全文获取类型
收费全文 | 5148篇 |
免费 | 937篇 |
国内免费 | 1126篇 |
专业分类
测绘学 | 560篇 |
大气科学 | 892篇 |
地球物理 | 1198篇 |
地质学 | 2666篇 |
海洋学 | 593篇 |
天文学 | 130篇 |
综合类 | 474篇 |
自然地理 | 698篇 |
出版年
2024年 | 11篇 |
2023年 | 75篇 |
2022年 | 200篇 |
2021年 | 255篇 |
2020年 | 196篇 |
2019年 | 226篇 |
2018年 | 277篇 |
2017年 | 248篇 |
2016年 | 287篇 |
2015年 | 277篇 |
2014年 | 285篇 |
2013年 | 343篇 |
2012年 | 328篇 |
2011年 | 353篇 |
2010年 | 349篇 |
2009年 | 353篇 |
2008年 | 296篇 |
2007年 | 326篇 |
2006年 | 243篇 |
2005年 | 240篇 |
2004年 | 178篇 |
2003年 | 169篇 |
2002年 | 181篇 |
2001年 | 182篇 |
2000年 | 175篇 |
1999年 | 190篇 |
1998年 | 114篇 |
1997年 | 149篇 |
1996年 | 125篇 |
1995年 | 80篇 |
1994年 | 87篇 |
1993年 | 98篇 |
1992年 | 68篇 |
1991年 | 59篇 |
1990年 | 32篇 |
1989年 | 26篇 |
1988年 | 30篇 |
1987年 | 18篇 |
1986年 | 13篇 |
1985年 | 13篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1977年 | 2篇 |
1973年 | 2篇 |
1958年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有7211条查询结果,搜索用时 15 毫秒
111.
112.
利用欧洲资源卫星1号和2号获取的重轨干涉测量雷达数据,首先进行干涉测量数据相关性估测,并结合干涉测量数据的振幅信息,开展新疆喀什试验区地表土地类型的识别与分类,区分和识别出裸土、盐碱地、灌丛、裸岩/戈壁、沼泽和水体 6类土地类型。最后通过对不同土地类型的后向散射特性和相关性的分析,探讨了干涉测量数据相关性与干旱-半干旱地区地表特征的关系。 相似文献
113.
114.
ZHAO Zhi-zhong ZENG Qiao-song BI Hua 《大地构造与成矿学(英文版)》2002,(2):68-75
There are four types of metamorphic rocks in the Marinwobo fault, i. e, cataclasite, mylonite,mictosite and migmatitic granite, and the formation of these rocks is due to the progressive metamorphism of the pyroclastics. The fluids play a very important role in the metamorphic process of these rocks in the Marinwobo fault, the most important feature is that the fluids not only result in the migration of the major elements of the deformation rocks, but also result in the volume loss of the deformation rocks in the deformation process. Thus the migration laws of the major elements in different stages of the progressive metamorphic process are discussed according to mass balance equations. Finally, the quantitative analysis of the mass loss and volume loss of the different rocks the in Marinwobo fault is discussed in this paper. 相似文献
115.
Introduction The azimuth and slowness are two major features of seismic signals. The accurate estimation of them is quite important for both phase identification and event location. Generally, there are two types of seismic stations, i.e. 3-component stations (3C) and arrays. To estimate the two direc-tional parameters, the polarization analysis (Jurkevics, 1988) is commonly used for 3C stations and the frequency-wavenumber spectrum analysis ( f-k) (Capon, 1969; Kvaerna, Doornbos, 1986) is … 相似文献
116.
117.
Early Yanshanian post-orogenic granitoids in the Nanling region
Petrological constraints and geodynamic settings 总被引:1,自引:0,他引:1
Petrological constraints and geodynamic settings 总被引:1,自引:0,他引:1
Early Yanshanian magmatic suites predominate absolutely in the Nanling granite belt. They consist mainly of monzogranite and K-feldspar granite. There occur associations of early Yanshanian A-type granitoids (176 Ma-178 Ma) and bimodal volcanic rocks (158 Ma-179 Ma) in southern Jiangxi and southwestern Fujian in the eastern sector of the granite belt and early Yanshanian basalts (177 Ma-178 Ma) in southern Hunan in the central sector of the belt. Both the acid end-member rhyolite in the bimodal volcanic rock association and A-type granitoids in southern Jiangxi have the geochemical characteristics of intraplate granitic rocks and the basic end-member basalt of the association is intraplate tholeiite, while the basaltic rocks in southern Hunan include not only intraplate tholeiite but also intraplate alkali basalt. Therefore the early Yanshanian magmatic suites in the Nanling region are undoubtedly typical post-orogenic rock associations. Post-orogenic suites mark the end of a post-collision or late orogenic event and the initiation of Pangaea break-up, indicating that a new orogenic Wilson cycle is about to start. Therefore it may be considered that the early Yanshanian geodynamic settings in the Nanling region should be related to post-orogenic continental break-up after the Indosinian orogeny and the break-up did not begin in the Cretaceous. 相似文献
118.
119.
山岳型旅游区人文建筑环境后效与调控模型 总被引:4,自引:1,他引:4
许多山岳型旅游区内或其流域上游,都建有人文建筑,而且在急剧增多,导致自然环境日趋恶化,其中乱建疗养院和旅馆的影响最为严重。通过地监测并全面分析张家界环境演变趋势,发现住宿施对环境的影响,比其他游乐设施更为明显。张家界国家森林公园生态环境的脆弱因子是金鞭溪水质。金鞭溪水质恶化主要表现为蓝藻,绿藻迅速繁殖,感官质量下降。主要原因是磷污染较重,总磷年均值100%超标。本文提出了基于环境脆弱因子的动态阈值调控模型,通过计算得出:在不超出张家界景区最为脆弱的环境因子-金鞭溪水质标准:总磷≤0.02前提下,金鞭溪上游接待区住宿设施生态阈值的动态系列:春季临界床位数为1186,夏季为3057,冬季为545,秋季为333。目前的建筑规模已超过了金鞭溪上游接待区住宿设施生态阈值。 相似文献
120.
Evapotranspiration (ET) is an important parameter for water resource management. Compared to the traditional ET computation and measurement methods, the ET computation method based on remote sensing has the advantages of quickness, precision, raster mapping and regional scale. SEBAL, an ET computation model using remote sensing method is based on the surface energy balance equation which is a function of net radiance flux, soil heat flux, sensible heat flux and latent heat flux. The former three fluxes can be computed through the parameters retrieved from remote sensing image, then the latent heat flux can be obtained to provide energy for ET. Finally we can obtain the daily ET. In this study SEBAL was applied to compute ET in the Yellow River Delta of China where water resource faces a rigorous situation. Three Landsat TM images and meteorology data of 1999 were used for ET computation, and spatial and temporal change patterns of ET in the Yellow River Delta were analysed. 相似文献