全文获取类型
收费全文 | 7214篇 |
免费 | 1113篇 |
国内免费 | 1630篇 |
专业分类
测绘学 | 94篇 |
大气科学 | 202篇 |
地球物理 | 796篇 |
地质学 | 4586篇 |
海洋学 | 622篇 |
天文学 | 2148篇 |
综合类 | 317篇 |
自然地理 | 1192篇 |
出版年
2024年 | 32篇 |
2023年 | 106篇 |
2022年 | 316篇 |
2021年 | 322篇 |
2020年 | 298篇 |
2019年 | 328篇 |
2018年 | 284篇 |
2017年 | 274篇 |
2016年 | 261篇 |
2015年 | 314篇 |
2014年 | 315篇 |
2013年 | 371篇 |
2012年 | 338篇 |
2011年 | 348篇 |
2010年 | 298篇 |
2009年 | 551篇 |
2008年 | 442篇 |
2007年 | 489篇 |
2006年 | 543篇 |
2005年 | 409篇 |
2004年 | 404篇 |
2003年 | 450篇 |
2002年 | 363篇 |
2001年 | 305篇 |
2000年 | 308篇 |
1999年 | 258篇 |
1998年 | 281篇 |
1997年 | 189篇 |
1996年 | 141篇 |
1995年 | 126篇 |
1994年 | 132篇 |
1993年 | 84篇 |
1992年 | 85篇 |
1991年 | 44篇 |
1990年 | 46篇 |
1989年 | 26篇 |
1988年 | 21篇 |
1987年 | 22篇 |
1986年 | 10篇 |
1985年 | 3篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1954年 | 3篇 |
排序方式: 共有9957条查询结果,搜索用时 0 毫秒
971.
972.
Jørgen Christensen-Dalsgaard 《Astrophysics and Space Science》2003,284(1):277-294
The workshop took place at the beginning of what promises tobe a golden age of asteroseismology.Ground-based instrumentation is finally reaching a level of stabilitywhich allows detailed investigations of solar-like oscillations in atleast bright, slowly rotating main-sequence stars.Very extensive results are expected from the coming space missions,including data on a broad range of stars from the Eddington mission.The observational situation is therefore extremely promising.To make full use of these promises, major efforts are requiredtowards the efficient utilization of the data, through the developmentof techniques for the analysis and interpretation of the data.A broad range of topics related to these issues is discussed in the presentproceedings. Here I review some of the relevant problems,relate the asteroseismic investigations to broader areas of astrophysics and consider briefly the basis for our great expectations for the developmentof the field. 相似文献
973.
Birgitta NordstrÖm 《Astrophysics and Space Science》2003,284(2):779-782
New, precise abundance data for a large number of elements in a growing sample of extremely metal-poor stars are accumulating
from the new 8-m telescopes. Combined with theoretical models, these results advance our understanding of the first generations
of stars, whose nucleosynthesis products are fossilised in the oldest stars we see today and thus give clues to the earliest
phases of evolution in the Galaxy. In particular, the heaviest elements give us insight into the different neutron capture
mechanisms and the stellar sites where such elements could be produced. They also afford an independent way to determine the
age of the Galaxy, by radioactive chronology.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
974.
975.
Stephen Serjeant Duncan Farrah James Geach Toshinobu Takagi Aprajita Verma Ali Kaviani Matt Fox 《Monthly notices of the Royal Astronomical Society》2003,346(4):L51-L56
We present the K -band Hubble diagrams ( K – z relations) of submillimetre-selected galaxies and hyperluminous galaxies (HLIRGs). We report the discovery of a remarkably tight K – z relation of HLIRGs, indistinguishable from that of the most luminous radio galaxies. Like radio galaxies, the HLIRG K – z relation at z ≲ 3 is consistent with a passively evolving ∼3 L * instantaneous starburst starting from a redshift of z ∼ 10 . In contrast, many submillimetre-selected galaxies are ≳2 mag fainter, and the population has a much larger dispersion. We argue that dust obscuration and/or a larger mass range may be responsible for this scatter. The galaxies so far proved to be hyperluminous may have been biased towards higher AGN bolometric contributions than submillimetre-selected galaxies due to the 60-μm selection of some, so the location on the K – z relation may be related to the presence of the most massive active galactic nucleus. Alternatively, a particular host galaxy mass range may be responsible for both extreme star formation and the most massive active nuclei. 相似文献
976.
