全文获取类型
收费全文 | 3706篇 |
免费 | 756篇 |
国内免费 | 869篇 |
专业分类
测绘学 | 214篇 |
大气科学 | 666篇 |
地球物理 | 1050篇 |
地质学 | 1806篇 |
海洋学 | 495篇 |
天文学 | 252篇 |
综合类 | 403篇 |
自然地理 | 445篇 |
出版年
2024年 | 19篇 |
2023年 | 65篇 |
2022年 | 227篇 |
2021年 | 230篇 |
2020年 | 195篇 |
2019年 | 242篇 |
2018年 | 210篇 |
2017年 | 225篇 |
2016年 | 239篇 |
2015年 | 211篇 |
2014年 | 234篇 |
2013年 | 217篇 |
2012年 | 244篇 |
2011年 | 217篇 |
2010年 | 207篇 |
2009年 | 194篇 |
2008年 | 191篇 |
2007年 | 165篇 |
2006年 | 147篇 |
2005年 | 111篇 |
2004年 | 99篇 |
2003年 | 105篇 |
2002年 | 107篇 |
2001年 | 117篇 |
2000年 | 130篇 |
1999年 | 130篇 |
1998年 | 119篇 |
1997年 | 114篇 |
1996年 | 101篇 |
1995年 | 96篇 |
1994年 | 89篇 |
1993年 | 68篇 |
1992年 | 67篇 |
1991年 | 39篇 |
1990年 | 31篇 |
1989年 | 31篇 |
1988年 | 18篇 |
1987年 | 12篇 |
1986年 | 9篇 |
1985年 | 8篇 |
1984年 | 13篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1958年 | 9篇 |
1954年 | 1篇 |
排序方式: 共有5331条查询结果,搜索用时 187 毫秒
101.
本文通过联剖、电测深、磁法和测温法等综合工作成果,分析、推断出汤上屯热水构造的产状、性质和热水出露条件,圈定出了热水分布范围. 相似文献
102.
Lijiang-Daju fault, the seismogenic fault of the 1996 Lijiang M=7.0 earthquake, can be divided into Lijiang-Yuhu segment in the south and Yuhu-Daju segment in the north. The two segments show clear difference in geological tectonics, but have the similar dynamic features. Both normal dip-slip and sinistral strike-slip coexist on the fault plane. This kind of movement started at the beginning of the Quaternary (2.4~2.5 Ma B.P.). As to the tectonic types, the detachment fault with low angle was developed in the Early Pleistocene and the normal fault with high angle only after the Mid-Pleistocene (0.8 Ma B.P.). Based on the horizontal displacements of gullies and the vertical variance of planation surfaces cross the Lijiang-Daju fault at east piedmont of Yulong-Haba range, the average horizontal and vertical slip rates are calculated. They are 0.84 mm/a and 0.70 mm/a since the Quaternary and 1.56 mm/a and 1.69 mm/a since the Mid-Pleistocene. The movements of the nearly N-S-trending Lijiang-Daju fault are controlled not only by the regional stress field, but also by the variant movement between the Yulong-Haba range and Lijiang basin. The two kinds of dynamic processes form the characteristics of seismotectonic environment of occurring the 1996 Lijiang earthquake. 相似文献
103.
Depositional sequence architecture and filling response model of the Cretaceous in the Kuqa depression, the Tarim basin 总被引:1,自引:0,他引:1
The Cretaceous system of the Kuqa depression is a regional scale (second order) depositional sequence defined by parallel unconformities or minor angular unconformities. It can be divided into four third-order sequence sets, eleven third-order sequences and tens of fourth- and fifth-order sequences. It consists generally of a regional depositional cycle from transgression to regression and is composed of three sets of facies associations: alluvial-fluvial, braided river-deltaic and lacustrine-deltaic facies associations. They represent the lowstand, transgressive and highstand facies tracts within the second-order sequence. The tectonic subsidence curve reconstructed by backstripping technique revealed that the Cretaceous Kuqa depression underwent a subsidence history from early accelerated subsidence, middle rapid subsidence and final slower subsidence phases during the Cretaceous time, with the correspondent tectonic subsidence rates being 30-35 m/Ma, 40-45 m/Ma and 5-10 m/Ma obtained from northern foredeep. This is likely attributed to the foreland dynamic process from early thrust flexural subsidence to late stress relaxation and erosion rebound uplift. The entire sedimentary history and the development of the three facies tracts are a response to the basin subsidence process. The slower subsidence foreland gentle slope was a favorable setting for the formation of braided fluvial deltaic systems during the late period of the Cretaceous, which comprise the important sandstone reservoirs in the depression. Sediment records of impermanent marine transgression were discovered in the Cretaceous and the major marine horizons are correctable to the highstands of the global sea level during the period. 相似文献
104.
本文采用Lorenz(1960)系统,在只考虑初始误差及观测误差而不考虑模式误差的情况下,利用扩展卡尔曼滤波(Extended Kalman Filter)数据同化方法进行了数值模拟试验。数值试验的结果表明:扩展卡尔曼滤波数据同化方法对系统状态的估计有较好的改善作用,能有效的抑制估计误差的增长;加大观测频率,可以进一步改善数据同化的效果,使估计误差进一步减小;由于模式误差的存在,系统的不稳定能量会不断的累积,出现了估计误差的异常增长和计算的不连续现象,在模式预报方程中的均值演变方程加人二阶偏差纠错项,对控制估计误差的异常增长,进一步改善数据同化的效果有较明显作用。 相似文献
105.
106.
107.
108.
本文利用2001-2003年南极中山站175天全天空摄像机观测,对午后多重极光弧的出现率及其与Kp指数的关系进行了统计分析,结果表明午后多重极光弧出现率呈一单峰分布,最大发生率出现在1445UT(1645MLT),其位置在1500MLT极光热点(1300-1700MLT)近夜侧的部分。与地磁活动指数Kp的相关统计分析表明,Kp值为2-3之间时多重极光弧有较大的出现率,这说明中等地磁活动情形下午后多重极光弧有较高的出现率。事件分析表明多重极光弧的强度变化与地磁Pc5脉动具有较高的相关性,并且有类似的频谱特征,这说明午后多重极光弧可能与同时出现的Pc5地磁脉动有关。 相似文献
109.
110.
New magnetostratigraphic and pedostratigraphic investigations of loess deposits in north‐east China and their implications for regional environmental change during the Mid‐Pleistocene climatic transition 下载免费PDF全文