全文获取类型
收费全文 | 957篇 |
免费 | 31篇 |
国内免费 | 8篇 |
专业分类
测绘学 | 27篇 |
大气科学 | 106篇 |
地球物理 | 206篇 |
地质学 | 302篇 |
海洋学 | 98篇 |
天文学 | 157篇 |
综合类 | 5篇 |
自然地理 | 95篇 |
出版年
2021年 | 15篇 |
2020年 | 16篇 |
2019年 | 14篇 |
2018年 | 22篇 |
2017年 | 20篇 |
2016年 | 33篇 |
2015年 | 22篇 |
2014年 | 24篇 |
2013年 | 62篇 |
2012年 | 23篇 |
2011年 | 40篇 |
2010年 | 36篇 |
2009年 | 44篇 |
2008年 | 35篇 |
2007年 | 32篇 |
2006年 | 23篇 |
2005年 | 40篇 |
2004年 | 36篇 |
2003年 | 31篇 |
2002年 | 27篇 |
2001年 | 25篇 |
2000年 | 35篇 |
1999年 | 25篇 |
1998年 | 21篇 |
1997年 | 12篇 |
1996年 | 10篇 |
1995年 | 10篇 |
1994年 | 15篇 |
1993年 | 19篇 |
1992年 | 12篇 |
1991年 | 10篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 10篇 |
1986年 | 14篇 |
1985年 | 14篇 |
1984年 | 13篇 |
1983年 | 17篇 |
1982年 | 16篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1978年 | 13篇 |
1977年 | 12篇 |
1976年 | 9篇 |
1975年 | 9篇 |
1973年 | 4篇 |
1971年 | 7篇 |
1970年 | 5篇 |
排序方式: 共有996条查询结果,搜索用时 328 毫秒
991.
Martin R. Bates C. Richard Bates Philip L. Gibbard Richard I. Macphail Frederick J. Owen Simon A. Parfitt Richard C. Preece Mark B. Roberts J. Eric Robinson John E. Whittaker Keith N. Wilkinson 《第四纪科学杂志》2000,15(1):61-89
The coastal plain of West Sussex, southern England, is internationally important because of the sequence of discrete high‐sea‐level events preserved at various elevations across it. New evidence is presented from a site at Norton Farm, near Chichester, on the Lower Coastal Plain, where Pleistocene marine sands, fining upwards into silts, occur between 5.3 m and 9.1 m OD. The sequence reflects a regressive tendency at the transition from an interglacial to a cold stage. The marine sands have yielded foraminifera, ostracods and molluscs that indicate a declining marine influence through the sequence, culminating in a tidal mudflat, strongly weathered in places. Cool‐climate foraminifera (including Elphidium clavatum, Cassidulina reniformis and Elphidium albiumbilicatum) and ostracods have been recovered from the marine sands. Some species with an apparent preference for warmer water conditions, however, are also present. Freshwater taxa washed into the terminal marine sediments include some cold climate indicators, such as Pisidium stewarti and P. obtusale lapponicum. Additional evidence for cool climatic conditions during the deposition of the upper part of the marine sequence is provided by the lack of tree taxa in the pollen record and by features of the micromorphology. The marine sediments probably began accumulating during OIS 7, a conclusion based on their elevation, on amino acid ratios from shells, but especially on vertebrate evidence, particularly the presence of a small form of horse, together with a large, distinctive, form of northern vole (Microtus oeconomus). The occurrence of cool climate indicators in these marine sediments may demonstrate a lag between the climatic deterioration and the expected glacio‐eustatic fall in relative sea‐level. This evidence appears to support the conclusions drawn from the study of coral terraces in Barbados. Such a scenario would provide the conditions necessary for the emplacement of the large erratic boulders reported from the Lower Coastal Plain of West Sussex. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
992.
Valois Pierre Bouchard David Talbot Denis Caron Maxime Renaud Jean-Sébastien Gosselin Pierre Jacob Johann 《Natural Hazards》2020,102(3):1155-1173
Natural Hazards - The increase in the frequency of floods, which is a projected consequence of climate change, can have wide-ranging health and economic impacts. To cope with these floods and to... 相似文献
993.
