全文获取类型
收费全文 | 28064篇 |
免费 | 562篇 |
国内免费 | 357篇 |
专业分类
测绘学 | 705篇 |
大气科学 | 2339篇 |
地球物理 | 6069篇 |
地质学 | 9653篇 |
海洋学 | 2680篇 |
天文学 | 5592篇 |
综合类 | 77篇 |
自然地理 | 1868篇 |
出版年
2020年 | 184篇 |
2019年 | 187篇 |
2018年 | 416篇 |
2017年 | 389篇 |
2016年 | 586篇 |
2015年 | 384篇 |
2014年 | 608篇 |
2013年 | 1420篇 |
2012年 | 620篇 |
2011年 | 956篇 |
2010年 | 803篇 |
2009年 | 1075篇 |
2008年 | 998篇 |
2007年 | 946篇 |
2006年 | 942篇 |
2005年 | 837篇 |
2004年 | 862篇 |
2003年 | 802篇 |
2002年 | 784篇 |
2001年 | 648篇 |
2000年 | 641篇 |
1999年 | 618篇 |
1998年 | 577篇 |
1997年 | 585篇 |
1996年 | 489篇 |
1995年 | 478篇 |
1994年 | 461篇 |
1993年 | 428篇 |
1992年 | 393篇 |
1991年 | 342篇 |
1990年 | 397篇 |
1989年 | 305篇 |
1988年 | 348篇 |
1987年 | 391篇 |
1986年 | 338篇 |
1985年 | 500篇 |
1984年 | 536篇 |
1983年 | 541篇 |
1982年 | 437篇 |
1981年 | 423篇 |
1980年 | 449篇 |
1979年 | 389篇 |
1978年 | 404篇 |
1977年 | 348篇 |
1976年 | 381篇 |
1975年 | 343篇 |
1974年 | 381篇 |
1973年 | 369篇 |
1972年 | 236篇 |
1971年 | 187篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
CHRIS W. LEE 《Geology Today》1991,7(4):133-136
Each year many hundreds, if not thousands, of Earth-science students visit the coastline at Ogmore-by-Sea, mid-Glamorgan. They study the excellent exposures of Lower Carboniferous Limestone, with their well-preserved coral and other shelly faunas, together with the presumed late Triassic 'breccias'* that rest unconformably on top. A study of the cements within the breccias may give an insight into syndepositional mineralization and the formation of sedimentary basins linked to the opening of the Atlantic in early Mesozoic times. 相似文献
112.
Jeremy Allington-Smith Graham Murray Robert Content George Dodsworth Bryan W. Miller James Turner Inger Jorgensen Isobel Hook 《Experimental Astronomy》2002,13(1):1-37
We describe the integral field unit (IFU) which converts the Gemini Multiobject Spectrograph (GMOS) installed on the Gemini-North telescope to an integral field spectrograph,which produces spectra over a contiguous field of view of 7 × 5 arcsec with spatial sampling of 0.2 arcsecover the wavelength range 0.4-1.0 μm.GMOS is converted to this mode by the remote insertion of the IFU into thebeam in place of the masks used for the multiobject mode. A separate fieldof half the area of the main field, but otherwise identical, is alsoprovided to improve background subtraction. The IFU contains 1500lenslet-coupled fibres and was the first facility of any type for integralfield spectroscopy employed on an 8/10 m telescope.We describe the design, construction and testing of the GMOS IFU and present measurements of the throughput both in the laboratory and at the telescope. We compare these with a theoretical prediction made before construction started. All are in good agreement with each other, with the on-telescope throughput exceeding 60% (averaged over wavelength). Finallywe show an example of data obtained during commissioning to illustrate the power of the device. 相似文献
113.
W.J. Boulton 《Planetary and Space Science》1985,33(6):721-734
Orbital parameters of the satellite NIMBUS 1 ROCKET (1964-52B) have been determined at 285 epochs using about 14,500 optical and radar observations during the last 2233 days of its life. 1964-52B was in an orbit inclined at about 98.7° to the Equator and it decayed on 13 August 1974. The orbital elements were found using the RAE orbit refinement program PROP 6 giving average orbital accuracies in perigee height and inclination at 110 m and 0.002° respectively. 相似文献
114.
115.
A new updated version of the MSK macroseismic intensity scale has been prepared by a Working Group of the European Seismological Commission and has been published in April 1993 (European Macroseismic Scale 1992: updated MSK scale, 1993, ed. by G. Grünthal, Cahiers du Centre Européen de Geodynamique et de Séismologie, no. 7). 相似文献
116.
F. W. Shotton D. H. Keen G. R. Coope A. P. Currant P. L. Gibbard M. Aalto S. M. Peglar J. E. Robinson 《第四纪科学杂志》1993,8(4):293-325
A complex of channels underlying the Baginton-Lillington Gravel (Baginton Formation) at Waverley Wood Quarry, Warwickshire is described. Fossil pollen and plant macrofossils, Coleoptera, Ostracoda, Mollusca and Mammalia are described from the channel-fill deposits. Consideration of all the evidence allows the identification of four separate stages of channel fill which largely occurred under a cool temperate climate. At the top of Channel 2 evidence for a cold, continental climatic episode can be recognised, suggesting that the whole complex was deposited under a fluctuating climate at the end of a temperate stage. At two levels in the channels human artefacts were recovered confirming the presence of Palaeolithic people in Warwickshire during the deposition of the sediments. Amino-acid geochronology suggests an age within the ‘Cromerian Complex’ Stage for the channels. The small vertebrate and molluscan faunas indicate that the deposits are no older than the latter part of the ‘Cromerian Complex’ Stage of East Anglia. The regional stratigraphic significance of the Waverley Wood succession is outlined. 相似文献
117.
118.
119.
In this paper we show that a change in the signs of some of the metric components of the solution of the field equations for
the classical cosmic string results in a solution which we interpret as a time-dependent wall composed of tachyons. We show
that the walls have the property of focusing the paths of particles which pass through them. As an illustration of this focusing,
we demonstrate the results of a simple simulation of the interaction between one such tachyon wall and a rotating disk of
point masses. This interaction leads to the temporary formation of spiral structures. These spiral structures exist for a
time on the order of one galactic rotation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
120.
Guinevere Kauffmann Timothy M. Heckman Simon D. M. White Stéphane Charlot Christy Tremonti Jarle Brinchmann Gustavo Bruzual Eric W. Peng Mark Seibert Mariangela Bernardi Michael Blanton Jon Brinkmann Francisco Castander Istvan Csábai Masataka Fukugita Zeljko Ivezic Jeffrey A. Munn Robert C. Nichol Nikhil Padmanabhan Aniruddha R. Thakar David H. Weinberg Donald York 《Monthly notices of the Royal Astronomical Society》2003,341(1):33-53