全文获取类型
收费全文 | 1046篇 |
免费 | 38篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 30篇 |
大气科学 | 68篇 |
地球物理 | 210篇 |
地质学 | 348篇 |
海洋学 | 104篇 |
天文学 | 238篇 |
综合类 | 4篇 |
自然地理 | 87篇 |
出版年
2023年 | 4篇 |
2021年 | 9篇 |
2020年 | 12篇 |
2019年 | 17篇 |
2018年 | 24篇 |
2017年 | 22篇 |
2016年 | 28篇 |
2015年 | 20篇 |
2014年 | 29篇 |
2013年 | 61篇 |
2012年 | 39篇 |
2011年 | 50篇 |
2010年 | 44篇 |
2009年 | 57篇 |
2008年 | 73篇 |
2007年 | 65篇 |
2006年 | 56篇 |
2005年 | 37篇 |
2004年 | 47篇 |
2003年 | 40篇 |
2002年 | 35篇 |
2001年 | 27篇 |
2000年 | 30篇 |
1999年 | 21篇 |
1998年 | 20篇 |
1997年 | 11篇 |
1996年 | 11篇 |
1995年 | 12篇 |
1994年 | 8篇 |
1993年 | 14篇 |
1992年 | 6篇 |
1990年 | 13篇 |
1989年 | 6篇 |
1988年 | 10篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 13篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 10篇 |
1981年 | 11篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 9篇 |
1971年 | 6篇 |
1910年 | 4篇 |
排序方式: 共有1089条查询结果,搜索用时 15 毫秒
81.
82.
Mark L. Brusseau Kenneth C. Carroll Zhilin Guo Jon Mainhagu 《Environmental Earth Sciences》2018,77(18):648
The concept of the Borehole Diffusive Flux Apparatus (BDFA) is presented herein. The BDFA is an innovative apparatus designed to provide continuous direct access to an undisturbed column of sediment that can be monitored at multiple discrete vertical intervals to provide high-resolution characterization of local-scale mass transfer and attenuation. The conceptual basis and technical design of the device are presented, along with an example of borehole design and installation at a field site. Mathematical simulations are used to illustrate its application for two scenarios. The results of these simulations indicate that test periods of several weeks to a few months should be sufficient to obtain robust results. The device has the potential to improve our ability to characterize critical mass-transfer and attenuation processes and to quantify the associated rates. This information is key to the evaluation of remediation alternatives, for enhancing the accuracy of mathematical models, and to support more effective long-term management of large groundwater contaminant plumes present at many sites. 相似文献
83.
Jonathan Irwin Suzanne Aigrain Simon Hodgkin Keivan G. Stassun Leslie Hebb Mike Irwin Estelle Moraux Jerome Bouvier Aude Alapini Richard Alexander D. M. Bramich Jon Holtzman Eduardo L. Martín Mark J. McCaughrean Frédéric Pont P. E. Verrier María Rosa Zapatero Osorio 《Monthly notices of the Royal Astronomical Society》2007,380(2):541-550
We present a general recipe for constructing N -body realizations of galaxies comprising near spherical and disc components. First, an exact spherical distribution function for the spheroids (halo and bulge) is determined, such that it is in equilibrium with the gravitational monopole of the disc components. Second, an N -body realization of this model is adapted to the full disc potential by growing the latter adiabatically from its monopole. Finally, the disc is sampled with particles drawn from an appropriate distribution function, avoiding local-Maxwellian approximations. We performed test simulations and find that the halo and bulge radial density profile very closely match their target model, while they become slightly oblate due to the added disc gravity. Our findings suggest that vertical thickening of the initially thin disc is caused predominantly by spiral and bar instabilities, which also result in a radial re-distribution of matter, rather than scattering off interloping massive halo particles. 相似文献
84.
