全文获取类型
收费全文 | 33517篇 |
免费 | 4811篇 |
国内免费 | 6647篇 |
专业分类
测绘学 | 8958篇 |
大气科学 | 4909篇 |
地球物理 | 6210篇 |
地质学 | 12208篇 |
海洋学 | 4217篇 |
天文学 | 296篇 |
综合类 | 2858篇 |
自然地理 | 5319篇 |
出版年
2024年 | 94篇 |
2023年 | 320篇 |
2022年 | 960篇 |
2021年 | 1134篇 |
2020年 | 1303篇 |
2019年 | 1577篇 |
2018年 | 1240篇 |
2017年 | 1646篇 |
2016年 | 1638篇 |
2015年 | 1842篇 |
2014年 | 1982篇 |
2013年 | 2504篇 |
2012年 | 2215篇 |
2011年 | 2286篇 |
2010年 | 1797篇 |
2009年 | 2135篇 |
2008年 | 2286篇 |
2007年 | 2347篇 |
2006年 | 2167篇 |
2005年 | 1907篇 |
2004年 | 1719篇 |
2003年 | 1482篇 |
2002年 | 1363篇 |
2001年 | 1083篇 |
2000年 | 1009篇 |
1999年 | 852篇 |
1998年 | 732篇 |
1997年 | 639篇 |
1996年 | 562篇 |
1995年 | 476篇 |
1994年 | 419篇 |
1993年 | 354篇 |
1992年 | 219篇 |
1991年 | 185篇 |
1990年 | 125篇 |
1989年 | 95篇 |
1988年 | 88篇 |
1987年 | 54篇 |
1986年 | 29篇 |
1985年 | 31篇 |
1984年 | 15篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1954年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 20 毫秒
991.
A two-layer primitive equation model is developed in this paper. The capabilities of this model aretested by the use of multiyearly averaged January and July sea surface level pressure fields and windfields which can be diagnosed from the pressure fields. The results show that the ocean surface currentsand undercurrents in the second layer driven by the sea surface wind and the sea surface pressure areclose to the observation. The results are also compared with that of the IAP OGCM and the OSUOGCM. 相似文献
992.
In this paper we document the correlationship between sea surface temperature(SST) and low level-winds such as sea level wind and 850 hPa wind in the South China Sea(SCS) based on COADS(1958-1987) and ECMWF objective analysis data(1973-1986).Further statistical analyses tell us that there is a fixed SCS basin mode for variations both of SST and low-level winds in the region on the interannual time scale due to air-sea interactions.A simplified,coupled model that is designed following the McCreary and Anderson's(1985) model and includes the feedback between the upper ocean and the circulation of East Asian monsoon demonstrates an interannual oscillation in the coupled air-sea system,which is similar to the observations in the SCS. 相似文献
993.
A coupled model,which is employed to study the dominating factor and key area of El Nino cycle formation,consists of a dynamical ocean model and a statistical atmospheric model.The coupled model with seasonal forcing successfully reproduces the El Nino event cycle which exhibits quasi-regular oscillations with a preferred period of about 4 years.The results show that the heat content(HC) is transported between the eastern and the western tropical Pacific areas.The spatial distribution of HC anomalies for four phases of the whole cycle clearly shows a possible formation mechanism of El Nino.Experiments further suggest that sea surface temperature in the tropical Pacific and HC in the central tropical Pacific are the most important factors and the central tropical Pacific is the most important area for determining formation of El Nino cycle. 相似文献
994.
Discussions are carried out on the vertical discretization of current atmospheric models.It is pointed out that there exist problems in the integration of the hydrostatic equation and the computation of vertical advection,vertical diffusion and so on.Then some possible ways for solving or alleviating them are suggested.Finally,the choice of vertical coordinate and basis functions is discussed. 相似文献
995.
利用卫星观测的长波磁异常,用等效偶极源方法推导了中国地区的视磁化强度分布.因卫星的高度远大于磁性地壳的厚度,将视磁化强度转换成磁化强度的垂直积分,它代表地壳内磁性物质的区域变化,利用视磁化强度与地表热流相应关系,计算了中国的新疆和东部一些地区居里等温面的深度.新疆地区的居里面深度为35-50km,其分布形态与塔里木盆地和准噶尔盆地的地貌比较相似;中国东部一些地区居里面深度在20-40km之间,与一些作者用航磁等数据得到的居里深度十分接近. 相似文献
996.
作者简单介绍了国内预报员较为熟悉的欧洲中期天气预报中心,美国国家气象中心和日本气象厅三个中期预报模式的性能及预报效果,包括近几年颇为流行的半拉格朗日时间积分方案,物理过程参数化方案的完善和改进,中期数值预报业务模式的发展趋势等。 相似文献
997.
文章设计了一个以均匀网格差分模式为基础的全球变网格多层原始方程差分模式。还证明了如果前者满足了一定条件,从而具有质量与能量守恒性质以及与连续情况一致的动能、位能和表面位能之间的转换关系,则变网格模式也同样具有。而且,把前者改变为后者增加的运算量很小,也非常方便。 相似文献
998.
999.
1000.
W. J. Collins D. S. Stevenson C. E. Johnson R. G. Derwent 《Journal of Atmospheric Chemistry》1997,26(3):223-274
A three-dimensional Lagrangian tropospheric chemistry modelis used toinvestigate the impact of human activities on the tropospheric distributionofozone and hydroxyl radicals. The model describes the behaviour of 50 speciesincluding methane, carbon monoxide, oxides of nitrogen, sulphur dioxide andnineorganic compounds emitted from human activities and a range of other sources.Thechemical mechanism involves about 100 chemical reactions of which 16 arephotochemical reactions whose diurnal dependence is treated in full. The modelutilises a five minute chemistry time step and a three hour advection timestepfor the 50,000 air parcels. Meteorological data for the winds, temperatures,clouds and so on are taken from the UK Meteorological Office global model for1994 onwards. The impacts of a 50% reduction in European NOXemissions onglobal ozone concentrations are assessed. Surface ozoneconcentrations decrease in summertime and rise in wintertime, but to differentextents. 相似文献