全文获取类型
收费全文 | 78332篇 |
免费 | 11679篇 |
国内免费 | 15557篇 |
专业分类
测绘学 | 13418篇 |
大气科学 | 9634篇 |
地球物理 | 11925篇 |
地质学 | 36810篇 |
海洋学 | 9246篇 |
天文学 | 4902篇 |
综合类 | 6356篇 |
自然地理 | 13277篇 |
出版年
2024年 | 263篇 |
2023年 | 820篇 |
2022年 | 2258篇 |
2021年 | 2741篇 |
2020年 | 2723篇 |
2019年 | 3373篇 |
2018年 | 2437篇 |
2017年 | 3205篇 |
2016年 | 3122篇 |
2015年 | 3572篇 |
2014年 | 4271篇 |
2013年 | 4790篇 |
2012年 | 4780篇 |
2011年 | 4980篇 |
2010年 | 4249篇 |
2009年 | 4978篇 |
2008年 | 5139篇 |
2007年 | 5606篇 |
2006年 | 5477篇 |
2005年 | 5023篇 |
2004年 | 4475篇 |
2003年 | 4001篇 |
2002年 | 3600篇 |
2001年 | 3040篇 |
2000年 | 2953篇 |
1999年 | 2564篇 |
1998年 | 2216篇 |
1997年 | 1666篇 |
1996年 | 1429篇 |
1995年 | 1178篇 |
1994年 | 1096篇 |
1993年 | 890篇 |
1992年 | 658篇 |
1991年 | 533篇 |
1990年 | 356篇 |
1989年 | 325篇 |
1988年 | 233篇 |
1987年 | 158篇 |
1986年 | 113篇 |
1985年 | 70篇 |
1984年 | 42篇 |
1983年 | 25篇 |
1982年 | 27篇 |
1981年 | 15篇 |
1980年 | 12篇 |
1979年 | 9篇 |
1978年 | 20篇 |
1977年 | 9篇 |
1971年 | 4篇 |
1954年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 968 毫秒
81.
A. V. Bogomolov A. P. Ignat’ev K. Kudela S. N. Kuznetsov Yu. I. Logachev O. V. Morozov I. N. Myagkova S. N. Oparin A. A. Pertsov S. I. Svertilov B. Yu. Yushkov 《Astronomy Letters》2003,29(3):199-204
We consider temporal, spectral, and polarization parameters of the hard X-ray and gamma-ray radiation observed during the solar flare of May 20, 2002, in the course of experiments with the SONG and SPR-N instruments onboard the Coronas-F spacecraft. This flare is one of the most intense gamma-ray events among all of the bursts of solar hard electromagnetic radiation detected since the beginning of the Coronas-F operation (since July 31, 2001) and one of the few gamma-ray events observed during solar cycle 23. A simultaneous analysis of the Coronas-F and GOES data on solar thermal X-ray radiation suggests that, apart from heating due to currents of matter in the the flare region, impulsive heating due to the injection of energetic electrons took place during the near-limb flare S21E65 of May 20, 2002. These electrons produced intense hard X-ray and gamma-ray radiation. The spectrum of this radiation extends up to energies ≥7 MeV. Intense gamma-ray lines are virtually unobservable against the background of the nonthermal continuum. The polarization of the hard X-ray (20–100 keV) radiation was estimated to be ≤15–20%. No significant increase in the flux of energetic protons from the flare under consideration was found. At the same time, according to ACE data, the fluxes of energetic electrons in interplanetary space increased shortly (~25 min) after the flare. 相似文献
82.
83.
The dunes in estuary of Tumen River in China lie to the area between the Jiushaping and Fangchuan in the left bank of Tumen River (Fig.1). The dis-tance is about 15~20 km between the dunes and the coast. It ranges from China to D. P. R. Korea and Russia. The range of the height of dunes is about 15~20 m and the width is 100~200 m. By the re-connaissance, we protracted 9 section planes of the dunes and collected 40 sand samples of the dunes, and identified the sedimentary environment … 相似文献
84.
Larisa A. Yakovina Yakiv V. Pavlenko Carlos Abia 《Astrophysics and Space Science》2003,288(3):279-286
Lithium abundances in the atmospheres of the super Li-rich C-giants WZ Cas and WX Cyg are derived by the spectral synthesis
technique using the Li I resonance line at λ670.8 nm and three subordinate lines at λλ 812.6, 610.4 and 497.2 nm. The differences
between the Li abundances derived from the λ670.8 nm line and the λλ 497.2, 812.6 nm lines do not exceed ±0.5 dex. The lithium
line at λ610.4 nm provides typically lower abundances than the resonance line (by ≈ 1 dex). The mean LTE and NLTE Li abundances
from three Li I lines (excluding λ610.4 nm) are 4.7, 4.9 for WZ Cas, and 4.6, 4.8 for WX Cyg, respectively.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
85.
杨吉 《地球科学与环境学报》2003,25(3):16-20
北秦岭侵入岩带中的中酸性侵入岩主要形成于晋宁旋回的中晚期阶段。主要岩石类型包括辉石闪长岩、闪长岩、石英闪长岩、英云闪长岩、花岗闪长岩、斜长花岗岩、花岗岩和钾长花岗岩。岩石化学、稀土元素和微量元素地球化学研究证明,这些岩石主要形成于B型俯冲和碰撞造山的构造环境中,而钾长花岗岩形成于后造山的伸展阶段。据此,该侵入岩带揭示了北秦岭褶皱带在晋宁旋回中晚期阶段的演化过程。 相似文献
86.
韩玲 《地球科学与环境学报》2003,25(1):74-75
提出了一种基于格网DEM的粗差检测及剔除方法,其基本思想是对每个表面上的点,在坡度上,高程或突变量引起的形状不连续,可能被怀疑有误差,通过坡度上每个点,应用坡度逼近或改变量来计算,考虑坡度变化的相对值,并以这些相对值计算一个统计值为判断该点合法性的阈值,使计算结果更为可靠。 相似文献
87.
Radiative Transfer (RT) codes with image capability are a fundamental tool for preparing interferometric observations and
for interpreting visibility data. In view of the upcoming VLTI facilities, we present the first comparison of images/visibilities
coming from two 3D codes that use completely different techniques to solve the problem of self-consistent continuum RT. In
addition, we focus on the astrophysical case of a disk distorted by tidal interaction with by-passing stars or internal planets
and investigate for which parameters the distortion can be best detected in the mid-infrared using the mid-infrared interferometric
device MIDI.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
88.
89.
90.
Pco2 of air and seawater samples from the East China Sea(ECS) were measured in situ in autumn, 1994,Ocean currents,terrestrial fluviation,biological activities,etc.,Pco2 char-acters in air and seawater were investigated,CO2 flux and its character in the East China Sea are discussed on the basis of the Pco2 profiles of air and seawater,It was clear that the nearshore was the source of CO2;and tht the oulter sea area was the sink of CO2; and that the shelf area of the EXS is a net sink for atmospheric CO2 in autumn. 相似文献