全文获取类型
| 收费全文 | 581篇 |
| 免费 | 34篇 |
| 国内免费 | 81篇 |
专业分类
| 测绘学 | 10篇 |
| 大气科学 | 3篇 |
| 地球物理 | 39篇 |
| 地质学 | 244篇 |
| 海洋学 | 59篇 |
| 天文学 | 313篇 |
| 综合类 | 18篇 |
| 自然地理 | 10篇 |
出版年
| 2024年 | 3篇 |
| 2023年 | 4篇 |
| 2022年 | 5篇 |
| 2021年 | 3篇 |
| 2020年 | 8篇 |
| 2019年 | 18篇 |
| 2018年 | 7篇 |
| 2017年 | 11篇 |
| 2016年 | 13篇 |
| 2015年 | 14篇 |
| 2014年 | 18篇 |
| 2013年 | 11篇 |
| 2012年 | 22篇 |
| 2011年 | 16篇 |
| 2010年 | 23篇 |
| 2009年 | 30篇 |
| 2008年 | 46篇 |
| 2007年 | 38篇 |
| 2006年 | 41篇 |
| 2005年 | 48篇 |
| 2004年 | 41篇 |
| 2003年 | 29篇 |
| 2002年 | 34篇 |
| 2001年 | 31篇 |
| 2000年 | 37篇 |
| 1999年 | 33篇 |
| 1998年 | 35篇 |
| 1997年 | 13篇 |
| 1996年 | 14篇 |
| 1995年 | 10篇 |
| 1994年 | 7篇 |
| 1993年 | 7篇 |
| 1992年 | 4篇 |
| 1991年 | 9篇 |
| 1989年 | 1篇 |
| 1988年 | 7篇 |
| 1987年 | 3篇 |
| 1986年 | 2篇 |
排序方式： 共有696条查询结果，搜索用时 15 毫秒
681.
682.
癞子岭岩体具有极好的垂向分带性,从下部到顶部包括了花岗岩、云英岩和伟晶岩,其中云英岩以其厚度巨大,云母类型属于铁锂云母,黄玉含量高,W-Sn-Nb-Ta含量高,而区别于其他地区云英岩。通过对癞子岭云英岩进行岩石学、地球化学和矿物学的研究,本文得出:癞子岭云英岩是高硅的强过铝质岩石类型,全碱含量低(3~4.3 wt%),富集挥发组分,全岩Zr/Hf(~8)和Nb/Ta(~1.7)比值低。造岩矿物铁锂云母中Nb(~74×10~(-6))、Ta(~66×10~(-6))、W(~23×10~(-6))、Sn(~75×10~(-6))等成矿元素含量较高。副矿物锆石自形且成分均一,含有HfO_2约10 wt%,Zr/Hf比值最低为5,与云英岩下部的癞子岭钠长花岗岩中的锆石成分有连续过渡的关系。这些特征与南岭地区高演化稀有金属花岗岩或伟晶岩相当,体现了相近的演化程度。癞子岭云英岩中有明显的Nb-Ta-W-Sn成矿作用发生,主要形成铌铁矿族矿物、锡石和黑钨矿,成分和结构均具有岩浆成因特征。花岗质熔体中含有大量挥发组分Li和F,结晶出黄玉和Li-F云母,F在稀有金属的成矿作用和云英岩的成岩过程中发挥了非常重要的作用,成矿作用发生在岩浆演化的晚期并伴随有流体作用。因此,云英岩可能是钠长花岗岩高度分异演化之后的特殊产物,这为研究花岗岩岩浆-热液体系成岩成矿过程提供了新的窗口。 相似文献
683.
684.
湖南沩山岩体多期云母的Rb-Sr同位素年龄和矿物化学组成及其成岩成矿指示意义 总被引：5，自引：5，他引：0
华南分布了大量的印支期-燕山期复式花岗岩体,其成岩及相关成矿过程一直存有争议。本文选择湖南典型的花岗质复式大岩基——沩山岩体为例,通过细致研究其中多期云母的单颗粒Rb-Sr年龄及地球化学组成,探讨了它们对相关成岩成矿过程的指示意义。单颗粒云母Rb-Sr等时线定年结果显示,沩山复式花岗岩主体唐市黑云母二长花岗岩中黑云母结晶年龄为221.9±5.8Ma(MSWD=3.8),主体边部的新浦高演化花岗岩中黑云母结晶年龄为227.0±13Ma(MSWD=1.6),主体内部的巷子口二云母花岗岩中白云母结晶年龄为210.1±3.3Ma(MSWD=0.21)。电子探针主量元素及激光探针LA-ICM-MS微量元素测定结果表明,沩山复式花岗岩中黑云母或白云母的成分存在明显差异,由此指示该岩体多期岩浆的温度、氧逸度以及源岩浆成分的差异。本文研究还表明,巷子口二云母花岗岩中白云母属于次生白云母,不能用来限定岩浆源区深度及岩石成因。鉴于多期云母的成分分异趋势及指示意义,我们认为沩山复式花岗岩多期岩浆具有同源关系,均来自于同一深部大岩浆房,是在不同时期不同构造背景下经历分离结晶和/或同化混染作用侵位而成。其中,印支晚期及之后的二云母花岗岩可能最具铀矿找矿前景。 相似文献
685.
