全文获取类型
收费全文 | 1786篇 |
免费 | 66篇 |
国内免费 | 26篇 |
专业分类
测绘学 | 62篇 |
大气科学 | 142篇 |
地球物理 | 377篇 |
地质学 | 587篇 |
海洋学 | 126篇 |
天文学 | 425篇 |
综合类 | 8篇 |
自然地理 | 151篇 |
出版年
2022年 | 23篇 |
2021年 | 23篇 |
2020年 | 29篇 |
2019年 | 24篇 |
2018年 | 54篇 |
2017年 | 58篇 |
2016年 | 40篇 |
2015年 | 42篇 |
2014年 | 51篇 |
2013年 | 90篇 |
2012年 | 47篇 |
2011年 | 72篇 |
2010年 | 77篇 |
2009年 | 83篇 |
2008年 | 79篇 |
2007年 | 81篇 |
2006年 | 72篇 |
2005年 | 53篇 |
2004年 | 58篇 |
2003年 | 43篇 |
2002年 | 64篇 |
2001年 | 30篇 |
2000年 | 45篇 |
1999年 | 25篇 |
1998年 | 33篇 |
1997年 | 30篇 |
1996年 | 19篇 |
1995年 | 28篇 |
1994年 | 15篇 |
1993年 | 19篇 |
1992年 | 29篇 |
1991年 | 18篇 |
1990年 | 18篇 |
1989年 | 12篇 |
1988年 | 12篇 |
1987年 | 24篇 |
1986年 | 23篇 |
1985年 | 26篇 |
1984年 | 33篇 |
1983年 | 31篇 |
1982年 | 36篇 |
1981年 | 26篇 |
1980年 | 27篇 |
1979年 | 22篇 |
1978年 | 10篇 |
1977年 | 15篇 |
1976年 | 18篇 |
1974年 | 16篇 |
1973年 | 9篇 |
1971年 | 9篇 |
排序方式: 共有1878条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
R. P. Kane 《Solar physics》2006,233(1):107-115
This paper examines the variations of coronal mass ejections (CMEs) and interplanetary CMEs (ICMEs) during solar cycle 23
and compares these with those of several other indices. During cycle 23, solar and interplanetary parameters had an increase
from 1996 (sunspot minimum) to ∼2000, but the interval 1998–2002 had short-term fluctuations. Sunspot numbers had peaks in
1998, 1999, 2000 (largest), 2001 (second largest), and 2002. Other solar indices had matching peaks, but the peak in 2000
was larger than the peak in 2001 only for a few indices, and smaller or equal for other solar indices. The solar open magnetic
flux had very different characteristics for different solar latitudes. The high solar latitudes (45∘–90∘) in both N and S hemispheres had flux evolutions anti-parallel to sunspot activity. Fluxes in low solar latitudes (0∘–45∘) evolved roughly parallel to sunspot activity, but the finer structures (peaks etc. during sunspot maximum years) did not
match with sunspot peaks. Also, the low latitude fluxes had considerable N–S asymmetry. For CMEs and ICMEs, there were increases
similar to sunspots during 1996–2000, and during 2000–2002, there was good matching of peaks. But the peaks in 2000 and 2001
for CMEs and ICMEs had similar sizes, in contrast to the 2000 peak being greater than the 2001 peak for sunspots. Whereas
ICMEs started decreasing from 2001 onwards, CMEs continued to remain high in 2002, probably due to extra contribution from
high-latitude prominences, which had no equivalent interplanetary ICMEs or shocks. Cosmic ray intensity had features matching
with those of sunspots during 2000–2001, with the 2000 peak (on a reverse scale, actually a cosmic ray decrease or trough)
larger than the 2001 peak. However, cosmic ray decreases started with a delay and ended with a delay with respect to sunspot
activity. 相似文献
5.
Viviane Pierrard Milan Maksimovic Joseph Lemaire 《Astrophysics and Space Science》2001,277(1-2):195-200
Electron velocity distribution functions (VDF) observed in the low speed solar wind flow are generally characterized by ‘core’
and ‘halo’ electrons. In the high speed solar wind, a third population of ‘strahl’ electrons is generally observed. New collisional
models based on the solution of the Fokker-Planck equation can be used to determine the importance of the different electron
populations as a function of the radial distance. Typical electron velocity distribution functions observed at 1 AU from the
Sun are used as boundary conditions for the high speed solar wind and for the low speed solar wind. Taking into account the
effects of external forces and Coulomb collisions with a background plasma, suprathermal tails are found to be present in
the electron VDF at low altitudes in the corona when they exist at large radial distances.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
We show how the Yarkovsky effect can be understood as a heat engine. The output of the engine, manifested in the rate of change in semimajor axis of the body, has a maximum at an intermediate heat capacity, depending on the rotation rate of the body. This maximum arises because the work output depends on the product of the solar heat absorbed by the body and transported from its morning to evening side (this am-pm heat flux increases with heat capacity) and the Carnot efficiency (which declines with heat capacity). 相似文献
7.
8.
This paper considers the problem of estimatingm, the number of components in a finite mixture of distributions from a parametric family. A step-up procedure using the bootstrap method is proposed. Some properties of the procedure are illustrated with simulation studies. An example of the method, applied to orientation of beach clasts, is given. 相似文献
9.
Topographic features affect the scattering properties of planetary surfaces by casting shadows and altering the local incidence and emission angles. Measurements of this phenomenon were obtained on the Cornell goniometer for both high and low albedo surfaces. For the low albedo surface, the decrease in reflected radiation due to topography increases sharply with increasing phase angle, whereas for the high albedo sample the effects are approximately constant between phase angles of 30 and 70°. The observations are in good agreement with a theoretical model in the case of the dark surface. However, for the high albedo surface the model overestimates the effects by about a factor of 2, since it does not include the partial illumination of shadows by multiple scattering. For both high and low albedo surfaces, the effects of topography do not become significant until a phase angle of 30–40°. 相似文献
10.
Resonant absorption of MHD waves on a nonuniform flux tube is investigated as a driven problem for a 1D cylindrical equilibrium. The variation of the fractional absorption is studied as a function of the frequency and its relation to the eigenvalue problem of the MHD radiating eigenmodes of the nonuniform flux tube is established. The optimal frequencies producing maximal fractional absorption are determined and the condition for total absorption is obtained. This condition defines an impedance matching and is fulfilled for an equilibrium that is fine tuned with respect to the incoming wave. The variation of the spatial wave solutions with respect to the frequency is explained as due to the variation of the real and imaginary parts of the dispersion relation of the MHD radiating eigenmodes with respect to the real driving frequency. 相似文献