全文获取类型
收费全文 | 1428篇 |
免费 | 261篇 |
国内免费 | 367篇 |
专业分类
测绘学 | 52篇 |
大气科学 | 216篇 |
地球物理 | 339篇 |
地质学 | 900篇 |
海洋学 | 171篇 |
天文学 | 67篇 |
综合类 | 172篇 |
自然地理 | 139篇 |
出版年
2024年 | 7篇 |
2023年 | 31篇 |
2022年 | 62篇 |
2021年 | 67篇 |
2020年 | 50篇 |
2019年 | 87篇 |
2018年 | 81篇 |
2017年 | 67篇 |
2016年 | 78篇 |
2015年 | 63篇 |
2014年 | 73篇 |
2013年 | 69篇 |
2012年 | 70篇 |
2011年 | 97篇 |
2010年 | 80篇 |
2009年 | 86篇 |
2008年 | 70篇 |
2007年 | 69篇 |
2006年 | 61篇 |
2005年 | 50篇 |
2004年 | 43篇 |
2003年 | 32篇 |
2002年 | 41篇 |
2001年 | 40篇 |
2000年 | 57篇 |
1999年 | 88篇 |
1998年 | 60篇 |
1997年 | 61篇 |
1996年 | 49篇 |
1995年 | 56篇 |
1994年 | 45篇 |
1993年 | 47篇 |
1992年 | 17篇 |
1991年 | 21篇 |
1990年 | 22篇 |
1989年 | 10篇 |
1988年 | 16篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1965年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有2056条查询结果,搜索用时 15 毫秒
991.
992.
Based on observational data of thunderstorm and lightening of 76 stations in Shaanxi, the National Centers for Environmental Prediction / National Centers for Atmospheric Research (NCEP/NCAR) reanalysis dataset from 1960 to 2010, the major modes of thunderstorm in warm seasons (May to September) of Shaanxi province and mechanism of its possible influence are studied .The results show that:①the thunderstorms show an obvious decreasing trend in the past 51 years, the average thunderstorm days reaching the peak in July, of which 70% occurred in warm season.②There are two dominant modes: EOF1 mode depicting a thunderstorm phase oscillation between the East and the West of Shaanxi province and EOF2 mode describing negative anomaly oscillation between the North and the middle of Shaanxi province and positive anomaly oscillation between Yan’an area and some areas of Southern Shaanxi province. These two modes account for 53.1% and 13.6% of total variance respectively. ③Analysis with Morlet wavelet method indicates that EOF1 mode has an inter annual changing cycle of 3 to 6 years and EOF2 has an interdecadal change cycle of about 15 years.④The meteorological field regression of EOF1 time coefficient shows the West Pacific subtropical high 584 line is located near 30°N ,the flowing of the southwest warm wet airflow to the north increases and the thunderstorms increase in the west of Shaanxi province; the time coefficient regression of EOF2 shows that the Northern Hemisphere polar vortex is weaker and the pressure over Mongolia area is stronger than usual result in the north wind component’s increasing ,which contributes to the formation EOF2. ⑤The important factors influencing Shaanxi thunderstorm spatial mode EOF1 include the location and the strength of Northwest Pacific subtropical high. In the same way, the Northern Hemisphere polar vortex possibly has a close connection with Shaanxi thunderstorm. 相似文献
993.
通过对21181综放工作面的突水特征与突水水质检测资料的分析,以及开采导水裂隙带高度的计算,得出了工作面突水原因——采煤后形成的导水裂隙带已波及到了上覆侏罗系上统巨厚砾岩含水层,通过运用合理的防治方案.为今后综放工作面预防水害打下了基础。 相似文献
994.
995.
The anti-slide support structure is widely used in the anti-seismic reinforcement of bridge foundations, but related experimental research was processing slowly. Based on the prototype of the Jiuzhaigou bridge at the Chengdu-Lanzhou Railway, a 3-D simulation model was established on the basis of the shaking table model test, and the rationality of the dynamic analysis model was verified by indicators such as the bending moment of the bridge piles, peak soil pressure, and PGA amplification factors. The results show that the inertia force of the bridge pier has an important influence on the deformation of the pile foundation. The bending moment and shearing force are larger in lateral bridge piles, and the maximum value is near the pile top. The PGA amplification factor is stronger in the back of the rear anti-slide piles and so is it in front of the bridge pier, and the soil is prone to slip and damage. The bedrock is rigid and the dynamic response is maintained at a low level. The anti-slide piles in the rear row play a major role in the anti-seismic reinforcement design, and the anti-slide piles in the front row can be used as an auxiliary support structure. 相似文献
996.
997.
I.DynamicStI.uctureofRegioIlalUl.baIlizati0llRegionalurbanizationa11dregionaleconol11icdevelopl1lel1tarecloselyrelated.Tl1eprocessofregionaleconol11icdevelopmentisactuallytheprocessofurbangroWthandurbansystel11developn1ent.Regiol1alurbal1izatiol1isl1otonlythespatiall11anifestati0nofregionaleconolllicdeveloplllent,butalsothespatialmeanstofosterregiol1aleconon1icdevelopment.Tl1el11ajortheoriesofdeveloplnentec0nomicsanddeveloplllel1ttheoriesofregiollaleconon1icsaftertl1eSec0l1dWorldWarareall… 相似文献
998.
Geotechnical and Geological Engineering - In order to reveal the deformation and failure mechanism of surrounding rock of deep layered roadway, the deformation field of physical model experiment of... 相似文献
1000.