全文获取类型
收费全文 | 20356篇 |
免费 | 4130篇 |
国内免费 | 4624篇 |
专业分类
测绘学 | 1024篇 |
大气科学 | 4168篇 |
地球物理 | 5286篇 |
地质学 | 10369篇 |
海洋学 | 2359篇 |
天文学 | 909篇 |
综合类 | 2426篇 |
自然地理 | 2569篇 |
出版年
2024年 | 23篇 |
2023年 | 306篇 |
2022年 | 873篇 |
2021年 | 971篇 |
2020年 | 851篇 |
2019年 | 942篇 |
2018年 | 1172篇 |
2017年 | 1040篇 |
2016年 | 1242篇 |
2015年 | 937篇 |
2014年 | 1217篇 |
2013年 | 1218篇 |
2012年 | 1133篇 |
2011年 | 1201篇 |
2010年 | 1120篇 |
2009年 | 1139篇 |
2008年 | 1010篇 |
2007年 | 981篇 |
2006年 | 773篇 |
2005年 | 826篇 |
2004年 | 577篇 |
2003年 | 612篇 |
2002年 | 606篇 |
2001年 | 569篇 |
2000年 | 666篇 |
1999年 | 1003篇 |
1998年 | 802篇 |
1997年 | 878篇 |
1996年 | 811篇 |
1995年 | 682篇 |
1994年 | 562篇 |
1993年 | 507篇 |
1992年 | 391篇 |
1991年 | 286篇 |
1990年 | 229篇 |
1989年 | 175篇 |
1988年 | 173篇 |
1987年 | 126篇 |
1986年 | 105篇 |
1985年 | 71篇 |
1984年 | 50篇 |
1983年 | 43篇 |
1982年 | 36篇 |
1981年 | 27篇 |
1980年 | 35篇 |
1979年 | 27篇 |
1978年 | 15篇 |
1976年 | 11篇 |
1975年 | 14篇 |
1958年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
991.
992.
With the development and popularization of smartphones and embedded sensors, a non-professional atmospheric measurement method by using smartphones carried by the public has been proposed recently. Without extra dedicated instrument, this method has many advantages, such as low hardware cost, high spatio-temporal resolution, and wide coverage, and it can supplement the professional atmospheric measurement methods, which has broad applications in the meteorological operation, scientific research, public service, and other fields. At present, the research on the non-professional atmospheric measurement in China is limited. In order to make full use of this method, this paper briefly outlined the states of existing smartphones and embedded sensors, highlighted the measurement of precipitation, air temperature, pressure, aerosols, and radiation by smartphones. To promote the development of smartphones for atmospheric measurement, future research should focus on mechanism study, available sources exploration, data quality control, big data processing, joining and matching with operation, research and service, etc. 相似文献
993.
994.
995.
996.
997.
998.
Chao Chen Shuyin Niu Fang Wang Fuxiang Zhang Qinglian Zhang Baojun Ma Aiqun Sun Jianzhen Zhang Yaqi Cao Xiaoqing Zhang 《中国地球化学学报》2018,37(1):80-89
The Shihu gold deposit, located in the middle-south section of the core of the Fuping mantle branch structure, is hosted in the Archean Fuping Group and adjacent to the quartz diorite porphyrite. The gold deposit is the only large gold deposit with reserves of more than 30 tons gold discovered in western Hebei Province so far. In order to constrain the timing of mineralization of this ore deposit, this paper focuses on the isotopic dating of zircon and pyrite. Zircons in gold-bearing quartz veins are magmatic in origin and no hydrothermal zircon has been found in such quartz veins, indicating that zircons were derived from the wall rocks. U–Pb ages of zircons fall mainly in the two domains: 2492 ± 82 and 136 ± 4 Ma, respectively, indicative of the contribution of the Fuping-Group TTG gneiss and Yanshanian igneous rocks, respectively. The Re–Os isotopic compositions of pyrites in the gold-bearing quartz veins yield an isochron age of 127 ± 31 Ma. Combined with other dating results, we suggest that the main metallogenic age of the Shihu gold deposit is 120–127 Ma. 相似文献
999.
1000.
Although the middle section of the Bangong-Nujiang suture zone has been intensively investigated, its tectonic framework and evolution is still controversy. The Pungco ophiolite has a relative complete ophiolitic complex, which is an ideal specimen for studying this tricky problem. LA-ICP-MS U-Pb dating of zircons from the diabasic rock yielded an age of 159.0±2.1 Ma. This age suggests that the Pungco ophiolite was formed in the Late Jurassic, indicating the development of the Late Jurassic ophiolite in the third ophiolitic subzone. The whole-rock major and trace element compositions of diabasic and basaltic rocks exhibit mixed arc and N-MORB geochemical characteristics. Two diabasic samples have (87Sr/86Sr)i values of 0.7055 and 0.7063 and εNd(t) values of 11.28 and 11.84, respectively. The geochemical signatures and formation age of the Pungco ophiolite suggest that this ophiolite was probably produced in an active continental fore-arc setting. It originated from a N-MORB-like depleted mantle source with the involvement of subducted-slab fluids. Considering the regional geological background, the Pungco ophiolite was likely generated during the southward subduction of the Bangong-Nujiang Tethyan oceanic lithosphere beneath the Lhasa terrane, and belongs to a regional archipelagic arc-basin system together with the other Early Jurassic-Early Cretaceous ophiolites from the northern Tibet Lake district. © 2018, Science Press. All right reserved. 相似文献