全文获取类型
收费全文 | 7714篇 |
免费 | 1473篇 |
国内免费 | 1852篇 |
专业分类
测绘学 | 600篇 |
大气科学 | 810篇 |
地球物理 | 874篇 |
地质学 | 6572篇 |
海洋学 | 983篇 |
天文学 | 30篇 |
综合类 | 528篇 |
自然地理 | 642篇 |
出版年
2024年 | 134篇 |
2023年 | 348篇 |
2022年 | 410篇 |
2021年 | 406篇 |
2020年 | 363篇 |
2019年 | 377篇 |
2018年 | 288篇 |
2017年 | 273篇 |
2016年 | 279篇 |
2015年 | 298篇 |
2014年 | 404篇 |
2013年 | 320篇 |
2012年 | 355篇 |
2011年 | 416篇 |
2010年 | 396篇 |
2009年 | 386篇 |
2008年 | 405篇 |
2007年 | 345篇 |
2006年 | 322篇 |
2005年 | 322篇 |
2004年 | 292篇 |
2003年 | 299篇 |
2002年 | 272篇 |
2001年 | 311篇 |
2000年 | 319篇 |
1999年 | 250篇 |
1998年 | 225篇 |
1997年 | 276篇 |
1996年 | 271篇 |
1995年 | 276篇 |
1994年 | 256篇 |
1993年 | 181篇 |
1992年 | 204篇 |
1991年 | 192篇 |
1990年 | 199篇 |
1989年 | 141篇 |
1988年 | 56篇 |
1987年 | 37篇 |
1986年 | 25篇 |
1985年 | 24篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1974年 | 3篇 |
1957年 | 3篇 |
1946年 | 4篇 |
1941年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
Mercury (Hg) was investigated in bone tissues of skua ( Catharacta maccormick) and penguin (Pygoscelis adeliae) collected in the maritime Antarctic using atomic fluorescence spectrometry (AFS) and synchrotron radiation X-ray fluorescence (SR-XRF) method. The total levels of mercury in bone tissues of penguin and skua are much lower than those in other organs (e. g. , kidney, liver). The toxic effects of mercury in bone tissues of seabirds in polar region are not known. We have used SR- XRF method to map the distribution of trace levels of mercury in bones. The levels of mercury are found to be enriched somewhere near the periosteal surface and/or endosteal surface. The distribution of mercury shows strongly correlation with that of some essential elements and probably poses negative effect on the bone metabolism inferring from the relationship of mercury with the other elements. These studies represent a first step toward understanding the toxic effects of mercury on bone of polar animals by suggesting the possible microscopic investigation. 相似文献
4.
ENVIRONMENTAL SUSTAINABILITY AND SCENARIOS OF URBANIZATION IN ARID AREA——A Case Study in Wuwei City of Gansu Province 总被引:1,自引:0,他引:1
YOUFei LIYu DONGSuo-cheng 《中国地理科学(英文版)》2005,15(2):120-130
1IN T R O D U C T IO N The western China isfacinggrowing problems of eco- logicaland economic development. The disparitiebse- tween the socio-economy of the western and eastern China were enlarging, and the major ecologicalprob- lems stilelvolve as past(H… 相似文献
5.
JesusMartinez-Frias RosarioLunar RaulBenito 《《幕》》2004,27(1):33-38
This paper presents the first specific study of the Th-and U-bearing minerals, which were recently found in the SE Mediterranean margin of Spain (El Hoyazo area,Almeria province). These minerals are REE phosphates (mainly monazite) which occur as amoeboidal-to-elongate inclusions,from around 10 120μm to 120μm, hosted in single garnet crystals from dacite lavas and metamorphic rocks from the El Hoyazo Volcanic Complex. Th and U contents are higher than 1 wt%, with 3.04 to 5.62wt% for Th02, and 0.7 to 1.75 wt% for UO2. Both elements are also found in xenotime (ThO2:0.24,UO2:0.27wt%). Given that the erosion of the volcanic source rocks has generated a “placer-type” deposit of monazite sands and that garnets (main carriers of monazite) are being commercialised, an environmental monitoring and management plan should be urgently executed in the area. 相似文献
6.
7.
8.
9.
张启武 《国土资源导刊(湖南)》2006,(Z1)
湘中主要赋存有下石炭统测水组、上二叠统龙潭组、上三叠统安源组和下侏罗统造上组等煤系。湘中煤层气含量主要是受煤级、煤层埋深、构造运动、围岩、水文地质条件因素的影响。 相似文献
10.
Virtual Huanghe River System: Framework and Technology 总被引:2,自引:0,他引:2
LU Heli LIU Guifang SUN Jiulin 《中国地理科学(英文版)》2006,16(3):255-259
1 Introduction Huanghe (Yellow) River basin is located in 32°–42°N, 96°–119°E. The area of the catchment is more than 752,000km2. The river is 5464km long with a drop in elevation of 4830m. Among the whole area, the moun- tainous and stone area accounts for 29%, loess and hills area 46%, sandy area 11% and plain area 14%, respec- tively. Different natural landscapes exist in this area. The Huanghe River flows through the Loess Plateau, where the soil is eroded seriously (Wang, 2002;… 相似文献