全文获取类型
| 收费全文 | 36184篇 |
| 免费 | 6048篇 |
| 国内免费 | 7615篇 |
专业分类
| 测绘学 | 3462篇 |
| 大气科学 | 4873篇 |
| 地球物理 | 6608篇 |
| 地质学 | 19297篇 |
| 海洋学 | 3965篇 |
| 天文学 | 3363篇 |
| 综合类 | 2346篇 |
| 自然地理 | 5933篇 |
出版年
| 2024年 | 165篇 |
| 2023年 | 447篇 |
| 2022年 | 1215篇 |
| 2021年 | 1395篇 |
| 2020年 | 1282篇 |
| 2019年 | 1700篇 |
| 2018年 | 1191篇 |
| 2017年 | 1373篇 |
| 2016年 | 1400篇 |
| 2015年 | 1576篇 |
| 2014年 | 2025篇 |
| 2013年 | 2000篇 |
| 2012年 | 2160篇 |
| 2011年 | 2283篇 |
| 2010年 | 1968篇 |
| 2009年 | 2508篇 |
| 2008年 | 2439篇 |
| 2007年 | 2521篇 |
| 2006年 | 2461篇 |
| 2005年 | 2353篇 |
| 2004年 | 2037篇 |
| 2003年 | 1966篇 |
| 2002年 | 1653篇 |
| 2001年 | 1466篇 |
| 2000年 | 1503篇 |
| 1999年 | 1312篇 |
| 1998年 | 1116篇 |
| 1997年 | 792篇 |
| 1996年 | 671篇 |
| 1995年 | 596篇 |
| 1994年 | 543篇 |
| 1993年 | 443篇 |
| 1992年 | 317篇 |
| 1991年 | 271篇 |
| 1990年 | 181篇 |
| 1989年 | 142篇 |
| 1988年 | 119篇 |
| 1987年 | 66篇 |
| 1986年 | 38篇 |
| 1985年 | 32篇 |
| 1984年 | 18篇 |
| 1983年 | 15篇 |
| 1982年 | 11篇 |
| 1981年 | 9篇 |
| 1980年 | 8篇 |
| 1979年 | 5篇 |
| 1978年 | 14篇 |
| 1977年 | 5篇 |
| 1976年 | 4篇 |
| 1954年 | 7篇 |
排序方式： 共有10000条查询结果，搜索用时 46 毫秒
81.
82.
P. A. Patsis 《Monthly notices of the Royal Astronomical Society》2005,358(2):305-315
We investigate the morphological relation between the orbits of the central family of periodic orbits ( x 1 family) and the bar itself using models of test particles moving in a barred potential. We show that different bar morphologies may have as a backbone the same set of x 1 periodic orbits. We point out that by populating initially axisymmetric stellar discs exponentially with test particles in circular, or almost circular motion, we may end up with a response bar which reveals a shape different in crucial details from that of the individual stable x 1 orbits. For example, a bar model in which the x 1 orbits are pure ellipses may have a much more complicated response morphology. This depends on the particular invariant curves around x 1 , which are populated in each model. 相似文献
83.
国家重大科学工程项目LAMOST总控系统的程序设计是一个庞大的软件工程．其总控系统下共包括8个既相互独立又互有关联的子系统．如何通过良好的软件设计方法来处理好这8个子系统之间的关系使其协调运转，以及如何确保软件开发的可维护性、可持续性是研究重点． 相似文献
84.
85.
86.
V. Castellani S. Degl'Innocenti P. G. Prada Moroni 《Monthly notices of the Royal Astronomical Society》2001,320(1):66-72
We compare theoretical stellar models for main sequence (MS) stars with the Hipparcos data base for the Hyades cluster to give a warning against the uncritical use of available theoretical scenarios and to show how formal MS fittings can be fortuitous if not fictitious. Moreover, we find that none of the current theoretical scenarios appears able to account for an observed mismatch between theoretical predictions and observations of the coolest Hyades MS stars. Finally, we show that current theoretical models probably give too faint He burning luminosities unlike the case of less massive He burning models, with degenerate progenitors, which have been suggested to suffer the opposite discrepancy. 相似文献
87.
88.
89.
The biomass of macro- and interstitial fauna on clean and wrack-covered beaches in Western Australia
Anton McLachlan 《Estuarine, Coastal and Shelf Science》1985,21(4):587-599
The benthic faunal spectrum including bacteria, protozoans, meiofauna, wrack epifauna and macrofauna, was quantitatively surveyed on two modally reflective, moderate energy, Western Australian beaches. The more exposed beach had coarser sand, no intertidal macrofauna and a poor interstitial fauna. The less exposed beach had a large deposit of wrack totalling 161 kg m?1 dry mass concentrated on the lower shore. The amphipod Allorchestes compressa was abundant in the fresh wrack comprising most of the macrofauna. There were also fairly abundant small epifauna on the wrack. Dry biomass of macrofauna, epifauna, meiofauna, protozoans and bacteria was 0, 0, 15, 4 and 180 g m?1 on the more exposed beach and 160, 3, 112, 9 and 901 g m?1 on the less exposed beach with wrack. On the latter beach there was an inverse correlation between meiofaunal densities and the densities of protozoans and bacteria, suggesting grazing by the former on the latter. On both beaches meiofauna was concentrated in the mid- to upper beach, protozoans near the surface and bacteria in the mid- to lower beach. It is estimated that bacteria are responsible for most of the secondary production on both beaches. 相似文献
90.
Sunetra Giridhar N. Kameswara Rao David L. Lambert 《Journal of Astrophysics and Astronomy》1996,17(1-2):23-40
Two high resolution spectra of the hot RCrB star DY Cen in the red region are compared. The photospheric absorption lines
show a radial velocity variation of 12 kms-1 between 1989 July and 1992 May. Emission components to some CII lines present
in 1989 are almost entirely absent in 1992. Nebular forbidden lines of [OI], [NII] and [SII] appear unchanged from 1989 to
1992 相似文献