全文获取类型
收费全文 | 2360篇 |
免费 | 517篇 |
国内免费 | 669篇 |
专业分类
测绘学 | 279篇 |
大气科学 | 478篇 |
地球物理 | 518篇 |
地质学 | 1396篇 |
海洋学 | 276篇 |
天文学 | 115篇 |
综合类 | 154篇 |
自然地理 | 330篇 |
出版年
2024年 | 12篇 |
2023年 | 37篇 |
2022年 | 96篇 |
2021年 | 112篇 |
2020年 | 90篇 |
2019年 | 124篇 |
2018年 | 127篇 |
2017年 | 122篇 |
2016年 | 140篇 |
2015年 | 131篇 |
2014年 | 124篇 |
2013年 | 164篇 |
2012年 | 173篇 |
2011年 | 129篇 |
2010年 | 147篇 |
2009年 | 130篇 |
2008年 | 115篇 |
2007年 | 105篇 |
2006年 | 119篇 |
2005年 | 107篇 |
2004年 | 116篇 |
2003年 | 145篇 |
2002年 | 258篇 |
2001年 | 225篇 |
2000年 | 103篇 |
1999年 | 88篇 |
1998年 | 39篇 |
1997年 | 63篇 |
1996年 | 43篇 |
1995年 | 29篇 |
1994年 | 29篇 |
1993年 | 16篇 |
1992年 | 10篇 |
1991年 | 19篇 |
1990年 | 12篇 |
1989年 | 9篇 |
1988年 | 13篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 6篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1958年 | 1篇 |
1954年 | 2篇 |
排序方式: 共有3546条查询结果,搜索用时 218 毫秒
1.
Zhi Xu Cheng Fang Wei-Qun Can Astronomy Department of Nanjing University Nanjing Purple Mountain Observatory Chinese Academy of Sciences Nanjing 《中国天文和天体物理学报》2005,5(5):519-530
Chromospheric lines, including Ha, Lyα, Lyβand CaⅡK, CaⅡ8542, are systemically and quantitatively investigated with respect to the non-thermal excitation and ionization due to particle beam bombardment for a series of solar semi-empirical atmospheric models. As a result we propose to use the contrast in the integrated intensity of hydrogen lines to estimate the total energy flux of the bombarding beam during the solar flare impulsive phase. Partial frequency redistribution is considered in the Lyαline calculation and a smaller intensity enhancement in the Ha line-centers is found than in the previous results of Fang et al. 相似文献
2.
Brine shrimp (Artemia parthenogenetica) which had ingested three water-insoluble antibacterial drugs i.e. sulfadiazine(SD), oxytetracycline (OTC) and erythromycin
estolate (ERY-Es) were fed toTilapia and Mysis IIIof Penaeus orientalis K. The drug contents in the predators were then determined. After administration of drugs toTilapia and Mysis III, through the bio-encapsulation of the brine shrimp, efficacious therapeutical concentration of OTC and ERY-Es
(but not SD) in the predators could be reached and maintained for more than 8 hours. 相似文献
3.
Wei-Hao Bian Quan-Ling Cui Li-Hua Chao Department of Physics Institute of Theoretical Physics Nanjing Normal University Nanjing Key Laboratory for Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2006,6(3):281-286
We used multi-component profiles to model the Hβ and [OⅢ]λλ4959,5007 lines of SDSS J143030.22-001115.1, a narrow-line Seyfert 1 galaxy (NLS1) in a sample of 150 NLS1 candidates selected from the Sloan Digital Sky Survey (SDSS), Early Data Release (EDR). After subtracting the Hβ contribution from narrow line regions (NLRs), we found that its full width half maximum (FWHM) of broad Hβ line is nearly 2900km s~(-1) , significantly larger than the customarily adopted criterion of 2000 km s~(-1) . With its weak Fe Ⅱ multiples, we believe that SDSS J143030.22-001115.1 should not be classified as a genuine NLS1. When we calculate the virial black hole masses of NLS1s, we should use the Hβ linewidth after subtracting the NLR component. 相似文献
4.
本文讨论了彗星中尘埃粒子的充电机制 ,带电特性和平衡电势的变化规律 ,分析了彗星尘埃的破碎特性和临界半径 ,得出了很有意义的结果 相似文献
5.
1 INTRODUCTIONIn the previous paper (on et al. 1999, hereafter Paper I), we investigated the wavelength-dependence of four colltribution functions (CFs) derived from dmerent formal solutions andreferring to different emergellt quantities in the unpolarized case. Because one cannot generallyassign a single formation region to the whole line band in a real stellar atmosphere, e.g., the solaratmosphere, instead, the line formation region can be defined as the layers deviating farthestfrom t… 相似文献
6.
本文叙述南天区 5GHzVLBI普查中新发现的视超光速射电源 ,0 4 2 0— 0 1 4,1 334—1 2 7和 2 345— 1 67,这些结果尚待进一步的观测加以证实 相似文献
7.
Based on the Germany Koldwey Station's 1994-2003 conventional observation hourly data, this paper conducts a statistical analysis on the short-term climate characteristics for an arctic tundra region (Ny-(A)lesund island) where our first arctic expedition station (Huanghe Station) was located. Affected by the North Atlantic warming current, this area has a humid temperate climate, and the air temperature at Ny-(A)lesund rose above 0 ℃ even during deep winter season during our research period. The wind speed in this area was low and appeared most at southeast direction. We find that the temperature at Ny-(A)lesund rose in the faster rate (0.68 ℃/10 a) than those at the whole Arctic area. Compared with the floating ices where our expedition conducted in the Arctic, Ny-(A)lesund was warmer and more humid and had lower wind speed. Comparison of the near surface air temperature derived by NCEP/NCAR reanalysis to the conventional measurements conducted at the Koldwey site in Ny-(A)lesund area shows a good agreement for winter season and a significant difference for summer season. 相似文献
8.
数字图像压缩方法在天文上的应用 总被引:1,自引:0,他引:1
概述了数字图像压缩技术在天文领域应用的必要性。针对天文观测的特点和研究的需要,经过研究、分析和比较,提出了天文图像压缩的可行方案。通过应用计算机编程及压缩实验并给出相应的结果。 相似文献
9.
介绍了一种新颖的静态传感器网络实现方法,它利用可移动的中继节点来收集静态传感器网络的数据,有效的节约各传感器节点的能源,延长整个传感器网络的有效工作时间。也可以对该方法进行适当的改进,应用到某些实时性要求较高的场合中去。然后介绍了应用该原理实现的一个通讯协议。 相似文献
10.
卞菊梅 《地球科学与环境学报》1995,(1)
本文主要依据地形图和航空照片解译,并经已有地质、钻孔资料验证及野外实地考察的方法来研究地形面及其变形特征,由此确定渭河盆地活断层的分布、最新活动特征及活动规律,为地震预报及地震危险性分析提供依据。 相似文献