全文获取类型
收费全文 | 12121篇 |
免费 | 2675篇 |
国内免费 | 6472篇 |
专业分类
测绘学 | 37篇 |
大气科学 | 1篇 |
地球物理 | 285篇 |
地质学 | 19648篇 |
海洋学 | 105篇 |
综合类 | 1050篇 |
自然地理 | 142篇 |
出版年
2024年 | 120篇 |
2023年 | 388篇 |
2022年 | 501篇 |
2021年 | 544篇 |
2020年 | 525篇 |
2019年 | 604篇 |
2018年 | 525篇 |
2017年 | 689篇 |
2016年 | 817篇 |
2015年 | 808篇 |
2014年 | 1098篇 |
2013年 | 882篇 |
2012年 | 1107篇 |
2011年 | 1004篇 |
2010年 | 928篇 |
2009年 | 785篇 |
2008年 | 727篇 |
2007年 | 810篇 |
2006年 | 756篇 |
2005年 | 670篇 |
2004年 | 677篇 |
2003年 | 594篇 |
2002年 | 579篇 |
2001年 | 675篇 |
2000年 | 620篇 |
1999年 | 583篇 |
1998年 | 580篇 |
1997年 | 556篇 |
1996年 | 491篇 |
1995年 | 383篇 |
1994年 | 327篇 |
1993年 | 249篇 |
1992年 | 207篇 |
1991年 | 158篇 |
1990年 | 90篇 |
1989年 | 79篇 |
1988年 | 58篇 |
1987年 | 36篇 |
1986年 | 18篇 |
1985年 | 12篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Hang Li Dahua Li Tangfu Xiao Libin He Zengping Ning Jialong Sun Changsheng Zhu Yan Shuang 《中国地球化学学报》2008,27(1):21-27
The Jinding Pb-Zn deposit in Yunnan Province is the representative of a Cd-enriched area and mining activities lead to the release of Cd into the hypergenic ecosystem, resulting in Cd pollution. The concentrations of Cd vary greatly from one type to another type of rocks in the mining district. In the host rock, Cd concentrations range from 50×10^-6 to 650×10^-6 with an average of 310×10^-6. In primary ores, Cd concentrations range from 14×10^-6 to 2800×10^-6 with an average of 767×10^-6. However, in oxidized ores, Cd concentrations are highest, varying within the range of 110×10^-6 to 8200×10^-6 , averaging 1661×10^-6. It is shown that the oxidized ores are the main carder and environmental source of Cd. Leaching test showed that Pb/Zn ores are easy to oxidize and thereafter release Cd and other harmful elements. These leached elements in the leachate may be precipitated rapidly in the order of Zn〉Pb〉Cd. As for the concentration distribution of Cd in the Bijiang River, it is estimated to be 15.7 μg/L Cd in water, 49.3 mg/L in suspended substances, and 203.7 mg/L in sediments. The average value of Cd in soil from the polluted area is 83.0 mg/kg. Natural weathering of Cd-rich rocks and minerals imposes a potential environmental risk on the aquatic ecosystem of the Bijiang catchment. 相似文献
62.
The Baimazhai nickel deposit, Yunnan Province, China, is located in the southern part of the Sanjiang (Tri-river) alkali-rich intrusive rock belt (Sanjiang ARIR). In this paper was conducted ^40Ar-^39Ar dating of two phlogopites in lamprophyres which are, as dikes, widely distributed in the orefield, and two plateau ages were acquired, i.e., 32.46±0.62 Ma and 32.01±0.60 Ma, respectively (averaging 32.23±0.60 Ma). The ages are obviously younger than those of the ore-hosted complex and mineralization of the Baimazhai nickel deposit. In combination with the characteristics, it is indicated that lamprophyres in the orefield and those in the Sanjiang ARIR are similar in tectonic setting, mineral assemblage and geochemistry. It is considered that lamprophyres in the orefield are the important component of the Sanjiang ARIR, and the lamprophyres and ore-hosted complex in the orefield represent the products of two times of different magmatic activity from different mantle sources. On the other hand, the age of lamprophyres in the orefield is older than that of the strike-slip shearing of the Ailaoshan-Honghe fault belt, suggesting that the strike-slip shearing of the Ailaoshan-Honghe fault belt is not the factor leading to magmatic activity of lamprophyres in the orefield, while it is more possible that magmatic activity of the Sanjiang ARIR promoted strike-slip shearing of the fault belt. 相似文献
63.
