全文获取类型
收费全文 | 5933篇 |
免费 | 592篇 |
国内免费 | 161篇 |
专业分类
测绘学 | 259篇 |
大气科学 | 626篇 |
地球物理 | 2174篇 |
地质学 | 2377篇 |
海洋学 | 340篇 |
天文学 | 435篇 |
综合类 | 190篇 |
自然地理 | 285篇 |
出版年
2023年 | 5篇 |
2022年 | 17篇 |
2021年 | 29篇 |
2020年 | 23篇 |
2019年 | 24篇 |
2018年 | 472篇 |
2017年 | 395篇 |
2016年 | 294篇 |
2015年 | 179篇 |
2014年 | 138篇 |
2013年 | 161篇 |
2012年 | 691篇 |
2011年 | 475篇 |
2010年 | 162篇 |
2009年 | 178篇 |
2008年 | 148篇 |
2007年 | 140篇 |
2006年 | 165篇 |
2005年 | 860篇 |
2004年 | 893篇 |
2003年 | 672篇 |
2002年 | 200篇 |
2001年 | 85篇 |
2000年 | 57篇 |
1999年 | 23篇 |
1998年 | 16篇 |
1997年 | 38篇 |
1996年 | 15篇 |
1995年 | 7篇 |
1994年 | 4篇 |
1992年 | 5篇 |
1991年 | 11篇 |
1990年 | 14篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1983年 | 4篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 8篇 |
1973年 | 4篇 |
1971年 | 3篇 |
1969年 | 5篇 |
1965年 | 3篇 |
1955年 | 2篇 |
1954年 | 2篇 |
1951年 | 2篇 |
1948年 | 2篇 |
排序方式: 共有6686条查询结果,搜索用时 15 毫秒
51.
Anders Moberg Hans Bergström Josefin Ruiz Krigsman Ola Svanered 《Climatic change》2002,53(1-3):171-212
Daily meteorological observations have been made at the old astronomical observatory in Stockholm since 1754. Complete daily mean series of air temperature and sea level pressure are reconstructed from the observational data for 1756–1998. The temperature and pressure series arereconstructed and homogenized with the aid of metadata, statistical tests and comparisons with data from other stations. Comparisons with independently reconstructed daily series for nearby Uppsala (1722–1998) show that the quality of thedaily Stockholm data is good, although the reliability is lower before the mid-19th century. The daily temperature data show that the colder winter mean temperatures of the late 18th to early 19th centuries were connected with a particularly high frequency of very cold winter days. The warmer summers of the same period are more connected with a general shift of the temperature distribution towards higher temperatures than in the late 20th century. 相似文献
52.
Rhenium and osmium isotopes in sulfide minerals from the Bagdad porphyry Cu–Mo deposit have been used to determine timing of mineralization and the source of osmium and, by inference, ore metals. Molybdenite, chalcopyrite and pyrite were analyzed mainly from the quartz monzonite and porphyritic quartz monzonite units, which are characterized by moderate to strong potassic alteration (secondary biotite and K-feldspar). Rhenium concentrations in molybdenite are between 330 and 642 ppm. Four Re–Os analyses of two molybdenite samples from the quartz monzonite and porphyritic quartz monzonite yield a weighted average age of 71.8±0.2 Ma (2s). Analyses of a third sample from a molybdenite vein in Precambrian rocks, outside of the main ore zone, yield a weighted average age of 75.9±0.2 Ma (2s), and provide evidence of two separate mineralization episodes. Chalcopyrite samples contain 6 to 12 ppt Os and 1.7 to 4.1 ppb Re; 187Os/ 188Os initial ratios are between 0.1 and 0.8. Pyrite samples have osmium and rhenium concentrations varying in the range 8–17 ppt and 3.9–6.8 ppb, respectively. Analyses from these pyrite samples yield an eight-point isochron with an age of 77±15 Ma (2s) and an initial 187Os/ 188Os ratio of 2.1±0.8 (MSWD=0.90). The results presented here add to the growing body of work indicating that porphyry-type mineralization is produced by long-term, multiple episodes of magmatism and associated mineralization. The data also support the hypothesis that a significant part of the metals and magmas may have a crustal source, as has been suggested for other copper deposits and districts in Arizona. 相似文献
53.
54.
Gil A. J. Rodríguez-Caderot G. Lacy M. C. Ruiz A. M. Sanz de Galdeano C. Alfaro P. 《Studia Geophysica et Geodaetica》2002,46(3):395-410
The Granada Basin (Central Betic Cordillera), one of the most seismically active areas of the Iberian Peninsula, is currently subjected to NW-SE compression and NE-SW extension. The present day extension is accommodated by normal faults with various orientations but particularly with a NW-SE strike. At the surface, these active NW-SE normal faults are mainly concentrated on the NE part of the Basin. In this part we have selected a 15-km long segment where several active normal faults crop out. Using the marine Tortonian rocks as a reference, we have calculated a minimum extensional rate of 0.15-0.30 mm/year. The observed block rotation, the listric geometry of faults at depth and the distribution of seismicity over the whole Basin, indicate that this rate is a minimum value. In the framework of an interdisciplinary research project a non-permanent GPS-network has been established in the central sector of Betic Cordillera to monitor the crustal deformations. The first two observation campaigns were done in 1999 and 2000. 相似文献
55.
新时期我国区域经济地理学发展问题初探 总被引:4,自引:0,他引:4
我国新时期的区域经济地理学在取得全面发展的同时,在理论体系,研究方法和实践领域等方面还需要进一步的发展,文章根据学习和实践区域经济地理学的体会,初步提出基础理论和应用理论,思维方法和技术方法等方面发展见解,并指出区域创新系统和国际经济技术合作等学科应注意拓展的重要实践领域,最后提出我国区域经济地理学科发展的建议。 相似文献
56.
57.
成都市民消费结构与休闲活动关系研究 总被引:6,自引:0,他引:6
城市居民消费水平,消费结构会影响其休闲消费能力,消费意愿,消费方式,消费态度和休闲时空结构,文章以成都市7个城区歌舞,茶棋牌,电影及城市公园休闲活动调查为基础,探讨了城市居民消费结构及其变化与休闲活动特征的关系。研究结果表明,城市居民消费结构的改变对歌舞,茶棋牌娱乐活动影响最大。 相似文献
58.
59.
区域视觉形象识别系统设计的理论与实践 总被引:6,自引:0,他引:6
目前,全国各地正在兴起区域形象设计与建设的浪潮,但如何把区域形象信息系统地传递出去,这方面的理论研究大大落后于实践。文章就区域形象信息传递的有效工具-区域视觉识别系统设计的主要内容,设计的原则,设计的基本流程等在理论与实践上作了较为详细的探讨,并就区域视觉识别系统设计方案的经济学论证作了一些有益探讨。 相似文献
60.