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61.
62.
M. H. Abdullah M. B. Mokhtar S. H. J. Tahir A. B. T. Awaluddin 《Environmental Geology》1997,29(1-2):112-117
Sipadan Island is a small oceanic island with limited storage of fresh groundwater. A study was carried out to determine
the effect of tidal change on the groundwater quality of such an island using temperature, dissolved oxygen content, conductivity,
salinity, and pH values as indicators. Overall, the results indicated that the groundwater quality changes with tides, but
the trends of fluctuation differs between the observed parameters. It was found that the percentages of changes during the
period of study were 0.8% (temperature), 53% (dissolved oxygen), 61% (conductivity), 58% (salinity), and 1.7% (pH) at the
centre of the island; and 0.9% (temperature), 33% (dissolved oxygen), 40% (conductivity), 42% (salinity), and 9% (pH) at a
station 120 m from the coast, based on 2.9-m and 2.8-m tidal ranges at each station.
Received: 5 July 1995 · Accepted: 6 November 1995 相似文献
63.
《Geodinamica Acta》2013,26(6):389-400
It is difficult to explain the position and behaviour of the main karst springs of southern France without calling on a drop in the water table below those encountered at the lowest levels of Pleistocene glacio-eustatic fluctuations. The principal karst features around the Mediterranean are probably inherited from the Messinian period (“Salinity crisis”) when sea level dropped dramatically due to the closing of the Straight of Gibraltar and desiccation of the Mediterranean Sea. Important deep karst systems were formed because the regional ground water dropped and the main valleys were entrenched as canyons. Sea level rise during the Pliocene caused sedimentation in the Messinian canyons and water, under a low hydraulic head, entered the upper cave levels. The powerful submarine spring of Port-Miou is located south of Marseille in a drowned canyon of the Calanques massif. The main water flow comes from a vertical shaft that extends to a depth of more than 147 m bsl. The close shelf margin comprises a submarine karst plateau cut by a deep canyon whose bottom reaches 1,000 m bsl. The canyon ends upstream in a pocket valley without relation to any important continental valley. This canyon was probably excavated by the underground paleoriver of Port-Miou during the Messinian Salinity Crisis. Currently, seawater mixes with karst water at depth. The crisis also affected inland karst aquifers. The famous spring of Fontaine de Vaucluse was explored by a ROV (remote observation vehicle) to a depth of 308 m, 224 m below current sea level. Flutes observed on the wall of the shaft indicate the spring was formerly an air-filled shaft connected to a deep underground river flowing towards a deep valley. Outcroppings and seismic data confirm the presence of deep paleo-valleys filled with Pliocene sediments in the current Rhône and Durance valleys. In the Ardèche, several vauclusian springs may also be related to the Messinian Rhône canyon, located at about 200 m below present sea level. A Pliocene base level rise resulted in horizontal dry cave levels. In the hinterland of Gulf of Lion, the Cévennes karst margin was drained toward the hydrologic window opened by the Messinian erosional surface on the continental shelf. 相似文献
64.
渗流场与斜坡稳定性的耦合分析是揭示灌溉诱发型黄土滑坡机理的重要途径,也是后续开展基于水位的滑坡灾害风险控制的基础.在综合分析研究区地质结构和水文地质条件的基础上,以调查、钻探、测量、三维激光扫描和监测资料为依据,联合应用Visual Modflow和FLAC3D数值模拟软件,开展潜水渗流场与斜坡稳定性的耦合分析,模型计算结果与监测及野外调查结果吻合较好,潜水渗流场的演化对斜坡稳定性具有控制作用,随着潜水位的升高,台塬周边不稳定区域逐年增加,1990、2000和2010年焦家崖头附近最大位移值分别为0.85、1.19和1.80m. 相似文献
65.
