全文获取类型
收费全文 | 521篇 |
免费 | 105篇 |
国内免费 | 174篇 |
专业分类
测绘学 | 68篇 |
大气科学 | 137篇 |
地球物理 | 99篇 |
地质学 | 269篇 |
海洋学 | 63篇 |
天文学 | 16篇 |
综合类 | 87篇 |
自然地理 | 61篇 |
出版年
2024年 | 2篇 |
2023年 | 18篇 |
2022年 | 37篇 |
2021年 | 36篇 |
2020年 | 30篇 |
2019年 | 37篇 |
2018年 | 44篇 |
2017年 | 39篇 |
2016年 | 32篇 |
2015年 | 38篇 |
2014年 | 34篇 |
2013年 | 35篇 |
2012年 | 25篇 |
2011年 | 27篇 |
2010年 | 37篇 |
2009年 | 33篇 |
2008年 | 26篇 |
2007年 | 23篇 |
2006年 | 23篇 |
2005年 | 17篇 |
2004年 | 22篇 |
2003年 | 19篇 |
2002年 | 12篇 |
2001年 | 15篇 |
2000年 | 12篇 |
1999年 | 18篇 |
1998年 | 24篇 |
1997年 | 17篇 |
1996年 | 13篇 |
1995年 | 11篇 |
1994年 | 12篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1958年 | 1篇 |
排序方式: 共有800条查询结果,搜索用时 0 毫秒
61.
个旧锡矿高松矿田综合信息矿产预测 总被引:13,自引:1,他引:13
个旧超大型锡铜多金属矿床是我国和世界上重要的锡产地,近年来面临严重的资源危机。通过分析个旧锡矿高松矿田的地质、地球化学、地球物理等信息特征,用统计排序法和地质统计学方法解决了断裂、褶皱、地层、花岗岩等定性信息的量化、分级,用分维确定了考虑线性和面状因素的最佳信息单元大小,利用以Shannon信息论基本原理为基础的分层次自相似信息量加和法在信息类型内部和类型之间进行了信息的有机综合,得到了三级18个预测区,经云南锡业公司工程和已知矿区验证,取得了很好的效果。 相似文献
62.
本文用矿石显微镜及单晶X射线分析方法,研究了攀枝花—西昌地区铁钛氧化物矿物的显微结构共生组合特点、各出溶相间的关系和分布方位以及不同岩石和矿石显微结构共生组合上的差异。业已查明它们受岩浆旋回和岩石类型所控制。本文指出了磁铁矿-钛铁晶石固溶体显微出溶结构可能是拐点分解经调制结构后的终期产物。 相似文献
63.
Jesper Raakjær Dao Manh Son Karl-Johan Stæhr Holger Hovgård Nguyen Thi Dieu Thuy Kristine Ellegaard Frank Riget Dang Van Thi Phung Giang Hai 《Marine Policy》2007
Vietnam is in the process of introducing adaptive management based on indicators and time-series to manage its marine fisheries. The development of indicator-based frameworks for fisheries management has accelerated in recent years. This article describes the suite of indicators being suggested or used in Vietnam including the data-collection system. The Vietnamese approach is supported by an institutional structure consisting of a multi-disciplinary advisory system to facilitate the process of using indicators and to introduce knowledge-based management. The article concludes by identifying current problems and weaknesses and by providing suggestions for future improvement of the system. 相似文献
64.
At 21:45 hr (Beijing time) on Oct. 31, 1990 the Yanzhuang meteorite hit the ground at the Yanzhuang village, Wenyuan County,
Guangdong Province. Several fragments, totalling 3.5 kg, were recovered during the field survey. This meteorite is a rare
one of its kind due to its heavily shocked features and thick veins made up of black molten materials.
Olivine and low-calcium pyroxene are compositionally homogeneous with Fa=18.59, Fs=16.35 and Wo=1.29. The chemical composition
(total Fe=28.0%) and recrystallized texture of the chondritic mass show that the Yanzhuang is an H6 chondrite. The black molten
materials occur in the form of blocks (up to 2×3×4 cm in size) and veins (0.1–15 mm in width), and contain a lot of rounded
and elliptic FeNi-FeS blobs (up to 6–10 mm in length). The metal in these blobs exhibits distinct dendritic structure characteristic
of rapid cooling. Unmolten and molten samples are very similar in chemical composition, fitting well with the average H-chondrites.
Partial melting and FeNi/FeS-silicate separation have not been observed in the molten materials of the Yanzhuang.
This project was financially supported by the Science Foundation of Guangdong Province. 相似文献
65.
1 德国地震监测系统德国的地震监测工作由德国联邦地学与自然资源研究院(BGR)负责,具体工作由格拉芬堡地震台阵(GRF)、德国区域地震台网(GRSN)、格拉芬堡地震观测中心(SZGRF)和试验地震观测台阵(GERESS)完成。图1 格拉芬堡地震台阵和德国区域地震台网台站分布格拉芬堡地... 相似文献
66.
Wang Zhaohui Lei Mingdan Ji Shuanghui Xie Changliang Chen Jiazhuo Li Weiguo Jiang Tao 《中国海洋湖沼学报》2022,40(6):2322-2342
Journal of Oceanology and Limnology - Surface sediment samples were collected in three different functional sea areas in Qingdao coast, East China, including the inner Jiaozhou Bay, the Laoshan... 相似文献
67.
Giuliani S Piazza R Bellucci LG Cu NH Vecchiato M Romano S Mugnai C Nhon DH Frignani M 《Marine pollution bulletin》2011,62(5):1013-1024
PCBs were analysed in surficial sediments and selected sediment cores collected between 2002 and 2008 in Central Vietnam coastal lagoons. The aim was to determine contamination levels and trends, and to evaluate the effects of anthropogenic pressures and natural events. Samples were mostly fine-grained with low total PCB concentrations (0.367-44.7 μg kg−1). Atmospheric transport and post depositional processes modify to some degree the fingerprint of PCB inputs to the environment favouring the predominance of 3, 4 and 5 chlorinated congeners. The similarity of congener distributions in contemporary surficial samples also suggests the presence of a unique source over the entire study area, probably connected to mobilisation and long range transports from land-based stocks. The removal of consistent sediment layers is hypothesised based on repeated samplings of the same area. Natural meteorological events (such as typhoons) are suspected to be responsible for these sediment losses. 相似文献
69.
The change in community diversity and structure of the indigenous, dominant, polycyclic aromatic hydrocarbon (PAH)-degrading bacterial genera, Sphingomonas and Mycobacterium, due to contamination in the environment is not very well known. A combination of PCR-DGGE with specific primers and a cultivation-dependent microbiological method was used to detect different populations of Sphingomonas and Mycobacterium in mangrove sediments. The structure of the entire bacterial community (including Sphingomonas) did not show a shift due to environmental contamination, whereas the diversity of Mycobacterium populations in mangrove sediments with higher PAH contamination increased from exposure between Day 0 and Day 30. The isolated Mycobacterium strains migrated to the same position as the major bands of the bacterial communities in Mycobacterium-specific DGGE. A dioxygenase gene system, nidA, which is commonly found in PAH-degrading Mycobacterium strains, was also detected in the more highly contaminated sediment slurries. The present study revealed that Mycobacterium species were the dominant PAH-degraders and played an important role in degrading PAHs in contaminated mangrove sediments. 相似文献
70.
?????????????????????GPS ??????????????Ч???????????????GPS?????????????в???С???????????????????????????Ч????????????????????????????? 相似文献