全文获取类型
收费全文 | 181篇 |
免费 | 47篇 |
国内免费 | 58篇 |
专业分类
测绘学 | 24篇 |
大气科学 | 29篇 |
地球物理 | 55篇 |
地质学 | 118篇 |
海洋学 | 22篇 |
天文学 | 2篇 |
综合类 | 15篇 |
自然地理 | 21篇 |
出版年
2024年 | 1篇 |
2023年 | 7篇 |
2022年 | 9篇 |
2021年 | 12篇 |
2020年 | 9篇 |
2019年 | 13篇 |
2018年 | 11篇 |
2017年 | 10篇 |
2016年 | 6篇 |
2015年 | 10篇 |
2014年 | 16篇 |
2013年 | 11篇 |
2012年 | 19篇 |
2011年 | 10篇 |
2010年 | 12篇 |
2009年 | 6篇 |
2008年 | 10篇 |
2007年 | 7篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 5篇 |
2003年 | 5篇 |
2002年 | 10篇 |
2001年 | 8篇 |
2000年 | 6篇 |
1999年 | 7篇 |
1998年 | 4篇 |
1997年 | 8篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1958年 | 1篇 |
排序方式: 共有286条查询结果,搜索用时 15 毫秒
81.
四川省剑门关一带晚侏罗世沉积体系与古环境演化 总被引:2,自引:0,他引:2
晚侏罗世是龙门山前陆盆地演化的关键时期, 因而沉积体系与古环境演化研究具有重要意义.运用比较沉积学的方法, 通过对沉积序列与旋回的详细研究, 将研究区晚侏罗世沉积体系分为湖泊沉积体系、三角洲沉积体系、冲积扇沉积体系以及河流沉积体系; 基于沉积背景和演化的分析, 确定龙门山推覆构造带是研究区晚侏罗世古环境演化和沉积体系空间配置的控制因素; 依据古流和物源分析, 确定西北部的龙门山是本区主要物源区 相似文献
82.
83.
84.
85.
Chengyou Feng Zailin Zeng Dequan Zhang Wenjun Qu Andao Du Daxin Li Hongquan She 《Ore Geology Reviews》2011,43(1):8-25
The southern Jiangxi Province is a major part of the Nanling W–Sn metallogenic province of southern China, where all W–Sn ore deposits are temporally and spatially related to Mesozoic granitic intrusions. The Tianmenshan–Hongtaoling orefield is a recently explored territory endowed by several styles of W–Sn mineralization. The orefield comprises three composite granitic plutons: Tianmenshan, Hongtaoling and Zhangtiantang associated with several tens of W–Sn-polymetallic ore deposits (Maoping, Baxiannao, Niuling, Zhangdou, Yaolanzhai and others) along their contacts. In this study, four new SHRIMP zircon U–Pb ages were determined for three composite granitic plutons, and 33 molybdenite samples from five W–Sn deposits were analysed by ICP-MS Re–Os isotopic method. SHRIMP zircon U–Pb ages for both medium to coarse-gained biotite granite and porphyritic biotite monzogranite from the Tianmenshan composite pluton are 157.2 ± 2.2 Ma and 151.8 ± 2.9 Ma, respectively. Molybdenite Re–Os isochron ages for the related Baxiannao fracture-controlled tungsten deposits are 157.9 ± 1.5 Ma. Maoping greisens-type tungsten deposits were emplaced at 155.3 ± 2.8 Ma and the Maoping wolframite–quartz veins at 150.2 ± 2.8 Ma, respectively. The SHRIMP U–Pb age of zircons from the Hongtaoling biotite granite is 151.4 ± 3.1 Ma whereas the molybdenite Re–Os isochron ages of the genetically related Niuling endocontact tungsten quartz veins and Zhangdou exocontact tungsten quartz veins are 154.9 ± 4.1 to 154.6 ± 9.7 Ma and 149.1 ± 7.1 Ma, respectively. The SHRIMP zircon U–Pb age of the Zhangtiantang fine-grained muscovite granite is 156.9 ± 1.7 Ma, whereas the molybdenite Re–Os isochron age for the related Yaolanzhai greisens-type tungsten deposit is 155.8 ± 2.8 Ma. These new age data, combined with those available from the literature, indicate that the ages of W–Sn ores and related granites are Late Jurassic with a peak at 150 to 160 Ma, which corresponds to the widespread Mesozoic metallogenic event in southern China. Molybdenites from this group of tungsten deposits have quite low Re contents (29.1 to 2608 ppb), suggesting continental crustal provenance of the ore metals. 相似文献
86.