尾矿库坝体的稳定性分析需充分考虑地形的复杂程度与边界的不规则程度,从而建立尾矿库的真实三维渗流场。利用SVOffice软件在不概化地形及边界的条件下构建尾矿库的真实渗流域,模拟了最后一期填筑在正常高水位(427.77 m)及汛期最高洪水位(434.50 m)两种工况下的三维瞬态渗流场。结果显示:两种工况下,尾矿最大日排水量均为6 100 m3,此时,堆积坝两侧浸润面均有溢出,远离排水井一侧的溢出范围更大,这主要是受渗流域的影响;库内初始水位对筑坝期渗流场的分布存在较大的影响,汛期洪水位筑坝初期浸润面位置最高。由模拟结果设计了5条排渗盲沟,保证了浸润面在堆积坝任何部位均未溢出。 相似文献
66.
Effect of climate change on the trends of evaporation of phreatic water from bare soil in Huaibei Plain,China 总被引:1,自引:0,他引:1 下载免费PDF全文
When the soil condition and depth to water table stay constant, climate condition will then be the only determinant of evaporation intensity of phreatic water from bare soil. Based on a series of long-term quality-controlled data collected at the Wudaogou Hydrological Experiment Station in the Huaibei Plain, Anhui, China, the variation trends of the evaporation rate of phreatic water from bare soil were studied through the Mann-Kendall trend test and the linear regression trend test, followed by the study on the responses of evaporation to climate change. Results indicated that in the Huaibei Plain during 1991-2008, evaporation of phreatic water from bare soil tended to increase at a rate of 5% on monthly scale in March, June and July while in other months the increase was minor. On the seasonal basis, the evaporation saw significant increase in spring and summer. In addition, annual evaporation tended to grow evidently over time. When air temperature rises by 1 °C, the annual evaporation rate increases by 7.24–14.21%, while when the vapor pressure deficit rises by 10%, it changes from-0.09 to 5.40%. The study also provides references for further understanding of the trends and responses of regional evapotranspiration to climate change. 相似文献
67.
利用五道沟水文实验站62套原状土蒸渗仪1991~2015年长系列实验资料,采用非线性拟合方法,模拟了砂姜黑土和黄潮土冬小麦和夏大豆各生育期潜水蒸发随埋深变化的规律。通过多种线型拟合,砂姜黑土两种作物潜水蒸发量随埋深的增大而递减,均呈指数函数关系;黄潮土小麦在返青前和大豆出苗-分枝期,潜水蒸发量随埋深的增大而递减,呈指数函数关系,小麦返青期以后和大豆分枝期后,潜水蒸发量在0.5~0.8m埋深区间达到最大值,在0.5~0.8m区间以浅随埋深增大而增大,在0.5~0.8m区间以深随埋深增大而减小,呈复合函数关系。 相似文献
68.
Great tritium ages explain the occurrence of good-quality groundwater in a phreatic aquifer of an urban area, Lublin, Poland 总被引:1,自引:0,他引:1
The phreatic aquifer of the Lublin chalk in the watershed of the Bystrzyca River, eastern Poland, is characterized by waters
of good quality. Its hydraulic conductivity is related to a fissure network of low porosity, as much as 0.006 at the outcrops.
The good quality of water in this urban setting is surprising because, according to estimates based on Darcy's law, a high
seepage velocity would be expected, resulting in rapid transport of pollutants in the aquifer. However, tritium sampling reveals
that the mean ages range from about 55 to 92 years in four cases, and about 250 to 350 years in 11 cases. One sampling site
is free of tritium, which indicates an even greater age. Such great ages can be explained only by a retardation of solute
transport due to matrix diffusion, that is, an exchange between mobile water in the fissures of low porosity and stagnant
water in the matrix of high porosity. The delay factor is given as the ratio of total porosity to fissure porosity. In consequence,
all types of dissolved constituents and, to some degree, fine suspended matter are delayed in their transport to springs and
wells. In addition, non-conservative constituents have longer times to sorb, react, and decay than in the case of transport
without a dominant influence of matrix diffusion. Though pollutants are greatly delayed, their accumulation in the matrix
and slow diffusion into the fissures contribute to their persistence in groundwater. Regional values of hydraulic conductivity,
estimated from tritium ages and known matrix porosity, agree reasonably well with the values known from pumping tests, which
supports the interpretation of a dominant influence of matrix diffusion on solute transport.
Electronic Publication 相似文献
69.
70.