全文获取类型
收费全文 | 82722篇 |
免费 | 1800篇 |
国内免费 | 1536篇 |
专业分类
测绘学 | 2230篇 |
大气科学 | 6138篇 |
地球物理 | 16101篇 |
地质学 | 30136篇 |
海洋学 | 7533篇 |
天文学 | 18898篇 |
综合类 | 408篇 |
自然地理 | 4614篇 |
出版年
2022年 | 597篇 |
2021年 | 973篇 |
2020年 | 1009篇 |
2019年 | 1079篇 |
2018年 | 2233篇 |
2017年 | 2145篇 |
2016年 | 2641篇 |
2015年 | 1532篇 |
2014年 | 2553篇 |
2013年 | 4346篇 |
2012年 | 2869篇 |
2011年 | 3734篇 |
2010年 | 3267篇 |
2009年 | 4185篇 |
2008年 | 3588篇 |
2007年 | 3648篇 |
2006年 | 3501篇 |
2005年 | 2584篇 |
2004年 | 2503篇 |
2003年 | 2354篇 |
2002年 | 2268篇 |
2001年 | 1945篇 |
2000年 | 1862篇 |
1999年 | 1517篇 |
1998年 | 1599篇 |
1997年 | 1488篇 |
1996年 | 1290篇 |
1995年 | 1254篇 |
1994年 | 1073篇 |
1993年 | 960篇 |
1992年 | 946篇 |
1991年 | 921篇 |
1990年 | 1012篇 |
1989年 | 820篇 |
1988年 | 783篇 |
1987年 | 916篇 |
1986年 | 785篇 |
1985年 | 973篇 |
1984年 | 1135篇 |
1983年 | 976篇 |
1982年 | 954篇 |
1981年 | 855篇 |
1980年 | 821篇 |
1979年 | 790篇 |
1978年 | 766篇 |
1977年 | 671篇 |
1976年 | 621篇 |
1975年 | 617篇 |
1974年 | 594篇 |
1973年 | 645篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
B. Ahmed G. J. Alner H. Araujo J. C. Barton A. Bewick M. J. Carson D. Davidge J. V. Dawson T. Gamble S. P. Hart R. Hollingworth A. S. Howard W. G. Jones M. K. Joshi V. A. Kudryavtsev T. B. Lawson V. Lebedenko M. J. Lehner J. D. Lewin P. K. Lightfoot I. Liubarsky R. Lüscher J. E. McMillan B. Morgan G. Nicklin S. M. Paling R. M. Preece J. J. Quenby J. W. Roberts M. Robinson N. J. T. Smith P. F. Smith N. J. C. Spooner T. J. Sumner D. R. Tovey 《Astroparticle Physics》2003,19(6):691-702
The NAIAD experiment (NaI Advanced Detector) for weakly interacting massive particle (WIMP) dark matter searches at Boulby mine (UK) is described. The detector consists of an array of encapsulated and unencapsulated NaI(Tl) crystals with high light yield. Six crystals are collecting data at present. Data accumulated by four of them (10.6 kg × year exposure) have been used to set upper limits on the WIMP–nucleon spin-independent and WIMP–proton spin-dependent cross-sections. Pulse shape analysis has been applied to discriminate between nuclear recoils, as may be caused by WIMP interactions, and electron recoils due to gamma background. Various calibrations of crystals are presented. 相似文献
103.
H. L. Xu S. Svanberg R. D. Cowan P.-H. Lefèbvre P. Quinet E. Biémont 《Monthly notices of the Royal Astronomical Society》2003,346(2):433-440
Radiative lifetime measurements were performed with time-resolved laser-induced fluorescence techniques for 24 levels of Nd ii in the energy range 20 500–32 500 cm−1 . For 17 levels, no previous experimental data exist. These results have allowed the testing of new theoretical calculations with the relativistic Hartree–Fock method taking configuration interactions and core-polarization effects into account, and a satisfying agreement has been found for this complex ion. A new set of calculated oscillator strengths, accurate within a few per cent for the strongest transitions, is presented for 107 lines of astrophysical interest appearing in the wavelength range 358.0–1100.0 nm. These results will be useful to evaluate abundance values of neodymium in chemically peculiar stars in relation with cosmochronology. 相似文献
104.
105.
Jean-Pierre Macquart Kinwah Wu Diana C. Hannikainen Robert J. Sault David L. Jauncey 《Astrophysics and Space Science》2003,288(1-2):105-119
We compare the observational properties of the circular polarization in Galactic jet sources with that observed in AGN, and outline the constraints they place on the mechanism responsible for the circular polarization. We also discuss the implications of the time scale of polarization variations on the mechanism responsible for the circular polarization. 相似文献
106.
L. Makarova E. Grebel I. Karachentsev A. Dolphin V. Karachentseva M. Sharina D. Geisler P. Guhathakurta P. Hodge A. Sarajedini P. Seitzer 《Astrophysics and Space Science》2003,285(1):107-111
We present a quantitative star formation history derivation of the four suspected tidal dwarf galaxies in the M 81 group:
Holmberg IX, BK3N,Arp-loop (A0952+69) and Garland using HST/WFPC2 images of these galaxies. We construct a library of synthetic
Colour-Magnitude Diagrams(CMDs) based on theoretical isochrones and data-derived determinations of photometric errors. These
synthetic CMDs were combined linearly andχ2-compared to observed photometry. All the galaxies show continuous star formation between about 20 and 200 Myr ago with star
formation rates between 7.5⋅10-3 M⊙/yr and 7.67⋅10-4 M⊙/yr. The metallicity of the detected stars is spanning rather a wide range, being lower than solar abundance. We suppose,
that all the galaxies were formed out of material from metal-poor outer part of the giant spiral galaxy M81after tidal interaction
about 200 Myr ago. However, this suggestion requires significantly more deep color-magnitude diagrams to be sure with the
scenario of the galaxy evolution.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
107.
108.
We present the results of BVRIZ photometry of 56 near-Earth objects (NEOs) obtained with the 1-m Jacobus Kapteyn telescope on La Palma during 2000 and 2001. Our sample includes many NEOs with particularly deep 1-μm pyroxene/olivine absorption bands, similar to Q-type asteroids. We also classify three NEOs with particularly blue colors. No D-type asteroids were found, placing an upper limit of ∼2% on the fraction of the NEO population originating in the outer main belt or the Trojan clouds. The ratio of dark to bright objects in our sample was found to be 0.40, significantly higher than current theoretical predictions. As well as classifying the NEOs, we have investigated color trends with size and orbit. We see a general trend for larger silicate objects to have shallower absorption bands but find no significant difference in the distribution of taxonomic classes at small and large sizes. Our data clearly show that different taxonomic classes tend to occupy different regions of (a, e) space. By comparing our data with current model predictions for NEO dynamical evolution we see that Q-, R-, and V-type NEOs tend to have orbits associated with “fast track” delivery from the main belt, whereas S-type NEOs tend to have orbits associated with “slow track” delivery. This outcome would be expected if space weathering occurs on time scales of >106 years. 相似文献
109.
110.