全文获取类型
收费全文 | 9941篇 |
免费 | 3981篇 |
国内免费 | 3350篇 |
专业分类
测绘学 | 726篇 |
大气科学 | 1784篇 |
地球物理 | 2104篇 |
地质学 | 9732篇 |
海洋学 | 1182篇 |
天文学 | 247篇 |
综合类 | 690篇 |
自然地理 | 807篇 |
出版年
2024年 | 43篇 |
2023年 | 177篇 |
2022年 | 401篇 |
2021年 | 599篇 |
2020年 | 549篇 |
2019年 | 578篇 |
2018年 | 584篇 |
2017年 | 593篇 |
2016年 | 659篇 |
2015年 | 685篇 |
2014年 | 833篇 |
2013年 | 886篇 |
2012年 | 884篇 |
2011年 | 833篇 |
2010年 | 721篇 |
2009年 | 777篇 |
2008年 | 716篇 |
2007年 | 810篇 |
2006年 | 688篇 |
2005年 | 615篇 |
2004年 | 588篇 |
2003年 | 498篇 |
2002年 | 428篇 |
2001年 | 484篇 |
2000年 | 451篇 |
1999年 | 363篇 |
1998年 | 364篇 |
1997年 | 272篇 |
1996年 | 266篇 |
1995年 | 169篇 |
1994年 | 182篇 |
1993年 | 128篇 |
1992年 | 109篇 |
1991年 | 81篇 |
1990年 | 42篇 |
1989年 | 52篇 |
1988年 | 45篇 |
1987年 | 27篇 |
1986年 | 21篇 |
1985年 | 19篇 |
1984年 | 13篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1971年 | 1篇 |
1954年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Xiaolei Zhang 《Astrophysics and Space Science》2002,281(1-2):281-284
One of the important consequences of a newly discovered secular dynamical evolution process of spiral galaxies (Zhang, 1996,
1998, 1999) is that the orbiting disk matter receives energy injection each time it crosses the spiral density wave crest.
This energy injection has been shown to be able to quantitatively explain the observed age-velocity-dispersion relation of
the solar neighborhood stars. We demostrate in this paper that similar energy injection into the interstellar medium could
serve as the large-scale energy source to continuously power the observed interstellar turbulence and to offset its downward
cascade tendency.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
992.
993.
本文通过考虑强磁场中电子的量子效应,分析了强磁场下电子气体的Fermi能,讨论了磁场对核的屏蔽势和核反应率的影响,进而计算了强磁场对天体物理中几个较重要的热核反应的影响,结果表明,相对于无磁场而言,在较低密度下,足够强的磁场使原子核的屏蔽势显著增加,但在ρ/μe>10~5molcm~(-3)的密度下,中子星表面存在的强度为10~5~10~9T范围内的磁场对核反应率几乎没有影响。 相似文献
994.
通过对“95.8”大暴雨过程的全面技术总结,揭示了多种尺度系统间相互作用对产生大暴雨过程的贡献,并指出了云团的发生及其发展源于北方冷空气和南方低空急流持续影响所形成的两个中间尺度垂直环流。 相似文献
995.
996.
We have analysed short-exposure high-resolution images obtained on the William Herschel Telescope (WHT), Big Telescope Azimuthal (BTA) and CanadaFranceHawaii Telescope (CFHT) in order to investigate mechanical vibrations that are capable of reducing the high angular resolution allowed by speckle-interferometric methods. After filtering the photon noise we have computed power spectra of the image centres of gravity. In these spectra we have found vibration features that differ from one telescope to another and that vary in particular with the zenith angle. In the case of the WHT we discuss these results in terms of possible causes and in terms of degradation of the transfer function. We present some means to improve the data. 相似文献
997.
A recently developed near infrared high speed photometer intended for lunar oc-cultation studies is described. The primary scientific objective is to reach milli arc second levels of angular resolution so that circumstellar structure of the occulted sources can be resolved. Near infrared sky brightness close to the lunar limb is also studied. Angular diameter derived from the observed occultation of IRC +20169 is presented and system performance discussed. 相似文献
998.
B. Straughan 《国际地质力学数值与分析法杂志》2002,26(1):75-97
An accurate computational analysis is presented for the onset of thermal convection in a two‐layer system which is comprised of a saturated layer of porous material described by Darcy's law, over which lies a layer of the same saturating fluid. The two‐layer system is heated from below and the upper (fluid) surface is allowed to be fixed or stress free. The onset of convection may have a bi‐modal nature in which convection may be dominated by the porous medium or by the fluid depending on the depths of the relative layers, but this is strongly controlled by material parameters. The effect of variation of relevant fluid and porous material properties is investigated in detail, as is the effect of the interface boundary condition between the fluid and the porous medium. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
999.
A new technique designed to help quantify the degree of damage to the landscape from one area to another shows a close relationship between population density and the degree of landscape damage. The technique establishes a scale of damage from 0 to 5 (zero = no damage; 5 = severe damage) using data from aerial photographs, land-use maps, and field data. The related formula allows one to compare the relative degree of damage across regions using a combination of an absolute index, a theoretical index, a relative index, and population density. Xing'an County is used to demonstrate the technique. 相似文献
1000.
本文以爱黎-海斯卡宁均衡补偿假设模式为基础,利用圆模板编制了滇西北及邻区均衡重力异常图。分析了异常的基本特征与壳内构造的关系,并初步探讨了均衡重力异常和强震活动的相关性。 相似文献