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641.
Advances in automated detection of sand dunes on Mars 总被引:1,自引:0,他引:1
This paper describes advances in an automatic approach for the detection of sand dunes of Mars, based on supervised learning techniques. A set of features (gradient histogram) is extracted from the remotely sensed images and two classifiers (Support Vector Machine and Random Forests) are trained from this data. The evaluation is conducted on 230 MOC‐NA images (spatial resolution between 1·45 and 6·80 m/pixel) leading to about 89% of correct detections. A detailed analysis of the detection results (dune/non‐dune) is performed by dune type or bulk shape, confirming high performances independently of the way the dataset is analysed. This demonstrates the robustness and adequacy of the automated approach to deal with the large variety of aeolian structures present on the surface of Mars. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Rodrigo Valdés-Pineda Roberto Pizarro Juan B. Valdés Jorge F. Carrasco Pablo García-Chevesich Claudio Olivares 《水文科学杂志》2013,58(11):2110-2132
ABSTRACTPrecipitation is the most critical climatic element that directly affects the availability of water resources. The objective of this study was to describe and discuss spatio-temporal patterns of annual precipitation, its aggressiveness, and its concentration along the southwest coast of South America (36°–49°S) from 1930 to 2006. An annual and multi-decadal analysis was applied to 107 sampling stations distributed throughout this region, using the Mann-Kendall test (MK), and the Sampling Uncertainty Analysis (SUA) coupled with Gumbel probability density function (SUA-Gumbel). The analysis revealed positive but not significant trends in annual precipitation and aggressiveness for the region between 36° and 44°S, at least during the last 50 years of the analysed period. However, a significant decrease in annual precipitation and aggressiveness was observed between 44° and 49°S during the same period. The annual concentration of precipitation became slightly more seasonal in the last 50 years within the entire study area. 相似文献
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Eric C. J. Oliver Jinyu Sheng Keith R. Thompson Jorge R. Urrego Blanco 《Natural Hazards》2012,64(2):1425-1446
This study presents a methodology for estimating extreme current speeds from numerical model results using extremal analysis techniques. This method is used to estimate the extreme near-surface and near-bottom current speeds of the northwest Atlantic Ocean with 50-year return periods from 17?years of model output. The non-tidal currents produced by a three-dimensional ocean circulation model for the 1988?C2004 period were first used to estimate and map the 17-year return period extreme current speeds at the surface and near the bottom. Extremal analysis techniques (i.e., fitting the annual maxima to the Type I probability distribution) are used to estimate and map the 50-year extreme current speeds. Tidal currents are dominant in some parts of the northwest Atlantic, and a Monte Carlo-based methodology is developed to take into account the fact that large non-tidal extrema may occur at different tidal phases. The inclusion of tidal currents in this way modifies the estimated 50-year extreme current speeds, and this is illustrated along several representative transects and depth profiles. Seasonal variations are examined by calculating the extreme current speeds for fall-winter and spring?Csummer. Finally, the distribution of extreme currents is interpreted taking into account (1) variability about the time-mean current speeds, (2) wind-driven Ekman currents, and (3) flow along isobaths. 相似文献
646.
Marbles and carbonate rocks from central Morocco: a petrographic,mineralogical and geochemical study
Francesca Origlia Elisabetta Gliozzo Anna Gandin Marco Meccheri Jorge E. Spangenberg Isabella Turbanti Memmi 《Environmental Earth Sciences》2012,66(1):209-222
Petrographic, mineralogical, and stable isotopes (δ13C, δ18O values) compositions were used to characterise marbles and sedimentary carbonate rocks from central Morocco, which are considered
to be a likely source of ornamental and building material from Roman time to the present day. This new data set was used in
the frame of an archaeometric provenance study on Roman artefacts from the town of Thamusida (Kenitra, north Morocco), to assess the potential employment of these rocks for the manufacture of the archaeological materials.
A representative set of samples from marbles and other carbonate rocks (limestone, dolostone) were collected in several quarries
and outcrops in the Moroccan Meseta, in a region extending from the Meknes–Khenifra alignment to the Atlantic Ocean. All the
samples were studied using a petrographic, mineralogical and geochemical methods. The petrographic and minerological investigations
(optical microscopy, electron microscopy, X-ray diffraction) allowed to group the carbonate rocks in limestones, foliated
limestone, diagenetic breccias and dolostone. The limestones could be further grouped as mudstones, wackestones–packstones,
crinoid grainstones, oolitic grainstone and floatstones. Textural differences allowed to define marbles varieties. The stable
carbon and oxygen isotope composition proved to be quite useful in the discrimination of marble sources, with apparently less
discriminatory potential for carbonate rocks. 相似文献
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Rodrigo Augusto Bellezoni Cristiano Kenji Iwai Vagner Roberto Elis Wanderley da Silva Paganini Jorge Hamada 《Environmental Earth Sciences》2014,71(5):2429-2439
In Brazil, the large quantities of solid waste produced are out of step with public policies, technological developments, and government budgets for the division. In small municipalities, the common lack of technological knowledge and financial conditions for suitable waste disposal has resulted in a large number of illegal dumps. Therefore, small sanitary landfill facilities are working with simplified operations focusing on cost reduction and meeting the economic and technological standards of the city without endangering the environment or public health. Currently, this activity is regulated at a federal level although there is some uncertainty regarding the risk of soil and aquifer contamination as theses facilities do not employ liners. Thus, this work evaluates a small landfill to identify changes in soil and groundwater using geotechnical parameters, monitoring wells, and geophysical tests performed by electrical profiling. It is verified that based on current conditions, no contaminants have migrated via underground water aquifers, and overall no significant changes have occurred in the soil. It is concluded that, despite its simplicity, the method investigated is a viable alternative for the final disposal of municipal solid waste from small cities, especially in developing countries. 相似文献