全文获取类型
收费全文 | 475篇 |
免费 | 26篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 23篇 |
大气科学 | 49篇 |
地球物理 | 102篇 |
地质学 | 165篇 |
海洋学 | 56篇 |
天文学 | 50篇 |
综合类 | 2篇 |
自然地理 | 58篇 |
出版年
2022年 | 5篇 |
2021年 | 9篇 |
2020年 | 16篇 |
2019年 | 8篇 |
2018年 | 15篇 |
2017年 | 19篇 |
2016年 | 18篇 |
2015年 | 15篇 |
2014年 | 17篇 |
2013年 | 24篇 |
2012年 | 21篇 |
2011年 | 20篇 |
2010年 | 22篇 |
2009年 | 17篇 |
2008年 | 25篇 |
2007年 | 10篇 |
2006年 | 21篇 |
2005年 | 22篇 |
2004年 | 16篇 |
2003年 | 12篇 |
2002年 | 16篇 |
2001年 | 13篇 |
2000年 | 7篇 |
1999年 | 9篇 |
1998年 | 11篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1993年 | 9篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1968年 | 2篇 |
1967年 | 3篇 |
1966年 | 2篇 |
1940年 | 2篇 |
排序方式: 共有505条查询结果,搜索用时 171 毫秒
51.
Sophie Raous Thierry Becquer Jérémie Garnier Éder de Souza Martins Guillaume Echevarria Thibault Sterckeman 《Applied Geochemistry》2010
An understanding of the biogeochemical behaviour of metals in mine spoil materials is a prerequisite to rehabilitate Ni mining sites. The objective of this study was to characterize the fate of metals in different Ni ore spoil materials as influenced by hydrological conditions and fertilisation practices. In tropical ultramafic complexes, the different stages of lateritic weathering lead to two types of ores, and therefore, to two spoil types. They are mainly either a clay-rich saprolite, so-called “garnierite”, enriched in phyllosilicates, or a limonitic material, enriched in Fe oxides. Lysimeter columns were designed to monitor leaching waters through both spoil materials. The garnieritic spoil released higher concentrations of Mg (mean = 2.25 mg L−1), Ni (0.39 mg L−1) and Cr (1.19 mg L−1) than the limonitic spoil (Mg = 0.5 mg L−1; Ni = 0.03 mg L−1 and Cr = 0.25 mg L−1). Chromium was mainly in an anionic form in leaching solutions. As exchangeable pools of Cr(VI) in limonite (980 mg kg−1 of KH2PO4-extractable Cr) are considerable its release in water may still occur in the case of a pH increase. In mixed spoil, metal concentrations were almost as low as in the limonitic one. The effect of mineral-N fertilisation was a strong release of cations (Ni, Mg) into the leachate. Phosphate amendment did not affect the soil solution composition under experimental conditions. 相似文献
52.
53.
Sharif B.S. Neasham J. Hinton O.R. Adams A.E. 《Oceanic Engineering, IEEE Journal of》2000,25(1):52-61
A Doppler compensation system is presented which is suitable for high-data-rate acoustic communication between rapidly moving platforms such as autonomous underwater vehicles. The proposed approach provides a generic preprocessor to conventional adaptive receiver structures with only a marginal increase in computational load and hardware cost. The preprocessor employs a novel Doppler estimation technique and efficient sample rate conversion to remove Doppler shift induced by platform velocity and acceleration. Performance predicted by simulation is compared to that of sea trials of a prototype communication system in the North Sea. Successful communication is demonstrated at 16 kbit/s with a transmitting platform moving at up to ±2.6 m/s 相似文献
54.
Hong Kwang Yeo Sharif B.S. Adams A.E. Hinton O.R. 《Oceanic Engineering, IEEE Journal of》2001,26(4):604-611
A multi-element receiver strategy is proposed in this paper for a multi-user shallow-water acoustic network (SWAN). The base station receiver, equipped with prior knowledge of the synchronization and training sequences of all intended users, has the task of demodulating the received signals of each user independent of the presence of other users. The adopted receiver strategy enables robust communications through the challenging underwater environment which is limited by both environmental and system factors. The channel is characterized by inter-symbol interference due to multipath propagation and multiple access interference. In this paper, we propose a number of multi-user detection receiver structures employing adaptive decision feedback equalization and spatial diversity to mitigate the effect of these two types of interference. Computer simulations and experimental sea trials conducted in the North Sea in 1999 were used to test the receiver strategies' performance for a two user near far scenario. Amongst a number of strategies tested, the structure based on recursive successive interference cancellation demonstrated improved performance overall 相似文献
55.
56.
