全文获取类型
收费全文 | 158篇 |
免费 | 9篇 |
国内免费 | 29篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 9篇 |
地球物理 | 16篇 |
地质学 | 134篇 |
海洋学 | 7篇 |
天文学 | 2篇 |
综合类 | 14篇 |
自然地理 | 13篇 |
出版年
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 5篇 |
2018年 | 3篇 |
2017年 | 19篇 |
2016年 | 13篇 |
2015年 | 12篇 |
2014年 | 6篇 |
2013年 | 4篇 |
2012年 | 3篇 |
2011年 | 6篇 |
2010年 | 7篇 |
2009年 | 11篇 |
2008年 | 10篇 |
2007年 | 12篇 |
2006年 | 6篇 |
2005年 | 7篇 |
2004年 | 4篇 |
2003年 | 6篇 |
2002年 | 7篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 3篇 |
1983年 | 1篇 |
排序方式: 共有196条查询结果,搜索用时 109 毫秒
51.
海拉尔盆地海参1井伊敏组孢粉组合的地层意义 总被引:3,自引:0,他引:3
海参1井伊敏组孢粉化石异常丰富,自下而上可以划分出3个孢粉组合:Impardecispora-Cyathidites-Clavatipollenites组合,Stereisporites-Deltoidospora-Asteropollis组合,Appendicisporites-Asteropollis-Tricolpites组合,分别分布于伊敏组一段、二段和三段,组合特征明显,是海拉尔盆地乌尔逊凹陷划分伊敏组与大磨拐河组的重要生物依据之一,更是伊敏组内三段划分和井间对比的生物依据之一。3个孢粉组合中见有属种繁多的海金沙科孢子及其他繁盛于早白垩世中晚期的孢子花粉,结合在绝大多数样品中发现的早期被子植物花粉的情况分析,推测含这3个孢粉组合的伊敏组地质时代为早白垩世巴列姆期—早阿尔必期(Barremian—Early Albian)。 相似文献
52.
从浙江天台白垩纪蛋化石复原恐龙类群 总被引:2,自引:1,他引:2
浙江天台盆地白垩纪地层中,已发现了甲龙类及慢龙类等恐龙骨骼化石及数以千计的蛋化石,其中许多为恐龙蛋化石。根据国内外相同类型的蛋化石中迄今已发现的恐龙胚胎化石研究成果,可大致确定其中一部分蛋化石分别是由鸭嘴龙类、巨龙类、慢龙类、盗蛋龙类、伤齿龙类和暴龙类等恐龙所产。并发现鸭嘴龙类、巨龙类和慢龙类的圆形蛋、副圆形蛋在数量上占绝大多数,盗蛋龙的长形蛋和伤齿龙的棱柱形蛋较少,暴龙类的巨型长形蛋最少,从而反映了他们各自在生态金字塔中的位置。 相似文献
53.
The downturn in temperature in the late medieval period is likely to have had significant impact upon insect distribution. Despite the amount of study fossil insect faunas have been afforded, there is presently little convincing evidence of climatic, rather than human impact upon faunas during the "Little Ice Age". This probably reflects as much the paucity of suitable sites, as the overarching scale of habitat destruction by Man. 相似文献
54.
Jayasri Banerji 《Cretaceous Research》2000,21(6):781
An angiosperm fruit of uncertain affinity and a questionable flower are reported from the Rajmahal Formation (Early Cretaceous) at the locality of Sonajori, Rajmahal Basin. The remains of ferns, Pentoxylales and conifers have been described previously from this locality. The significant addition of angiosperm megafossil remains confirms that flowering plants were evolving during the Early Cretaceous Epoch in India. The Sonajori assemblage seems to be the youngest fossil assemblage recovered so far from the Rajmahal Basin. It is tentatively dated as Barremian–Aptian. 相似文献
55.
