全文获取类型
收费全文 | 1606篇 |
免费 | 187篇 |
国内免费 | 241篇 |
专业分类
测绘学 | 180篇 |
大气科学 | 114篇 |
地球物理 | 255篇 |
地质学 | 753篇 |
海洋学 | 261篇 |
天文学 | 231篇 |
综合类 | 101篇 |
自然地理 | 139篇 |
出版年
2024年 | 9篇 |
2023年 | 13篇 |
2022年 | 36篇 |
2021年 | 56篇 |
2020年 | 43篇 |
2019年 | 54篇 |
2018年 | 36篇 |
2017年 | 57篇 |
2016年 | 52篇 |
2015年 | 79篇 |
2014年 | 92篇 |
2013年 | 75篇 |
2012年 | 102篇 |
2011年 | 89篇 |
2010年 | 82篇 |
2009年 | 90篇 |
2008年 | 114篇 |
2007年 | 133篇 |
2006年 | 94篇 |
2005年 | 99篇 |
2004年 | 82篇 |
2003年 | 86篇 |
2002年 | 83篇 |
2001年 | 50篇 |
2000年 | 66篇 |
1999年 | 49篇 |
1998年 | 34篇 |
1997年 | 60篇 |
1996年 | 23篇 |
1995年 | 14篇 |
1994年 | 9篇 |
1993年 | 15篇 |
1992年 | 9篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1976年 | 1篇 |
1971年 | 1篇 |
1921年 | 1篇 |
1919年 | 1篇 |
1905年 | 1篇 |
1897年 | 2篇 |
1880年 | 2篇 |
1877年 | 2篇 |
1875年 | 1篇 |
排序方式: 共有2034条查询结果,搜索用时 359 毫秒
131.
132.
直流电法在探测老窑采空区的应用 总被引:1,自引:1,他引:1
在各种工程地质、环境地质中、对地下采空区的探测是地球物理勘探的一项重要内容。文章从物性参数研究、技术方法择方面入手,探讨了直流电法探测老窑采空区的可行性,并以实例介绍了解决该问题所取得的经验。 相似文献
133.
岩石变形所反映的地震作用过程--第13届国际变形机理、流变学和构造学学术会议概述 总被引:2,自引:0,他引:2
简要介绍了第13届国际变形机理、流变学和构造学学术会议的概况和特点,综述了地震变形作用的研究现状。 相似文献
134.
Fluid-rock history of granulite facies humite-marbles from Ambasamudram, southern India. 总被引:1,自引:0,他引:1
An extensive humite‐bearing marble horizon within a supracrustal sequence at Ambasamudram, southern India, was studied using petrological and stable isotopic techniques to define its metamorphic history and fluid characteristics. At peak metamorphic temperatures of 775±73°C, based on calcite‐graphite carbon isotope thermometry, the mineral assemblages suggest layer‐by‐layer control of fluid compositions. Clinohumite + calcite‐bearing assemblages suggest XCO2 < 0.4 (at 700°C and 5 kbar), calcite + forsterite + K‐feldspar‐bearing assemblages suggest XCO2>0.9 (at 790°C); and local wollastonite + scapolite + grossular‐bearing zones formed at XCO2 of c. 0.3. Retrograde reaction textures such as scapolite + quartz symplectites after feldspar and calcite and replacement of dolomite + diopside or tremolite+dolomite after calcite+forsterite or calcite+clinohumite are indicative of retrogression under high XCO2 conditions. Calcite preserves late Proterozoic carbon and oxygen isotopic signatures and the marble lacks evidence for extensive retrograde fluid infiltration, while during prograde metamorphism the possible infiltration of aqueous fluids did not produce significant isotopic resetting. Isotopic zonation of calcite and graphite grains was likely produced by localized CO2 fluid infiltration during retrogression. Contrary to the widespread occurrence of humite‐marbles related to retrograde aqueous fluid infiltration, the Ambasamudram humite‐marbles record a prograde‐to‐peak metamorphic humite formation and retrogression under conditions of low XH2O. 相似文献
135.
钢筋混凝土框架砖填充墙结构抗震性能的研究 总被引:12,自引:5,他引:12
本文介绍了一个1/3比例框架填充墙结构模型模拟地震振动台试验,研究了结构动力特性与反应特征,提出了钢筋混凝土框架砖填充墙结构层间刚度与抗力的简化估计方法和公式,同时进行了多层框架填充墙结构的弹塑性动力反应分析并结合试验模型将计算结果与试验结果进行比较。 相似文献
136.
吉黑东部斑岩型-浅成热液型铜金矿床多重成矿模型 总被引:5,自引:0,他引:5
通过四个典型矿床(小西南岔、闹枝、五凤和刺猬沟)的对比,发现它们在形成时间-空间一成因上既相互联系,又相互区别。小西南岔和闹枝矿床存在三个成矿流体系统:加热天水系统(A)、排放流体系统(B)、蒸气缕(steam plume)反应系统(C);五凤和刺猬沟矿床只有一个成矿流体系统,即排放流体系统(B)。前者的成矿流体由浅成岩浆房的补给;后者的成矿流体主要为循环天水,浅成岩浆房的补给不明显。小西南岔金铜矿床产于中生代火山岩盆地边缘的隆起带,属于斑岩型矿床;闹枝金(铜)矿床产于中生代火山岩盆地内的断隆块,属于斑岩-浅成热液过渡型矿床;五凤和刺猬沟金(银)矿床产于中生代火山岩盆地内断裂带,属于浅成热液型矿床。在区域成矿上,由浅入深,浅成热液型斑岩-浅成热液过渡型和斑岩型构成多重成矿模型。 相似文献
137.
