全文获取类型
收费全文 | 1243篇 |
免费 | 286篇 |
国内免费 | 218篇 |
专业分类
测绘学 | 12篇 |
大气科学 | 13篇 |
地球物理 | 594篇 |
地质学 | 571篇 |
海洋学 | 35篇 |
天文学 | 86篇 |
综合类 | 20篇 |
自然地理 | 416篇 |
出版年
2023年 | 13篇 |
2022年 | 17篇 |
2021年 | 37篇 |
2020年 | 48篇 |
2019年 | 56篇 |
2018年 | 47篇 |
2017年 | 33篇 |
2016年 | 58篇 |
2015年 | 47篇 |
2014年 | 59篇 |
2013年 | 58篇 |
2012年 | 52篇 |
2011年 | 58篇 |
2010年 | 51篇 |
2009年 | 56篇 |
2008年 | 95篇 |
2007年 | 95篇 |
2006年 | 115篇 |
2005年 | 86篇 |
2004年 | 88篇 |
2003年 | 61篇 |
2002年 | 54篇 |
2001年 | 40篇 |
2000年 | 56篇 |
1999年 | 38篇 |
1998年 | 39篇 |
1997年 | 32篇 |
1996年 | 55篇 |
1995年 | 29篇 |
1994年 | 41篇 |
1993年 | 20篇 |
1992年 | 24篇 |
1991年 | 29篇 |
1990年 | 19篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 2篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有1747条查询结果,搜索用时 31 毫秒
21.
22.
23.
24.
Detailed study on the anisotropy of magnetic susceptibility of arctic marine sediments 总被引:3,自引:0,他引:3
Norbert R. Nowaczyk 《Geophysical Journal International》2003,152(2):302-317
25.
T-matrix approach to shale acoustics 总被引:2,自引:0,他引:2
Morten Jakobsen John A. Hudson Tor Arne Johansen 《Geophysical Journal International》2003,154(2):533-558
26.
An anisotropic fractured poroelastic effective medium theory 总被引:1,自引:0,他引:1
S. R. Tod 《Geophysical Journal International》2003,155(3):1006-1020
27.
28.
Magnetic properties of a freshly fallen LL ordinary chondrite: the Bensour meteorite 总被引:1,自引:0,他引:1
Jrme Gattacceca Pierre Rochette Michle Bourot-Denise 《Physics of the Earth and Planetary Interiors》2003,140(4):343-358
A comprehensive rock magnetic, magnetic anisotropy and paleomagnetic study has been undertaken in the brecciated LL6 Bensour ordinary chondrite, a few months only after its fall on Earth. Microscopic observations and electronic microprobe analyses indicate the presence of Ni-rich taenite, tetrataenite and rare Co-rich kamacite. Tetrataenite is the main carrier of remanence. Magnetization and anisotropy measurements were performed on mutually oriented 125 mm3 sub-samples. A very strong coherent susceptibility and remanence anisotropy is evidenced and interpreted as due to the large impact responsible for the post-metamorphic compaction of this brecciated material and disruption of the parent body. We show that the acquisition of remanent magnetization postdates metamorphism on the parent body and predates the entering of the meteorite in Earth’s atmosphere. Three components of magnetization could be isolated. A soft coherent component is closely related to the anisotropy of the meteorite and is interpreted as a shock remanent magnetization acquired during the same large impact on the parent body. Two harder components show random directions at a few mm scale. This randomness is attributed either to the formation mechanism of tetrataenite or to post-metamorphic brecciation. All components are likely acquired in very low (≈μT) to null ambient magnetic field, as demonstrated by comparison with demagnetization behavior of isothermal remanent magnetization. Two other LL6 meteorites, Kilabo and St-Mesmin, have also been studied for comparison with Bensour. 相似文献
29.
Statistical analysis of the magnetic fabric of samples from several successive lava flows emplaced under similar conditions can allow determination of the mean flow direction when magnetic fabric data from individual flows do not lead to reliable results. A difference between the obtained flow direction and the present dip direction indicates that the flows were tilted after emplacement. For 2 successive series of flows on the Jeanne d’Arc Peninsula presently NNW dipping, this method shows lava emplacement along a SSW–NNE direction. This indicates a gentle tilting acquired during a period of weak deformation in the whole archipelago. Additionally, the magnetic fabric data allow the reconstruction of the different conditions of emplacement of these two series of lava flows and of formation of the local thick conglomerate interbedded between these series. 相似文献
30.
During the past three decades, damage due to swelling action of Ankara Clay has been observed more clearly in some parts of Ankara where rapid expansion of the city led to the construction of various kinds of structures. In this study, a comprehensive research program has been conducted (i) to investigate the effect of remoulding and desiccation on the swelling behavior of Ankara Clay and its swelling anisotropy, (ii) to estimate depth of active zone, (iii) to develop a simple technique in determining the magnitude of swelling based on water content of the soaked specimen after 24 and 72 h (wmax24,72), and (iv) to produce predictive models which could be used to estimate the swelling potential of Ankara Clay from its mineralogical and simply measured engineering characteristics. A laboratory testing program was carried out using both undisturbed, and remoulded and desiccated samples selected from 20 different locations. Montmorillonite was identified as being the main clay mineral present. Based on the moisture content variation with depth, the active expansive zone was considered to be about 2 m. The test results suggest that swelling pressure of the clay considerably decreases and/or dies out when the water content is greater than 30%. It is also noted that the measured lateral swelling is significantly in excess of the vertical equivalent indicating an anisotropy with respect to swelling. Statistical assessments indicate that a new parameter (wmax24,72) from a simple test, suggested in this study, is a very strong parameter for predicting swelling parameters of Ankara Clay. Based on 60 empirical predictive equations with coefficients of correlation between 0.96 and 0.66 from multiple regression analyses, wmax24,72, methylene blue value, liquid limit, dry unit weight and smectite content are the most important index and mineralogical properties to predict the swelling parameters of Ankara clay with small deviations from the measured values. 相似文献