannes Schmidt Lukas Werther Johannes Rabiger-Völlmer Franz Herzig Birgit Schneider Ulrike Werban Peter Dietrich Stefanie Berg Sven Linzen Peter Ettel Christoph Zielhofer 《地球表面变化过程与地形》2020,45(14):3449-3462
Sediment budgeting concepts serve as quantification tools to decipher the erosion and accumulation processes within a catchment and help to understand these relocation processes through time. While sediment budgets are widely used in geomorphological catchment-based studies, such quantification approaches are rarely applied in geoarchaeological studies. The case of Charlemagne's summit canal (also known as Fossa Carolina) and its erosional collapse provides an example for which we can use this geomorphological concept and understand the abandonment of the Carolingian construction site. The Fossa Carolina is one of the largest hydro-engineering projects in Medieval Europe. It is situated in Southern Franconia (48.9876°N, 10.9267°E; Bavaria, southern Germany) between the Altmühl and Swabian Rezat rivers. It should have bridged the Central European watershed and connected the Rhine–Main and Danube river systems. According to our dendrochronological analyses and historical sources, the excavation and construction of the Carolingian canal took place in AD 792 and 793. Contemporary written sources describe an intense backfill of excavated sediment in autumn AD 793. This short-term erosion event has been proposed as the principal reason for the collapse and abandonment of the hydro-engineering project. We use subsurface data (drillings, archaeological excavations, and direct-push sensing) and geospatial data (a LiDAR digital terrain model (DTM), a pre-modern DTM, and a 3D model of the Fossa Carolina] for the identification and sediment budgeting of the backfills. Dendrochronological findings and radiocarbon ages of macro remains within the backfills give clear evidence for the erosional collapse of the canal project during or directly after the construction period. Moreover, our quantification approach allows the detection of the major sedimentary collapse zone. The exceedance of the manpower tipping point may have caused the abandonment of the entire construction site. The spatial distribution of the dendrochronological results indicates a north–south direction of the early medieval construction progress. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd 相似文献
112.
Endoparasites in common eiders Somateria mollissima from birds killed by an oil spill in the northern Wadden Sea 总被引:1,自引:0,他引:1
Mass mortalities of common eiders Somateria mollissima have been ascribed to high parasite loads. However, the actual role of parasites in mortalities is disputed as in the case of a mass mortality of eiders in the Wadden Sea in the winter of 1999/2000. A critical evaluation of the role of parasites in eider mass mortalities is hampered by (1) a lack of data on actual parasite loads of the birds involved, (2) missing regional data for comparison, and (3) a lack of unbiased samples: investigations are often based on dead beached individuals, which are presumably the more heavily infected birds of a population and thus more likely to die and be washed ashore. Although published data on parasite loads in birds of the winter 1999/2000 mortality are available, no data on background parasitism in eiders from the Wadden Sea exist, making an evaluation of the potential role of parasites in this mortality event difficult. By investigating endoparasites of 102 eiders affected by an oil spill in the northern Wadden Sea in winter 1998/1999, we provide a data set of background parasitism in wintering eiders from the Wadden Sea. We found 13 different parasite taxa with high prevalence values (% infected birds) in the acanthocephalan Profilicollis botulus, the nematode Amidostomum acutum, cestodes and trematodes. In some taxa we observed pronounced differences in prevalence values between juvenile eiders and adults, as well as between adult sexes. The parasite composition shows that bivalves, crabs (Carcinus maenas) and other crustaceans are important sources of infections by being intermediate hosts. This is partly mirrored in the food content of eider stomachs where bivalves and crabs were predominantly found. Intensities of the acanthocephalan P. botulus, suspected of causing eider mortalities, were especially high in juveniles (1112 ± 416 ind per infected host), but lower in adult males (40 ± 7) and adult females (81 ± 18). However, no extraordinary mortality event was observed in the winter of 1998/1999, indicating no or a very weak effect of the parasites on host condition. A comparison with the parasite loads of eiders from the mass mortality in the winter of 1999/2000 shows that parasite numbers were by no means exceptional for birds from the area. Hence, parasites alone are unlikely to have caused this mortality. Regional background parasite loads are important to differentiate between primary and secondary roles of parasites in anomalous mortality events. 相似文献
113.