吉黑东部斑岩型-浅成热液型铜金矿床多重成矿模型 总被引:9,自引:2,他引:9
通过四个典型矿床(小西南岔、闹枝、五凤和刺猬沟)的对比,发现它们在形成时间-空间-成因上既相互联系,又相互区别。小西南岔和闹枝矿床存在三个成矿流体系统:加热天水系统(A)、排放流体系统(B)、蒸气缕(steamplume)反应系统(C);五凤和刺猬沟矿床只有一个成矿流体系统,即排放流体系统(B)。前者的成矿流体由浅成岩浆房的补给;后者的成矿流体主要为循环天水,浅成岩浆房的补给不明显。小西南岔金铜矿床产于中生代火山岩盆地边缘的隆起带,属于斑岩型矿床;闹枝金(铜)矿床产于中生代火山岩盆地内的断隆块,属于斑岩-浅成热液过渡型矿床;五凤和刺猬沟金(银)矿床产于中生代火山岩盆地内断裂带,属于浅成熟液型矿床。在区域成矿上,由浅入深,浅成热液型斑岩-浅成热液过渡型和斑岩型构成多重成矿模型。 相似文献
138.
Sunil Bharati Richard L. Patience Steve R. Larter Guy Standen Iain J. F. Poplett 《Organic Geochemistry》1995,23(11-12)
The significance and validity of integrating data obtained from a variety of analytical techniques to understand, elucidate and model kerogen's complex chemical structure is reported here using degradative (open and closed system pyrolysis, chemical oxidation), non-degradative (13C CP/MAS NMR) and optical (incident white light and blue light) methods. Seven Cambrian Alum Shale samples, ranging in maturity from immature to post-mature with respect to petroleum generation, were studied and were chosen for their simple geological history, uniform organic matter type and high organic carbon content. The Alum Shale kerogens, which primarily consist of algal organic matter, liberate low molecular weight gaseous and aromatic compounds on pyrolysis and give mostly branched dicarboxylic acids on chemical oxidation. 13C NMR spectroscopy shows that the Alum Shale kerogens are anomalously rich in oxygen-bearing functional groups (such as C = O, ArCO, CHO, CHxO), most of which apparently remain intact within the kerogen macro-molecule (KMM) through the diagenetic and catagenetic stages. Fragments released by different degradative techniques are quantified and the aromaticity (fa), O/C and relative proportions of various carbon types estimated by 13C NMR. A synthesis of these data has allowed us to better understand the chemistry of the Alum Shale kerogen. 相似文献
139.
Abstract Isotopic analyses of organic carbon from the mid-Cretaceous sequence in Hokkaido, Japan, revealed a 2‰ positive excursion of δ13C values at the biostratigraphically defined Cenomanian/Turonian (C/T) boundary recognized in the Yezo Group. The planktonic foraminiferal Whiteinella archaeocretacea Zone, which is known to bracket the Cenomanian/Turonian boundary elsewhere in the world, was recognized in the Oyubari area of central Hokkaido based on the distribution of commonly occurring planktonic foraminifera. In the Tappu area of northwestern Hokkaido, where diagnostic planktonic foraminifera are rare but calcareous nannoplankton occur commonly, the interval coeval with the W. archaeocretacea Zone can also be established by recognizing the conjoined last appearance levels of Corollithion kennedyi and Axopodorhabdus albianus, both calcareous nannoplankton species. Carbon isotope profiles exhibit a similar pattern with comparable peaks and troughs occurring in the same stratigraphic position in the sequences. A prominent, positive 2‰ shift of δ13C values, here called ‘δ13C spike’ occurs in the middle of the W. archaeocretacea Zone in the Oyubari area and just above the conjoined last appearances of the two above-mentioned nannoplankton taxa in the Tappu area. The Cenomanian/Turonian boundary can be drawn just above the peak position of the spike in both sections. The Rock Eval analyses and biomarker analyses of organic carbon indicate that organic carbon subjected to our isotope analyses is of terrestrial origin. Therefore, the observed 2%o shift should reflect changes in the isotopic composition of the atmospheric CO2. A unique layer composed predominantly of sand-grain sized spumellarian Radiolaria is present immediately above the δ13C spike both in the Oyubari and Tappu areas, suggesting an increasing availability of both nutrients and silica in surface waters. 相似文献
140.
陈高云 《成都信息工程学院学报》1999,(4):11
说明了用图形方式展现C程序运行情况的必要性和可行性;介绍了用图形演绎C程序运行的总设计思想;详细介绍了图形界面设计要求和程序模块的功能要求。 相似文献