全文获取类型
收费全文 | 8503篇 |
免费 | 1317篇 |
国内免费 | 2763篇 |
专业分类
测绘学 | 422篇 |
大气科学 | 1034篇 |
地球物理 | 1416篇 |
地质学 | 5989篇 |
海洋学 | 966篇 |
天文学 | 39篇 |
综合类 | 550篇 |
自然地理 | 2167篇 |
出版年
2024年 | 42篇 |
2023年 | 135篇 |
2022年 | 363篇 |
2021年 | 476篇 |
2020年 | 467篇 |
2019年 | 515篇 |
2018年 | 343篇 |
2017年 | 397篇 |
2016年 | 467篇 |
2015年 | 422篇 |
2014年 | 586篇 |
2013年 | 581篇 |
2012年 | 624篇 |
2011年 | 714篇 |
2010年 | 647篇 |
2009年 | 615篇 |
2008年 | 621篇 |
2007年 | 629篇 |
2006年 | 544篇 |
2005年 | 470篇 |
2004年 | 444篇 |
2003年 | 368篇 |
2002年 | 250篇 |
2001年 | 260篇 |
2000年 | 209篇 |
1999年 | 215篇 |
1998年 | 195篇 |
1997年 | 174篇 |
1996年 | 144篇 |
1995年 | 131篇 |
1994年 | 110篇 |
1993年 | 109篇 |
1992年 | 87篇 |
1991年 | 65篇 |
1990年 | 37篇 |
1989年 | 23篇 |
1988年 | 28篇 |
1987年 | 12篇 |
1986年 | 20篇 |
1985年 | 11篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1981年 | 3篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1976年 | 4篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
矿区地质、地球化学特征研究入手,总结了综合找矿标志,指出了进一步找矿方向。研究表明该矿床成矿组分单一,异常元素组合主要为Mo、Bi、Ag,次为W、Sn、Zn、Cu、Pb,仅有钼能形成较大规模的异常;矿床元素水平分带序列为(Mo-Bi-Ag)-(W-Sn)-(Pb-Zn-Cu),垂向分带序列为(Mo-Ag-Pb-Zn)-Cu-(Bi-W-Sn),并以w(Mo)/[w(Bi)×100]≥65,[w(Pb)×w(Zn)/w(W)×w(Sn)]≥25为判别标志,来预测深部盲矿体的存在。 相似文献
93.
94.
95.
YANG Keming 《《地质学报》英文版》2008,82(6)
The foreland basin in West Sichuan is a tectonic unit that has undergone multi-periods tectonic movements of Indosinian-Yanshanian-Himalayan. Since late Triassic, it has been in a passive subsidence environment controlled by basin margin mountain systems and by the compression with abundant sediment sources. With the complex geologic setting, the main geologic characteristics of natural gas reservoir are listed as following:(1)Source rocks are coal-bearing mud and shale series with high to over maturity, and long and progressive hydrocarbon generation-displacement period. The key accumulation period is middle-late Yanshanian epoch.(2)There are three gas-bearing systems vertically, each of which has different reservoir mechanism, main-controlled factors and distribution law, so the exploration thoughts and techniques are also different.(3)Undergoing multi-period generation-migration-accumulation, oil and gas have encountered multi-period modification or destruction, and gas accumulation overpass multiple tectonic periods. So the trap type is complicated and dominated by combination traps. Because the main accumulation period of natural gas is early and the reservoir encountered the modification of strong Himalayan movement, there is great difference in the fullness degree of gas reservoirs and complicated gas-water relation. (4) Reservoir is tight to very tight, but reservoirs of relatively high quality developed under the super tight setting. (5) The key techniques for oil and gas exploration in west Sichuan foreland basin are the prediction of relatively favorable reservoirs, fractures and gas bearing; and the key techniques for oil and gas development are how to improve the penetration rate, reservoir protection and modification. 相似文献
96.
The ionospheric eclipse factor method (IEFM) and its application to determining the ionospheric delay for GPS 总被引:4,自引:1,他引:3
A new method for modeling the ionospheric delay using global positioning system (GPS) data is proposed, called the ionospheric
eclipse factor method (IEFM). It is based on establishing a concept referred to as the ionospheric eclipse factor (IEF) λ
of the ionospheric pierce point (IPP) and the IEF’s influence factor (IFF) . The IEF can be used to make a relatively precise distinction between ionospheric daytime and nighttime, whereas the IFF
is advantageous for describing the IEF’s variations with day, month, season and year, associated with seasonal variations
of total electron content (TEC) of the ionosphere. By combining λ and with the local time t of IPP, the IEFM has the ability to precisely distinguish between ionospheric daytime and nighttime, as well as efficiently
combine them during different seasons or months over a year at the IPP. The IEFM-based ionospheric delay estimates are validated
by combining an absolute positioning mode with several ionospheric delay correction models or algorithms, using GPS data at
an international Global Navigation Satellite System (GNSS) service (IGS) station (WTZR). Our results indicate that the IEFM
may further improve ionospheric delay modeling using GPS data. 相似文献
98.
99.
松原市地下水防污性能评价 总被引:1,自引:0,他引:1
本文是依托于国土资源大调查项目"松花江重点地段地下水环境污染调查",在对松原市地下水污染现状调查的基础上,充分收集和整理了松原市的包气带和含水层资料,应用在DRASTIC模型基础上改进的DRTA模型进行了本区的地下水防污性能评价,评价结果采用MapGIS软件实现可视化显示。 相似文献
100.
宁德禅地铜矿床产于上侏罗统南园组第三段英安质晶屑凝灰熔岩夹层凝灰岩中。矿体呈脉状、缓倾角似层状,受断裂构造控制,成矿在时空上与中生代中酸性岩浆活动有密切相关,属于岩浆热液交代-充填型铜矿床。 相似文献