全文获取类型
收费全文 | 11011篇 |
免费 | 400篇 |
国内免费 | 83篇 |
专业分类
测绘学 | 317篇 |
大气科学 | 785篇 |
地球物理 | 3260篇 |
地质学 | 4061篇 |
海洋学 | 607篇 |
天文学 | 1903篇 |
综合类 | 45篇 |
自然地理 | 516篇 |
出版年
2022年 | 83篇 |
2021年 | 159篇 |
2020年 | 157篇 |
2019年 | 151篇 |
2018年 | 610篇 |
2017年 | 497篇 |
2016年 | 583篇 |
2015年 | 363篇 |
2014年 | 496篇 |
2013年 | 638篇 |
2012年 | 492篇 |
2011年 | 530篇 |
2010年 | 514篇 |
2009年 | 569篇 |
2008年 | 447篇 |
2007年 | 370篇 |
2006年 | 402篇 |
2005年 | 313篇 |
2004年 | 288篇 |
2003年 | 274篇 |
2002年 | 204篇 |
2001年 | 181篇 |
2000年 | 184篇 |
1999年 | 145篇 |
1998年 | 180篇 |
1997年 | 172篇 |
1996年 | 141篇 |
1995年 | 125篇 |
1994年 | 120篇 |
1993年 | 112篇 |
1992年 | 86篇 |
1991年 | 88篇 |
1990年 | 92篇 |
1989年 | 80篇 |
1988年 | 83篇 |
1987年 | 84篇 |
1986年 | 99篇 |
1985年 | 90篇 |
1984年 | 80篇 |
1983年 | 89篇 |
1982年 | 89篇 |
1981年 | 77篇 |
1980年 | 71篇 |
1979年 | 65篇 |
1978年 | 64篇 |
1977年 | 61篇 |
1975年 | 59篇 |
1974年 | 50篇 |
1973年 | 64篇 |
1971年 | 52篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
The IRAS and 2MASS associations for 193 T Tauri stars are identified in this paper. From the color–color diagrams and spectral index, it is found that the IR excesses for most samples are due to thermal emission from the circumstellar material, as suggested previously. It is also found that the IR excesses at IRAS region for few T Tauri stars and the near-IR excesses for some T Tauri stars are likely attributed to free-free emission or free-bound emission from the circumstellar ionized gas. Moreover, It is found in deredened J–H versus H–K color–color diagram that there is a slight separation in different spectral groups. The T Tauri stars locus equation in J–H versus H–K color–color diagram for our sample is also presented. 相似文献
43.
The aim of the present paper is to analyze the light variation as well as the period changes of the eclipsing binary RZ Cas. New photometric elements are computed using the frequency-domain method. The possibility of the light-time effect and the apsidal motion is discussed. 相似文献
44.
J. Rajchl J. Bočcek D. Očenáš J. Škvarka P. Zimnikoval H. Murayama K. Ohtsuka 《Earth, Moon, and Planets》1995,68(1-3):479-486
Some results following from two contemporary photographical programs (Slovakia and Japan) for persistent meteor train spectra are compared. It shows that even though both programs are not too different according to their lenses and films used, the spectral interval detected is very different. In this respect prism as a dispersion element is more favourable than the grating with blaze wavelength near 610 nm. However, some results previously assumed as typicai for presented persistent trains-e.g. the forbidden Herzberg O2 emission, the NO2 continuum and OH red emissions-seem to be substanciated especially due to higher and linear dispersion of those grating spectra. 相似文献
45.
46.
P. G. Jonker G. Nelemans Z. Wang A. K. H. Kong D. Chakrabarty M. Garcia P. J. Groot M. van der Klis T. Kerr B. Mobasher M. Sullivan T. Augusteijn B. W. Stappers P. Challis R. P. Kirshner J. Hjorth A. Delsanti 《Monthly notices of the Royal Astronomical Society》2003,344(1):201-206
We have obtained optical and near-infrared images of the field of the accreting millisecond X-ray pulsar XTE J1751−305. There are no stars in the 0.7-arcsec error circle (0.7 arcsec is the overall uncertainty arising from tying the optical and X-ray images and from the intrinsic uncertainty in the Chandra X-ray astrometric solution). We derive limiting magnitudes for the counterpart of R > 23.1, I > 21.6, Z > 20.6, J > 19.6 and K > 19.2 . We compare these upper limits with the magnitudes one would expect for simple models for the possible donor stars and the accretion disc subject to the reddening observed in X-rays for XTE J1751−305 and when put at the distance of the Galactic Centre (8.5 kpc). We conclude that our non-detection does not constrain any of the models for the accretion disc or possible donor stars. Deep, near-infrared images obtained during quiescence will, however, constrain possible models for the donor stars in this ultracompact system. 相似文献
47.
Andrés E. Piatti Juan J. Clariá Andrea V. Ahumada 《Monthly notices of the Royal Astronomical Society》2003,346(2):390-402
Charge-coupled device (CCD) photometry in the Johnson V , Kron–Cousins I and Washington CMT 1 systems is presented in the field of the poorly known open cluster NGC 2627. Four independent Washington abundance indices yield a mean cluster metallicity of [Fe/H]=−0.12 ± 0.08 , which is compatible with the existence of a radial gradient in the Galactic disc. The resultant colour–magnitude diagrams indicate that the cluster is an intermediate-age object of 1.4 Gyr. Based on the best fits of the Geneva group's isochrones to the ( V , V − I ) and ( T 1 , C − T 1 ) diagrams, we estimate E ( V − I ) = 0.25 ± 0.05 and V − MV = 11.80 ± 0.25 for log t = 9.15 , and E ( C − T 1 ) = 0.23 ± 0.07 and T 1 − M T 1 = 11.85 ± 0.25 for log t = 9.10 , respectively, assuming solar metal content. The derived reddening value E ( C − T 1 ) implies E ( B − V ) = 0.12 ± 0.07 and a distance from the Sun of 2.0 ± 0.4 kpc . Using the WEBDA data base and the available literature, we re-examined the overall properties of all the open clusters with ages between 0.6 and 2.5 Gyr. We identified peaks of cluster formation at 0.7–0.8, 1.0–1.1, 1.6–1.7 and 2.0–2.1 Gyr, separated by relative quiescent epochs of ∼0.2–0.3 Gyr. We also estimated a radial abundance gradient of −0.08 ± 0.02 , which is consistent with the most recent determinations for the Galactic disc, but no clear evidence for a gradient perpendicular to the Galactic plane is found. 相似文献
48.
We obtain the possible ellipsoidal and hyperboloidal equilibrium figures of the light subsystem with internal fluxes of matter of constant vorticity inside a gravitating homogeneous triaxial ellipsoid. We obtain the domains of stability of these equilibrium figures with respect to second-form oscillations.Translated fromAstrofizika, Vol. 38, No. 2, 1995. 相似文献
49.
We describe how a local plasma structure can be changed by a transverse shear flow using numerical simulation to investigate the disturbance process near the magnetopause. The results show that magnetic field lines are bent by transverse shear flow disturbance near the current sheet region. There are multiple bipolar structures of the normal magnetic field in the numerical simulation. We term this new feature as K-point magnetic reconnection, realistic for discussing space observations. 相似文献
50.
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