全文获取类型
收费全文 | 9266篇 |
免费 | 1957篇 |
国内免费 | 2453篇 |
专业分类
测绘学 | 597篇 |
大气科学 | 1970篇 |
地球物理 | 2810篇 |
地质学 | 5479篇 |
海洋学 | 994篇 |
天文学 | 366篇 |
综合类 | 564篇 |
自然地理 | 896篇 |
出版年
2024年 | 62篇 |
2023年 | 139篇 |
2022年 | 351篇 |
2021年 | 355篇 |
2020年 | 366篇 |
2019年 | 475篇 |
2018年 | 360篇 |
2017年 | 365篇 |
2016年 | 377篇 |
2015年 | 434篇 |
2014年 | 562篇 |
2013年 | 566篇 |
2012年 | 598篇 |
2011年 | 599篇 |
2010年 | 510篇 |
2009年 | 632篇 |
2008年 | 652篇 |
2007年 | 715篇 |
2006年 | 638篇 |
2005年 | 550篇 |
2004年 | 504篇 |
2003年 | 439篇 |
2002年 | 410篇 |
2001年 | 325篇 |
2000年 | 351篇 |
1999年 | 302篇 |
1998年 | 330篇 |
1997年 | 322篇 |
1996年 | 266篇 |
1995年 | 190篇 |
1994年 | 196篇 |
1993年 | 140篇 |
1992年 | 145篇 |
1991年 | 118篇 |
1990年 | 88篇 |
1989年 | 71篇 |
1988年 | 72篇 |
1987年 | 29篇 |
1986年 | 28篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 9篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1971年 | 1篇 |
1954年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
中国古生教授学会微体古生物学分会举行代表大会和学术年会中国古竽物学会微体古物学分会第五次会员代表大分暨第六次不术年会于1996年1月24日到30日在福州市召开。来自全国地质、石油、煤炭的和产、科研和大学的100多位代表参加了这次大会和学术研讨。大会共... 相似文献
2.
3.
4.
Yoshio Kubo 《Celestial Mechanics and Dynamical Astronomy》1990,50(2):165-187
Hamiltonian mechanics is applied to the problem of the rotation of the elastic Earth. We first show the process for the formulation of the Hamiltonian for rotation of a deformable body and the derivation of the equations of motion from it. Then, based on a simple model of deformation, the solution is given for the period of Euler motion, UT1 and the nutation of the elastic Earth. In particular it is shown that the elasticity of the Earth acts on the nutation so as to decrease the Oppolzer terms of the nutation of the rigid Earth by about 30 per cent. The solution is in good agreement with results which have been obtained by other, different approaches. 相似文献
5.
利用 12年的Lageos 1卫星激光测距资料 (1990 - 2 0 0 1)解算得到了地球定向参数 (EOP) ,将该序列的结果与同期的EOP(IERS)C0 4进行比较 ,其外符精度为 :极移XP— 0 .4 0mas,YP— 0 .4 2mas ,日长变化Dr— 0 .0 35ms。 相似文献
6.
Pittichovâ J. Sekenina Z. Birkle K. Boehnhardt J. Engels D. Keller P. 《Earth, Moon, and Planets》1997,78(1-3):329-338
The Sekanina-Farrell particle fragmentation model for the striated tails of dust comets is successfully applied to two images
of comet Hale-Bopp to study the motions of 12 striae in a time span of March 12–15, 1997. There is evidence for recurring
outbursts with a periodicity of 11h21m, consistent with results based on analysis of dust jets. The ejecta in all the striae appear to have been released from one
source on the nucleus between the end of January and the second half of February 1997, some 60 to 40 days before perihelion.
The parent particles were subjected to a radiation pressure acceleration of βp ≃ 0.55 and their fragmentation lifetimes in 11 of the 12 striae were practically constant and equal to 13–15 days, when normalized
to 1 AU from the Sun. Brief analysis of Watanabe et al.'s measurements of striae on their images from March 5–9, 1997 shows
even shorter fragmentation lifetimes for the parent particles, mostly about 7–11 days at1 AU.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
Based on the Intensive Field Campaign(IFC-1)data of Boreal Ecosystem-Atmosphere Study(BOREAS).a three-dimensional meso-β scale model is used to simulate the effect of boreal forests onthe lower atmosphere.A fine horizontal resolution of 2 km×2 km is used in order to distinguish thevegetative heterogeneity in the boreal region.A total of 20×25 grid points cover the entire sub-modeling area in BOREAS' South Study Area(SSA).The ecosystem types and their coverage ineach grid square are extracted from the North American Land Cover Characteristics Data Base(NALCCD)generated by the U.S.Geographical Survey(USGS)and the University of Nebraska-Lincoln(UNL).The topography of the study area is taken from the Digital Elevation Map(DEM)of USGS.The model outputs include the components of the energy balance budget within the canopyand at the ground.the turbulence parameters in the atmospheric boundary layer and the wind.temperature and humidity profiles extending up to a height of 1500 m.In addition to the fine timeand spatial step,the unique feature of the present model is the incorporation of both dynamic andbiological effects of the Boreal forest into the model parameterization scheme.The model resultscompare favorably with BOREAS' IFC-1 data in 1994 when the forest was in the luxuriant growingperiod. 相似文献
8.
9.
Yehuda Ben-Zion 《Geophysical Journal International》1990,101(3):507-528
10.
秦岭凤太矿田层控铅锌(铜)矿床的金属物质、硫和成矿溶液主要来自深部基底的岩石,属海底喷流—沉积成因矿床。从这一理论认识出发可进一步分析控矿地质条件及今后在该区有效地寻找同类矿床。 相似文献