全文获取类型
收费全文 | 328篇 |
免费 | 25篇 |
国内免费 | 27篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 48篇 |
地球物理 | 120篇 |
地质学 | 163篇 |
海洋学 | 30篇 |
天文学 | 3篇 |
综合类 | 2篇 |
自然地理 | 12篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2017年 | 6篇 |
2016年 | 17篇 |
2015年 | 6篇 |
2014年 | 9篇 |
2013年 | 8篇 |
2012年 | 12篇 |
2011年 | 12篇 |
2010年 | 21篇 |
2009年 | 18篇 |
2008年 | 21篇 |
2007年 | 18篇 |
2006年 | 18篇 |
2005年 | 15篇 |
2004年 | 17篇 |
2003年 | 14篇 |
2002年 | 6篇 |
2001年 | 20篇 |
2000年 | 21篇 |
1999年 | 15篇 |
1998年 | 19篇 |
1997年 | 16篇 |
1996年 | 11篇 |
1995年 | 6篇 |
1994年 | 7篇 |
1993年 | 9篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有380条查询结果,搜索用时 31 毫秒
91.
大气的严重污染导致雾中溶入SO2。等物质而形成酸雾(AcidFog)。酸雾的研究较少[1~6,8,10]。美国加州南部酸雾pH<3.0,最低1.63,我国仅对贵州的梵净山及四川的峨眉山等地的酸雾进行过研究,其成分多为常量组分[4~6,10]。SO2是大气中重要的污染物,而酸雾中SO2的研究至今未见报道。因此研究雾水中SO2及其他成分具有重要的意义。青岛的6~7月为多雾月份,此时盛行风SSE1,雾多形成于4~8m/s风速时,雾以上午4~8时频率最大,最小频率出现于午后14~16时,青岛海雾最长持续… 相似文献
92.
Several mines in the Witbank coalfield in South Africa are affected by acid mine drainage. This has led to a deterioration
in the water quality in many surface streams. The Loubert Mine is one such mine. Hence, an initial investigation was carried
out to determine the source of acid mine drainage pollution and the associated hydrogeological conditions. The investigation
showed that most of the acid mine drainage is emanating from old opencast workings which have been backfilled. Most of the
water from the backfilled area drains into control reservoirs. Unfortunately their capacity is limited, which means that water
overspills and seeps from them. This water finds its way into a nearby stream, the water of which accordingly has an unacceptably
low pH value and high sulphate content. The proposals advanced to control the problem basically involve inhibiting the amount
of water infiltrating the backfilled opencast area on the one hand and reducing the amount of water entering the control reservoirs
on the other.
Received: 5 March 1997 · Accepted: 17 June 1997 相似文献
93.
为研究温度和盐度对华贵栉孔扇贝免疫相关酶活力的联合效应,采用中心复合设计(CCD)和响应曲面分析法(RSM)进行试验,在实验室条件下研究了温度(19~31℃),盐度(22~38)对华贵栉孔扇贝酸性磷酸酶(ACP)、碱性磷酸酶(AKP)、谷胱甘肽还原酶(GR)三种免疫相关酶活性的联合效应,旨在考察温度与盐度对ACP,AKP和GR活性的影响及华贵栉孔扇贝免疫水平较高时的最佳温度和盐度组合,为华贵栉孔扇贝人工养殖所需条件提供理论基础。结果表明:温度的一次效应和二次效应对ACP,AKP和GR活力影响显著(P0.05);盐度的一次效应和二次效应对ACP,AKP和GR的活力影响显著(P0.05);温度和盐度的交互作用对ACP,AKP和GR活力的影响显著(P0.05)。采用响应曲面法,建立了温度和盐度对华贵栉孔扇贝ACP,AKP和GR活性影响的模型方程,该模型方程决定系数分别为0.986 6,0.981 3和0.957 6(P0.01),预测系数分别为0.934 5,0.888 0和0.738 4,表明该模型可以用于预测华贵栉孔扇贝ACP,AKP和GR活力变化。通过模型优化和验证实验,得到在温度24.30℃、盐度30.55时,ACP和AKP活力达到最小值,分别为170.43,181.74U/mg,而GR活力最大为0.34U/mg,满意度达0.95。 相似文献
94.
The present study investigated the chemical composition of wet atmospheric precipitation in India’s richest coal mining belt.
