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791.
George Aim Skianis 《Earth Science Informatics》2012,5(1):13-21
Numerous efforts have been made to study how the spatial distribution of ground surface objects controls the image semivariogram.
The present paper is centered on how the histograms and semivariograms of the individual bands x and y influence the spatial variation of a simple spectral ratio u = arctan(x/y). The image histogram of each separate band is described by a proper distribution. The exponential model is used to describe
the semivariograms of x and y. Taking the first derivatives of the spectral ratio u for x and y and taking into account the mathematical behavior of the histograms of bands x and y, an approximate expression for the semivariogram γ
u
of the spectral ratio is derived. This mathematical expression shows how the spatial variation of the spectral ratio depends
on the standard deviations of the histograms, as well as the ranges of the semivariograms of x and y. Experimentation with multispectral images is then carried out and it shows that theoretical predictions agree, in qualitative
terms, with real data. The results and conclusions of this paper may be useful in assessing the efficiency of various spectral
band ratios and vegetation indices, which are often used in geological and environmental research (mapping of hydrothermal
zones and land cover types). 相似文献
792.
Geochemistry of surface sediments and heavy metal contamination assessment: Messolonghi lagoon complex,Greece 总被引:2,自引:2,他引:0
Aristomenis P. Karageorgis Andreas Sioulas Evangelia Krasakopoulou Christos L. Anagnostou George A. Hatiris Harikleia Kyriakidou Konstantinos Vasilopoulos 《Environmental Earth Sciences》2012,65(6):1619-1629
The Messolonghi lagoon complex in Western Greece receives agricultural and domestic effluents both from point and diffused
sources. Surface sediments were analyzed for grain size, organic carbon, total nitrogen, total sulfur, major and minor elements,
aiming at the identification of geochemical relationships between all variables. Enrichment factors and the modified degree
of contamination methods were applied to assess potential heavy metal enrichment related to human activities. Sediment texture
was highly variable, with muddy sediments prevailing. In the central sector of the Messolonghi lagoon, organic carbon contents
were high. Principal factor analysis revealed the following main groups of variables with common geochemical behavior: (1)
terrigenous aluminosilicates (2) organic matter, (3) biogenic carbonates, (4) mineral quartz-aluminosilicates, and (5) Mn-oxides.
Enrichment factors estimated for V, Cr, Mn, Co, Ni, Cu, Zn, and Pb using local pre-industrial sediment showed that all metals
exhibit almost natural background levels, except for Pb, which was found to be slightly elevated (legacy of leaded fuel).
Estimation of contamination factors concluded in similar results, whereas the overall modified degree of contamination was
at the lowest level, therefore suggesting that this transitional water body has not been affected by anthropogenic activities.
The data set may be considered as a baseline for future monitoring projects according to EU policy. 相似文献
793.
Morphometrical analysis of two tropical mountain river basins of contrasting environmental settings, the southern Western Ghats, India 总被引:8,自引:4,他引:4
Jobin Thomas Sabu Joseph K. P. Thrivikramji George Abe N. Kannan 《Environmental Earth Sciences》2012,66(8):2353-2366
The morphometric analysis of river basins represents a simple procedure to describe hydrologic and geomorphic processes operating on a basin scale. A morphometric analysis was carried out to evaluate the drainage characteristics of two adjoining, mountain river basins of the southern Western Ghats, India, Muthirapuzha River Basin (MRB) in the western slopes and Pambar River Basin (PRB) in the eastern slopes. The basins, forming a part of the Proterozoic, high-grade, Southern Granulite Terrain of the Peninsular India, are carved out of a terrain dominantly made of granite- and hornblende-biotite gneisses. The Western Ghats, forming the basin divide, significantly influences the regional climate (i.e., humid climate in MRB, while semi-arid in PRB). The Survey of India topographic maps (1:50,000) and Shuttle Radar Topographic Mission digital elevation data were used as the base for delineation and analysis. Both river basins are of 6th order and comparable in basin geometry. The drainage patterns and linear alignment of the drainage networks suggest the influence of structural elements. The Rb of either basins failed to highlight the structural controls on drainage organization, which might be a result of the elongated basin shape. The irregular trends in Rb between various stream orders suggest the influence of geology and relief on drainage branching. The Dd values designate the basins as moderate- to well-drained with lower infiltration rates. The overall increasing trend of Rl between successive stream orders suggests a geomorphic maturity of either basins and confirmed by the characteristic I hyp values. The Re values imply an elongate shape for both MRB and PRB and subsequently lower vulnerability to flash floods and hence, easier flood management. The relatively higher Rr of PRB is an indicative of comparatively steeply sloping terrain and consequently higher intensity of erosion processes. Further, the derivatives of digital elevation data (slope, aspect, topographic wetness index, and stream power index), showing significant differences between MRB and PRB, are useful in soil conservation plans. The study highlighted the variation in morphometric parameters with respect to the dissimilarities in topography and climate. 相似文献
794.
