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1.
Wu F  Qing H  Wan G 《Water research》2001,35(5):1334-1337
Lake water, pore water, and sediments were sampled in both polluted and unpolluted lakes from Southwestern (SW) China Plateau. The results show that although the mechanisms of nutrient regeneration were similar in the polluted and unpolluted lakes, the processes, however, were much stronger in the polluted lakes. Nitrogen regeneration was mainly of organic process. Phosphorus regeneration was essentially controlled by iron redox cycling near sediment/water interface. Nutrient upward fluxes were in the order SiO2 > NH4+ > PO4(3-). This study has significance for further investigating the response of nutrient biogeochemistry to the increasing nutrient levels in aquatic environments.  相似文献
2.
Total gaseous mercury in the atmosphere of Guiyang,PR China   总被引:14,自引:0,他引:14  
Four measurement campaigns were carried out to monitor total gaseous mercury (TGM) at one site in the Guiyang City, PR China in the following periods: April 19-30, 2000; February 26-March 14, 2001; June 26-July 20, 2001; and October 9-November 22, 2001, respectively. High temporal resolved data were obtained by using automated mercury analyzers Gardis 1A and Tekran 2537A. TGM data from all measurement periods followed the typical log normal distribution pattern. The geometric mean of TGM from different seasons were 8.56, 7.45, 5.20 and 8.33 ngm(-3) in spring 2000, winter 2001, summer 2001 and autumn 2001, respectively. The overall average TGM covering the sampling periods was 7.39 ngm(-3), which is significantly elevated comparing to global background of approximately 1.5-2.0 ngm(-3). The major anthropogenic atmospheric mercury emission sources differed significantly among seasons, which caused the seasonal variability of TGM level. Distinct daily variability of TGM was observed among seasons. The daytime TGM concentrations were larger than that of nighttime in spring and winter seasons, while in summer and autumn the opposite daily TGM distribution pattern was observed.  相似文献
3.
石灰岩应力–应变全过程的非Darcy流渗透特性   总被引:13,自引:3,他引:10       下载免费PDF全文
利用瞬态渗透法测定了石灰岩在应力-应变全过程的非Darcy流渗透特性,发现一种新的试验现象,即在峰后大应变状态下非Darcy流β因子为负。这一试验现象使得人们可以立足于实验室试验来验证、预测和分析岩石渗流失稳现象和规律。建市了一种瞬态法测定岩石渗透特性的试验系统的动力学模型,介绍了由孔隙压力差单一时间序列提取非Darcy流渗透特性参数(渗透率、非Darcy流β因子和加速度系数)的方法,并对石灰岩标准试样进行了应力-应变全过程的渗透试验。研究表明,无论在峰前还是峰后,石灰岩的渗流都不服从Darcy定律;当非Darcy流β因子为正时,非Darcy流的渗透率小于Darcy流的渗透率;当Darcy流β因子为负时,由于裂隙的贯通,孔隙压力迅速衰减,石灰岩中渗流可能失稳。提出的非Darcy流渗透特性的测定方法,继承了以往实验室试验的成熟技术,只是在数据处理方面进行了尝试,既不增加试验成本,又不加大试验的技术难度,便于被用户接受。  相似文献
4.
Thallium (Tl) contamination in soils poses a significant threat to human health due to the high toxicity of Tl and its ready assimilation by crops. This study is focused on high concentrations of Tl in soils in the Lanmuchang area of southwest Guizhou, China, which is related to natural processes of Tl-rich sulfide mineralization. Thallium contents range from 40 to 124 mg/kg in soils originating from the mining area, from 20 to 28 mg/kg in slope wash materials, from 14 to 62 mg/kg in alluvial deposits downstream, from 1.5 to 6.9 mg/kg in undisturbed natural soils and <0.2 to 0.5 mg/kg Tl in soils from the background area. These values indicate that both the erosion of natural soils from the Tl mineralized area and the mining activity are responsible for the distribution of high Tl concentrations in soils. Two other important toxic metals of interest, mercury and arsenic, also show high contents in soils, and are generally higher than Tl concentrations. Thallium concentration in plants exhibit species-dependent preferences. Thus, the enrichment of Tl in the edible parts of crop species decreases in the following order: green cabbage>carrot>chili>Chinese cabbage>rice>corn. The highest level of Tl in green cabbage is up to 500 mg/kg as dry wt., surpassing the values of Tl in the soils in which the green cabbages grow. In contrast, Hg and As are relatively less concentrated in local plants. The average daily uptake of Tl by the villagers of the Lanmuchang area through consumption of locally planted crops has been estimated to be 1.9 mg/person, which is 50 times the daily ingestion of individuals from the Tl-free background area. The daily ingestion of As and Hg from the study area are 0.03 and 0.01 mg, respectively. This indicates that Tl in the contaminated soils related to the natural Tl mineralization is being readily transferred to the human body through the food chain, and poses a significant threat to the health of the local villagers. Arsenic may pose a lesser health hazard, but mercury has an insignificant health risk. This study illustrates a real environmental concern related to land use and human health in areas containing high contents of Tl in soils associated with the natural occurrence of Tl-rich sulfides and coals, with or without mining activities. Thallium contamination in soils should be a critical parameter for proper land use and health related environmental planning and regulations.  相似文献
5.
