全文获取类型
收费全文 | 457篇 |
免费 | 106篇 |
国内免费 | 175篇 |
专业分类
地球物理 | 26篇 |
地质学 | 662篇 |
海洋学 | 3篇 |
综合类 | 36篇 |
自然地理 | 11篇 |
出版年
2024年 | 3篇 |
2023年 | 6篇 |
2022年 | 9篇 |
2021年 | 18篇 |
2020年 | 17篇 |
2019年 | 23篇 |
2018年 | 20篇 |
2017年 | 29篇 |
2016年 | 15篇 |
2015年 | 25篇 |
2014年 | 24篇 |
2013年 | 63篇 |
2012年 | 23篇 |
2011年 | 22篇 |
2010年 | 17篇 |
2009年 | 25篇 |
2008年 | 22篇 |
2007年 | 28篇 |
2006年 | 31篇 |
2005年 | 23篇 |
2004年 | 20篇 |
2003年 | 23篇 |
2002年 | 18篇 |
2001年 | 17篇 |
2000年 | 22篇 |
1999年 | 15篇 |
1998年 | 20篇 |
1997年 | 25篇 |
1996年 | 20篇 |
1995年 | 30篇 |
1994年 | 17篇 |
1993年 | 21篇 |
1992年 | 7篇 |
1991年 | 10篇 |
1990年 | 4篇 |
1989年 | 14篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有738条查询结果,搜索用时 15 毫秒
641.
Françoise Chalot-Prat Petr Tikhomirov Aline Saintot 《Journal of Earth System Science》2007,116(6):469-495
In Late Devonian and Early-to-Late Triassic times, the southern continental margin of the Eastern European Platform was the
site of a basaltic volcanism in the Donbas and Fore-Caucasus areas respectively. Both volcanic piles rest unconformably upon
Paleoproterozoic and Late Paleozoic units respectively, and emplaced during continental rifting periods some 600 km away from
expected locations of active oceanic subduction zones.
This paper reports a comparative geochemical study of the basaltic rocks, and views them as the best tracers of the involved
mantle below the Eastern European Platform. The Late Devonian alkaline basic rocks differ from the calc-alkaline Triassic
basic rocks by their higher alkali-silica ratio, their higher TiO2, K2O, P2O5 and FeO contents, their higher trace element contents, a higher degree of fractionation between the most and the least incompatible
elements and the absence of Ta-Nb negative anomalies. These general features, clearly distinct from those of partial melting
and fractional crystallization, are due to mantle source effects. With similar Nd and Sr isotopic signatures indicating mantle-crust
mixing, both suites would originate from the melting of a same but heterogeneous continental mantle lithosphere (refertilized
depleted mantle). Accordingly the Nd model ages, the youngest major event associated with mantle metasomatism occurred during
Early Neoproterozoic times (∼650Ma). 相似文献
642.
新疆北山黑石山地区下泥盆统大南湖组地层的发现 总被引:1,自引:0,他引:1
在1/25万《红宝石幅》区域地质调查过程中,在新疆北山黑石山地区发现早泥盆世火山—沉积地层,通过岩石地层、生物化石及地层年代研究,结合区域地层对比,将其划归大南湖组。该组的确定为恢复哈萨克斯坦板块南缘区域地质演化历史提供了新的资料。 相似文献
643.
Pioneer organisms after F-F mass extinction in Dushan region, Guizhou Province, and their significance in establishing new ecosystem 总被引:1,自引:0,他引:1
After bio-mass extinction, the ecosystems in most areas were damaged seriously and may become an “ecologically barren area” lacking or even without ecosystems. To know what the pioneer organisms would be and their development, and to trace the es- tablishment process of the ecosystems are of great importance for the study of the biological evolution and recovery in aftermath. As one of the “big five” mass extinctions in the geological history, the Late Devonian Frasnian-Famennian (F-F) e… 相似文献
644.
645.
分叉波痕在广西上泥盆统钙质浊积岩中的发现及意义 总被引:3,自引:0,他引:3
小型不对称分叉波痕(简称分叉波痕)发现于桂林杨堤剖面上泥盆统弗拉斯阶linguiformis牙形石带,桂林碳酸盐台地东南缘斜坡相钙质浊积岩鲍马序列C段。波长7.5~8.0cm,波高0.5~0.8cm,波痕指数15~10;向流面长5.0~7.0cm,背流面长2.5~4.0cm,波痕对称指数2.0~1.8;背流面向东倾;波脊较圆滑、缓曲,且具明显的分叉现象。是浊流流速减缓,密度流转化为牵引流后在低流态条件下,并叠加有推进型风暴浪作用形成的复合成因波痕。根据该波痕和寄主地层特征,推断含分叉波痕的阳朔碳酸盐盆地的最大水深约100m,极限水深小于200m。这一估计值应能代表广西乃至华南板块泥盆纪广泛发育的含牙形石动物群和钙质浊积岩碳酸盐沉积盆地的定量水深,可能也代表了弗拉斯阶一法门阶之交受集群绝灭事件重创的浅水海相生物与基本未受影响的深水海相生物的水深分界线。 相似文献
646.
