全文获取类型
收费全文 | 51185篇 |
免费 | 421篇 |
国内免费 | 317篇 |
专业分类
测绘学 | 995篇 |
大气科学 | 2572篇 |
地球物理 | 9813篇 |
地质学 | 19547篇 |
海洋学 | 4854篇 |
天文学 | 12246篇 |
综合类 | 131篇 |
自然地理 | 1765篇 |
出版年
2022年 | 577篇 |
2021年 | 858篇 |
2020年 | 896篇 |
2019年 | 1005篇 |
2018年 | 2103篇 |
2017年 | 1914篇 |
2016年 | 2044篇 |
2015年 | 836篇 |
2014年 | 1827篇 |
2013年 | 2793篇 |
2012年 | 2078篇 |
2011年 | 2469篇 |
2010年 | 2318篇 |
2009年 | 2686篇 |
2008年 | 2358篇 |
2007年 | 2622篇 |
2006年 | 2301篇 |
2005年 | 1299篇 |
2004年 | 1214篇 |
2003年 | 1194篇 |
2002年 | 1158篇 |
2001年 | 1129篇 |
2000年 | 936篇 |
1999年 | 693篇 |
1998年 | 706篇 |
1997年 | 735篇 |
1996年 | 549篇 |
1995年 | 573篇 |
1994年 | 535篇 |
1993年 | 433篇 |
1992年 | 449篇 |
1991年 | 428篇 |
1990年 | 477篇 |
1989年 | 421篇 |
1988年 | 388篇 |
1987年 | 409篇 |
1986年 | 336篇 |
1985年 | 463篇 |
1984年 | 468篇 |
1983年 | 453篇 |
1982年 | 432篇 |
1981年 | 387篇 |
1980年 | 395篇 |
1979年 | 347篇 |
1978年 | 378篇 |
1977年 | 320篇 |
1976年 | 287篇 |
1975年 | 293篇 |
1974年 | 274篇 |
1973年 | 344篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Quasi-steady high-temperature current sheets are an energy source during the main or hot phase of solar flares. Such sheets are shown to be stabilized with respect to the tearing instability by a small transverse component of magnetic field existing in the sheets. 相似文献
42.
The joint evolution of organic matter and silica in petroliferous sequences is considered in the terms of the laws of transformation of dispersion systems. The dispersion systems are transformed under conditions of low-temperature solid-phase processes accompanied by the silica phase transition and dehydration that favors the evolution of organic matter. 相似文献
43.
Harpacticoida taxocen diversity in the silty-sandy littoral zone of Kandalaksha Bay of the White Sea
E. S. Chertoprud M. V. Chertoprud D. V. Kondar P. N. Kornev A. A. Udalov 《Oceanology》2006,46(4):492-500
The fauna composition, ecological groups, and life forms of Harpacticoids of soft littoral grounds from 15 sites off the Karelian coast in Kandalaksha Bay of the White Sea were studied. Six types of harpacticoid taxocens with different sets of dominating species are described. On silty sands with clear signs of desalination, the Stenchelia palustris taxocen is common; medium-grained sands are characterized by the Heterolaophonte minuta, Paraleptastacus kliei — Huntemannia jadensis, and Amphiascoides nanus — Scottopsyllus minor taxocens; while on coarse sands, the Ameira parvula and Ameira scotti — Mesochra lilljeborgi taxocens have developed. The diversity of the taxocens is partly explained by the differences in the grain-size composition and salinity at different sites. In addition, groups of various taxocens dwelling on the same type of the sediments were found in different minor bights of the coastline. 相似文献
44.
45.
In this paper the peculiarities of compiled oceanographic data sets, which consist primarily in the presence of some characteristic information as well as in the planned incomplete filling of the files with observations, are discussed. A number of special ways are suggested which essentially improve the packing density of computerized data without applying special archiving algorithms. The effectiveness of these methods has been tested by treating thein situ hydrological/chemical data file compiled in the Black Sea in 1988.Translated by Vladimir A. Puchkin. 相似文献
46.
M. V. Ramana 《Geo-Marine Letters》1986,6(1):1-5
Satellite imagery and offshore magnetic data were analysed to correlate regional tectonic elements on the inner continental
shelf off Konkan and the adjacent Deccan plateau. Three statistically important lineament trends—N-S, WNW-ESE and ENE-WSW—that
prevail on land are correlatable well with the offshore trends. This positive correlation suggests simultaneous deformation.
The major magnetic lineament observed off Jaigad Bay, west coast of India, may be the extension of onshore lineaments. The
correlation of both the offshore and onshore trends indicates that the fracture pattern of the crystalline basement has also
controlled the offshore structural pattern. 相似文献
47.
Trends in emigration from Ireland over time are reviewed. "During the eighteenth and nineteenth centuries overseas migration to the United States and seasonal harvest migration to Britain were the main types of movement, but over the past 100 years the Irish have developed a special affinity for settling in British towns. Although the outflow was halted for a time during the 1970s, when return migration took over, the 1980s have seen a renewal of the exodus. This time, however, the character of the flow has changed from predominantly low-skill construction and factory workers to embrace better-educated emigrants, including many graduates. This shift reflects Ireland's changing position in the international market for labour." 相似文献
48.
49.
50.