全文获取类型
收费全文 | 5158篇 |
免费 | 901篇 |
国内免费 | 1224篇 |
专业分类
测绘学 | 349篇 |
大气科学 | 937篇 |
地球物理 | 1207篇 |
地质学 | 2672篇 |
海洋学 | 621篇 |
天文学 | 249篇 |
综合类 | 501篇 |
自然地理 | 747篇 |
出版年
2024年 | 27篇 |
2023年 | 85篇 |
2022年 | 268篇 |
2021年 | 271篇 |
2020年 | 264篇 |
2019年 | 298篇 |
2018年 | 287篇 |
2017年 | 268篇 |
2016年 | 295篇 |
2015年 | 273篇 |
2014年 | 294篇 |
2013年 | 371篇 |
2012年 | 314篇 |
2011年 | 291篇 |
2010年 | 292篇 |
2009年 | 289篇 |
2008年 | 245篇 |
2007年 | 250篇 |
2006年 | 209篇 |
2005年 | 163篇 |
2004年 | 118篇 |
2003年 | 137篇 |
2002年 | 146篇 |
2001年 | 147篇 |
2000年 | 148篇 |
1999年 | 210篇 |
1998年 | 184篇 |
1997年 | 160篇 |
1996年 | 162篇 |
1995年 | 129篇 |
1994年 | 132篇 |
1993年 | 106篇 |
1992年 | 93篇 |
1991年 | 66篇 |
1990年 | 71篇 |
1989年 | 43篇 |
1988年 | 34篇 |
1987年 | 23篇 |
1986年 | 20篇 |
1985年 | 15篇 |
1984年 | 14篇 |
1983年 | 15篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 10篇 |
1975年 | 2篇 |
1969年 | 3篇 |
1968年 | 2篇 |
排序方式: 共有7283条查询结果,搜索用时 15 毫秒
101.
WUXiaofang CAIZhongliang WUGuofeng DUQingyun 《地球空间信息科学学报》2003,6(4):27-31
Through analyzing the principle of data sharing in the database system, this paper discusses the principle and method for integrating and sharing GIS data by data engine, introduces a way to achieve the high integration and sharing of GIS data on the basis of VCT in VC , and provides the method for uniting VCT into RDBMS in order to implement a spatial database with object-oriented data model. 相似文献
102.
高原交通干线对土地利用和景观格局的影响——以兰州至格尔木段为例 总被引:12,自引:1,他引:12
运用景观生态学方法和Arc/Info软件,研究1995年至2000年兰州至格尔木铁路沿线的区域土地利用和景观格局变化,分析交通干线(公路和铁路)的影响程度与范围。主要结果如下:(1)东线土地利用和景观格局没有发生显著变化,西线土地利用和景观格局变化较大;(2)东线缓冲带土地利用程度综合指数没有显著变化,西线缓冲带土地利用程度综合指数明显升高。缓冲带综合土地利用动态度的变化反映了交通干线的轴向影响规律;兰州至西宁铁路对土地利用变化的显著影响范围是5km,青藏铁路对土地利用变化的显著影响范围是7km;(3)9个城市缓冲带的土地利用变化分析表明:城市扩展主要发生在1km缓冲带内。 相似文献
103.