Metop-GRAS in-orbit instrument performance 总被引:2,自引:1,他引:1
The GRAS instrument on the Metop-A satellite provides more than 600 radio occultation measurement profiles per day. The instrument
is characterized by its wide antenna coverage, high signal-to-noise ratio and an ultra-stable clock reference. The conventional
dual-frequency tracking of GPS signals is under dynamic atmosphere conditions complemented by open loop tracking with sampling
of the signal at a 1 kHz rate, providing an unprecedented view of the signal spectral environment. This paper presents the
instrument performance as derived from analysis of in-orbit measurement data. We show that the noise figure is low enough
to enable mapping of external radio noise variations over the earth’s surface. An error propagation model is presented to
relate instrument characteristics to bending angle performance. This model is also used to illustrate the relation between
filter bandwidth, resolution and measurement noise. The Doppler model, guiding open loop measurements, is found to be accurate
to better than 20 Hz with a possibility for improvement to 10 Hz. The high performance at low altitudes enables the presence
of surface reflections at the −20-dB level to be identified in more than 50% of the occultations. The potential performance
improvements for next generation receivers are discussed. 相似文献
994.
C. P. Green G. R. Coope R. L. Jones D. H. Keen D. Q. Bowen A. P. Currant D. T. Holyoak M. Ivanovich J. E. Robinson R. J. Rogerson R. C. Young 《第四纪科学杂志》1996,11(1):59-87
At Stoke Goldington in the valley of the Great Ouse in Buckinghamshire a river terrace at a height of about 7 m above the floodplain is underlain by fluvial sediments representing climatic fluctuations in the late Middle Pleistocene. Near the base of the succession, at a level only 1 m above the modern floodplain, a fossil assemblage, including pollen, plant macrofossils, molluscs, insects and ostracods, provides evidence for the local development of herb-rich grassland under temperate climatic conditions. The fossil record, amino-acid racemisation ratios and uranium disequilibrium dating all suggest deposition of this material during Oxygen Isotope Stage 7. The deposits containing the temperate assemblage are immediately overlain by typical cold-climate gravels of the Great Ouse. These have been subjected to a later cut-and-fill episode, with the fill accumulating in cool climatic conditions. The cut-and-fill episode was succeeded by aggradation, forming the overlying terrace surface. Amino-acid racemisation ratios indicate that the fill was emplaced, and the terrace surface created, during or after Oxygen Isotope Stage 5. © 1996 John Wiley & Sons, Ltd. 相似文献
995.
Jacob Mulder Graham Hagen-Peter Teresa Ubide Rasmus Andreasen Ellen Kooijman Melanie Kielman-Schmitt Yue-Xing Feng Bence Paul Andreas Karlsson Christian Tegner Charles Lesher Fidel Costa 《Geostandards and Geoanalytical Research》2023,47(2):311-336
Laser ablation multi-collector mass spectrometry (LA-MC-ICP-MS) has emerged as the technique of choice for in situ measurements of Sr isotopes in geological minerals. However, the method poses analytical challenges and there is no widely adopted standardised approach to collecting these data or correcting the numerous potential isobaric inferences. Here, we outline practical analytical procedures and data reduction strategies to help establish a consistent framework for collecting and correcting Sr isotope measurements in geological materials by LA-MC-ICP-MS. We characterise a new set of plagioclase reference materials, which are available for distribution to the community, and present a new data reduction scheme for the Iolite software package to correct isobaric interferences for different materials and analytical conditions. Our tests show that a combination of Kr-baseline subtraction, Rb-peak-stripping using βRb derived from a bracketing glass reference material, and a CaCa or CaAr correction for plagioclase and CaCa or CaAr + REE2+ correction for rock glasses, yields the most accurate and precise 87Sr/86Sr measurements for these materials. Using the analytical and correction procedures outlined herein, spot analyses using a beam diameter of 100 μm or rastering with a 50–65 μm diameter beam can readily achieve < 100 ppm 2SE repeatability ("internal") precision for 87Sr/86Sr measurements for materials with < 1000 μg g-1 Sr. 相似文献
996.