全文获取类型
收费全文 | 23篇 |
免费 | 8篇 |
国内免费 | 12篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 6篇 |
地球物理 | 3篇 |
地质学 | 14篇 |
海洋学 | 10篇 |
综合类 | 3篇 |
自然地理 | 3篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 3篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2014年 | 4篇 |
2013年 | 1篇 |
2011年 | 3篇 |
2010年 | 2篇 |
2009年 | 3篇 |
2007年 | 1篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2000年 | 1篇 |
1998年 | 1篇 |
1995年 | 1篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
排序方式: 共有43条查询结果,搜索用时 218 毫秒
1.
本文利用取自浙江椒江河口3个未扰动柱状沉积物样,进行了孔隙水化学测试、固相沉积物的活性分量与黄铁矿分量的分级提取和测试,结果表明:Hg主要以黄铁矿态形式存在于沉积物中。As在有机碳较高的河口区潮上带和沉积速率较慢的潮下带主要以黄铁矿形态存在[DTMP(degree of trace metal pyritization,痕量元素黄铁矿矿化程度)〉50%)],而在中潮带As的黄铁矿矿化程度略低(DTMP均值为40.99%),研究区DOP(Fe的黄铁矿矿化程度)值普遍较低(〈35%),Mn-DTMP低于3.32%。从而揭示了浙江椒江河口沉积物在数厘米以下,毒性痕量元素Hg和As被高度黄铁矿矿化的规律性,并指出在遇有海事活动或风暴潮事件对海底沉积物进行扰动时,河口沉积物与充氧的海水反应,高度黄铁矿矿化的痕量元素会转变成活性态,从而导致近海生态系统的毒性事件。 相似文献
2.
3.
Jiankui?Shi?Email author Zhenxing?Liu Zhang?T.?L. Jianshan?Guo Manlian?Zhang Sheping?Shang Xigui?Luo 《中国科学D辑(英文版)》2003,46(10):986-993
Based on satellite observation data, using dynamics equation, the ionospheric O+ ion’s distribution in the synchronous altitude region for different geomagnetic activity indexK
p is studied by theoretical modeling and numerical analyzing, and semi-empirical models for the O+ ion’s density and flux versus longitude in the synchronous altitude region for differentK
p
are given. The main results show that in the synchronous altitude region: (i) The O+ ion’s density and flux in day-side are larger than those in nightside. (ii) With longitude changing, the higher the geomagnetic
activity indexK
p
is, the higher the O+ ion’s density and flux, and their variation amplitude will be. The O+ ion’s density and flux whenK
p ≥ 6 will be about ten times as great as that whenK
p
= 0. (iii) WhenK
p
= 0 orK
p ≥ 6, the O+ ion’s density reaches maximum at longitudes 120° and 240° respectively, and minimum in the magnetotail. WhenK
p
= 3−5, the O+ ion’s density gets to maximum at longitude 0°, and minimum in the magnetotail. However, the O+ ion’s flux reaches maximum at longitude 120° and 240° respectively, and minimum in the magnetotail for anyK
p
value. 相似文献
4.
PAH concentrations of 61 surface soil samples collected from the Yellow River Delta (YRD), China were measured to determine occurrence levels, sources, and potential toxicological significance of PAHs. The total concentrations of ∑PAHs ranged from 27 to 753 ng/g d.w., with a mean of 118 ± 132 ng/g. The highest concentrations was found in the mid-southern part of the YRD (753 ng/g), which was associated with the oil exploration. The ratios indicated that the PAHs throughout the YRD were mostly of pyrogenic origin; while various sites in mid-southern part in the region were derived mainly from the petrogenic sources. Multivariate statistical analyses supported that the PAHs in surface soils of the YRD were principally from the coal and biomass combustion, petroleum spills, and/or vehicular emissions. The toxic assessment suggested that the PAHs in soils were at low potential of ecotoxicological contamination level for the YRD. 相似文献
5.
Siyuan Ye Edward A. Laws Xigui Ding Hongming Yuan Guangming Zhao Jin Wang 《Environmental Earth Sciences》2011,64(6):1641-1646
Samples of porewater and the edible tissue of mottled clams, Ruditapes variegatus, were collected simultaneously at each of 12 stations from Jiaozhou Bay near Qingdao, China, in June of 2003. Chemical analysis
focused on trace metals and major elements. Porewater concentrations of Cd, Cr, Pb, and Zn were distributed in a bimodal fashion
among the 12 stations, with mean concentrations at six of the stations being 8–32 times mean values at the other six stations.
The concentrations of the same metals in clams were remarkably similar among stations, the coefficients of variation being
only 12–37%. Calculations performed with the computer program PHREEQC indicated that Pb and Cr in porewater were present only
in the +2 and +3 states, respectively, and because dissolved Cd and Zn exist only in the +2 state, the bimodal distribution
of these four metals likely reflects secondary effects associated with their scavenging by Fe and/or Mn under oxidizing conditions
and subsequent dissolution in the reducing environment of the porewaters. Consistent with this hypothesis is the fact that
the distribution of high and low metal concentrations was closely correlated with the granularity of the sediment, with lower
metal concentrations associated with relatively coarse sediment. Comparison of published biological concentration factors
with the ratios of metal concentrations in the clams to porewater metal concentrations indicated that the porewaters were
not the primary sources of the metals in the clams. Mixing processes in the bay likely account for the rather uniform concentrations
of metals in clam tissue. 相似文献
6.
7.
8.
湖北省休闲农业示范点空间格局及影响因素研究 总被引:1,自引:0,他引:1
运用GIS空间分析方法,对湖北省休闲农业示范点的空间分布特征及影响因素进行了研究。结果表明:湖北省休闲农业示范点为集聚型分布态势,空间差异明显;总体呈"散点状与组团状"分布特征,集中于鄂东和鄂中地区,且主要沿公路、铁路等交通干道及城市周边分布;其空间分布密度具有多中心集群分布趋势,表现出"大分散、小集聚"的分布格局;其空间分布具有显著的自相关性,规模相似地区在空间上趋于集聚,热点区与冷点区呈现出"面状"分布特征,其中,热点区主要分布在荆门、孝感等鄂中地区和武汉,冷点区主要分布在宜昌、恩施、神农架等鄂西地区和鄂东北地区。相关分析得出,农业水平、人口规模、交通设施和资源禀赋是影响湖北省休闲农业示范点空间分布的主要因素。 相似文献
9.