全文获取类型
收费全文 | 920篇 |
免费 | 32篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 25篇 |
大气科学 | 84篇 |
地球物理 | 279篇 |
地质学 | 217篇 |
海洋学 | 88篇 |
天文学 | 161篇 |
自然地理 | 103篇 |
出版年
2021年 | 8篇 |
2020年 | 10篇 |
2019年 | 10篇 |
2018年 | 13篇 |
2017年 | 13篇 |
2016年 | 23篇 |
2015年 | 16篇 |
2014年 | 20篇 |
2013年 | 41篇 |
2012年 | 23篇 |
2011年 | 40篇 |
2010年 | 38篇 |
2009年 | 50篇 |
2008年 | 34篇 |
2007年 | 34篇 |
2006年 | 49篇 |
2005年 | 43篇 |
2004年 | 48篇 |
2003年 | 40篇 |
2002年 | 29篇 |
2001年 | 33篇 |
2000年 | 22篇 |
1999年 | 17篇 |
1998年 | 23篇 |
1997年 | 18篇 |
1996年 | 12篇 |
1995年 | 13篇 |
1994年 | 18篇 |
1993年 | 12篇 |
1992年 | 22篇 |
1991年 | 9篇 |
1990年 | 15篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 13篇 |
1986年 | 11篇 |
1985年 | 14篇 |
1984年 | 9篇 |
1983年 | 16篇 |
1982年 | 13篇 |
1981年 | 13篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 9篇 |
1976年 | 3篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1970年 | 2篇 |
排序方式: 共有957条查询结果,搜索用时 15 毫秒
151.
M. J. Keith R. P. Eatough A. G. Lyne M. Kramer A. Possenti F. Camilo R. N. Manchester 《Monthly notices of the Royal Astronomical Society》2009,395(2):837-846
Modern pulsar surveys produce many millions of candidate pulsars, far more than can be individually inspected. Traditional methods for filtering these candidates, based upon the signal-to-noise ratio of the detection, cannot easily distinguish between interference signals and pulsars. We have developed a new method of scoring candidates using a series of heuristics which test for pulsar-like properties of the signal. This significantly increases the sensitivity to weak pulsars and pulsars with periods close to interference signals. By applying this and other techniques for ranking candidates from a previous processing of the Parkes Multi-beam Pulsar Survey, 28 previously unknown pulsars have been discovered. These include an eccentric binary system and a young pulsar which is spatially coincident with a known supernova remnant. 相似文献
152.
The suitability of geologic frameworks for extrapolating hydraulic conductivity (K) to length scales commensurate with hydraulic data is difficult to assess. A novel method is presented for evaluating assumed relations between K and geologic interpretations for regional-scale groundwater modeling. The approach relies on simultaneous interpretation of multiple aquifer tests using alternative geologic frameworks of variable complexity, where each framework is incorporated as prior information that assumes homogeneous K within each model unit. This approach is tested at Pahute Mesa within the Nevada National Security Site (USA), where observed drawdowns from eight aquifer tests in complex, highly faulted volcanic rocks provide the necessary hydraulic constraints. The investigated volume encompasses 40 mi3 (167 km3) where drawdowns traversed major fault structures and were detected more than 2 mi (3.2 km) from pumping wells. Complexity of the five frameworks assessed ranges from an undifferentiated mass of rock with a single unit to 14 distinct geologic units. Results show that only four geologic units can be justified as hydraulically unique for this location. The approach qualitatively evaluates the consistency of hydraulic property estimates within extents of investigation and effects of geologic frameworks on extrapolation. Distributions of transmissivity are similar within the investigated extents irrespective of the geologic framework. In contrast, the extrapolation of hydraulic properties beyond the volume investigated with interfering aquifer tests is strongly affected by the complexity of a given framework. Testing at Pahute Mesa illustrates how this method can be employed to determine the appropriate level of geologic complexity for large-scale groundwater modeling. 相似文献
153.
The 2dF Galaxy Redshift Survey: the bJ -band galaxy luminosity function and survey selection function
Peder Norberg Shaun Cole Carlton M. Baugh Carlos S. Frenk Ivan Baldry Joss Bland-Hawthorn Terry Bridges Russell Cannon Matthew Colless Chris Collins Warrick Couch Nicholas J. G. Cross Gavin Dalton Roberto De Propris Simon P. Driver George Efstathiou Richard S. Ellis Karl Glazebrook Carole Jackson Ofer Lahav Ian Lewis Stuart Lumsden Steve Maddox Darren Madgwick John A. Peacock Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,336(3):907-931
154.
