全文获取类型
收费全文 | 1633篇 |
免费 | 34篇 |
国内免费 | 7篇 |
专业分类
测绘学 | 39篇 |
大气科学 | 177篇 |
地球物理 | 290篇 |
地质学 | 466篇 |
海洋学 | 178篇 |
天文学 | 358篇 |
自然地理 | 166篇 |
出版年
2021年 | 12篇 |
2020年 | 10篇 |
2019年 | 15篇 |
2018年 | 19篇 |
2017年 | 17篇 |
2016年 | 39篇 |
2015年 | 38篇 |
2014年 | 26篇 |
2013年 | 115篇 |
2012年 | 50篇 |
2011年 | 65篇 |
2010年 | 29篇 |
2009年 | 67篇 |
2008年 | 76篇 |
2007年 | 72篇 |
2006年 | 76篇 |
2005年 | 55篇 |
2004年 | 60篇 |
2003年 | 59篇 |
2002年 | 65篇 |
2001年 | 51篇 |
2000年 | 35篇 |
1999年 | 45篇 |
1998年 | 31篇 |
1997年 | 27篇 |
1996年 | 22篇 |
1995年 | 26篇 |
1994年 | 18篇 |
1993年 | 19篇 |
1992年 | 17篇 |
1991年 | 13篇 |
1990年 | 24篇 |
1989年 | 17篇 |
1988年 | 10篇 |
1987年 | 20篇 |
1986年 | 12篇 |
1985年 | 32篇 |
1984年 | 31篇 |
1983年 | 18篇 |
1982年 | 15篇 |
1981年 | 19篇 |
1980年 | 13篇 |
1979年 | 19篇 |
1978年 | 22篇 |
1977年 | 22篇 |
1976年 | 13篇 |
1975年 | 12篇 |
1974年 | 23篇 |
1973年 | 17篇 |
1969年 | 10篇 |
排序方式: 共有1674条查询结果,搜索用时 0 毫秒
81.
The "Little Ice Age": Local and Global Perspectives 总被引:3,自引:0,他引:3
82.
Velocity images from stacking depth-slowness seismic wavefields 总被引:1,自引:0,他引:1
Geraint D. Jones Penny J. Barton Satish C. Singh 《Geophysical Journal International》2007,168(2):583-592
83.
84.
A.W. Jones R.J. Davis A. Wilkinson G. Giardino S.J. Melhuish H. Asareh R.D. Davies A.N. Lasenby 《Monthly notices of the Royal Astronomical Society》2001,327(2):545-551
We present the joint analysis of two 5-GHz interferometric surveys of the northern sky, taken with different baselines. The two surveys were carried out on the Jodrell Bank 5-GHz interferometer based at Manchester. The Maximum Entropy Method is used to check the consistency of the two surveys and the final two-dimensional maps are used, together with low-frequency full sky surveys, to put constraints on the Galactic spectral index. It is found that synchrotron emission is the dominant process at high Galactic latitudes below 5 GHz. 相似文献
85.
86.
Thomas A. Jones 《Mathematical Geology》1977,9(6):635-647
It is becoming increasingly important to determine probability distributions of combinations of random variables. Convolution is a technique by which the distribution of a sum of random variables can be determined. This paper presents some simplifications in order to reduce the numerical integrations and computer time. In addition, the method may be used with empirical nonanalytic distributions. While Monte Carlo methods are also appropriate for calculating the distribution, convolution can give at least as much accuracy as Monte Carlo methods with a reduction in computation. Two applications are presented: one approximates the distribution of percent sand in an area, and the other indicates a method of determining sample size when using the distribution of means to approximate normality. 相似文献
87.
88.
89.
90.
Giant ground figures are widespread in the lower Colorado River area of southwestern North America, yet their chronology has remained unconstrained by numerical ages. Thirteen AMS 14C measurements reported here indicate that geoglyphs were made from before ˜A. D. 1200 to before ˜900 B. C. We account for potential contamination from prior organics in weathering rinds. All other potential errors point to 14C dates being minimum-limiting ages for the manufacturing of geoglyphs. Although these ages indicate considerable chronological complexity among geoglyphs, our data are consistent with the linguistic hypothesis that the Yuman people in the desert of southeastern California migrated from Baja California—rather than from the north. These results must, however, be placed under the cloud of uncertainty that hangs over the entire field of AMS dating of rock art: the untested assumption surrounding contemporeneity of organics in a surface context. © 1995 John Wiley & Sons, Inc. 相似文献