全文获取类型
收费全文 | 1472篇 |
免费 | 159篇 |
国内免费 | 147篇 |
专业分类
测绘学 | 512篇 |
大气科学 | 77篇 |
地球物理 | 259篇 |
地质学 | 352篇 |
海洋学 | 101篇 |
天文学 | 134篇 |
综合类 | 126篇 |
自然地理 | 217篇 |
出版年
2023年 | 9篇 |
2022年 | 32篇 |
2021年 | 57篇 |
2020年 | 53篇 |
2019年 | 65篇 |
2018年 | 47篇 |
2017年 | 83篇 |
2016年 | 68篇 |
2015年 | 76篇 |
2014年 | 78篇 |
2013年 | 98篇 |
2012年 | 90篇 |
2011年 | 98篇 |
2010年 | 71篇 |
2009年 | 104篇 |
2008年 | 86篇 |
2007年 | 111篇 |
2006年 | 74篇 |
2005年 | 63篇 |
2004年 | 52篇 |
2003年 | 50篇 |
2002年 | 47篇 |
2001年 | 33篇 |
2000年 | 35篇 |
1999年 | 34篇 |
1998年 | 24篇 |
1997年 | 21篇 |
1996年 | 19篇 |
1995年 | 19篇 |
1994年 | 11篇 |
1993年 | 10篇 |
1992年 | 13篇 |
1991年 | 10篇 |
1990年 | 2篇 |
1989年 | 11篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有1778条查询结果,搜索用时 62 毫秒
1.
T. H. BELL S. E. JOHNSON B. DAVIS A. FORDE N. HAYWARD C. WILKINS 《Journal of Metamorphic Geology》1992,10(3):295-307
Extensive examination of large numbers of spatially orientated thin sections of orientated samples from orogens of all ages around the world has demonstrated that porphyroblasts do not rotate relative to geographical coordinates during highly non-coaxial ductile deformation of the matrix subsequent to their growth. This has been demonstrated for all tectonic environments so far investigated. The work also has provided new insights and data on metamorphic, structural and tectonic processes including: (1) the intimate control of deformation partitioning on metamorphic reactions; (2) solutions to the lack of correlation between lineations that indicate the direction of movement within thrusts and shear zones, and relative plate motion; and (3) a possible technique for determining the direction of relative plate motion that caused orogenesis in ancient orogens. 相似文献
2.
介绍了自动高精度测距系统。该系统能以5×10-7的测距精度测定多个观测点的形变,可作为跨断层动态连续观测的新仪器。 相似文献
3.
4.
Ralph A. M. J. Wijers 《Astrophysics and Space Science》1995,231(1-2):399-402
Since the discovery that dim gamma-ray bursts last longer on average than bright ones (time dilation) the cosmological origin of this effect has been contested by various researchers. I discuss the current status of this issue and conclude that current models for a non-cosmological time dilation only explain part of the observed phenomenon, and even then betray themselves by distinct signatures in the data. As those signatures have not been seen, the cosmological origin remains the favoured explanation of the time dilation. 相似文献
5.
AbstractThe ground vibrations during pile driving operation have a drastic potential to undermine the surrounding structures both in land and reclaimed land. Particularly, reclaimed land necessitates ample application of pile driving due to the weak land condition. To prevent the structural damage, attenuation of the ground vibrations to an allowable level through active isolation of circular open trench is the scope of this study. In this research, finite element simulations of continuous impact pile driving process from the ground surface was executed with particular attention to the pile-soil interaction, and thereby, the efficiency of open trench application in attenuation of the unsafe distance of different structures was surveyed using the vibration sensitivity degree. Regarding the crucial parameters of an open trench (depth, width, and location), it was concluded that a sufficient high depth can attenuate the unsafe distance up to 68%, the trench width variations are less effective, and an average pile-trench distance is the most efficient option. The excavation volume was also concluded as another crucial parameter in open trench design which takes all three parameters into account. The trench depth equal to the pile’s maximum critical depth of vibration was inferred for an optimum design. 相似文献
6.
7.
8.
9.
10.