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51.
Hosein Haghi Holger Baumgardt Pavel Kroupa Eva K. Grebel Michael Hilker Katrin Jordi 《Monthly notices of the Royal Astronomical Society》2009,395(3):1549-1557
We investigate the mean velocity dispersion and the velocity dispersion profile of stellar systems in modified Newtonian dynamics (MOND), using the N -body code n-mody , which is a particle-mesh-based code with a numerical MOND potential solver developed by Ciotti, Londrillo & Nipoti. We have calculated mean velocity dispersions for stellar systems following Plummer density distributions with masses in the range of 104 to 109 M⊙ and which are either isolated or immersed in an external field. Our integrations reproduce previous analytic estimates for stellar velocities in systems in the deep MOND regime ( a i , a e ≪ a 0 ) , where the motion of stars is either dominated by internal accelerations ( a i ≫ a e ) or constant external accelerations ( a e ≫ a i ) . In addition, we derive for the first time analytic formulae for the line-of-sight velocity dispersion in the intermediate regime ( a i ∼ a e ∼ a 0 ) . This allows for a much-improved comparison of MOND with observed velocity dispersions of stellar systems. We finally derive the velocity dispersion of the globular cluster Pal 14 as one of the outer Milky Way halo globular clusters that have recently been proposed as a differentiator between Newtonian and MONDian dynamics. 相似文献
52.
A map depicting predicted classes of soil magnetic susceptibility in Angola was produced. The map is based on a classification
system for the susceptibility of tropical soils set up by the authors and a 1:2,000,000 scale FAO soil map. Statistical data
of two large groups of parent rock—ultrabasic, basic and intermediate igneous rocks on the one hand and acid igneous rocks
and some slightly metamorphosed rocks and clastic sediments on the other—had been linked to three associated degrees of weathering.
These determining factors were used to classify Angolan soils, and the overall method is semi-quantitative. The resulting
map shows that easily available pedological information as given by FAO soil maps is generally appropriate to predict soil
magnetic susceptibility. Potential metal detector performance failures may be predicted. The resulting information is a useful
tool for planning the use of appropriate techniques in landmine clearance operations. 相似文献
53.
Holger Klein 《Ocean Dynamics》1995,47(2):77-92
Summary A bottom mounted BroadBand ADCP was deployed for about two months in the German Bight (54° 15.3′, N, 7° 35.5′ E) at 40 m depth.
The ADCP recorded current data and echo intensity between 3 and 38m depth with a vertical resolution of 1 m. The data, which
provide continuous vertical current profiles, are investigated with regard to the vertical variations of residual and tidal
currents and kinetic energies. To investigate the temporal variability of the current profiles, the time series are subdivided
into 8-day intervals. Furthermore, the data are compared with historical data. According to the ADCP profiles, the water column
can be subdivided into three layers: A primarily wind-driven near-surface layer (∼10m), a middepth layer with great directional
variability, and a near-bottom layer of about 10 m thickness with a strictly logarithmic current profile.
über das Stromprofil in der Deutschen Bucht: Eine zweimonatige BroadBand ADCP Zeitserie mit hoher vertikaler Aufl?sung
Zusammenfassung Ein am Boden stehender BroadBand ADCP wurde für zwei Monate in der Deutschen Bucht (54° 15.3′ N, 7° 35.5′ E) in 40 m Wassertiefe eingesetzt. Er registrierte Str?mungsdaten und Echointensit?t zwischen 3 und 38 m Wassertiefe mit einer vertikalen Aufl?sung von 1 m. Dieser Datensatz, der kontinuierliche vertikale Stromprofile liefert, wird hinsichtlich der vertikalen Variation von Rest- und Gezeitenstr?men und kinetischer Energie analysiert. Zur Untersuchung der zeitlichen Variabilit?t der Stromprofile wird die Gesamtzeitserie in 8-Tage-Intervalle unterteilt. Ferner werden die Ergebnisse mit historischen Messungen verglichen. Aus den ADCP-Profilen ergibt sich eine prinzipielle Dreiteilung der Wassers?ule: Eine vorwiegend windgetriebene oberfl?chennahe Schicht (∼10m), eine mittlere Schicht mit hoher Richtungsvariabilit?t und eine etwa 10 m m?chtige Bodenschicht mit streng logarithmischem Stromprofil.相似文献
54.
Characterization of sediments in an abandoned mining area; a case study of Mansfeld region,Germany 总被引:1,自引:0,他引:1
Rainer?WennrichEmail author Jürgen?Mattusch Peter?Morgenstern Klaus?Freyer Hanns-Christian?Treutler Hans-Joachim?St?rk Lutz?Brüggemann Albrecht?Paschke Birgit?Daus Holger?Weiss 《Environmental Geology》2004,45(6):818-833
The distribution of selected heavy metals, including some radionuclides, metalloids and non-metals was determined in stream sediments in a region influenced by abandoned copper mining and ore processing activities. A considerable amount of the ore processing waste with a very complex composition and highly elevated concentrations of zinc, sulfur, lead, copper, arsenic, and a lot of other elements in the range between 100 and 1,000 mg/kg (Sb, Mn, Ni, Cr, Cd, Hg, and Ag) was piled up on mine dumps. The dispersion of the pollutants originating from this source and their environmental impact were investigated. Both, sediments and original waste material were studied to indicate the pathways and the mobilization behavior of different pollutants. For this purpose, the process of the elution of pollutants by application of different fractionation schemes was studied. The capabilities of different analytical techniques are shown for the analysis of solid samples (X-ray fluorescence spectrometry, Gamma-spectrometry) and liquid ones (ICP-atomic emission spectrometry, ICP-mass spectrometry and different techniques of atomic absorption). Additionally, the coupling of ion chromatography and ICP-MS detection was used to study the distribution of arsenic species in the sediment cores of a lake which acts as a natural sink for the region. 相似文献
55.
