全文获取类型
收费全文 | 2448篇 |
免费 | 480篇 |
国内免费 | 831篇 |
专业分类
测绘学 | 19篇 |
大气科学 | 139篇 |
地球物理 | 593篇 |
地质学 | 2532篇 |
海洋学 | 49篇 |
天文学 | 8篇 |
综合类 | 74篇 |
自然地理 | 345篇 |
出版年
2024年 | 8篇 |
2023年 | 24篇 |
2022年 | 66篇 |
2021年 | 106篇 |
2020年 | 99篇 |
2019年 | 108篇 |
2018年 | 82篇 |
2017年 | 90篇 |
2016年 | 77篇 |
2015年 | 107篇 |
2014年 | 195篇 |
2013年 | 170篇 |
2012年 | 230篇 |
2011年 | 211篇 |
2010年 | 188篇 |
2009年 | 155篇 |
2008年 | 144篇 |
2007年 | 197篇 |
2006年 | 184篇 |
2005年 | 145篇 |
2004年 | 154篇 |
2003年 | 124篇 |
2002年 | 126篇 |
2001年 | 102篇 |
2000年 | 93篇 |
1999年 | 81篇 |
1998年 | 65篇 |
1997年 | 96篇 |
1996年 | 75篇 |
1995年 | 65篇 |
1994年 | 39篇 |
1993年 | 49篇 |
1992年 | 23篇 |
1991年 | 19篇 |
1990年 | 19篇 |
1989年 | 18篇 |
1988年 | 17篇 |
1987年 | 6篇 |
1985年 | 2篇 |
排序方式: 共有3759条查询结果,搜索用时 343 毫秒
11.
The purpose of this study is to validate and improve satellite-derived downward surface shortwave radiation (DSSR) over the northwestern Pacific Ocean using abundant in situ data. The DSSR derivation model used here assumes that the reduction of solar radiation by clouds is proportional to the product of satellite-measured albedo and a cloud attenuation coefficient. DSSR is calculated from Geostationary Meteorological Satellite-5/Visible Infrared Spin-Scan Radiometer data in 0.05° × 0.05° grids. The authors first compare the satellite DSSR derived with a cloud attenuation coefficient table determined in past research with in situ values. Although the hourly satellite DSSR agrees well with land in situ values in Japan, it has a bias of +13∼+34 W/m2 over the ocean and the bias is especially large in the low latitudes. The authors then improve the coefficient table using the ocean in situ data. Usage of the new table successfully reduces the bias of the satellite DSSR over the ocean. The cloud attenuation coefficient for low-albedo cases over the ocean needs to be larger in the low latitudes than past research has indicated. Daily and hourly DSSR can be evaluated from the satellite data with RMS errors of 11–14% and 30–33%, respectively, over a wide region of the ocean by this model. It is also shown that the cloud attenuation coefficient over land needs to be smaller than over the ocean because the effect of the radiation reflected by the land surface cannot be ignored. 相似文献
12.
本文根据滇西地区18个大地电磁测深点资料的数据处理和分析结果,对测区深部导电率在纵、横向上的变化特征进行了研究。结果表明:滇西地区深部电性为多层结构,大致可分四至五个电性结构层;深部电性结构横向变化大,明显受区域构造控制;该区上部地壳内普遍存在低阻层;上地幔高导层明显存在两个隆起区,一个以剑川—鹤庆为中心呈北北西向展布的隆起区,另一个以腾冲—潞西为轴呈南北向展布的隆起区。 本文还讨论了地壳上地幔电性结构与大地构造的关系,滇西北裂陷区盆地的形成,以及该区地震活动与深部构造的关系 相似文献
13.
14.
The Baimazhai nickel deposit, Yunnan Province, China, is located in the southern part of the Sanjiang (Tri-river) alkali-rich intrusive rock belt (Sanjiang ARIR). In this paper was conducted ^40Ar-^39Ar dating of two phlogopites in lamprophyres which are, as dikes, widely distributed in the orefield, and two plateau ages were acquired, i.e., 32.46±0.62 Ma and 32.01±0.60 Ma, respectively (averaging 32.23±0.60 Ma). The ages are obviously younger than those of the ore-hosted complex and mineralization of the Baimazhai nickel deposit. In combination with the characteristics, it is indicated that lamprophyres in the orefield and those in the Sanjiang ARIR are similar in tectonic setting, mineral assemblage and geochemistry. It is considered that lamprophyres in the orefield are the important component of the Sanjiang ARIR, and the lamprophyres and ore-hosted complex in the orefield represent the products of two times of different magmatic activity from different mantle sources. On the other hand, the age of lamprophyres in the orefield is older than that of the strike-slip shearing of the Ailaoshan-Honghe fault belt, suggesting that the strike-slip shearing of the Ailaoshan-Honghe fault belt is not the factor leading to magmatic activity of lamprophyres in the orefield, while it is more possible that magmatic activity of the Sanjiang ARIR promoted strike-slip shearing of the fault belt. 相似文献
15.
16.
17.
丽江市地质灾害易发性遥感影像判译 总被引:2,自引:0,他引:2
丽江市地质灾害多发,在滇西北旅游城市中较典型。应用遥感技术对丽江市地质灾害易发性的遥感研究,可突破传统方法,发挥宏观、综合、直观、快速特点,取得较好效果。 相似文献
18.
19.
20.