全文获取类型
收费全文 | 502篇 |
免费 | 129篇 |
国内免费 | 225篇 |
专业分类
测绘学 | 11篇 |
大气科学 | 2篇 |
地球物理 | 137篇 |
地质学 | 658篇 |
海洋学 | 15篇 |
综合类 | 18篇 |
自然地理 | 15篇 |
出版年
2024年 | 10篇 |
2023年 | 22篇 |
2022年 | 41篇 |
2021年 | 33篇 |
2020年 | 37篇 |
2019年 | 45篇 |
2018年 | 41篇 |
2017年 | 33篇 |
2016年 | 31篇 |
2015年 | 29篇 |
2014年 | 50篇 |
2013年 | 67篇 |
2012年 | 43篇 |
2011年 | 34篇 |
2010年 | 19篇 |
2009年 | 35篇 |
2008年 | 19篇 |
2007年 | 31篇 |
2006年 | 28篇 |
2005年 | 16篇 |
2004年 | 22篇 |
2003年 | 27篇 |
2002年 | 28篇 |
2001年 | 13篇 |
2000年 | 21篇 |
1999年 | 14篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 11篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 9篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 1篇 |
1987年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有856条查询结果,搜索用时 15 毫秒
751.
On October 27, 2001, a large earthquake with Ms6.0, named the Yongsheng earthquake, occurred along the Jinshajiang segment of Chenghai fault in Yongsheng County, Yuunan Province. It is the largest event to occur along the Chenghai fault in the last 200 years. The seismo-geological survey shows that the seismogenic fault, which is the Jinshajiang segment of Chenghal fault, takes left-lateral strike-slip as its dominant movement pattern. According to differences in vertical motion, motion time, landforms and scales, the Chenhai fault can be divided into eight segments. The Jinshajiang segment has a vertical dislocation rate of 0.4mm/a, far lower than the mean rate of the Chenghai fault, about 2.0 mm/a. It‘ s deduced that the two sides of Jinshajiang segment “stuck“ tightly and hindered the strike-slip of the Chenghai fault. The strong earthquake distribution before this event shows that the Jinshajiang segment was in the seismic gap. The Chenghai fault, as a boundary of tectonic sub-blocks, makes the Northwest Yunnan block and the Middle Yunnan block move clockwise, and their margins move oppositely along the Chenghai fault. In the motion process of the Chenghai fault, structural hindrance and the seismic gap of strong earthquakes are propitious to the concentration and accumulation of structure stress. As a result, the Yongsheng Ms6.0 earthquake occurred. The Sujiazhuang-Shangangfu segment is similar to the Jinshajiang segment with a low vertical motion rate of 0.3 mm/a and in the seismic gap. So it‘s postulated that the segment may become a new structure hindrance, and the Yongsheng Ms6.0 earthquake may trigger the occurrence of future large earthquakes along this segment. 相似文献
752.
We report new occurrences of sapphirine- and corundum-bearing granulites intercalated within orthogneisses at Lachmanapatti and Malappatty in the northern part of Madurai Block. Sapphirine in these localities occurs either as needle-like intergrowth with cordierite and corundum in symplectites and medium- to fine-grained euhderal to subhedral crystals associated with cordierite and corundum (Lachmanapatti) or in association with plagioclase, corundum and gedrite (Malappatty). The sapphirine from Lachmanapatti is highly magnesian (XMg = 0.87-0.94) with higher Cr content (up to 0.9 pfu) as compared with those in other localities in the Madurai Block. The sapphirine-corundum association reported in this study has important bearing on the ultrahigh-temperature metamorphism and exhumation history of the northern Madurai Block as well as on the tectonic evolution of the continental deep crust in southern India. 相似文献
753.
Late Cretaceous palaeomagnetic results from Sikhote Alin, far eastern Russia: tectonic implications for the eastern margin of the Mongolia Block 总被引:3,自引:0,他引:3
754.
Detailed paleomagnetic investigation of a pyroclastic flow deposit has clarified the deformation mode around an active fault. In central Japan, the early Quaternary Nyukawa Pyroclastic Flow Deposit is cut by the active dextral Enako fault. Activity level of the fault is evaluated on the basis of geological and geomorphological surveys. Then, paleomagnetic samples are collected from 22 sites at exposures located on a lineament that is adjoining and parallel to the Enako fault. Stable thermoremanent magnetization (TRM) of the pyroclastic deposit is isolated through progressive thermal and/or alternating field demagnetization tests. Untilted site-mean directions of the TRMs simultaneously acquired during initial cooling indicate significant clockwise vertical-axis rotation. The lineament was then activated with right-lateral motions through the early Quaternary. Together with the late Quaternary activities along the adjoining Enako fault evaluated by our study, the present result exemplifies a migration of active segments within a fault system during the Quaternary. Paleomagnetic directions on the strike–slip fault are not concordant with uniform deformation predicted by the model of rotation of rigid blocks aligned on a master fault, but suggestive of a periodic deformation as a result of intense fracturing and differential rotation of blocks bounded by nested parallel faults. 相似文献
755.