Sebastian Zuehlke Uwe Duennbier Thomas Heberer Birgit Fritz 《Ground Water Monitoring & Remediation》2004,24(2):78-85
A reliable and sensitive analytical method for the determination of estrone (E1), 17β-estradiol (E2), and the synthetic hormone 17α-ethinylestradiol (EE2) has been established. Samples are concentrated using automated solid-phase extraction and analysis is performed by liquid chromatography with detection by tandem mass spectrometry. Recoveries of all analytes were between 93% and 107%, and limits of quantification (LOQs) between 0.1 and 0.4 ng/L for purified sewage, and surface, ground, and drinking water, and between 1 and 2 ng/L in case of raw sewage. For the investigation of estrogen release into the environment and its behavior during sewage and surface water treatment, and during ground water recharge, samples from municipal waste water treatment plants (WWTPs), a surface water treatment plant, a bank filtration site, and a ground water enrichment (GWE) pond were analyzed. El was found in the raw waste water with an average concentration of 157 ng/L, whereas E2 and EE2 were found with mean concentrations of only 18 and 9 ng/L, respectively. Sewage treatment by municipal WWTPs affected a removal of EE2 (76%), El (92%), and E2 (94%). In the investigated surface water of Berlin, only E1 could be detected at concentrations around or below 1 ng/L. E2 and EE2 were not present in the Berlin surface water above the LOQ of 0.2 ng/L, respectively. Surface water treatment also leads to a significant removal of E1 (> 80%). In the ground water samples from the GWE site near Lake Tegel, only a few samples contained detectable concentrations of E1. These samples were collected from a shallow monitoring well located very close to the bank of the pond. Even a short distance between the bank and observation wells led to concentrations of El below the LOQ showing the potential of ground water recharge systems for the retention of estrogenic steroids depending on the environmental setting. 相似文献
114.
Dr. Jürgen Hagedorn 《International Journal of Earth Sciences》1968,58(2):439-446
Zusammenfassung Es wird vorgeschlagen, als Hauptgliederungsprinzip in kleinmaßstäblichen geomorphologischen Karten die genetische Gliederung nach exogenen Formungsprozessen zu benutzen. Dabei sind für die Morphogenese eines einheitlichen Gebietes im allgemeinen die Wirkungen mehrerer Formungsphasen zu berücksichtigen, für jede Formungsphase die Wirkungen mehrerer Formungsprozesse. Jedes morphogenetisch gleichartige Gebiet läßt sich durch eine Formel beschreiben, in der jede Formungsphase durch die Aneinanderreihung von Kennbuchstaben für die wirksamen Prozesse, die Abfolge der Formungsphasen durch ihre Anordnung zu einer Spalte gezeichnet wird.
Erweiterte Fassung eines Vortrages auf der 58. Jahrestagung der Geologischen Vereinigung, Göttingen 1968. - Die Ausführungen gehen zurück auf Arbeiten an einem geomorphologischen Atlas, die seit längerer Zeit am Geographischen Institut der Universität Göttingen unter der Gesamtleitung von Prof. Dr. H.Poser durchgeführt werden. Herrn Prof.Poser und meinen Kollegen und Mitarbeitern möchte ich für alle die Anregungen, die sich in diesem Aufsatz niedergeschlagen haben, ohne daß sie im einzelnen zitiert werden können, herzlich danken. 相似文献
The author proposes a new classificatory principle for geomorphological maps of a small scale: it is the application of a genetic classification derived from exogenous processes. In general the effects of several morphogenetic periods must be considered for the morphological evolution of a homogenous region, as well as the effects of several morphodynamic processes during each morphogenetic period. Each morphogenetically similar region can be specified by a formula in which each morphodynamic period is characterized by a set of indicating letters, each representing a single effective process; the succession of the morphogenetic periods is signified by their multi-lined arrangement.
