全文获取类型
收费全文 | 334篇 |
免费 | 24篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 13篇 |
大气科学 | 43篇 |
地球物理 | 72篇 |
地质学 | 134篇 |
海洋学 | 16篇 |
天文学 | 73篇 |
自然地理 | 10篇 |
出版年
2022年 | 1篇 |
2021年 | 8篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 16篇 |
2017年 | 13篇 |
2016年 | 24篇 |
2015年 | 8篇 |
2014年 | 16篇 |
2013年 | 18篇 |
2012年 | 18篇 |
2011年 | 23篇 |
2010年 | 29篇 |
2009年 | 25篇 |
2008年 | 19篇 |
2007年 | 22篇 |
2006年 | 11篇 |
2005年 | 15篇 |
2004年 | 18篇 |
2003年 | 13篇 |
2002年 | 11篇 |
2001年 | 8篇 |
2000年 | 9篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有361条查询结果,搜索用时 46 毫秒
91.
Jessica Barabasch Mathieu Ducros Nicolas Hawie Samer Bou Daher Fadi Henri Nader Ralf Littke 《Basin Research》2019,31(2):228-252
The Eastern Mediterranean Levant Basin is a proven hydrocarbon province with recent major gas discoveries. To date, no exploration wells targeted its northern part, in particular the Lebanese offshore. The present study assesses the tectono‐stratigraphic evolution and related petroleum systems of the northern Levant Basin via an integrated approach that combines stratigraphic forward modeling and petroleum systems/basin modeling based on the previous published work. Stratigraphic modeling results provide a best‐fit realisation of the basin‐scale sedimentary filling, from the post‐rift Upper Jurassic until the Pliocene. Simulation results suggest dominant eastern marginal and Arabian Plate sources for Cenozoic siliciclastic sediments and a significant contribution from the southern Nilotic source mostly from Lower Oligocene to Lower Miocene. Basin modeling results suggest the presence of a working thermogenic petroleum system with mature source rocks localised in the deeper offshore. The generated hydrocarbons migrated through the deep basin within Jurassic and Cretaceous permeable layers towards the Latakia Ridge in the north and the Levant margin and offshore topographic highs. Furthermore, the basin model indicates a possibly significant influence of salt deposition during Messinian salinity crisis on formation fluids. Ultimately, the proposed integrated workflow provides a powerful tool for the assessment of petroleum systems in underexplored areas. 相似文献
92.
Ludovic Puig Göran Pilbratt Astrid Heske Isabel Escudero Pierre-Elie Crouzet Bram de Vogeleer Kate Symonds Ralf Kohley Pierre Drossart Paul Eccleston Paul Hartogh Jeremy Leconte Giusi Micela Marc Ollivier Giovanna Tinetti Diego Turrini Bart Vandenbussche Paulina Wolkenberg 《Experimental Astronomy》2018,46(1):211-239
ARIEL, the Atmospheric Remote sensing Infrared Exoplanet Large survey, is one of the three M-class mission candidates competing for the M4 launch slot within the Cosmic Vision science programme of the European Space Agency (ESA). As such, ARIEL has been the subject of a Phase A study that involved European industry, research institutes and universities from ESA member states. This study is now completed and the M4 down-selection is expected to be concluded in November 2017. ARIEL is a concept for a dedicated mission to measure the chemical composition and structure of hundreds of exoplanet atmospheres using the technique of transit spectroscopy. ARIEL targets extend from gas giants (Jupiter or Neptune-like) to super-Earths in the very hot to warm zones of F to M-type host stars, opening up the way to large-scale, comparative planetology that would place our own Solar System in the context of other planetary systems in the Milky Way. A technical and programmatic review of the ARIEL mission was performed between February and May 2017, with the objective of assessing the readiness of the mission to progress to the Phase B1 study. No critical issues were identified and the mission was deemed technically feasible within the M4 programmatic boundary conditions. In this paper we give an overview of the final mission concept for ARIEL as of the end of the Phase A study, from scientific, technical and operational perspectives. 相似文献
93.
94.
