全文获取类型
收费全文 | 3445篇 |
免费 | 91篇 |
国内免费 | 37篇 |
专业分类
测绘学 | 50篇 |
大气科学 | 296篇 |
地球物理 | 778篇 |
地质学 | 1217篇 |
海洋学 | 326篇 |
天文学 | 507篇 |
综合类 | 10篇 |
自然地理 | 389篇 |
出版年
2021年 | 42篇 |
2020年 | 40篇 |
2019年 | 47篇 |
2018年 | 57篇 |
2017年 | 62篇 |
2016年 | 68篇 |
2015年 | 73篇 |
2014年 | 69篇 |
2013年 | 180篇 |
2012年 | 92篇 |
2011年 | 139篇 |
2010年 | 146篇 |
2009年 | 163篇 |
2008年 | 132篇 |
2007年 | 115篇 |
2006年 | 120篇 |
2005年 | 107篇 |
2004年 | 92篇 |
2003年 | 84篇 |
2002年 | 85篇 |
2001年 | 75篇 |
2000年 | 46篇 |
1999年 | 57篇 |
1998年 | 54篇 |
1997年 | 43篇 |
1996年 | 66篇 |
1995年 | 43篇 |
1994年 | 48篇 |
1993年 | 45篇 |
1992年 | 52篇 |
1991年 | 54篇 |
1990年 | 49篇 |
1989年 | 46篇 |
1988年 | 50篇 |
1987年 | 50篇 |
1986年 | 37篇 |
1985年 | 65篇 |
1984年 | 83篇 |
1983年 | 81篇 |
1982年 | 66篇 |
1981年 | 46篇 |
1980年 | 52篇 |
1979年 | 50篇 |
1978年 | 49篇 |
1977年 | 44篇 |
1976年 | 39篇 |
1975年 | 30篇 |
1974年 | 28篇 |
1973年 | 34篇 |
1972年 | 24篇 |
排序方式: 共有3573条查询结果,搜索用时 31 毫秒
101.
William T. Perkins Nicholas J.G. Pearce John A. Westgate 《Geostandards and Geoanalytical Research》1997,21(2):175-190
This contribution presents a review of the recent developments in laser ablation inductively coupled plasma-mass spectrometry. We describe the important developments which have occurred in the laser systems used, leading to a spatial resolution of around 20 (im, and give an overview of the major instrument developments which have affected the geological applications of laser ablation ICP-MS. We describe the calibration of laser ablation for the analysis of trace elements in two different matrices: volcanic glass shards and sulfide minerals. We show how single glass shards can be analysed using the National Institute of Standards and Technology (NIST) glass certified reference materials for calibration and demonstrate the effect of using single spot analyses compared to rastering of the calibration sample. We show the importance of inter-shard variation and demonstrate that averaged single shard analyses produce data which compare well with bulk analyses. The calibration of the laser system for sulfide mineral analysis is discussed and two different strategies are proposed, one using spiked pressed powder pellets of sulfides and the other metal reference materials. We present conclusions and recommendations for the calibration of laser ablation ICP-MS instruments. 相似文献
102.
The Sakoa Group is the lowermost stratigraphical succession of the Karoo Supergroup and the oldest sedimentary unit in Madagascar, spanning the Late Carboniferous through Early Permian epochs. The Sakoa Group is exposed in the southern Morondava Basin. It is predominantly a siliciclastic sequence comprising seven lithofacies associations: (1) diamictites; (2) conglomeratic sandstones; (3) sandstones; (4) interbedded thin sandstones and mudstones; (5) mudstones; (6) coals; and (7) limestones. These facies represent deposition in the early extensional stages of continental rift development. The sediments were deposited predominantly on alluvial fans, and in braided to meandering stream and overbank environments. Locally lacustrine and coal swamp environments formed in low areas of the basin floor during rift initiation. Subsidence rates remained fairly constant throughout the Early Permian and were accompanied by a gradual reduction in relief of the basin margins and an increased geomorphic maturity of the fluvial systems flowing across the basin floor. Near the end of the Early Permian the southern Morondava Basin was inundated by a marine transgression , which resulted in deposition of the Vohitolia Limestone. Subsequent tectonic uplift and erosion resulted in a regional unconformity between the Sakoa Group and the overlying Sakamena Group. 相似文献
103.
104.
105.
Reinterpretation of the RRISP-77 Iceland shear-wave profiles 总被引:1,自引:0,他引:1
106.
107.
108.
109.
The nonlinear association between ENSO and the Euro-Atlantic winter sea level pressure 总被引:1,自引:0,他引:1
A nonlinear projection of the tropical Pacific sea surface temperature anomalies (SSTA) onto the Northern Hemisphere winter sea level pressure (SLP) anomalies by neural networks (NN) was performed to investigate the nonlinear association between El Niño-Southern Oscillation (ENSO) and the Euro-Atlantic winter climate. While the linear impact of ENSO on the Euro-Atlantic winter SLP is weak, the NN projection reveals statistically significant SLP anomalies over the Euro-Atlantic sector during both extreme cold and warm ENSO episodes, suggesting that the Euro-Atlantic climate mainly responds to ENSO nonlinearly. The nonlinear response, mainly a quadratic response to the SSTA, reveals that regardless of the sign of the SSTA, positive SLP anomalies are found over the North Atlantic, stretching from eastern Canada to Europe (with anomaly center located just northwestward of Portugal), and negative anomalies centered over Scandinavia and Norwegian Sea, consistent with the excitation of the positive North Atlantic Oscillation pattern. 相似文献
110.
Tim Barnett Robert Malone William Pennell Detlet Stammer Bert Semtner Warren Washington 《Climatic change》2004,62(1-3):1-11
The results of an experimental `end to end' assessment of the effects of climate change on water resources in the western United States are described. The assessment focuses on the potential effects of climate change over the first half of the 21st century on the Columbia, Sacramento/San Joaquin, and Colorado river basins. The paper describes the methodology used for the assessment, and it summarizes the principal findings of the study. The strengths and weaknesses of this study are discussed, and suggestions are made for improving future climate change assessments. 相似文献