全文获取类型
收费全文 | 1210篇 |
免费 | 228篇 |
国内免费 | 426篇 |
专业分类
测绘学 | 7篇 |
大气科学 | 98篇 |
地球物理 | 216篇 |
地质学 | 1254篇 |
海洋学 | 149篇 |
天文学 | 7篇 |
综合类 | 46篇 |
自然地理 | 87篇 |
出版年
2024年 | 8篇 |
2023年 | 21篇 |
2022年 | 31篇 |
2021年 | 43篇 |
2020年 | 59篇 |
2019年 | 61篇 |
2018年 | 46篇 |
2017年 | 91篇 |
2016年 | 63篇 |
2015年 | 48篇 |
2014年 | 105篇 |
2013年 | 109篇 |
2012年 | 94篇 |
2011年 | 71篇 |
2010年 | 57篇 |
2009年 | 80篇 |
2008年 | 95篇 |
2007年 | 75篇 |
2006年 | 96篇 |
2005年 | 74篇 |
2004年 | 75篇 |
2003年 | 53篇 |
2002年 | 44篇 |
2001年 | 39篇 |
2000年 | 50篇 |
1999年 | 48篇 |
1998年 | 32篇 |
1997年 | 26篇 |
1996年 | 25篇 |
1995年 | 27篇 |
1994年 | 21篇 |
1993年 | 24篇 |
1992年 | 23篇 |
1991年 | 11篇 |
1990年 | 15篇 |
1989年 | 3篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有1864条查询结果,搜索用时 296 毫秒
951.
Tassilo Herrschel 《Applied geography (Sevenoaks, England)》1997,17(4):267-281
Economic transformation in post-socialist eastern Germany revealed inherent inequalities in development opportunities, which had been disguised during the socialist ancien régime. Using local examples from the two contrasting Länder of Mecklenburg-Vorpommern and Saxony, this paper explores how market forces not only exposed these differences, but further entrenched them at the regional and local scales. Local economies demonstrate the differential development very clearly, exposing the significance of regional economic context and raisons d'être of local economic structures. This is genuine locational advantages vis-à-vis activities imposed through ideology rather than economy-driven decrees by the old GDR regime. Many of these state-decreed activities lacked local, and regional, embeddedness, rendering the respective local economies most vulnerable to market operation. They will continue to rely on state support. The problems were exacerbated in those localities lacking support from a regional economy, as in Mecklenburg-Vorpommern. Conversely, market-favoured, economically attractive regions, like Saxony, generally help localities develop their new economic roles, including those with few indigenous advantages. These fundamental differences in opportunities, illustrated here for six cities, are reflected in local policy-making, especially the role of localness and utilization of local identity. 相似文献
952.
松树沟蛇绿岩是东秦岭构造带内出露规模最大的超镁铁—镁铁质杂岩体。地质填图证实,该区存在结构十分复杂的大型逆冲推覆构造系统,其中北区松树沟超镁铁质主岩体内发育的高角度逆冲断层系向北拆离;而包括富水杂岩在内的南区镁铁质及超镁铁质岩块均向南大规模逆掩;剖面上总体构成不对称(向南滑脱为主)的“背冲型”样式。松树沟逆冲推覆构造研究对恢复蛇绿岩组合层序及其古构造环境具有重要的地质意义。 相似文献
953.
本文认为环境岩土工程问题与污染和生态破坏环境问题是等价的。所以,存在着两类同样重要的环境问题。关于两类环境问题的类型划分和内容,文中做了系统介绍和讨论。并着重对我国东部3个有重要意义的主要环境岩土工程问题进行了分析。 相似文献
954.
东秦岭地区原划为泥盆系的“刘岭群”被一条大型韧性推覆剪切带分为南北两个岩系,北部岩系为一套中浅变质的以杂砂岩为主,夹火山熔岩、火山碎屑岩和含陆缘砂碳酸盐岩的沉积-火山建造,其中紧闭、倒转、平卧褶皱和逆冲断层极为发育,沉积学特征及物源分析显示其为早古生代末-晚古生代初华北板块南缘活动大陆边缘沉积;南部岩系为一套由浅变质的粉砂岩、泥质岩、石英砂岩和碳酸盐岩组成的巨厚陆源碎屑沉积,发育东西向陡倾劈理及开阔对称褶皱组成的复式褶皱,沉积学特征和物源分析表明其为晚古生代初期扬子板块北缘沉积。“刘岭群”两岩系的岩性组合、沉积学特征、变质作用、构造变形期次、生物化石特征及形成的大地构造环境等方面的差异足以划分为不同的岩群,“刘岭群”应予解体。 相似文献
955.