Résumé L'auteur propose de se servir, comme principe fondamental de classification sur des cartes géomorphologiques à petite échelle, de la classification génétique d'apres les processus exogènes. Dans la morphogénèse d'une région homogène on doit alors en général distinguer des phases de façonnement différentes, chaque phase représentant un groupe de plusieurs processus. On peut caractériser toute région d'une même morphogénèse par une formule dans laquelle chaque phase morphogénétique est signifiée par une série de lettres-clés pour les processus efficaces. et dans laquelle la succession des phases morphogénétiques est exprimée par un arrangement de ces séries l'une en dessous de l'autre.
: . : . , , , , — .
Erweiterte Fassung eines Vortrages auf der 58. Jahrestagung der Geologischen Vereinigung, Göttingen 1968. - Die Ausführungen gehen zurück auf Arbeiten an einem geomorphologischen Atlas, die seit längerer Zeit am Geographischen Institut der Universität Göttingen unter der Gesamtleitung von Prof. Dr. H.Poser durchgeführt werden. Herrn Prof.Poser und meinen Kollegen und Mitarbeitern möchte ich für alle die Anregungen, die sich in diesem Aufsatz niedergeschlagen haben, ohne daß sie im einzelnen zitiert werden können, herzlich danken. 相似文献
115.
Birgit Lange Fritz Scholz Hans-Joachim Bautsch Ferdinand Damaschun Gert Wappler 《Physics and Chemistry of Minerals》1993,19(7):486-491
The electrochemical reduction of xanthoconite, proustite, pyrostilpnite, and pyrargyrite was studied by abrasive stripping voltammetry, a technique which is based upon a preliminary mechanical transfer of trace amounts of the mineral onto the surface of a paraffin impregnated graphite electrode. Because the electrochemical reduction proceeds near to reversibility and is very similar for each pair of minerals, the peak potentials in differential pulse voltammetry can be used to calculate the standard enthalpy of phase transformation of xanthoconite to proustite and of pyrostilpnite to pyrargyrite: T
H
(xanth proust)
O = 35.46 ± 14.15 kJ/mol and T
H
(pyrostilp pyrarg)
O = 38.85 ± 6.60 kJ/mol. These values are not accessible otherwise until now. 相似文献
116.
The effect of horizontal grid resolution on the horizontal relative dispersion of particle pairs has been investigated on
a short time scale, i.e. one tidal M
2 cycle. Of particular interest is the tidal effect on dispersion and transports in coastal waters where small-scale flow features
are important. A three-dimensional ocean model has been applied to simulate the tidal flow through the Moskstraumen Maelstrom
outside Lofoten in northern Norway, well known for its strong current and whirlpools (Gjevik et al., Nature 388(6645):837–838,
1997; Moe et al., Cont Shelf Res 22(3):485–504, 2002). Simulations with spatial resolution down to 50 m have been carried out. Lagrangian tracers were passively advected with
the flow, and Lyapunov exponents and power law exponents have been calculated to analyse the separation statistics. It is
found that the relative dispersion of particles on a short time scale (12–24 h) is very sensitive to the grid size and that
the spatial variability is also very large, ranging from 0 to 100 km2 over a distance of 100 m. This means that models for prediction of transport and dispersion of oil spills, fish eggs, sea
lice etc. using a single diffusion coefficient will be of limited value, unless the models actually resolves the small-scale
eddies of the tidal current. 相似文献
117.
118.
Fluid and gas migration in the North German Basin: fluid inclusion and stable isotope constraints 总被引:1,自引:0,他引:1
Volker Lüders Christian Reutel Peer Hoth David A. Banks Birgit Mingram Thomas Pettke 《International Journal of Earth Sciences》2005,94(5-6):990-1009
Fluid inclusions have been studied in minerals infilling fissures (quartz, calcite, fluorite, anhydrite) hosted by Carboniferous
and Permian strata from wells in the central and eastern part of the North German Basin in order to decipher the fluid and
gas migration related to basin tectonics. The microthermometric data and the results of laser Raman spectroscopy reveal compelling
evidence for multiple events of fluid migration. The fluid systems evolved from a H2O–NaCl±KCl type during early stage of basin subsidence to a H2O–NaCl–CaCl2 type during further burial. Locally, fluid inclusions are enriched in K, Cs, Li, B, Rb and other cations indicating intensive
fluid–rock interaction of the saline brines with Lower Permian volcanic rocks or sediments. Fluid migration through Carboniferous
sediments was often accompanied by the migration of gases. Aqueous fluid inclusions in quartz from fissures in Carboniferous
sedimentary rocks are commonly associated with co-genetically trapped CH4–CO2 inclusions. P–T conditions estimated, via isochore construction, yield pressure conditions between 620 and 1,650 bar and temperatures between
170 and 300°C during fluid entrapment. The migration of CH4-rich gases within the Carboniferous rocks can be related to the main stage of basin subsidence and stages of basin uplift.
