全文获取类型
收费全文 | 797篇 |
免费 | 47篇 |
国内免费 | 13篇 |
专业分类
测绘学 | 14篇 |
大气科学 | 45篇 |
地球物理 | 237篇 |
地质学 | 178篇 |
海洋学 | 61篇 |
天文学 | 140篇 |
自然地理 | 182篇 |
出版年
2021年 | 10篇 |
2020年 | 9篇 |
2019年 | 15篇 |
2018年 | 15篇 |
2017年 | 13篇 |
2016年 | 27篇 |
2015年 | 19篇 |
2014年 | 17篇 |
2013年 | 44篇 |
2012年 | 23篇 |
2011年 | 31篇 |
2010年 | 19篇 |
2009年 | 48篇 |
2008年 | 41篇 |
2007年 | 33篇 |
2006年 | 31篇 |
2005年 | 32篇 |
2004年 | 43篇 |
2003年 | 26篇 |
2002年 | 39篇 |
2001年 | 28篇 |
2000年 | 18篇 |
1999年 | 13篇 |
1998年 | 21篇 |
1997年 | 21篇 |
1996年 | 16篇 |
1995年 | 8篇 |
1994年 | 12篇 |
1993年 | 12篇 |
1992年 | 10篇 |
1991年 | 23篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 7篇 |
1987年 | 10篇 |
1986年 | 5篇 |
1985年 | 15篇 |
1984年 | 13篇 |
1983年 | 6篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 9篇 |
1975年 | 7篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1970年 | 4篇 |
1965年 | 2篇 |
1924年 | 2篇 |
排序方式: 共有857条查询结果,搜索用时 15 毫秒
731.
We present a new approach for the precise and accurate forward modeling of the solar oscillation ℓ−ν power spectrum. The approach
is designed to provide the basis for a streamlined solar seismic inversion without measurements of the p-mode frequencies. The new strategy represents a paradigm change in how information is extracted from the oscillation spectrum.
It also represents a step toward the ideal case of inferring the Sun's properties directly from the raw observations. 相似文献
732.
Seismology of the solar atmosphere 总被引:1,自引:0,他引:1
Wolfgang Finsterle Stuart M. Jefferies Alessandro Cacciani Paolo Rapex Cynthia Giebink Allister Knox Vincenzo DiMartino 《Solar physics》2004,220(2):317-331
We describe a new instrument for seismically probing the properties of the Sun's lower atmosphere, and present some first
results from an observational campaign carried out at the geographic South Pole during the austral summer of 2002/2003. A
preliminary analysis of the data (simultaneous, high-cadence observations of the velocity signals from the photosphere and
low chromosphere) shows that the well-known suppression of acoustic power in regions of strong magnetic field, and enhancement
of high-frequency power around active regions (acoustic halos), are both consistent with a spreading out of the magnetic field
lines with increasing height in the atmosphere. The data have also revealed some unexpected wave behavior. First, evanescent-like
waves are found at frequencies substantially above the acoustic cut-off frequency in regions of intermediate magnetic field.
Second, upward- and downward-propagating waves are detected in areas of strong magnetic field such as sunspots and plage:
even at frequencies below the acoustic cut-off frequency. Third, the wave behavior in regions of strong magnetic field can
change over periods of a few hours from propagating to evanescent. While we have no concrete explanation for the first two
results, the latter result opens up the question of whether sound waves are involved in short-term events such as flares or
CME's. 相似文献
733.
Edward Conway Steve Maddox Vivienne Wild John A. Peacock Ed Hawkins Peder Norberg Darren S. Madgwick Ivan K. Baldry Carlton M. Baugh Joss Bland-Hawthorn Terry Bridges Russell Cannon Shaun Cole Matthew Colless Chris Collins Warrick Couch Gavin Dalton Roberto De Propris Simon P. Driver George Efstathiou Richard S. Ellis Carlos S. Frenk Karl Glazebrook Carole Jackson Bryn Jones Ofer Lahav Ian Lewis Stuart Lumsden Will Percival Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2005,356(2):456-474
We present an analysis of the relative bias between early- and late-type galaxies in the Two-degree Field Galaxy Redshift Survey (2dFGRS) – as defined by the η parameter of Madgwick et al., which quantifies the spectral type of galaxies in the survey. We calculate counts in cells for flux-limited samples of early- and late-type galaxies, using approximately cubical cells with sides ranging from 7 to 42 h −1 Mpc . We measure the variance of the counts in cells using the method of Efstathiou et al., which we find requires a correction for a finite volume effect equivalent to the integral constraint bias of the autocorrelation function. Using a maximum-likelihood technique we fit lognormal models to the one-point density distribution, and develop methods of dealing with biases in the recovered variances resulting from this technique. We then examine the joint density distribution function, f (δE , δL ) , and directly fit deterministic bias models to the joint counts in cells. We measure a linear relative bias of ≈1.3, which does not vary significantly with ℓ. A deterministic linear bias model is, however, a poor approximation to the data, especially on small scales (ℓ≤ 28 h −1 Mpc) where deterministic linear bias is excluded at high significance. A power-law bias model with index b 1 ≈ 0.75 is a significantly better fit to the data on all scales, although linear bias becomes consistent with the data for ℓ≳ 40 h −1 Mpc . 相似文献
734.
