全文获取类型
收费全文 | 37906篇 |
免费 | 974篇 |
国内免费 | 1054篇 |
专业分类
测绘学 | 957篇 |
大气科学 | 2882篇 |
地球物理 | 7802篇 |
地质学 | 14008篇 |
海洋学 | 3375篇 |
天文学 | 8207篇 |
综合类 | 241篇 |
自然地理 | 2462篇 |
出版年
2022年 | 292篇 |
2021年 | 477篇 |
2020年 | 459篇 |
2019年 | 501篇 |
2018年 | 916篇 |
2017年 | 883篇 |
2016年 | 1058篇 |
2015年 | 727篇 |
2014年 | 1065篇 |
2013年 | 1894篇 |
2012年 | 1357篇 |
2011年 | 1806篇 |
2010年 | 1585篇 |
2009年 | 2039篇 |
2008年 | 1719篇 |
2007年 | 1783篇 |
2006年 | 1723篇 |
2005年 | 1231篇 |
2004年 | 1148篇 |
2003年 | 1052篇 |
2002年 | 1015篇 |
2001年 | 858篇 |
2000年 | 829篇 |
1999年 | 681篇 |
1998年 | 722篇 |
1997年 | 699篇 |
1996年 | 574篇 |
1995年 | 568篇 |
1994年 | 486篇 |
1993年 | 426篇 |
1992年 | 422篇 |
1991年 | 392篇 |
1990年 | 465篇 |
1989年 | 378篇 |
1988年 | 361篇 |
1987年 | 445篇 |
1986年 | 349篇 |
1985年 | 433篇 |
1984年 | 535篇 |
1983年 | 460篇 |
1982年 | 463篇 |
1981年 | 410篇 |
1980年 | 430篇 |
1979年 | 367篇 |
1978年 | 348篇 |
1977年 | 344篇 |
1976年 | 310篇 |
1975年 | 298篇 |
1974年 | 318篇 |
1973年 | 344篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
Thomas L. Duvall Jr. 《Solar physics》1982,76(1):137-143
The equatorial photospheric rotation rate has been observed on 14 days in 1978–1980. The resulting rotation rate, = 14.14±0.04°/day, is 2% slower than the rate as observed for long-lived sunspots.Stationed at Kitt Peak National Observatory.Operated by the Association of Universities for Research in Astronomy, Inc. under contract with the National Science Foundation. 相似文献
53.
54.
Lithology and Mineral Resources - The chemical composition and Nd isotope systematics were obtained for mudrocks (mudstones) from sections of the Siberian hypostratotype of the Riphean and Vendian... 相似文献
55.
56.
Astrakhantsev G. P. Minina T. R. Petrova N. A. Poloskov V. N. Rukhovets L. A. 《Water Resources》2003,30(2):209-220
A zoobenthos submodel is included in an ecosystem model. The new model is used to assess the role of zoobenthos in the phosphorus exchange at the water–bed interface, in particular, the phosphorus cycle in the water body ecosystem is described more accurately. The calculated zoobenthos distribution over the bed of a lake can be used in modeling the lake ichthyocenoses. 相似文献
57.
A. P. Geptner Yu. I. Pikovskii L. T. Protasevich T. A. Alekseeva M. E. Ramenskaya 《Lithology and Mineral Resources》2003,38(6):509-521
Relationships of mineralized microbiota with the content of polycyclic aromatic hydrocarbons in hydrothermal systems are considered. It has been established that the mineralized microbiota can serve as an indicator of hydrothermal hydrocarbon flows in present-day and ancient deposits. 相似文献
58.
59.
60.
An experimental study on reduction of U (Ⅵ) by anaerobic bacteria, Shewane//a putrefaciens, is first reported here in China. The experimental conditions were: 35℃ and pH =7.0-7.4, corresponding to a physicochemical environments in which the sandstone-hosted interlayer oxidation-zone type uranium deposit formed in Northwest China's Xinjiang. Bacteria adopted in the present experiment, Shewanella putrefaciens, occur extensively in natural environment. Our study shows that nano-crystal precipitates of uraninite quickly occurred on the surface of the cells within one week. It was found that the pitchblende was characterized by a random arrangement of uraninite nanocrystals (2-4 nm) in it, significantly different from natural pitchblende in which uraninite nanocrystals are arranged in order. Finally, a possible mechanism of uranium biomineralization by microorganisms in the deposits is discussed. Our investigation may supply a technical train of thoughts for bioremediation of nuclear-contaminated water environments and for underground dissolving extraction of the sandstone-hosted uranium ores. 相似文献