全文获取类型
收费全文 | 9238篇 |
免费 | 480篇 |
国内免费 | 634篇 |
专业分类
测绘学 | 289篇 |
大气科学 | 950篇 |
地球物理 | 1952篇 |
地质学 | 3617篇 |
海洋学 | 768篇 |
天文学 | 1992篇 |
综合类 | 189篇 |
自然地理 | 595篇 |
出版年
2023年 | 67篇 |
2022年 | 117篇 |
2021年 | 129篇 |
2020年 | 126篇 |
2019年 | 131篇 |
2018年 | 324篇 |
2017年 | 285篇 |
2016年 | 365篇 |
2015年 | 238篇 |
2014年 | 364篇 |
2013年 | 499篇 |
2012年 | 307篇 |
2011年 | 475篇 |
2010年 | 375篇 |
2009年 | 532篇 |
2008年 | 414篇 |
2007年 | 394篇 |
2006年 | 384篇 |
2005年 | 347篇 |
2004年 | 342篇 |
2003年 | 312篇 |
2002年 | 289篇 |
2001年 | 259篇 |
2000年 | 254篇 |
1999年 | 252篇 |
1998年 | 220篇 |
1997年 | 218篇 |
1996年 | 214篇 |
1995年 | 184篇 |
1994年 | 163篇 |
1993年 | 128篇 |
1992年 | 106篇 |
1991年 | 115篇 |
1990年 | 101篇 |
1989年 | 111篇 |
1988年 | 75篇 |
1987年 | 109篇 |
1986年 | 78篇 |
1985年 | 77篇 |
1984年 | 74篇 |
1983年 | 78篇 |
1982年 | 75篇 |
1981年 | 74篇 |
1980年 | 55篇 |
1979年 | 51篇 |
1977年 | 49篇 |
1976年 | 50篇 |
1975年 | 35篇 |
1974年 | 31篇 |
1973年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
21.
Hui-Rong Ji Qi-Jun Pu Yi-Hua Yan Yu-Ying Liu Zhi-Jun Chen Cheng-Ming Tan Cong-Ling Cheng De-Bang Lao Shu-Ke Li Zhi-Qiang Wang Min-Hong Yu Jian-Nong Liu Li-Kang Zhang Ji-Yong Gao National Astronomical Observatories Chinese Academy of Sciences Beijing Hebei Semiconductor Research Institute Shijiazhuang 《中国天文和天体物理学报》2005,5(4):433-441
An improved Solar Radio Spectrometer working at 1.10-2.06 GHz with much improved spectral and temporal resolution, has been accomplished by the National Astronomical Observatories and Hebei Semiconductor Research Institute, based on an old spectrometer at 1-2 GHz. The new spectrometer has a spectral resolution of 4 MHz and a temporal resolution of 5ms, with an instantaneous detectable range from 0.02 to 10 times of the quiet Sun flux. It can measure both left and right circular polarization with an accuracy of 10% in degree of polarization. Some results of preliminary observations that could not be recorded by the old spectrometer at 1-2 GHz are presented. 相似文献
22.
The FAST/SKA site selection in Guizhou province 总被引:1,自引:0,他引:1
Many karst depressions with diameters of 300 m to 500 m, suitable for constructing Arecibo-style radio telescopes, were identified
in the south of Guizhou Province by Remote Sensing (RS) and Geographic Information System (GIS) technologies together with
field investigations. Fundamental topography and landform databases were established for 391candidate depressions, and using
GIS the3-dimensional images of depressions, at a scale of 1:10000, were then simulated to fit a spherical antenna.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
23.
Using the basic Boussinesq's equation, the expression for the vertical stress distribution (σz) underneath any point on the ground surface due to a general triangular loaded region in a preferred orientation with a linearly varied loading has been successfully derived. When the triangle is not in a preferred orientation, a simple axis transformation is required and the expression will be equally applicable. Based on this expression, σz due to an arbitrarily shaped loaded foundation can simply be determined by first triangulating the loaded area and summing up the contributions from each generated triangular region. The procedures for triangulating and calculating the stress distribution can be simply automated through computer programs. 相似文献
24.
I.A. Bond F. Abe R.J. Dodd J.B. Hearnshaw M. Honda J. Jugaku P.M. Kilmartin A. Marles K. Masuda Y. Matsubara Y. Muraki T. Nakamura G. Nankivell S. Noda C. Noguchi K. Ohnishi N.J. Rattenbury M. Reid To. Saito H. Sato M. Sekiguchi J. Skuljan D.J. Sullivan T. Sumi M. Takeuti Y. Watase S. Wilkinson R. Yamada T. Yanagisawa P.C.M. Yock 《Monthly notices of the Royal Astronomical Society》2001,327(3):868-880
We describe observations carried out by the MOA group of the Galactic bulge during 2000 that were designed to detect efficiently gravitational microlensing of faint stars in which the magnification is high and/or of short duration. These events are particularly useful for studies of extrasolar planets and faint stars. Approximately 17 deg2 were monitored at a sampling rate of up to six times per night. The images were analysed in real time using a difference imaging technique. 20 microlensing candidates were detected, of which eight were alerted to the microlensing community whilst in progress. Approximately half of the candidates had high magnifications (≳10), at least one had very high magnification (≳50), and one exhibited a clear parallax effect. The details of these events are reported here, together with details of the on-line difference imaging technique. Some nova-like events were also observed and these are described, together with one asteroid. 相似文献
25.
26.
使用中国科学院紫金山天文台青海站13.7米射电望远镜于1996年12月至1997年1月对富碳拱星IRC 10216和CIT6的CO J=1-0跃迁(115GHz)进行了观测。在观测谱线的基础上得到了IRC 10216的视向速度和膨胀速度分别为一26.1km s~(-1)和14.8km s~(-1),CIT6的视向速度和膨胀速度分别为0.6km s~(-1)和13.8kms~(-1)。并对望远镜的射束及指向精度进行了研究。 相似文献
27.
In this paper, two factors — the redistribution of the density and the variation in the angular velocity of the Earth rotation, that affect the adopted value of the flattening for equidensity surface within the Earth, are discussed. The computational results show that the contribution of the redistribution of the density in the Earth interior (especially in the core) on the change of the flattening at the core-mantle boundary (CMB) is marginal, and that the calculated value of the flattening at the CMB can be in good agreement with the VLBI observed value so long as the fact that the angular velocity of the Earth rotation has undergone the tidal evolution is taken into account. As a result, this paper presents a set of recommended values of the dynamical parameters of the Earth (see Table III) for computing Earth's forced nutation series. 相似文献
28.
This work deals with the possible solution of the solar neutrino problem in the framework of the resonant neutrino spin-flavor precession scenario. The event rate results from the solar neutrino experiments as well as the recoil electron energy spectrum from SuperKamiokande are used to constrain the free parameters of the neutrino in this model (Δm2 and μν). We consider two kinds of magnetic profiles inside the sun. For both cases, a static and a twisting field are discussed. 相似文献
29.
30.