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111.
A three-dimensional multi-level turbulence model is developed to simulate tide induced circulation in coastal waters. Based on the bathymetry data, the coastal waters are divided into a number of layers. In every layer, the velocities are integrated along the layer depth. The eddy viscosity and diffusivity are computed from the Prandtl mixing length turbulence model. This multi-level model solves for the water surface elevations and currents in different water depths. Comparison of numerical results with the measured data shows good conformity. 相似文献
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Contrary to general international perception, Canada does not have an unlimited supply of freshwater. However, because Canada has a small population, it does have a generous water allocation on a per capita basis. Nor is Canada immune from water quality problems:its cold continental climate, urbanization and industrial activities all contribute to water quality concerns and deterioration. Generally, the authority to manage water in Canada is held by the country''s provincial governments. The Great Lakes basin is the world''s largest freshwater ecosystem and is located in Canada''s industrial heartland. Water issues, starting with phosphorus in the 1960''s, created international headlines. In the 1970''s toxics became the predominant issue and this led to the Great Lakes Water Quality Agreement which established the ecosystem approach to water quality management. This approach is now the standard approach to water quality management and has been successfully applied to a number of other lake and river ecosystems in Canada. While there have been improvements in the water quality of the Great Lakes much remains to be done on toxic elimination and the large contaminant stores in the sediments. Atmospheric deposition has become a significant source of chemicals from outside the basin The Canadian prairies, the agricultural heartland of Canada, is one major ecozone that has not been selected to have current and potential water quality problems examined by a federal government program. Both the quantity and quality of water in this region are potentially significant factors limiting economic diversification and sustainable development in this vast and ecologically disturbed region. 相似文献
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From the HISTRHONE database we extracted 1483 hydro-meteorological events from AD 1300 to 2000 that occurred in the Lower Rhône Valley, France. Daily heights of the Rhône River at Beaucaire and Arles are also available, from 1816 and 1829, respectively. A total of 517 floods were divided into three categories and a synthetic frequency severity index (FSI) was computed. Running averages of 11 and 31 years show a succession of poor and rich flood fluctuations. Extreme floods tripled in the second half of the period (1650–2000). Singular spectrum analysis isolates a dominant irregular component (main positive anomalies in 1450–1580, around 1700, late 18th century, and most of the 20th century). We focus on the 17th century, with rare flooding events between two secular so-called “hyper phases”, i.e. frequent and/or severe floods. We also recorded 173 episodes of ice in the river, during the Little Ice Age. 相似文献
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基于质量守恒以及电中性条件,采用化学平衡计算法,计算模拟研究了高岭石固相平衡的酸性天然地表水中铝的缓冲作用对pH值,酸中和容量ANC和缓冲强度β的影响,讨论了影响酸性地表水pH估算的各种因素,如溶解硅酸的浓度,溶解总无机碳的浓度,溶解总氟和总有机碳的浓度及温度等。模型被用于实际水样的分析,所得结果与实验值符合较好,用MonteCarlo模拟考察了由于平衡常数的选择以及水化学参数测量误差而带来的不确 相似文献
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The area of north Evia and eastern central Greece is characterized by strong geomorphological contrast and is built up mainly of consolidated rocks. Unconsolidated young sediments of Pleistocene to Holocene age cover the valley and basin flats, forming the most productive aquifers in this area. However, two more types of aquifers can be distinguished within the consolidated rock area. The first one is associated with karstified limestones and the second with strongly tectonized ultramafic rocks. The schist–chert formation, with intercalations of shales and cherts, seals the ultramafic masses underneath. Surface and spring waters associated with ultramafic rocks in north Evia and eastern central Greece were studied. Two types of water can be distinguished: (1) high Mg2+ and SiO2 , bicarbonate as the dominant anion, pH 7·4–9·2, temperature 9·5–16·3 °C, low TDS (total dissolved solutes) (459–1037 mg/l), found both in peridotite and serpentinite areas, classified as Mg–HCO3 type; (2) high Ca2+, low Mg2+ and SiO2 , hydroxyl ion as the major anion, pH 11·2, temperature 28 °C, very low TDS (122 mg/l), found in peridotite areas, classified as Ca–OH type. The studied waters are highly supersaturated with respect to quartz, amorphous silica, brucite and most low temperature magnesium silicates (antigorite, sepiolite, talc, etc.). These waters show relatively narrow SiO2 concentration ranges and a trend parallel to the amorphous silica saturation surface. The silica supersaturated waters have the potential to precipitate silica and consequently could affect the people of the local communities that use it as drinking water, causing health problems (kidney stones). Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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Józef Lis Anna Pasieczna Ryszard Strzelecki Stanis?aw Wo?kowicz Pawe? Lewandowski 《Journal of Geochemical Exploration》1997,60(1):39-53
In 1990 the Polish Geological Institute initiated geochemical mapping of the country aimed at determining the actual conditions of chemistry in the Earth's surficial environments (soils, water sediments, and surficial waters as well) and sea-floor deposits in the Polish economic sector of the Baltic Sea. The geochemical mapping on different scales covered the entire area of the country and selected more important urban agglomerations and industrial districts. Approximately 15,100 samples of soils, 16,200 samples of fresh water sediments, 14,600 samples of surface waters and 467 samples of marine deposits were collected and analysed. A list of geochemical atlases published by the Polish Geological Institute is presented. Investigation of the distribution of radionuclides (natural and artificial) has been done since 1992. Concentrations of U, Th, K, post-Chernobyl Cs and γ dose rate were measured. Approximately 20,000 points covering the whole country were measured. More detailed mappings were executed in the areas polluted by Cs. 相似文献