全文获取类型
收费全文 | 63383篇 |
免费 | 8322篇 |
国内免费 | 11467篇 |
专业分类
测绘学 | 5626篇 |
大气科学 | 7126篇 |
地球物理 | 9036篇 |
地质学 | 25669篇 |
海洋学 | 6689篇 |
天文学 | 17917篇 |
综合类 | 3562篇 |
自然地理 | 7547篇 |
出版年
2024年 | 247篇 |
2023年 | 619篇 |
2022年 | 1678篇 |
2021年 | 1865篇 |
2020年 | 1953篇 |
2019年 | 2489篇 |
2018年 | 1718篇 |
2017年 | 2031篇 |
2016年 | 2048篇 |
2015年 | 2399篇 |
2014年 | 2806篇 |
2013年 | 2965篇 |
2012年 | 3108篇 |
2011年 | 3157篇 |
2010年 | 2778篇 |
2009年 | 4445篇 |
2008年 | 4409篇 |
2007年 | 4856篇 |
2006年 | 4841篇 |
2005年 | 4421篇 |
2004年 | 4111篇 |
2003年 | 3693篇 |
2002年 | 3243篇 |
2001年 | 2767篇 |
2000年 | 2615篇 |
1999年 | 2354篇 |
1998年 | 2317篇 |
1997年 | 1245篇 |
1996年 | 964篇 |
1995年 | 946篇 |
1994年 | 926篇 |
1993年 | 692篇 |
1992年 | 510篇 |
1991年 | 424篇 |
1990年 | 305篇 |
1989年 | 336篇 |
1988年 | 239篇 |
1987年 | 174篇 |
1986年 | 140篇 |
1985年 | 91篇 |
1984年 | 55篇 |
1983年 | 47篇 |
1982年 | 23篇 |
1981年 | 18篇 |
1980年 | 13篇 |
1979年 | 9篇 |
1978年 | 16篇 |
1977年 | 12篇 |
1954年 | 11篇 |
1897年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 942 毫秒
361.
362.
363.
Tao Kiang Yong-Feng Wu Xing-Fen Zhu Dunsink Observatory Dublin Institute for Advanced Studies Dublin Ireland Center for Astrophysics University of Science Technology of China Hefei 《中国天文和天体物理学报》2004,4(3):209-220
Rhombic cell analysis as outlined in the first paper of the present seriesis applied to samples of varying depths and liming luminosities of the IRAS/PSCzCatalogue. Numerical indices are introduced to summarize essential information.Because of the discrete nature of the analysis and of the space distribution of galax-ies, the indices for a given sample must be regarded as each having an irreduciblescatter. Despite the scatter, the mean indices show remarkable variations acrossthe samples. The underlying factor for the variations is shown to be the limitingluminosity rather than the sampling depth. As samples of more and more luminousgalaxies are considered over a range of some 2.5 magnitudes (a factor of some 75in space density), the morphology of the filled and empty regions defined by thegalaxies degrades steadily towards insignificance, and the degrading is faster for thefilled than the empty region. 相似文献
364.
365.
366.
Yanjun ZHANG Fenglong ZHANG Full QI Fuquan NI 《东北亚地学研究》2006,9(2):199-203
In view of the situation of excavation of open coal mine for the underground water disaster,we should carry out simulation studies for the numerical value of the water lowering project and improve the accuracy and the level of the water lowering project.On the basis of the hydrological geological conditions of certain open mine digging,a more reasonable seepage numerical model was built according to MODFLOW.It was simulated in advance that the process of the confined water level descending with the time,and combining with the actual observations to test the correctness of the model.The calculation showed that the results coincided well with the results of actual measurement.Based on this,different water lowering numerical simulations were built for the open coal mine digging.It could be simulated and forecast that the changes of the groundwater level in drainage process within and outside the mine pit,and it was quantitatively assessed that the possible water lowering result of the opencast water drainage process,which provide an important basis for the actual water lowering project and the possible project disposal. 相似文献
367.
Blazars are the only (with one or two exceptions) extragalactic objects which were detected and identified at gamma-ray energies
so far. It is suspected that most of the unidentified gamma-ray sources may be the blazars as well. Because the entire electromagnetic
spectrum of these objects is dominated by non-thermal radiation from relativistically moving jets, the effects such as the
Klein–Nishina regime in the Compton scattering may play a major role in shaping some parts of the blazar spectrum. Within
the framework of external radiation Compton model, we present how these effect influence the spectra of blazars for which
the production of gamma rays is dominated by Comptonization of external radiation. 相似文献
368.
We investigate the evolution of rotation period and spindown age of a pulsar whose surface magnetic field undergoes a phase
of growth. Application of these results to the Crab pulsar strongly indicates that its parameters cannot be accounted for
by the field growth theories. 相似文献
369.
Sunetra Giridhar N. Kameswara Rao David L. Lambert 《Journal of Astrophysics and Astronomy》1996,17(1-2):23-40
Two high resolution spectra of the hot RCrB star DY Cen in the red region are compared. The photospheric absorption lines
show a radial velocity variation of 12 kms-1 between 1989 July and 1992 May. Emission components to some CII lines present
in 1989 are almost entirely absent in 1992. Nebular forbidden lines of [OI], [NII] and [SII] appear unchanged from 1989 to
1992 相似文献
370.