A different situation is recorded in fluid inclusions in fissure minerals hosted by Permian sandstones and carbonates: aqueous
fluid inclusions in calcite, quartz, fluorite and anhydrite are always H2O–NaCl–CaCl2-rich and show homogenization temperatures between 120 and 180°C. Co-genetically trapped gas inclusions are generally less
frequent. When present, they show variable N2–CH4 compositions but contain no CO2. P–T reconstructions indicate low-pressure conditions during fluid entrapment, always below 500 bar. The entrapment of N2–CH4 inclusions seems to be related to phases of tectonic uplift during the Upper Cretaceous. A potential source for nitrogen
in the inclusions and reservoirs is Corg-rich Carboniferous shales with high nitrogen content. Intensive interaction of brines with Carboniferous or even older shales
is proposed from fluid inclusion data (enrichment in Li, Ba, Pb, Zn, Mg) and sulfur isotopic compositions of abundant anhydrite
from fissures. The mainly light δ34S values of the fissure anhydrites suggest that sulfate is either derived through oxidation and re-deposition of biogenic
sulfur or through mixing of SO42−-rich formation waters with variable amounts of dissolved biogenic sulfide. An igneous source for nitrogen seems to be unlikely
since these rocks have low total nitrogen content and, furthermore, even extremely altered volcanic rocks from the study area
do not show a decrease in total nitrogen content. 相似文献
119.
Nitrogen geochemistry of Upper Carboniferous shales from the Central European Basin (CEB) was investigated by elemental analysis, stable isotope mass spectrometry and non-isothermal pyrolysis. Total N-contents of Namurian shales from four deep wells (4400–7000 m) in NE Germany ranged between 520 and 2680 ppm. Up to 90% of this nitrogen occurs as ammonium in minerals with δ15N values between + 1‰ and + 3.5‰. Low nitrogen contents (down to 460 ppm) and high δ15N values (up to + 5.6‰) in one well in the basin centre suggest a large-scale release of nitrogen associated with isotopic fractionation. Pyrolytic liberation of N2 from pelagic Namurian A shales of NW and NE Germany occurred at significantly lower temperatures than from paralic Namurian B shales and terrestrial Westphalian samples. On-line isotope analysis of N2 liberated between 400 and 1200 °C indicates the presence of precursor pools with different thermal stability and nitrogen isotopic composition. 相似文献
120.
The patterns of dissolved inorganic C (DIC) and aqueous CO2 in rivers and estuaries sampled during summer and winter in the Australian Victorian Alps were examined. Together with historical (1978–1990) geochemical data, this study provides, for the first time, a multi-annual coverage of the linkage between CO2 release via wetland evasion and CO2 consumption via combined carbonate and aluminosilicate weathering. δ13C values imply that carbonate weathering contributes ∼36% of the DIC in the rivers although carbonates comprise less than 5% of the study area. Baseflow/interflow flushing of respired C3 plant detritus accounts for ∼50% and atmospheric precipitation accounts for ∼14% of the DIC. The influence of in river respiration and photosynthesis on the DIC concentrations is negligible. River waters are supersaturated with CO2 and evade ∼27.7 × 106 mol/km2/a to ∼70.9 × 106 mol/km2/a CO2 to the atmosphere with the highest values in the low runoff rivers. This is slightly higher than the global average reflecting higher gas transfer velocities due to high wind speeds. Evaded CO2 is not balanced by CO2 consumption via combined carbonate and aluminosilicate weathering which implies that chemical weathering does not significantly neutralize respiration derived H2CO3. The results of this study have implications for global assessments of chemical weathering yields in river systems draining passive margin terrains as high respiration derived DIC concentrations are not directly connected to high carbonate and aluminosilicate weathering rates. 相似文献