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991.
A model was developed for pollutant dispersion from a point source simulating the Hadera (Israel) power plant stack. The model is based on the NCAR mesoscale meteorological MM4 model that provides the wind fields and coefficients of turbulent diffusion. The model was implemented using an implicit numerical scheme with changing directions. A comparison between the model calculations and an analytical solution for the advection-diffusion equation shows good agreement. Relatively low numerical diffusion of the adopted advection scheme was noted. Results for the hilly region of central Israel are presented for a summer case. 相似文献
992.
Impacts of shortwave radiation forcing on ENSO: a study with a coupled tropical ocean-atmosphere model 总被引:2,自引:0,他引:2
We describe a coupled tropical ocean-atmosphere model that represents a new class of models that fill the gap between anomaly
coupled models and fully coupled general circulation models. Both the atmosphere and ocean are described by two and half layer
primitive equation models, which emphasize the physical processes in the oceanic mixed layer and atmospheric boundary layer.
Ocean and atmosphere are coupled through both momentum and heat flux exchanges without explicit flux correction. The coupled
model, driven by solar radiation, reproduces a realistic annual cycle and El Nino-Southern Oscillation (ENSO). In the presence
of annual mean shortwave radiation forcing, the model exhibits an intrinsic mode of ENSO. The oscillation period depends on
the mean forcing that determines the coupled mean state. A perpetual April (October) mean forcing prolongs (shortens) the
oscillation period through weakening (enhancing) the mean upwelling and mean vertical temperature gradients. The annual cycle
of the solar forcing is shown to have fundamental impacts on the behavior of ENSO cycles through establishing a coupled annual
cycle that interacts with the ENSO mode. Due to the annual cycle solar forcing, the single spectral peak of the intrinsic
ENSO mode becomes a double peak with a quasi-biennial and a low-frequency (4–5 years) component; the evolution of ENSO becomes
phase-locked to the annual cycle; and the amplitude and frequency of ENSO become variable on an interdecadal time scale due
to interactions of the mean state and the two ENSO components. The western Pacific monsoon (the annual shortwave radiation
forcing in the western Pacific) is primarily responsible for the generation of the two ENSO components. The annual march of
the eastern Pacific ITCZ tends to lock ENSO phases to the annual cycle. The model's deficiencies, limitations, and future
work are also discussed.
Received: 15 June 1999 / Accepted: 11 December 1999 相似文献
993.
Spatial analysis of monthly precipitation in Turkey 总被引:1,自引:1,他引:1
Summary The principal objectives of this paper are to develop and validate an optimum interpolation method for the spatial analysis
of monthly precipitation in Turkey. A two-dimensional optimum interpolation objective analysis scheme has been developed for
the spatial analysis of precipitation. The model is developed for generating statistically optimum interpolation based on
the irregular distribution of meteorological stations. One question that affects the optimum interpolation method and, indeed,
all such techniques, is how many observations should be allowed to influence a given grid point? The method developed in this
paper addresses this question. For the implementation of the method, 52 stations are considered for Turkey, with 30 years
of monthly data at each point. It is observed that each monthly average spatial correlation function shows a monotonically
decreasing pattern based on 15 km interval averages. The method provides high estimation accuracy in dense station locations
such as in northwestern Turkey. Precipitation contour maps obtained by the optimum interpolation method indicate two spatial
trends over Turkey which have not been identified in any previous study.
Received June 24, 1999/Revised April 26, 2000 相似文献
994.
本文阐述了如何在已建好的局域网内建立自己的WEB网站,并简单叙述了编制网页的几种方法与途径。 相似文献
995.
