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A suite of vast stellar surveys mapping the Milky Way, culminating in the Gaia mission, is revolutionizing the empirical information about the distribution and properties of stars in the Galactic stellar disk. We review and lay out what analysis and modeling machinery needs to be in place to test mechanism of disk galaxy evolution and to stringently constrain the Galactic gravitational potential, using such Galactic star-by-star measurements. We stress the crucial role of stellar survey selection functions in any such modeling; and we advocate the utility of viewing the Galactic stellar disk as made up of ‘mono-abundance populations’ (MAPs), both for dynamical modeling and for constraining the Milky Way’s evolutionary processes. We review recent work on the spatial and kinematical distribution of MAPs, and point out how further study of MAPs in the Gaia era should lead to a decisively clearer picture of the Milky Way’s dark-matter distribution and formation history. 相似文献
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Temperature is critical to maintaining seed viability under long-term storage conditions. It has been common practice to use refrigeration systems to maintain required storage temperatures. A seed repository constructed in permafrost in Yakutsk, Russia is the first seed storage facility that relies solely on natural cold. This paper describes the design and performance of the cooling system of the repository. An innovative aspect of the cooling system is that it utilizes the patterns of temperature wave propagation in permafrost. Predicted and measured ground temperatures for the first year of operation are presented and analyzed. Results indicate that convection air cooling systems can be used to control the temperature regime in underground facilities in permafrost. 相似文献
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G. Henrici D. Hofmann H.-W. Georgii K. O. Groeneveld 《Journal of Atmospheric Chemistry》1991,12(4):391-400
PIXE is a well established and valuable method for quantitative and qualitative aerosol elemental analysis. Using this method, we have developed a technique to simultaneously analyse the trace-element content in precipitation for elements with Z> 12. Freeze-drying and leaching was used as a nonselective preconcentration technique. A special backing foil to take up the sample liquid to be dried was developed for these experiments. By careful adjustment of the experimental parameters, we reached a detection limit lower than 1 ppb for most detected elements. Thus, it will be possible to analyze precipitation at low concentrations of trace elements which are important for air chemistry and environmental studies.Supported by DFG/Bonn under Sonderforschungsbereich 233. 相似文献
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Zusammenfassung Die vorliegende Arbeit behandelt Gefrierkernmessungen, die im Rahmen eines europäischen Gemeinschaftsprogrammes auf dem Kleinen Feldberg/Taunus vorgenommen wurden. Ein Ziel dieser Arbeiten war die Aufdeckung und Deutung sommerlicher Anomalien der Gefrierkernkonzentration. Die Ergebnisse zeigen, daß während des Sommers 1964 aufgetretene Anomalien im wesentlichen regionalen Einflüssen zugeschrieben werden können. Ein Zusammenhang mit den an verschiedenen in Frankreich, Italien, Österreich und Spanien unterhaltenen Meßstellen gleichzeitig gewonnenen Ergebnissen ist nicht nachweisbar.
Summary This paper deals with measurements of the concentration of atmospheric freezingnuclei carried out in the frame of an European cooperative program. The investigations described here were made on Mt. Kleiner Feldberg/Taunus. They aimed at detecting and explaining anomalies of the freezing-nucleus concentration generally occurring during the summer-months. The results show that the anomalies observed on Mr. Kleiner Feldberg during summer 1964 are mainly caused by regional phenomena. There exists hardly any connection to results gained at the same time at sites of measurement in France, Italy, Austria and Spain.相似文献
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A three-stage vertical-flow thermal gradient vapour diffusion chamber for the fast, continuous measurement of the number concentration of cloud condensation nuclei (CCN) at three different water vapour supersaturations was constructed. CCN are monitored by imaging cloud droplets in the chamber with a CCD-camera. The counting of droplets and the control of all instrumental parameters are computerized. The instrument was calibrated with NaCl-aerosols, and was successfully operated in the field. Data from 2 weeks of field measurements at an island in the North Sea are presented. 相似文献
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W. Wobrock D. Schell R. Maser W. Jaeschke H. -W. Georgii W. Wieprecht B. G. Arends J. J. Mols G. P. A. Kos S. Fuzzi M. C. Facchini G. Orsi A. Berner I. Solly C. Kruisz I. B. Svenningsson A. Wiedensohler H. -C. Hansson J. A. Ogren K. J. Noone A. Hallberg S. Pahl T. Schneider P. Winkler W. Winiwarter R. N. Colvile T. W. Choularton A. I. Flossmann S. Borrmann 《Journal of Atmospheric Chemistry》1994,19(1-2):3-35
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Alexandrov GA 《Carbon balance and management》2011,6(1):1
The dominant model of journal evaluation emerged at the time when there were no open-access journals, and nobody has assessed
yet whether this model is able to cope with this modern reality. This commentary attempts to fill the gaps in the common understanding
of the role that 'impact factor' should play in evaluation of open-access journals. 相似文献