Martin Bak Hansen Holger Lykke-Andersen Ali Dehghani Dirk Gajewski Christian Hübscher Morten Olesen Klaus Reicherter 《International Journal of Earth Sciences》2005,94(5-6):1070-1082
A dense grid of multichannel high-resolution seismic sections from the Bay of Kiel in the western Baltic Sea has been interpreted
in order to reveal the Mesozoic and Cenozoic geological evolution of the northern part of the North German Basin. The overall
geological evolution of the study area can be separated into four distinct periods. During the Triassic and the Early Jurassic,
E–W extension and the deposition of clastic sediments initiated the movement of the underlying Zechstein evaporites. The deposition
ceased during the Middle Jurassic, when the entire area was uplifted as a result of the Mid North Sea Doming. The uplift resulted
in a pronounced erosion of Upper Triassic and Lower Jurassic strata. This event is marked by a clear angular unconformity
on all the seismic sections. The region remained an area of non-deposition until the end of the Early Cretaceous, when the
sedimentation resumed in the area. Throughout the Late Cretaceous the sedimentation took place under tectonic quiescence.
Reactivated salt movement is observed at the Cretaceous Cenozoic transition as a result of the change from an extensional
to compressional regional stress field. The vertical salt movement influenced the Cenozoic sedimentation and resulted in thin-skinned
faulting. 相似文献
56.
Arsenic fixation on iron-hydroxide-rich and plant litter-containing sediments in natural environments 总被引:2,自引:0,他引:2
Iron-hydroxide-rich and plant litter-containing sediments from natural sites contaminated with uranium mine tailing leachates were examined for their ability to adsorb arsenic. The samples with high contents of iron hydroxides (Fetotal concentration, >300 g kg−1) exhibited remarkable fixation of arsenic (up to 40 g As kg−1). This value corresponded approximately to the supersaturation point for natural iron hydroxides under the present conditions, and it was significantly lower than the value found for synthetic iron hydroxides. There was a strong correlation (R=0.8999) between the concentration of iron and that of arsenic at low arsenic contents, indicating adsorption on strong binding sites. Although all the samples had noticeable contents of organic carbon (plant litter), calcium, and manganese, no obvious effect of these elements on arsenic fixation could be detected. The amount of iron hydroxides was found the only fixation-controlling parameter immediately below a leaching water source. 相似文献
57.
Research on tsunami-induced coarse-clast transport is a field of rising interest since such deposits have been identified as useful proxies for extreme-wave events (tsunamis, storm waves) that provide crucial information for coastal hazard assessment. Physical experiments are, beside in-situ observations, the foundation of our understanding of how boulders are transported by tsunamis and provide clues to the development of empirical equations and numerical models describing the processes and fundamental mechanics. Nevertheless, investigating tsunami-induced boulder transport is a comparatively young discipline and only a few experimental studies focusing on this topic have been published so far. To improve the knowledge on nearshore tsunami hydrodynamics, physical experiments utilizing real-world boulder shapes have been carried out simulating three different shore types in a wave flume. Crucial insights were gained into boulder transport hydrodynamics and data resulting from the experiments were analysed in an empirical, statistical, quantitative and qualitative manner. The regular cuboid boulder – one of the specific shapes used in the experiments – showed the longest transport distances compared to a complex, natural boulder and a flat cuboid boulder, but also significant fluctuations regarding the total transport distance. The experiments indicate a strong influence of the shore shape on boulder transport behaviour. Experimental setups of increased mean transport distances also led to a higher spreading of results. This spreading was further amplified between the idealized-shaped cuboid and the complex-shaped boulder, which is associated with a lower drag coefficient. Due to the highly sensitive boulder reaction to divergent experimental setups, the need to recognize boundary conditions overcoming commonly considered parameters (e.g. roughness or Flatness Index) in field studies and numerical models is underlined. Beside the strong influence of initial boulder submergence and alignment, both the boulder shape and shore type influence the boulder transport pattern, increasing the total transport distance by more than 350% in some cases. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd 相似文献
58.
The use of ultrasonic anemometers under cloudy weather conditions is often doubted, even rejected or not discussed in the literature. To investigate the influence of liquid water content on the behaviour of sonic anemometers a small intercomparison experiment using an ultrasonic anemometer, a fast response propeller anemometer, and a Particulate Volume Monitor was performed at the German Environmental Research Station Schneefernerhaus near the top of Mt. Zugspitze. The results obtained under different conditions (dry/cloudy) give no significant hint on such an influence. 相似文献
59.
Cecilia Johansson Barbara Hennemuth Jens Bösenberg Holger Linné Ann-sofi Smedman 《Boundary-Layer Meteorology》2005,114(2):389-412
Double-layered structures found over the Baltic Sea are investigated using radiosoundings and lidar measurements. Situations with double-layer structures are also simulated with the regional model REMO in a realistic manner. The double layer consists of two adjacent well-mixed layers, with a sharp inversion in between.Results from radiosoundings show that the double-layer structure over the Baltic Sea mainly occurs during the autumn with thermally unstable stratification near the surface. The structure is present in about 50 % of the radiosoundings performed during autumn. The presence of the double-layer structure cannot be related to any specific wind direction, wind speed or sea surface temperature.The lidar measurements give a more continuous picture of the time evolution of the double-layer structure, and show that the top of the lower layer is not a rigid lid for vertical transport. Two possible explanations of the double-layer structure are given, (i) the structure is caused by `advection' of land boundary-layer air over the convective marine boundary layer or, (ii) by development of Sc clouds in weak frontal zones connected to low pressure systems. Also the forming of Cu clouds is found to be important for the development of a double-layer structure. 相似文献
60.