全文获取类型
收费全文 | 12409篇 |
免费 | 2784篇 |
国内免费 | 3324篇 |
专业分类
测绘学 | 1123篇 |
大气科学 | 3181篇 |
地球物理 | 4087篇 |
地质学 | 5000篇 |
海洋学 | 2178篇 |
天文学 | 709篇 |
综合类 | 1019篇 |
自然地理 | 1220篇 |
出版年
2024年 | 96篇 |
2023年 | 245篇 |
2022年 | 422篇 |
2021年 | 514篇 |
2020年 | 537篇 |
2019年 | 696篇 |
2018年 | 497篇 |
2017年 | 589篇 |
2016年 | 575篇 |
2015年 | 661篇 |
2014年 | 745篇 |
2013年 | 846篇 |
2012年 | 845篇 |
2011年 | 859篇 |
2010年 | 674篇 |
2009年 | 862篇 |
2008年 | 718篇 |
2007年 | 945篇 |
2006年 | 808篇 |
2005年 | 651篇 |
2004年 | 628篇 |
2003年 | 562篇 |
2002年 | 505篇 |
2001年 | 450篇 |
2000年 | 474篇 |
1999年 | 419篇 |
1998年 | 382篇 |
1997年 | 356篇 |
1996年 | 374篇 |
1995年 | 280篇 |
1994年 | 264篇 |
1993年 | 250篇 |
1992年 | 187篇 |
1991年 | 131篇 |
1990年 | 114篇 |
1989年 | 106篇 |
1988年 | 80篇 |
1987年 | 50篇 |
1986年 | 18篇 |
1985年 | 27篇 |
1984年 | 19篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 1篇 |
1954年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
41.
TOGA—COARE强化观测期间,对赤道暖池区海流作了多种方法、多层次的观测;根据美国释放的漂流浮标不同时刻位置的资料,分别对赤道及其南、北海域的表层漂流状况作了计算分析,指出:从1°N向北存在单一的北向流;从1°N~1°S这个近赤道区域内为东向流;1°N~2°S区域为过渡区,以东向流为主,个别浮标出现涡旋状运动。2°S以南为一反时针运动的大涡旋。 相似文献
42.
Ana P. Mucha M. Teresa S. D. Vasconcelos Adriano A. Bordalo 《Estuarine, Coastal and Shelf Science》2004,59(4):663
Vertical distribution (0–15 cm) of the macrobenthic community and its relationships to natural sediment characteristics and trace metal contents and bioavailability were studied at five locations in the lower Douro estuary, Portugal. An analysis of vertical metal distribution, for the interpretation of anthropogenic impact on the estuarine sediments, was also investigated. Sediment characterisation included organic matter, grain size, metals (Al, Fe, Cu, Pb, Cr, Ni, Cd, Zn and Mn), acid volatile sulphide (AVS) and simultaneously extracted metals (SEM). The macrobenthic community had low diversity (14 species), was dominated by small size opportunists and seemed to be controlled mainly by natural factors such as grain size distribution, Al and Fe contents and sediment depth. The vertically heterogeneous distribution of macrobenthic community appears to affect redox status of the sediments and consequently metal bioavailability. Despite anthropogenic contamination in terms of Zn, Cu, Pb, Cr and Ni having already been detected in the north bank, the analysis of vertical distribution was essential for the identification of current anthropogenic contamination in terms of Zn, Pb and Cd in the south bank. 相似文献
43.
对冲绳海槽1984-1990年的实测热流值,利用数字滤波方法计算,得到反映该区深部地壳热状态的区域热流值为80-160mW/m^2,用B样条函数法对其作数值模拟,计算出海槽地温场模式,并以此研究冲绳海槽海底高热流的形成机制,得出冲绳海槽热流值的区域性变化与綦中地质构造格局呈正相关,高热流是该区现代构造活动所致,其明显特征是地壳减薄,地幔上拱等结论。 相似文献
44.
好望角附近海域春季大风的几种主要形势分析 总被引:1,自引:1,他引:1
通过普查和分析,概括出了春季好望角附近海域三种主要大风出现时的模型图,并以一个月中逐日4次船舶测风报告为例,分析了好望角大风的某些主要特征。 相似文献
45.
9012号热带气旋维持的卫星云图和垂直结构特征分析 总被引:2,自引:0,他引:2
本文根据卫星云图的演变和常规天气分析相结合,对9012号热带气旋登陆后维持水消的成因进行了分析。指出该热带气旋经久不消的重要原因为其西南侧对流云团和东北侧高空槽前对流云带与热带气旋云系相衔接在中低层东北气流引导下卷入,热带气旋内部的两条云带的维持,以及利有的环流条件。 相似文献
46.
47.
A probability density function of surface elevation is obtained through improvement of the method introduced by Cieslikiewicz who employed the maximum entropy principle to investigate the surface elevation distribution. The density function can be easily extended to higher order according to demand and is non-negative everywhere, satisfying the basic behavior of the probability. Moreover because the distribution is derived without any assumption about sea waves, it is found from comparison with several accepted distributions that the new form of distribution can be applied in a wider range of wave conditions. In addition, the density function can be used to fit some observed distributions of surface vertical acceleration although something remains unsolved. 相似文献
48.
提出用B样条函数求解曲线、曲面上重磁位场的向上延拓,水平、垂向导数计算,磁异常分量互换的方法。该方法的特点是:原理简明,程序通用性强,计算精度高。 相似文献
49.
50.
Wind and waves are major forces affecting the geomorphology and biota in coastal areas. We present a generally applicable method for measuring and calculating fetch length, fetch direction and wave exposure. Fetch length and direction, measured by geographic information system-based methods, are used along with wind direction and wind speed data to estimate wave height and period by applying forecasting curves. The apparent power of waves approaching the shore, used as a proxy for wave exposure, is then calculated by a linear wave model. We demonstrate our method by calculating fetch lengths and wave exposure indices for five areas with varying exposure levels and types of meteorological conditions in the Finnish Archipelago Sea, situated in the northern Baltic Sea. This method is a rapid and accurate means of estimating exposure, and is especially applicable in areas with geomorphologically varying and complicated shorelines. We expect that our method will be useful in several fields, such as basic biogeographical and biodiversity research, as well as coastal land-use planning and management. 相似文献