全文获取类型
收费全文 | 1066篇 |
免费 | 27篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 32篇 |
大气科学 | 78篇 |
地球物理 | 196篇 |
地质学 | 302篇 |
海洋学 | 120篇 |
天文学 | 279篇 |
自然地理 | 87篇 |
出版年
2022年 | 5篇 |
2021年 | 10篇 |
2020年 | 11篇 |
2019年 | 14篇 |
2018年 | 9篇 |
2017年 | 15篇 |
2016年 | 24篇 |
2015年 | 20篇 |
2014年 | 26篇 |
2013年 | 54篇 |
2012年 | 24篇 |
2011年 | 61篇 |
2010年 | 31篇 |
2009年 | 47篇 |
2008年 | 43篇 |
2007年 | 52篇 |
2006年 | 51篇 |
2005年 | 37篇 |
2004年 | 45篇 |
2003年 | 41篇 |
2002年 | 46篇 |
2001年 | 40篇 |
2000年 | 30篇 |
1999年 | 25篇 |
1998年 | 26篇 |
1997年 | 15篇 |
1996年 | 18篇 |
1995年 | 16篇 |
1994年 | 17篇 |
1993年 | 14篇 |
1992年 | 9篇 |
1991年 | 16篇 |
1990年 | 12篇 |
1989年 | 8篇 |
1988年 | 13篇 |
1987年 | 11篇 |
1986年 | 6篇 |
1985年 | 21篇 |
1984年 | 18篇 |
1983年 | 11篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1979年 | 15篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1971年 | 5篇 |
1970年 | 4篇 |
排序方式: 共有1094条查询结果,搜索用时 31 毫秒
911.
William J. Chaplin Andrew M. Dumbill Yvonne P. Elsworth George R. Isaak Clive P. McLeod Brek A. Miller Roger New Balázs Pintér 《Solar physics》2004,220(2):307-316
The Birmingham Solar-Oscillations Network (BiSON) has acquired high-precision solar mean magnetic field (SMMF) data on a 40-s
cadence for a decade. We present attempts to compare such data from recent years with the occurrence of coronal mass ejections
(CMEs) as recorded by LASCO, using correlation techniques applied to measurements from different BiSON instruments to maximise
the sensitivity to CME-related SMMF responses. SMMF measurements were recorded at the time of occurrence of several hundred
CMEs. No CME event shows a convincing response in our SMMF data at short periods setting a threshold amplitude of 12 mG. By
averaging data sets we are able to set lower thresholds, which depend somewhat on the distribution of response strengths.
A brief summary of the very first results of this study is also given in Chaplin et al. 相似文献
912.
913.
914.
James E.H. Turner Bryan W. Miller Tracy L. Beck Inseok Song Andrew J. Cooke Robert L. Seaman Francisco G. Valds 《New Astronomy Reviews》2006,49(10-12):655
We present a brief overview of facilities for Integral Field Spectroscopy at the Gemini Observatory. These include four optical and near-infrared IFUs suitable for high spatial resolution work and a suite of tasks for handling IFU data in the Gemini IRAF package. We describe the tools for data reduction that are available now or planned in the near future, helping investigators make productive use of these ground-breaking instruments. Further details on the individual IFUs, specific science applications and reduction examples are given in associated presentations by Beck et al., Carrasco et al., Trancho et al. and Winge et al. 相似文献
915.
916.
917.
918.
919.
W. J.Chaplin Y.Elsworth G. R.Isaak B. A.Miller R.New 《Monthly notices of the Royal Astronomical Society》2002,330(3):731-736
We make use of 3456 d of observations of the low-ℓ p-mode oscillations of the Sun in order to study the evolution over time of the measurement precision of the radial eigenfrequencies. These data were collected by the ground-based Birmingham Solar-Oscillations Network (BiSON) between 1991 January and 2000 June. When the power spectrum of the complete time series is fitted, the analysis yields frequency uncertainties that are close to those expected from the returned coherence times of the modes. The slightly elevated levels compared with the prediction appear to be consistent with a degradation of the signal-to-noise ratio in the spectrum that is the result of the influence of the window function of the observations (duty cycle 71 per cent). The fractional frequency precision reaches levels of a several parts in 106 for many of the modes. The corresponding errors reported from observations made by the GOLF instrument on board the ESA/NASA SOHO satellite, when extrapolated to the length of the BiSON data set, are shown to be (on average) about ∼25 per cent smaller than their BiSON counterparts owing to the uninterrupted nature of the data from which they were derived.
An analysis of the BiSON data in contiguous segments of different lengths, T , demonstrates that the frequency uncertainties scale as T−1/2 . This is to be expected in the regime where the coherence (life) times of the modes, τ n ℓ , are smaller than the observing time T (the 'oversampled' regime). We show that mode detections are only now beginning to encroach on the 'undersampled' regime (where T < τ n ℓ ) . 相似文献
An analysis of the BiSON data in contiguous segments of different lengths, T , demonstrates that the frequency uncertainties scale as T
920.