全文获取类型
收费全文 | 119020篇 |
免费 | 7138篇 |
国内免费 | 8626篇 |
专业分类
测绘学 | 4853篇 |
大气科学 | 12695篇 |
地球物理 | 24798篇 |
地质学 | 46396篇 |
海洋学 | 11575篇 |
天文学 | 22070篇 |
综合类 | 3866篇 |
自然地理 | 8531篇 |
出版年
2023年 | 679篇 |
2022年 | 1982篇 |
2021年 | 2633篇 |
2020年 | 2338篇 |
2019年 | 2645篇 |
2018年 | 4043篇 |
2017年 | 3754篇 |
2016年 | 4547篇 |
2015年 | 3102篇 |
2014年 | 4571篇 |
2013年 | 6383篇 |
2012年 | 4585篇 |
2011年 | 5504篇 |
2010年 | 5196篇 |
2009年 | 6064篇 |
2008年 | 5298篇 |
2007年 | 5257篇 |
2006年 | 4665篇 |
2005年 | 3765篇 |
2004年 | 3507篇 |
2003年 | 3339篇 |
2002年 | 3222篇 |
2001年 | 2980篇 |
2000年 | 3003篇 |
1999年 | 3095篇 |
1998年 | 2871篇 |
1997年 | 2690篇 |
1996年 | 2397篇 |
1995年 | 2232篇 |
1994年 | 1954篇 |
1993年 | 1750篇 |
1992年 | 1558篇 |
1991年 | 1463篇 |
1990年 | 1428篇 |
1989年 | 1217篇 |
1988年 | 1152篇 |
1987年 | 1166篇 |
1986年 | 1033篇 |
1985年 | 1224篇 |
1984年 | 1350篇 |
1983年 | 1217篇 |
1982年 | 1128篇 |
1981年 | 1083篇 |
1980年 | 953篇 |
1979年 | 911篇 |
1978年 | 871篇 |
1977年 | 748篇 |
1976年 | 708篇 |
1975年 | 711篇 |
1973年 | 716篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
361.
362.
山区短波反射辐射的计算模式 总被引:2,自引:0,他引:2
本文提出计算山区测点可接受到的来自周围山地的短波反射辐射日平均通量密度的通用计算机模式,并以大别山南段赵公岭山区为例进行了试验,结果表明,该式通用性强、精度较高。 相似文献
363.
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
364.
The cumulative probability distributions for stream order, stream length, contributing area, and energy dissipation per unit length of channel are derived, for an ordered drainage system, from Horton's laws of network composition. It is shown how these distributions can be related to the fractal nature of single rivers and river networks. Finally, it is shown that the structure proposed here for these probability distributions is able to fit the observed frequency distributions, and their deviations from straight lines in a log-log plot. 相似文献
365.
利用上海天文台的照相底片资料,确定了疏散星团NGC6530天区364颗恒星的自行和成员概率,并对有关自行测定的方法、结果和精度等问题作了较为详细的介绍和讨论。使用的底片历元差为87年,全部恒星自行中误差的均方根值为1.09mas/a。 相似文献
366.
We discuss the possibility of setting upper limits to deviations of the dimensionD of space from the standard integer value of 3. The method we suggest — a reanalysis of the Planck law for the black-body radiation in aD-dimensional space — is less sensitive than other methods previously suggested. It offers, however, the possibility of probing the fractal dimension of space-time over cosmological distances. 相似文献
367.
The self-consistent dynamic pole tide in global oceans 总被引:1,自引:0,他引:1
S. R. Dickman 《Geophysical Journal International》1985,81(1):157-174
368.
369.
A.W.R. Bevan R. Hutchison A.J. Easton G.P. Durant C.M. Farrow 《Meteoritics & planetary science》1985,20(3):491-501
High Possil and Strathmore are the first (1804) and last (1917) meteorite falls, respectively, of the three recorded in Scotland. Olivine compositions and total Fe contents in High Possil (Fa25.2; 21.35 wt %) and Strathmore (Fa25.3; 20.6 wt %) confirm their classification as L-group chondrites (Mason, 1963), and the presence of abundant plagioclase feldspar shows that both chondrites belong to petrologic type 6. Both chondrites display thermal and mechanical alteration attributable to moderate shock-loading appropriate to facies c (High Possil) and c-d (Strathmore) (Dodd and Jarosewich, 1979). Incipient shock-melting of metal and troilite in both chondrites is the first described from Lc chondrites, and differences in the responses of metallic and silicate minerals to shock-loading are discussed. 相似文献
370.
R. K. Pant N. Basavaiah N. Juyal N. K. Saini M. G. Yadava E. Appel A. K. Singhvi 《第四纪科学杂志》2005,20(5):485-492
The southwest monsoon that dominated Central Himalaya has preserved loessic silt deposits preserved in patches that are proximal to periglacial areas. The occurrence of such silts suggests contemporary prevalence of cold and dry northwesterly winds. Field stratigraphy, geochemistry, mineral magnetism, infrared stimulated luminescence (IRSL) and radiocarbon dating has enabled reconstruction of an event chronology during the past 20 ka. Three events of loess accretion could be identified. The first two events of loess deposition occurred betweem 20 and 9 ka and were separated by a phase of moderate weathering. Pedogenesis at the end of this event gave rise to a well‐developed soil that was bracketed around 9 to > 4 ka. This was followed by the third phase of loess accretion that occurred around 4 to > 1 ka. Episodes of loess deposition and soil formation are interpreted in terms of changes in the strength of the Indian southwest monsoon. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献