全文获取类型
收费全文 | 414篇 |
免费 | 23篇 |
专业分类
测绘学 | 16篇 |
大气科学 | 18篇 |
地球物理 | 128篇 |
地质学 | 191篇 |
海洋学 | 8篇 |
天文学 | 47篇 |
自然地理 | 29篇 |
出版年
2020年 | 3篇 |
2019年 | 5篇 |
2018年 | 6篇 |
2017年 | 9篇 |
2016年 | 14篇 |
2015年 | 14篇 |
2014年 | 10篇 |
2013年 | 14篇 |
2012年 | 10篇 |
2011年 | 24篇 |
2010年 | 23篇 |
2009年 | 25篇 |
2008年 | 16篇 |
2007年 | 21篇 |
2006年 | 12篇 |
2005年 | 26篇 |
2004年 | 14篇 |
2003年 | 19篇 |
2002年 | 10篇 |
2001年 | 5篇 |
2000年 | 7篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 9篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1986年 | 4篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1979年 | 3篇 |
1976年 | 4篇 |
1974年 | 4篇 |
1964年 | 2篇 |
1962年 | 4篇 |
1961年 | 2篇 |
1960年 | 2篇 |
1959年 | 2篇 |
1958年 | 6篇 |
1956年 | 2篇 |
1953年 | 2篇 |
1951年 | 2篇 |
1950年 | 5篇 |
1949年 | 2篇 |
1948年 | 6篇 |
排序方式: 共有437条查询结果,搜索用时 31 毫秒
31.
32.
Zusammenfassung Am 9. Mai wurde der dritte chinesische Kernwaffenversuch durchgeführt. Als Folge konnte etwa vierzehn Tage nach dem Explosionszeitpunkt in Stuttgart-Hohenheim eine deutliche Zunahme des radioaktiven Befalls festgestellt werden. Für die gewonneuen Niederschlags-, Staub- und Luftfilterproben, sowie für ein Heisses Teilchen wurdent
–(1+x
)-Kurven gemessen, diex-Werte bestimmt und gammaspektrometrisch die Nuklidzusammensetzung untersucht. An den aufgefundenen Nukliddiskriminierungen ist bemerkenswert, dass das Heisse Teilchen eine deutliche95Zr-95 Nb-Anreicherung aufwies.
Summary The results of an investigation of the deposition of nuclear weapon debris from the third Chinese test explosion are discussed.t –(1+x )-curves were measured and the values of the parameterx are presented. The dry and precipitation fallout samples and a hot particle were gammaspectrometrically examined. Fractionation phenomena were studied.相似文献
33.
34.
Fritz Baum 《International Journal of Earth Sciences》1955,44(1):148-167
Zusammenfassung Die Abbiegung der SE-Flanke des Vennsattels zum Westrand der Eifeler N-S-Zone wird von einem Störungsbündel begleitet, das die Achsenflexur zu einem Staffelbruch fortbildete und mehrmals posthum in Tätigkeit trat. Methoden werden entwickelt, um aus der Verstellung der feintektonischen Elemente nicht sichtbare Verwerfungen zu erschließen. 相似文献
35.
Significant population growth over the last three decades, as well as efforts to improve surface-water quality mandated by the Clean Water Act, potentially have had opposing influences on aquatic ecosystems in the U.S. Because historical data on water-quality trends are limited over this time period, we developed a diatom-based transfer function to reconstruct chloride, color, acid neutralizing capacity (ANC), total phosphorus (TP), and pH in 55 Minnesota lakes. The lakes span three different ecoregions, as well as the Twin Cities metropolitan area, and differ in their history of settlement and land use, and in surficial geology, climate, and vegetation. Lakes in the Northern Lakes and Forest ecoregion are nearly pristine, whereas those in the other regions likely are strongly affected by urban or agricultural pollutants. Reconstructions of water-chemistry trends since 1970 suggest that recent human activities have had substantial impacts in both urban and rural areas. Chloride concentrations have increased in many Metro lakes, which may be due to road salts, and phosphorus levels have been steady or rising in agricultural regions. The majority of Metro lakes show some decline in TP, although many of the changes are not statistically significant based on our reconstruction techniques. There is no evidence that atmospheric deposition of sulfate or nitrate has caused acidification or changes in trophic state for remote lakes in the northeastern part of the state. 相似文献
36.
37.
38.
Fritz H. Cramer Maria del Carmen R. Díez 《International Journal of Earth Sciences》1976,65(1):288-290
Palynological analysis of twelve wells shows that the metamorphic gradient of the pre-Mesozoic in the Kasba Tadla Basin of Morocco increases rapidly northwest-, southeast-, and eastward, from the center of the Basin. In the center, the Ordovician may still be releasing mobile hydrocarbons.
The authors gratefully acknowledge support of this project through Grant GF-32510-X from the National Science Foundation, Washington, D.C., U.S.A. 相似文献
Zusammenfassung Eine palynologische Untersuchung von zwölf Bohrungen zeigt, daß der thermale Gradient sich im Premesozoikum des Kasba-Tadla-Beckens in Marokko vom Zentrum des Beckens aus nach Nordwesten, Südosten und Osten schnell vergrößert. Es ist sehr wohl möglich, daß das Ordovizium des Beckenzentrums noch flüssige und gasförmige Kohlenwasserstoffverbindungen abgibt.
Résumé L'analyse palynologique de 12 sondages montre que le gradient métamorphique du pré-Mésozoïque dans le Basin du Kasba Tadla, au Maroc, augmente à partir du centre du Bassin vers le nordouest, le sudest et vers l'est. Il est possible que l'Ordovicien de la partie centrale du Bassin produise encore des hydrocarbures liquides et gaseux.
12 , Kasba Tadla -, - . , .
The authors gratefully acknowledge support of this project through Grant GF-32510-X from the National Science Foundation, Washington, D.C., U.S.A. 相似文献
39.
40.
The morphology of the Alpine and adjacent landscapes is directly related to glacial erosion and associated sediment transport.
Here we report the effects of glacio-hydrologic erosion on bedrock topography in the Swiss Plateau. Specifically, we identify
the presence of subsurface valleys beneath the city of Bern and discuss their genesis. Stratigraphic investigations of more
than 4,000 borehole data within a 430 km2-large area reveal the presence of a network of >200 m-deep and 1,000 m-wide valleys. They are flat floored with steep sided
walls and are filled by Quaternary glacial deposits. The central valley beneath Bern is straight and oriented towards the
NNW, with valley flanks more than 20° steep. The valley bottom has an irregular undulating profile along the thalweg, with
differences between sills and hollows higher than 50–100 m over a reach of 4 km length. Approximately 500 m high bedrock highlands
flank the valley network. The highlands are dissected by up to 80 m-deep and 500 m-broad hanging valleys that currently drain
away from the axis of the main valley. We interpret the valleys beneath the city of Bern to be a tunnel valley network which
originated from subglacial erosion by melt water. The highland valleys served as proglacial meltwater paths and are hanging
with respect to the trunk system, indicating that these incipient highland systems as well as the main gorge beneath Bern
formed by glacial melt water under pressure. 相似文献