Total 418 samples were collected on event basis at six sites from July to October in 2003 and May to October in 2004 and analysed
for pH, EC, F−, Cl−, , , Ca2+, Mg2+, Na+, K+ and . The average pH value (5.7) of the rainwater of the investigated area is alkaline in nature. However, the temporal pH variation
showed the alkaline nature during the early phase of monsoonal rainfall but it trends towards acidic during the late and high
rainfall periods. The rainwater chemistry of the region showed high contribution of Ca2+ (47%) and (21%) in cations and (55%) and Cl− (23%) in anionic abundance. The high non seas salt fraction (nss) of Ca2+ (99%) and Mg2+ (96%) suggests crustal source of the ions, while the high nss (96%) and high ratio signifying the impact of anthropogenic sources and the source of the acidity. The ratio of varies from 0.03 to 3.23 with the average value of 0.84 suggesting that Ca2+ and play a major role in neutralization processes. The assessment of the wet ionic deposition rates shows no any specific trend,
however Ca2+ deposition rate was highest followed by and
. 相似文献
95.
The changing chemical composition of cloud water and precipitation in the Western Sudety Mountains are discussed against the background of air-pollution changes in the Black Triangle since the 1980s until September 2004. A marked reduction of sulphur dioxide emissions between the early 1990's and the present (from almost 2 million tons to around 0.2 million tons) has been observed, with a substantial decline of sulphate and hydrogen concentration in cloud water (SO42− from more than 200 to around 70 μmol l− 1; H+ from 150 to 50 μmol l− 1) and precipitation (SO42− from around 80 to 20–30 μmol l− 1; H+ from around 60 to 10–15 μmol l− 1) samples. At some sites, where fog/cloud becomes the major source of pollutants, deposition hot spots are still observed where, for example, nitrogen deposition can exceed 20 times the relevant critical load. The results show that monitoring of cloud water chemistry can be a sensitive indicator of pollutant emissions. 相似文献
96.
97.
Near Eagle Plains, northern Yukon, Canada, acidic Ca-Fe-Mg sulfate waters are discharging year-long from disturbed permafrosted sandstone bedrock overlying pyritiferous black shales. These acidic waters are precipitating gypsum with minor amounts of jarosite-K (Na), schwertmannite and hematite. This mineral assemblage is similar to that observed at Meridiani Planum (and other location on Mars), making this site a valuable analogue for low-temperature sulfate geochemistry and mineral formation on Mars. Stable O-S isotope analysis of the acidic waters near Eagle Plains revealed that the oxygen in the dissolved sulfate is mostly derived from water (ca. 70%), suggesting that the sulfide oxidation process could be in part biomediated (i.e., accelerated by acidophilic Fe-oxidizing bacteria). However, unlike the dissolved sulfate in the waters, the formation of the Ca-Fe-SO4 minerals appears to be purely abiotic. The stable O-S isotope composition of the sulfate minerals is well within the predicted equilibrium range at low temperature, suggesting that they formed through physico-chemical processes (i.e., evaporation or freezing). Low-temperature geochemical modeling with FREZCHEM and PHREEQC suggests that the mineral assemblage at Eagle Plains precipitated mainly through the freezing of Ca-Fe-Mg-SO4 acidic waters, rather than through evaporation during the dry summer season, although the latter is still possible. This suggests that the sulfate mineral assemblage observed on Mars could have also formed under a periglacial-type climate. Considering that the active layer in the zone affected by acid drainage does not freeze-over during winter, the residual talik offers a localized niche environment to support acidophilic microorganisms. Overall, the fact that acid drainage is presently active near Eagle Plains allows the direct observation of the low-temperature geochemical processes responsible for generating acid drainage conditions and precipitation of gypsum, schwertmannite, jarosite-K, jarosite-Na, goethite and hematite. 相似文献
98.
99.
Shuping Bi 《Environmental Geology》2001,40(3):300-304
The aim of this paper was to analyze the processing and transport of aluminum speciation through the terrestrial and aquatic
ecosystems of the Chesapeake Bay landscape. Stream waters were sampled in 14 different streams from the Susquehanna River
watershed to the upper reach of Chesapeake Bay. The basic water quality data were documented and Al speciation was evaluated
by modified MINEQL computer model. It was found that the increase in acidity in some of the stream waters near New York were
closely linked with a marked decline in basic cation concentrations. In these areas, the sum of the toxic forms of Al3+ plus AlOH2+ and Al(OH)2
+ concentrations exceeds the critical level of 5 μmol l–1. A potential threat from aluminum may occur.
Received: 3 January 2000 · Accepted: 21 March 2000 相似文献
100.
介绍了晶安高科污染源的来源、采取的措施及综合治理、利用方法.使废水指标由PH11~12;SS<1000mg/l;CODcr≤200mg/l;氨氮≤200mg/l降到PH6~9;SS<70mg/l;CODcr≤100mg/l;氨氮≤15mg/l;酸雾指标由HCl500~800mg/m3达到小于25~40mg/m3;炉窑烟气由林格曼黑度5,烟尘浓度2700~5191mg/Nm3降到林格曼黑度1,烟尘浓度小于200mg/Nm3;硅渣可生产复合絮凝剂和白炭黑,不仅可改善环境影响,而且可回收盐酸和利用废资源,可给企业带来经济效益. 相似文献