全文获取类型
收费全文 | 1300篇 |
免费 | 192篇 |
国内免费 | 196篇 |
专业分类
测绘学 | 152篇 |
大气科学 | 172篇 |
地球物理 | 372篇 |
地质学 | 346篇 |
海洋学 | 157篇 |
天文学 | 175篇 |
综合类 | 57篇 |
自然地理 | 257篇 |
出版年
2024年 | 7篇 |
2023年 | 9篇 |
2022年 | 28篇 |
2021年 | 38篇 |
2020年 | 48篇 |
2019年 | 53篇 |
2018年 | 31篇 |
2017年 | 40篇 |
2016年 | 56篇 |
2015年 | 42篇 |
2014年 | 77篇 |
2013年 | 90篇 |
2012年 | 57篇 |
2011年 | 69篇 |
2010年 | 52篇 |
2009年 | 81篇 |
2008年 | 80篇 |
2007年 | 92篇 |
2006年 | 73篇 |
2005年 | 67篇 |
2004年 | 70篇 |
2003年 | 63篇 |
2002年 | 55篇 |
2001年 | 37篇 |
2000年 | 42篇 |
1999年 | 41篇 |
1998年 | 39篇 |
1997年 | 41篇 |
1996年 | 37篇 |
1995年 | 26篇 |
1994年 | 29篇 |
1993年 | 11篇 |
1992年 | 16篇 |
1991年 | 16篇 |
1990年 | 16篇 |
1989年 | 14篇 |
1988年 | 11篇 |
1987年 | 10篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有1688条查询结果,搜索用时 15 毫秒
1.
2.
Sergei A. Klioner 《Celestial Mechanics and Dynamical Astronomy》1996,66(4):345-363
Intermediate orbit for general planetary theory is constructed in the form of multivariate Fourier series with numerical coefficients. The structure and efficiency of the derived series are illustrated by giving various statistical properties of the coefficients.The ability of the recently proposed elliptic function approach to compress the Fourier series representing the intermediate orbit is investigated. Our results confirm that when mutual perturbations of a pair of planets are considered the elliptic function approach is quite efficient and allows one to compress the series substantially. However, when perturbations of three or more planets are under study the elliptic function approach does not give any advantages. 相似文献
3.
We have derived the galaxy luminosity function in various regions of the cluster of galaxies Abell 496 from a wide field image
in the I band. A Schechter function fit in the 17≤ IAB ≤22(–19.5≤ MIAB ≤ –14.5) magnitude interval gives a steep power law index, which is somewhat steeper in the outer regions than in the inner
zones. This result agrees with previous findings obtained by several teams on the Coma cluster and can be interpreted as due
to the fact that faint galaxies are accreted by large ones in the central regions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
Lin Liu 《Chinese Astronomy and Astrophysics》1997,21(4):488-500
With the aim of analyzing the errors in the radial position of satellites, we give in this paper the expressions for the radial perturbation which include the complete zeroth- and first-order terms in the orbital eccentricity. A simpler and faster method of calculating the perturbation is given. 相似文献
5.
Sunetra Giridhar N. Kameswara Rao David L. Lambert 《Journal of Astrophysics and Astronomy》1996,17(1-2):23-40
Two high resolution spectra of the hot RCrB star DY Cen in the red region are compared. The photospheric absorption lines
show a radial velocity variation of 12 kms-1 between 1989 July and 1992 May. Emission components to some CII lines present
in 1989 are almost entirely absent in 1992. Nebular forbidden lines of [OI], [NII] and [SII] appear unchanged from 1989 to
1992 相似文献
6.
R. F. Griffin 《Journal of Astrophysics and Astronomy》1990,11(4):533-540
Photoelectric radial-velocity measurements show that HD 118670 is a double-lined spectroscopic binary in an orbit which is
not quite circular and whose period is about 48 days. Spectral types of K0 V and K7 V would satisfy the photometry and the
mass ratio; the mass function would then suggest the possibility of eclipses. However, actual spectral classification indicates
a luminosity somewhat above the main sequence 相似文献
7.
Thinly stratified sedimentary deposits in a heterogeneous field were investigated to obtain basic physical data for the simulation of water flow. A procedure is described which translates a thinly stratified soil profile into a number of functional layers using functional hydrological properties. A functional layer is defined as a combination of one or more soil horizons and should (i) be recognizable during a soil survey using an auger and (ii) show significantly different functional hydrological properties when compared with another functional layer. This procedure gave three easily recognizable functional layers. Sets of hydrological characteristics of these three functional layers were obtained by physical measurements of the soil and by estimation, using textural data for classification into a standard Dutch series. The performance of several combinations of these sets was tested by comparing simulated and measured soil matric potentials for seven plots during one year. The best simulation results were obtained if measured soil hydraulic characteristics were used for relatively homogeneous functional layers and if the soil hydraulic characteristics were estimated at each location for the most heterogeneous layer. 相似文献
8.
9.
西洋东大港水道流速垂线分布研究 总被引:2,自引:0,他引:2
对辐射沙洲海域东大港4#站位连续2个潮周期的流速测量资料进行了分析、研究,拟合给出了流速垂线分布关系,并根据实际测量资料确定了该站位6个水层的浑水水流尾流函数项表达式。这些表达式表明浑水水流尾流函数是相对深度和摩阻速度的函数。探讨分析了尾流函数的空间分布和潮周期过程。非恒定流的水流尾流函数项的准确表达,对于揭示含沙水流流速结构及水、沙相影响作用规律将起到启发和推动作用。 相似文献
10.