云南新生代断陷盆地的环境地质记录 总被引:1,自引:0,他引:1
盆地的环境地质记录是从盆地的形成、发展演变、沉积物形成的地球化学与古气候环境、沉积物堆积后所经历的压实、成岩来加以研究的。除无机介质(矿物)外的有机质,在成岩压实受热过程中化学成分与结构的变化,也是盆地环境地质记录的一部分,环境地质研究的归宿是对矿产—化石燃料形成与潜能的估价,完整的研究应该包括化石燃料形成(成烃成煤)环境及成藏(保存)环境等。对云南滇西陇川、瑞丽及保山等三个新生代断陷盆地环境地质记录的研究揭示,在极其相似的盆地形成演变、沉积地球化学与古气候、成岩与成烃背景基础上,化石燃料的形成与潜能在三个盆地具有差异性;指出陇川盆地以找寻煤型气及初熟(低熟)油为主,保山盆地以寻找浅部生物成因气及煤型气为主,瑞丽盆地相对潜能较差,仅有生物气浅部产出的可能。 相似文献
56.
Carbon capture and storage (CCS) is increasingly depicted as an important element of the carbon dioxide mitigation portfolio. However, critics have warned that CCS might lead to “reinforced fossil fuel lock-in”, by perpetuating a fossil fuel based energy provision system. Due to large-scale investments in CCS infrastructure, the fossil fuel based ‘regime’ would be perpetuated to at least the end of this century.In this paper we investigate if and how CCS could help to avoid reinforcing fossil fuel lock-in. First we develop a set of criteria to estimate the degree of technological lock-in. We apply these criteria to assess the lock-in reinforcement effect of adding CCS to the fossil fuel socio-technical regime (FFR).In principle, carbon dioxide could be captured from any carbon dioxide point source. In the practice of present technological innovations, business strategies, and policy developments, CCS is most often coupled to coal power plants. However, there are many point sources of carbon dioxide that are not directly related to coal or even fossil fuels. For instance, many forms of bio-energy or biomass-based processes generate significant streams of carbon dioxide emissions. Capturing this carbon dioxide which was originally sequestered in biomass could lead to negative carbon dioxide emissions.We use the functional approach of technical innovations systems (TIS) to estimate in more detail the strengths of the “niches” CCS and Bio-Energy with CCS (BECCS). We also assess the orientation of the CCS niche towards the FFR and the risk of crowding out BECCS. Next we develop pathways for developing fossil energy carbon capture and storage, BECCS, and combinations of them, using transition pathways concepts. The outcome is that a large-scale BECCS development could be feasible under certain conditions, thus largely avoiding the risk of reinforced fossil fuel lock-in. 相似文献
57.
Androecium of the earliest known flowering plant Archaefructus liaoningensis was found from the Upper Jurassic Jianshangou Formation of western Liaoning, China. The androecium consists of numerous stamens bearing in pair on the reproductive axes below conduplicate carpels. The stamens are composed of a short filament and basifixed anther for each. Monosulcate pollen in situ are found from the anthers. The characters of the androecium reveals that Archaefructus are probably protandrous, and the paired stamens and monosulcate pollen appear to indicate that Archaefructus, as primitive angiosperms,might be derived from extinct seed -ferns during the Older Mesozoic. Archaefructus is considered Late Jurassic in age. 相似文献
58.
田师傅植物群系我国北方典型的早中侏罗世植物群之一,产自辽宁本溪田师傅盆地及风城赛马-(?)阳盆地的下侏罗统长梁子组、中侏罗统大堡组及三个岭组。该植物群由34属77种植物组成。本文通过含植物化石地层剖面简介阐明化石的产地和层位,对以往的化石名单进行修订,对部分重要化石作了描述。 相似文献
59.
辽东本溪田师傅和新开岭地区出露的一套沉积碎屑岩,范国清(1982年)称为东营坊组,时代隶属晚侏罗世。本文依据 Euestheria ziliujinensis 群将东营坊组时代置于中侏罗早中期,与辽西海房沟组、冀北九龙山组叶肢介动物群主体基本一致。依据 Pagiophyllum cf.maculosum,P.cf.shahoziensis,Brachyphyllumcf.mamillare,Coniopteris sp.等植物化石和区域地层接触关系,东营坊组应置于转山子组、大堡组和三个岭组之上。 相似文献
60.
IntroductionArchaefructus ,theoldestknownangiosperms ,werefoundfromtheUpperJurassicJianshangouFormation (i.e .theformerlowerpartofYi 相似文献