全文获取类型
收费全文 | 263篇 |
免费 | 14篇 |
国内免费 | 13篇 |
学科分类
地球科学 | 290篇 |
出版年
2023年 | 5篇 |
2022年 | 7篇 |
2021年 | 8篇 |
2020年 | 9篇 |
2019年 | 12篇 |
2018年 | 20篇 |
2017年 | 13篇 |
2016年 | 15篇 |
2015年 | 11篇 |
2014年 | 13篇 |
2013年 | 15篇 |
2012年 | 12篇 |
2011年 | 11篇 |
2010年 | 21篇 |
2009年 | 8篇 |
2008年 | 13篇 |
2007年 | 14篇 |
2006年 | 17篇 |
2005年 | 6篇 |
2004年 | 10篇 |
2003年 | 8篇 |
2002年 | 7篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1986年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1969年 | 1篇 |
1963年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有290条查询结果,搜索用时 31 毫秒
61.
62.
The food choice of juvenile flounder (Platichthys flesus) and turbot (Scophthalmus maximus) was studied in the northern Baltic Sea during the years 1988, 1989, 1994 and 1995. The diet included organisms from 30 species/taxa in flounder (n = 306) and 10 species/taxa in turbot (n = 41). Flounder 45 mm mainly consumed meiofauna (dominating taxon: Harpacticoida, Copepoda) and larger fish (46–101 mm) consumed macrofauna (dominating taxa: Oligochaeta, Amphipoda and Chironomidae). In terms of biomass, macrofauna dominated for all sizes of flounders, and meiofauna was important only for the smallest fish. A strong seasonal variation could be detected in the diet. In spring, macrofauna dominated for all size classes of fish (only fish > 30 mm were caught in spring), while in summer and autumn meiofauna dominated the diets for fish 45 mm in size. Juvenile turbot (22–88 mm) consumed macrofauna and small fish. Turbot 30 mm consumed mainly amphipods, while > 30 mm turbot consumed mysid shrimps, amphipods and fish.The ontogenetic shift from meio- to macrofauna-sized prey in flounders occurs at a larger fish size in the northern Baltic Sea than reported in other areas, possibly depending on the increased relative importance of meiofauna in the northern Baltic. The seasonal variation in the diet could be due to seasonally changing abundances in the zoobenthos, or for the small fish (1-group, spring), to switching from meio- to macrofauna in order to optimize their energy gain. The 0-group flounders consumed meiofauna for a long period, possibly due to a learning-process or simply due to easy availability of meiofauna. Turbot has a much larger mouth gap than flounders, thus allowing them to consume macrofauna from the beginning of their benthic life. 相似文献
63.
Nina Morgan 《Geology Today》2016,32(4):154-159
Cemeteries and graveyards not only serve as a peaceful place to commemorate the dead. For geologists—whether amateur, student or professional—almost any urban cemetery provides a valuable opportunity to carry out scientific field work at leisure, right on the doorstep, and at no cost. Cemeteries offer an excellent opportunity to examine and study a wide range of stone types in a small space. They also serve as a useful field area for studying rock weathering. 相似文献
64.
Effect of salinity on abundance dynamics and cell size of microalga Corethron hystrix Hensen (Bacillariophyta) were studied. C. hystrix can normally grow within a rather narrow salinity range between 32 and 28‰. The viable cells of this microalga change their morphological characters at a salinity of 24‰. This salinity level probably marks the beginning of cell division restriction, because the general number of cells by the end of the experiment was lower than in the control. The decrease of salinity to 16‰ caused pronounced irreversible morphological changes: cell height increased, chloroplasts compressed, protoplasm became granular, cytoplasm retracted, and spines shortened. 相似文献
65.
66.
67.
68.
Nina Laurie 《Geoforum》2010,41(2):165-167
69.
New seismicity and focal-mechanism data from the area of the Azores Islands, in the Mid-Atlantic Ridge, to the Alboran Sea and the southern part of Spain are presented.As a consequence of the different characters in the focal-mechanism solutions and b-values associated, the area has been divided in four different parts, namely, Mid-Atlantic and Terceira Ridge, Azores—Gibraltar fault, Gulf of Cadiz, Alboran Sea and Betica. The last two form the interaction between the Eurasian and African continental plates.The fracture zone is the locus of very large earthquakes with mechanisms showing a predominant right-lateral horizontal motion. Seismic foci in the continental interaction zone are spread over the whole region with mechanisms changing in character from west to east. It is suggested that this may be consequence of the behaviour of the Spanish Peninsula as a partly independent subplate. In the eastern part of the studied zone, the so-called Alboran plate may be considered as a buffer plate. 相似文献
70.