Growth kinetics of enstatite reaction rims studied on nano-scale,Part I: Methodology,microscopic observations and the role of water 总被引:1,自引:0,他引:1
Ralf Milke Ralf Dohmen Hans-Werner Becker Richard Wirth 《Contributions to Mineralogy and Petrology》2007,154(5):519-533
The kinetics of (Mg, Fe)SiO3 pyroxene layer growth within silicate thin films with total thickness <1 μm was studied experimentally at 0.1 MPa total pressure,
controlled fO2 and temperatures from 1,000 to 1,300°C. The starting samples were produced by pulsed laser deposition. Layer thickness before
and after the experiments and layer composition as well as microstructures, grain size and shape of the interfaces were determined
by Rutherford back scattering and transmission electron microscopy assisted by focused ion beam milling. Due to the miniaturization
of the starting samples and the use of high resolution analytical methods the experimentally accessible temperature range
for rim growth experiments was extended by about 300°C towards lower temperatures. The thickness of the layers at a given
temperature increases proprotional to the square root of time, indicating a diffusion-controlled growth mechanism. The temperature
dependence of rim growth yields an apparent activation energy of 426 ± 34 kJ/mol. The small grain size in the orthopyroxene
rims implies a significant contribution of grain boundary diffusion to the bulk diffusion properties of the polycrystalline
rims. Based on microstructural observations diffusion scenarios are discussed for which the SiO2 component behaves immobile relative to the MgO component. Volume diffusion data for Mg in orthopyroxene from the literature
indicate that the measured diffusivity is probably controlled by the mobility of oxygen. The observed reaction rates are consistent
with earlier results from dry high-temperature experiments on orthopyroxene rim growth. Compared to high pressure experiments
at 1,000°C and low water fugacities, reaction rates are 3–4 orders of magnitude smaller. This observation is taken as direct
evidence for a strong effect of small amounts of water on diffusion in silicate polycrystals. In particular SiO2 changes from an immobile component at dry conditions to an extremely mobile component even at very low water fugacities. 相似文献
95.
Ralf Greve 《Climatic change》2000,46(3):289-303
Numerical computations are performed with the three-dimensional polythermal ice-sheet model SICOPOLIS in order to investigate the possible impact of a greenhouse-gas-induced climate change on the Greenland ice sheet. The assumed increase of the mean annual air temperature above the ice covers a range from T = 1°C to 12°C, and several parameterizations for the snowfall and the surface melting are considered. The simulated shrinking of the ice sheet is a smooth function of the temperature rise, indications for the existence of critical thresholds of the climate input are not found. Within 1000 model years, the ice-volume decrease is limited to 10% of the present volume for T 3°C, whereas the most extreme scenario, T = 12°C, leads to an almost entire disintegration, which corresponds to a sea-level equivalent of 7 m. The different snowfall and melting parameterizations yield an uncertainty range of up to 20% of the present ice volume after 1000 model years. 相似文献
96.
Rüdiger Lutz Birgit Gieren Andreas Lückge Heinz Wilkes Ralf Littke 《Organic Geochemistry》2000,31(12)
Investigation of sediment samples from Sites 1039 and 1040 (ODP Leg 170) drilled off the Nicoya peninsula (Costa Rica) by organic geochemical and organic petrological methods has revealed that subduction has only little influence on the composition of the sedimentary organic matter. Organic carbon contents reached 1.5% in the Pleistocene samples but Miocene and Pliocene sediments had an average organic carbon content of less than 0.5%. Organic carbon/sulfur ratios are generally below 2.8, reflecting an intense sulfate reduction in the uppermost sediments which was enhanced by sulfate supply both from sea water and deeper strata. Microscopical examinations indicate that the organic matter is mainly derived from marine sources. A small amount of terrigenous organic matter is, however, present as well according to n-alkane and fatty acid distributions. The alkenone unsaturation index U37k′ shows only a slight decrease during the Miocene and Pliocene, and stronger variations in the Pleistocene, probably indicating more stable sea surface temperatures during the Miocene and Pliocene. Variations in the Pleistocene can possibly be related to glacial/interglacial changes. 相似文献
97.
From basalt to dacite: origin and evolution of the calc-alkaline series of Salina, Aeolian Arc, Italy 总被引:1,自引:1,他引:0
The island of Salina comprises one of the most distinct calc-alkaline series of the Aeolian arc (Italy), in which calc-alkaline,
high-K calc-alkaline, shoshonitic and leucite-shoshonitic magma series are developed. Detailed petrological, geochemical and
isotopic (Sr, Nd, Pb, O) data are reported for a stratigraphically well-established sequence of lavas and pyroclastic rocks
from the Middle Pleistocene volcanic cycle (430–127 ka) of Salina, which is characterized by an early period of basaltic volcanism
(Corvo; Capo; Rivi; Fossa delle Felci, group 1) and a sequence of basaltic andesites, and andesites and dacites in the final
stages of activity (Fossa delle Felci, groups 2–8). Major and trace element compositional trends, rare earth element (REE)
abundances and mineralogy reveal the importance of crystal fractionation of plagioclase + clinopyroxene + olivine/ orthopyroxene ± titanomagnetite ± amphibole ± apatite
in generating the more evolved magma types from parental basaltic magmas, and plagioclase accumulation in producing the high
Al2O3 contents of some of the more evolved basalts. Sr isotope ratios range from 0.70410 to 0.70463 throughout the suite and show
a well-defined negative correlation with 143Nd/144Nd (0.51275–0.51279). Pb isotope compositions are distinctly radiogenic with relatively large variations in 206Pb/204Pb (19.30–19.66), fairly constant 207Pb/204Pb (15.68–15.76) and minor variations in 208Pb/204Pb ratios (39.15–39.51). Whole-rock δ18O values range from +6.4 to +8.5‰ and correlate positively with Sr isotope ratios. Overall, the isotopic variations are correlated
with the degree of differentiation of the rocks, indicating that only small degrees of crustal assimilation are overprinting
the dominant evolution by crystal–liquid fractionation (AFC-type processes). The radiogenic and oxygen isotope composition
of the Salina basalts suggests derivation from primary magmas from a depleted mantle source contaminated by slab-derived fluids
and subducted sediments with an isotopic signature of typical upper continental crust. These magmas then evolved further to
andesitic and dacitic compositions through the prevailing process of low-pressure fractional crystallization in a shallow
magma reservoir, accompanied by minor assimilation of crustal lithologies similar to those of the Calabrian lower crust.
