全文获取类型
收费全文 | 369篇 |
免费 | 6篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 11篇 |
大气科学 | 29篇 |
地球物理 | 81篇 |
地质学 | 141篇 |
海洋学 | 22篇 |
天文学 | 71篇 |
综合类 | 1篇 |
自然地理 | 22篇 |
出版年
2019年 | 3篇 |
2017年 | 3篇 |
2016年 | 13篇 |
2014年 | 4篇 |
2013年 | 17篇 |
2012年 | 5篇 |
2011年 | 11篇 |
2010年 | 14篇 |
2009年 | 14篇 |
2008年 | 13篇 |
2007年 | 14篇 |
2006年 | 7篇 |
2005年 | 5篇 |
2004年 | 7篇 |
2003年 | 9篇 |
2002年 | 3篇 |
2001年 | 9篇 |
2000年 | 6篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1990年 | 4篇 |
1989年 | 9篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 13篇 |
1979年 | 7篇 |
1978年 | 9篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1971年 | 4篇 |
1970年 | 5篇 |
1969年 | 3篇 |
1968年 | 5篇 |
1965年 | 3篇 |
1962年 | 3篇 |
1948年 | 3篇 |
1905年 | 2篇 |
排序方式: 共有378条查询结果,搜索用时 15 毫秒
61.
62.
Herbert A. Beebe 《Solar physics》1971,17(2):304-315
The formation of the solar Caii K-line core is studied under the assumption of a two component chromosphere for many atmosphere models, which are tested by comparing observed and calculated average intensity profiles at several places on the solar disk. Non-LTE-line profile calculations are made using model atoms of two and three bound levels while the value and depth of the temperature minimum and turbulent velocity gradient are varied. A critique of several broad types of models is provided.Limb darkening of the entire core, a K1 radiation temperature of 4300 K and increasing limbward separation of the K2 peaks are predicted by a combination of a cool component, covering 90% of the solar disk, and a hot component, representing the bright calcium network. The optimum cool component is characterized by a 4200 K temperature minimum and low ( 1 km/sec) microturbulent velocities. The hot component begins its outward temperature rise in the photosphere at 4300 K and is never more than 500 K hotter than the cool component.Publications of the Goethe Link Observatory, Indiana University, No. 116.Presently at New Mexico State University, Las Cruces, New Mexico. 相似文献
63.
Earlier analyses of the Pioneer 8 and 9 experimental meteoroid data have shown that the detectors on these two spacecraft are intercepting meteoroids with hyperbolic orbital parameters. It is shown in this paper that these results are entirely consistent with and, indeed, to be expected from other observations of the interplanetary meteoroid complex. Collisional breakup of meteoroids and post-collision radiation pressure modification of their orbits is found to be a sufficient cause for the observed results. Details of the calculations as well as of the results are presented. 相似文献
64.
Copper concentrations in surface waters off the southeastern United States coast range from 0.02 to 0.33 μg/kg (0.3–5.2 nmol/kg). Mean concentrations are lowest in Onslow Bay (0.07 μg/kg) and highest over the Blake Plateau (0.20 μg/kg). An explanation, compatible with the hydrography and hydrodynamics of the area, is proposed for the observed regional variations. 相似文献
65.
Testing the theoretical notion that differences in entrepreneurial skill can enhance the viability of a poor location or detract from the qualities of a good location, this study reviews the historical experience of a number of retailing establishments operated by different firms at the same sites. The ultimate success of stores that had done poorly under previous management tends to confirm that a location is “good'’only so long as the retailer employs effective merchandising and operating policies. 相似文献
66.
Herbert Knothe 《Celestial Mechanics and Dynamical Astronomy》1969,1(1):36-45
In an axially symmetric three-dimensional Riemann-spaceg ik(u 1,u 2)?u 3 represents the cyclic parameter-, a gravitational potential ?(u 1,u 2) is given. For all masspoints with equal total energy and equal angular momentum there exists a function Ψ(u 1,u 2) by means of which the equations of motion can be reduced to a simple ordinary second-order differential equation. The function ? can be interpreted as the velocity with which the masspoint moves in the two-dimensional spaceu 1,u 2. Of particular interest is the case where the spaceu 1,u 2,u 3 is Euclidean. Ifu 1,u 2 are Cartesian coordinates in a planeu 3=const., and if the tangent vector of the trajectoryu 1(t)u 2(t) has the components cosω, sinω it is shown that the triple integral $$\smallint \smallint \smallint \psi du^1 du^2 d\omega $$ is an invariant integral in Cartan's sense, in other words, if the integral is extended over a domain in a meridian plane at timet=0, it keeps its value at any time. 相似文献
67.
68.
Ohne Zusammenfassung 相似文献
69.
The compact source 0125 + 628 in the centre of the galactic supernova remnant G 127.1 + 0.5 has been re-observed in HI absorption
using the Westerbork Synthesis Radio Telescope (WSRT). The outer arm HI absorption atV = -95km s-1 has been confirmed. The absorption spectrum is similar to that of the nearby extragalactic source 0123 + 633. We discuss
the arguments concerning an extragalactic origin of 0125 + 628 and conclude that it is most likely extragalactic and not an
SS 433 type object.
The National Radio Astronomy Observatory is operated by Associated Universities Inc. under contract with the National Science
Foundation. 相似文献
70.