Ultrahigh-pressure metamorphism in the forbidden zone: the Xugou garnet peridotite, Sulu terrane, eastern China 总被引:21,自引:3,他引:21
The Xugou garnet peridotite body of the southern Sulu ultrahigh‐pressure (UHP) terrane is enclosed in felsic gneiss, bounded by faults, and consists of harzburgite and lenses of garnet clinopyroxenite and eclogite. The peridotite is composed of variable amounts of olivine (Fo91), enstatite (En92?93), garnet (Alm20?23Prp53?58Knr6?9Grs12?18), diopside and rare chromite. The ultramafic protolith has a depleted residual mantle composition, indicated by a high‐Mg number, very low CaO, Al2O3 and total REE contents compared to primary mantle and other Sulu peridotites. Most garnet (Prp44?58) clinopyroxenites are foliated. Except for rare kyanite‐bearing eclogitic bands, most eclogites contain a simple assemblage of garnet (Alm29?34Prp32?50Grs15?39) + omphacite (Jd24?36) + minor rutile. Clinopyroxenite and eclogite exhibit LREE‐depleted and LREE‐enriched patterns, respectively, but both have flat HREE patterns. Normalized La, Sm and Yb contents indicate that both eclogite and garnet clinopyroxenite formed by high‐pressure crystal accumulation (+ variable trapped melt) from melts resulting from two‐stage partial melting of a mantle source. Recrystallized textures and P–T estimates of 780–870 °C, 5–7 GPa and a metamorphic age of 231 ± 11 Ma indicate that both mafic and ultramafic protoliths experienced Triassic UHP metamorphism in the P–T forbidden zone with an extremely low thermal gradient (< 5 °C km?1), and multistage retrograde recrystallization during exhumation. Develop of prehnite veins in clinopyroxenite, eclogite, felsic blocks and country rock gneiss, and replacements of eclogitic minerals by prehnite, albite, white mica, and K‐feldspar indicate low‐temperature metasomatism. 相似文献
104.
105.
WangShicheng YeShuisheng ZhouDongdai 《中国地质大学学报(英文版)》2003,14(3):207-214
Metallogenic prognosis of synthetic information uses the geological body and the miaeral resource body as a statistical unit to interpret synthetically the information of geology, geophysics, geo-chemistry and remote sensing from the evolution of geology and puts all the information into one entire system by drawing up digitalized interpretation maps of the synthetic information. On such basis, differ-ent grades and types of mineral resource prospecting models and predictive models of synthetic informa-tion can be established. Hence, a new integrated prediction system will be formed of metallogenic prog-nosis (qualitative prediction), mineral resources statistic prediction (determining targets) and mlaeral resources prediction (determining resources amount). 相似文献
106.
During the whole 20th century in China, especially the latest 50 years, we have gotten much geological information about geological mapping, geophysics, geochemistry, mineral exploration,remote sensing, environmental geology, hydrogeology, engineering geology and oceanic geology etc. by our geologists and explorers. All the information has been accmnulated and can be used as a dcision-making foundation for the future plan of geological survey. The spatial database of geological survey ex-tents has been established by using computer technology. The database contained all kinds of exploration sections and collected about 160 000 records in this database. This paper introduces the data construc-tion ,contents and applying systemof this database, and trys to let people know what kinds of geological survey were finished, when the exploration were carried out, and how and where you can get this infor-mation. 相似文献
107.
统计1965年以来影响韶关的热带气旋发现,韶关出现暴雨不仅与热带气旋的路径、强度有关,而且与大气层结稳定度或冷空气的相互作用密切相关。由此结合实况、应用数值预报产品来制作热带气旋暴雨24小时预报。 相似文献
108.
109.
通过对1975~1998年北京动物园动物发病率的统计分析,揭示了不同动物发病率的年变化特征和长期变化趋势,并分季节进行了发病率与气象因子的相关分析,发现冬季兽类发病率、秋季禽类发病率与同期气象因子相关较好,总体看春、夏季动物发病率与气象因子的关系不明显。 相似文献
110.
The Northward Shift of Climatic Belts in China During the Last 50 Years and the Corresponding Seasonal Responses 总被引:29,自引:0,他引:29
Along the meridian of 105°E, the Chinese region are divided into two parts, east and west. The results show that in the east part of China the temperate extratropical belt, the warm extratropical belt,and the northern subtropical belt shift northward significantly, whereas the middle subtropical belt and the southern subtropical belt have less or no change. As for the northern subtropical belt, the maximal northward shift can reach 3.7 degrees of latitude. As for the warm extratropical belt, along the meridian of 120°-125°E, the maximal northward shift can reach 3-4 degrees. In the west part of China, each climatic belt changes little. Only in the Xinjiang area are the significant northward shifts. Correspondingly, it is found that in the last 50 years the traditional seasons have changed. For Beijing, Hailar, and Lanzhou, in general, summer becomes longer and winter shorter over the last 50 years. Summer begins early and ends late with respect to early 1950s. Contrary to the summer, winter begins la 相似文献