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171.
u uuuuaumau uu u m, ¶rt;u a mumau nmu a u nmu mau u nmmu. au n¶rt; nuau ¶rt;mam u u m. nua m¶rt; m u m¶rt;a aau (1960) ¶rt; uu . 相似文献
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175.
Summary A simple two-layer model of finite-amplitude frontal waves was derived. During the development of the unstable waves the cusp point is formed on the front. On the relatively steep (very flat) frontal planes very short (relatively long) amplified waves are to be expected. 相似文献
176.
The linear magnetoconvection in the rotating uniformly as well as non-uniformly stratified horizontal layer with azimuthal magnetic field is investigated for the various mechanical and electrical boundary conditions and especially, for various values of Roberts number. The developed diffusive perturbations (modes) are strongly influenced not only by the mentioned properties of boundaries but also by complicated coupling of viscous, thermal and magnetic diffusive processes. The mean electromotive force produced by developed hydromagnetic instabilities is also investigated to determine the hydromagnetic processes which are appropriate for -effect. The presented paper is an unification of hitherto published results of the authors and gives a short survey of many developments of corresponding model by Soward (1979). 相似文献
177.
Climate Change Impacts and Adaptation Strategies in Spring Barley Production in the Czech Republic 总被引:1,自引:0,他引:1
The crop model CERES-Barley was used to assess the impacts of increased concentration of atmospheric CO2 on growth and development of the most important spring cereal in Central and Western Europe, i.e., spring barley, and to examine possible adaptation strategies. Three experimental regions were selected to compare the climate change impacts in various climatic and pedological conditions. The analysis was based on multi-year crop model simulations run with daily weather series obtained by stochastic weather generator and included two yield levels: stressed yields and potential yields. Four climate change scenarios based on global climate models and representing 2 × CO2 climate were applied. Results: (i) The crop model is suitable for use in the given environment, e.g., the coefficient of determination between the simulated and experimental yields equals 0.88. (ii) The indirect effect related to changed weather conditions is mostly negative. Its magnitude ranges from ?19% to +5% for the four scenarios applied at the three regions. (iii) The magnitude of the direct effect of doubled CO2 on the stressed yields for the three test sites is 35–55% in the present climate and 25–65% in the 2 × CO2 climates. (iv) The stressed yields would increase in 2 × CO2 conditions by 13–52% when both direct and indirect effects were considered. (v) The impacts of doubled CO2 on potential yields are more uniform throughout the localities in comparison with the stressed yields. The magnitude of the indirect and direct effects ranges from ?1 to ?9% and from +31 to +33%, respectively. Superposition of both effects results in 19–30% increase of the potential yields. (vi) Application of the earlier planting date (up to 60 days) would result in 15–22% increase of the yields in 2 × CO2 conditions. (vii) Use of a cultivar with longer vegetation duration would bring 1.5% yield increase per one extra day of the vegetation season. (viii) The initial water content in the soil water profile proved to be one of the key elements determining the spring barley yield. It causes the yields to increase by 54–101 kg.ha?1 per 1% increase of the available soil water content on the sowing day. 相似文献
178.
The complicated structural and rheologic properties of Western Carpathian lithosphere reflect the complex geodynamic history of the Carpathian orogen. Based on critical analysis of earlier models, new interpolation of existing geophysical data and results of integrated modelling, a new map of the lithosphere thickness for the Carpathian–Pannonian region has been constructed. The map allows for the distinction of a frontal orogen collision zone in the NE (from increased lithosphere thickness) as well as a zone of oblique collision with the Bohemian Massif in the West, where lithosphere is not significantly thickened. The MOHO discontinuity beneath the Western Carpathian hinterland (Danube and East Slovak Basins), as defined by deep reflection seismic profiling, is relatively shallow. This probably reflects recent crustal extension related to oblique collision between the European plate and the ALCAPA block and an increase of the asthenospheric updoming from the Middle Miocene onward.Crustal thickness reflects the combined effects of deep-seated orogenic processes and mantle thermal evolution beneath the Pannonian Basin system. In this study, we focus particularly the structures of: (1) the Late Alpine collision and Neogene back arc basin development, including deep-seated contacts between colliding plates, a zone of slab detachment, the compressional accretionary wedge of the Outer Western Carpathian Flysch Belt, and extensional structures produced by subduction rollback and asthenosphere upwelling; (2) Early Alpine structures related to Cretaceous thrust-stacking, including subhorizontal reflection packages (interpreted as multi-generational extensional structures), the underplated intra-Penninic (Oravic) continental ribbon, and ophiolite traces of the Meliatic oceanic suture; and (3) north-dipping reflectors interpreted as remnant Hercynian lithotectonic fragments with opposed vergency to the subducted Alpine units. 相似文献
179.
P. Špaček Z. Sýkorová J. Pazdírková J. Švancara J. Havíř 《Studia Geophysica et Geodaetica》2006,50(2):233-258
The Variscan Bohemian Massif is disrupted by the NW-SE striking Elbe Fault System in its northern part. The increased tectonic
activity associated with this structure is manifested by increased seismicity in the eastern part of the Sudetes. With the
use of a temporary local seismic network, the total number of micro-earthquakes located in this region increased to 153 for
the period 1996–2003. The local magnitudes vary between −0.6 and 1.8 and the seismic energy was often released in swarm-like
sequences. Five seismic events with well-defined P-onset polarities at five or six stations enabled the estimation of focal
mechanisms. The present-day activity of the WNW-ESE to NNW-SSE fault systems is discussed on the basis of source mechanisms,
the alignment of the epicentres, as well as morphological and geological evidence. The majority of the recent seismic activity
is concentrated in a 40–60 km wide zone of a generally NW-SE trend. This structure represents a regional zone of weakness
within the SE termination of the Elbe Fault System, defined by a mesh of interconnected faults, of which many are deep-seated
and highly permeable and some are associated with light to moderate historical earthquakes. Both in the areas due south and
due north of this zone the present-day seismic activity is very low. The increased tectonic activity can be interpreted as
a result of the abundance of suitably oriented faults and their interconnection into major fault systems, the proximity of
the Outer Carpathian indentor and the Cainozoic volcanic and associated recent post-volcanic activity. The similar character
of swarms and their coincidence with the post-volcanic activity in the southeastern part of the Elbe Fault System and in some
focal zones of the western Bohemian seismically active area suggests that overpressurized fluids may represent a potential
swarm-triggering mechanism. 相似文献
180.
Comparative studies of short-term ionospheric variability in the F region ionosphere during rapid sequence sounding campaign
“HIRAC/SolarMax” (23–29 April 2001) are presented. The ionospheric short-term fluctuations have been studied in detail using
measurements from vertical sounding at Ebro (40.8 °N, 0.5 ° E) and Průhonice (49.9 °N, 14.5 °E) in the period range from 15
minutes to 2 hours. The electron density measurements contain variations that indicate the possible presence of propagating
gravity waves. Regular wave-like bursts were found during quiet days at both stations in electron concentration in F region,
with an increase of the oscillation activity after sunrise and then during late afternoon, and at sunset and after sunset.
Solar Terminator is assumed to be one of the sources of the regular wave bursts detected in the ionosphere during campaign
HIRAC. As expected, substantial intensification in longer period gravity waves was found to occur during the disturbed period
on April 28. Particular enhancement of the wave-like activity during disturbed day is discussed, being significant evidences
of a change of the wave-like activity pattern at a height around 200 km. 相似文献