《International Geology Review》2012,54(2):145-165
Two sediment cores from the inner continental shelf of SW India, SK‐148/13 (4.66 m long; from 50 m water depth) and SK‐148/14 (5.37 m long; from 22 m water depth), were studied for provenance and palaeomonsoonal implications. Sediment layers at different depth intervals in these cores were estimated for clay minerals and organic matter content. Five surface sediment samples from the nearby Kali River estuary of the adjacent hinterland were also analysed for clay mineral contents. In both cores and Kali River sediments, smectite is the dominant clay followed by illite, and kaolinite or chlorite. Based on the similarities of the abundances of clay minerals and their relative wt‐% in the inner shelf sediment cores and in surface sediments of the estuary as demonstrated by significance tests, Al‐rich illite, and negligible contribution of clay from the deep‐sea and aeolian sources, it can be inferred that the sediments of the two inner continental shelf cores were derived from the adjacent hinterland. Application of statistical discordancy and significance tests on the down‐core variations in the crystallinity index (CI) of illite and organic matter content in the sediment cores indicates intense monsoonal (high rainfall) conditions at the adjacent hinterland during about 4300–6200 and 9300–10,400 years BP. These inferences are comparable to those from other well‐established palaeomonsoonal indicators such as sedimentation rates and mineral magnetic properties. The CI of illite, an easily determinable and climatically sensitive parameter, can thus be a reliable palaemonsoonal indicator for inner shelf sediment cores. The statistical methodology used in this work highlights the advantages of a quantitative interpretation of the data instead of the conventional qualitative visual examination. 相似文献
686.
短波红外光谱技术在浅剥蚀斑岩铜矿区勘查中的应用——以西藏念村矿区为例 总被引：14，自引：5，他引：9
作为世界上最重要的一种矿床类型,斑岩铜矿一直是工业界勘查的首选.对此类矿床的勘查,在中-深剥蚀程度的矿区相对简单,而在浅剥蚀的矿区则变得较为困难,这是因为在浅剥蚀的矿区,矿床热液/矿化中心很难快速有效定位.近年来,在矿产勘查领域逐渐得到广泛应用的短波红外光谱技术,可通过特定蚀变矿物反射光谱特征参数系统变化的规律来厘定热液/矿化中心,在块状硫化物及浅成低温矿床中显示出良好的应用效果,这为浅剥蚀斑岩铜矿热液/矿化中心的快速、有效厘定提供了一种途径.为此,文章选择了位于冈底斯斑岩铜矿带东段、剥蚀较弱的念村(即夏玛日)矿区,拟通过矿区样品短波红外光谱的系统测量,寻找出蚀变矿物反射光谱特征参数系统变化的规律,进而约束矿床热液/矿化中心.本次研究在念村矿区共识别出7种蚀变矿物,按出现频率由多至少依次为伊利石、绿泥石、蛋白石、叶蜡石、高岭石、绿帘石及多硅白云母;而且,矿区外围以伊利石-绿泥石±绿帘石蚀变矿物组合为主,向内逐渐过渡为伊利石±蛋白石、伊利石-叶蜡石±高岭石组合.通过对伊利石反射光谱特征参数的计算发现,伊利石结晶度及Al-OH吸收峰位,这些通常被认为与伊利石形成温度有关的光谱学参数,在该矿区呈现出系统的变化规律:在矿区东北部,伊利石结晶度较大(＞1.6),Al-OH吸收峰位较小(＜2 203 nm),而该区域的外围,伊利石结晶度变小,Al-OH吸收峰位变大.这表明矿区东北部伊利石的形成温度更高,暗示该区域可能为矿床热液/矿化中心.因此,建议在本次研究所圈定的热液/矿化中心范围内,在适当开展物探工作的基础上,尽快布置勘查工程进行验证,以实现矿床的尽快查找和突破. 相似文献
687.
