全文获取类型
收费全文 | 36521篇 |
免费 | 6037篇 |
国内免费 | 7825篇 |
专业分类
测绘学 | 3349篇 |
大气科学 | 4607篇 |
地球物理 | 6628篇 |
地质学 | 19692篇 |
海洋学 | 4197篇 |
天文学 | 4006篇 |
综合类 | 2293篇 |
自然地理 | 5611篇 |
出版年
2024年 | 183篇 |
2023年 | 436篇 |
2022年 | 1178篇 |
2021年 | 1379篇 |
2020年 | 1296篇 |
2019年 | 1679篇 |
2018年 | 1176篇 |
2017年 | 1381篇 |
2016年 | 1401篇 |
2015年 | 1558篇 |
2014年 | 2007篇 |
2013年 | 2055篇 |
2012年 | 2122篇 |
2011年 | 2331篇 |
2010年 | 2031篇 |
2009年 | 2568篇 |
2008年 | 2524篇 |
2007年 | 2561篇 |
2006年 | 2464篇 |
2005年 | 2401篇 |
2004年 | 2082篇 |
2003年 | 1969篇 |
2002年 | 1672篇 |
2001年 | 1486篇 |
2000年 | 1499篇 |
1999年 | 1328篇 |
1998年 | 1138篇 |
1997年 | 806篇 |
1996年 | 673篇 |
1995年 | 576篇 |
1994年 | 539篇 |
1993年 | 452篇 |
1992年 | 321篇 |
1991年 | 282篇 |
1990年 | 197篇 |
1989年 | 164篇 |
1988年 | 133篇 |
1987年 | 73篇 |
1986年 | 43篇 |
1985年 | 40篇 |
1984年 | 33篇 |
1983年 | 26篇 |
1982年 | 16篇 |
1981年 | 18篇 |
1980年 | 12篇 |
1979年 | 8篇 |
1978年 | 16篇 |
1977年 | 9篇 |
1976年 | 7篇 |
1954年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
42.
Larisa A. Yakovina Yakiv V. Pavlenko Carlos Abia 《Astrophysics and Space Science》2003,288(3):279-286
Lithium abundances in the atmospheres of the super Li-rich C-giants WZ Cas and WX Cyg are derived by the spectral synthesis
technique using the Li I resonance line at λ670.8 nm and three subordinate lines at λλ 812.6, 610.4 and 497.2 nm. The differences
between the Li abundances derived from the λ670.8 nm line and the λλ 497.2, 812.6 nm lines do not exceed ±0.5 dex. The lithium
line at λ610.4 nm provides typically lower abundances than the resonance line (by ≈ 1 dex). The mean LTE and NLTE Li abundances
from three Li I lines (excluding λ610.4 nm) are 4.7, 4.9 for WZ Cas, and 4.6, 4.8 for WX Cyg, respectively.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
43.
韩玲 《地球科学与环境学报》2003,25(1):74-75
提出了一种基于格网DEM的粗差检测及剔除方法,其基本思想是对每个表面上的点,在坡度上,高程或突变量引起的形状不连续,可能被怀疑有误差,通过坡度上每个点,应用坡度逼近或改变量来计算,考虑坡度变化的相对值,并以这些相对值计算一个统计值为判断该点合法性的阈值,使计算结果更为可靠。 相似文献
44.
45.
46.
We consider the effects of projection, internal absorption, and gas-or stellar-velocity dispersion on the measured rotation curves of galaxies with edge-on disks. Axisymmetric disk models clearly show that the rotational velocity in the inner galaxy is highly underestimated. As a result, an extended portion that imitates nearly rigid rotation appears. At galactocentric distances where the absorption is low (i.e., it does not exceed 0.3–0.5m kpc?1), the line profiles can have two peaks, and a rotation curve with minimum distortions can be obtained by estimating the position of the peak that corresponds to a higher rotational velocity. However, the high-velocity peak disappears in high-absorption regions and the actual shape of the rotation curve cannot be reproduced from line-of-sight velocity estimates. In general, the optical rotation curves for edge-on galaxies are of little use in reconstructing the mass distribution in the inner regions, particularly for galaxies with a steep velocity gradient in the central region. In this case, estimating the rotation velocities for outer (transparent) disk regions yields correct results. 相似文献
47.
48.
M.P. Collings J.W. Dever H.J. Fraser M.R.S. McCoustra 《Astrophysics and Space Science》2003,285(3-4):633-659
The interaction of carbon monoxide (CO) with vapour-deposited water(H2O) ices has been studied using temperature programmed desorption (TPD) and Fourier transform reflection-absorption infrared
spectroscopy (FT-RAIRS) over a range of astrophysically relevant temperatures. Such measurements have shown that CO desorption
from amorphous H2Oices is a much more complex process than current astrochemical models suggest. Re-visiting previously reported laboratory
experiments (Collings et al., 2003), a rate model has been constructed to explain, in a phenomenological manner, the desorption
of CO over astronomically relevant time scales. The model presented here can be widely applied to a range of astronomical
environments where depletion of CO from the gas phase is relevant. The model accounts for the two competing processes of CO
desorption and migration, and also enables the entrapment of some of the CO in the ice matrix and its subsequent release as
the water ice crystallises and then desorbs. The astronomical implications of this model are discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
49.
50.
DEVELOPMENTSTRATEGIESOFWATERANDLANDRESOURCESINTHEHEXIREGION,CHINA肖洪浪,高前兆,李福兴DEVELOPMENTSTRATEGIESOFWATERANDLANDRESOURCESINTHE... 相似文献