全文获取类型
收费全文 | 39674篇 |
免费 | 19319篇 |
国内免费 | 43699篇 |
专业分类
测绘学 | 3147篇 |
大气科学 | 22378篇 |
地球物理 | 13828篇 |
地质学 | 37427篇 |
海洋学 | 16427篇 |
天文学 | 1250篇 |
综合类 | 5150篇 |
自然地理 | 3085篇 |
出版年
2024年 | 170篇 |
2023年 | 407篇 |
2022年 | 820篇 |
2021年 | 1166篇 |
2020年 | 2232篇 |
2019年 | 5598篇 |
2018年 | 5983篇 |
2017年 | 5594篇 |
2016年 | 5747篇 |
2015年 | 5056篇 |
2014年 | 4587篇 |
2013年 | 5136篇 |
2012年 | 4770篇 |
2011年 | 4594篇 |
2010年 | 4564篇 |
2009年 | 3892篇 |
2008年 | 3162篇 |
2007年 | 3196篇 |
2006年 | 2737篇 |
2005年 | 2620篇 |
2004年 | 2917篇 |
2003年 | 2615篇 |
2002年 | 2354篇 |
2001年 | 2158篇 |
2000年 | 1808篇 |
1999年 | 1979篇 |
1998年 | 2061篇 |
1997年 | 2066篇 |
1996年 | 1672篇 |
1995年 | 1557篇 |
1994年 | 1412篇 |
1993年 | 1330篇 |
1992年 | 1130篇 |
1991年 | 856篇 |
1990年 | 801篇 |
1989年 | 674篇 |
1988年 | 578篇 |
1987年 | 440篇 |
1986年 | 370篇 |
1985年 | 277篇 |
1984年 | 292篇 |
1983年 | 177篇 |
1982年 | 214篇 |
1981年 | 155篇 |
1980年 | 116篇 |
1979年 | 111篇 |
1978年 | 47篇 |
1977年 | 43篇 |
1971年 | 53篇 |
1970年 | 44篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
The characteristics and sources of natural gases from Ordovician weathered crust reservoirs in the Central Gas Field in the Ordos Basin 总被引:2,自引:2,他引:0
Xianqing Li Guoyi Hu Jian Li Dujie Hou Peng Dong Zhihong Song Yunfeng Yang 《中国地球化学学报》2008,27(2):109-120
The Central Gas Field is a famous large-sized gas field in the Ordos Basin of China. However, identification of main gas sources of the Ordovician reservoirs in this gas field remains puzzling. On the basis of a lot of geochemical data and geological research on natural gases, the characteristics and sources of natural gases from Ordovician weathered crust reservoirs in the Central Gas Field in the Ordos Basin were studied. The results indicated that natural gases from Ordovician weathered crust reservoirs in the Central Gas Field in the Ordos Basin have similar chemical and isotopic compositions to highly mature and over-mature dry gases. Both coal-derived gases and oil-type gases coexist in the Central Gas Field in the Ordos Basin. The former was derived mainly from Carboniferous-Permian coal measures and the latter from Lower Paleozoic marine carbonates. It is suggested that coal-derived gases occur in the eastern part of the Central Gas Field while oil-type gases may be produced mainly in the northern, western and southern parts of the Central Gas Field in the Ordos Basin. 相似文献
942.
943.
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
944.
Three-dimensional modelling from single images remains an interesting topic of investigation in the research community, even though range sensors are becoming a common alternative for the generation of 3D information. The interest in single-image-based modelling is motivated by a wide spectrum of applications such as cultural heritage, civil engineering, urban planning and even criminology. In this paper a complete new production flowline is presented for modelling based on a single image. The modelling process consists of a series of familiar steps in photogrammetry and computer vision: feature extraction, vanishing point computation, camera self-calibration, 3D reconstruction and dimensional analysis. In particular, the methodology developed for single-image-based modelling takes a scientific approach combining several proven techniques with robust estimators. Finally, in order to demonstrate its capabilities, the reported examples include several real situations applied in different contexts. 相似文献
945.
946.
947.
948.
949.
950.