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311.
Dr. Friedrich Lippmann 《Contributions to Mineralogy and Petrology》1954,4(1-2):130-134
Zusammenfassung Durch röntgenographisehe und differentialthermoanalytische Untersuchungen wurde in einem roten Keuperton (km 3) von Zaisersweiher bei Maulbronn ein quellfähiges chloritisches Mineral (Corrensit) als Hauptbestandteil gefunden, das sick durch doppelten Basisabstand (28 Å) auszeichnet. Daneben treten Illit (Glimmer) und Quarz auf. Nebengemengteile sind Hämatit und Feldspat.Herrn Professor Dr.Carl W. Correns zum 60. Geburtstag gewidmet. 相似文献
312.
E. V. Badanina V. V. Gordienko A. Wiechowski G. Friedrich 《Geology of Ore Deposits》2008,50(8):772-781
Composition and localization of REE mineralization in miarolitic pegmatites and its role in the pegmatite formation were studied at the Malkhan gem deposit (jewel-quality tourmaline, morganite, danburite, and hambergite) in the central Transbaikal region. The chemical composition of Ti-, Ta-, Nb- and REE-bearing minerals, their relationships with rock-forming and accessory minerals indicate that two geochemically specialized stages of pegmatite formation are distinguished. The early stage gave rise to the crystallization of quartz-feldspar aggregates including K-feldspar block zone with Sc and REE mineralization. The rare-metal (Li, Cs, F, B, Be) albite-lepidolite-cleavelandite complex with pockets of gem mineralization was formed at the late stage. 相似文献
313.
News from the Lower Ionosphere: A Review of Recent Developments 总被引:1,自引:1,他引:0
Current knowledge concerning the lower ionosphere (D- and E-region) is reviewed with an emphasis on new aspects of empirical results. Starting with an overview of experimental techniques
and corresponding data bases, both regarding charged as well as the most relevant neutral constituents of this altitude range,
the ionospheric variability is discussed both concerning regular (e.g. diurnal and seasonal) as well as irregular variations
(e.g. driven by the variability of nitric oxide). We then turn to ‘new players’ in the lower ionosphere, i.e. charged aerosol
particles such as mesospheric ice particles in noctilucent clouds or polar mesospheric summer echoes and meteor smoke particles
originating from ablated meteoric matter. These species have received considerable attention in recent years, in part because
it is speculated that observations of their properties might be useful for the detection of climate change signals. The available
experimental data base regarding these species is reviewed and we show that there is now compelling evidence for the ubiquitous
presence of these very heavy charge carriers throughout the lower ionosphere. While many fundamental details regarding these
charged species are not yet completely understood, this emphasizes that charged aerosol particles may not be neglected in
a comprehensive treatment of the lower ionospheric charge balance and related phenomena. Finally, we close with suggestions
for future research. 相似文献
314.
Geomorphometric feature analysis using morphometric parameterization and artificial neural networks 总被引:3,自引:0,他引:3
This paper presents a semi-automatic method using an unsupervised neural network to analyze geomorphometric features as landform elements. The Shuttle Radar Topography Mission (SRTM) provided detailed digital elevation models (DEMs) for all land masses between 60°N and 57°S. Exploiting these data for recognition and extraction of geomorphometric features is a challenging task. Results obtained with two methods, Wood's morphometric parameterization and the Self Organizing Map (SOM), are presented in this paper.Four morphometric parameters (slope, minimum curvature, maximum curvature and cross-sectional curvature) were derived by fitting a bivariate quadratic surface with a window size of 5 by 5 to the SRTM DEM. These parameters were then used as input to the two methods. Wood's morphometric parameterization provides point-based features (peak, pit and pass), line-based features (channel and ridge) and area-based features (planar). Since point-based features are defined as having a very small slope when their neighbors are considered, two tolerance values (slope tolerance and curvature tolerance) are introduced. Selection of suitable values for the tolerance parameters is crucial for obtaining useful results.The SOM as an unsupervised neural network algorithm is employed for the classification of the same morphometric parameters into ten classes characterized by morphometric position (crest, channel, ridge and plan area) subdivided by slope ranges. These terrain features are generic landform element and can be used to improve mapping and modeling of soils, vegetation, and land use, as well as ecological, hydrological and geomorphological features. These landform elements are the smallest homogeneous divisions of the land surface at the given resolution. The result showed that the SOM is an efficient scalable tool for analyzing geomorphometric features as meaningful landform elements, and uses the full potential of morphometric characteristics. 相似文献
315.
G. Tetzlaff R. Dlugi K. Friedrich G. Gross D. Hinneburg U. Pahl M. Zelger N. Mölders 《Journal of Atmospheric Chemistry》2002,42(1):123-155
An explicit multi-layer subgrid-scheme was developed for ameso-/-scale model to consider subgrid-scale surface heterogeneity, dry deposition, biogenic and anthropogenic emission of trace gases. Since dry deposition measurements of highly reactive trace species are scarce we try to evaluate this scheme by heuristic principles. The results of simulations conducted for a 5×5 km2 resolution with and without thisscheme are evaluated by using results of a model run with 1×1 km2resolution, which is taken as a `grand thruth' and which has the same resolution as the subgrid. The explict multi-layer subgrid scheme provides a similar distribution of dry deposition fluxes as the much more computationally expensive simulation with the 1×1 km2 resolution.Dry deposition fluxes determined from observations give evidence that the explicit multi-layer subgrid scheme which does not require a constant flux approximation for a layer of several decameters leads to an improvement in determining the exchange between the atmosphere and the ground.Results of simulations with a microscale model show that the inhomogeneity at forest edges leads to an increase of the turbulent transports of up to a factor 4 compared to horizontally homogeneous terrain, which is assumed to be the conditions of the subgrid cells (and which is usually the assumption for the entire grid cell in mesoscale models). Inhomogeneity inside an extended stand of trees causes an overall increase of 5–10% withhigh local extremes, i.e. such an inhomogeneity results to an underestimation of dry deposition in meso-/-scale models. The effects are most pronounced for a wind direction perpendicular to the forest edge. 相似文献
316.
