全文获取类型
收费全文 | 16568篇 |
免费 | 1152篇 |
国内免费 | 241篇 |
专业分类
测绘学 | 525篇 |
大气科学 | 1575篇 |
地球物理 | 5494篇 |
地质学 | 6211篇 |
海洋学 | 1008篇 |
天文学 | 2141篇 |
综合类 | 234篇 |
自然地理 | 773篇 |
出版年
2023年 | 54篇 |
2022年 | 88篇 |
2021年 | 224篇 |
2020年 | 228篇 |
2019年 | 184篇 |
2018年 | 878篇 |
2017年 | 844篇 |
2016年 | 907篇 |
2015年 | 659篇 |
2014年 | 698篇 |
2013年 | 939篇 |
2012年 | 1238篇 |
2011年 | 1047篇 |
2010年 | 694篇 |
2009年 | 784篇 |
2008年 | 589篇 |
2007年 | 536篇 |
2006年 | 493篇 |
2005年 | 1112篇 |
2004年 | 1154篇 |
2003年 | 895篇 |
2002年 | 395篇 |
2001年 | 276篇 |
2000年 | 224篇 |
1999年 | 159篇 |
1998年 | 174篇 |
1997年 | 189篇 |
1996年 | 121篇 |
1995年 | 119篇 |
1994年 | 132篇 |
1993年 | 91篇 |
1992年 | 80篇 |
1991年 | 86篇 |
1990年 | 125篇 |
1989年 | 74篇 |
1988年 | 58篇 |
1987年 | 78篇 |
1986年 | 68篇 |
1985年 | 62篇 |
1984年 | 83篇 |
1983年 | 69篇 |
1982年 | 71篇 |
1981年 | 69篇 |
1980年 | 52篇 |
1978年 | 52篇 |
1977年 | 54篇 |
1975年 | 51篇 |
1974年 | 51篇 |
1973年 | 57篇 |
1971年 | 54篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
21.
Valentin D. Ivanov G. Chauvin C. Foellmi M. Hartung N. Huélamo C. Melo D. Nürnberger M. Sterzik 《Astrophysics and Space Science》2006,304(1-4):247-249
The multiplicity of early-type stars is still not well established. The derived binary fraction is different for individual star forming regions, suggesting a connection with the age and the environment conditions. The few studies that have investigated this connection do not provide conclusive results. To fill in this gap, we started the first detailed adaptive-optic-assisted imaging survey of early-type field stars to derive their multiplicity in a homogeneous way. The sample has been extracted from the Hipparcos Catalog and consists of 341 BA-type stars within ∼300 pc from the Sun. We report the current status of the survey and describe a Monte-Carlo simulation that estimates the completeness of our companion detection. 相似文献
22.
23.
Arnaud M. Aubourg E. Bareyre P. Br';ehin S. Caridroit R. de Kat J. Dispau G. Djidi K. Gros M. Lachièze-Rey M. Laigneau Y. Laurent B. Lesquoy E. Lavocat Ph. Magneville C. Mazeau B. Milsztajn A. Moscoso L. Pasquaud J. Paul B. Perrin P. Petibon J. Piret Y. Queinnec F. Rich J. Spiro M. de Trogoff J. Vigroux L. Zylberajch S. Ansari R. Cavalier F. Moniez M. Beaulieu J. P. Ferlet R. Grison Ph. Vidal-Madjar A. Adrianzyk G. Berger J. P. Burnage R. Delclite J. C. Kohler D. Magnan R. Richaud A. Guibert J. Moreau O. Tajahmady F. Baranne A. Maurice E. Prévôt L. Gry C. 《Experimental Astronomy》1994,4(3-4):265-278
A 20cm
2
CCD mosaic camera has been especially built to search for dark galactic halo objects by the gravitational microlensing effect. The sensitive area is made of 16 edge-buttable CCDs developped by Thomson-CTS, with 23×23 µm
2
pixels. The 35 kg camera housing and mechanical equipment is presented. The associated electronics and data acquisition system are described in a separate paper. The camera resides at the focal plane of a 40 cm, f/10, Ferson reflector. The instrument has been in operation since December 1991 at the La Silla Observatory (ESO). 相似文献
24.