Michael W. Busch Steven J. Ostro Jon D. Giorgini Ellen S. Howell Alice A. Hine Irwin I. Shapiro 《Icarus》2007,186(2):581-584
In November 2005, we observed the moons of Mars using the Arecibo 2380-MHz (13-cm) radar, obtaining a result for the OC radar albedo of Phobos (0.056±0.014) consistent with its previously reported radar albedo and implying an upper bound on its near-surface bulk density of . We detected Deimos by radar for the first time, finding its OC radar albedo to be 0.021±0.006, implying an upper bound on its near-surface density of , consistent with a high-porosity regolith. We briefly discuss reasons for these low radar albedos, Deimos' being possibly the lowest of any Solar System body yet observed by radar. 相似文献
85.
Russell Cannon Michael Drinkwater Alastair Edge Daniel Eisenstein Robert Nichol Phillip Outram Kevin Pimbblet Roberto De Propris Isaac Roseboom David Wake Paul Allen Joss Bland-Hawthorn Terry Bridges Daniel Carson Kuenley Chiu Matthew Colless Warrick Couch Scott Croom Simon Driver Stephen Fine Paul Hewett Jon Loveday Nicholas Ross Elaine M. Sadler Tom Shanks Robert Sharp J. Allyn Smith Chris Stoughton Peter Weilbacher Robert J. Brunner Avery Meiksin Donald P. Schneider 《Monthly notices of the Royal Astronomical Society》2006,372(1):425-442
86.
Progress in Carrier Phase Time Transfer 总被引:1,自引:0,他引:1
Jim Ray Felicitas Arias Gérard Petit Tim Springer Thomas Schildknecht Jon Clarke Jan Johansson 《GPS Solutions》2001,4(4):47-54
The progress of the joint Pilot Project for time transfer, formed by the International GPS Service (IGS) and the Bureal International
des Poids et Mesures (BIPM), was recently reviewed. Three notable milestones were set. (1) The IGS will implement, at least
in a test mode, an internally realized time scale based on an integration of combined frequency standards within the IGS network.
This will eventually become the reference time scale for all IGS clock products (instead of the current GPS broadcast time).
(2) A new procedure for combined receiver and satellite clock products will be implemented officially in November 2000. Receiver
clocks are an entirely new product of the IGS. (3) The BIPM will coordinate an effort to calibrate all Ashtech Z12-T (and
possibly other) receivers suitable for time transfer applications, either differentially or absolutely. Progress reports will
be presented publicly in the spring 2001. ? 2001 John Wiley & Sons, Inc. 相似文献
87.
Steven J. OSTRO R. Scott HUDSON Lance A. M. BENNER Michael C. NOLAN Jon D. GIORGINI Daniel J. SCHEERES Raymond F. JURGENS Randy ROSE 《Meteoritics & planetary science》2001,36(9):1225-1236
Abstract— Goldstone and Arecibo delay‐Doppler radar imaging of asteroid 1998 ML 14 shortly after its discovery reveals a 1 km diameter spheroid with prominent topography on one side and subdued topography on the other. The object's radar and optical properties are typical for S‐class near‐Earth asteroids. The gravitational slopes of a shape model derived from the images and assumed to have a uniform density are shallow, exceeding 30° over only 4% of the surface. If 1998 ML14's density distribution is uniform, then its orbital environment is similar to a planetary body with a spheroidal gravitational field and is relatively stable. Integration of a radar‐refined orbit reveals that the 1998 apparition was the asteroid's closest approach to Earth since at least 1100 and until 2283, when it approaches to within 2.4 lunar distances. Outside of that time interval, orbit uncertainties based on the present set of observations preclude reliable prediction. 相似文献
88.
89.
90.
I. González Hernández M. Díaz Alfaro K. Jain W. K. Tobiska D. C. Braun F. Hill F. Pérez Hernández 《Solar physics》2014,289(2):503-514
Solar magnetic indices are used to model the solar irradiance and ultimately to forecast it. However, the observation of such indices is generally limited to the Earth-facing hemisphere of the Sun. Seismic maps of the far side of the Sun have proven their capability to locate and track medium–large active regions at the non-visible hemisphere. We present here the possibility of using the average signal from these seismic far-side maps, combined with similarly calculated near-side maps, as a proxy to the full-Sun magnetic activity. 相似文献