全文获取类型
收费全文 | 76篇 |
免费 | 10篇 |
国内免费 | 17篇 |
专业分类
地球物理 | 7篇 |
地质学 | 86篇 |
综合类 | 1篇 |
自然地理 | 9篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 6篇 |
2014年 | 1篇 |
2013年 | 3篇 |
2012年 | 3篇 |
2011年 | 5篇 |
2010年 | 5篇 |
2009年 | 6篇 |
2008年 | 11篇 |
2007年 | 7篇 |
2006年 | 13篇 |
2005年 | 4篇 |
2004年 | 3篇 |
2003年 | 6篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 2篇 |
排序方式: 共有103条查询结果,搜索用时 468 毫秒
81.
中水灌溉下重金属在土壤中的垂直迁移及其对地下水的污染风险 总被引:25,自引:2,他引:23
中水灌溉是解决水资源短缺的潜在途径,关于中水灌溉条件下土壤中重金属的迁移行为及其对浅层地下水的污染风险至今仍缺乏研究。本文通过土柱模拟试验,分析中水灌溉条件下重金属在土壤中的迁移趋势及其对浅层地下水的污染风险。试验用添加重金属(As、Cd、Cu、Pb浓度分别为2、0.2、20、20 mg.kg-1)的人工污水和中水以1年、3年的灌溉量进行土柱淋溶实验。结果表明,淋溶20天(1年的灌溉量)以及60天(3年的灌溉量),灌溉水中的As、Cd、Cu和Pb主要在表层(010cm)累积。随着淋溶时间的延长,4种重金属(尤其是Cd)表现出向下迁移的趋势。但与地下水I级水质标准(GB/T14848-93)相比,淋滤液中4种重金属均未超标。因此,从本文的模拟试验来看,以北京市当前的中水进行灌溉,As、Cu、Pb对浅层地下水的污染风险不大。 相似文献
82.
83.
Mara R. Diaz Peter K. Swart Gregor P. Eberli Amanda M. Oehlert Quinn Devlin Amel Saeid Mark A. Altabet 《Sedimentology》2015,62(7):2090-2112
Ooid formation remains elusive despite their importance as palaeoclimatic indicators and important contributors to global carbonate budget. Based on stable isotopes, nutrient and elemental analyses on solid components and ooidal leachates, this study supports the notion of microbial involvement in the development of ooids from Great Bahama Bank. Carbon and nitrogen isotopic analyses on organic fractions identified geochemical signatures of microbial activity. The δ13C values for organic carbon in the bulk (?11·9 to ?16·9‰); intercrystalline/intracrystalline (?11·9 to 16·7‰); and intracrystalline phases (?12·4 to ?17·7‰) were similar and, except for the more enriched values of ooids from Butterfly Beach, were within the range of photosynthesisers. The δ15N values for the bulk (+0·5 to ?0·2‰); intercrystalline/intracrystalline (?0·3‰ to ?0·7‰) and intracrystalline organic matter (?0·3 to ?1·7‰) showed a narrow range consistent with nitrogen fixation. While positive δ15N and δ18O values of the leached from the ooids provided evidence of denitrification, the carbonate associated sulphate δ34SCAS of the bulk sediments (+19·2 to +19·6‰) and δ34S of the leachates (+16·6 to +18·3‰) provided weak indication of sulphate reduction, suggesting either that high concentrations of isotopically enriched S are overriding bio‐signatures of sulphate reduction or that microbes are preferentially using as an electron acceptor. In contrast, the elevated sulphate concentrations of the leachates suggest the occurrence of microbial sulphide oxidation within ooids. The high Mg/Ca of the leachates and scanning electron microscope analyses provide putative evidence of amorphous calcium carbonate and a formative role in CaCO3 precipitation. Together, these findings indicate that a redox dependent microbial consortium may influence CaCO3 precipitation in the form of ooid accretion, cementation and micritization. It is also inferred that ooid deposits are not suitable indicators of palaeoclimate because ooids are affected throughout their life by a complex chain of abiotic and biological processes which can lead to large geochemical offsets. 相似文献
84.
85.
为研制出一种低渗透系数并对污染物有一定吸附阻滞作用的浆材,用于城市生活垃圾填埋场渗滤液防渗工程,通过正交试验优选出了以膨润土为主的浆材配方:膨润土20%~30%,水泥15%~25%,粉煤灰20%~25%,纯碱1.0%~1.4%,稀释剂FCLS加量0.35%~0.75%,余之为水.该浆材结石率〉99.6%,固结体28d渗... 相似文献
86.
87.
88.
89.
非开挖HDD技术具有对环境干扰小、施工效率高等优点,被广泛应用于给排水、电力、通信、油气等领域的新管道敷设和既有管线修复中。本文结合英国某垃圾填埋场的渗滤液导流治理工程,分别从技术原理、工程背景、工艺过程、应用效果和改进措施等方面展开了论述。工程实践表明,HDD技术可应用于垃圾填埋场渗滤液水平排放孔的施工中,并应根据现场地层条件和工艺参数对施工过程加以优化。由于填埋堆体含有大量金属废弃物,采用有线导向系统替换了无线电磁导向,可极大提高导向钻孔轨迹的定位精度。采用正向扩孔和管道敷设技术有助于降低阻力,提高敷设效果。对比运行结果显示,相对于传统的渗滤液竖井抽排模式,水平钻孔排放效率更高,成本投入也相对较低,但在设计施工中应充分考虑堆体非均质对施工过程的影响,降低施工风险。 相似文献
90.
The Nanjido Landfill is the largest uncontrolled landfill in Korea and it causes various kinds of environmental problems.
Landfill gases and leachate are recognized as the most serious environmental problems associated with the landfill. This study
employs a series of numerical models and uses test data to interpret the distribution and flow of landfill gases and leachate.
Leachate seepage appears about 40–60 m higher than the estimated basal groundwater table. Thus, seepage data indicate that
perched or floating leachate layers are formed in the unsaturated zone of the landfill. The leachate production rate is estimated
using infiltration test data and a model for unsaturated groundwater flow. Geochemical data indicate that the landfill leachate
degrades the basal groundwater quality along the downgradient zone. The environmental impact of the leachate on river water
is estimated.
Received: 17 June 1996 · Accepted: 2 October 1996 相似文献