全文获取类型
收费全文 | 677篇 |
免费 | 97篇 |
国内免费 | 215篇 |
专业分类
测绘学 | 5篇 |
大气科学 | 13篇 |
地球物理 | 261篇 |
地质学 | 621篇 |
海洋学 | 20篇 |
天文学 | 4篇 |
综合类 | 39篇 |
自然地理 | 26篇 |
出版年
2024年 | 2篇 |
2023年 | 7篇 |
2022年 | 16篇 |
2021年 | 16篇 |
2020年 | 22篇 |
2019年 | 14篇 |
2018年 | 13篇 |
2017年 | 25篇 |
2016年 | 28篇 |
2015年 | 16篇 |
2014年 | 30篇 |
2013年 | 35篇 |
2012年 | 21篇 |
2011年 | 51篇 |
2010年 | 61篇 |
2009年 | 52篇 |
2008年 | 65篇 |
2007年 | 61篇 |
2006年 | 38篇 |
2005年 | 45篇 |
2004年 | 34篇 |
2003年 | 30篇 |
2002年 | 28篇 |
2001年 | 15篇 |
2000年 | 26篇 |
1999年 | 31篇 |
1998年 | 32篇 |
1997年 | 23篇 |
1996年 | 35篇 |
1995年 | 14篇 |
1994年 | 17篇 |
1993年 | 14篇 |
1992年 | 16篇 |
1991年 | 5篇 |
1990年 | 10篇 |
1989年 | 9篇 |
1988年 | 15篇 |
1987年 | 6篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有989条查询结果,搜索用时 15 毫秒
81.
The X-drilling cores of the North Yellow Sea basin reveal two sets of Mesozoic clastic rocks, which are the dark rocks in lower part and the red rocks in upper part, respectively. There are two layers of volcanic rocks at the bottom and the upper part of the dark rock unit. The volcanic rocks at the bottom part are trachytic dacite while rocks at the upper part are clastic dacite. The zircon grains from the upper and lower units of volcanic rocks are euhedral-subhedral columnar crystals and show oscillatory zoning on cathodoluminescence images. 22 tests of zircons in the trachytic dacite from the bottom part yield an age of 141-151 Ma, with weighted mean 206Pb/238U age of 145±2 Ma. Whereas 18 tests of zircons from the sample at the upper part give 206Pb/238U ages around 139-149 Ma with weighted mean 206Pb/238U age of 141±2 Ma, which implies that the X well volcanic rocks belong to Late Jurassic-Early Cretaceous. Comparing with the age and geochemical characteristics of the Mesozoic igneous rocks in Shandong peninsula, we suggest that the igneous rocks from both the North Yellow Sea basin and Jiaolai basin were formed under same dynamic setting, i.e., the subduction related volcano arc and back-arc extension. ©, 2015, Science Press. All right reserved. 相似文献
82.
Fjords are semi-enclosed systems often with usually strong physical and chemical gradients. These gradients provide the opportunity to test the influence of various physical and chemical factors on biodiversity. However study area of this investigation, Trondheimsfjord, is a large water body where especially salinity gradient along the fjord is not well pronounced. The goal of this study was to establish within a temperate fjord a baseline identifying encrusting fauna on rocks and determine the factors driving changes along the length of the fjord and changing depths. There was no trend in species composition change and increase or decrease in number of species, diversity and number of individuals along the fjord. This was likely due to the relative homogeneity of both substrate (rocks) and environmental parameters. Nevertheless, the influence of fresh water inflow in the vicinity of the river mouth was apparent by the presence of characteristic brackish-water species at these locations. Multidimensional scaling analysis revealed three separate assemblages: intertidal, shallow and deep subtidal (below 50 m). Intertidal assemblages were species poor (one to 11 species) but relatively abundant (six to 2374 indiv./m2 of rocks). Number of individuals and biomass was highest in the shallow subtidal (2059–13,587 indiv./m2 of rocks). Overall the highest species number (45) was recorded at 50 m depth which is probably result of low competition pressure yet still relatively high nutrient concentration in comparison to shallower locations. Environmental parameters (i.e., tidal currents, wave action, salinity) change more drastically with depth than along the fjord and these changes are the major driving forces in shaping encrusting assemblages in Trondheimsfjord. 相似文献
83.
Hazard maps are considered essential tools in the communication of volcanic risk between scientists, the local authorities
and the public. This study investigates the efficacy of such maps for the volcanic island of Montserrat in the West Indies
using both quantitative and qualitative research techniques. Normal plan view maps, which have been used on the island over
the last 10 years of the crisis, are evaluated against specially produced three-dimensional (3D) maps and perspective photographs.
