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51.
C. E. Konrad 《Theoretical and Applied Climatology》1998,60(1-4):11-19
Summary Previous work has examined relationships between the planetary scale Pacific North American (PNA) teleconnection pattern
and regional scale mean temperature over portions of the United States, but analyses have been restricted to monthly values
of these two variables. It is not clear if this is the most appropriate scale for relating PNA patterns to temperature. In
this study, PNA indices are related to various aspects of temperature over a range of time scales spanning one month. To carry
this out, standardized PNA indices are calculated for 6 time intervals ranging from 5 to 30 days over a period of 27 winter
seasons. Standardized regional scale temperature anomalies are assessed over various regions of the United States and used
to compute mean, maximum, and minimum temperature anomalies over the same 6 time intervals. Correlation matrices are then
constructed to provide relationship characteristics between the PNA indices and temperature measures within the intramonthly
time scale.
Only the southeastern and northwestern regions of the United States display significant relationships between the PNA indices
and temperature. Over the Southeast, temperature anomalies on short time scales relate most strongly to PNA indices computed
over time intervals of 25 to 30 days; this is especially the case for the minimum temperature anomaly. The strongest relationships,
however, are observed between the PNA index and temperature anomalies computed on a 20–25 day time interval. Over the Northwest,
the relationships are not as strong and somewhat more varied. Most notably, moderate connections are found between the 30
day PNA index and minimum temperature anomalies computed over a 25 day period.
Received August 18, 1997Revised November 28, 1997 相似文献
52.
A Servohydraulically-controlled Deformation Apparatus for Rock Deformation under Conditions of Ultra-high Pressure Metamorphism 总被引:5,自引:0,他引:5
E. Rybacki J. Renner K. Konrad W. Harbott F. Rummel B. Stöckhert 《Pure and Applied Geophysics》1998,152(3):579-606
—A deformation apparatus has been developed to study the mechanical behaviour of high pressure and ultra-high pressure metamorphic rocks. It is based on the conventional Griggs design and the molten salt cell concept introduced by H. E. Green II. Both, the axial loading and the confining pressure are servohydraulically controlled. Alternatively, a self-made multilayer pressure vessel or a commercial stripwound construction are used. The pressure cell is improved with respect to systems described previously by the use of different salt mixtures with low eutectic temperatures, by a mechanically stable arrangement of the thermocouples, and by an optimization of the frictional characteristics of the axial loading system. The apparatus has been successfully used in deformation experiments on cylindrical aragonite and coesite samples 3 to 4 mm in diameter and 6 to 10 mm in length at confining pressures up to 3.7 GPa and temperatures up to 1170°C. 相似文献
53.
Michael R. Merrifield & Konrad Kuijken 《Monthly notices of the Royal Astronomical Society》1998,297(4):1292-1296
We show that the kinematics of the shells seen around some elliptical galaxies provide a new, independent means for measuring the gravitational potentials of elliptical galaxies out to large radii. A numerical simulation of a set of shells formed in the merger between an elliptical and a smaller galaxy reveals that the shells have a characteristic observable kinematic structure, with the maximum line-of-sight velocity increasing linearly as one moves inward from a shell edge. A simple analytic calculation shows that this structure provides a direct measure of the gradient of the gravitational potential at the shell radius. In order to extract this information from attainable data, we have also derived a complete distribution of line-of-sight velocities for material within a shell; comparing the observed spectra of a shell to a stellar template convolved with this distribution will enable us to measure the gradient of the potential at this radius. Repeating the analysis for a whole series of nested shells in a galaxy allows the complete form of the gravitational potential as a function of radius to be mapped out. The requisite observations lie within reach of the up-coming generation of large telescopes. 相似文献
54.
55.
Merril Eisenbud Konrad Krauskopf Eduardo Penna Franca Wayne Lei Robert Ballad Paul Linsalata Kenkichi Fujimori 《Environmental Geology》1984,6(1):1-9
A highly weathered deposit of thorium and rare earth elements located near the summit of a hill in the state of Minas Gerais,
Brazil, is being studied as an analogue for a radioactive waste repository that sometime in the distant future may be eroded
to the surface or intruded by groundwater Thorium serves as an analogue for Pu4+, and La3+ as an analogue for Cm3+ and Am3+ The mobilization rate constants of the analogue elements by groundwater are so slow (of the order of 10−9 per year) as to suggest that essentially complete radioactive decay of the transuranic actinides would occur in place even
under the relatively unfavorable conditions that exist at a site such as this 相似文献
56.
