全文获取类型
收费全文 | 5281篇 |
免费 | 465篇 |
国内免费 | 721篇 |
专业分类
测绘学 | 513篇 |
大气科学 | 362篇 |
地球物理 | 839篇 |
地质学 | 1550篇 |
海洋学 | 408篇 |
天文学 | 1539篇 |
综合类 | 259篇 |
自然地理 | 997篇 |
出版年
2024年 | 19篇 |
2023年 | 58篇 |
2022年 | 118篇 |
2021年 | 105篇 |
2020年 | 131篇 |
2019年 | 177篇 |
2018年 | 126篇 |
2017年 | 145篇 |
2016年 | 170篇 |
2015年 | 169篇 |
2014年 | 201篇 |
2013年 | 264篇 |
2012年 | 215篇 |
2011年 | 205篇 |
2010年 | 177篇 |
2009年 | 339篇 |
2008年 | 379篇 |
2007年 | 386篇 |
2006年 | 383篇 |
2005年 | 309篇 |
2004年 | 287篇 |
2003年 | 269篇 |
2002年 | 255篇 |
2001年 | 226篇 |
2000年 | 200篇 |
1999年 | 221篇 |
1998年 | 194篇 |
1997年 | 103篇 |
1996年 | 91篇 |
1995年 | 92篇 |
1994年 | 73篇 |
1993年 | 81篇 |
1992年 | 61篇 |
1991年 | 38篇 |
1990年 | 46篇 |
1989年 | 39篇 |
1988年 | 30篇 |
1987年 | 30篇 |
1986年 | 15篇 |
1985年 | 12篇 |
1984年 | 6篇 |
1983年 | 2篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1972年 | 1篇 |
1954年 | 3篇 |
排序方式: 共有6467条查询结果,搜索用时 0 毫秒
101.
In this paper a slightly different approach is proposed for the process of determining the functions S
m
and H
m
* of the algorithm of the canonical version of Hori method. This process will be referred to as integration theory of the mth order equation of the method. It will be shown that the ordinary differential equation with an auxiliary parameter t
* as independent variable, introduced through Hori auxiliary system, can be replaced by a partial differential equation in the time t. In this way, the mth order equation of the algorithm assumes a form very similar to the one of other perturbation methods. In virtue of this new approach of the integration theory for Hori method, Lagrange's variational equations introduced by Sessin are revised. As an example, the Duffing equation is solved through this new approach. 相似文献
102.
103.
104.
105.
106.
107.
108.
109.
Licia Verde Limin Wang Alan F. Heavens Marc Kamionkowski 《Monthly notices of the Royal Astronomical Society》2000,313(1):141-147
Cosmic microwave background and large-scale structure data will shortly improve dramatically with the Microwave Anisotropy Probe and Planck Surveyor , and the Anglo-Australian 2-Degree Field and Sloan Digital Sky Survey. It is therefore timely to ask which of the microwave background and large-scale structure will provide a better probe of primordial non-Gaussianity. In this paper we consider this question, using the bispectrum as a discriminating statistic. We consider several non-Gaussian models and find that in each case the microwave background will provide a better probe of primordial non-Gaussianity. Our results suggest that if microwave background maps appear Gaussian, then apparent deviations from Gaussian initial conditions in galaxy surveys can be attributed with confidence to the effects of biasing. We demonstrate this precisely for the spatial bispectrum induced by local non-linear biasing. 相似文献
110.
We investigate the behaviour of galaxy clustering on large scales using the PSC z catalogue. In particular, we ask whether there is any evidence of large-scale fractal behaviour in this catalogue. We find the correlation dimension in this survey varies with scale, consistent with other analyses. For example, our results on small and intermediate scales are consistent those obtained from the QDOT sample, but the larger PSC z sample allows us to extend the analysis out to much larger scales. We find firm evidence that the sample becomes homogeneous at large scales; the correlation dimension of the sample is D 2 =2.992±0.003 for r >30 h −1 Mpc. This provides strong evidence in favour of a universe that obeys the cosmological principle. 相似文献