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41.
Eberhard Grün Ralf Srama Nicolas Altobelli Kathrin Altwegg James Carpenter Luigi Colangeli Karl-Heinz Glassmeier Stefan Helfert Hartmut Henkel Mihaly Horanyi Annette Jäckel Sascha Kempf Markus Landgraf Neil McBride Georg Moragas-Klostermeyer Pasquale Palumbo Han Scholten Andre Srowig Zoltan Sternovsky Xavier Vo 《Experimental Astronomy》2009,23(3):981-999
The DuneXpress observatory will characterize interstellar and interplanetary dust in-situ, in order to provide crucial information
not achievable with remote sensing astronomical methods. Galactic interstellar dust constitutes the solid phase of matter
from which stars and planetary systems form. Interplanetary dust, from comets and asteroids, represents remnant material from
bodies at different stages of early solar system evolution. Thus, studies of interstellar and interplanetary dust with DuneXpress
in Earth orbit will provide a comparison between the composition of the interstellar medium and primitive planetary objects.
Hence DuneXpress will provide insights into the physical conditions during planetary system formation. This comparison of
interstellar and interplanetary dust addresses directly themes of highest priority in astrophysics and solar system science,
which are described in ESA’s Cosmic Vision. The discoveries of interstellar dust in the outer and inner solar system during
the last decade suggest an innovative approach to the characterization of cosmic dust. DuneXpress establishes the next logical
step beyond NASA’s Stardust mission, with four major advancements in cosmic dust research: (1) analysis of the elemental and
isotopic composition of individual interstellar grains passing through the solar system, (2) determination of the size distribution
of interstellar dust at 1 AU from 10 − 14 to 10 − 9 g, (3) characterization of the interstellar dust flow through the planetary system, (4) establish the interrelation of interplanetary
dust with comets and asteroids. Additionally, in supporting the dust science objectives, DuneXpress will characterize dust
charging in the solar wind and in the Earth’s magnetotail. The science payload consists of two dust telescopes of a total
of 0.1 m2 sensitive area, three dust cameras totaling 0.4 m2 sensitive area, and a nano-dust detector. The dust telescopes measure high-resolution mass spectra of both positive and negative
ions released upon impact of dust particles. The dust cameras employ different detection methods and are optimized for (1)
large area impact detection and trajectory analysis of submicron sized and larger dust grains, (2) the determination of physical
properties, such as flux, mass, speed, and electrical charge. A nano-dust detector searches for nanometer-sized dust particles
in interplanetary space. A plasma monitor supports the dust charge measurements, thereby, providing additional information
on the dust particles. About 1,000 grains are expected to be recorded by this payload every year, with 20% of these grains
providing elemental composition. During the mission submicron to micron-sized interstellar grains are expected to be recorded
in statistically significant numbers. DuneXpress will open a new window to dusty universe that will provide unprecedented
information on cosmic dust and on the objects from which it is derived. 相似文献
42.
Thi Thao Dinh To Quyen Nguyen Gia Co Quan Vo Dong Nghi Nguyen Hon Quoc Tran Tien Khoa Le 《International Journal of Environmental Science and Technology》2017,14(12):2613-2622
Magnetic photo-Fenton catalysts based on spinel CuFe2O4 were successfully prepared by the starch-assisted sol–gel method. Various synthetic conditions such as annealing temperatures (700, 800 and 900 °C) and molar ratios of Cu2+/Fe3+/C6H10O5 in the precursor solution (from 1:2:2 to 1:2:4) were, respectively, used in order to study the influences of annealing temperatures and precursor starch contents on the magnetic and catalytic properties of CuFe2O4 powders. The photo-Fenton catalytic activity was evaluated via the degradation of methylene blue under ultraviolet and visible irradiation with H2C2O4 as a new oxidizing agent. According to the results, when the annealing temperature increased to 800 °C, the spinel CuFe2O4 phase amount was increased, which strongly enhances the photo-Fenton catalytic performance. However, above 800 °C, the catalytic activity was reduced, due to the increase in particle size. The starch content also affected the surface Cu2+ content and the particle size of catalysts. The catalyst prepared at 800 °C with the molar Cu2+/Fe3+/C6H10O5 ratio of 1:2:3 presented the best photo-Fenton performance, owing to its highest surface Cu2+ content. This catalyst also exhibits ferromagnetic properties (saturation magnetization of 25.836 emu/g and coercivity of 1010.23 Oe), which allows them to be easily separated from the solution by a magnet. 相似文献
43.
To date, the interpretation of the self-potential anomalies, caused by the polarized spherical ore bodies, has usually been carried out based on the special graph along the profile passing through the extremes of these anomalies. This special graph could be identified only if we have at hand a map of self-potential distribution for which many profiles should be measured needing many man powers and time. To overcome this situation, in actual paper a new method of interpretation for the above mentioned self-potential anomalies is proposed for which sufficiency is provided by only two self-potential graphs along two parallel ordinary profiles oriented fortuitously.The theoretical basis of this new method of interpretation, together with several nomograms making comfortably its use as well as some testing results, were given.Until May 1986, Inst. of Hydrogeology and Eng. Geology, Warsaw University, 02-089 Warsaw, Poland. 相似文献
44.
