全文获取类型
收费全文 | 5046篇 |
免费 | 430篇 |
国内免费 | 682篇 |
专业分类
测绘学 | 483篇 |
大气科学 | 255篇 |
地球物理 | 847篇 |
地质学 | 1323篇 |
海洋学 | 1186篇 |
天文学 | 1446篇 |
综合类 | 230篇 |
自然地理 | 388篇 |
出版年
2024年 | 27篇 |
2023年 | 81篇 |
2022年 | 87篇 |
2021年 | 142篇 |
2020年 | 159篇 |
2019年 | 179篇 |
2018年 | 124篇 |
2017年 | 159篇 |
2016年 | 168篇 |
2015年 | 197篇 |
2014年 | 242篇 |
2013年 | 249篇 |
2012年 | 222篇 |
2011年 | 260篇 |
2010年 | 217篇 |
2009年 | 351篇 |
2008年 | 343篇 |
2007年 | 356篇 |
2006年 | 362篇 |
2005年 | 277篇 |
2004年 | 277篇 |
2003年 | 241篇 |
2002年 | 215篇 |
2001年 | 192篇 |
2000年 | 195篇 |
1999年 | 179篇 |
1998年 | 175篇 |
1997年 | 67篇 |
1996年 | 62篇 |
1995年 | 58篇 |
1994年 | 62篇 |
1993年 | 33篇 |
1992年 | 27篇 |
1991年 | 25篇 |
1990年 | 23篇 |
1989年 | 21篇 |
1988年 | 11篇 |
1987年 | 14篇 |
1986年 | 11篇 |
1985年 | 21篇 |
1984年 | 18篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1978年 | 3篇 |
1976年 | 1篇 |
排序方式: 共有6158条查询结果,搜索用时 15 毫秒
31.
32.
Robert R. Twilley 《Estuarine, Coastal and Shelf Science》1985,20(5):543-557
The magnitude and seasonality of organic carbon exchange was estimated for two basin mangrove forests in Rookery Bay, Florida. Runoff and tidal inundation in the forests were seasonal with half the annual total of each occurring from August to October. In each forest there were 152 tides yr?1 with a cumulative depth of about 12 m. Total organic carbon increased in bay waters exporting from the mangroves following a flood tide and peak concentrations were associated with export due to rainfall. The amount of net export from each basin forest was similar, although the concentration of organic carbon in each were different. Monthly net organic carbon export was proportional to the cumulative tidal amplitude within the forest. Total organic carbon export was 64 gC m?2 yr?1 and DOC was 75% of the total. A comparison of organic carbon export among riverine, fringe and basin mangroves suggests that tidal hydrology influences the proportion of litter fall that is exported from mangroves; and the magnitude of this organic carbon export from mangroves is related to the cumulative tidal amplitude within the forests. 相似文献
33.
Andreas Burkert 《Astrophysics and Space Science》2003,284(2):697-700
The puzzling correlation between the spin parameter λ of galactic disks and the disk-to-halo mass fraction f
disk is investigated. It is shown that such a correlation arises naturally from large uncertainties in determining the virial
masses of dark matter halos. This result indicates that halo properties derived from fits to observed rotation curves are
still very uncertain. An analysis of λ versus f
disk as function of the adopted halo virial mass shows that for reasonable halo concentrations f
disk ≈ 0.01 - 0.07 which is significantly smaller than the universal baryon fraction. Most of the available gas either never settled
into the galactic disks or was ejected subsequently.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
34.
35.
We present observations of a sample of Herbig AeBe stars, as well as the FU Orionis object V1057 Cygni. Our K-band (2.2μm)
observations from the Palomar Testbed Interferometer (PTI) used baselines of 110 m and 85 m, resulting in fringe spacings
of ∼4 mas and 5 mas, respectively. Fringes were obtained for the first time on V1057 Cygnias well as V594 Cas. Additional
measurements were made of MWC147, while upper limits to visibility-squared are obtained for MWC297, HD190073, and MWC614.
These measurements are sensitive to the distribution of warm, circumstellar dust in these sources. If the circumstellar infrared
emission comes from warm dust in a disk, the inclination of the disk to the line of sight implies that the observed interferometric
visibilities should depend upon hour angle. Surprisingly, the observations of Millan-Gabet, Schloerb and Traub (2001)(hereafter
MST) did not show significant variation with hour angle. However, limited sampling of angular frequencies on the sky was possible
with the IOTA interferometer, motivating us to study a subset of their objects to further constrain these systems.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
36.
37.
38.
39.
40.
Fabio Fontanot Pierluigi Monaco Stefano Borgani 《Monthly notices of the Royal Astronomical Society》2003,341(2):692-706
We apply the ztrace algorithm to the optical NOG and infrared PSC z galaxy catalogues to reconstruct the pattern of primordial fluctuations that have generated our local Universe. We check that the density fields traced by the two catalogues are well correlated, and consistent with a linear relation [either in δ or in log (1 +δ) ] with relative bias (of NOG with respect to PSC z ) b rel = 1.1 ± 0.1 . The relative bias relation is used to fill the optical zone of avoidance at | b | < 20° using the PSC z galaxy density field.
We perform extensive testing on simulated galaxy catalogues to optimize the reconstruction. The quality of the reconstruction is predicted to be good at large scales, up to a limiting wavenumber klim ≃ 0.4 h Mpc−1 beyond which all information is lost. We find that the improvement arising from the denser sampling of the optical catalogue is compensated by the uncertainties connected to the larger zone of avoidance.
The initial conditions reconstructed from the NOG catalogue are found (analogously to those from the PSC z ) to be consistent with a Gaussian paradigm. We use the reconstructions to produce sets of initial conditions ready to be used for constrained simulations of our local Universe. 相似文献
We perform extensive testing on simulated galaxy catalogues to optimize the reconstruction. The quality of the reconstruction is predicted to be good at large scales, up to a limiting wavenumber k
The initial conditions reconstructed from the NOG catalogue are found (analogously to those from the PSC z ) to be consistent with a Gaussian paradigm. We use the reconstructions to produce sets of initial conditions ready to be used for constrained simulations of our local Universe. 相似文献