全文获取类型
收费全文 | 12027篇 |
免费 | 2284篇 |
国内免费 | 2326篇 |
专业分类
测绘学 | 516篇 |
大气科学 | 1316篇 |
地球物理 | 4193篇 |
地质学 | 3595篇 |
海洋学 | 3263篇 |
天文学 | 1629篇 |
综合类 | 620篇 |
自然地理 | 1505篇 |
出版年
2024年 | 39篇 |
2023年 | 126篇 |
2022年 | 296篇 |
2021年 | 340篇 |
2020年 | 394篇 |
2019年 | 577篇 |
2018年 | 410篇 |
2017年 | 419篇 |
2016年 | 420篇 |
2015年 | 524篇 |
2014年 | 554篇 |
2013年 | 680篇 |
2012年 | 630篇 |
2011年 | 645篇 |
2010年 | 541篇 |
2009年 | 782篇 |
2008年 | 780篇 |
2007年 | 974篇 |
2006年 | 855篇 |
2005年 | 726篇 |
2004年 | 730篇 |
2003年 | 642篇 |
2002年 | 564篇 |
2001年 | 489篇 |
2000年 | 471篇 |
1999年 | 478篇 |
1998年 | 450篇 |
1997年 | 308篇 |
1996年 | 299篇 |
1995年 | 298篇 |
1994年 | 252篇 |
1993年 | 222篇 |
1992年 | 172篇 |
1991年 | 137篇 |
1990年 | 99篇 |
1989年 | 81篇 |
1988年 | 71篇 |
1987年 | 54篇 |
1986年 | 28篇 |
1985年 | 21篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1954年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Sergei A. Klioner 《Celestial Mechanics and Dynamical Astronomy》1996,66(4):345-363
Intermediate orbit for general planetary theory is constructed in the form of multivariate Fourier series with numerical coefficients. The structure and efficiency of the derived series are illustrated by giving various statistical properties of the coefficients.The ability of the recently proposed elliptic function approach to compress the Fourier series representing the intermediate orbit is investigated. Our results confirm that when mutual perturbations of a pair of planets are considered the elliptic function approach is quite efficient and allows one to compress the series substantially. However, when perturbations of three or more planets are under study the elliptic function approach does not give any advantages. 相似文献
12.
Stress wave attenuation across fractured rock masses is a great concern of underground structure safety. When the wave amplitude is large, fractures experience nonlinear deformation during the wave propagation. This paper presents a study on normal transmission of P‐wave across parallel fractures with nonlinear deformational behaviour (static Barton–Bandis model). The results show that the magnitude of transmission coefficient is a function of incident wave amplitude, nondimensional fracture spacing and number of fractures. Two important indices of nondimensional fracture spacing are identified, and they divide the area of nondimensional fracture spacing into three parts (individual fracture area, transition area and small spacing area). In the different areas, the magnitude of transmission coefficient has different trends with nondimensional fracture spacing and number of fractures. In addition, the study reveals that under some circumstances, the magnitude of transmission coefficient increases with increasing number of fractures, and is larger than 1. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
13.
14.
Hai-Ning LiNational Astronomical Observatories Chinese Academy of Sciences Beijing lhnDepartment of Astronomy Beijing Normal University Beijing 《中国天文和天体物理学报》2003,3(5)
We present a quantitative estimate of the relativistic corrections to the thermal SZ power spectrum produced by the energetic electrons in massive clusters. The corrections are well within 10% for current experiments with working frequencies below v < 100 GHz, but become non-negligible at high frequencies v > 350 GHz. Moreover, the corrections appear to be slightly smaller at higher l or smaller angular scales. We conclude that there is no need to include the relativistic corrections in the theoretical study of the SZ power spectrum especially at low frequencies unless the SZ power spectrum is used for precision cosmology. 相似文献
15.
16.
17.
18.
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
19.
20.
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