滇西南早泥盆世地层研究新进展 总被引:2,自引:1,他引:1
滇西南西盟里拉、孟连回库腊垒组发现早泥盆世Monograptushercynicus、M.falcarius等7个笔石种,从下到上识别出M.uniformis带、M.hercynicus带和M.falcarius带3个笔石带,分别属于洛赫科夫期早期、晚期和布拉格期早期,并与国内外其他地区的笔石带进行了对比。对该时期笔石的生物地理分析表明,洛赫科夫期的笔石具有全球性,而布拉格期的笔石则显示出一定程度的地区性。 相似文献
647.
将旋回地层学(cyclostratigraphy)和层序地层学(sequencestratigraphy)有机地结合起来并应用沉积学和地层学的基本理论研究了陕西省商南地区上泥盆统王冠沟组旋回层序级别的划分、层序边界特征、三级旋回层序内部组成特征以及米级旋回的沉积特点。王冠沟组可以识别出1.5个三级旋回层序,4个四级旋回层序,共发育86个米级旋回,归属8大类。三级旋回层序发育低水位体系域(LST)、海进体系域(TST)、高水位体系域(HST)和陆架边缘体系域(SMST)。第一个三级旋回层序的底界面为Ⅰ型层序界面(SB1),顶界面为Ⅱ型层序界面(SB2),明显地具间断-加积旋回(PAC)沉积特征。通过详细的旋回层序研究以及与中国黔南和世界晚泥盆世弗拉斯阶海进-海退旋回进行比较研究,并结合区域地层对比研究,商南地区上泥盆统王冠沟组旋回发育不完整,推测可能地层发育不全。 相似文献
648.
The Ashele Deposit: A Recently Discovered Volcanogenic Massive Sulfide Cu-Zn Deposit in Xinjiang, China 总被引:1,自引:0,他引:1
Abstract: The Ashele Cu-Zn deposit is a recently discovered volcanogenic massive sulfide deposit in Xinjiang, Northwestern China. It is the largest Cu-Zn deposit in this type of deposits in China, which were formed in the early period of later Palaeozoic Era. This deposit is hosted within a suit of bimodal submarine volcanic rocks of the Ashele Formation of Lower-Middle Devonian System formed in an environment of paleocontinental margin rift setting. Lensoid orebodies occur between spilitic rocks developed at footwall and quartz-keratophyric tuff at hanging wall. Zonation of metal elements in the Ashele mine is one of typical volcanic-related exhalative Cu-Zn sulfide deposits in the world. Black ores enriched in Pb, Zn and Ag occurs on the top of the No. 1 orebody in the Ashele deposit, yellow ores enriched in Cu in the middle part, and the chalcopyritization stringer below the massive sulfide ores. Zonation of ore-structure in the No. 1 orebody is also apparent and corresponds to the zoning of elements, i. e. lamellar and/or banded sulfide-sulfate ores on the top, massive sulfide ores in the middle, and stockwork veinlets associated with altered breccia pipe on the bottom. Four epochs of mineralization in the Ashele deposit has been recognized. The first period of syngenetic-exhalative deposition of sulfides is the main epoch of mineralization, and the ores deposited subsequently subjected to thermo-metamorphism at the second epoch, superimposed by hydrothermal mineralization at the third epoch, and weathered or oxidized at the fourth epoch.
More than 100 categories of minerals have been recognized in the Ashele mine, but only pyrite, chalcopyrite, sphalerite, tetrahedrite, galena, barite, quartz, chlorite, sericite, and calcite are dominant, making up various types of ores, and alteration pipes or horizons. Studies of ore petrology suggest that the massive ores were volcanogenic and deposited by exhalative process. 相似文献
More than 100 categories of minerals have been recognized in the Ashele mine, but only pyrite, chalcopyrite, sphalerite, tetrahedrite, galena, barite, quartz, chlorite, sericite, and calcite are dominant, making up various types of ores, and alteration pipes or horizons. Studies of ore petrology suggest that the massive ores were volcanogenic and deposited by exhalative process. 相似文献
649.
扬子西缘龙门山区泥盆纪沉积旋回与相序样式 总被引:2,自引:0,他引:2
扬子西缘龙门山地区泥盆系可识别出一个二级、三个准二级、十八个三级沉积旋回和三十余种高频旋回,低级(高频)旋回往往以不同形式叠加构成高一级沉积旋回。高频旋回具有复杂的相序结构样式,大致可概括为非对称向上变浅、加深和对称型三种。整个泥盆纪沉积旋回的旋回演化作用早期为异旋回作用,中期为自旋回与异旋回作用交替,晚期则转变成自旋回作用为主。 相似文献
650.
蚣坝、水市地区位于华南褶皱系南岭构造带中段北缘,泥盆纪地层广布测区,南部其昌岭基底隆起导致区内古地理环境的巨大变迁,岩石组合复杂,岩相类型多样,致使区内不同时期、同一时期不同区域的岩相演化特征有着不同的特点。 相似文献