Hyun-Chul Lee Thomas L. Delworth Anthony Rosati Rong Zhang Whit G. Anderson Fanrong Zeng Charles A. Stock Anand Gnanadesikan Keith W. Dixon Stephen M. Griffies 《Climate Dynamics》2013,40(1-2):327-340
The impact of climate warming on the upper layer of the Bering Sea is investigated by using a high-resolution coupled global climate model. The model is forced by increasing atmospheric CO2 at a rate of 1% per year until CO2 reaches double its initial value (after 70 years), after which it is held constant. In response to this forcing, the upper layer of the Bering Sea warms by about 2°C in the southeastern shelf and by a little more than 1°C in the western basin. The wintertime ventilation to the permanent thermocline weakens in the western Bering Sea. After CO2 doubling, the southeastern shelf of the Bering Sea becomes almost ice-free in March, and the stratification of the upper layer strengthens in May and June. Changes of physical condition due to the climate warming would impact the pre-condition of spring bio-productivity in the southeastern shelf. 相似文献
155.
Variations in the crustal structure beneath western Turkey 总被引:6,自引:0,他引:6
Paul Saunders Keith Priestley & Tuncay Taymaz 《Geophysical Journal International》1998,134(2):373-389
156.
Matthias R. Aellig Alan J. Lazarus Justin C. Kasper Keith W. Ogilvie 《Astrophysics and Space Science》2001,277(1-2):305-307
The Triana PlasMag Faraday Cup (FC) will be able to determine speed, flow angles, temperature, and density of the main solar
wind ion species with a time resolution of better than one second. Thus, the Triana PlasMag FC will enable resolution of spatial
structures as small as a few hundred kilometers as the structures convect past the spacecraft. Under typical solar wind conditions,
that size is comparable to a few proton gyroradii.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
157.
Peder Norberg Carlton M. Baugh Ed Hawkins Steve Maddox John A. Peacock Shaun Cole Carlos S. Frenk Joss Bland-Hawthorn Terry Bridges Russell Cannon Matthew Colless Chris Collins Warrick Couch Gavin Dalton Roberto De Propris Simon P. Driver George Efstathiou Richard S. Ellis Karl Glazebrook Carole Jackson Ofer Lahav Ian Lewis Stuart Lumsden Darren Madgwick Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2001,328(1):64-70
We investigate the dependence of the strength of galaxy clustering on intrinsic luminosity using the Anglo-Australian two degree field galaxy redshift survey (2dFGRS). The 2dFGRS is over an order of magnitude larger than previous redshift surveys used to address this issue. We measure the projected two-point correlation function of galaxies in a series of volume-limited samples. The projected correlation function is free from any distortion of the clustering pattern induced by peculiar motions and is well described by a power law in pair separation over the range . The clustering of galaxies in real space is well-fitted by a correlation length and power-law slope . The clustering amplitude increases slowly with absolute magnitude for galaxies fainter than M *, but rises more strongly at higher luminosities. At low luminosities, our results agree with measurements from the Southern Sky Redshift Survey 2 by Benoist et al. However, we find a weaker dependence of clustering strength on luminosity at the highest luminosities. The correlation function amplitude increases by a factor of 4.0 between and −22.5, and the most luminous galaxies are 3.0 times more strongly clustered than L * galaxies. The power-law slope of the correlation function shows remarkably little variation for samples spanning a factor of 20 in luminosity. Our measurements are in very good agreement with the predictions of the hierarchical galaxy formation models of Benson et al. 相似文献
158.
Jones Keith Pascale Federica Wanigarathna Nadeeshani Morga Mariantonietta Sargin Sinan 《Bulletin of Earthquake Engineering》2021,19(10):4115-4143
Bulletin of Earthquake Engineering - As cities become larger and more densely populated the impacts of major earthquake events on city communities become more severe. Improving community resilience... 相似文献
159.
160.
Changes in the Geometry and Volume of Rabots glaciär,Sweden, 2003–2011: Recent Accelerated Volume Loss Linked to More Negative Summer Balances 下载免费PDF全文
Keith A. Brugger Latysha Pankratz 《Geografiska Annaler: Series A, Physical Geography》2015,97(2):265-278
Terminus geometry, ice margins, and surface elevations on Rabots glaciär were measured using differential GPS during summer 2011 and compared with those similarly measured in 2003. Glacier length over the eight years decreased by ~105 m corresponding to 13 m a?1, a rate consistent with ice recession over the last several decades. Measured changes in surface elevations show that between 2003 and 2011 the glacier's volume decreased by ~27.6 ± 2.6 × 106 m3, or 3.5 ± 0.3 × 106 m3 a?1. This compares favorably with an estimate of ?28.1 ± 2.6 × 106 m3 based on a mass‐balance approach. The rate of volume loss appears, however, to have significantly increased after 2003, being substantially greater than rates determined for the intervals 1959–80, 1980–89, and 1989–2003. This increase corresponds to a sustained interval of more negative summer balances. Previous work suggests that as of 2003 Rabots glaciär had not yet completed its response to a ~1°C warming that occurred c. 1900, and thus the current marked increase rate of ice loss might reflect the effect of recent, or accelerated regional warming that occurred during the last decade superimposed on its continued response to that earlier warming. 相似文献