全文获取类型
收费全文 | 140554篇 |
免费 | 19261篇 |
国内免费 | 42770篇 |
专业分类
测绘学 | 5218篇 |
大气科学 | 27958篇 |
地球物理 | 34195篇 |
地质学 | 70542篇 |
海洋学 | 25420篇 |
天文学 | 27784篇 |
综合类 | 4218篇 |
自然地理 | 7250篇 |
出版年
2022年 | 1031篇 |
2021年 | 1732篇 |
2020年 | 3160篇 |
2019年 | 6666篇 |
2018年 | 8570篇 |
2017年 | 8064篇 |
2016年 | 8666篇 |
2015年 | 6360篇 |
2014年 | 7286篇 |
2013年 | 10368篇 |
2012年 | 7857篇 |
2011年 | 8427篇 |
2010年 | 8209篇 |
2009年 | 8774篇 |
2008年 | 7426篇 |
2007年 | 7281篇 |
2006年 | 6563篇 |
2005年 | 5411篇 |
2004年 | 5758篇 |
2003年 | 5281篇 |
2002年 | 4953篇 |
2001年 | 4455篇 |
2000年 | 3900篇 |
1999年 | 3496篇 |
1998年 | 3696篇 |
1997年 | 3694篇 |
1996年 | 3020篇 |
1995年 | 2884篇 |
1994年 | 2682篇 |
1993年 | 2428篇 |
1992年 | 2167篇 |
1991年 | 1956篇 |
1990年 | 2013篇 |
1989年 | 1755篇 |
1988年 | 1586篇 |
1987年 | 1700篇 |
1986年 | 1418篇 |
1985年 | 1693篇 |
1984年 | 1872篇 |
1983年 | 1615篇 |
1982年 | 1595篇 |
1981年 | 1443篇 |
1980年 | 1290篇 |
1979年 | 1220篇 |
1978年 | 1197篇 |
1977年 | 1051篇 |
1976年 | 990篇 |
1975年 | 968篇 |
1974年 | 913篇 |
1973年 | 999篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
D. Montes M. C. Gálvez M. J. Fernández-Figueroa I. Crespo-Chacón 《Astrophysics and Space Science》2006,304(1-4):367-369
High resolution echelle spectroscopic observations taken with the FEROS spectrograph at the 2.2 m telescope ESO confirm the binary nature of the flare M3.5V star LU Vel (GJ 375, RE J0958-462) previously reported by Christian and Mathioudakis (2002). Emission of similar intensity from both components is detected in the Balmer, Na i D1&D2, He i D3, Ca ii H&K, and Ca ii IRT lines. We have determined precise radial velocities by cross correlation with radial velocity standard stars, which have allowed us to obtain for the first time the orbital solution of the system. The binary consists of two near-equal M3.5V components with an orbital period shorter than 2 days. We have analyzed the behaviour of the chromospheric activity indicators (variability and possible flares). In addition, we have determined its rotational velocity and kinematics. 相似文献
102.
J. M. Diego J. Mohr J. Silk G. Bryan 《Monthly notices of the Royal Astronomical Society》2003,341(2):599-608
We develop a new method to estimate the redshift of galaxy clusters through resolved images of the Sunyaev–Zel'dovich effect (SZE). Our method is based on morphological observables which can be measured by actual and future SZE experiments. We test the method with a set of high-resolution hydrodynamical simulations of galaxy clusters at different redshifts. Our method combines the observables in a principal component analysis. After calibrating the method with an independent redshift estimation for some of the clusters, we show – using a Bayesian approach – how the method can give an estimate of the redshift of the galaxy clusters. Although the error bars given by the morphological redshift estimation are large, it should be useful for future SZE surveys where thousands of clusters are expected to be detected; a first preselection of the high-redshift candidates could be done using our proposed morphological redshift estimator. Although not considered in this work, our method should also be useful to give an estimate of the redshift of clusters in X-ray and optical surveys. 相似文献
103.
104.
O.V.Chumak 《中国天文和天体物理学报》2003,3(2):175-182
We present a study of the relationship between integral area and corresponding total magnetic flux for solar active regions. It is shown that some of these relationships are satisfied to simple power laws. Fractal examination showed that some of these power laws can not be justified inside the simple models of stationary magnetic flux tube aggregation. All magnetic fluxes and corresponding areas were calculated using the data measured with the Solar Magnetic Field Telescope of the Huairou Solar Observing Station in Beijing. 相似文献
105.
昆仑山8.1级地震前中国大陆的构造应变背景 总被引:10,自引:4,他引:6
利用“网络工程”1998~2001年累积的1181个测站的GPS重复观测资料,采用双三次样条函数模型建立中国大陆水平运动模型速度场,用大地坐标在椭球面上计算各类应变场,详细分析了2001年昆仑山8.1级地震前中国大陆水平构造应变场空间分布特征。各类构造应变场的最高值都出现在喜马拉雅构造带与昆仑山地块内(地震断裂带南侧),鲜水河—安宁河断裂带次之。分析表明,昆仑山8.1级地震正好发生在张性面膨胀应变率的高值区,第一、第二和最大剪应变率高值区边缘的突变区和最大、最小主应变率的高值区。 相似文献
106.
E.A. Evstigneeva R.R. de Carvalho A.L. Ribeiro H.V. Capelato 《Astrophysics and Space Science》2003,284(2):487-490
We present the preliminary results of a study of how small stellar systems merge to form larger ones. As we display the families
of galaxies in the μe - Re plane (effective surface brightness versus effective radius) we realize that different morphological types occupy different
loci, evidencing the different physical mechanisms operating in each family. As proposed by Capaccioli et al. (1992) this
diagram is the logical equivalent of the HR diagram for stars. Here we take some initial steps in understanding of how we
can establish the evolutionary tracks, solely due to dynamical processes, in the μe - Re plane, ultimately making a dwarf elliptical to turn into a normal elliptical galaxy.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
107.
108.
A synthesis of Holocene pollen records from the Tibetan Plateau shows the history of vegetation and climatic changes during the Holocene. Palynological evidences from 24 cores/sections have been compiled and show that the vegetation shifted from subalpine/alpine conifer forest to subalpine/alpine evergreen sclerophyllous forest in the southeastern part of the plateau; from alpine steppe to alpine desert in the central, western and northern part; and from alpine meadow to alpine steppe in the eastern and southern plateau regions during the Holocene. These records show that increases in precipitation began about 9 ka from the southeast, and a wide ranging level of increased humidity developed over the entire of the plateau around 8-7 ka, followed by aridity from 6 ka and a continuous drying over the plateau after 4-3 ka. The changes in Holocene climates of the plateau can be interpreted qualitatively as a response to orbital forcing and its secondary effects on the Indian Monsoon which expanded northwards 相似文献
109.
110.
V. G. Gorbatskii 《Astrophysics》1990,32(2):149-154
Leningrad State University. Translated from Astrofizika, Vol. 32, No. 2, pp. 267–275, March–April, 1990. 相似文献