全文获取类型
收费全文 | 5693篇 |
免费 | 1017篇 |
国内免费 | 1318篇 |
专业分类
测绘学 | 376篇 |
大气科学 | 1180篇 |
地球物理 | 1553篇 |
地质学 | 2729篇 |
海洋学 | 699篇 |
天文学 | 298篇 |
综合类 | 647篇 |
自然地理 | 546篇 |
出版年
2024年 | 36篇 |
2023年 | 107篇 |
2022年 | 253篇 |
2021年 | 293篇 |
2020年 | 236篇 |
2019年 | 264篇 |
2018年 | 293篇 |
2017年 | 267篇 |
2016年 | 338篇 |
2015年 | 297篇 |
2014年 | 349篇 |
2013年 | 307篇 |
2012年 | 288篇 |
2011年 | 322篇 |
2010年 | 298篇 |
2009年 | 358篇 |
2008年 | 325篇 |
2007年 | 301篇 |
2006年 | 222篇 |
2005年 | 243篇 |
2004年 | 171篇 |
2003年 | 168篇 |
2002年 | 183篇 |
2001年 | 182篇 |
2000年 | 181篇 |
1999年 | 251篇 |
1998年 | 226篇 |
1997年 | 181篇 |
1996年 | 200篇 |
1995年 | 147篇 |
1994年 | 146篇 |
1993年 | 152篇 |
1992年 | 123篇 |
1991年 | 68篇 |
1990年 | 56篇 |
1989年 | 48篇 |
1988年 | 41篇 |
1987年 | 21篇 |
1986年 | 26篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1958年 | 4篇 |
排序方式: 共有8028条查询结果,搜索用时 15 毫秒
101.
??LAMBDA????????GNSS????????????????????????????????????????????????????????????????????????Ratio??????????????????Ratio?????????????????????L1??L2?????λ????????????????????÷????????????????????????????????????????????????????????? 相似文献
102.
�봨����ǿ��۲� 总被引:1,自引:0,他引:1
????????????????;???????????????????????????????????????????????????????????????????????????? 相似文献
103.
Based on the sequence data of the nuclear ribosomal DNA internal transcribed spacer (ITS) 1, 5.8 S, and ITS 2, the molecular
phylogeny was analyzed on Ulvaceae species collected from Qingdao coasts in summer of 2007, including 15 attached Ulva and Enteromorpha samples from 10 locations and 10 free-floating Enteromorpha samples from seven locations. The result supported the monophyly of all free-floating Enteromorpha samples, implying the unialgal composition of the free-floating Enteromorpha, and the attached Ulvaceae species from Qingdao coasts were grouped into other five clades, suggesting that they were not
the biogeographic origin of the free-floating Enteromorpha in that season.
Supported by NSFC (40506030); the Innovative Key Project of the Chinese Academy of Sciences (KZCX2-YW-209); Science & Technology
Project of Qingdao City (06-2-2-12-JCH) 相似文献
104.
LIUJuan JIANGWensheng SUNWenxin WANGYongzhi 《中国海洋大学学报(英文版)》2005,4(2):108-114
In order to forecast storm surge inundation, a two-dimensional model is established. In the model, an alternating computation sequence method is used to solve the governing equations, and the dry and wet method is introduced to treat the moving boundary. This model is easy to use. It has a friendly input interface and Arcview GIS is used as the output interface. The model is applied to the Shantou area to simulate the storm surge elevations and inundations caused by Typhoons 6903 ane 0104 using the same relevant parameters. The calculated results agree well with the observations. 相似文献
105.
在第一代DZW-Ⅰ重力仪基础上,采用新的机电一体的数字智能化设计,研制出改进的DZW-Ⅱ型重力仪。介绍了DZW-Ⅱ型重力仪的基本原理,对仪器使用过程中出现的问题进行分析,改进和优化仪器设计,进一步提高了仪器的可靠性和稳定性。 相似文献
106.
THE CORRESPONDING ANALYSIS OF HEAVY-METAL POLLUTION OF SOIL IN ZHUZHOU CITY ShangJincheng(尚金城);LongAimin(龙爱民)LiBin(李斌);JiangJ... 相似文献
107.
Contribution to diffuse gamma-rays in the Galactic Centre region from unresolved millisecond pulsars
W. Wang Z. J. Jiang K. S. Cheng 《Monthly notices of the Royal Astronomical Society》2005,358(1):263-269
Diffuse gamma-rays in the Galactic Centre region have been studied. We propose that there exists a population of millisecond pulsars in the Galactic Centre, which emit GeV gamma-rays through synchrotron-curvature radiation as predicted by outer gap models. These GeV gamma-rays from unresolved millisecond pulsars probably contribute to the diffuse gamma-ray spectrum detected by EGRET which displays a break at a few GeV. We have used a Monte Carlo method to obtain simulated samples of millisecond pulsars in the Galactic Centre region covered by EGRET (∼ 15) according to the different period and magnetic field distributions from observed millisecond pulsars in the Galactic field and globular clusters, and superposed their synchrotron-curvature spectra to derive the total GeV flux. Our simulated results suggest that there probably exist about 6000 unresolved millisecond pulsars in the region of angular resolution of EGRET, the emissions of which could contribute significantly to the observed diffuse gamma-rays in the Galactic Centre. 相似文献
108.
Two primary solar-activity indicators sunspot numbers(SNs)and sunspot areas(SAs)in the time interval from November 1874 to December 2012 are used to determine the chaotic and fractal properties of solar activity.The results show that(1)the long-term solar activity is governed by a low-dimensional chaotic strange attractor,and its fractal motion shows a long-term persistence on large scales;(2)both the fractal dimension and maximal Lyapunov exponent of SAs are larger than those of SNs,implying that the dynamical system of SAs is more chaotic and complex than SNs;(3)the predictions of solar activity should only be done for short-to mid-term behaviors due to its intrinsic complexity;moreover,the predictability time of SAs is obviously smaller than that of SNs and previous results. 相似文献
109.
110.