Twenty-two rainwater samples from Guiyang city, southwestern China, have been analyzed for their chemical compositions and 87Sr/86Sr ratios, with a main purpose to get a better understanding of the general features of rainwater in Guiyang city and their correspondences to human activities. The rainwaters studied are almost acidic (pH=4.53) and show big changes in major ion composition. Ca2+ and Mg2+ are the principal cations in the rainwaters and their mean values are 56.6 micromol/L (12.5-163.8 micromol/L) and 12.8 micromol/L (4.5-47.3 micromol/L ), respectively. The sum of Ca2+ and Mg2+ accounts for 78%-96% of the total cations in the studied rainwaters. Na+ was the least abundant of the major cations with a mean content of 4 micromol/L (0.9-7.8 micromol/L). SO4(2-) is the predominant anion, with a mean content of 94 micromol/L (33.5-279.4 micromol/L), coming next is NO(3-) with a mean content of 48 micromol/L (2.1-251.8 micromol/L). SO4(2-) and NO(3-) together account for 77%-99% of the total anions. Ca2+ and Mg2+ in the rainwater are most likely from dissolution of carbonate minerals in dust or aerosol, unlike K+ that shows more contribution of anthropogenic sources to the rainwater. Na+ does not vary in concentration with Cl-. Significant enrichment of Cl- relative to Na+ as compared with sea water indicates negligible contribution of marine source, which is supported by the evidence that the total rainwater samples show lower 87Sr/86Sr ratios (ranging from 0.707934 to 0.709080) than sea water. The rainwater samples are characterized by high contents of NO(3-), SO4(2-), and Cl- relative to Na+, as compared to the rainwater from other areas in the world, suggesting that the anions (NO(3-), SO4(2-), and Cl-) have mainly of anthropogenic sources. Sr isotope shows potential to trace sources of contaminants when combined with other chemical factors: covariation of 87Sr/86Sr ratio with Cl-/Na+ in the rainwater suggest presence of at least two anthropogenic sources for the rainwater samples studied. The coal-combustion industries are probably the major atmospheric contaminant sources in Guiyang city.  相似文献
6.
Baihua Reservoir in Guizhou Province, China, experienced serious Hg contamination from Guizhou Organic Chemical Plant (GOCP) between 1971 and 1997. However, the biogeochemical cycling of Hg in this reservoir is not well studied. Sediment cores were collected in fall 2002, spring 2003 and in spring and fall 2004. THg and MeHg concentrations in all sediment profiles ranged from 0.26 to 38.9 mg/kg and from 0.5 to 27.5 μg/kg (d.w.), respectively. The distribution of THg in sediment cores was characterized by a few peaks, which may correspond to the Hg-containing wastewater discharge history of the GOCP. The average THg concentrations in sediments cores decreased from upstream to downstream due to the deposition of particulate Hg, which is the major form of Hg in water. THg and MeHg concentrations in pore water varied from 6.1 to 5860 ng/L and from 0.3 to 15.4 ng/L, respectively, which were significantly higher than levels in the overlying water column. Average diffusive flux from sediment to water is 1642 and 36 ng/m2/day for THg and MeHg. The spatial distribution of THg in pore water from upstream to downstream showed the same trend as the sediment, but MeHg in pore water did not show a declining pattern with distance from the GOCP. These results suggested that sediments experienced serious contamination of Hg, and the contaminated sediment is an important Hg contamination source to the overlying water.  相似文献
7.
