全文获取类型
收费全文 | 309篇 |
免费 | 2篇 |
国内免费 | 8篇 |
专业分类
教育与普及 | 3篇 |
综合类 | 316篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2021年 | 1篇 |
2020年 | 4篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2017年 | 5篇 |
2016年 | 11篇 |
2015年 | 7篇 |
2014年 | 8篇 |
2013年 | 8篇 |
2012年 | 14篇 |
2011年 | 16篇 |
2010年 | 5篇 |
2009年 | 12篇 |
2008年 | 16篇 |
2007年 | 23篇 |
2006年 | 17篇 |
2005年 | 18篇 |
2004年 | 25篇 |
2003年 | 19篇 |
2002年 | 18篇 |
2001年 | 11篇 |
2000年 | 9篇 |
1999年 | 10篇 |
1998年 | 9篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 8篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 1篇 |
排序方式: 共有319条查询结果,搜索用时 0 毫秒
311.
SHRIMP U-Pb zircon geochronology of granulites at Rimana (Southern Tibet) in the central segment of Himalayan Orogen 总被引:2,自引:0,他引:2
LI Dewei LIAO Qunan YUAN Yanming WAN Yusheng LIU Demin ZHANG Xionghua YI Shunhua CAO Shuzhao & XIE Defan . Faculty of Earth Sciences China University of Geosciences Wuhan China . Institute of Geology Chinese Academy of Geosciences Beijing China Correspondence should be addressed to Li Dewei 《科学通报(英文版)》2003,48(23):2647-2650
TheCenozoicHimalayanorogenisimportantinun-derstandingcontinentaldynamicprocesses.Lowercrustal,high-grademetamorphicrockshaverecentlybeendiscov-eredinNamcheBarwaandParmir,i.e.therespectivere-gionsofeasternandwesternsyntaxisoftheorogen[1—4].Eclogitesthatunderwentgranulite-faciesmetamorphismhaverecentlybeenreportedintheCadaareatotheeastofMountEverestinthecentralsegmentoftheHimalayanorogen[5].WiththehelpofthegeologicalsurveyofDing-gyeCountyandChentangSheets(scale1︰250000),high-pressuremafic… 相似文献
312.
对北黄海钻遇的侏罗系地层的4个变质火成岩样品进行锆石U-Pb定年分析,主要获得了2类年龄记录,一类是前寒武纪变质基底形成演化的年龄,另一类是印支期碰撞造山改造的年龄记录.变质基底的年龄区间分布在1.0Ga至2.6Ga,其中1.4Ga至1.8Ga是一个主要构造岩浆期,包括(1 792±140)Ma,(1 447±110)Ma和(1 524±68)Ma三组U-Pb谐和年龄.与华北和扬子印支期碰撞造山作用有关的定年结果为200Ma至240Ma.这2类年龄与邻区胶北地体及苏鲁造山带获得的年龄数据具有很好可比性,可为进一步认识北黄海侏罗系物源区构造演变特点提供重要依据. 相似文献
313.
ZhaoQian Liu LianFu Mei HuaNing Qiu ChuanBo Shen JiGuang Tang JianBing Yun 《科学通报(英文版)》2011,56(26):2803-2812
The exact determination of isotopic ages of hydrocarbon accumulation,reconstruction and destruction periods using traditional isotopic dating methods is complex because of the small numbers of minerals that correlate with hydrocarbons.The quantitative and direct study of hydrocarbon geochronology is therefore an important scientific problem for isotope geochronology and petroleum geology.This study obtains two isotopic ages from a quartz vein sample associated with bitumen in a reverse fault located in the ... 相似文献
314.
315.
Hu Dongsheng Hu Rong Li Xiaoyu Hu Wenxuan Wang Xulong Tian Xingong Liu Weiguo Zhang Guowei 《中国工程科学》2013,11(6):48-57
Through the scientific investigation on Lushan for a long time, detailed studies have been carried out on the geologic stratum section of Late Quaternary in Dajiaochang. The series age data of complete stratigraphic section and full time formation since 400 kaBP were based on the results of the analyses using the dating methods with various instruments such as the ancient geomagnetism, electronics spin resonance (ESR), 36C1 and lumines- cence dating, etc. Corresponding to these data, it identified the paleomagnetic polarity events including Biwa- III event (320 kaBP), Biwa- 1I event (260 kaBP), Biwa- I event (180 kaBP, scarcity due to the disturbance of the iron dish), Blake event (100 kaBP) and Laschamp event (20 kaBP, didn't grow due to the activities of the surface), etc. Combined with the sequence stratigraphy, layer type characteristics and its sediment environment, the strati- graphic can be divided into 4 stages of development respectively : Stage [ is the climate period of glacial epoch (200-400 kaBP); stage 11 is the climate period of interglacial epoch (100-200 kaBP); stage llI is the climate peri- od of periglacial epoch (10-100 kaBP); stage IV is the climate period ofpostglacial epoch (0-10 kaBP). 相似文献
316.