George D. Bathrellos Kalliopi Gaki-Papanastassiou Hariklia D. Skilodimou Dimitrios Papanastassiou Konstantinos G. Chousianitis 《Environmental Earth Sciences》2012,66(2):537-548
During the planning of an urban environment, usually only economic and social parameters are taken into account. As a result,
urban areas are susceptible to natural disasters, which cause extensive damages in them, because the cities or towns have
been repeatedly located in vulnerable areas. In this study, for the protection of human environment, is proposed a unique
approach of urban planning and sustainable development. The study area is Trikala Prefecture (Western Thessaly, Central Greece).
An integrated evaluation of the suitable areas for urban growth and light industry development is proposed by using mainly
natural hazards as well as geological–geomorphological–geographical characteristics of the study area. The used parameters
were correlated by using the analytical hierarchical process (AHP) method and incorporated into a geographic information system
(GIS) in order to produce the corresponding suitability maps. The study area is classified in five categories of very high,
high, moderate, low, and very low suitability for urban growth and industrial development. Moreover, the spatio-temporal changes
of the urban limits are studied since 1885 for the three major towns (Trikala, Kalambaka and Pyli) of the study area. These
changes sketch out the urban growth trend. The comparison between the urban growth trend with the potential suitability for
urban growth and industrial development of these towns lead to discrepancies. These can be attributed mainly to the fact that
in the majority of cases, only geographical, social, and economical factors were used for urban development, whereas in our
study, natural hazards, geomorphological, and geographical parameters were quantified and taken into account. 相似文献
795.
796.
P. Sargent Bray Claudia M. Jones Stewart J. Fallon Jochen J. Brocks Simon C. George 《Quaternary Research》2012,77(1):104-109
Assigning accurate dates to hypersaline sediments opens important terrestrial records of local and regional paleoecologies and paleoclimatology. However, as of yet no conventional method of dating hypersaline systems has been widely adopted. Biomarker, mineralogical, and radiocarbon analyses of sediments and organic extracts from a shallow (13 cm) core from a hypersaline playa, Lake Tyrrell, southeastern Australia, produce a coherent age-depth curve beginning with modern microbial mats and extending to ~ 7500 cal yr BP. These analyses are furthermore used to identify and constrain the timing of the most recent change in hydrological regime at Lake Tyrrell, a shift from a clay deposit to the precipitation of evaporitic sands occurring at some time between ~ 4500 and 7000 yr. These analyses show the potential for widespread dating of hypersaline systems integrating the biomarker approach, reinforce the value of the radiocarbon content of biomarkers in understanding the flow of carbon in modern ecologies, and validate the temporal dimension of data provided by biomarkers when dating late Quaternary sediments. 相似文献
797.
Wang Qiuxuan Song Li Agusti Susana Duarte Carlos Christakos George Wu Jiaping 《Ocean Science Journal》2021,56(4):395-405
Ocean Science Journal - Macrobenthos organisms are vital ecological components of intertidal wetlands. This work studied effects of non-native mangrove rehabilitation (Kandelia obovata) and salt... 相似文献
798.
Maria Francesca Milazzo Giuseppa Ancione Anna Basco David George Lister Ernesto Salzano Giuseppe Maschio 《Natural Hazards》2013,66(2):939-953
The phenomenon of volcanic fallout ash from Mt. Etna in Sicily (Italy) is well known and frequent in recent years, as in the period 2001–2004. As a consequence, significant problems for the population, road, rail and air traffic and production activities have occurred. The industrial areas of Catania and Augusta-Priolo, located in south eastern Sicily, might be involved during particular weather conditions. This paper aims at determining the potential scenarios of damage to industrial facilities caused by volcanic ash fallout. The work has been focused on the study of both fixed and floating roof storage tanks, containing flammable liquids, and examines extreme failures damage causing the greatest loss of containment for these facilities. To include scenarios arising from natural phenomena (Na-Tech events) in the standard risk assessment procedure, the estimation of the vulnerability of these facilities is necessary. The study has been applied to the area surrounding Mt. Etna, and the procedure can also be extended to other case studies. 相似文献
799.
