全文获取类型
收费全文 | 658篇 |
免费 | 45篇 |
国内免费 | 82篇 |
专业分类
测绘学 | 84篇 |
大气科学 | 204篇 |
地球物理 | 35篇 |
地质学 | 10篇 |
海洋学 | 11篇 |
天文学 | 410篇 |
综合类 | 21篇 |
自然地理 | 10篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 12篇 |
2021年 | 18篇 |
2020年 | 16篇 |
2019年 | 19篇 |
2018年 | 9篇 |
2017年 | 18篇 |
2016年 | 14篇 |
2015年 | 19篇 |
2014年 | 23篇 |
2013年 | 29篇 |
2012年 | 22篇 |
2011年 | 22篇 |
2010年 | 15篇 |
2009年 | 47篇 |
2008年 | 32篇 |
2007年 | 48篇 |
2006年 | 52篇 |
2005年 | 57篇 |
2004年 | 42篇 |
2003年 | 40篇 |
2002年 | 33篇 |
2001年 | 35篇 |
2000年 | 34篇 |
1999年 | 28篇 |
1998年 | 33篇 |
1997年 | 1篇 |
1996年 | 8篇 |
1995年 | 13篇 |
1994年 | 15篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1985年 | 3篇 |
1980年 | 4篇 |
1978年 | 2篇 |
排序方式: 共有785条查询结果,搜索用时 672 毫秒
511.
512.
J. S.Lazendic † M.Wardle M. G.Burton F.Yusef-Zadeh J. B.Whiteoak A. J.Green M. C. B.Ashley 《Monthly notices of the Royal Astronomical Society》2002,331(2):537-544
We have found a bar of shocked molecular hydrogen (H2 ) towards the OH(1720 MHz) maser located at the projected intersection of supernova remnant (SNR) G359.1–0.5 and the non-thermal radio filament known as the Snake. The H2 bar is well aligned with the SNR shell and almost perpendicular to the Snake. The OH(1720 MHz) maser is located inside the sharp western edge of the H2 emission, which is consistent with the scenario in which the SNR drives a shock into a molecular cloud at that location. The spectral line profiles of 12 CO, HCO+ and CS towards the maser show broad-line absorption, which is absent in the 13 CO spectra and most probably originates from the pre-shock gas. A density gradient is present across the region and is consistent with the passage of the SNR shock, while the H2 filament is located at the boundary between the pre-shock and post-shock regions. 相似文献
513.
514.
C. Codella R. Bachiller M. Benedettini P. Caselli 《Monthly notices of the Royal Astronomical Society》2003,341(2):707-716
The Cepheus A star-forming region has been investigated through a multiline H2 S and SO2 survey at millimetre wavelengths. Large-scale maps and high-resolution line profiles reveal the occurrence of several outflows. Cep A East is associated with multiple mass-loss processes: in particular, we detect a 0.6-pc jet-like structure which shows for the first time that the Cep A East young stellar objects are driving a collimated outflow moving towards the south.
The observed outflows show different clumps associated with definitely different H2 S/SO2 integrated emission ratios, indicating that the gas chemistry in Cepheus A has been altered by the passage of shocks. H2 S appears to be more abundant than SO2 in high-velocity clumps, in agreement with chemical models. However, we also find quite small H2 S linewidths, suggestive of regions where the evaporated H2 S molecules had enough time to slow down but not to freeze out on to dust grains. Finally, comparison between the line profiles indicates that the excitation conditions increase with the velocity, as expected for a propagation of collimated bow shocks. 相似文献
The observed outflows show different clumps associated with definitely different H
515.
C. del Burgo R. J. Laureijs P. Ábrahám Cs. Kiss 《Monthly notices of the Royal Astronomical Society》2003,346(2):403-414
We present ISOPHOT observations of eight interstellar regions in the 60–200 μm wavelength range. The regions belong to mostly quiescent high-latitude clouds and have optical extinction peaks from AV ∼1–6 mag . From the 150- and 200-μm emission, we derived colour temperatures for the classical big grain component which show a clear trend of decreasing temperature with increasing 200-μm emission. The 200-μm emission per unit AV , however, does not drop at lower temperatures. This fact can be interpreted in terms of an increased far-infrared (FIR) emissivity of the big grains. We developed a two-component model including warm dust with the temperature of the diffuse interstellar medium (ISM) of T = 17.5 K , and cold dust with T = 13.5 K and FIR emissivity increased by a factor of >4. A mixture of the two components can reproduce the observed colour variations and the ratios I 200 / AV and τ200 / AV . The relative abundance of small grains with respect to the big grains shows significant variations from region to region at low column densities. However, in lines of sight of higher column density, our data indicate the disappearance of small grains, perhaps a signature of adsorption/coagulation of dust. The larger size and porous structure could also explain the increased FIR emissivity. Our results from eight independent regions suggest that these grains might be ubiquitous in the galactic ISM. 相似文献
516.
517.
518.
A mechanism for interstellar panspermia 总被引:2,自引:0,他引:2
W. M. Napier † 《Monthly notices of the Royal Astronomical Society》2004,348(1):46-51
519.
R. Zylka 《Astrophysics and Space Science》1995,224(1-2):189-198
I summarize recent millimetre and submillimetre observations of cloud cores where massive star formation is currently taking place. The first systematic continuum surveys in this wavelength range obtained with single dish telescopes and high-resolution data of NGC 2024 and W51A obtained with the Plateau de Bure interferometer are presented in more detail. Also given is a discussion of observing methods and some of the difficulties involved with the observations. 相似文献
520.
一种基于LiDAR点云栅格化的海岸线提取方法 总被引:1,自引:0,他引:1
针对当前从三维激光点云中提取海岸线方法的不足,提出了一种基于点云栅格化的海岸线提取方法。首先对点云进行去噪等数据预处理,然后直接将其栅格化生成更为平滑的海岸地形,最后采用中国近海海域潮汐精密模型,从栅格海岸地形中提取基于平均大潮高潮面MHWS(Mean High Water Springs)海岸线。实验表明:此处所提出的点云栅格化方法较当前方法提取的海岸线更可靠、合理,提取效率更高,同时也可用于其他辅助岸线的提取。 相似文献