全文获取类型
收费全文 | 3462篇 |
免费 | 86篇 |
国内免费 | 58篇 |
专业分类
测绘学 | 326篇 |
大气科学 | 299篇 |
地球物理 | 628篇 |
地质学 | 1518篇 |
海洋学 | 154篇 |
天文学 | 544篇 |
综合类 | 55篇 |
自然地理 | 82篇 |
出版年
2023年 | 18篇 |
2022年 | 58篇 |
2021年 | 79篇 |
2020年 | 73篇 |
2019年 | 71篇 |
2018年 | 287篇 |
2017年 | 256篇 |
2016年 | 249篇 |
2015年 | 146篇 |
2014年 | 212篇 |
2013年 | 290篇 |
2012年 | 180篇 |
2011年 | 179篇 |
2010年 | 155篇 |
2009年 | 168篇 |
2008年 | 138篇 |
2007年 | 98篇 |
2006年 | 89篇 |
2005年 | 60篇 |
2004年 | 55篇 |
2003年 | 50篇 |
2002年 | 41篇 |
2001年 | 30篇 |
2000年 | 39篇 |
1999年 | 34篇 |
1998年 | 27篇 |
1997年 | 25篇 |
1996年 | 25篇 |
1995年 | 15篇 |
1994年 | 32篇 |
1993年 | 34篇 |
1992年 | 14篇 |
1991年 | 36篇 |
1990年 | 21篇 |
1989年 | 20篇 |
1988年 | 14篇 |
1987年 | 27篇 |
1986年 | 23篇 |
1985年 | 26篇 |
1984年 | 22篇 |
1983年 | 11篇 |
1982年 | 13篇 |
1981年 | 12篇 |
1980年 | 25篇 |
1979年 | 21篇 |
1978年 | 14篇 |
1975年 | 10篇 |
1974年 | 12篇 |
1972年 | 11篇 |
1971年 | 15篇 |
排序方式: 共有3606条查询结果,搜索用时 78 毫秒
1.
Ashok Kumar Dubey 《地学学报》2004,16(3):91-94
Geometric and kinematic models reveal that rotation of layers during thrusting or development of drag folds produced by movement along listric thrust faults results in the formation of dilation space at the junction of the thrust ramp with the basal decollement. This is accompanied by upwarping of the basement to occupy the available space thereby producing an antiformal structure, which restricts the thrust displacement. The structure is termed a decollement upwarp and examples are cited from the foothill belt of the Himalaya. 相似文献
2.
3.
4.
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
5.
A recently developed near infrared high speed photometer intended for lunar oc-cultation studies is described. The primary scientific objective is to reach milli arc second levels of angular resolution so that circumstellar structure of the occulted sources can be resolved. Near infrared sky brightness close to the lunar limb is also studied. Angular diameter derived from the observed occultation of IRC +20169 is presented and system performance discussed. 相似文献
6.
The present work applies the method of characteristics to study the behaviour of planar and cylindrical wave-heads propagating through a perfectly electrically conducting and thermally radiating inviscid gas under the optically thin limit in the presence of a transverse magnetic field. The true nonlinear progress of the flow variable gradients at the wavefront is predicted and the critical distance at which the characteristics pile up at the wavefront to form a shock wave is obtained. It is investigated as to how the effects of radiative flux, the magnetic field strength and the specific heat ratio influence the process of steepening or flattening of the characteristic wavefront. 相似文献
7.
The oscillatory, conjugate and asymptotic behaviours of the principal and non-principal solutions of the Blasius and corresponding heat transfer equations governing the compressible laminar boundary-layer flow over a semi-infinite flat plate with heat flux have been studied; the results of the discussion being based on the asymptotic integrations of second-order linear differential equations. 相似文献
8.
9.
10.
1IntroductionThe Late Mesozoic sequences of Afghanistan are important in understanding the geodynamic evolu-tion of the northwestern part of South Asia, in par-ticular the transgressive and regressive history of the northwestern part of the Tethys connecting Iran to the west and the northern Indian Subcontinent to the east. Jurassic to Upper Cretaceous sedimentary seque-nces were initially studied by Griesbach (1885 ~1887) and Hayden (1880~1901) through several traverses in northern an… 相似文献