Yeonsang?HwangEmail author Martyn?Clark Balaji?Rajagopalan George?Leavesley 《Stochastic Environmental Research and Risk Assessment (SERRA)》2012,26(2):295-320
Distributed hydrologic models typically require spatial estimates of precipitation interpolated from sparsely located observational
points to the specific grid points. We compare and contrast the performance of regression-based statistical methods for the
spatial estimation of precipitation in two hydrologically different basins and confirmed that widely used regression-based
estimation schemes fail to describe the realistic spatial variability of daily precipitation field. The methods assessed are:
(1) inverse distance weighted average; (2) multiple linear regression (MLR); (3) climatological MLR; and (4) locally weighted
polynomial regression (LWP). In order to improve the performance of the interpolations, the authors propose a two-step regression
technique for effective daily precipitation estimation. In this simple two-step estimation process, precipitation occurrence
is first generated via a logistic regression model before estimate the amount of precipitation separately on wet days. This
process generated the precipitation occurrence, amount, and spatial correlation effectively. A distributed hydrologic model
(PRMS) was used for the impact analysis in daily time step simulation. Multiple simulations suggested noticeable differences
between the input alternatives generated by three different interpolation schemes. Differences are shown in overall simulation
error against the observations, degree of explained variability, and seasonal volumes. Simulated streamflows also showed different
characteristics in mean, maximum, minimum, and peak flows. Given the same parameter optimization technique, LWP input showed
least streamflow error in Alapaha basin and CMLR input showed least error (still very close to LWP) in Animas basin. All of
the two-step interpolation inputs resulted in lower streamflow error compared to the directly interpolated inputs. 相似文献
800.
Wei Shen Klaus-Werner Gurgel George Voulgaris Thomas Schlick Detlef Stammer 《Ocean Dynamics》2012,62(1):105-121
Land-based high-frequency (HF) radars have the unique capability of continuously monitoring ocean surface environments at
ranges up to 200 km off the coast. They provide reliable data on ocean surface currents and under slightly stricter conditions
can also give information on ocean waves. Although extraction of wind direction is possible, estimation of wind speed poses
a challenge. Existing methods estimate wind speed indirectly from the radar derived ocean wave spectrum, which is estimated
from the second-order sidebands of the radar Doppler spectrum. The latter is extracted at shorter ranges compared with the
first-order signal, thus limiting the method to short distances. Given this limitation, we explore the possibility of deriving
wind speed from radar first-order backscatter signal. Two new methods are developed and presented that explore the relationship
between wind speed and wave generation at the Bragg frequency matching that of the radar. One of the methods utilizes the
absolute energy level of the radar first-order peaks while the second method uses the directional spreading of the wind generated
waves at the Bragg frequency. For both methods, artificial neural network analysis is performed to derive the interdependence
of the relevant parameters with wind speed. The first method is suitable for application only at single locations where in
situ data are available and the network has been trained for while the second method can also be used outside of the training
location on any point within the radar coverage area. Both methods require two or more radar sites and information on the
radio beam direction. The methods are verified with data collected in Fedje, Norway, and the Ligurian Sea, Italy using beam
forming HF WEllen RAdar (WERA) systems operated at 27.68 and 12.5 MHz, respectively. The results show that application of
either method requires wind speeds above a minimum value (lower limit). This limit is radar frequency dependent and is 2.5
and 4.0 m/s for 27.68 and 12.5 MHz, respectively. In addition, an upper limit is identified which is caused by wave energy
saturation at the Bragg wave frequency. Estimation of this limit took place through an evaluation of a year long database
of ocean spectra generated by a numerical model (third generation WAM). It was found to be at 9.0 and 11.0 m/s for 27.68 and
12.5 MHz, respectively. Above this saturation limit, conventional second-order methods have to be applied, which at this range
of wind speed no longer suffer from low signal-to-noise ratios. For use in operational systems, a hybrid of first- and second-order
methods is recommended. 相似文献