全文获取类型
收费全文 | 22461篇 |
免费 | 3820篇 |
国内免费 | 5626篇 |
专业分类
测绘学 | 4844篇 |
大气科学 | 3627篇 |
地球物理 | 4803篇 |
地质学 | 9147篇 |
海洋学 | 3531篇 |
天文学 | 1646篇 |
综合类 | 1900篇 |
自然地理 | 2409篇 |
出版年
2024年 | 56篇 |
2023年 | 252篇 |
2022年 | 790篇 |
2021年 | 911篇 |
2020年 | 1089篇 |
2019年 | 1052篇 |
2018年 | 930篇 |
2017年 | 1204篇 |
2016年 | 1173篇 |
2015年 | 1307篇 |
2014年 | 1387篇 |
2013年 | 1609篇 |
2012年 | 1524篇 |
2011年 | 1507篇 |
2010年 | 1212篇 |
2009年 | 1402篇 |
2008年 | 1555篇 |
2007年 | 1691篇 |
2006年 | 1659篇 |
2005年 | 1469篇 |
2004年 | 1244篇 |
2003年 | 977篇 |
2002年 | 939篇 |
2001年 | 681篇 |
2000年 | 787篇 |
1999年 | 721篇 |
1998年 | 577篇 |
1997年 | 418篇 |
1996年 | 330篇 |
1995年 | 266篇 |
1994年 | 244篇 |
1993年 | 233篇 |
1992年 | 189篇 |
1991年 | 121篇 |
1990年 | 80篇 |
1989年 | 89篇 |
1988年 | 62篇 |
1987年 | 41篇 |
1986年 | 41篇 |
1985年 | 18篇 |
1984年 | 13篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1977年 | 3篇 |
1971年 | 2篇 |
1954年 | 11篇 |
1900年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
In recent years,scholars at home and abroad have method,and that vanous disasters would be analyzed assynthetically studied natural dlsaste‘theoretically and an Integral.SHI Peilun(1991)putforwad a scientificmethodologlcally,as well as its cases analys。s(CND,term—regional disaster system,which Indicates that1987; MA et al,1990; MARBLE,1990; NE et al,the situation of a disaster(calamity loss)results from1999; PATAK et al,1982; SHI,1991;VAN et al,h… 相似文献
62.
R. N. Ogley † S. J. Bell Burnell R. P. Fender 《Monthly notices of the Royal Astronomical Society》2001,322(1):177-186
We have observed the energetic binary Cygnus X-3 in both quiescent and flaring states between 4 and 16 μm using the ISO satellite. We find that the quiescent source shows the thermal free–free spectrum typical of a hot, fast stellar wind, such as from a massive helium star. The quiescent mass-loss rate arising from a spherically symmetric, non-accelerating wind is found to be in the range (0.4–2.9)×10−4 M⊙ yr−1 , consistent with other infrared and radio observations, but considerably larger than the 10−5 M⊙ yr−1 deduced from both the orbital change and the X-ray column density. There is rapid, large-amplitude flaring at 4.5 and 11.5 μm at the same time as enhanced radio and X-ray activity, with the infrared spectrum apparently becoming flatter in the flaring state. We believe that non-thermal processes are operating, perhaps along with enhanced thermal emission. 相似文献
63.
M. J. Carson J. C. Davies E. Daw R. J. Hollingworth V. A. Kudryavtsev T. B. Lawson P. K. Lightfoot J. E. McMillan B. Morgan S. M. Paling M. Robinson N. J. C. Spooner D. R. Tovey 《Astroparticle Physics》2004,21(6):667-687
Simulations of the neutron background for future large-scale particle dark matter detectors are presented. Neutrons were generated in rock and detector elements via spontaneous fission and (α,n) reactions, and by cosmic-ray muons. The simulation techniques and results are discussed in the context of the expected sensitivity of a generic liquid xenon dark matter detector. Methods of neutron background suppression are investigated. A sensitivity of 10−9–10−10 pb to WIMP-nucleon interactions can be achieved by a tonne-scale detector. 相似文献
64.
1 INTRODUCTIONThe South China Sea (SCS) is a semi-enclosedmarginal sea in western North Pacific Ocean withvery complex topography and is the important pas-sage connecting the Pacific and Indian Oceans. Ithas great impact to the global climate and a greatinterest of many oceanography researchers. Twodominant surface hydrographic and circulation fea-tures in the northern SCS are a strong fresh waterexpansion and a warm and high-salinity seawaterintrusion such as the SCS Diluted Water… 相似文献
65.
66.
67.
Randall D. Campbell 《Experimental Astronomy》2002,14(1):57-60
Keck's Long Wavelength Spectrometer (LWS), is the facility instrument used for imaging and spectroscopy in the wavelength
range of 3–28 μm at the Keck Observatory. LWS uses an 128 × 128 Si:As blocked impurity band (BIB) array manufactured by the
Boeing Corporation. This paper discusses the method used for optimizing the detector's operating parameters at a temperature
of 8.5 K and bias voltage of 1.2 V. A process for characterizing detective quantum efficiency of BIB detectors is also presented.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
68.
WANG Yachun 《东北亚地学研究》2002,(1)
The paper deals with the methods of formation pressure evaluation for a single well by using the very common ac-cepted parameters, such as drilling exponent , and flowline temperature , etc. which is part of compiling the end well report. 相似文献
69.
Dr M. J. Wooller D. L. Swain K. J. Ficken A. D. Q. Agnew F. A. Street-Perrott G. Eglinton 《第四纪科学杂志》2003,18(1):3-15
Woody, subalpine shrubs and grasses currently surround Lake Rutundu, Mount Kenya. Multiple proxies, including carbon isotopes, pollen and grass cuticles, from a 755‐cm‐long core were used to reconstruct the vegetation over the past 38 300 calendar years. Stable carbon‐isotope ratios of total organic carbon and terrestrial biomarkers from the lake sediments imply that the proportion of terrestrial plants using the C4 photosynthetic pathway was greater during the Late Pleistocene than in the Holocene. Pollen data show that grasses were a major constituent of the vegetation throughout the Late Pleistocene and Holocene. The proportion of grass pollen relative to the pollen from other plants was greatest at the last glacial maximum (LGM). Grass cuticles confirm evidence that C4 grass taxa were present at the LGM and that the majority followed the cold‐tolerant NADP‐MEC4 subpathway. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
70.