Sebastian F. Hönig Almudena Alonso Herrero Poshak Gandhi Makoto Kishimoto Jörg-Uwe Pott Cristina Ramos Almeida Jean Surdej Konrad R. W. Tristram 《Experimental Astronomy》2018,46(3):413-419
Infrared (IR) interferometry has made widely recognised contributions to the way we look at the dusty environment of supermassive black holes on parsec scales. It finally provided direct evidence for orientation-dependent unification of active galaxies, however it also showed that the classical “torus” picture is oversimplified. New scientific opportunities for AGN have been suggested, and will soon be carried out, focusing on the dynamical aspects of spectrally and spatially resolved interferometry, as well as the potential to employ interferometry for cosmology. This will open interferometry to new scientific communities. 相似文献
57.
Greater sage-grouse (Centrocercus urophasianus) are threatened by loss of sagebrush habitat and the spread of West Nile virus throughout much of their range in North America;
yet, future impacts of climate change on these potential stressors have not been addressed. Here, we aim to quantify the potential
impacts of climate change on the distribution of climatically suitable habitat for sagebrush and on transmission risk for
West Nile virus in the eastern portion of the species’ range. We used Maxent to model the current and future climatically
suitable habitat for two dominant sagebrush species in the study area, and we used a degree-day model to predict future West
Nile virus transmission risk under likely climate-change scenarios. Our models suggest that areas with the highest future
suitability for sagebrush habitat will be found in southwestern Wyoming and north-central Montana. The degree-day model suggests
that greater sage-grouse in western portions of the study area, which are generally higher in elevation than where West Nile
virus currently occurs, will see increasing risk of transmission in the future. We developed a spatially explicit map of suggested
management actions based on our predictions that will aid in conservation of the species into the coming decades. 相似文献
58.
59.
This work is intended to investigate the influence of temperature-dependent metamorphism of ice on the shape of small depressions in the surface of cometary nuclei. We are mainly interested in the role of initial cohesivity of a nucleus. For this purpose we simulate sublimation of ice from the facets of initially cylindrical depressions in ice of different initial structure. The simulations account for the diurnal and orbital changes of insolation and its dependence on the current shape of the depressions. Our model includes heat transport in the cometary material and metamorphism of ice. We present the results obtained for the nucleus of the Comet 67P/Churyumov-Gerasimenko, target of the ESA cornerstone mission Rosetta. 相似文献
60.
The comet 67P/Churyumov-Gerasimenko is the current target of the mission Rosetta, initially planned to investigate comet 46P/Wirtanen. These two comets have similar orbits, except the distance to the Sun at perihelion, but different orbital histories and different masses. Thus, structures of the nuclei can be significantly different. The evolution of comet Wirtanen was simulated by several authors, while comet Churyumov-Gerasimenko became an object of high interest only recently and is not well investigated. In the present work we simulate the evolution of the nucleus, down to tens of meters below the surface, using an extended version of the model previously applied for comet Wirtanen [Kossacki et al., 1999. Comet 46P/Wirtanen: evolution of the subsurface layer. Icarus 142, 202-218.]. The model includes strengthening of the nucleus due to sintering of the ice grains. Simulations are performed for different latitudes, accounting for the evolution of the orbit and for changes of the nucleus orientation, as well as diurnal and seasonal changes of insolation. The calculated loss of water vapor from the comet is integrated over the nucleus surface and is compared with the observational data. We have found, that the sublimation through the dust mantle can be large enough to reproduce the profile of the total water production as a function of time from perihelion. The required dependence of thickness of the dust layer on latitude qualitatively matches present distribution of the absorbed solar flux. The non-gravitational acceleration in the comet motion together with the simulated sublimation flux are used in order to estimate the mass and the bulk density of the nucleus. 相似文献