Abstract— Early “regolith-evolution” experiments using fragmental, polycrystalline gabbro targets displayed mineral-specific comminution trends, with feldspar being significantly fractionated into the finest grain sizes. Since planetary regoliths are similar mixtures of lithic and monomineralic detritus, the comminution of monomineralic grains is important in understanding the evolution of such regoliths. Particulate targets of monomineralic feldspar, olivine, pyroxene, and quartz therefore were subjected to at least 25 impacts each to complement the previous gabbro-based investigations. Stainless-steel projectiles 3.18 mm in diameter were launched at the targets at nominal velocities of 1.4 km s?1, depositing an average of about 2.6 × 106 ergs per g of target per impact. The quartz and feldspar comminuted most readily, while olivine and pyroxene were the most resistant. In addition, the feldspar and quartz were virtually indistinguishable in terms of any measure of comminution used here. The behavior of the olivine differed somewhat from that of the pyroxene, but the variation between these two minerals was much less than the difference between them and the tectosilicates. The apparent energy required to create new surfaces through comminution was about a factor of two higher for the mafic minerals. Densities of pre-existing cracks and other crystal defects depend on sample preparation techniques, among other things, and appear to play a notable role in the early evolution of these “regoliths.” It is probable that the history of a particular regolith's parent rocks will exert a comparable influence on the early stages of evolution of a planetary regolith. The trends for the individual targets in these monomineralic series duplicated those exhibited by the gabbro charges, leading to the general conclusion that mineral-specific comminution will occur during repetitive impact of planetary surfaces, whether they comprise freshly excavated, large blocks, or highly comminuted, clastic fines containing substantial fractions of monomineralic debris. This mineral-specific behavior will cause small grain sizes in planetary regoliths to be substantially fractionated relative to coarse regolith components, and especially relative to their source rocks. 相似文献
317.
A radioisotope energy-dispersive X-ray (EDX) system has been used on board the German research vessel “Valdivia” during an exploration expedition in the northern equatorial Pacific in 1973. The instrumentation used consisted of an X-ray detection system incorporating a 30 mm2 effective-area Si (Li) detector with a measured energy resolution of 195 eV for Mn Kα X-rays, standard nuclear electronics, a 1024-channel analyser and a data read-out unit. The X-ray spectra in the manganese-nodule samples were excited by a 30-mCi 238Pu source.The six elements Mn, Fe, Co, Ni, Cu and Zn were analysed on board. Precision values for the analyses were less than 3% for Mn, Fe, Ni, Cu and Zn and about 5% for Co. A total amount of 350 analyses was carried out during a one-month cruise.Average contents of 190 analysed whole manganese-nodule samples from all the sampling sites of the covered area were 23.3% Mn, 6.7% Fe, 0.23% Co, 1.16% Ni, 0.94% Cu and 0.10% Zn. The average content of the base metals expressed as the sum of the Co, Ni, Cu and Zn contents was 2.48%. A linear relationship between Mn and Ni in all analysed samples, including whole manganese-nodule samples, zones of manganese nodules and manganese crusts, was observed. The Mn/Ni ratio calculated by regression analysis was 23.0. Zonal variations of the chemical contents of the six elements in the manganese nodules were found. A size classification of the manganese nodules has been suggested. Geochemical correlations of Cu and Ni versus Mn/Fe in the investigated samples are given. 相似文献
318.
Friedrich Kiefer 《Aquatic Sciences - Research Across Boundaries》1963,25(1):40-48
Ohne Zusammenfassung
Herrn Prof. Dr. A. Remane, Kiel, zum 65. Geburtstag gewidmet. 相似文献
319.
320.
Bruno Merz Jana Friedrich Markus Disse Jochen Schwarz Johann G. Goldammer Jochen Wächter 《Natural Hazards》2006,38(1-2):3-20
The German Research Network for Natural Disasters (DFNK) linked 15 partners with scientific expertise in the field of natural
hazards. Main objectives were the development and provision of the scientific fundamentals for an advanced risk management
of important natural disasters in Germany, i.e., floods, earthquakes, storms and wildland fires. This included risk analyses,
the development of information systems for supporting disaster management, and recommendations for risk reduction measures.
This paper gives an overview of DFNK and summarises its experiences concerning multidisciplinarity and user-orientation. It
illustrates the concept of risk chains, causally linking the different processes from hazard to risk. The step from hazard
to risk requires interdisciplinary research teams. The experiences show that integrative concepts allow results not achievable
with mono-disciplinary approaches. Integrative approaches pave the way to harmonised safety considerations taking into account
the different hazards in a region within a common framework. User-orientation, policy advice and development of operational
tools are key issues of disaster research. The experiences of DFNK illustrate the limitations of a research network in bridging
the gap between research and application within rather short-term projects. Successful cooperation with users could be established
by those activities where, at the beginning of the project, a user was identified who had a strong interest in solving an
urgent problem. 相似文献