全文获取类型
收费全文 | 6309篇 |
免费 | 1701篇 |
国内免费 | 1543篇 |
专业分类
测绘学 | 76篇 |
大气科学 | 1012篇 |
地球物理 | 3098篇 |
地质学 | 1744篇 |
海洋学 | 2835篇 |
天文学 | 76篇 |
综合类 | 319篇 |
自然地理 | 393篇 |
出版年
2024年 | 28篇 |
2023年 | 86篇 |
2022年 | 160篇 |
2021年 | 216篇 |
2020年 | 246篇 |
2019年 | 376篇 |
2018年 | 270篇 |
2017年 | 252篇 |
2016年 | 255篇 |
2015年 | 333篇 |
2014年 | 343篇 |
2013年 | 364篇 |
2012年 | 398篇 |
2011年 | 408篇 |
2010年 | 319篇 |
2009年 | 405篇 |
2008年 | 384篇 |
2007年 | 527篇 |
2006年 | 432篇 |
2005年 | 390篇 |
2004年 | 399篇 |
2003年 | 345篇 |
2002年 | 307篇 |
2001年 | 258篇 |
2000年 | 260篇 |
1999年 | 245篇 |
1998年 | 247篇 |
1997年 | 196篇 |
1996年 | 210篇 |
1995年 | 196篇 |
1994年 | 165篇 |
1993年 | 134篇 |
1992年 | 107篇 |
1991年 | 92篇 |
1990年 | 46篇 |
1989年 | 42篇 |
1988年 | 37篇 |
1987年 | 21篇 |
1986年 | 11篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1954年 | 10篇 |
排序方式: 共有9553条查询结果,搜索用时 15 毫秒
231.
232.
233.
234.
235.
低应变反射波法在基桩检测中的应用实例及一些问题的探讨 总被引:5,自引:0,他引:5
根据应力波理论,介绍了用低应变反射波法在桩身完整性检测中的几个应用实例,并对检测中的一些问题作了探讨。 相似文献
236.
德令哈6.6级地震前卫星红外长波辐射OLR的分析 总被引:4,自引:0,他引:4
应用NOAA卫星资料反演的地震长波辐射值OLR对2003年4月17日发生在青海省德令哈西的6.6级地震进行了追踪研究。结果显示:2003年1月起OLR距平值出现明显的高值异常区域。 相似文献
237.
Short period surface waves, recorded during a seismic refractionsurvey in the Sannio region (Southern Italy), have been modeled to infera shallow velocity model for the area. Based on the decrease of resolutionwith depth, due to the bias on group velocity estimates arising frominterference of the Rayleigh waves with higher modes, we carried out aprocedure of fitting, with synthetic seismograms, of selected filtered traceswith a gaussian filter, having a width at half height equal to 1 Hz and acentral frequency lying in the range [1,4] Hz. We estimated the likelihoodbetween synthetic and observed seismograms by measuring their semblance.In this way we were able to infer a more refined local velocity modelcharacterized by a high Vp and Vs vertical gradient in the sedimentarycover. Two ad hoc resolution studies, based on group velocity andamplitude data respectively, indicate that the local velocity model is a goodvelocity model also for the entire studied area. The increase in the numberof available data when using amplitude information allows us to make amore selective choice in the model parameter space (Vp and Vs of eachlayer) and to solve for the Vp/Vs ratio. The inferred Vp velocity in thehalf-space is equal to 2.8 km/s. This value is in excellent agreement withthat inferred by other authors (3 km/s) by modeling P-wave travel timevs. distance. The best-fit model furnish low Vp/Vs for the sedimentarycover so indicating a high degree of the sediment's compaction in thestudied area. The inferred shallow high-velocity gradient indicates thatthe shallow sedimentary layer in the area could trap and focus the energytraveling into it. 相似文献
238.
The effect of asymmetry and irregularity of the inputted seismic waves on the earthquake-induced differential settlement of the buildings on natural subsoil is investigated in terms of the earthquake damage phenomena, theoretical analyses, dynamic triaxial tests and shaking table tests. A conclusion can be drawn from the investigation results that, the asymmetrical and irregular character of the inputted seismic waves themselves may have a significant contribution to the differential settlement of subsoil and buildings in some cases, and this is a necessary factor to be considered in reasonable evaluation for the differential settlement and other problems relating to the soil deformation due to earthquakes. 相似文献
239.
240.
G. Jayachandran M.M. Abdul RazakA.G.V. Prasad E. Unnikrishnan 《Physics of the Earth and Planetary Interiors》2003,138(2):131-145
The devastating earthquake on 26 January 2001 at Bhuj, India, resulted in large-scale death and destruction of properties of several million US dollars. The moment magnitude of the earthquake was 7.7 and its maximum focal intensity exceeded X in MM scale. The rate of aftershocks of this earthquake, recorded at Gauribidanur seismic array station (GBA), shows a monotonic decay with time superposed with oscillations. For the Indian continent the Lg phase is a prominent arrival at regional distances. The estimate of Lg amplitude is obtained by optimally fitting the Lg wave train to a exponential decay curve. The logarithm of these amplitudes and logarithm of root mean square (rms) value of actual amplitudes of the Lg are calibrated with USGS mb to create a local mbLg magnitude scale. The energy released from these aftershocks is calculated from the rms value of Lg phase. The plot of cumulative energy release with time follows the power law of the form tp, superposed with oscillations. The exponent of the power law, p, is estimated both by a time-window scanning method and by an interpolation method. The value of p is 0.434 for time-window scanning method and 0.432 for the interpolation method. The predominant periods found in the oscillatory part of the cumulative energy, obtained by differencing the observed from the power law fit, are 10.6, 7.9, 5.4, 4.6 and 3.5 h for time-window scanning method. The corresponding periods for interpolation method are 13.4, 11.5, 7.4, 4.2, 3.5, 2.6 and 2.4 h. 相似文献