全文获取类型
收费全文 | 3450篇 |
免费 | 1139篇 |
国内免费 | 445篇 |
专业分类
测绘学 | 257篇 |
大气科学 | 258篇 |
地球物理 | 2010篇 |
地质学 | 1352篇 |
海洋学 | 262篇 |
天文学 | 23篇 |
综合类 | 272篇 |
自然地理 | 600篇 |
出版年
2024年 | 13篇 |
2023年 | 33篇 |
2022年 | 93篇 |
2021年 | 138篇 |
2020年 | 139篇 |
2019年 | 202篇 |
2018年 | 149篇 |
2017年 | 191篇 |
2016年 | 174篇 |
2015年 | 207篇 |
2014年 | 239篇 |
2013年 | 206篇 |
2012年 | 207篇 |
2011年 | 206篇 |
2010年 | 158篇 |
2009年 | 200篇 |
2008年 | 191篇 |
2007年 | 252篇 |
2006年 | 222篇 |
2005年 | 192篇 |
2004年 | 192篇 |
2003年 | 160篇 |
2002年 | 142篇 |
2001年 | 105篇 |
2000年 | 100篇 |
1999年 | 103篇 |
1998年 | 108篇 |
1997年 | 108篇 |
1996年 | 106篇 |
1995年 | 83篇 |
1994年 | 72篇 |
1993年 | 74篇 |
1992年 | 56篇 |
1991年 | 47篇 |
1990年 | 38篇 |
1989年 | 29篇 |
1988年 | 31篇 |
1987年 | 19篇 |
1986年 | 20篇 |
1985年 | 5篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1974年 | 1篇 |
1954年 | 14篇 |
排序方式: 共有5034条查询结果,搜索用时 15 毫秒
41.
大地震的震源机制及地震矩、应力降等参数,不(又对认识地震的破裂过程,而且对预报强地面运动都是非常重要的。一些文章对板内地震应力降的特点、地震矩与高频源谱的关系及区域特征的讨论,使我们可直接由长周期体波或面波得出的地震矩M0估计出不同地区中大地震的高频源谱,以供强地面运动预报参考。 由于对发生在中国板内的1976年11月6日盐源地震(Ms=6.5)和1976年11月15日宁河地震(Ms=6.3)的震源参数还没有详尽的报道;另外,对1973年7月14日 相似文献
42.
A simplified procedure for evaluating aseismic stability of slope subjected to earthquake shaking, in which the effect of dynamic shear strength and time-history stress on the yielding angular acceleration of sliding block is taken into account, is presented. The fundamental feature of this procedure is the dynamic shear strength. The numerical computations are performed by using the proposed method. It is shown that the computed sliding displacement for a given core dam, with either method of dynamic shear strength properly considered, is more rational compared with the conventional computational results based on static shear strength. 相似文献
43.
From July 1996 to August 1997 the TOR project operated 130 seismographs in North Germany, Denmark and South Sweden, with the aim of collecting signals from local, regional and teleseismic earthquakes. This data set is particularly interesting since the seismic antenna crosses the most significant geological boundary in Europe, the Tornquist Zone, which in the northern part is the border between the Baltic Shield and the younger European lithosphere. Previous studies have shown significant physical changes in the crust and upper mantle across this transition zone, including two independent teleseismic tomographic studies of the TOR data set. But these two studies disagree on the orientation of the slope of the transition. Both studies used an iterative linearized inversion method. We will in this work Preprint submitted to Elsevier Science 27 July 2005 present an inversion based on Bayesian statistics, where the solution space is examined in order to study a very large number of tomographic solutions and to examine the solution uniqueness and uncertainty. The method is applied to measurements of 3345 relative teleseismic P-phase travel times from 48 teleseismic earthquakes with good azimuthal coverage with respect to the great circle arc of the TOR array. We find the lithospheric transition to be a north east inclination of around 30° to 45° off vertical. 相似文献
44.
45.
Michael Commer Stefan L. Helwig reas Hördt Carsten Scholl Bülent Tezkan 《Geophysical Journal International》2006,167(3):1172-1187
46.
47.
48.
49.
A time-varying spherical harmonic model of the palaeomagnetic field for 0–7 ka is used to investigate large-scale global geomagnetic secular variation on centennial to millennial scales. We study dipole moment evolution over the past 7 kyr, and estimate its rate of change using the Gauss coefficients of degree 1 (dipole coefficients) from the CALS7K.2 field model and by two alternative methods that confirm the robustness of the predicted variations. All methods show substantial dipole moment variation on timescales ranging from centennial to millennial. The dipole moment from CALS7K.2 has the best resolution and is able to resolve the general decrease in dipole moment seen in historical observations since about 1830. The currently observed rate of dipole decay is underestimated by CALS7K.2, but is still not extraordinarily strong in comparison to the rates of change shown by the model over the whole 7 kyr interval. Truly continuous phases of dipole decrease or increase are decadal to centennial in length rather than longer-term features. The general large-scale secular variation shows substantial changes in power in higher spherical harmonic degrees on similar timescales to the dipole. Comparisons are made between statistical variations calculated directly from CALS7K.2 and longer-term palaeosecular variation models: CALS7K.2 has lower overall variance in the dipole and quadrupole terms, but exhibits an imbalance between dispersion in g 1 2 and h 1 2 , suggestive of long-term non-zonal structure in the secular variations. 相似文献
50.