Mesoproterozoic age for Xiamaling Formation in North China Plate indicated by zircon SHRIMP dating 总被引:21,自引:0,他引:21
LinZhi Gao ChuanHeng Zhang XiaoYing Shi Biao Song ZiQiang Wang YaoMing Liu 《科学通报(英文版)》2008,53(17):2665-2671
Zircon grains of magmatic origin from tuffite layers in the Xiamaling Formation at Zhaojiashan Village, Xuanhua area, Hebei Province, were used for zircon dating with a Sensitive High-Resolution Ion Microprobe (SHRIMP Ⅱ), which gives a weighted mean ^207Pb/^206Pb age of 1366±9 Ma. It shows a very similar age (1368±12 Ma) as the zircon dating from the Xiamaling Formation in Western Hill, Beijing. This age proposes that the Xiamaling Formation in the North China plate should be of Mesoproterozoic, instead of Neoproterozoic based on K-Ar, Ar-Ar dating. The new zircon age also indicates the development of macrofossils algae from the Mesoproterozoic age. 相似文献
317.
LA-ICP-MS zircon U-Pb dating and geochemical data for the Late Paleozoic volcanic rocks from eastern and southeastern margins of the Jiamusi Massif are presented to understand the regional tectonic evolution. Zircons from eight representative volcanic rocks are euhedral-subhedral in shape and display striped absorption and fine-scale oscillatory growth zoning as well as high Th/U ratios (0.33-2.37), implying a magmatic origin. The dating results show that the Late Paleozoic volcanic rocks in the study area can be divided into two stages, i.e., the Early Permian (a weighted mean 205^Pb/238^U age of 288 Ma) and the Middle Permian volcanisms (a weighted mean 205^Pb/238^U age of 268 Ma). The former is composed mainly of basalt, basaltic-andesite, andesite and minor dacite. They are characterized by low SiO2 contents, high Mg^# (0.40-0.59), enrichment in Na (Na2O/K2O = 1.26-4.25) and light rare earth elements (LREEs), relative depletion in heavy rare earth elements (HREEs) and high field strength elements (HFSEs), indicating that an active continental margin setting could exist in the eastern margin of the Jiamusi Massif in the Early Permian. The latter consists mainly of rhyolite and minor dacite with high SiO2 (77.23%-77.52%), low MgO (0.11%-0.14%), enrichment in 1(20 (Na2O/K2O ratios 〈 0.80) and Rb, Th, U and depletion in Eu, Sr, P and Ti, implying a crust-derived origin. Therefore, it is proposed that the Middle Permian volcanic rocks could have formed under the collision of the Jiamusi and the Khanka Massifs. 相似文献
318.
Timing of the Wudangshan, Yaolinghe volcanic sequences and mafic sills in South Qinling: U-Pb zircon geochronology and tectonic implication 总被引:10,自引:0,他引:10
WenLi Ling BangFang Ren RuiChun Duan XiaoMing Liu XinWu Mao LianHong Peng ZaoXue Liu JianPing Cheng HongMei Yang 《科学通报(英文版)》2008,53(14):2192-2199
The Wudangshan, Yaolinghe volcanic-sedimentary sequences and doleritic-gabbroic sills comprise the largest exposed Precambrian basement in South Qinling. Zircons separated from 5 volcanic-pyroclastic samples of the Wudangshan Group, 2 volcanic samples of the Yaolinghe Group and one sample for the mafic sills were used for U-Pb dating by laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS). The results reveal that the Wudangshan volcanic sequence was formed at (755±3) Ma (a weighted mean from the 5 samples, MSWD=0.47), whereas the Yaolinghe volcanic suite and the mafic sill were crystallized at (685±5) (2 samples, MSWD=0.36) and (679±3) Ma (MSWD=1.6), respectively, which are equal to each other within analysis errors. These ages are markedly younger than those previously documented for the rocks. The newly obtained ages for the Wudangshan and Yaolinghe Groups are Identical to those of the bottom Liantuo and slightly older than those of the Nantuo Formations, respectively, lower strata of the Nanhua (middle to late Neoproterozoic) stratotype section in eastern Three Gorges, Yangtze creton. A range of inherited magmatic zircons was recognized with ages of 830 to 780 Ma, which are typical of Neoprotzrozoic magmatisms recorded along the margins and interior of the Yangtze craton. Thus, there is Neoproterozoic basement comprising 830-780 Ma igneous suites in South Qinling; the inherited zircons were detrital sediments derived from the northern margin of the Yangtze craton. Accordingly, it is suggested that the South Qinling is a segment of the Yangtze creton before the Qinling Orogeny. 相似文献
319.
《科学通报(英文版)》2008,(24)
It is difficult to date pyroclastic rocks,for almost all the dating methods,due to the multiple sources during their formation.40Ar/39Ar incremental heating results on groundmass selected from the samples show that the age spectra are meaningless geologically.However,singe crystal total fusions of CO2 lasing on the sanidine separates could yield rational 40Ar/39Ar results and distinguish their sources in this study.Timing on three formations of the Moshishan Group,after avoiding the exotic and altered grains by lasing on the single sanidine separate,was reported in this paper.The lowermost portion of the Chawan Formation gives an age of 113.7±0.3 Ma;the lower part of the Xishantou Formation was formed 116.4±0.4 Ma ago and the bottom of the Gaowu Formation took its shape at 118.4±0.4 Ma.These new ages are much younger than the previous ones,suggesting that these thick volcanic formations had been formed in very short durations. 相似文献