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71.
Prof. Dr. M. Ewing Dipl.-Phys. S. Mueller M. Landisman Prof. Dr. Y. Satô 《Pure and Applied Geophysics》1959,44(1):83-118
Summary An electronic sound spectrograph has been used to analyze the transients in complicated earthquake and explosion signals. Transient analysis with a sound spectrograph gives a means for directly obtaining group velocity at each of the spectral frequencies for each of the separate arrival branches, for any type of transient signal. Compared to frequency analysis, it presents the fine spectral structure of the signal as it changes with time, not an average over a time that includes many parts of the seismic signal.Dispersion as well as the body wave spectrum of theP wave has been observed by transient analysis of seismic signals. Dispersion has also possibly been observed in theS wave, and in the various multiply reflectedS waves, which have been found to increase in period from one arrival to the next. The dispersed pattern of arrival of fundamental and higher mode surface waves has been observed for oceanic, continental, and mixed paths. Among these signals is a clear indication of the continental second shear mode. The separation of surface waves for the direct and complementary paths has also been accomplished. Our results compare well with those obtained by standard techniques.The dispersion of the fundamental and higher mode signals from explosive sources in shallow water may be easily studied by making sound spectrograms and amplitude sections of these seismic signals. These shallow water shots show bubble pulses and Airy phases, which are clearly defined on the spectrograms and sections.
With two plates: Figs. 6 & 17
Preliminary results presented at the 30th Annual Meeting of the Eastern Section of the Seismological Society of America, June 13–14, 1958, inSt. Louis, Missouri, U.S.A.-Lamont Geological Observatory Contribution No. 383. 相似文献
Zusammenfassung Ein elektronischer Schallspektrograph wurde benutzt, um die nichtstationären Vorgänge in komplizierten Erdbeben- und Explosionswellen zu analysieren. Die Analyse von nichtstationären Vorgängen mittels dieses Schallspektrographen ergibt unmittelbar die Gruppengeschwindigkeit jeder einzelnen Spektralfrequenz für die verschiedenen seismischen Wellenphasen, die ja solche nichtstationären Vorgänge darstellen. Verglichen mit einer gewöhnlichen Frequenzanalyse liefert diese Art von Analyse die Spektralfeinstruktur des zeitlich sich ändernden Signals und nicht ein Mittel über ein Zeitintervall, das einen grösseren Teil des seismischen Schwingungsablaufs umfasst.Sowohl Dispersionserscheinungen in derP-Welle als auch deren diskretes Amplitudenspektrum wurden mit Hilfe dieser Analyse seismischer Signale festgestellt. Dispersion wurde mit ziemlicher Wahrscheinlichkeit auch bei derS-Welle beobachtet, und in den verschiedenen mehrfachreflektiertenS-Wellen zeigt sich in aufeinanderfolgenden Reflexionen eine Periodenzunahme. Das disperse Erscheinungsbild der Oberflächenwellen in ihrer Grundschwingungstype und den zugehörigen Schwingungstypen höherer Ordnung wurde für ozeanischen, kontinentalen und gemischten Weg aufgenommen. Unter diesen Wellentypen findet sich eine klare Andeutung der kontinentalen Scherschwingungsform zweiter Ordnung vom Rayleigh-Typus (Second Shear Mode). Die Aufspaltung von Oberflächenwellen für direkten und antipodalen Weg wurde ebenfalls erreicht. Unsere Ergebnisse zeigen eine gute Übereinstimmung mit den von herkömmlichen Methoden stammenden Resultaten.Die Dispersion von Wellentypen erster und höherer Ordnung, die durch Explosionen im Seichtwasser angeregt werden, kann leicht an Hand der Schallspektrogramme und momentanen Amplitudenspektren ihrer seismischen Signale untersucht werden. Solche Seichtwasserdetonationen zeigen Pulsationen und Airy-Phasen, die sich eindeutig auf den Spektrogrammen und Amplitudenbildern abzeichnen.
With two plates: Figs. 6 & 17
Preliminary results presented at the 30th Annual Meeting of the Eastern Section of the Seismological Society of America, June 13–14, 1958, inSt. Louis, Missouri, U.S.A.-Lamont Geological Observatory Contribution No. 383. 相似文献
72.
This paper explores the influence of Walter Isard, his work, and the field of regional science generally on transportation geography. It argues that Isards impact was both subtle and significant. Regional science greatly influenced the emergence of modern transportation geography in the 1950s. Transportation themes and methods from Isards own work provided early building blocks for transportation geography. Moreover, Isard and regional science contributed importantly to the development of the intellectual network of persons, places, and institutions that early on defined the subfield. Regional science and transportation geography have diverged in recent decades, but opportunities exist for renewed interaction.The author thanks Doug Fleming and Dick Morrill for comments on an earlier version of this paper. 相似文献
73.
Eastward-propagating patterns in anomalous potential temperature and salinity of the Southern Ocean are analyzed in the output of a 1000-year simulation of the global coupled atmosphere–ocean GCM ECHO-G. Such features can be associated with the so-called Antarctic Circumpolar Wave (ACW). It is found that time–longitude diagrams that have traditionally been used to aid the visualization of the ACW are strongly influenced by the width of the bandpass time filtering. This is due to the masking of considerable low-frequency variability that occurs over a broad range of time scales. Frequency–wavenumber analysis of the ACW shows that the eastward-propagating waves do have preferred spectral peaks, but that both the period and wavenumber change erratically when comparing different centuries throughout the simulation. The variability of the ACW on a variety of time scales from interannual to centennial suggests that the waiting time for a sufficient observational record to determine the time scale of variability of the real world ACW (and the associated decadal time scale predictability of climate for southern landmasses) will be a very long one.Responsible Editor: Dirk Olbers 相似文献
74.
