全文获取类型
收费全文 | 113661篇 |
免费 | 1769篇 |
国内免费 | 921篇 |
专业分类
测绘学 | 2685篇 |
大气科学 | 7652篇 |
地球物理 | 21362篇 |
地质学 | 42762篇 |
海洋学 | 9930篇 |
天文学 | 25462篇 |
综合类 | 450篇 |
自然地理 | 6048篇 |
出版年
2022年 | 754篇 |
2021年 | 1254篇 |
2020年 | 1380篇 |
2019年 | 1490篇 |
2018年 | 4569篇 |
2017年 | 4131篇 |
2016年 | 4123篇 |
2015年 | 1817篇 |
2014年 | 3248篇 |
2013年 | 5509篇 |
2012年 | 4020篇 |
2011年 | 5860篇 |
2010年 | 5216篇 |
2009年 | 6387篇 |
2008年 | 5468篇 |
2007年 | 5864篇 |
2006年 | 4251篇 |
2005年 | 3207篇 |
2004年 | 3075篇 |
2003年 | 2943篇 |
2002年 | 2855篇 |
2001年 | 2357篇 |
2000年 | 2310篇 |
1999年 | 1827篇 |
1998年 | 1900篇 |
1997年 | 1762篇 |
1996年 | 1506篇 |
1995年 | 1489篇 |
1994年 | 1314篇 |
1993年 | 1203篇 |
1992年 | 1146篇 |
1991年 | 1160篇 |
1990年 | 1164篇 |
1989年 | 983篇 |
1988年 | 925篇 |
1987年 | 1097篇 |
1986年 | 931篇 |
1985年 | 1189篇 |
1984年 | 1286篇 |
1983年 | 1231篇 |
1982年 | 1143篇 |
1981年 | 1051篇 |
1980年 | 993篇 |
1979年 | 891篇 |
1978年 | 886篇 |
1977年 | 746篇 |
1976年 | 758篇 |
1975年 | 730篇 |
1974年 | 709篇 |
1973年 | 785篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
371.
E. Tóth F. Deak C. S. Gyurkócza Z. S. Kasztovszky R. Kuczi G. Marx B. Nagy S. Oberstedt L. Sajó-Bohus C. S. Sükösd G. Toth N. Vajda 《Environmental Geology》1997,31(1-2):123-127
A steady radon exhalation is assumed in most publications. In a village of North-East Hungary, however, high radon concentrations
have been measured, differing strongly in neighbouring houses and varying in time, due to the interplay of geochemical phenomena.
Received: 20 November 1995 · Accepted: 18 June 1996 相似文献
372.
R. W. A. Dallas 《The Photogrammetric Record》1989,13(73):133-136
The paper describes the material generated in carrying out architectural photogrammetric surveys. The importance of the archival nature of this material is highlighted and reference is made to the indexing and storing of the records. 相似文献
373.
V. I. Ferronsky S. A. Denisik S. V. Ferronsky 《Celestial Mechanics and Dynamical Astronomy》1996,64(3):167-183
The physical meaning of the terms of the potential and kinetic energy expressions, expanded by means of the density variation function for a nonuniform self-gravitating sphere, is discussed. The terms of the expansions represent the energy and the moment of inertia of the uniform sphere, the energy and the moment of inertia of the nonuniformities interacting with the uniform sphere, and the energy of the nonuniformities interacting with each other. It follows from the physical meaning of the above components of the energy structure, and also from the observational fact of the expansion of the Universe that the phase transition, notably, fusion of particles and nuclei and condensation of liquid and solid phases of the expanded matter accompanied by release of energy, must be the physical cause of initial thermal and gravitational instability of the matter. The released kinetic energy being constrained by the general motion of the expansion, develops regional and local turbulent (cyclonic) motion of the matter, which should be the second physical effect responsible for the creation of celestial bodies and their rotation. 相似文献
374.
375.
376.
377.
C. S. Crawford A. C. Fabian P. Gandhi R. J. Wilman R. M. Johnstone 《Monthly notices of the Royal Astronomical Society》2001,324(2):427-442
We present observations of a sample of optically faint, hard X-ray sources of the kind likely to be responsible for much of the hard X-ray background. We confirm that such sources are easily detected in the near-infrared, and find that they have a featureless continuum suggesting that the active nucleus is heavily obscured. The infrared colours of the majority of the targets observed are consistent with absorbed elliptical host galaxies at z =1–2. It is likely that we are observing some of the brighter members of the important new class of X-ray type II quasars. 相似文献
378.
We have undertaken a study of coronal features observed at meter-decameter wavelengths using the Clark Lake radioheliograph.
Among the coronal structures we have studied are the radio manifestations of coronal streamers on the solar disk and above
the solar limb. We have analyzed the radio data quantitatively, using ray-tracing models for comparison with the maps. Our
study provides information about the streamers' three-dimensional shapes, scales, and density profiles, for comparison with
related observations using white-light coronagraphs. 相似文献
379.
380.
A dominant source of errors in swath bathymetry is acoustic interference. In 1989 the author published an analysis of these errors and predicted depth accuracies for a system which reduced their effect by averaging. This present paper shows how a considerable improvement in performance may be obtained by a variety of signal processing strategies that include the use of several widely spaced receivers and the elimination of the most unsatisfactory measurements before averaging. Simulations show how impressive sea bed profiles can be produced with a single ping, even at low signal-to-interference ratios 相似文献