The length variations and the ultrasonic wave velocities were measured along principal single crystal calcite axes under high pressure.We have observed that six independent elastic constants undergo drastic changes at the calcite I—calcite II transition point at 14.6 kbar. Furthermore, we have determinated the length and volumetric variations in the phases I and II and during the I–II transition.These results allow us to deduce the following important points: influence of the planar CO3 groups on the strong linear compressibility anisotropy in phase I; reciprocal relation between the decrease of elastic constants at the transition point and the anomaly of compressibility of the calcite II; compatibility of our data with the monoclinic structure of calcite II. 相似文献
45.
Dr. C. Voûte 《International Journal of Earth Sciences》1963,52(2):665-675
In connection with the UNESCO-activity to save the Nubian Monuments several geological and geotechnical problems arising are discussed. Geomorphology, regional geology, capillarity-questions and salt-action are considered and ways of saving the Philae-Monuments are sketched.
Zusammenfassung Im Zusammenhang mit der UNESCO-Aktion zur Rettung der Nubischen Denkmäler werden verschiedene geologische und geotechnische Probleme dieses Unternehmens beschrieben. Regional-geologische und geomorphologische Fragen, Kapillaritäts- und Salzverwitterungs-Probleme werden angeschnitten und diskutiert. Zum Schluß werden Maßnahmen zur Rettung der Philae-Tempel skizziert.
Résumé En regard de l'action de l'UNESCO pour le sauvetage des monuments de la Nubie, l'auteur décrit les différents problèmes géologiques et géotechniques relatifs à cette entreprise. Des questions à caractère géologique régional et géomorphologique, des problèmes d'altération par capillarité et à l'intervention de sels sont examinés et discutés. Finalement l'auteur esquisse les mesures à prendre pour la sauvegarde du temple de Philae.
UNESCO .相似文献
46.
J. Hakkila V. Vo C. Meegan J. Horack G. Fishman D. Hartmann G. Pendleton M. Briggs W. Paciesas 《Astrophysics and Space Science》1995,231(1-2):23-26
A repeater statistic (derived from the two-point angular correlation function and accounting for location errors) is used to identify constraints on the rate of burst repetition from the BATSE 1B catalog. Because of the anisotropic sky exposure, repeating sources should create additional effects in the large-scale distribution of close burst pairs.National Research Council Fellow at NASA/MSFC 相似文献
47.
48.
K. Kh. Truong T. S. Vo Yu. M. Mikhailov A. L. Kharitonov O. V. Kapustina 《Geomagnetism and Aeronomy》2010,50(5):690-694
The preliminary results of observations of VLF electromagnetic signals (atmospherics) in the mountains of North Vietnam (Dien
Bien Phu, 21°23′50″ N, 103°0′28″ E) are presented. Primarily, signals of typical atmospherics with a maximum in the frequency
range of 4–9 kHz were observed; sometimes they were accompanied by so-called “tails” at frequencies less than 1 kHz, and also
tweeks of usually short duration (about 10 ms) were observed. Several parameters of the ionosphere, as well as the distance
to sources of atmospherics (in accordance to the data of the World Wide Lightning Location Network (TOGA)), were estimated
by spectral-temporal characteristics of tweeks. 相似文献
49.
An energy approach is proposed as a complement to the stress approach commonly considered for investigating soil desiccation cracking. The elastic strain energies before and after crack initiation are estimated by both numerical and analytical solutions. The energy released by cracking is then compared with the fracture energy to discuss crack initiation conditions. This leads to combined energy and stress conditions for crack initiation following Leguillon's theory. An approximate analytical solution is derived from a variational formulation of the porous elastic body equations. A cohesive zone model and finite element code are used to simulate crack propagation in an unsaturated porous body. This analysis shows that the energy criterion is reached before the stress criterion, and this can explain unstable crack propagation at the beginning. The approximate analytical solution allows predicting correctly the crack depth and opening in its initiation stage. 相似文献
50.
Overhangs are frequently observed in riverbanks, coastal headlands, and rock formations. The geometry of an overhang is an input into most slope stability analyses and is often idealised or back-calculated from empirical data. This study investigates the geometries of overhang slopes, which exist while in limiting conditions satisfying static equilibrium with soil strength governed by the Mohr-Coulomb failure criterion. The overhanging contour is formulated as the unknown in a boundary value problem and solved for using the slip line theory. Analyses consider nonhomogeneous soils, where cohesion and, if unsaturated, the contribution of suction to the effective stress vary linearly with depth. The solutions are presented in general dimensionless charts. Applications of the charts are illustrated via examples. It has been observed that soil with varying amounts of friction and cohesion could develop overhanging arches of different sizes and shapes. This study shows that the curvature of an overhang becomes more pronounced for small values of φ′ . It is also demonstrated that changing the contribution of suction to the effective stress has a direct impact on the size of an unsaturated soil overhang. Overhanging slope shapes observed in reality may be different from the idealised subset studied in this paper since real slopes are not necessarily at impending failure. The real shapes may be influenced by various physical processes such as weathering, stress variations caused by cycles of wetting-drying. Even so, the results presented in the paper indicated how key soil properties influence slope shapes, albeit it while in limiting conditions. 相似文献