全文获取类型
收费全文 | 367篇 |
免费 | 13篇 |
国内免费 | 8篇 |
专业分类
大气科学 | 3篇 |
地球物理 | 118篇 |
地质学 | 80篇 |
海洋学 | 32篇 |
天文学 | 151篇 |
综合类 | 1篇 |
自然地理 | 3篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 6篇 |
2016年 | 8篇 |
2015年 | 1篇 |
2014年 | 11篇 |
2013年 | 13篇 |
2012年 | 1篇 |
2011年 | 52篇 |
2010年 | 46篇 |
2009年 | 30篇 |
2008年 | 41篇 |
2007年 | 30篇 |
2006年 | 19篇 |
2005年 | 14篇 |
2004年 | 23篇 |
2003年 | 16篇 |
2002年 | 19篇 |
2001年 | 6篇 |
2000年 | 3篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1980年 | 1篇 |
排序方式: 共有388条查询结果,搜索用时 15 毫秒
111.
利用河北怀来4井1990年至2002年的水汞观测资料,对怀来4井汞量异常进行了分析,分析结果显示,怀来4井水汞异常与地震的对应率较好,1990年以来,其异常对于测点监测范围的有感地震及中小地震和距离测点较远的范围内发生的5.0级以上地震有很高的对应率。 相似文献
112.
贵州万山汞矿尾矿堆及地表水的环境地球化学特征 总被引:5,自引:0,他引:5
对贵州万山汞矿区尾渣堆(主要为炉渣组成)、地表水及河流沉淀物的汞迁移进行了研究。由于赋矿岩石为白云岩,高温煅烧的炉渣中含CaO等碱性物质,炉渣的风化作用释放出汞以及碱性水.流经尾渣堆的地表水碱性强(pH10.6-11.8)、电导率高,且具有明显不同的主要离子组成.万山汞矿矿石单一,主要为辰砂,其他矿石极少,因此炉渣及其渗滤水中除汞外的重金属含量很低.尾渣堆中的汞及碱性物质是对周围环境的主要威胁.在尾渣堆下游汞含量很快降低,约300n,范围内水中的溶解汞从300—1900,ng/L降至72ng/L,而且水的碱性也被中和.但是,由于尾渣堆中的汞及碱性物质含量高,尾渣堆的长时间风化及水流的溶解会将大量汞搬运到周围的土壤及水体并对生物产生不利影响. 相似文献
113.
滇西水汞观测的地震短临预报指标 总被引:2,自引:0,他引:2
通过对滇西下关,弥渡,洱源江干,洱源滇20#,保山等水汞在12次地震前异常特征分析的结果表明,汞异常形态清楚,异常变化率大,单项以多点突跳为主,整体以群体突跳为主,短临异常持续时间数十天,地震多数发生在首次异常后23-111天的88天之内;大震存在中短期异常和时空演变规律,对应地震范围受震中距和地震构造的双重制约,似乎与孕震能大小和传播途径有关,大体存在的异常持续时间越长,异常数量越多,震级越大的 相似文献
114.
氡,汞测量用于断裂活动性和分段的研究 总被引:25,自引:1,他引:25
作者首先给出海原活动断裂带从边沟至硝口的3条较长次级剪切断层,干盐池拉分盆地和边沟推挤构造区内的断层,以及尾端挤压构造区内的六盘山东麓逆断层的气氡,气汞浓度测量结果,然后分析了断层气浓度与断层活动性之间的关系,研究结果表明,测试条件大体一致的基础上,气氡,气汞浓度与断层活动性之间有着明显的对应关系,从而证明了断层气测量方法对于活断层分段和活动性研究是一种有效的手段。 相似文献
115.
本文在介绍一种新的土壤汞量测量找矿方法的同时,着重用大量的实测数据阐明汞在460铀矿床上的分布特征。汞在该矿床上部“黑矿”中的平均含量高达11430ppb,最高达193800ppb,而一般岩石中的汞含量只有数十至数百个ppb。通过对铀矿石及其主岩中的汞的热释谱分析,发现释汞主峰温度在350℃以上的中温、高温相态汞与铀矿化关系密切。铀矿床上部土壤汞晕规模大(550×350m~2),平均含量可达563ppb,最高达6080ppb,平均衬度16,最高达174。汞含量随着采样深度的加深而升高。在矿床外围测出了相似的汞晕,并进行了成矿预测。上述成果已用于生产。 相似文献
116.