We present R-band galaxy luminosity functions (GLFs) from aspectroscopic sample of six nearby rich galaxy clusters. In addition
to individual cluster GLFs, extending to, in one case, M
R=–14, we also present composite GLFs for cluster and field galaxies toM
R=–17. All six cluster samples are consistent with the composite GLF, but there is evidence that the GLF of the quiescent population
in clusters is not universal. Furthermore, the GLF of quiescent galaxies is significantly steeper in clusters than in the
field. The overall GLF in clusters is consistent with that of field galaxies, except for the luminous tip, which is enhanced
in clusters versus the field.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
977.
Aaron J. Grocholski Ata Sarajedini 《Monthly notices of the Royal Astronomical Society》2003,345(3):1015-1029
We present combined optical/near-infrared photometry ( BVIK ) for six open clusters – M35, M37, NGC 1817, NGC 2477, NGC 2420 and M67. The open clusters span an age range from 150 Myr to 4 Gyr and have metal abundances from [Fe/H]=−0.27 to +0.09 dex. We have utilized these data to test the robustness of theoretical main sequences constructed by several groups as denoted by the following designations – Padova, Baraffe, Y2 , Geneva and Siess. The comparisons of the models with the observations have been performed in the [ MV , ( B − V )0 ], [ MV , ( V − I )0 ] and [ MV , ( V − K )0 ] colour–magnitude diagrams as well as the distance-independent [( V − K )0 , ( B − V )0 ] and [( V − K )0 , ( V − I )0 ] two-colour diagrams. We conclude that none of the theoretical models reproduces the observational data in a consistent manner over the magnitude and colour range of the unevolved main sequence. In particular, there are significant zero-point and shape differences between the models and the observations. We speculate that the crux of the problem lies in the precise mismatch between theoretical and observational colour–temperature relations. These results underscore the importance of pursuing the study of stellar structure and stellar modelling with even greater intensity. 相似文献
978.
Chan Kwing Lam 《紫金山天文台台刊》2003,(2)
1 IntroductionManybottlenecksinthetheoreticalstudyofstellarevolutionarisefromthelackofunder standingofsomehighlycomplicatedprocessesthatcannotbetreatedwithanalyticaltech niques .Alargeportionoftheseprocessesisrelatedtohydrodynamics,particularlyconvec tion .Theapplicationofmultidimensionalnumericalcomputationstotheinvestigationofthesedifficultproblemshasmadegreatprogressinrecentyears .Here ,weprovideasurveyoftherecentnumericalstudiesofconvectionrelatedproblems.Theobjectiveistoassistthosewhoar… 相似文献
979.
Donald L. Hardesty 《The Professional geographer》1986,38(1):11-18
Several issues surrounding the concept of cultural adaptation and its significance to cultural geography are discussed. A new model of cultural adaptation is developed to explain the evolution of spatial structures. Also a research agenda for geographic inquiry is proposed. 相似文献
980.
Paul J. Wiita 《Journal of Astrophysics and Astronomy》1981,2(4):387-403
Previous first-order analytic treatments of rotation acting upon stellar equilibria are extended to include later, post-Helium
burning, stages of stellar evolution. Strong differential rotation is capable of substantially increasing the photon luminosities
of post-main sequence stars, and thus accelerating their evolution. On the other hand, uniform rotation reduces the photon
flux for a wide range of stellar interior types and conditions. Similar conclusions are drawn regarding the effects of rotation
on the emission of neutrinos in pre-collapse phases of evolution. A brief discussion of the gravitational radiation emitted
during these phases is also given. 相似文献