全文获取类型
收费全文 | 555篇 |
免费 | 124篇 |
国内免费 | 83篇 |
专业分类
测绘学 | 16篇 |
大气科学 | 80篇 |
地球物理 | 103篇 |
地质学 | 317篇 |
海洋学 | 68篇 |
天文学 | 14篇 |
综合类 | 63篇 |
自然地理 | 101篇 |
出版年
2024年 | 3篇 |
2023年 | 3篇 |
2022年 | 26篇 |
2021年 | 23篇 |
2020年 | 22篇 |
2019年 | 30篇 |
2018年 | 31篇 |
2017年 | 34篇 |
2016年 | 34篇 |
2015年 | 35篇 |
2014年 | 38篇 |
2013年 | 31篇 |
2012年 | 35篇 |
2011年 | 29篇 |
2010年 | 29篇 |
2009年 | 43篇 |
2008年 | 40篇 |
2007年 | 25篇 |
2006年 | 23篇 |
2005年 | 13篇 |
2004年 | 9篇 |
2003年 | 12篇 |
2002年 | 15篇 |
2001年 | 5篇 |
2000年 | 7篇 |
1999年 | 22篇 |
1998年 | 21篇 |
1997年 | 22篇 |
1996年 | 18篇 |
1995年 | 11篇 |
1994年 | 11篇 |
1993年 | 9篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 13篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有762条查询结果,搜索用时 296 毫秒
551.
552.
Potential Orthopyroxene,Clinopyroxene and Olivine Reference Materials for In Situ Lithium Isotope Determination 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《Geostandards and Geoanalytical Research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ben‐Xun Su Xiao‐Yan Gu Etienne Deloule Hong‐Fu Zhang Qiu‐Li Li Xian‐Hua Li Nathalie Vigier Yan‐Jie Tang Guo‐Qiang Tang Yu Liu Kwan‐Nang Pang Aaron Brewer Qian Mao Yu‐Guang Ma 《Geostandards and Geoanalytical Research》2015,39(3):357-369
Over 1400 electron probe and 700 ion probe microanalyses were performed on eleven mineral separates to evaluate their potential as reference materials for in situ Li isotopic determination. Our results suggest the homogenous distributions of major elements, Li and its isotopes for each sample. Hence, these samples are suitable to be used as reference materials for in situ measurements of Li abundance and Li isotopes by secondary ion mass spectrometry (SIMS) or laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS). These samples have the advantage of mitigating probable matrix effects during calibration owing to the wide range of compositions. The effect of composition on the δ7Li of olivine measured by SIMS is a linear function of composition, with δ7Li increasing by 1.0‰ for each mole per cent decrease in forsterite component. 相似文献
553.
在煤层气勘探中,煤心数据是评价煤层气潜力的重要指标,因此,在煤层气录井中,卡准煤层位置、计算煤层厚度是煤层气测井工作中的一项基础工作。有研究表明,在地质条件复杂及钻井困难的环境下,全烃曲线对煤层的识别具有较高的准确性。以山西王坡V1井640~645m井段煤层判识为例,其全烃解释厚度为3.8m,与测井解释的4.0m相差0.2,与地质解释的3.7m相差0.1m,与全烃曲线校正前4.6m的解释结果比较,校正后的全烃曲线解释成果比较可靠。 相似文献
554.
555.
根据大量岩石薄片观察、扫描电镜和X?衍射分析,研究陇东地区典型区块三叠系延长组长6—长8段特低渗透—致密砂岩的岩石学特征、孔隙成因等,探讨成岩作用类型及主要控制因素,剖析延长组长6与长8成岩作用的差异性。研究表明:该区砂岩经历的成岩作用主要有压实作用、胶结作用、溶解作用等,建立了三角洲和重力流成岩演化模式序列,研究区目前处于中成岩A?B期;并从储层形成的物源、沉积环境、古气候等方面的差异性,探讨了华庆区块长63和马岭区块长81成岩作用差异性的成因。由于长6较长8粒度细、杂基含量较高,其压实作用强,原生粒间孔保存较少,早期绿泥石膜胶结不发育,含铁碳酸盐胶结物及自生伊利石含量高,砂岩储层物性较差。 相似文献
556.
