全文获取类型
收费全文 | 197篇 |
免费 | 2篇 |
国内免费 | 7篇 |
专业分类
测绘学 | 22篇 |
大气科学 | 7篇 |
地球物理 | 83篇 |
地质学 | 56篇 |
海洋学 | 20篇 |
天文学 | 7篇 |
综合类 | 1篇 |
自然地理 | 10篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 7篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2014年 | 1篇 |
2013年 | 4篇 |
2012年 | 9篇 |
2011年 | 9篇 |
2010年 | 1篇 |
2008年 | 11篇 |
2007年 | 10篇 |
2006年 | 16篇 |
2005年 | 5篇 |
2004年 | 7篇 |
2003年 | 7篇 |
2002年 | 6篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 11篇 |
1991年 | 8篇 |
1990年 | 10篇 |
1989年 | 12篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1981年 | 3篇 |
排序方式: 共有206条查询结果,搜索用时 31 毫秒
41.
Concentrations of polycyclic aromatic hydrocarbons were determined in species of commercial fish and lobsters following an oil-spill just off the protected Madagascan coastline. Samples were collected along the coastline within and outside the affected area. Summed PAH concentrations ranged from 1.9 μg kg−1 to 63 μg kg−1 wet weight, but with no higher molecular weight PAHs (>202 Da) being detected. All concentrations of benzo[a]pyrene, benz[a]anthracene and dibenz[a,h]anthracene were <0.1 μg kg−1 wet weight, well within the EU and UK set limits for the protection of human health. Additionally, samples were calculated as the benzo[a]pyrene toxic equivalency quotient (TEQ) and found to be well below the level of concern in relation to health of human consumers. Evaluation of the biota PAH data indicated the origin of PAH was predominantly petrogenic with >80% arising from oil sources. Profile studies indicate a low-level multisource petrogenic contamination probably representing a pre-spill background for the area. 相似文献
42.
Guitart C Slattery M Ankisetty S Radwan M Ross SJ Letcher RJ Reddy CM 《Marine pollution bulletin》2011,62(3):631-636
Considerable debate surrounds the sources of oxygenated polybrominated diphenyl ethers (O-PBDEs) in wildlife as to whether they are naturally produced or result from anthropogenic industrial activities. Natural radiocarbon (14C) abundance has proven to be a powerful tool to address this problem as recently biosynthesized compounds contain contemporary (i.e. modern) amounts of atmospheric radiocarbon; whereas industrial chemicals, mostly produced from fossil fuels, contain no detectable 14C. However, few compounds isolated from organisms have been analyzed for their radiocarbon content. To provide a baseline, we analyzed the 14C content of four O-PBDEs. These compounds, 6-OH-BDE47, 2′-OH-BDE68, 2′,6-diOH-BDE159, and a recently identified compound, 2′-MeO-6-OH-BDE120, were isolated from the tropical marine sponges Dysidea granulosa and Lendenfeldia dendyi. The modern radiocarbon content of their chemical structures (i.e. diphenyl ethers, C12H22O) indicates that they are naturally produced. This adds to a growing baseline on, at least, the sources of these unusual compounds. 相似文献
43.
Concentrations of polycyclic aromatic hydrocarbons have been determined in sediments, mussels and crustacea in the vicinity of a former gasworks site by Shoreham Harbour, UK. Very high concentrations of PAH were found in the substrate, an ash-like material deposited on the former gasworks site, which exhibited a profile consistent with the major source of contamination being coal or coke tar produced during the period of gas production at the site. Elevated PAH concentrations were also found in mussels both from the beach below the former gasworks site, and from sites further to the east in Portslade and Hove. The significance of these concentrations were assessed using an approach which involved the calculation of benzo[a]pyrene equivalent conoentrations (BaPEs), summing concentrations of individual PAH on the basis of their comparative potency as carcinogens. BaPE ranged from values of, or close to, zero for crustacea, to 336 microg kg(-1) wet weight in mussels from Southwick Beach. The contaminated mussels are not exploited commercially but may be taken by casual gatherers, and notices have been posted to warn potential consumers. 相似文献
44.
45.
46.
以一切可利用的实验数据为基础的H20-CO2-CH4-N2-C2H6流体系统的网格状化合物稳定条件已建成为模型,对于包含在网格状化合物模型中的一些参数,如逸度气体在水中的溶解热度及热动力常数,可根据对它们最准确的计算结果估计纯净的CO2、CH4、N2、C2H6等气体水合物最适合的Kihara参数,对于CO2-CH4,CH4-C2H6等混合型气体水合物,引入过量吉布斯自由能函数并得到一个与实验数据非常吻合的结果,过量吉布斯自由能被描述为一个修正过的Margules方程,它取决于克分子量和温度。 相似文献
47.
48.
The authors use 1981 census data to create a cartogram showing the counties of New Zealand in proportion to their population. 相似文献
49.
50.