Yannick Giraud-Héraud Jean Kaplan François De Volnay Martin Charling Tao Sylvaine Turck-Chièze 《Solar physics》1990,128(1):21-33
The Saclay solar evolution code is used to check the effect of WIMPs on solar evolution. In this paper we study the effects of various types of Cosmion-matter interactions, give constraints on the crosssections compatible with the measured neutrino rate of 2 SNU on chlorine, and relate these constraints to ongoing dark matter detection experiments.Unité associée au CNRS UA 280, F-75251 Paris Cedex 05, France.On leave from LPC, Collège de France. 相似文献
25.
Vladimír Skalský 《Astrophysics and Space Science》1993,201(1):3-14
(a) Hubble's discovery of the expansion of the Universe makes it possible to choose unambiguously from the models described by Friedmann's equations of universe dynamics. (b) From the present temperature of the cosmic microwave background radiation, the specific entropy in the matter era and the model properties of the expansive nondecelerative universe, we can determine the present parameters of our Universe with deviations smaller than 2.2%. 相似文献
26.
María Luisa García Vargas Angeles Díaz Roberto Terlevich Elena Terlevich 《Astrophysics and Space Science》1993,205(1):77-84
In the frame of the Starburst Model, we show that the evolution of a massive stellar cluster in a high metallicity environment can reproduce the observed emission-line spectrum and the UV-optical Spectral Energy Distribution of the Seyfert 2 galaxies and LINERs. We apply the results of our models to three objects: NGC 5506, NGC 5643 and Mk 348. 相似文献
27.
The trans-Neptunian belt has been subject to a strong depletion that has reduced its primordial population by a factor of one hundred over the solar system's age. One by-product of such a depletion process is the existence of a scattered disk population in transit from the belt to other places, such as the Jupiter zone, the Oort cloud or interstellar space. We have integrated the orbits of the scattered disk objects (SDOs) so far discovered by 2500 Myr to study their dynamical time scales and the probability of falling in each of the end states mentioned above, paying special attention to their contribution to the Oort cloud. We found that their dynamical half-time is close to 2.5 Gyr and that about one third of the SDOs end up in the Oort cloud. 相似文献
28.
We investigate the metal enrichment of the intra-cluster medium by using a method that combines N-Body simulations and a semi-analytic
model (SAM) of galaxy formation. The cluster of galaxies is simulated in a flat, low density universe, with a numerical resolution
that allows the detection of substructures in the dark matter background of the cluster. The phenomenological approach used
to model the physical processes involved in the galaxy formation and metal production is applied to the substructures found
in the dark matter halos detected at different redshifts. Details of the chemical implementation in the SAM and first results
related to the mean properties of the baryonic matter components are presented.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
29.
Gérard Daigne Patrick Charlot Christine Ducourant Jean-François Lestrade 《Astrophysics and Space Science》2003,286(1-2):255-260
The question of positioning the optical counterparts of the ICRF quasars is outlined in the perspective of future space astrometry
missions, which ultimately will bring a new realization of the ICRS in the optical range. Ground-based interferometry with
a dual-field observing mode (PRIMA/VLTI),together with the missions DIVA and FAME, will have a key role in building an extragalactic
reference frame in the optical/near-IR range with about the same accuracy as that of the present (VLBI) primary frame.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
30.
Milan Burša 《Earth, Moon, and Planets》1992,56(1):57-60
The tidal long-term decrease in the angular velocity of the Earth's rotation has been estimated on the basis of the angular momentum tidal balance in the Earth-Moon-Sun system. The observed (LLR) tidal long-term decrease in the Moon's mean motion, the apparent secular acceleration in the mean longitude of the Sun and the long-term decrease in the 2nd degree zonal geopotential parameter were used.Presented at the XXth General Assembly of the I.A.G., Vienna, August 15, 1991. 相似文献