956.
荷载微粒闪长质包体是全球范围内Ⅰ型花岗岩的普遍特征,本文对中国东部不同构造域内印支期以来的典型岩体及其荷载微粒闪长质包体进行了对比研究,提出两种岩浆并存的地质、岩石学标志。根据岩石∈Nd_0和T_(DM),模式年龄的大小将花岗岩及其荷载闪长质包体划分为三种组合类型:①花岗岩T_(DM)明显大于或∈Nd_0明显小于荷栽微粒闪长质包体;②花岗岩T_(DM)明显小于或∈Nd_0明显大于微粒闪长质包体;③二者相近。指出三种组合类型分别受①古老地壳区(早元古-太古宙),②较新造山带(古生代以来),③较老地壳区(中、晚元古代)所制约。提出花岗岩及其荷载微粒闪长质包体是分别来自深部地壳不同成分层部分熔融的成因观点。 相似文献
957.
The regional topography of much of the New South Wales Southern Highlands was long attributed to Quaternary erosion, but it has been recently demonstrated that the region was, in fact, well developed by the Eocene. The hillsides at Inverary Park are mantled by the Late‐Eocene Reevesdale Basalt, thus indicating the extent of landscape development by the mid‐Tertiary. Pre‐, intra‐, and post‐basaltic alluvial and lacustrine sediments are compared with the current extent of the basalt, clearly demonstrating the age of this landscape and the paucity of modification since the Late Eocene. Stratigraphic techniques, U/Th, TL and 14C dating aid reconstruction of much of the Cainozoic history of Inverary Park. Major changes in sediment type and source have long been common, but Late Quaternary changes do not correlate well with similar observations elsewhere, suggesting that changes in hydrologic regime, notably climate change, are not necessarily responsible for changes in the stratigraphic record. This landscape development and preservation is also at odds with most models of landscape development. 相似文献
958.
东亚古陆中生代晚期热河生物群的起源、发展、鼎盛与衰亡 总被引:6,自引:0,他引:6
本文探讨东亚古陆独特而著名的“热河生物群”的起源、发展、鼎盛与衰亡的规律;同时也提出其顶底的界限范围。总结和补充笔者于1983年首次提出的关于热河生物群起源于华北、以燕辽为中心,尔后向外扩散和迁移,形成独特的生物区系的观点。 相似文献
959.
Geothermobarometry and development of inverted metamorphism in the Darjeeling-Sikkim region of the eastern Himalayan 总被引:2,自引:0,他引:2
ABSTRACT The Darjeeling-Sikkim region provides a classic example of inverted Himalayan metamorphism. The different parageneses of pelitic rocks containing chlorite, biotite, garnet, staurolite, kyanite, sillimanite, plagioclase and K-feldspar are documented by a variety of textures resulting from continuous and discontinuous reactions in the different zones. Microprobe data of coexisting minerals show that XMg varies in the order: garnet < staurolite < biotite < chlorite. White mica is a solid solution between muscovite and phengite. Garnet is mostly almandine-rich and shows normal growth zoning in the lower part of the Main Central Thrust (MCT) zone, and reverse zoning in the upper part of the zone. Chemographical relations and inferred reactions for different zones are portrayed in AFM space. In the low-grade zones oriented chlorites and micas and rolled garnets grew syntectonically, and were succeeded by cross-cutting chlorites and micas and garnet rims. In the upper zones sillimanite, kyanite and staurolite crystallized during a static inter-kinematic phase. P-T contitions of metamorphism, estimated through different models of geothermobarometry, are estimated to have been 580°c for the garnet zone to a maximum of 770°c for the sillimanite zone. The preferred values of pressure range from 5.0 kbar to 7.7 kbar. Models to explain the inverted metamorphism include overthrusting of a hot high Himalayan slab along a c. 5 km wide ductile MCT zone and the syn- or post-metamorphic folding of isograds. 相似文献
960.