全文获取类型
收费全文 | 800篇 |
免费 | 63篇 |
专业分类
测绘学 | 27篇 |
大气科学 | 54篇 |
地球物理 | 257篇 |
地质学 | 246篇 |
海洋学 | 59篇 |
天文学 | 182篇 |
综合类 | 2篇 |
自然地理 | 36篇 |
出版年
2023年 | 3篇 |
2022年 | 5篇 |
2021年 | 13篇 |
2020年 | 17篇 |
2019年 | 13篇 |
2018年 | 40篇 |
2017年 | 45篇 |
2016年 | 39篇 |
2015年 | 36篇 |
2014年 | 46篇 |
2013年 | 34篇 |
2012年 | 41篇 |
2011年 | 45篇 |
2010年 | 46篇 |
2009年 | 49篇 |
2008年 | 38篇 |
2007年 | 40篇 |
2006年 | 22篇 |
2005年 | 19篇 |
2004年 | 29篇 |
2003年 | 20篇 |
2002年 | 22篇 |
2001年 | 24篇 |
2000年 | 14篇 |
1999年 | 15篇 |
1998年 | 17篇 |
1997年 | 10篇 |
1996年 | 6篇 |
1995年 | 10篇 |
1994年 | 4篇 |
1993年 | 13篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1989年 | 5篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1971年 | 4篇 |
1969年 | 3篇 |
1968年 | 2篇 |
1955年 | 4篇 |
排序方式: 共有863条查询结果,搜索用时 15 毫秒
721.
722.
The presence of scaling statistical properties in temporal rainfall has been well established in many empirical investigations during the latest decade. These properties have more and more come to be regarded as a fundamental feature of the rainfall process. How to best use the scaling properties for applied modelling remains to be assessed, however, particularly in the case of continuous rainfall time‐series. One therefore is forced to use conventional time‐series modelling, e.g. based on point process theory, which does not explicitly take scaling into account. In light of this, there is a need to investigate the degree to which point‐process models are able to ‘unintentionally’ reproduce the empirical scaling properties. In the present study, four 25‐year series of 20‐min rainfall intensities observed in Arno River basin, Italy, were investigated. A Neyman–Scott rectangular pulses (NSRP) model was fitted to these series, so enabling the generation of synthetic time‐series suitable for investigation. A multifractal scaling behaviour was found to characterize the raw data within a range of time‐scales between approximately 20 min and 1 week. The main features of this behaviour were surprisingly well reproduced in the simulated data, although some differences were observed, particularly at small scales below the typical duration of a rain cell. This suggests the possibility of a combined use of the NSRP model and a scaling approach, in order to extend the NSRP range of applicability for simulation purposes. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
723.
724.
Stephen Serjeant † Alberto Carramiñana † Eduardo Gonzáles-Solares Phillipe Héraudeau Raúl Mújica † Ismael Perez-Fournon Nicola Sedgwick † Michael Rowan-Robinson Alberto Franceschini Thomas Babbedge Carlos del Burgo Paolo Ciliegi reas Efstathiou Fabio La Franca Carlotta Gruppioni David Hughes Carlo Lari Seb Oliver Francesca Pozzi Manfred Stickel Mattia Vaccari 《Monthly notices of the Royal Astronomical Society》2004,355(3):813-818
725.
Piercarlo Bonifacio Elisabetta Caffau Miriam Centurión Paolo Molaro Giovanni Vladilo 《Monthly notices of the Royal Astronomical Society》2001,325(2):767-771
By using UV spectra for the O star HD 93521 taken with the ORFEUS II echelle spectrograph, we determine an 'astrophysical' f value for the S ii λ 94.7-nm line: f =0.00498−0.00138 +0.00172 , error at 1 σ level. This is almost a factor of 30 smaller than the guessed value found in the Kurucz data base ( f =0.1472) , which was until now the only one available for this transition. We use our 'astrophysical' f to investigate the S abundance in two damped Ly α absorption systems (DLAs) observed with the UV–Visual Echelle Spectrograph (UVES) at the European Southern Observatory's 8.2-m Kueyen telescope. In the case of the absorber at z abs =3.02486 towards QSO 0347-3819, we find a sulphur column density which is consistent, within errors, with that determined by Centurión et al. by means of the λ 125.9-nm line, thus providing an external check on the accuracy of our f value. For the damped absorber at z abs =4.4680 towards BR J0307-4945, we determine a high value of the S abundance, which, however, is probably the result of blending with Ly α forest lines. 相似文献
726.
Paolo Padovani 《Astrophysics and Space Science》2007,309(1-4):63-71
The “blazar sequence” posits that the most powerful BL Lacertae objects and flat-spectrum radio quasars should have relatively
small synchrotron peak frequencies, ν
peak, and that the least powerful such objects should have the highest ν
peak values. This would have strong implications for our understanding of jet formation and physics and the possible detection
of powerful, moderately high-redshift TeV blazars. I review the validity of the blazar sequence by using the results of very
recent surveys and compare its detailed predictions against observational data. I find that the blazar sequence in its simplest
form is ruled out. However, powerful flat-spectrum radio quasars appear not to reach the ν
peak typical of BL Lacs. This could indeed be related to some sort of sequence, although it cannot be excluded that it is instead
due to a selection effect.
相似文献
727.
728.
729.
730.
In the framework of the commemorations for the First World War, a research project has been carried on in order to identify, archive and disseminate the places involved by the war along the Italian front. A task of this project foresaw the analysis of the terminological component of toponyms. All the occurrences of place names has been collected, evaluated and organised in order to fulfill the task of associate univocally one place name to a set of geographic coordinates, thus creating a specific geodatabase. Lexical, formal, linguistic and dialectal variants, homonyms, exonyms and even errors, once processed, lead to an unambiguous perspective on the use of toponyms during the war and their subsequent variations over the years. 相似文献