 以目前国内设计地震烈度最大的水电站工程——大岗山坝肩边坡工程为实例,根据规范,选用拟静力法对坝肩边坡地震工况下的稳定性进行分析,并对该方法进行相应改进。基于合理的边坡岩体参数、锚固参数和地震参数,对坡体在不同地震加速度下的应力、应变、塑性区及锚索应力进行研究。指出不同剖面地质条件下,不同烈度下边坡关键点位移随边坡高度的变化规律,同时得到不同剖面地震作用的主要影响区域(敏感区域)和地震中塑性区随地震加速度的演化规律,提出相应滑移模式,为支护提供依据。分析认为,考虑50 a超越概率5%的地震加速度时,边坡的V类岩体和表面坡积物及岩脉γL5,γL6,XL316–1,XL9–15,β6处有较大塑性区,并呈贯通趋势。分析指出V类岩体分层线及岩脉XL316–1,XL9–15对岩坡稳定性有着重要的影响,建议调整V类岩体参数并进一步查明岩脉XL316–1,XL9–15的分布情况及连通率。  相似文献
8.
光照重力坝坝基断层影响及处理的三维数值模拟   总被引:5,自引:0,他引:5       下载免费PDF全文
200m级光照重力坝坝踵和坝趾分别存在较大规模的断层,为了分析和评价断层对重力坝应力位移和坝基稳定性的影响,以及建坝后由于围压变化导致的断层变形模量提高对坝体的影响,对重力坝典型坝段和坝基岩体的联合作用进行三维数值模拟。对两条断层分别进行浮值分析,用强度储备系数法计算受断层影响的坝基安全稳定性,并分别模拟对两条断层进行的不同方式加固处理措施进行模拟。研究结果表明,位于坝趾的F2断层对坝体应力位移状态影响较大,也是坝基稳定性的控制性因素之一,在进行固结灌浆处理提高强度后,不仅可以提高坝基稳定性,而且可使坝体应力状态得到改善。位于坝踵的F1断层开挖并回填混凝土处理不宜过深。同时,建坝后围压变化导致断层变形模量的提高对于坝体应力控制是有利的。  相似文献
9.
Mercury pollution in Guizhou, southwestern China - an overview   总被引:4,自引:0,他引:4  
Mercury (Hg) is a global pollutant and poses a worldwide concern due to its high toxicity. Guizhou province is recognized as a heavily Hg-polluted area in China due to both the special geochemical background and human activities. Here an integrated overview of current knowledge on the behavior of Hg in environments, as well as human health risk with respect to Hg contaminations in Guizhou was presented. Two key anthropogenic Hg emission sources in Guizhou were coal combustion and metals smelting, which dominantly contributed to the high levels of Hg in local ecosystems and high fluxes of Hg deposition. The annual Hg emission from anthropogenic sources ranged between 22.6 and 55.5 t, which was about 6.3–10.3% of current total Hg emissions in China. Meanwhile, Hg Hg-enriched soil in the province serves an important natural Hg emission source to the ambient air. The local environment of Hg mining and zinc smelting areas are seriously contaminated with Hg. It is demonstrated that rice growing in Hg Hg-contaminated soil can accumulate methylmercury (MeHg) to a level to pose health threat to local inhabitants whose staple food is rice. Local inhabitants in Hg mining areas are exposed to Hg through inhalation of Hg vapor and consumption of rice with high level of MeHg. Rice intake is indeed the main MeHg exposure pathway to local inhabitants in Hg mining areas in Guizhou, which is contrary to the general point of view that fish and fish products are the main pathway of MeHg exposure to humans.  相似文献
10.
某水电站右岸坝肩岩体受断层切割,稳定性较差,成为工程安全的一大控制性因素。为研究其稳定性,对受断层切割的拱坝坝肩岩体进行了拱坝和坝肩岩体联合作用的三维非线性数值模拟。模型用点安全系数法和超水荷载法,研究坝肩岩体的稳定性,并对起控制性作用的断层进行了加固模拟,分析了加固措施对坝肩岩体安全的影响。研究结果表明:对断层采取工程加固措施后,稳定性有了明显提高,为工程建设提供了有意义的参考。  相似文献
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