在矿床储量计算过程中,矿石体重预测的准确与否将直接影响到资源储储量的可靠程度.对矿石体重的准确预测需要大量运算的统计问题,利用SPSS(Statistical Product and Service Solutions)的Regression模块,对所测定的矿石小体重与其矿石品位进行多元回归分析,快速、准确的构建了矿石体重与品位的数学模型,从而为储量计算提供了科学依据. 相似文献
87.
Spatio-temporal variation and statistical characteristic of extreme dry spell in Yellow River Basin, China 总被引:1,自引:0,他引:1
Dunxian She Jun Xia Jiyun Song Hong Du Junxu Chen Long Wan 《Theoretical and Applied Climatology》2013,112(1-2):201-213
Drought is one of the most detrimental natural hazards in Yellow River Basin (YRB). In this research, spatio-temporal variation and statistical characteristic of drought in YRB is studied by using dry spell. Two extreme series, including annual maximum series (AMS) and partial duration series (PDS), are used and simulated with generalized extreme value (GEV), generalized Pareto (GP), and Pearson type III (PE3) distributions. The results show that the northern part is drier than the southern part of YRB. Besides, the maximum dry spell usually starts in October, November, and December. According to the trend analysis, mean maximum length of dry spell (MxDS) shows a negative trend in most stations. From the L-moments and Kolmogorov–Smirnov test method, it can be found that GEV model can better fit AMS while GP and PE3 can better fit PDS. Moreover, the quantiles from optimal model of AMS and PDS depict a similar distribution with values increases from south to north. The spatial distribution of scale and location parameters of GEV model for AMS shows a south-to-north gradient, while the distribution of shape parameter is a little irregularity. Furthermore, based on the linear correlation analysis, there is an evident linear relation between location and scale parameters with mean and standard variation of MxDS, respectively. 相似文献
88.
89.
研究南海海域盛产的四种褐藻(海带、裙带菜、昆布和亨氏马尾藻)、三种红藻(紫菜、沙菜和江蓠)及来自南海三个不同海区(南沙、惠来和南澳)亨氏马尾藻的总脂质及脂肪酸含量干重,并重点比较其多不饱和脂肪酸的含量.结果表明,供试褐藻类海藻总脂质含量ω在1.81%~6.11%之间,红藻类海藻的总脂质含量ω在1.44%~3.96%之间;紫菜中含有7.548mg/g(干重,下同)的亚油酸(C182);海带含丰富C181,达5.592mg/g;花生四烯酸(C204)在裙带菜中含量为1.606mg/g;在供试藻种中,昆布的EPA(C20.5)和DHA(C226)含量最高,测定值为608μg/g和689μg/g. 相似文献
90.
Cao Kenan Dong Mingtan She Zhenbing Xiao Qian Wang Xinyi Qian Yuqi Li Yiheng Wang Zaicong He Qi Wu Xiang Zong Keqing Hu Zhaochu Xiao Long 《中国科学:地球科学(英文版)》2022,65(9):1704-1714
Science China Earth Sciences - The successful return of lunar soil samples from the northern Oceanus Procellarum by the Chang’E 5 (CE-5) mission has provided unprecedented ground-truth... 相似文献