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11.
Celestial Mechanics and Dynamical Astronomy - On reprend ici l'étude du problème trapezoïdal des 4 corps, qui a été commencée par l'auteur dans [2]. En... 相似文献
12.
Ortega Ernesto Braunstein Alfredo Lage-Castellanos Alejandro 《Stochastic Environmental Research and Risk Assessment (SERRA)》2020,34(3):493-511
Stochastic Environmental Research and Risk Assessment - We present a Bayesian approach for the Contamination Source Detection problem in water distribution networks. Assuming that contamination is... 相似文献
13.
A criterion is proposed for making decisions regarding the optimal location of a given number of sensors to record the seismic response of a structure for identification purposes. The optimal location of the sensors is selected so that the expected value of a Bayesian loss function, expressed in terms of the Fisher information in the recordings, is minimized. The criterion is applied to the case of multi-degree-of-freedom systems with uncertain structural properties subjected to earthquake ground motions modelled as stationary stochastic processes. The use and capabilities of the criterion are thoroughly illustrated by means of an example. Results are used to assess the influence of record duration, recording noise, and ground motion frequency content and amplitude, on the optimal location of accelerometers as well as on the reduction of prior uncertainty about the structural parameters. © 1998 John Wiley & Sons, Ltd. 相似文献
14.
Maria Lacalamita Ernesto Mesto Fernando Scordari Emanuela Schingaro 《Physics and Chemistry of Minerals》2012,39(8):601-611
In the present work, crystal chemical variations between 1M and 2M 1 phlogopites coexisting in the same rock sample from kamafugite of Kasenyi (southwest Uganda, west branch of the East African Rift) were explored by electron probe microanalyses, single crystal X-ray diffraction and M?ssbauer spectroscopy. Chemical analyses revealed close similarity both within and between the two polytypic arrangements as well as high TiO2 (~4.9?wt%) and Al2O3 (~12.9?wt%), and low Cr2O3 (~0.8?wt%), F (~0.3?wt%) and BaO (~0.2?wt%) contents. Room temperature 57Fe M?ssbauer investigation proved that the studied mica is a tetraferriphlogopite with: IVFe3+?=?19(1)?%, VIFe2+?=?58(1)?%, VIFe3+?=?23(1)?%. Single crystal refinement showed that both polytypes have narrow range of variation in terms of some relevant unit cell parameters and similar values in terms of mean bond lengths, mean atomic numbers and distortion parameters. Similar substitutions were active in the structure of the 1M and 2M 1 studied phlogopites. However, in 2M 1 polytypes the oxy-type substitutions were found to occur to a greater extent. Comparison of unit layer of 1M mica (in the 2M 1 setting) with that of the 2M 1 ones showed that the 2M 1 polytypes are affected to different extent by relative shifts of the upper and lower triads of octahedral oxygens along the ±b directions. This effect did not cause any symmetry lowering in the T-O-T layer of the studied samples. 相似文献
15.
The Guará and Botucatu formations comprise an 80 to 120 m thick continental succession that crops out on the western portion of the Rio Grande do Sul State (Southernmost Brazil). The Guará Formation (Upper Jurassic) displays a well-defined facies shift along its outcrop belt. On its northern portion it is characterised by coarse-grained to conglomeratic sandstones with trough and planar cross-bedding, as well as low-angle lamination, which are interpreted to represent braided river deposits. Southwards these fluvial facies thin out and interfinger with fine- to medium-grained sandstones with large-scale cross-stratification and horizontal lamination, interpreted as eolian dune and eolian sand sheets deposits, respectively. The Botucatu Formation is characterised by large-scale cross-strata formed by successive climbing of eolian dunes, without interdune and/or fluvial accumulation (dry eolian system). The contact between the Guará and the Botucatu formations is delineated by a basin-wide deflation surface (supersurface). The abrupt change in the depositional conditions that took place across this supersurface suggests a major climate change, from semi-arid (Upper Jurassic) to hyper-arid (Lower Cretaceous) conditions. A rearrangement of the Paraná Basin depocenters is contemporaneous to this climate change, which seems to have changed from a more restrict accumulation area in the Guará Formation to a wider sedimentary context in the Botucatu Formation. 相似文献
16.
