全文获取类型
| 收费全文 | 13489篇 |
| 免费 | 2678篇 |
| 国内免费 | 2504篇 |
专业分类
| 测绘学 | 598篇 |
| 大气科学 | 1002篇 |
| 地球物理 | 3914篇 |
| 地质学 | 6385篇 |
| 海洋学 | 1859篇 |
| 天文学 | 2011篇 |
| 综合类 | 690篇 |
| 自然地理 | 2212篇 |
出版年
| 2024年 | 35篇 |
| 2023年 | 150篇 |
| 2022年 | 389篇 |
| 2021年 | 427篇 |
| 2020年 | 476篇 |
| 2019年 | 541篇 |
| 2018年 | 476篇 |
| 2017年 | 485篇 |
| 2016年 | 511篇 |
| 2015年 | 559篇 |
| 2014年 | 664篇 |
| 2013年 | 614篇 |
| 2012年 | 728篇 |
| 2011年 | 794篇 |
| 2010年 | 645篇 |
| 2009年 | 958篇 |
| 2008年 | 879篇 |
| 2007年 | 946篇 |
| 2006年 | 938篇 |
| 2005年 | 816篇 |
| 2004年 | 813篇 |
| 2003年 | 819篇 |
| 2002年 | 641篇 |
| 2001年 | 605篇 |
| 2000年 | 578篇 |
| 1999年 | 505篇 |
| 1998年 | 565篇 |
| 1997年 | 327篇 |
| 1996年 | 293篇 |
| 1995年 | 290篇 |
| 1994年 | 260篇 |
| 1993年 | 224篇 |
| 1992年 | 189篇 |
| 1991年 | 117篇 |
| 1990年 | 79篇 |
| 1989年 | 82篇 |
| 1988年 | 56篇 |
| 1987年 | 66篇 |
| 1986年 | 39篇 |
| 1985年 | 20篇 |
| 1984年 | 6篇 |
| 1983年 | 5篇 |
| 1982年 | 4篇 |
| 1981年 | 5篇 |
| 1980年 | 7篇 |
| 1979年 | 10篇 |
| 1978年 | 4篇 |
| 1977年 | 5篇 |
| 1976年 | 5篇 |
| 1954年 | 14篇 |
排序方式： 共有10000条查询结果，搜索用时 62 毫秒
61.
62.
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
63.
通过杂质对导电类型的影响的研究,得出了同种矿物的不同导电类型与矿物形成温度的规律:电子型(n型)导电矿物的形成温度大于电子与空穴混合型导电矿物的形成温度,又大于空穴型(p型)导电矿物的形成温度,绝缘体矿物的形成温度低于上述三种导电类型矿物。应用矿物热电图谱仪,天然金刚石半导体测试仪对闪锌矿、黄铁矿、金刚石等矿物的导电类型进行了测试,并探讨了导电类型成因,证实了上述规律的正确性。 相似文献
64.
65.
We briefly describe an advanced 3D gas dynamical model developed for the simulation of theenvironment of active cometary nuclei.
The model canhandle realistic nucleus shapes and alternative physical models for the gas and dust production mechanism.The
inner gas coma structure is computed by solving self-consistently(a) near to the surface the Boltzman Equation(b) outside
of it, Euler or Navier-Stokes equations.The dust distribution is computed from multifluid ``zero-temperature' Euler equations,extrapolated
with the help of a Keplerian fountain model.The evolution of the coma during the nucleus orbital and spin motion,is computed
as a succession of quasi-steady solutions. Earlier versions of the model using simple,``paedagogic' nuclei have demonstrated
that the surface orographyand the surface inhomogeneity contribute similarly to structuring the near-nucleusgas and dust coma,casting
a shadow on the automatic attribution of such structures to ``active areas'.The model was recently applied to comet P/Halley,
for whichthe nucleus shape is available. In the companion paper of this volume,we show that most near-nucleus dust structuresobserved
during the 1986 Halley flybys are reproduced, assuming that the nucleus is strictly homogeneous. Here, we investigate the
effect of shape perturbations and homogeneityperturbations. We show that the near nucleus gas coma structure is robust vis-a-vissuch
effects. In particular, a random distribution of active and inactive areaswould not affect considerably this structure, suggesting that such areas,even if present, could not be easily identified on images
of the coma. 相似文献
66.
67.
68.
69.
70.