全文获取类型
| 收费全文 | 804篇 |
| 免费 | 318篇 |
| 国内免费 | 301篇 |
专业分类
| 测绘学 | 113篇 |
| 大气科学 | 115篇 |
| 地球物理 | 281篇 |
| 地质学 | 579篇 |
| 海洋学 | 167篇 |
| 天文学 | 11篇 |
| 综合类 | 96篇 |
| 自然地理 | 61篇 |
出版年
| 2024年 | 6篇 |
| 2023年 | 20篇 |
| 2022年 | 49篇 |
| 2021年 | 61篇 |
| 2020年 | 56篇 |
| 2019年 | 66篇 |
| 2018年 | 72篇 |
| 2017年 | 56篇 |
| 2016年 | 55篇 |
| 2015年 | 62篇 |
| 2014年 | 47篇 |
| 2013年 | 77篇 |
| 2012年 | 72篇 |
| 2011年 | 86篇 |
| 2010年 | 75篇 |
| 2009年 | 66篇 |
| 2008年 | 71篇 |
| 2007年 | 97篇 |
| 2006年 | 68篇 |
| 2005年 | 70篇 |
| 2004年 | 32篇 |
| 2003年 | 29篇 |
| 2002年 | 30篇 |
| 2001年 | 36篇 |
| 2000年 | 26篇 |
| 1999年 | 9篇 |
| 1998年 | 4篇 |
| 1997年 | 1篇 |
| 1996年 | 7篇 |
| 1995年 | 1篇 |
| 1994年 | 3篇 |
| 1993年 | 2篇 |
| 1992年 | 3篇 |
| 1990年 | 3篇 |
| 1989年 | 2篇 |
| 1988年 | 1篇 |
| 1957年 | 1篇 |
| 1954年 | 1篇 |
排序方式： 共有1423条查询结果，搜索用时 15 毫秒
31.
A simulated experimental reduction of U^v1 and the synthesis of uraninite by a sulfate-reducing bacteria,Desulfovibrio desulfuricans DSM 642, are first reported. The simulated physicochemical experimental conditions were:35℃, pH=7.0-7.4, corresponding to the environments of formation of the sandstone-hosted interlayer oxidation-zone type uranium deposits in Xinjiang, NW China. Uraninite was formed on the surface of the host bacteria after a one-week‘s incubation. Therefore, sulfate-reducing bacteria, which existed extensively in Jurassic sandstone-producing environments,might have participated in the biomineralization of this uranium deposit. There is an important difference in the orderdisorder of the crystalline structure between the uraninite produced by Desulfovibrio desulfuricans and naturally occurring uraninite. Long time and slow precipitation and growth of uraninite in the geological environment might have resulted in larger uraninite crystals, with uraninite nanocrystals arranged in order, whereas the experimentally produced uraninite is composed of unordered uraninite nanocrystals which, in contrast, result from the short time span of formation and rapid precipitation and growth of uraninite. The discovery has important implications for understanding genetic significance in mineralogy, and also indicates that in-situ bioremediation of U-contaminated environments and use of biotechnology in the treatment of radioactive liquid waste is being contemplated. 相似文献
32.
辽宁省的鞍山、本溪两市为我国重要的钢铁基地，各矿山长期生产遗留的铁尾矿问题越来越引起人们的重视，如污染环境、诱发地质灾害等，如何解决已成为地质、环保、水工界的关注。 相似文献
33.
34.
利用常规地面观测资料和CALIOP/CALIPSO卫星遥感资料统计分析了中国西北东部霾的多年变化以及霾事件期间气溶胶光学特性的垂直空间分布特征,并以2013年3月和11月发生在西北东部的霾天气为例分析了霾发生时大气气溶胶粒子的形状及大小的垂直分布特征、对应的天气形势和气象要素的变化。结果表明:西北东部霾日出现频率由20世纪80年代至90年代末逐渐减小,但21世纪起又明显增加;霾事件主要发生在11、12和1月。霾发生时,在对流层内霾影响最严重的区域在距地面2~4 km范围,垂直方向气溶胶后向散射系数的范围集中于0.8×10-3~2.5×10-3km-1·sr-1,且随高度增加而增大;气溶胶的体积退偏比大部分20%,气溶胶较为规则,不规则的多分布在地表向上4 km以下,随着高度的增加气溶胶不规则性减弱。色比数值大部分0.8,8~12 km气层中主要是色比为0.0~0.4的粒子。当高空受高压系统控制,地面为均压场,近地面出现逆温层时易产生霾。 相似文献
35.
TTG(Tonalite-Trondhjemite-Granodiorite) gneisses,a major component of Precambrian continental crust,play a significant role in understanding the process and mechanism of the crustal evolution in the early periods of the Earth. In terms of field occurrence,there are two kinds of Archean TTGs in the NCC(North China Craton): intercalated and non-intercalated TTGs. In this contribution,we make a comprehensive comparison of these two types of TTGs from the typical areas(Lushan and Hengshan) in the NCC with an aim to constrain their petrogenesis. The results suggest that they have similar mineral assemblages of Pl + Qtz + Bt ± Amp ± Kfs but different field appearances and geochemical compositions,thus probably reflecting different source materials and tectonic settings. Differences in the contents of characteristic elements,such as Sr,REE and HFSE,suggest that the nonintercalated TTGs in Hengshan were generated at deeper levels than those of intercalated TTGs in Lushan. Constraints from element contents and geochemical modeling results are consistent with derivation from dual sources involving both garnet amphibolite and rutile-bearing eclogite residues for the non-intercalated TTGs in Hengshan,whereas the compositions of intercalated TTGs in Lushan indicate that they were formed by partial melting with amphibolite to garnet-amphibolite residues. Moreover,accumulation of plagioclase is also required in the petrogenesis of intercalated TTGs in Lushan,at least for part of them. In addition,the non-intercalated TTGs in Hengshan display distinctly higher Mg O,Mg#,Cr and Ni values and lower SiO_2 average contents compared to the intercalated TTGs in Lushan. These features suggest that the former magma,at least a part,might have interacted with the mantle wedge during ascent. Considering all the above factors and in combination with the whole-rock Nd and zircon Hf isotopic data,it is suggested that the non-intercalated TTGs in Hengshan were produced by partial melting of subducted slab contaminated by the overlying mantle wedge at deeper levels and high pressures,whereas the intercalated TTGs in Lushan were generated by melting of the thickened lower crust at lower pressures and shallower depths. The tectonic settings of the two types of TTGs shed new light on the growth of the NCC. 相似文献
36.
37.
38.
SHAN Xin YU Xinghe Peter ?CLIFT LI Yalong JIN Lin SU Dongxu DU Yonghui ZHOU Jinsong HAN Xiaoqin 《《地质学报》英文版》2018,92(1):268-285
39.
40.