Fibrous illite is one of the most important cements that grows within sandstones during burial, and the only one which is commonly dated using the K–Ar age technique. A small quantity of illite can dramatically reduce porefluid flow rates within a sandstone, thus making oil recovery uneconomic. Illite ages potentially correspond to geological events such as hydrocarbon filling of a sandstone reservoir, providing calibration to basin models. Yet the fundamental processes controlling fibrous illite growth are not understood. This contribution presents a new theory for illite growth within sandstones that explains the fibrous morphology of illite, the restricted range of illite K–Ar age dates compared to the age of the host sandstones, and the lack of 0-Myr-old illite reported. The growth of fibrous illite as an authigenic cement may be controlled by nucleation kinetics, and not by thermodynamic or growth kinetic considerations as has been previously assumed. 相似文献
735.
Carmen Morales Joaquín Trapero José F. Gómez Verónica Orozco Alvaro Gimenez Stuart Bowyer Jerry Edelstein Eric Korpela Michael Lampton Jeff Cobb 《Astrophysics and Space Science》2001,276(1):141-150
We present here stellar spectra of B stars obtained with the EURD spectrograph, one of the three instruments on board MINISAT-01. EURD is a spectrograph specially designed to detect diffuse radiation in thewavelength range between 350 and 1100 Å with 5 Å spectral resolution. EURD main scientific targets are: the spectrum of interstellar medium,atmospheric airglow, decaying neutrinos, Moon and early type stars. 相似文献
736.
Takuya Fujiyoshi Craig H. Smith Toby J. T. Moore Stuart L. Lumsden David K. Aitken Patrick F. Roche 《Monthly notices of the Royal Astronomical Society》2005,356(3):801-809
We present near-infrared broad-band JHK ' images of the southern massive star-forming region G333.6−0.2. The slope of the K -luminosity function towards the region (0.24 ± 0.01) is considered to be equivalent to that expected for main-sequence stars in the solar neighbourhood. Point sources with their ( H − K ) colour greater than 1 are more likely to be located in extended emission and it is suggested that these objects are physically associated with the H ii region. 相似文献
737.
Near-infrared (JHK) images of the nucleus of the barred spiral galaxy M100 (NGC 4321) have been obtained using a high-bandwidth tip-tilt secondary
and fast guider system on the 3.8 m United Kingdom Infrared Telescope (UKIRT). The resulting images, with a resolution of
0.34″ at K, reveal for the first time a host of compact ‘knots’, which appear to be the result of a recent burst (or bursts) of star
formation. Confirmation of this comes from K-band spectroscopy of these knots with CGS4 on UKIRT, which shows Brγ emission and CO absorption features. A comparison with
starburst evolutionary models suggests ages for these knots of between 17 and 27 Myr, and a stellar population dominated by
late-type supergiants.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
738.
739.
740.
Stuart J. Jones 《地学学报》2004,16(3):121-127
An understanding of how drainage patterns respond to tectonics can provide an insight into past deformational events within mountain belts and where sediment flux is supplied to depositional basins. The transverse rivers draining the Spanish Pyrenees show sudden diversions to axial courses and the capture of lateral systems producing large trunk rivers that break through the thrust front at structurally controlled points. The drainage reorganization from the initial regularly spaced pattern in the Late Eocene caused by the growth of thrust‐controlled topography influenced the location of outlets into the Ebro basin. The headward capture and merger of rivers as a result of structural diversion formed two large terminal fan systems during the Oligo‐Miocene along the Pyrenean thrust front. The early structural topographic controls on drainage evolution will have long‐term effects on sedimentation and stratigraphic architecture of foreland basins. This will only be maintained as long as there is tectonic uplift and the river systems strive to re‐attain a regular drainage spacing across the orogenic belt as partly achieved in the Pyrenees. 相似文献