全文获取类型
收费全文 | 5145篇 |
免费 | 520篇 |
国内免费 | 872篇 |
专业分类
测绘学 | 85篇 |
大气科学 | 630篇 |
地球物理 | 1088篇 |
地质学 | 1066篇 |
海洋学 | 1101篇 |
天文学 | 1709篇 |
综合类 | 216篇 |
自然地理 | 642篇 |
出版年
2024年 | 17篇 |
2023年 | 43篇 |
2022年 | 99篇 |
2021年 | 125篇 |
2020年 | 134篇 |
2019年 | 161篇 |
2018年 | 132篇 |
2017年 | 145篇 |
2016年 | 139篇 |
2015年 | 163篇 |
2014年 | 195篇 |
2013年 | 252篇 |
2012年 | 161篇 |
2011年 | 231篇 |
2010年 | 197篇 |
2009年 | 392篇 |
2008年 | 393篇 |
2007年 | 422篇 |
2006年 | 433篇 |
2005年 | 344篇 |
2004年 | 295篇 |
2003年 | 313篇 |
2002年 | 252篇 |
2001年 | 203篇 |
2000年 | 262篇 |
1999年 | 227篇 |
1998年 | 216篇 |
1997年 | 107篇 |
1996年 | 77篇 |
1995年 | 92篇 |
1994年 | 71篇 |
1993年 | 48篇 |
1992年 | 43篇 |
1991年 | 23篇 |
1990年 | 26篇 |
1989年 | 14篇 |
1988年 | 9篇 |
1987年 | 12篇 |
1986年 | 9篇 |
1985年 | 14篇 |
1984年 | 7篇 |
1983年 | 9篇 |
1982年 | 17篇 |
1981年 | 8篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有6537条查询结果,搜索用时 31 毫秒
51.
52.
Mass heterogeneities and convection in the earth's mantle inferred from gravity and core-mantle boundary irregularities 总被引:1,自引:0,他引:1
Mass heterogeneities in the earth's mantle are retrieved from the gravity data and the topography of the core-mantle boundary as well as the topography of the earth's surface. A mantle circulation induced by the heterogeneities is modelled by solving the Stokes problem for incompressible Newtonian fluid. The derived models of mantle motions correlate well with the plate tectonics and point at a close relation between the surface tectonic activity and the processes in the vicinity of the core-mantle boundary. 相似文献
53.
饱和软黏土动力学特性循环扭剪试验研究 总被引:2,自引:0,他引:2
以饱和软黏土的循环扭剪试验研究为基础,阐明不固结不排水条件下饱和软黏土的动力学特性。在循环扭剪和循环三轴两种不同试验应力状态下,通过研究不同围压和不同静、动应力组合下饱和软黏土的应力等效破坏关系和应变等效破坏关系,提出在循环荷载作用下饱和软黏土的循环破坏同样遵循Mises屈服准则,且在Mises屈服准则下,饱和软黏土的循环强度趋于不变量。循环破坏的过程可以等效为一种拟静力弹塑性循环蠕变,建立了饱和软黏土循环累积变形随静荷载、循环荷载以及循环破坏振次之间的关系式。上述结论分别从应力和变形两个方面阐述饱和软黏土的动力学特性,与试验应力状态和围压无关,可以推广到一般应力状态下。 相似文献
54.
Abstract. The consequences of the following episodic phenomena for the pelagic-benthic coupling in the Nordic Seas are illustrated: (1) Advection of water masses between fjords and shelf environments, (2) freshwater run-off and vertical stability, (3) dynamics of the marginal ice zone in the central and northern Barents Sea and the Polar Ocean, (4) drift patterns of sinking particles along the North Norwegian coast, (5) advection of zooplankton into subarctic fjords and the southern Barents Sea, zooplankton overwintering and composition, and (6) transport of organic particulate matter from the Barents Sea shelf. It is shown that physical processes in the north-eastern North Atlantic and Polar Ocean can be strongly variable on time scales of days to decades. They have a significant influence on the dynamics of pelagic-benthic coupling. The physical oceanography influences the vertical and horizontal particle flux not only directly (mixing, advection, up- and down-welling), but also indirectly through its impact on the biota (for example radiation, wind, ice cover, freshwater run-off and overwintering, advection and retention of zooplankton). Understanding pelagic-benthic coupling at high latitudes depends even more on a best possible understanding of the physical oceanography and the time scales involved than elsewhere. 相似文献
55.
56.
Abstract. The secondary production of Spisula subtruncata (somatic production) is calculated in the framework of a benthic monitoring study in a coastal area. The temporal trends of density, biomass and growth increments are examined in the three year-classes present. These are compared to certain physical and chemical parameters. 相似文献
57.
Modelling and forecasting long-term dynamics of Western Baltic macrobenthic fauna in relation to climate signals and environmental change 总被引:1,自引:0,他引:1
Long-term macrobenthos data from Kiel Bight in the Western Baltic collected between 1968 and 2000 have been correlated with the winter NAO index (North Atlantic Oscillation Index) and other environmental data such as temperature, salinity and oxygen content in the bottom water in order to detect systematic patterns related to so far unexplained abiotic signals in the dynamics of zoobenthic species assemblages. The benthos data come from a cluster of five stations (Süderfahrt/ Millionenviertel) in Kiel Bay. Our investigations concentrated on the macrobenthic dynamics with a focus on the number of species m− 2 (species richness). Using logarithms and the time series analysis approach of Box/Jenkins (ARIMA modelling, transfer function modelling) it was shown that species richness was strongly influenced by the winter NAO (adjusted for a linear time trend within the 1968-2000 period) and salinity (with a shift/lag of four years). Bootstrapping experiments (i.e. sampling from the error process) and analysis of prediction power (by means of the one- or more-years leaving-out method) showed that the parameter estimates behaved in a stable way, leading to a relatively robust model. 相似文献
58.
59.
关于南海暖水季节和年际变化的研究 总被引:1,自引:3,他引:1
王启 《中国海洋大学学报(自然科学版)》2003,33(6):821-824
阐述了研究南海暖水的意义 ,综述了关于南海暖水的现状 ,提出了关于南海暖水季节和年际变化方面应该研究的问题 相似文献
60.