The Chang 7 Member of the Yan-Chang Formation (Yan-Chang #7 Member), which is located in the central south of the Ordos Basin (China), is assessed for its potential as a shale gas resource. The characteristics and spatial variability of mineral components in this continental shale formation play a crucial role in evaluating and characterising the shale reservoirs. We collected 64 shale core samples from 30 representative sampling sites located in the central south of the Ordos Basin using X-ray diffraction and field emission scanning electron microscopy to study the mineral compositions, vertical/planar variations of minerals, and the major controlling factors that result in such variations. Based on the relative fractions of the dominant minerals, the shale rocks can be classified into four categories: quartz-rich (type #1), illite/chlorite-rich (type #2), illite–smectite mixed-layer-rich (type #3) and feldspar-rich (type #4). In general, type #1 is mainly located in the northwest of the study area, type #4 is mainly located in the south of the study area, and types #2 and #3 are sandwiched between types #1 and #4. In the centre of the basin, the illite content increases with burial depth and the conversion from smectite to illite, which is experimentally confirmed in this study, enhances the surface porosity of shale. The major factors influencing the properties and spatial variability of the mineral components include sedimentary environment, provenance and diagenesis. Compared with marine shales in China (e.g. Longmaxi marine shales), the Yan-Chang #7 Member continental shale has a higher clay content, but lower calcite, dolomite and pyrite contents. The brittleness indexes of type #1 shale in Wuqi and its surrounding areas are marginally higher than that of Longmaxi marine shales, which makes the type #1 shale in the Wuqi and its surrounding areas slightly easier to fracture than the Longmaxi marine shales. 相似文献
557.
558.
Detrital zircon records in bauxite deposits of China: Implication for the provenance model and ore deposits classification of bauxite
下载免费PDF全文
![点击此处可从《古地理学报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yu Wen-Chao Du Yuan-Sheng Xiong Guo-Lin Zhou Jin-Tao Pang Da-Wei Deng Xu-Sheng Weng Shen-Fu Li Pei-Gang 《古地理学报》1999,22(5):947-964
Based on 3439 detrital zircon U-Pb datapoints collected from the bauxite deposits of China and 297 detrital zircon U-Pb datapoints from underlying clastic rocks,this study reviews the recent progress in the detrital zircon U-Pb geochronology of bauxite deposits in China. Stability assessment of zircon grains in modern tropical weathering profiles proves the chemical and physical stability during the and intense weathering and bauxitization,which makes zircon become a good provenance indicator. Sedimentary provenance study of bauxite deposits in China indicates that even the bauxite deposit developed on the carbonate rocks,there was still considerable input of the weathering aluminosilicate materials. Previous classifications of bauxite deposit are mainly based on the lithology of basement rock and features of ore body,applications of these classifications will cause ambiguities and uncertainties. For widespread parautochthonous and allochthonous detrital zircon grains within Chinese bauxite deposits,parautochthonous and allochthonous criterion is invalid in classification of Chinese bauxite deposits. Here we suggest that the bauxite study requires a new classification of ore deposit,which should consider the weathering process of bauxite deposits as well as the position of bauxite deposit in the sedimentological framework. Although detrital zircon study provides important constrains for the provenance of bauxite deposits,combination of regional geological background and the geochemical characteristics are still essential for the comprehensive cognition of source materials. 相似文献
559.
560.
深基坑支护设计的弹性抗力有限元法 总被引:1,自引:1,他引:0
采用弹性抗力有限元方法讨论多支撑锚桩的深坑支护设计问题。该方法与传统的静力平衡法相比有其优越性,能够计算出不同开挖阶段的桩顶位移,桩身弯距随深度的变化,模拟开挖过程,最大限度地协调支护结构与土体的变形关系,并能确定出最小的桩身弯距设计值及各层锚杆的锚固力。并以实例运用该方法对青岛某基坑工程的支护进行了设计,取得了满意效果 相似文献