Received: 29 November 1999 / Accepted: 16 April 2000 相似文献
98.
An algorithm for the estimation of root zone soil moisture is presented. Global fields of the soil moisture within the uppermost metre of soil are derived with a temporal resolution of 10 days. For calibration, long-term soil moisture observations from the former Soviet Union are used. The variance of the measurements is largely dominated by the spatial variability of the long-term mean soil moisture, while the temporal variability gives comparatively small contribution. Consequently, the algorithm is organised into two steps. The first step concentrates on the retrieval of the spatial variance of the long-term means, which comprises more than 85% of the total soil moisture variability. A major part of the spatial variance can be explained by four easily available fields: the climatological precipitation, land use, soil texture, and terrain slope. The second step of the algorithm is dedicated to the local temporal variability. This part of variability is recovered by using passive microwave data from scanning multichannel microwave radiometre (SMMR) supported by monthly averaged fields of air temperature and precipitation. The 6-GHz channel of SMMR is shown to be severely disturbed by radio frequency interference, so that information from the 10-GHz channel is used instead. The algorithm provides reasonable soil moisture fields which is confirmed by a comparison with independent measurements from Illinois. 相似文献
99.
Regional mean sea level changes in the German Bight are considered. Index time series derived from 15 tide gauge records are
analysed. Two different methods for constructing the index time series are used. The first method uses arithmetic means based
on all available data for each time step. The second method uses empirical orthogonal functions. Both methods produce rather
similar results for the time period 1924–2008. For this period, we estimate that regional mean sea level increased at rates
between 1.64 and 1.74 mm/year with a 90% confidence range of 0.28 mm/year in each case. Before 1924, only data from a few
tide gauges are available with the longest record in Cuxhaven ranging back till 1843. Data from these tide gauges, in particular
from Cuxhaven, thus receive increasingly more weight when earlier years are considered. It is therefore analysed to what extent
data from Cuxhaven are representative for the regional sea level changes in the German Bight. While this cannot be clarified
before 1924, it is found that this is not the case from 1924 onwards when changes in Cuxhaven can be compared to that derived
from a larger data set. Furthermore, decadal variability was found to be substantial with relatively high values towards the
end of the analysis period. However, these values are not unusual when compared to earlier periods. 相似文献
100.
Modelling studies were performed with the multiphase mechanism RACM-MIM2ext/CAPRAM 3.0i to investigate the tropospheric multiphase chemistry in deliquesced particles and non-precipitating clouds using the SPACCIM model framework. Simulations using a non-permanent cloud scenario were carried out for two different environmental conditions focusing on the multiphase chemistry of oxidants and other linked chemical subsystems. Model results were analysed by time-resolved reaction flux analyses allowing advanced interpretations. The model shows significant effects of multiphase chemical interactions on the tropospheric budget of gas-phase oxidants and organic compounds. In-cloud gas-phase OH radical concentration reductions of about 90 % and 75 % were modelled for urban and remote conditions, respectively. The reduced in-cloud gas-phase oxidation budget increases the tropospheric residence time of organic trace gases by up to about 30 %. Aqueous-phase oxidations of methylglyoxal and 1,4-butenedial were identified as important OH radical sinks under polluted conditions. The model revealed that the organic C3 and C4 chemistry contributes with about 38 %/48 % and 8 %/9 % considerably to the urban and remote cloud / aqueous particle OH sinks. Furthermore, the simulations clearly implicate the potential role of deliquescent particles to operate as a reactive chemical medium due to an efficient TMI/HOx,y chemical processing including e.g. an effective in-situ formation of OH radicals. Considerable chemical differences between deliquescent particles and cloud droplets, e.g. a circa 2 times more efficient daytime iron processing in the urban deliquescent particles, were identified. The in-cloud oxidation of methylglyoxal and its oxidation products is identified as efficient sink for NO3 radicals in the aqueous phase. 相似文献