Shales of the Silurian Dadaş Formation exposed in the southeast Anatolia were investigated by organic geochemical methods. The TOC contents range from 0.24 to 1.48 wt% for the Hazro samples and 0.19 to 3.58 wt% for the Korudağ samples. Tmax values between 438 and 440 °C in the Hazro samples indicate thermal maturity; Tmax values ranging from 456 to 541 °C in the Korudağ samples indicate late to over-maturity. Based on the calculated vitrinite reflectance and measured vitrinite equivalent reflectance values, the Korudağ samples have a maximum of 1.91%R(g-v), in the gas generation window, while a maximum value of 0.79%R(amor-v) of one sample from the Hazro section is in the oil generation window. Illite crystallinity (IC) values of all samples are consistent with maturity results.Pr/Ph ratios ranging from 1.32 to 2.28 and C29/C30 hopane ratios > 1.0 indicate an anoxic to sub-oxic marine-carbonate depositional environment.The Hazro shales do not have any shale oil or shale gas potential because of their low oil saturation index values and early to moderate thermal maturation. At first glance, the Korudağ shales can be considered a shale gas formation because of their organic richness, thickness and thermal over-maturity. However, the low silica content and brittle index values of these shales are preventing their suitability as shale gas resource systems. 相似文献
688.
This study uses illite crystallinity,chlorite crystallinity,illite polytypes,the b_0 cell-dimension of K-white mica,clay mineral assemblages and mineral geothermo-geobarometers to investigate the overprint of diagenesis and metamorphism on the Meso-Neoproterozoic and the Lower Paleozoic along the profile Yueyang-Linxiang in northeastern Hunan Province,China.Illite crystallinity Kbler index(KI) of the 2μm fractions ranges from 0.225 to 0.485°Δ2θ while chlorite crystallinity Arkai index(AI) ranges from 0.244 to 1.500°Δ2θ.This indicates that the Meso-Neoproterozoic and the Lower Paleozoic along the profile Yueyang-Linxiang were overprinted with diagenesis and anchi- to epimetamorphism.Peak metamorphic temperature is estimated with the IV site chlorite geothermometer roughly at 360℃.The b_0 cell dimension values of illites(K-mica) range from 0.9002 to 0.9054 nm and,on average,at 0.9030 nm for the Meso-Neoproterozoic.Based on cumulative frequency curves of illite(K-mica) b_0 cell dimension,the peak metamorphic pressure of the MesoNeoproterozoic along the profile Yueyang-Linxiang is derived of an intermediate pressure type.Most illites occur in the 2M_1 polytype and some of them in a mixture of 2M1+1M types especially those in the Paleozoic.This result partly agrees with the conclusion of the lower greenschist and greenschist facies of the Lengjiaxi and Banxi Groups.However,it is not agreed with the sedimentary cover from the Sinian to the Lower Paleozoic or from the Banxi Group to the Lower Paleozoic.Crustal thickening due to "collision" between the Yangtze and Cathaysia blocks led to an increase in the thickness of the Meso-Neoproterozoic to ca.14 km and resulted in a temperature increase in those rocks due to burial.The very low grade to low grade metamorphism overprinting the Meso-Neoproterozoic implies that the so called "Chiangnania or Jiangnan orogen" was no relative with the "Grenvillian orogeney;instead,it might be a continuous amalgamation product between the Yangtze and Cathaysia blocks. 相似文献
689.
湘北杨家坪中新元古宇和下古生界的近变质作用与成岩作用 总被引：1，自引：1，他引：0
运用伊利石结晶度、K云母晶格常数b0、应变值τ、颗粒大小分布与矿物组合分析等低温变质指示数据对湘北杨家坪剖面中晚元古宇和下古生界的近变质作用和成岩作用进行了研究。Kisch国际标样用于校正伊利石结晶度的测定。中晚元古宇伊利石结晶度Kübler指数范围为:0.21~0.24°Δ2θ,而下古生界为0.28~0.67°Δ2θ。表明近变质作用影响了中晚元古宇和部分下古生界。按照Kisch国际标样的成岩/变质界限(0.21~0.38°Δ2θ,CuKα),将剖面划分为北部近变质带和中南部成岩带。由绿泥石化学成分地质温度计估计近变质峰期温度约为260℃。K云母晶格常数b0值变化范围0.9000~0.9045nm,平均为0.9017nm,表明近变质作用处于中压-中低压力范围。近变质带伊利石(主要是中晚元古宇)的多型为2M1型,而成岩带伊利石(主要是下古生界)的多型为2M1+1M混合类型。平均对数粒度与对数方差之积(GLR)称为对数总成熟效应具有不同的两组分布特征即近变质作用区(GLR1.88)与成岩作用区(GLR1.88),这是一个新的发现。后变质作用的构造应力不仅可产生断层,而且可引起矿物的应变,从而导致衍射峰的宽化,使得近变质带伊利石结晶度值次生变大到成岩值范畴。与剖面南部地区(长沙-澧陵-浏阳,黄土店-仙溪,沅古坪)比较,杨家坪剖面中晚元古宇和下古生界经历了中压-中低压近变质作用和成岩作用的影响。这一结果与多数前人认为的"元古宇板溪群处于绿片岩相或亚绿片岩相或低绿片岩相而震旦到下古生界为沉积盖层"的观点不同。 相似文献
690.