Matthew A.LAZZARA Sophie A.ORENDORF Taylor P.NORTON Jordan G.POWERS David H.BROMWICH Scott CARPENTIER John J.CASSANO Steven R.COLWELL Arthur M.CAYETTE Kirstin WERNER 《大气科学进展》2020,37(5):423-430
1.Overview In July 2018,the Antarctic community came together to meet at the 13th Workshop on Antarctic Meteorology and Climate(WAMC)in Madison,Wisconsin,USA(Fig.1);and in the following year in June 2019,the 14th WAMC was held in Charleston,South Carolina,USA(Fig.2).With a growing history,the WAMC addresses the topics of Antarctic meteorology and climate(Kameda et al.,2008;Colwell et al.,2016;Lazzara et al.,2018)as well as weather-related issues of scientific and operational support.The workshops bring together researchers,operational forecasters,numerical modelers,observational specialists,and students.The themes of both workshops included Antarctic meteorological observations,Antarctic atmospheric numerical modeling,Antarctic meteorological and climate research,and Antarctic weather forecasting and operational services.The 2018 and 2019 WAMC were both followed by a one-day focus on the Year of Polar Prediction-Southern Hemisphere(YOPP-SH),when preparations and follow-up discussions were made with regard to the YOPP Special Observing Period from 16 November 2018 to 15 February 2019. 相似文献
57.
Ian Shennan Sarah Hamilton Caroline Hillier Amanda Hunter Ruth Woodall Sarah Bradley Glenn Milne Anthony Brooks Sophie Bassett 《第四纪科学杂志》2006,21(6):601-613
Observations of relative sea‐level change and local deglaciation in western Scotland provide critical constraints for modelling glacio‐isostatic rebound in northern Britain over the last 18 000 years. The longest records come from Skye, Arisaig and Knapdale with a shorter, Holocene, record from Kintail. Biostratigraphic (diatom, pollen, dinoflagellate, foraminifera and thecamoebian), lithological and radiocarbon analyses provide age and elevation parameters for each sea‐level index point. All four sites reveal relative sea‐level change that is highly non‐monotonic in time as the local vertical component of glacio‐isostatic rebound and eustasy (or global meltwater influx) dominate at different periods. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
58.
Fractal and multifractal techniques have been applied to various types of solar data to study the fractal properties of sunspots as well as the distribution of photospheric magnetic fields and the role of random motions on the solar surface in this distribution. Other research includes the investigation of changes in the fractal dimension as an indicator for solar flares. Here we evaluate the efficacy of two methods for determining the fractal dimension of an image data set: the Differential Box Counting scheme and a new method, the Jaenisch scheme. To determine the sensitivity of the techniques to changes in image complexity, various types of constructed images are analyzed. In addition, we apply this method to solar magnetogram data from Marshall Space Flight Center's vector magnetograph. 相似文献
59.
Ian Shennan Sarah Bradley Glenn Milne Anthony Brooks Sophie Bassett Sarah Hamilton 《第四纪科学杂志》2006,21(6):585-599
While contributing <1 m equivalent eustatic sea‐level rise the British Isles ice sheet produced glacio‐isostatic rebound in northern Britain of similar magnitude to eustatic sea‐level change, or global meltwater influx, over the last 18 000 years. The resulting spatially variable relative sea‐level changes combine with observations from far‐field locations to produce a rigorous test for quantitative models of glacial isostatic adjustment, local ice‐sheet history and global meltwater influx. After a review of the attributes of relative sea‐level observations significant for constraining large‐scale models of the isostatic adjustment process we summarise long records of relative sea‐level change from the British Isles and far‐field locations. We give an overview of different global theoretical models of the isostatic adjustment process before presenting intercomparisons of observed and predicted relative sea levels at sites in the British Isles and far‐field for a range of Earth and ice model parameters in order to demonstrate model sensitivity and the resolving power available from using evidence from the British Isles. For the first time we show a good degree of fit between relative sea‐level observations and predictions that are based upon global Earth and ice model parameters, independently derived from analysis of far‐field data, with a terrain‐corrected model of the British Isles ice sheet that includes extensive glaciation of the North Sea and western continental shelf, that does not assume isostatic equilibrium at the Last Glacial Maximum and keeps to trimline constraints of ice surface elevation. We do not attempt to identify a unique solution for the model lithosphere thickness parameter or the local‐scale detail of the ice model in order to provide a fit for all sites, but argue that the next stage should be to incorporate an ice‐sheet model that is based on quantitative, glaciological model simulations. We hope that this paper will stimulate this debate and help to integrate research in glacial geomorphology, glaciology, sea‐level change, Earth rheology and quantitative modelling. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
60.
Following the recent mass spectrometric observations of the ambient stratospheric positive and negative ions we have carried out co-ordinated laboratory experiments using a selected ion flow tube apparatus and a flowing afterglow apparatus for the following purposes: (i) to consider whether CH3CN is a viable candidate molecule for the species X in the observed stratospheric ion series H+ (H2On (X)m and (ii) to determine the binary mutual neutralization rate coefficients αi for the reactions ofH+ (H2O4 and H+(H2O)(CH3CN)3 with several of the negative ion species observed in the stratosphere. We conclude from (i) that CH3CN is indeed a viable candidate for X and from (ii) that the αi for stratospheric ions are within the limited range (5–6) × 10?8 cm3 s?1. 相似文献