The nitrogen and carbon stable isotope ratios (δ15N and δ13C) of the pygmy mussel,Xenostrobus securis, were determined for three estuaries with varying levels of catchment disturbance in northern New South Wales, Australia.
The lower Manning River catchment supported the highest human population densities with 3% residential development and some
livestock agriculture (41%); the Wallamba River catchment was mostly livestock agriculture (56%) while the Wallingat River
catchment was mostly vegetated (79%). Mussels, estuarine particulate organic matter (POM), and livestock and human-derived
waste were collected in two stages during the austral summers of 2001–2002 and 2002–2003 for dual carbon-nitrogen stable isotope
analysis. The disturbed Manning and Wallamba River catchment mussels were enriched in15N by an average of 3.2‰ and 1.5‰, respectively, compared to the vegetated Wallingat River mussels. Mussel δ13C values ranged from −24.8‰ to −30.3‰ and showed an estuarine gradient becoming enriched with distance downstream within estuaries,
but were unable to distinguish patterns in catchment disturbance between estuaries. The δ15N and δ13C values of POM showed a similar pattern to mussels, indicating a direct link between them within each estuary. A multiple
regression model of mussel δ15N using the fractions of land used for livestock agriculture and residential development within 5 km zones from river networks
to a distance equivalent to a tidal ellipse from sites explained 67% of the variation in mussel δ15N with 95% of the differences lying within 1.6‰ of observed values. Increasing fractions of land used for livestock agriculture
depleted mussel δ15N values estimated by the regression equation, indicating the use of cow manure as a nutrient source with a value of 2.0‰.
Increasing fractions of land used for residential development enriched estimated mussel δ15N, indicating the use of human-derived waste with a value of 20.8‰. Pygmy mussels are a useful long-term bio-indicator for
the effects of anthropogenic catchment disturbance and nutrient enrichment in estuaries. 相似文献
75.
Criteria used to identify Fe2+-Fe3+ and Fe2+-Ti4+ intervalence charge transfer absorption bands in electronic spectra are reviewed and compared to the characteristics of unperturbed Fe2+ crystal field bands and those that are intensified by interaction with Fe3+. Band energy is the least definitive diagnostic criterion. Changes in band intensity with temperature are also of limited value. Large widths are the most reliable characteristic of charge transfer bands. New optical absorption spectra are presented for euclase, as well as 80 K spectra of rockbridgeite, babingtonite and lazulite. Comparison of optical spectra to magnetic susceptibility measurements for rockbridgeite and babingtonite provides support for recent theories regarding the effect of magnetic coupling on the variation of charge transfer intensity with temperature. 相似文献
76.
We develop an ELLAM-MFEM approximation to the strongly coupled systems of time-dependent nonlinear partial differential equations (PDEs) and constraining equations, which describe fully miscible, highly compressible, multicomponent flows through heterogeneous and compressible porous media with singular sources and sinks. An Eulerian–Lagrangian localized adjoint method (ELLAM) is presented to solve the transport equations for concentrations. A mixed finite element method (MFEM) is used to solve the pressure PDE for the pressure and Darcy velocity simultaneously, which generates accurate fluid velocities and minimizes the numerical difficulties occurring in standard methods caused by differentiation of the pressure and then multiplication by rough coefficients. The ELLAM-MFEM solution technique symmetrizes and stabilizes the governing transport PDEs and greatly reduces nonphysical oscillation and/or excessive numerical dispersion present in many large-scale simulators. Computational experiments show that the ELLAM-MFEM solution technique can generate stable and physically reasonable numerical simulations even if coarse spatial grids and very large time steps are used. 相似文献
77.
Stephanie Pincetl 《Urban geography》2018,39(9):1431-1434
I argue that the tension between cities and nation states go through the countryside, or rural areas, at least in the U.S. Further, cities are decidedly constrained in their abilities to effectuate many of the changes associated with them: addressing climate change, economic inequality and more. What is missing is the way in which rural alienation from economic prosperity plays out politically. 相似文献
78.
John D. Monnier Stefan Kraus Michael J. Ireland Fabien Baron Amelia Bayo Jean-Philippe Berger Michelle Creech-Eakman Ruobing Dong Gaspard Duchêne Catherine Espaillat Chris Haniff Sebastian Hönig Andrea Isella Attila Juhasz Lucas Labadie Sylvestre Lacour Stephanie Leifer Antoine Merand Ernest Michael Stefano Minardi Christoph Mordasini David Mozurkewich Johan Olofsson Claudia Paladini Romain Petrov Jörg-Uwe Pott Stephen Ridgway Stephen Rinehart Keivan Stassun Jean Surdej Theo ten Brummelaar Neal Turner Peter Tuthill Kerry Vahala Gerard van Belle Gautam Vasisht Ed Wishnow John Young Zhaohuan Zhu 《Experimental Astronomy》2018,46(3):517-529
The Planet Formation Imager (PFI, www.planetformationimager.org) is a next-generation infrared interferometer array with the primary goal of imaging the active phases of planet formation in nearby star forming regions. PFI will be sensitive to warm dust emission using mid-infrared capabilities made possible by precise fringe tracking in the near-infrared. An L/M band combiner will be especially sensitive to thermal emission from young exoplanets (and their disks) with a high spectral resolution mode to probe the kinematics of CO and H2O gas. In this paper, we give an overview of the main science goals of PFI, define a baseline PFI architecture that can achieve those goals, point at remaining technical challenges, and suggest activities today that will help make the Planet Formation Imager facility a reality. 相似文献
79.
80.