Central Fujian Rift is another new and important volcanogenic massive sulfide Pb-Zn polymetallic metallogenetic belt. In order to find out the material genesis and mineralization period of Meixian-type Pb-Zn-Ag deposits, S and Pb isotope analysis and isotope geochronology of ores and wall rocks for five major deposits are discussed. It is concluded that the composition of sulfur isotope from sulfide ore vary slightly in different deposits and the mean value is close to zero with the 834S ranging from -3.5‰ to +5.6‰ averaging at +2.0‰, which indicates that the sulfur might originate from magma or possibly erupted directly from volcano or was leached from ore-hosted volcanic rock. The lead from ores in most deposits displays radioactive genesis character (206pb/204pb〉18.140, 207Pb/204pb〉15.584, 208pb/204pb〉38.569) and lead isotope values of ores are higher than those of wall rocks, which indicates that the lead was likely leached from the ore-hosted volcanic rocks. Based on isotope data, two significant Pb-Zn metallogenesis are delineated, which are Mid- and Late-Proterozoic sedimentary exhalative metailogenesis (The single zircon U-Pb, Sm-Nd isochronal and Ar-Ar dating ages of ore- hosted wall rocks are calculated to be among 933-1788 Ma.) and Yanshanian magmatic hydrothermal superimposed and alternated metallogenesis (intrusive SHRIMP zircon U-Pb and Rb-Sr isochronal ages between 127-154 Ma). 相似文献
64.
湖子地区位于NNE向诸广-新兴铀成矿带与近EW向大东山-漳州大断裂复合部位,是华南早、晚两期铀成矿热液活动叠加区、放射性高场区,既有"硅化带大脉"型铀矿产出,又有"交点"型铀矿存在,找矿前景良好.文章在论述下庄矿田铀成矿地质环境、铀成矿特征及铀矿定位条件基础上,分析了湖子地区铀成矿条件与找矿前景,指出该区今后铀矿找矿方向是:① 6009号硅化断裂带,在其北段找硅化带大脉型铀矿,在其南段找"交点"型铀矿;②新桥-下庄硅化断裂带和6009号带之间成矿部位,寻找硅化带型和"交点"型铀矿;③NW向、近EW向辉绿岩脉与NNE向、NE向构造交汇部位(交点),寻找"交点"型铀矿. 相似文献
65.
大兴安岭白音诺尔铅锌矿控矿构造研究与找矿预测 总被引:4,自引:1,他引:3
成矿物质来源及控矿因素是矿床学研究的前沿课题。过去人们认为成矿物质主要源于含矿围岩的萃取。因此,找矿重点是寻找矿源层。但是,更多的事实表明,成矿物质主要来自深源,通过地幔热柱多级演化迁移至地壳,并在幔枝构造较好的控矿构造空间聚集成矿。本文探讨了大兴安岭中南段的成矿作用,总结了该区的主要控矿构造,指出了不同级别构造对成矿的控制作用,并预测了不同级别的成矿靶区。 相似文献
66.
67.
大金山铅锌矿位于泰宁一政和北东东向铜多金属成矿带上,是该成矿带主要的矿种之一,也是闽北地区一个较有价值的矿床。矿床产于早元古代南山组上段,受燕山期北东东向构造控制,属中低温热液充填交代型矿床。 相似文献
68.
排庭金矿是贵州三都——丹寨锑、汞、金成矿带上,继苗龙锑-金矿、宏发厂汞-金矿后首次发现的产于中下寒武统独立型的微细浸染型金矿,其矿体受断裂构造、地层、岩性等因素控制,矿床规模为中型。对该矿床的地质特征及成因进行总结和分析,对于华南褶皱带与扬子准地台过渡带寻找寒武纪地层中的微细浸染型金矿具有重要的借鉴和指导意义。 相似文献
69.
70.