全文获取类型
收费全文 | 3168篇 |
免费 | 126篇 |
国内免费 | 19篇 |
专业分类
测绘学 | 114篇 |
大气科学 | 357篇 |
地球物理 | 658篇 |
地质学 | 981篇 |
海洋学 | 341篇 |
天文学 | 606篇 |
综合类 | 4篇 |
自然地理 | 252篇 |
出版年
2023年 | 10篇 |
2022年 | 12篇 |
2021年 | 33篇 |
2020年 | 45篇 |
2019年 | 47篇 |
2018年 | 91篇 |
2017年 | 67篇 |
2016年 | 118篇 |
2015年 | 67篇 |
2014年 | 101篇 |
2013年 | 151篇 |
2012年 | 147篇 |
2011年 | 176篇 |
2010年 | 147篇 |
2009年 | 203篇 |
2008年 | 195篇 |
2007年 | 163篇 |
2006年 | 139篇 |
2005年 | 119篇 |
2004年 | 127篇 |
2003年 | 118篇 |
2002年 | 103篇 |
2001年 | 80篇 |
2000年 | 87篇 |
1999年 | 76篇 |
1998年 | 88篇 |
1997年 | 54篇 |
1996年 | 52篇 |
1995年 | 33篇 |
1994年 | 29篇 |
1993年 | 36篇 |
1992年 | 25篇 |
1991年 | 37篇 |
1990年 | 15篇 |
1989年 | 19篇 |
1988年 | 10篇 |
1987年 | 22篇 |
1986年 | 11篇 |
1985年 | 22篇 |
1984年 | 27篇 |
1983年 | 22篇 |
1982年 | 17篇 |
1981年 | 10篇 |
1980年 | 14篇 |
1979年 | 11篇 |
1978年 | 9篇 |
1977年 | 11篇 |
1976年 | 14篇 |
1975年 | 13篇 |
1973年 | 9篇 |
排序方式: 共有3313条查询结果,搜索用时 31 毫秒
11.
K. A. van der Hucht 《Astronomy and Astrophysics Review》1992,4(2):123-159
Summary Recent literature on Population I Wolf-Rayet star research extending from the Milky Way to blue compact dwarf galaxies is reviewed, broken down into inventory, basic parameters and galactic distribution, atmospheres, binaries, intrinsic variability, mass loss, enrichment and evolution. Also the incidence of Wolf-Rayet stars with variable non-thermal radio emission, excess X-ray fluxes, and episodic/periodic IR excesses is reviewed. These phenomena appear to be associated with wind-wind interaction in wide long-period WR+OB binaries and with wind-compact object interaction in WR+c binaries, with orbit sizes of the order of magnitude of the WR radio photosphere sizes or larger. 相似文献
12.
R. T. Schilizzi W. Aldrich B. Anderson A. Bos R. M. Campbell J. Canaris R. Cappallo J. L. Casse A. Cattani J. Goodman H. J. van Langevelde A. Maccafferri R. Millenaar R. G. Noble F. Olnon S. M. Parsley C. Phillips S. V. Pogrebenko D. Smythe A. Szomoru H. Verkouter A. R. Whitney 《Experimental Astronomy》2001,12(1):49-67
13.
14.
刘少明 《大地测量与地球动力学》2004,24(4):13-19
对1999年8月11日日全食阴影扫过欧洲期间,设在Annelles,Uccle,Walferdange和Bondy弹簧和超导重力仪的记录进行了分析.为了确定月亮对太阳万有引力可能的遮挡效应的极限,对超导和弹簧重力仪记录进行了比较.同时也对LCR和阿斯卡尼亚重力仪观测结果进行了讨论.结论是如果日食重力吸引效应存在,它应在超导重力仪±1 nm/s2(0.1×10-8ms-2)的观测精度范围之内.研究发现在以上情形下,弹簧和超导重力仪都在它们的精度范围内工作,并且日食引起的异常环境干扰可能使重力信号有重大的改变. 相似文献
15.
16.
Universal cokriging is used to obtain predictions when dealing with multivariate random functions. An important type of nonstationarity is defined in terms of multivariate random functions with increments which are stationary of orderk. The covariance between increments of different variables is modeled by means of the pseudo-cross-covariance function. Criteria are formulated to which the parameters of pseudo-cross-covariance functions must comply so as to ensure positive-definiteness. Cokriging equations and the induced cokriging equations are given. The study is illustrated by an example from soil science. 相似文献
17.
Angelika van der Linde 《Mathematical Geology》1993,25(1):1-7
Least squares estimation (LSE) is theoretically related to quadratic unbiased estimation of variance components. It is argued that these methods of estimation of variance components essentially generalize LSE though they are not formally equivalent. 相似文献
18.
A palaeotemperature reconstruction based on periglacial phenomena in Europe north of approximately 51 °N, is compared with high‐resolution regional climate model simulations of the marine oxygen isotope Stage 3 (Stage 3) palaeoclimate. The experiments represent Stage 3 warm (interstadial), Stage 3 cold (stadial) and Last Glacial Maximum climatic conditions. The palaeotemperature reconstruction deviates considerably for the Stage 3 cold climate experiments, with mismatches up to 11 °C for the mean annual air temperature and up to 15 °C for the winter temperature. However, in this reconstruction various factors linking climate and permafrost have not been taken into account. In particular a relatively thin snow cover and high climatic variability of the glacial climate could have influenced temperature limits for ice‐wedge growth. Based on modelling the 0 °C mean annual ground temperature proves to be an appropriate upper temperature limit. Using this limit, mismatches with the Stage 3 cold climate experiments have been reduced but still remain. We therefore assume that the Stage 3 ice wedges were generated during short (decadal time‐scale) intervals of extreme cold climate, below the mean temperatures indicated by the Stage 3 cold climate model simulations. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
19.
20.
P. G. Jonker G. Nelemans Z. Wang A. K. H. Kong D. Chakrabarty M. Garcia P. J. Groot M. van der Klis T. Kerr B. Mobasher M. Sullivan T. Augusteijn B. W. Stappers P. Challis R. P. Kirshner J. Hjorth A. Delsanti 《Monthly notices of the Royal Astronomical Society》2003,344(1):201-206
We have obtained optical and near-infrared images of the field of the accreting millisecond X-ray pulsar XTE J1751−305. There are no stars in the 0.7-arcsec error circle (0.7 arcsec is the overall uncertainty arising from tying the optical and X-ray images and from the intrinsic uncertainty in the Chandra X-ray astrometric solution). We derive limiting magnitudes for the counterpart of R > 23.1, I > 21.6, Z > 20.6, J > 19.6 and K > 19.2 . We compare these upper limits with the magnitudes one would expect for simple models for the possible donor stars and the accretion disc subject to the reddening observed in X-rays for XTE J1751−305 and when put at the distance of the Galactic Centre (8.5 kpc). We conclude that our non-detection does not constrain any of the models for the accretion disc or possible donor stars. Deep, near-infrared images obtained during quiescence will, however, constrain possible models for the donor stars in this ultracompact system. 相似文献