全文获取类型
收费全文 | 1313篇 |
免费 | 32篇 |
国内免费 | 14篇 |
专业分类
测绘学 | 100篇 |
大气科学 | 65篇 |
地球物理 | 312篇 |
地质学 | 444篇 |
海洋学 | 58篇 |
天文学 | 310篇 |
综合类 | 16篇 |
自然地理 | 54篇 |
出版年
2022年 | 11篇 |
2021年 | 17篇 |
2020年 | 19篇 |
2019年 | 27篇 |
2018年 | 64篇 |
2017年 | 49篇 |
2016年 | 67篇 |
2015年 | 42篇 |
2014年 | 51篇 |
2013年 | 82篇 |
2012年 | 44篇 |
2011年 | 43篇 |
2010年 | 44篇 |
2009年 | 56篇 |
2008年 | 57篇 |
2007年 | 46篇 |
2006年 | 36篇 |
2005年 | 34篇 |
2004年 | 19篇 |
2003年 | 25篇 |
2002年 | 21篇 |
2001年 | 22篇 |
2000年 | 23篇 |
1999年 | 25篇 |
1998年 | 27篇 |
1997年 | 15篇 |
1996年 | 16篇 |
1995年 | 22篇 |
1994年 | 17篇 |
1993年 | 19篇 |
1992年 | 12篇 |
1991年 | 25篇 |
1990年 | 12篇 |
1989年 | 20篇 |
1988年 | 14篇 |
1987年 | 15篇 |
1986年 | 10篇 |
1985年 | 15篇 |
1984年 | 14篇 |
1983年 | 13篇 |
1982年 | 26篇 |
1981年 | 13篇 |
1980年 | 15篇 |
1979年 | 16篇 |
1978年 | 15篇 |
1975年 | 8篇 |
1974年 | 11篇 |
1973年 | 12篇 |
1972年 | 12篇 |
1971年 | 13篇 |
排序方式: 共有1359条查询结果,搜索用时 31 毫秒
1.
Studying relativistic compact objects is important in modern astrophysics to understand several astrophysical issues. It is therefore natural to ask for an internal structure and physical properties of specific classes of compact stars from astrophysical observations. We obtain a class of new relativistic solutions with anisotropic distribution of matter for compact stars. More specifically, stellar models, described by an anisotropic fluid, establishing a relation between metric potentials and generating a specific form of mass function, are explicitly constructed within the framework of General Relativity. New solutions can be used to model compact objects, which adequately describe compact strange star candidates like SMC X-1, Her X-1 and 4U 1538-52, with observational data taken from Gangopadhyay et al. (Mon. Not. R. Astron. Soc. 431:3216, 2013). As a possible astrophysical application the obtained solutions could explain the physics of selfgravitating objects, and might be useful for strong-field regimes where data are currently inadequate. 相似文献
2.
It is shown that the kinematical parameters associated with the congruence formed by tachyonic motion can be defined in the manner of Greenberg, but not that of Ehlers. The space-like counterpart of Raychaudhuri's equation has also been obtained. 相似文献
3.
4.
The most general accurate solutions for the Buchdhal fluid sphere were obtained and matched with the Schwarzchild's exterior
solution at the pressure free interface. Various parameters of the solutions were so adjusted that the energy density, pressure
and temperature were positive and decreasing away from the centre, and the velocity of sound was less than unity throughout
the spheroid model. Using this procedure, the maximum mass of the fluid sphere with a surface density of2 × 1014gm cm-3 was determined to be 3.82MΘ and 4.57 MΘ for strong and weak energy conditions respectively. PACS number: 0402, 0402J, 0440D,
95301
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
C. Debi Prasad Ashok Ambastha Nandita Srivastava Sushanta C. Tripathy Mona J. Hagyard 《Journal of Astrophysics and Astronomy》1997,18(1):39-55
Super-active region NOAA 6555 was highly flare productive during the period March 21st–27th, 1991 of its disk passage. We
have st udied its chromospheric activity using high spatial resolution Hα filtergrams taken at Udaipur along with MSFC vector
magnetograms. A possible relationship of flare productivity and the variation in shear has been explored. Flares were generally
seen in those subareas of the active region which possessed closed magnetic field configuration, whereas only minor flares
and/or surges occurred in subareas showing open magnetic field configuration. Physical mechanisms responsible for the observed
surges are also discussed. 相似文献
6.
The new calculations of the Oiv temperature-sensitive EUV line ratios are presented and compared with previous results. 相似文献
7.
Subramanian Prasad Ananthakrishnan S. Janardhan P. Kundu M.R. White S.M. Garaimov V.I. 《Solar physics》2003,218(1-2):247-259
We present the first observations of a solar flare with the GMRT. An M2.8 flare observed at 1060 MHz with the GMRT on 17 November 2001 was associated with a prominence eruption observed at 17 GHz by the Nobeyama radioheliograph and the initiation of a fast partial halo CME observed with the LASCO C2 coronagraph. Towards the start of the eruption, we find evidence for reconnection above the prominence. Subsequently, we find evidence for rapid growth of a vertical current sheet below the erupting arcade, which is accompanied by the flare and prominence eruption. 相似文献
8.
9.
The flow of laser radiation in a plane-parallel cylindrical slab of active amplifying medium with axial symmetry is treated as a problem in radiative transfer. The appropriate one-dimensional transfer equation describing the transfer of laser radiation has been derived by an appeal to Einstein'sA, B coefficients (describing the processes of stimulated line absorption, spontaneous line emission, and stimulated line emission sustained by population inversion in the medium) and considering the rate equations to completely establish the rational of the transfer equation obtained. The equation is then exactly solved and the angular distribution of the emergent laser beam intensity is obtained; its numerically computed values are given in tables and plotted in graphs showing the nature of peaks of the emerging laser beam intensity about the axis of the laser cylinder. 相似文献
10.
Age estimates of coastal terraces in the Andaman and Nicobar Islands and their tectonic implications
Kusala Rajendran C.P. Rajendran Anil Earnest G.V. Ravi Prasad K. Dutta D.K. Ray R. Anu 《Tectonophysics》2008,455(1-4):53-60
The great Indian Ocean earthquake of December 26, 2004 caused significant vertical changes in its rupture zone. About 800 km of the rupture is along the Andaman and Nicobar Islands, which forms the outer arc ridge of the subduction zone. Coseismic deformation along the exposed land could be observed as uplift/subsidence. Here we analyze the morphological features along the coast of the Andaman and Nicobar Islands, in an effort to reconstruct the past tectonics, taking cues from the coseismic effects. We obtained radiocarbon dates from coastal terraces of the island belt and used them to compute uplift rates, which vary from 1.33 mm yr− 1 in the Little Andaman to 2.80 mm yr− 1 in South Andaman and 2.45 mm yr− 1 in the North Andaman. Our radiocarbon dates converge on 600 yr and 1000 yr old coastal uplifts, which we attribute to the level changes due to two major previous subduction earthquakes in the region. 相似文献