H. R. Merrett K. Kuijken M. R. Merrifield A. J. Romanowsky N. G. Douglas N. R. Napolitano M. Arnaboldi M. Capaccioli K. C. Freeman O. Gerhard N. W. Evans M. I. Wilkinson C. Halliday T. J. Bridges D. Carter 《Monthly notices of the Royal Astronomical Society》2003,346(4):L62-L66
We present a possible orbit for the Southern Stream of stars in M31, which connects it to the Northern Spur. Support for this model comes from the dynamics of planetary nebulae (PNe) in the disc of M31: analysis of a new sample of 2611 PNe obtained using the Planetary Nebula Spectrograph reveals ∼20 objects with kinematics inconsistent with the normal components of the galaxy, but which lie at the right positions and velocities to connect the two photometric features via this orbit. The satellite galaxy M32 is coincident with the stream both in position and velocity, adding weight to the hypothesis that the stream comprises its tidal debris. 相似文献
17.
The global positioning system (GPS) is used increasingly to control horizontal and vertical displacement of large civil constructions.
The displacements can occur over varius time scales. For example, in case of the loading test of a bridge, the time span between
measurements is on the order of 30 min. The achievable precision in the vertical component and its relation to residual multiplath
effects become critically important in such aaplications. A multipath-to-noise ratio (MNR) on individual satellites is introduced
to quantify the multipath effects. ? 2000 John Wiley & Sons, Inc. 相似文献
18.
Ernesto A. Lacomba Ernesto Pérez-Chavela 《Celestial Mechanics and Dynamical Astronomy》1992,54(4):343-355
We obtain a compact model for the global study of the planar rhomboidal 4-body problem in a level of constant negative energy. This model is a variation of the non compact model obtained through a McGehee blow up transformation. but compactness permits to obtain results which are not clear in the other case. 相似文献
19.
Abimael Bengochea Manuel Falconi Ernesto Pérez-Chavela 《Astrophysics and Space Science》2011,333(2):399-408
We present some families of horseshoe periodic orbits in the general planar three-body problem for the case of two equal masses.
The considered system is a symmetric version of the one formed by Saturn, Janus and Epimetheus. We use a mass ratio equal
to 35×10−5, corresponding to 105 times the Saturn-Janus mass parameter of the restricted case; for this mass ratio the satellites have a significantly bigger
influence on the planet than in the classical Saturn, Janus and Epimetheus system. To obtain periodic orbits, we search those
horseshoe orbits passing through two reversible configurations. A particular kind of periodic orbits where the minor bodies
follow the same path is discussed. 相似文献
20.
Alex Fore Ziad S. Haddad T. N. Krishnamurti Ernesto Rodgridez 《Pure and Applied Geophysics》2012,169(3):415-424
One of the current problems in the accurate estimation of over-ocean wind from scatterometry observations is the proper accounting
for precipitation. Specific cases such as hurricanes are particularly difficult, because precipitation in the eye wall and
rain bands can be quite heavy, and therefore, affect the scatterometer signatures so drastically that a category-4 hurricane
can appear, to the scatterometer, to have category-1 winds. We have developed an approach to infer and account for the signature
of the precipitation from non-simultaneous passive-microwave measurements of rain, with the help of geostationary IR measurements.
In this note, we describe the basic approach, and the results of applying it to the data taken by the Tropical Rainfall Measurement
Mission Microwave Imager measurements several hours before and after the QuikSCAT observation of Hurricane Rita in September
2005. We also describe how we are enhancing the approach with more realism in the assimilation of the IR information. 相似文献