全文获取类型
收费全文 | 68713篇 |
免费 | 859篇 |
国内免费 | 672篇 |
专业分类
测绘学 | 1848篇 |
大气科学 | 4634篇 |
地球物理 | 12364篇 |
地质学 | 27339篇 |
海洋学 | 5929篇 |
天文学 | 14931篇 |
综合类 | 251篇 |
自然地理 | 2948篇 |
出版年
2022年 | 361篇 |
2021年 | 604篇 |
2020年 | 682篇 |
2019年 | 790篇 |
2018年 | 3965篇 |
2017年 | 3639篇 |
2016年 | 2992篇 |
2015年 | 987篇 |
2014年 | 1622篇 |
2013年 | 2779篇 |
2012年 | 2628篇 |
2011年 | 4466篇 |
2010年 | 4011篇 |
2009年 | 4634篇 |
2008年 | 3833篇 |
2007年 | 4414篇 |
2006年 | 2213篇 |
2005年 | 1826篇 |
2004年 | 1750篇 |
2003年 | 1710篇 |
2002年 | 1523篇 |
2001年 | 1175篇 |
2000年 | 1156篇 |
1999年 | 943篇 |
1998年 | 964篇 |
1997年 | 909篇 |
1996年 | 742篇 |
1995年 | 704篇 |
1994年 | 737篇 |
1993年 | 572篇 |
1992年 | 577篇 |
1991年 | 507篇 |
1990年 | 601篇 |
1989年 | 468篇 |
1988年 | 466篇 |
1987年 | 527篇 |
1986年 | 425篇 |
1985年 | 589篇 |
1984年 | 593篇 |
1983年 | 560篇 |
1982年 | 566篇 |
1981年 | 453篇 |
1980年 | 508篇 |
1979年 | 396篇 |
1978年 | 409篇 |
1977年 | 370篇 |
1976年 | 339篇 |
1975年 | 353篇 |
1974年 | 336篇 |
1973年 | 325篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
71.
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
72.
73.
A type IV radio burst accompanied by several normal- and reverse-drifting type III bursts, multiple long-term quasi-periodic pulsations and spikes was observed with the radio spectrometers (1.0–2.0 and 2.6–3.8 GHz) at National Astronomical Observatories of China (NAOC) on 23 September 1998. In combination with the images of Siberian Solar Radio Telescope (SSRT) of Russia, the complex and multiple magnetic structures inferred from the radio bursts reveal the existence of both large-scale and small-scale magnetic structures. This event suggests that the geometries of coronal magnetic fields contain multiple discrete electron acceleration/injection sites at different heights, and extended open and closed magnetic field lines. It can be shown that the energetic electrons gain access to open, diverging and closed field lines thus producing different types of radio bursts. From the characteristics of position, polarization, dispersion and displacement of the sources, the model of the type IV event is supported, which involves synchrotron emission from the electrons confined by the rapid scattering through the interaction of hydromagnetic wave with particles. 相似文献
74.
75.
76.
77.
Radiation exposure and Mission Strategies
for Interplanetary Manned Missions (REMSIM) 总被引:1,自引:0,他引:1
C. Cougnet N. B. Crosby S. Eckersley C. Foullon V. Guarnieri S. Guatelli D. Heynderickx A. Holmes-Siedle C. Lobascio S. Masiello P. Nieminen G. Parisi P. Parodi M. A. Perino M. G. Pia R. Rampini P. Spillantini V. Tamburini E. Tracino 《Earth, Moon, and Planets》2004,94(3-4):279-285
Cosmic radiation is an important problem for human interplanetary missions. The “Radiation Exposure and Mission Strategies for Interplanetary Manned Missions–REMSIM” study is summarised here. They are related to current strategies and countermeasures to ensure the protection of astronauts from radiation during interplanetary missions, with specific reference to: radiation environment and its variability; radiation effects on the crew; transfer trajectories and associated fluences; vehicle and surface habitat concepts; passive and active shielding concepts; space weather monitoring and warning systems. 相似文献
78.
Irina N Belskaya Vasilij G Shevchenko Yurij N Krugly Yurij S Efimov Alberto Cellino 《Icarus》2003,166(2):276-284
The first results of the observational program devoted to simultaneous investigation of asteroid polarimetric and photometric opposition phenomena are presented. UBVRI polarimetric and V-band photometric observations of the S-type Asteroid 20 Massalia and the E-type Asteroids 214 Aschera and 620 Drakonia were carried out in 1996-1999 down to phase angles of 0.08°, 0.7°, and 1.2°, correspondingly. The S-type Asteroid 20 Massalia is characterized by the pronounced brightness opposition surge with an amplitude larger than that observed for the E-type asteroids. A sharp peak of negative polarization at small phase angles was not observed for this asteroid. The value of polarization degree at phase angle α<1° is less than 0.5% for both S and E types. The negative polarization branches of S and especially E-asteroids have an asymmetrical shape. The phase angle at which the polarization minimum occurs is close to the angle at which non-linear increase begins in the asteroid magnitude phase curves. A relation of the observed effects to the mechanism of coherent backscattering is discussed. 相似文献
79.
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
80.