A palaeomagnetic study of the Ronda peridotites (southern Spain) has been carried out on 301 samples from 20 sites, spread along the three main outcrops of the ultrabasic complex: Ronda, Ojén and Carratraca massifs. Different lithologies and outcrops with different degrees of serpentinization have been sampled and analysed. Rock magnetic experiments have been carried out on a representative set of samples. These measurements include: Curie curves, hysteresis cycles, isothermal remanent magnetization (IRM) acquisition curves, thermal demagnetization of IRM imparted along three orthogonal axes and magnetic bulk susceptibility. Results indicate that magnetite is the main magnetic mineral present in the samples. Stepwise thermal and alternating field (AF) demagnetization of the natural remanent magnetization (NRM) reveals the presence of a characteristic remanent magnetization (ChRM) carried by magnetite, and in some sepentinized samples, a northward component with variable unblocking temperatures up to 250–575 °C. The appearance and the relative intensity of this northward component are strongly related to serpentinization degree. Taking into account the geological history of the peridotites, the ChRM has been considered as a thermo-chemical remanent magnetization acquired during the first serpentinization phase associated to the post-metamorphic cooling of this unit. On the basis of radiometric and fission track analysis, the ChRM is proposed to have been acquired between 20 and 17–18 Ma. The inclination of the mean direction of the ChRM statistically coincides with the expected inclination for stable Iberia during the Oligocene–Miocene. The declination of the ChRM differs from the expected declination, indicating clockwise block rotations of 41±12° about vertical axes since the cooling of the peridotites. When applying a compositional layering correction, the ChRM directions fail to pass this kind of fold test, thus, the compositional layering was not a palaeohorizontal during ChRM acquisition time. Normal and reversed polarities of the ChRM are reported, showing that at least one reversal of the Earth's magnetic field took place during ChRM acquisition process. A tentative polarity zonation within the peridotitic outcrops is also suggested. No evidence is found from these data for the previously proposed simultaneity between post-metamorphic cooling and rotation of the peridotites. 相似文献
756.
扬子地块南缘晚古生代洋壳存在的Nd同位素证据 总被引:7,自引:0,他引:7
总结我国扬子地块南缘新元古代—早中生代沉积岩目前已发表的Nd同位素资料发现,这些沉积岩具有随时间变化而其Nd同位素组成发生漂移的现象。在绝大多数时间里,它们具有2000Ma左右的Nd模式年龄,但在1000~700Ma的新元古代和<400Ma的晚古生代—早中生代时间段中,Nd同位素模式年龄急剧降低,反映在此时间段内,新生地幔物质已经进入沉积物的物源区。1000~700Ma期间的Nd同位素变化归因于晋宁期的碰撞造山作用而晚古生代-早中生代沉积岩的Nd同位素变异起因于海盆发育阶段洋壳的出现。即扬子地块南缘在晚古生代—早中生代期间曾经存在过洋壳,且该洋盆可能是古特提斯大洋分支的一部分。 相似文献
757.
758.
759.
华北陆块对Rodinia超大陆的响应及其特征 总被引:13,自引:0,他引:13
研究揭示华北陆块1300-1000Ma和800-650Ma都存在比较弱的岩浆-变质事件,它们可能对应于华南陆块的碰撞(四堡运动)和裂解事件。华北陆块的四堡期蛇绿混杂岩可能只见于新元古代秦岭造山带中。秦岭造山带北缘识别出了一些花岗质分清入体,它们具有碰撞或碰撞后花岗岩的特征。华北陆块北缘的火山沉积岩生活费不具有离散边界杂岩的特征,它们可能揭示了大陆边缘或者大陆伸展过程。华北陆块与800-650Ma事件相关的岩石主要为来自富集地幔的基性岩墙和来自陆内裂谷的沉积岩,它们很可能与Rodinia裂解有关。沉积学和古生物学特征表明元古宙华北陆块不同华南陆块,而与西伯利亚陆块相似。据此可以认为华北陆块是Rodinia超大陆的一部分,它位于超大陆的边缘,可以不与华南陆块紧邻,而与西伯利亚陆地较近。 相似文献
760.