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The desorption of contaminants from soils/sediments is one of the most important processes controlling contaminant transport and environmental risks. None of the currently adopted desorption models can accurately quantify desorption at relatively low concentrations; these models often overestimate the desorption and thus the risks of hydrophobic organic chemicals, such as benzene and chlorinated solvents. In reality, desorption is generally found to be biphasic, with two soil-phase compartments. A new dual-equilibrium desorption (DED) model has been developed to account for the biphasic desorption. This model has been tested using a wide range of laboratory and field data and has been used to explain key observations related to underground storage tank plumes. The DED model relates the amount of a chemical sorbed to the aqueous concentration, with simple parameters including octanol-water partition coefficient, solubility, and fractional organic carbon; thus, it is the only biphasic model, to date, that is based on readily available parameters. The DED model can be easily incorporated into standard risk and transport models. According to this model, many regulatory standards of soils and sediments could be increased without increasing the risks. 相似文献
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高斯线调频连续小波变换的时频能量衰减因子方法及其应用 总被引:5,自引:0,他引:5
本文基于高斯线调频连续小波变换,提出了能够反映震源区或近场区小地震波形在震源深度、震源尺度、震源破裂机制、地震波传播途径、地震波衰减等方面的差异特征信息的特征指标,即小波变换的时频能量衰减因子方法。为了验证该方法的有效性,选取了震源破裂机制有明显差异特性的天然地震、爆破或塌方资料以及非强地震孕震区同一地点发生的多次小震资料。研究结果表明,天然地震与爆破或塌方记录的连续小波变换时频能量衰减因子有明显区别;正常地震活动背景下地震记录的连续小波变换时频能量衰减因子变化比较稳定;利用该方法,通过对某一地区的连续观测,可望为强震预测提供有效判据。 相似文献
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Sea lice treatments on salmon farms have no adverse effects on zooplankton communities: a case study
The long-term effects of the sea lice treatment products Excis and Slice on zooplankton communities in a Scottish sea loch were investigated at a commercially operating salmon farm over 31 months. Cypermethrin and emamectin benzoate are the active ingredients in Excis and Slice respectively, which are widely used to control ectoparasitic sea lice on farmed salmon. Excis and Slice treatments did not cause basin-wide effects on the zooplankton community. For both formulations, no adverse affects on zooplankton were detected, instead observed changes in zooplankton abundance and community composition displayed natural seasonal cycles of abundance. Water column concentrations of cypermethrin and emamectin benzoate following sea lice treatments at the fish farm were predicted using models. Cypermethrin concentrations of 3000 ng/l were predicted for short periods immediately after each cage treatment assuming no particle adhesion. The 3-h and 24-h Environmental Quality Standards (EQS) were exceeded for 10 h and 32 h respectively on the second day when five cages were treated. However, cypermethrin concentrations higher than 0.5 ng/l (24-h EQS) were predicted to occur over <2% of the total basin area on each treatment day. The 3-h EQS (16 ng/l) was exceeded in <0.3% of the basin on each treatment day. The concentration of soluble emamectin benzoate present in the water column was predicted from modelled deposition footprints and sediment concentrations to be of order 10(-3) ng/l. Predicted concentrations of both chemicals were generally lower than those causing toxicity to copepods in previous laboratory studies and further support the results of this field study that environmental concentrations of Excis and Slice do not adversely impact zooplankton communities. 相似文献
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应用包含在小波变换系数中的信号偏振信息,提出了一种确定单台三分向记录图中P波和S波震相的小波变换方法.主要的思路是寻找地震信号在不同尺度下小波变换系数的显著特性.通过对小波变换系数主成分的分析,得到不同尺度下的P波和S波识别因子,进而形成确定P波和S波初至的定位函数.通过对模拟资料和实际地震资料的分析,认为由小波变换方法形成的定位函数具有一定的抗噪声能力,在精确识别P波和S波初至方面是非常有效的.本文首先介绍了小波变换的基本概念和详细方法,然后应用小波变换对实际资料进行处理,并给出了研究结果. 相似文献