Sean C Solomon Author Vitae 《Earth and Planetary Science Letters》2003,216(4):441-455
The planet Mercury, a difficult object for study by astronomical observation and spacecraft exploration alike, poses multiple challenges to our general understanding of the inner planets. Mercury’s anomalously high uncompressed density implies a metal fraction of 60% or more by mass, an extreme outcome of planetary formational processes common to the inner solar system. Whether that outcome was the result of chemical gradients in the early solar nebula or removal by impact or vaporization of most of the silicate shell from a differentiated protoplanet can potentially be distinguished on the basis of the chemical composition of the present crust. Our understanding of the geological evolution of Mercury and how it fits within the known histories of the other terrestrial planets is restricted by the limited coverage and resolution of imaging by the only spacecraft to have visited the planet. The role of volcanism in Mercury’s geological history remains uncertain, and the dominant tectonic structures are lobate scarps interpreted as recording an extended episode of planetary contraction, issues that require global imaging to be fully examined. That Mercury has retained a global magnetic field when larger terrestrial planets have not stretches the limits of standard hydromagnetic dynamo theory and has led to proposals for a fossil field or for exotic dynamo scenarios. Hypotheses for field generation can be distinguished on the basis of the geometry of Mercury’s internal field, and the existence and size of a fluid outer core on Mercury can be ascertained from measurements of the planet’s spin axis orientation and gravity field and the amplitude of Mercury’s forced librations. The nature of Mercury’s polar deposits, suggested to consist of volatile material cold-trapped on the permanently shadowed floors of high-latitude impact craters, can be tested by remote sensing of the composition of Mercury’s surface and polar atmosphere. The extremely dynamic exosphere, which includes a number of species derived from Mercury’s surface, offers a novel laboratory for exploring the nature of the complex and changing interactions among the solar wind, a small magnetosphere, and a solid planet. Recent ground-based astronomical measurements and several new theoretical developments set the stage for the in-depth exploration of Mercury by two spacecraft missions within the coming decade. 相似文献
117.
Clausthalite in coal 总被引:2,自引:0,他引:2
A lead selenide mineral, tentatively identified as clausthalite (PbSe) based on optical microscopy, scanning electron microscopy with energy-dispersive X-ray (EDAX), electron microprobe, and scanning proton microprobe (SPM), has been described in a number of coals. While clausthalite has been mentioned as a possible source of Se in coal, it is present in such small quantities and sizes, that the mineral identification has not been absolutely confirmed. The mineral specimens examined in this study would contribute, not only to the Pb and Se concentrations in the coal, but also, in at least one case, to Hg concentrations. 相似文献
118.
Olivier Rozenbaum Luc Barbanson Fabrice Muller Ary Bruand 《Comptes Rendus Geoscience》2008,340(6):345-355
Stone substitution is a conventional operation during heritage buildings’ restoration, but becomes problematic for architects and restorers when the quarry is mined out. The compatibility of the substitution stones with the original ones has been for long mainly based on the aesthetical aspect, this resulting too often in a patchwork of original and substitution stones with different patina after several years because of differences of properties. In this study, the objective is to show how substitution stones can be selected by combining aesthetic criteria and stones properties that are relevant for analyzing their compatibility. A couple of French limestones with their potential substitution stones were selected for the study. Our results showed that potential substitution stones selected on their aesthetic criteria require to be rejected because of their differences of physical properties. On the other hand, our results showed also the possibility to select substitution stones with satisfactory aesthetic aspect and properties that enable to expect a satisfactory compatibility with the original stone. 相似文献
119.
An integrated geochemical and toxicological assessment of environmental mercury contamination and attendant human exposure
in Honda Bay, Palawan was undertaken in 1995 following a nationally reported pollution scare centered on a coastal jetty,
Sitio Honda Bay, constructed using approximately 1 million tons of tailings and beneficiation waste from a cinnabar mine.
Mercury (Hg) data for marine and fluvial sediments, fish tissues and human hair indicate that the toxicological hazard is
considerably lower than initially reported by state environment and health officials. Typical Hg concentrations in surficial
Honda Bay sediments were found to lie within the global background range (<60 μg/kg). Downcore profiles provide no evidence
of enhanced Hg fluxes coincident with the onset of mining and/or coastal tailings disposal. The mean and median Hg concentrations
recorded in tissues of six species of Honda Bay fish are compliant with thresholds established by the US Environmental Protection
Agency (US-EPA) for marketable stocks. Earlier reports of 'Minamata range' Hg concentrations in fish and shellfish from Honda
Bay remain unsubstantiated. Geochemical analyses of samples of the Sitio Honda Bay substrate have confirmed the prevalence
of solid-phase Hg concentrations to ca. 340 mg/kg. The speciation of Hg is, however, dominated by secondary oxides of low
bioavailability. The mean Hg concentration in hair from Sitio Honda Bay residents (4.41 mg/kg) was found to be statistically
analogous to that for a neighbouring coastal community unimpacted by the coastal disposal of mine waste. A negligible residential
exposure factor is thus inferred for the former. Relatively high hair Hg burdens prevail throughout the coastal Honda Bay
population, consistent with significant methyl Hg ingestion through daily fish consumption. The data presented provide no
environmental or toxicological justification for immediate remedial action.
Received: 14 May 1998/Accepted: 1 September 1998 相似文献
120.
Total mercury (Hg) was measured in coastal fishes from Southern New England (RI, USA), and Hg exposure was estimated for anglers and family members that consumed these resources. Fish Hg was positively related to total length (n = 2028 across 7 fish species), and interspecies differences were evident among legally harvestable fish. Many recreational anglers and their families experienced excessively high Hg exposure rates, which was attributed to the enriched Hg content of frequently consumed fishes. Specifically, 51.5% of participants in this study had Hg exposures exceeding the US EPA reference dose, including 50.0% of women of childbearing years. These results are noteworthy given that Hg neurotoxicity occurs in adults and children from direct and prenatal low-dose exposure. Moreover, this study underscores the need for geographic-specific research that accounts for small-scale spatial variations in fish Hg and dietary habits of at-risk human populations. 相似文献