全文获取类型
收费全文 | 8877篇 |
免费 | 839篇 |
国内免费 | 788篇 |
专业分类
测绘学 | 310篇 |
大气科学 | 1383篇 |
地球物理 | 2320篇 |
地质学 | 3811篇 |
海洋学 | 671篇 |
天文学 | 1155篇 |
综合类 | 247篇 |
自然地理 | 607篇 |
出版年
2024年 | 22篇 |
2023年 | 72篇 |
2022年 | 135篇 |
2021年 | 243篇 |
2020年 | 259篇 |
2019年 | 221篇 |
2018年 | 453篇 |
2017年 | 443篇 |
2016年 | 570篇 |
2015年 | 428篇 |
2014年 | 499篇 |
2013年 | 667篇 |
2012年 | 554篇 |
2011年 | 531篇 |
2010年 | 513篇 |
2009年 | 489篇 |
2008年 | 410篇 |
2007年 | 342篇 |
2006年 | 317篇 |
2005年 | 260篇 |
2004年 | 248篇 |
2003年 | 221篇 |
2002年 | 212篇 |
2001年 | 174篇 |
2000年 | 174篇 |
1999年 | 203篇 |
1998年 | 163篇 |
1997年 | 199篇 |
1996年 | 144篇 |
1995年 | 139篇 |
1994年 | 135篇 |
1993年 | 89篇 |
1992年 | 58篇 |
1991年 | 70篇 |
1990年 | 87篇 |
1989年 | 48篇 |
1988年 | 41篇 |
1987年 | 53篇 |
1986年 | 45篇 |
1985年 | 41篇 |
1984年 | 48篇 |
1983年 | 39篇 |
1982年 | 37篇 |
1981年 | 43篇 |
1980年 | 22篇 |
1979年 | 30篇 |
1978年 | 22篇 |
1977年 | 23篇 |
1975年 | 18篇 |
1973年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 484 毫秒
21.
JiřÍ Polcar Martin Topinka Graziella Pizzichini Eliana Palazzi Nicola Masetti RenÉ Hudec Věra HudcovÁ 《Astrophysics and Space Science》2005,296(1-4):485-488
We report on our statistical research of space–time correlated supernovae and CGRO-BATSE gamma-ray bursts (GRBs). There exists
a significantly higher abundance of core-collapse supernovae among the correlated supernovae, but the subset of all correlated
objects does not seem to be physically different from the whole set. 相似文献
22.
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
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.
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
26.
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
27.
28.
M. Fiore L. O. Silva C. Ren M. A. Tzoufras W. B. Mori 《Monthly notices of the Royal Astronomical Society》2006,372(4):1851-1855
The dynamics of two counter-streaming electron–positron–ion unmagnetized plasma shells with zero net charge is analysed in the context of magnetic field generation in gamma-ray burst internal shocks due to the Weibel instability. The effects of large thermal motion of plasma particles, arbitrary mixture of plasma species and space charge effects are taken into account. We show that, although thermal effects slow down the instability, baryon loading leads to a non-negligible growth rate even for large temperatures and different shell velocities, thus guaranteeing the robustness and the occurrence of the Weibel instability for a wide range of scenarios. 相似文献
29.
Szilárd Csizmadia Zsolt Kővári Péter Klagyivik 《Astrophysics and Space Science》2006,304(1-4):355-357
We carried out optical and Hα photometry of two contact binaries (V861 Herculis, EQ Tauri). The light curve modeling revealed stellar spots in both contact systems and strong Hα excess in the position of the observed stellar spots. A correlation was found between the V−R and R−Hα colour indices of V861 Her. 相似文献
30.
黄淮海平原地下水开采的水文效应 总被引:1,自引:0,他引:1
黄淮海平原是我国地下水开发最早,利用程度最高的地区。随着地下水开采量急剧增长,已产生了一系列水文效应变化,其中包括区域地下水位下降和地下水降落漏斗的形成;开采浅层地下水对地表径流和降雨入渗补给的地下水量的影响,井灌井排在盐碱土的改良作用等。 相似文献