全文获取类型
收费全文 | 282篇 |
免费 | 6篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 11篇 |
大气科学 | 48篇 |
地球物理 | 39篇 |
地质学 | 137篇 |
海洋学 | 11篇 |
天文学 | 23篇 |
综合类 | 6篇 |
自然地理 | 14篇 |
出版年
2022年 | 4篇 |
2021年 | 2篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 10篇 |
2015年 | 7篇 |
2014年 | 10篇 |
2013年 | 19篇 |
2012年 | 7篇 |
2011年 | 10篇 |
2010年 | 15篇 |
2009年 | 10篇 |
2008年 | 10篇 |
2007年 | 6篇 |
2006年 | 12篇 |
2005年 | 11篇 |
2004年 | 7篇 |
2003年 | 10篇 |
2002年 | 11篇 |
2001年 | 6篇 |
2000年 | 8篇 |
1999年 | 7篇 |
1998年 | 9篇 |
1997年 | 6篇 |
1995年 | 2篇 |
1993年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1986年 | 2篇 |
1980年 | 4篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1969年 | 2篇 |
1965年 | 2篇 |
1964年 | 2篇 |
1957年 | 3篇 |
1956年 | 4篇 |
1955年 | 2篇 |
1953年 | 2篇 |
1951年 | 3篇 |
1948年 | 5篇 |
1940年 | 2篇 |
1934年 | 1篇 |
1930年 | 1篇 |
1928年 | 2篇 |
1916年 | 1篇 |
1912年 | 1篇 |
排序方式: 共有289条查询结果,搜索用时 31 毫秒
11.
12.
Inspired by recent significant agricultural yield losses in the eastern China and a missing operational monitoring system, we developed a comprehensive drought monitoring model to better understand the impact of individual key factors contributing to this issue. The resulting model, the ‘Humidity calibrated Drought Condition Index’(HcDCI) was applied for the years 2001 to 2019 in form of a case study to Weihai County, Shandong Province in East China. Design and development are based on a linear ... 相似文献
13.
Seasonal Study of Methane and Nitrous Oxide in the Coastal Waters of the Southern Baltic Sea 总被引:2,自引:0,他引:2
H.W. Bange S. Dahlke R. Ramesh L.-A. Meyer-Reil S. Rapsomanikis M.O. Andreae 《Estuarine, Coastal and Shelf Science》1998,47(6):807-817
Atmospheric and dissolved methane (CH4) and nitrous oxide (N2O) were measured in the unique coastal ecosystem of theBoddenwaters, including the western Oder estuary, (southern Baltic Sea) during five campaigns between 1994 and 1997. The CH4saturations, ranging from 105–15 500%, showed great spatial and temporal variability with maximum values in September and minimum values in December. The N2O saturations were in the range of 91–312% with a maximum in March. Enhanced concentrations of both gases were observed only in the western Oder estuary near the mouth of the Peene River. Thus, we conclude that the distributions of CH4and N2O in the investigatedBoddenwaters are, directly or indirectly, linked to the Peene River runoff and not to the Oder River. Our estimate of the annual CH4emissions from theBoddenwaters to the atmosphere indicates a significant contribution (c. 17%) to the overall CH4emissions from the Baltic Sea. In contrast, theBoddenwaters represent only a small source for atmospheric N2O.CH4production rates estimated from sediment slurry experiments revealed a significant spatial variability and indicated that methanogenic activity was related to acetate consumption in the surface sediment layer. Sedimentary CH4production might depend on different amounts of accumulation of organic material. 相似文献
14.
David L. Finnegan Janet P. Kotra Diane M. Hermann William H. Zoller 《Bulletin of Volcanology》1989,51(2):83-87
A simple system was designed using7LiOH-impregnated filters to collect acidic gases from ambient air and from highly concentrated volcanic plumes or gas streams. These filters were developed for analysis using instrumental neutron activation analysis, but other analytical techniques could be used as well. The sampling system was designed to use a series of 1–3 M7LiOH-impregnated filters to collect high concentrations of acidic gases found in gas plumes of active volcanoes. The filters are quantitative for SO2 and the halide acids when sufficient base is present to neutralize the acidic species. Extremely high concentrations of SO2 may not be collected quantitatively since SO2 is a relatively weak Lewis acid compared to the halide acids. The acidic oxides of Sb, As, and Se were also collected quantitatively. A particle filter preceded the impregnated filters in order to remove particles from the fumes. This system has proven effective under difficult sampling conditions and, since it is portable and light weight, it could be used for many volcanological applications where high levels of acidic gaseous phase species need to be collected. 相似文献
15.
Chemical degradations of coal resins, coal asphaltenes and coal residues have been performed with selective, non-oxidative reagents. The coal comprise samples a rank interval 0.30–1.21 %Rm. Degraded low-molecular-weight compounds were analyzed by GC-MS. The distributions of pentacyclic terpanes, isoprenoids, n-alkanes, acids and alcohols obtained as degradation products illustrate a considerable variability between the macromolecular coal fractions. A structural study on the molecular level of the degraded compounds from coal resins and coal asphaltenes show their potential to generate hydrocarbons during coalification process. 相似文献
16.
Besides systematic instrumental and environmental effects in high-precision levellings and gravimetry, some theoretical problems are decisive in the evaluation and interpretation of recent vertical crustal movements. In view of the increased accuracy of recently developed portable instruments for absolute gravity measurements, some global effects on gravity may no longer be neglected, necessitating additional time-dependent reductions for polar motion effects. Another problem concerns the evaluation of recent vertical crustal movements from repeated geodetic measurements: a rigorous treatment of the problem demands both repeated levellings and gravity measurements; only under additional hypotheses can these limitating prerequisites be eliminated. 相似文献
17.
The OECD soil, which is standardised for use in the sediment toxicity with the midge Chironomus riparius revealed inhibition of the nematode Caenorhabditis elegans in body growth length and egg production of 41.0% and 84%, respectively. 18 formulated sediments were tested to optimise the sediment composition for growth and reproduction of C. elegans. Their components were chosen to simulate native sediments, whereby different quantities and different clay minerals were tested. The mixture that we found to be optimal in our experiments consisted of 5% sphagnum peat, 70% calcitic sand, 0.5% dolomite limestone, 4.5% iron(III) oxide, and a clay combination of 1.5% chlorite and 18.5% aluminium(III) oxide. When applying this mixture to C. riparius, the new formulated sediment improved also growth in comparison to the OECD sediment. 相似文献
18.
19.
Hermann Harder 《International Journal of Earth Sciences》1955,43(2):515-518
Zusammenfassung Sedimentäre Eisenerze können durch Ausflocken von Fe+++haltigen Solen und durch Ausfällen von Fe++haltigen Lösungen gebildet werden. Aus Solen gebildete Erze werden als Begleitelemente Kieselsäure und Aluminium anreichern, während aus Lösungen gebildete Erze manganreicher sind und Kieselsäure und Aluminium zurücktreten. 相似文献
20.