全文获取类型
收费全文 | 6556篇 |
免费 | 195篇 |
国内免费 | 63篇 |
专业分类
测绘学 | 135篇 |
大气科学 | 549篇 |
地球物理 | 1519篇 |
地质学 | 2203篇 |
海洋学 | 630篇 |
天文学 | 1066篇 |
综合类 | 14篇 |
自然地理 | 698篇 |
出版年
2021年 | 54篇 |
2020年 | 72篇 |
2019年 | 84篇 |
2018年 | 118篇 |
2017年 | 122篇 |
2016年 | 145篇 |
2015年 | 122篇 |
2014年 | 143篇 |
2013年 | 342篇 |
2012年 | 192篇 |
2011年 | 271篇 |
2010年 | 258篇 |
2009年 | 267篇 |
2008年 | 274篇 |
2007年 | 228篇 |
2006年 | 246篇 |
2005年 | 201篇 |
2004年 | 208篇 |
2003年 | 185篇 |
2002年 | 192篇 |
2001年 | 133篇 |
2000年 | 125篇 |
1999年 | 118篇 |
1998年 | 104篇 |
1997年 | 97篇 |
1996年 | 100篇 |
1995年 | 106篇 |
1994年 | 98篇 |
1993年 | 81篇 |
1992年 | 89篇 |
1991年 | 77篇 |
1990年 | 100篇 |
1989年 | 88篇 |
1988年 | 79篇 |
1987年 | 106篇 |
1986年 | 79篇 |
1985年 | 101篇 |
1984年 | 141篇 |
1983年 | 114篇 |
1982年 | 106篇 |
1981年 | 109篇 |
1980年 | 97篇 |
1979年 | 115篇 |
1978年 | 81篇 |
1977年 | 94篇 |
1976年 | 80篇 |
1975年 | 80篇 |
1974年 | 61篇 |
1973年 | 74篇 |
1972年 | 42篇 |
排序方式: 共有6814条查询结果,搜索用时 338 毫秒
901.
902.
Robert C. Fleck Jr. 《Astrophysics and Space Science》1984,100(1-2):417-419
Two comments are prompted by the recent paper of Quiroga (1983). First, it is pointed out that Quiroga's identification of two distinct types of motion (hydrodynamic and turbulent) within the galactic disk supports the suggestion that turbulent motions in the Galaxy are generated by the shearig action of differential galactic rotation. Secondly, as a result of these turbulent motions dominating the systematic hydrodynamics of galactic rotation at scale sizes below 100–300 pc, it appears that some process(es) associated with interstellar turbulence rather than with galactic rotation should play a dominant role in the establishment of the angular momentum of interstellar material. 相似文献
903.
904.
We study sudden brightenings of coronal loops that interconnect active regions. Such brightenings often occur within one or two days after the birth of a new interconnecting loop, as well as in some old interconnections. The brightenings of young loops are obviously associated with the emergence of new magnetic flux near their footpoints, whereas some enhancements of old loops may be triggered by slowly moving disturbances propagating from other centers of activity. A few loop brightenings are associated with flares, but the loop does not brighten in consequence of energy supply from the flare. Both the flare and the loop brightening are independent consequences of one common agent, presumably newly emerging flux.Temperatures in brightened loops are between 3 and 4 × 106 K and densities are < 2 × 109 cm–3, probably < 5 × 108 cm–3 in some old loops. The top part of a loop is the site of the most intense brightening in the initial phase of a loop enhancement. The most frequent lifetime of these brightenings is 6 to 7 hr.Hale Observatories are operated jointly by the Carnegie Institution of Washington and the California Institute of Technology. 相似文献
905.
906.
Solar Physics - A preliminary theoretical solar model is presented that produces closer agreement with observation than has been heretofore possible. The qualitative advantages and shortcomings of... 相似文献
907.
908.
909.
Eric F. Wood 《Advances in water resources》1978,1(5):299-305
Bayesian Inference and Decision Theory tools are applied to the problem of synthetic hydrology when model and parameter uncertainty exist. Issues such as optimal parameter estimation, use of synthetic generation in design problems, and the effects of parameter uncertainty on statistical estimation are discussed and applied to the problem of reservoir slorage-yield analysis. 相似文献
910.