全文获取类型
收费全文 | 7324篇 |
免费 | 79篇 |
国内免费 | 19篇 |
专业分类
测绘学 | 64篇 |
大气科学 | 1165篇 |
地球物理 | 1634篇 |
地质学 | 3772篇 |
海洋学 | 168篇 |
天文学 | 362篇 |
综合类 | 11篇 |
自然地理 | 246篇 |
出版年
2013年 | 173篇 |
2012年 | 69篇 |
2011年 | 104篇 |
2010年 | 92篇 |
2009年 | 114篇 |
2008年 | 108篇 |
2007年 | 83篇 |
2006年 | 101篇 |
2005年 | 94篇 |
2004年 | 90篇 |
2003年 | 84篇 |
2002年 | 88篇 |
1999年 | 68篇 |
1998年 | 78篇 |
1996年 | 96篇 |
1995年 | 66篇 |
1994年 | 68篇 |
1993年 | 86篇 |
1992年 | 166篇 |
1991年 | 170篇 |
1990年 | 162篇 |
1989年 | 161篇 |
1988年 | 148篇 |
1987年 | 185篇 |
1986年 | 147篇 |
1985年 | 134篇 |
1984年 | 176篇 |
1983年 | 190篇 |
1982年 | 199篇 |
1981年 | 207篇 |
1980年 | 173篇 |
1979年 | 201篇 |
1978年 | 165篇 |
1977年 | 159篇 |
1976年 | 127篇 |
1975年 | 146篇 |
1974年 | 137篇 |
1973年 | 147篇 |
1972年 | 133篇 |
1971年 | 140篇 |
1970年 | 150篇 |
1969年 | 104篇 |
1968年 | 131篇 |
1967年 | 126篇 |
1966年 | 87篇 |
1965年 | 96篇 |
1964年 | 101篇 |
1962年 | 91篇 |
1960年 | 105篇 |
1954年 | 67篇 |
排序方式: 共有7422条查询结果,搜索用时 296 毫秒
1.
2.
3.
Takuya Matsumoto Masahiko Honda Ian McDougall Igor Yatsevich Suzanne Y. O'Reilly 《地学学报》2004,16(1):23-26
Using a Rayleigh distillation fractionation model, we calculate that the maximum isotope fractionation potentially achievable is less than 5% during the early stages of gas release from a sample. Our calculation corrects the erroneous conclusions of Gautheron and Moreira (2003), who re‐interpreted the plume‐like neon isotopic compositions found in metasomatic apatite from a south‐eastern Australian xenolith (Matsumoto et al., 1997) to be the result of Rayleigh‐type isotope fractionation of originally MORB‐type neon during stepheating gas extraction. We stress that the modelling of neon isotopic fractionation by Gautheron and Moreira (2003) is incorrect, and that the finding of a plume‐like neon isotopic composition in the apatite by Matsumoto et al. (1997) remains a quite valid and robust conclusion. 相似文献
4.
5.
Gavin L. England Birger Rasmussen Neal J. McNaughton Ian R. Fletcher David I. Groves & Bryan Krapez 《地学学报》2001,13(5):360-367
SHRIMP dating of xenotime overgrowths on detrital zircon grains can constrain maximum durations since diagenesis and therefore provide minimum dates of sediment deposition. Thus, xenotime dating has significant economic application to Precambrian sediment-hosted ore deposits, such as Witwatersrand Au–U, for which there are no precise depositional ages. The growth history of xenotime in the Witwatersrand Supergroup is texturally complex, with several phases evident. The oldest authigenic xenotime 207 Pb/206 Pb age obtained in sandstone underlying the Vaal Reef is 2764 ± 5 Myr (1 σ), and most likely represents a mixture of diagenetic and hydrothermal growth. Nevertheless, this represents the oldest authigenic mineral age yet recorded in the sequence and provides a minimum age of deposition. Other xenotime data record a spread of ages that correspond to numerous post-diagenetic thermotectonic events (including a Ventersdorp event at ≈ 2720 Ma) up to the ≈2020 Ma Vredefort event. 相似文献
6.
7.
8.
Kenai, located on the west coast of the Kenai Peninsula, Alaska, subsided during the great earthquake of AD 1964. Regional land subsidence is recorded within the estuarine stratigraphy as peat overlain by tidal silt and clay. Reconstructions using quantitative diatom transfer functions estimate co‐seismic subsidence (relative sea‐level rise) between 0.28±0.28 m and 0.70±0.28 m followed by rapid post‐seismic recovery. Stratigraphy records an earlier co‐seismic event as a second peat‐silt couplet, dated to ~1500–1400 cal. yr BP with 1.14±0.28 m subsidence. Two decimetre‐scale relative sea‐level rises are more likely the result of glacio‐isostatic responses to late Holocene and Little Ice Age glacier expansions rather than to co‐seismic subsidence during great earthquakes. Comparison with other sites around Cook Inlet, at Girdwood and Ocean View, helps in constructing regional patterns of land‐level change associated with three great earthquakes, AD 1964, ~950–850 cal. yr BP and ~1500–1400 cal. yr BP. Each earthquake has a different spatial pattern of co‐seismic subsidence which indicates that assessment of seismic hazard in southern Alaska requires an understanding of multiple great earthquakes, not only the most recent. All three earthquakes show a pre‐seismic phase of gradual land subsidence that marked the end of relative land uplift caused by inter‐seismic strain accumulation. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
9.
10.
Andrew J. L. Harris Anna L. Butterworth Richard W. Carlton Ian Downey Peter Miller Pedro Navarro David A. Rothery 《Bulletin of Volcanology》1997,59(1):49-64
Satellite data offer a means of supplementing ground-based monitoring during volcanic eruptions, especially at times or locations
where ground-based monitoring is difficult. Being directly and freely available several times a day, data from the advanced
very high resolution radiometer (AVHRR) offers great potential for near real-time monitoring of all volcanoes across large
(3000×3000 km) areas. Herein we describe techniques to detect and locate activity; estimate lava area, thermal flux, effusion
rates and cumulative volume; and distinguish types of activity. Application is demonstrated using data for active lavas at
Krafla, Etna, Fogo, Cerro Negro and Erebus; a pyroclastic flow at Lascar; and open vent systems at Etna and Stromboli. Automated
near real-time analysis of AVHRR data could be achieved at existing, or cheap to install, receiving stations, offering a supplement
to conventional monitoring methods.
Received: 21 January 1997 / Accepted: 3 April 1997 相似文献