T. Halenka J. Kalvová Z. Chládová A. Demeterová K. Zemánková M. Belda 《Theoretical and Applied Climatology》2006,86(1-4):125-145
Summary We analyze daily precipitation and temperature extremes over the Czech Republic in a regional climate simulation for the 40-year
period of 1961–2000 carried out with the RegCM3 regional climate model. The model is run at 45 km grid interval and is driven
by NCEP/NCAR reanalysis lateral boundary conditions. Comparison with station data shows that the model performs reasonably
well in simulating the frequency of daily precipitation events of medium to high intensity as well as the precipitation intensities
(return levels) of long return periods, with the exception of mountain stations. While this is attributed mainly to the relatively
coarse representation of topography across the area of the Czech Republic, the parameterization of convection can be another
reason. The model underestimates daily maximum temperature (especially in the warm seasons) and as a result the occurrence
of heat waves (high temperature episodes). The performance of the model improves in the simulation of daily minimum temperature
and cold wave events. In order to apply this regional model to the simulation of extreme events over the complex terrain as
for Czech Republic we recommend that a higher resolution is used in order to better describe the topography of the Czech Republic
and that the daily maximum temperature bias is reduced. 相似文献
996.
希腊作物蒸散的区域性研究 总被引:1,自引:0,他引:1
在希膜的几个试验站对作物蒸散进行了测量,并建立了大量的一年生作物和果树的作物系数,用于与修正的彭曼公式计算出的“基本”作物蒸散相比较,这些系数明显小于FAO24号文件推荐的值,在所有试验站,应用局地获得的作物系数,可更加准确地预报出作物蒸散量。 相似文献
997.
998.
E. Sh. Elizbarashvili M. E. Elizbarashvili N. B. Kutaladze Sh. E. Elizbarashvili N. Z. Chelidze 《Russian Meteorology and Hydrology》2017,42(10):665-670
Variations in the number of hot days, their frequency, intensity, and duration in Georgia are studied using observational data from 50 weather stations for the period of 1936-2013. The periods of the onset of hot days in the year and their maximum intensity in different physiographic conditions are identified. The zoning of Georgia was carried out according to the rate of changes in the number of hot days. The results enhance the understanding of climate change in Georgia under global warming conditions. 相似文献
999.
Long-term variability and methods of forecasting dates of ice break-up in the mouth area of the Ob and Yenisei rivers 总被引:1,自引:0,他引:1
Long-term characteristics of the onset dates of spring ice phases at hydrological stations in the mouth areas of the Ob and Yenisei rivers for 1936–2006 are obtained. The correlations are analyzed between these dates and the frequency of different synoptic processes over the Atlantic and Eurasia in the fall-winter months, the dates when the accumulated temperatures at meteorological stations in the middle parts of the river basins reach 5, 10, 20, 30, and 40°C, and the dates of the start of ice drift at the upstream sections of the Yenisei. Prognostic relations are suggested and test forecasts of the onset dates of ice phases are verified. The percentage of correct forecasts was 67–86%, which makes it possible to recommend the relations for using in prognostic practice. The forecast lead time ranges from 3 to 110 days. 相似文献
1000.
We document a case of exceptionally large natural breaching of a sandy spit (Sacalin spit, Danube Delta) using multiannual to seasonal surveys of topography and bathymetry on successive cross-barrier and shoreface profiles, LiDAR data, satellite imagery, and wind and wave data. The large breach, which quickly reached 3.4 km in May 2014, is attributed to morphological preconditioning of the narrow (50–150 m) barrier, which was susceptible to breaching even during moderate storm conditions. The event switched the barrier's decadal evolution from low cross-shore transport to high cross-shore transport over the barrier, which is an order of magnitude larger than during the non-breach period. Upper shoreface erosion, as indicated by the extensive erosion down to −4 m, indicates that this zone is a significant source for the rebuilding of the barrier. Barrier recovery and widening trigger a negative feedback which limits the back-barrier sediment transfer. As a result, back-barrier deposition decreases whilst the barrier aggradation through overwash becomes more frequent. The Big Breach (TBB) closed naturally in three years. The very high deposition rate of sediment in the breach is a testimony of the high sediment volumes supplied by the longshore transport and the high sediment released through shoreface retreat, and resulted in widening the barrier to a maximum of 1 km. Since the newly-formed barrier shoreline retreated 500 m, this reveals that barrier breaching is an important mechanism which significantly accelerates the landward migration of the barrier system and is a proof of the highly non-linear morphodynamics involved in the barrier island translation. © 2019 John Wiley & Sons, Ltd. 相似文献