全文获取类型
收费全文 | 23095篇 |
免费 | 1159篇 |
国内免费 | 684篇 |
专业分类
测绘学 | 509篇 |
大气科学 | 221篇 |
地球物理 | 1256篇 |
地质学 | 4405篇 |
海洋学 | 466篇 |
天文学 | 17264篇 |
综合类 | 275篇 |
自然地理 | 542篇 |
出版年
2024年 | 49篇 |
2023年 | 89篇 |
2022年 | 186篇 |
2021年 | 163篇 |
2020年 | 175篇 |
2019年 | 237篇 |
2018年 | 124篇 |
2017年 | 127篇 |
2016年 | 159篇 |
2015年 | 278篇 |
2014年 | 271篇 |
2013年 | 282篇 |
2012年 | 369篇 |
2011年 | 414篇 |
2010年 | 454篇 |
2009年 | 1780篇 |
2008年 | 1720篇 |
2007年 | 2035篇 |
2006年 | 2021篇 |
2005年 | 1861篇 |
2004年 | 1944篇 |
2003年 | 1676篇 |
2002年 | 1486篇 |
2001年 | 1308篇 |
2000年 | 1101篇 |
1999年 | 1028篇 |
1998年 | 1168篇 |
1997年 | 354篇 |
1996年 | 245篇 |
1995年 | 371篇 |
1994年 | 378篇 |
1993年 | 168篇 |
1992年 | 103篇 |
1991年 | 111篇 |
1990年 | 95篇 |
1989年 | 153篇 |
1988年 | 104篇 |
1987年 | 104篇 |
1986年 | 79篇 |
1985年 | 44篇 |
1984年 | 30篇 |
1983年 | 27篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1977年 | 6篇 |
1905年 | 3篇 |
1900年 | 3篇 |
1897年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 484 毫秒
71.
O.V.Chumak 《中国天文和天体物理学报》2003,3(2):175-182
We present a study of the relationship between integral area and corresponding total magnetic flux for solar active regions. It is shown that some of these relationships are satisfied to simple power laws. Fractal examination showed that some of these power laws can not be justified inside the simple models of stationary magnetic flux tube aggregation. All magnetic fluxes and corresponding areas were calculated using the data measured with the Solar Magnetic Field Telescope of the Huairou Solar Observing Station in Beijing. 相似文献
72.
Wavelet Analysis of Space Solar Telescope Images 总被引:1,自引:0,他引:1
Xi-An Zhu Sheng-Zhen Jin Jing-Yu Wang Shu-Nian NingNational Astronomical Observatories Chinese Academy of Science Beijing Department of Mechanical Electric Engineering China College of Mining Technology Beijing 《中国天文和天体物理学报》2003,3(6):587-596
The scientific satellite SST (Space Solar Telescope) is an important research project strongly supported by the Chinese Academy of Sciences. Every day, SST acquires 50 GB of data (after processing) but only 10GB can be transmitted to the ground because of limited time of satellite passage and limited channel volume. Therefore, the data must be compressed before transmission. Wavelets analysis is a new technique developed over the last 10 years, with great potential of application. We start with a brief introduction to the essential principles of wavelet analysis, and then describe the main idea of embedded zerotree wavelet coding, used for compressing the SST images. The results show that this coding is adequate for the job. 相似文献
73.
E.A. Evstigneeva R.R. de Carvalho A.L. Ribeiro H.V. Capelato 《Astrophysics and Space Science》2003,284(2):487-490
We present the preliminary results of a study of how small stellar systems merge to form larger ones. As we display the families
of galaxies in the μe - Re plane (effective surface brightness versus effective radius) we realize that different morphological types occupy different
loci, evidencing the different physical mechanisms operating in each family. As proposed by Capaccioli et al. (1992) this
diagram is the logical equivalent of the HR diagram for stars. Here we take some initial steps in understanding of how we
can establish the evolutionary tracks, solely due to dynamical processes, in the μe - Re plane, ultimately making a dwarf elliptical to turn into a normal elliptical galaxy.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
74.
75.
76.
77.
78.
Observations of the brightness, color, and polarization of the fuor V1057 Cyg over more than 30 years are presented and briefly discussed. Variability of the linear polarization was found. 相似文献
79.
层序-岩相古地理图及其编制 总被引:24,自引:3,他引:21
在中国岩相古地理研究历史简要回顾基础上,以层序地层学理论为指导,就如何编制层序-岩相古地理图进行了讨论,首先是编图单元的选择,一是以层序内的体系域为成图单元,二是以相关界面为成图单元.具体方法是在对所研究的层位进行精细的层序地层分析的基础上,进行层序对比,建立等时地层格架.在上述基础上系统编制不同层序内的各体系域或有关界面沉积时的古地理图.以此方法所编制的层序-岩相古地理图具有重要的理论和现实意义,主要表现为更具有等时性、成因连续性和实用性,能更好地反映一个地区在统一地质作用场中的各种地质信息和综合效应;可以揭示出一些新的地质现象,对于覆盖区相带展布及变化具更合理的预测性.进而以中国南方二叠纪为例,在层序划分、对比的基础上,系统编制了一个完整的海平面变化旋回条件下的层序-岩相古地理图,并描述了其平面展布特点. 相似文献
80.
R. Surendiranath N. Kameswara Rao Ram Sagar J. S. Nathan K. K. Ghosh 《Journal of Astrophysics and Astronomy》1990,11(2):151-166
bdAbstract The open cluster NGC 2818 containing a planetary nebula has been observed inVRI bands using the CCD system at prime focus of the 2.3-metre Vainu Bappu Telescope. The study extending to starsV ∼ 21 magnitude establishes the distance modulus as(m-M)
0 = 12.9 ±0.1 for the cluster. Based on the fitting of theoretical isochrones computed for solar metallicity, an age of 5(±1)
× 108 years has been assigned to the cluster. Association of the planetary nebula with the cluster indicates that the progenitor
mass of the planetary nebula on the main sequence is ≥2.5M⊙
Based on observations obtained with the Vainu Bappu Telescope. 相似文献