全文获取类型
收费全文 | 90071篇 |
免费 | 1514篇 |
国内免费 | 885篇 |
专业分类
测绘学 | 2409篇 |
大气科学 | 6347篇 |
地球物理 | 17775篇 |
地质学 | 32214篇 |
海洋学 | 7841篇 |
天文学 | 21097篇 |
综合类 | 351篇 |
自然地理 | 4436篇 |
出版年
2022年 | 550篇 |
2021年 | 944篇 |
2020年 | 1015篇 |
2019年 | 1038篇 |
2018年 | 2397篇 |
2017年 | 2259篇 |
2016年 | 2827篇 |
2015年 | 1578篇 |
2014年 | 2734篇 |
2013年 | 4708篇 |
2012年 | 2923篇 |
2011年 | 3742篇 |
2010年 | 3356篇 |
2009年 | 4383篇 |
2008年 | 3680篇 |
2007年 | 3717篇 |
2006年 | 3466篇 |
2005年 | 2627篇 |
2004年 | 2647篇 |
2003年 | 2476篇 |
2002年 | 2381篇 |
2001年 | 2119篇 |
2000年 | 1982篇 |
1999年 | 1671篇 |
1998年 | 1757篇 |
1997年 | 1607篇 |
1996年 | 1411篇 |
1995年 | 1364篇 |
1994年 | 1217篇 |
1993年 | 1075篇 |
1992年 | 1018篇 |
1991年 | 1040篇 |
1990年 | 1123篇 |
1989年 | 932篇 |
1988年 | 901篇 |
1987年 | 1045篇 |
1986年 | 910篇 |
1985年 | 1151篇 |
1984年 | 1283篇 |
1983年 | 1180篇 |
1982年 | 1095篇 |
1981年 | 1043篇 |
1980年 | 944篇 |
1979年 | 904篇 |
1978年 | 887篇 |
1977年 | 762篇 |
1976年 | 725篇 |
1975年 | 744篇 |
1974年 | 693篇 |
1973年 | 748篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
121.
We present warm dark matter (WDM) as a possible solution to the missing satellites and angular momentum problem in galaxy
formation and introduce improved initial conditions for numerical simulations of WDM models, which avoid the formation of
unphysical haloes found in earlier simulations. There is a hint, that because of that the mass function of satellite haloes
has been overestimated so far, pointing to higher values for the WDM particle mass.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
122.
H. L. Xu S. Svanberg R. D. Cowan P.-H. Lefèbvre P. Quinet E. Biémont 《Monthly notices of the Royal Astronomical Society》2003,346(2):433-440
Radiative lifetime measurements were performed with time-resolved laser-induced fluorescence techniques for 24 levels of Nd ii in the energy range 20 500–32 500 cm−1 . For 17 levels, no previous experimental data exist. These results have allowed the testing of new theoretical calculations with the relativistic Hartree–Fock method taking configuration interactions and core-polarization effects into account, and a satisfying agreement has been found for this complex ion. A new set of calculated oscillator strengths, accurate within a few per cent for the strongest transitions, is presented for 107 lines of astrophysical interest appearing in the wavelength range 358.0–1100.0 nm. These results will be useful to evaluate abundance values of neodymium in chemically peculiar stars in relation with cosmochronology. 相似文献
123.
We present four epochs of observations of the Galactic X-ray binarySS433 using the Australian Telescope Compact Array (ATCA). These observations, taken on 4 February, 29 February, 23 March and 27 June 2000, at four frequencies ranging from 1–9 Ghz, are used to monitor the circular polarised emission from the source. We obtain circular polarisation spectra for the first three epochs with spectralindices α, (m c ∝ν α), equal to 0.07±0.10, –1.07±0.09 and –0.18±0.05 and also observe a sign change in Stokes V. This change of handedness may indicate along-term restructuring of the magnetic field. 相似文献
124.
125.
126.
Summary ?The rare earth, major and trace element geochemistry of Jurassic deep marine manganese shales allow insight into their environment
of deposition. We present data of 24 samples from the Northern Calcareous Alps (Eastern Alps), collected from Late Jurassic
strata of the Tennengebirge and from Early Jurassic strata of the Karwendel Mts. Whereas major and trace element geochemistry
is controlled by the detrital input, rare earth element data and the relationship between total organic carbon and (pyritic)
sulfur can be used to constrain the origin of the manganese accumulation. The data of this study are compatible with a hydrogenous
precipitation of manganese by strongly varying redox-conditions at the sediment–water interface of a slope basin.
Received December 21, 2001; revised version accepted February 18, 2002 相似文献
127.
128.
129.
F. Marcolini G. Bigazzi F. P. Bonadonna E. Centamore R. Cioni G. Zanchetta 《第四纪科学杂志》2003,18(6):545-556
The stratigraphical context of two Middle Pleistocene fossiliferous palaeosols from Central Italy (Abruzzo and Tuscany) have been studied. Small mammals and molluscs occur in both palaeosols, which are covered by tephra layers that were analysed using an interdisciplinary approach. Application of fission‐track dating to apatites separated from the Case Picconetto tephra (Pescara, Abruzzo), yielded an age of 0.48 ± 0.04 Ma, indistinguishable from those previously determined for the Campani Quarry (Lower Valdarno, Tuscany) (0.46 ± 0.05 Ma and 0.48 ± 0.05 Ma). Geochemical and petrographic investigations indicate that these tephra originated from different volcanoes, the Alban Hills Volcanic Complex and the Vico Volcano (Latium) respectively. Small mammal and mollusc assemblages indicate different palaeoclimatic and palaeoenvironmental conditions for the Case Picconetto and Campani Quarry palaeosols. Warm and humid conditions can be inferred for the Campani Quarry site, whereas open and cold conditions can be inferred for Case Picconetto. On the basis of faunal data, fission‐track dates and attribution of tephra to specific volcanic eruptions, we suggest a correlation of these faunas with marine oxygen isotope stage 14 (Case Picconetto) and with marine oxygen isotope stage 11 (Campani Quarry), respectively. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
130.