Thirty-two demographically representative respondents of mixed backgrounds, sex, education and location were interviewed and
asked to complete a range of tasks and identification on the maps and photographs. The overall results show that ordinary
people have problems interpreting their environment as a mapped representation. We found respondents’ ability to locate and
orientate themselves as well as convey information relating to volcanic hazards was improved when using aerial photographs
rather than traditional plan view contour maps. There was a slight improvement in the use of the 3D maps, especially in terms
of topographic recognition. However, the most striking increase in effectiveness was found with the perspective photographs,
which enabled people to identify features and their orientation much more readily. For Montserrat it appears that well labelled
aerial and perspective photographs are the most effective geo-spatial method of communicating volcanic risks.
相似文献
Katharine HaynesEmail: |
84.
磁铁矿矿体似层状、透镜状赋存于淇海岩组中上一中部的钠长绿泥片岩、钠长绿泥绿岩、钠长绿帘绿泥片岩中,严格受层位、岩性和构造的控制。 相似文献
85.
石平川钼矿由燕山晚期第四次侵入碱性长石花岗岩体提供物源和热动力,火山机构、断裂和西山头组第二岩性段为成矿提供了导矿通道和容矿场所。 相似文献
86.
87.
火山岩油气藏的研究一般以陆上喷发沉积的火山岩体为主,事实上全世界四分之三的火山活动是在水下发生的,只是水下喷发沉积的火山岩在各个方面的研究还比较少,在勘探中尚未引起注意。本文以三塘湖盆地石炭系火山岩油藏为例,对比分析了陆上与水下喷发沉积形成的火山岩在岩性、颜色、结构构造以及储集空间特征和地震反射特征等方面的差异,指出了三塘湖盆地石炭系哈尔加乌组火山岩为水下喷发环境形成。通过对研究区两种类型的火山岩油藏系统的研究,总结出了水下喷发沉积的火山岩储层的形成机理以及其形成规模油气藏的条件,为今后的火山岩油气藏的勘探指出了新的方向。 相似文献
88.
试论火山岩油气藏成藏机理 总被引:24,自引:3,他引:21
全球100多个国家/地区在火山岩内或其周围发现了油气藏或油气显示,展示了火山岩油气藏勘探的广阔前景。火山岩已从油气勘探的"禁区"转变为了"靶区",成为油气勘探的新目标。火山岩储集物性较好,其本身可直接作为储层,各类侵入体与围岩相互作用还可形成与火成岩有关的圈闭。火山岩油气藏的烃源包括有机成因和无机成因两种。火山作用可以明显提高烃源岩内有机质的成熟度,加快烃的产生,促进油气运移,并为无机成因烃提供合成原料(CO_2和H_2等)和运移通道。虽然火山岩在盆地早期尤为发育,约占盆地充填体积的1/4,但是目前火山岩油气储量仅占世界油气探明储量的1%左右,勘探潜力巨大。中国沉积盆地内发育不同时代火山岩,火山岩储层与烃源岩匹配较好,无机成因气来源丰富,火山岩油气藏正在成为我国油气勘探的重要领域之一。 相似文献
89.
90.
徐家围子断陷营城组火山岩分布特征及火山喷发机制的新认识 总被引:10,自引:0,他引:10
基于深层钻井和连片处理三维地震资料,结合同位素测年,本文对松辽盆地北部徐家围子断陷白垩系营城组火山岩的分布特征及其喷发机制进行了研究。本区火山岩分布广、厚度大、沿深大断裂串珠状分布;纵向上分为下部营一段和上部营三段两套;营一段分布于断陷中部及其以南地区,岩性以酸性为主;营三段分布于断陷中部及其以北地区,酸性和中、基性火山岩均有发育。本区断裂类型及其组合复杂,正、逆、走滑和花状断裂都有发育;两组断裂交汇部位是火山喷发的主要通道。深大断裂与火山岩时空展布关系显示,营一段火山岩主要受徐中断裂控制,由北向南依次喷发,岩性以酸性为主;营三段火山岩主要沿着徐东花状断裂带由南向北依次喷发,表现为基性与酸性交替的双峰式。营城组火山岩喷发类型有三种:裂隙式、中心式与复合式。徐家围子断陷营城组火山岩储集性能优良且毗邻烃源岩,与断裂、源岩及盖层有利匹配,可构成有利的生储盖组合,具有良好的天然气勘探前景。 相似文献