全文获取类型
收费全文 | 3560篇 |
免费 | 334篇 |
国内免费 | 321篇 |
专业分类
测绘学 | 851篇 |
大气科学 | 165篇 |
地球物理 | 435篇 |
地质学 | 914篇 |
海洋学 | 198篇 |
天文学 | 206篇 |
综合类 | 320篇 |
自然地理 | 1126篇 |
出版年
2024年 | 32篇 |
2023年 | 61篇 |
2022年 | 182篇 |
2021年 | 181篇 |
2020年 | 159篇 |
2019年 | 205篇 |
2018年 | 119篇 |
2017年 | 187篇 |
2016年 | 189篇 |
2015年 | 157篇 |
2014年 | 154篇 |
2013年 | 219篇 |
2012年 | 185篇 |
2011年 | 169篇 |
2010年 | 140篇 |
2009年 | 168篇 |
2008年 | 184篇 |
2007年 | 193篇 |
2006年 | 160篇 |
2005年 | 149篇 |
2004年 | 169篇 |
2003年 | 135篇 |
2002年 | 118篇 |
2001年 | 90篇 |
2000年 | 95篇 |
1999年 | 70篇 |
1998年 | 59篇 |
1997年 | 51篇 |
1996年 | 39篇 |
1995年 | 32篇 |
1994年 | 34篇 |
1993年 | 21篇 |
1992年 | 17篇 |
1991年 | 26篇 |
1990年 | 14篇 |
1989年 | 18篇 |
1988年 | 10篇 |
1987年 | 11篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有4215条查询结果,搜索用时 0 毫秒
731.
A. Bragaglia F. R. Ferraro F. Fusi Pecci R. Buonanno C. E. Corsi I. Ferraro G. Iannicola 《Journal of Astrophysics and Astronomy》1987,8(1):57-68
Using a first approximation to the Hubble space telescope point-spread function, the problems concerning observation and reduction
of globular clusters in the Andromeda nebula are analysed through a simulation procedure in order to study the feasibility
of accurate photometry of individual stars in the clusters. 相似文献
732.
733.
734.
735.
银河系厚盘的本地空间密度 总被引:1,自引:0,他引:1
本文利用北银极天区的现代恒星计数资料,采用标准的银河系模型,通过恒星统计积分方程对参数值组合模型的亮度函数进行计数分析,证明了银河系厚盘恒星成份存在的必要性,并进一步得出太阳附近厚盘成份的空间密度的最佳期望值为薄盘密度的0.041. 相似文献
736.
737.
A. M. Heras E. Wieprecht H. Feuchtgruber F. Lahuis K. Leech R. Lorente P. Morris A. Salama B. Vandenbussche 《Experimental Astronomy》2000,10(2-3):177-197
We present a trend analysis of the ISO-SWS detector performance and a study of the space radiation effects on the SWS detectors. In particular, dark currents, dark current noise and detector responses have been checked as a function of time through the mission and as a function of time in arevolution. The results show that these parameters were stable during the mission in all bandsbut for band 3 (Si:As). Dark currents and responses were found to be higherin the first hours following the start of the science window,especially in band 2 (Si:Ga). We have studied the impacts of cosmic rays and radiation belt particles on the SWS detectors, as well as of the only large solar proton event on November 6, 1997,that occurred during the ISO mission (operated during solar minimum).The observed glitch rates in all SWS bands are found to be between 2 and4 times higher than the value predicted by the CREME96 model for the cosmic ray flux in the period considered. The bands that registered the highest glitch rates showed also a correlation with the electron fluxes measured on theGOES 9 spacecraft. From the distribution of glitchheights (voltage jumps in the detector signal), we have derived the deposited energy distributions of the particles hits. Our results lead to the conclusion that secondaryparticles produced in the shield and the detectors contributed at least as much as cosmic rays to the observed glitch rate. The effects on the detectors of the November 6, 1997 event, which caused that all observationsin a revolution were declared failed, are described in detail. 相似文献
738.
739.
空间碎片观测精度分析 总被引:1,自引:0,他引:1
文章分别用内符合精度和外符合精度两种精度指标对云南天文台SBG望远镜的观测数据进行判定,确定了其观测精度。得到高轨空间碎片的观测精度约为2″,和低轨空间碎片的观测精度约为7″,并对观测误差的来源作了一些初步的分析。 相似文献
740.
Anirudh Pradhan G. S. Khadekar Deepak Srivastava 《Astrophysics and Space Science》2006,305(4):415-421
Implications of cosmological model with a cosmological term of the form , where β is a constant, are analyzed in multidimensional space time. The proper distance, the luminosity distance-redshift, the angular diameter distance-redshift, and look back time-redshift for the model are presented. It has been shown that models are found to be compatible with the present observations. This work, has thus generalized to higher dimensions the well-known result in four dimensional space time. It is found that the difference is significant at least in the principal to the anologous situation in four dimensional space time. 相似文献