全文获取类型
收费全文 | 2067篇 |
免费 | 106篇 |
国内免费 | 504篇 |
专业分类
测绘学 | 103篇 |
大气科学 | 244篇 |
地球物理 | 808篇 |
地质学 | 764篇 |
海洋学 | 205篇 |
天文学 | 92篇 |
综合类 | 303篇 |
自然地理 | 158篇 |
出版年
2023年 | 15篇 |
2022年 | 7篇 |
2021年 | 18篇 |
2020年 | 9篇 |
2019年 | 21篇 |
2018年 | 22篇 |
2016年 | 19篇 |
2015年 | 17篇 |
2014年 | 32篇 |
2013年 | 28篇 |
2012年 | 79篇 |
2011年 | 94篇 |
2010年 | 29篇 |
2009年 | 60篇 |
2008年 | 102篇 |
2007年 | 119篇 |
2006年 | 119篇 |
2005年 | 129篇 |
2004年 | 124篇 |
2003年 | 111篇 |
2002年 | 106篇 |
2001年 | 105篇 |
2000年 | 118篇 |
1999年 | 52篇 |
1998年 | 55篇 |
1997年 | 39篇 |
1996年 | 55篇 |
1995年 | 64篇 |
1994年 | 65篇 |
1993年 | 77篇 |
1992年 | 71篇 |
1991年 | 92篇 |
1990年 | 74篇 |
1989年 | 82篇 |
1988年 | 75篇 |
1987年 | 63篇 |
1986年 | 47篇 |
1985年 | 65篇 |
1984年 | 52篇 |
1983年 | 29篇 |
1982年 | 25篇 |
1981年 | 19篇 |
1980年 | 44篇 |
1979年 | 5篇 |
1978年 | 10篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1974年 | 8篇 |
1963年 | 3篇 |
1957年 | 2篇 |
排序方式: 共有2677条查询结果,搜索用时 46 毫秒
951.
本文叙述两种用于绘制建造三维地貌立体模型所需模片的制图算法。从美国国防制图局的1:250000比例尺数字地形磁带中提取高程数据,用来组装等高线立体模型和剖面立体模型。 相似文献
952.
DRY-WET EVOLUTION IN GUANGDONG PROVINCE DURING LAST 500 YEARS 总被引:1,自引:0,他引:1
1 INTRODUCTIONThe global warming change has already become one ofthe focuses that many scientists pay attention to, and theprecipitation change of China is also one part of thequestionsunder the whole world changes today. Accord-ing to the actual material analysis, the climate in Chinahad a warm-dry tendency in a wide spread range duringthe past one hundred years (ZHAO, 1993), and it couldnot draw a verdict as for future tendency at present. Fol-lowing the thought of Prof. HUANG Bing… 相似文献
953.
1 MathematicModelofTidalVibrationSupposethat 3semi -axesofaellipsoidarea ,bandc (a >b >c) ,latitudeisθ ,longitudeisψ(changingfrom 0°to 90°) , 相似文献
954.
Qijia-Gulong Depression Northern Songliao Basin YAN Jianping LIU Li ZHANG Xinrong MA Yanping 《东北亚地学研究》2002,(2)
IntroductionTheorderingofdiageneticeventsisoneofthemostimportantkeystotheultimateinterpretationofthewaysinwhichthegeologicalandgeochemicalhistoryofasandstoneaffecteditscompositionandtexture .Thisarti clegiveadetaildescriptionandoriginexplanationtothea… 相似文献
955.
Cold water in the deep Pacific can be drawn up to the surface (or west warm water drifts eastwards) because strong tide increases the mixing of seawater both in vertical and horizontal. In this way greenhouse effect is decreased or in-creased by means of absorbing (or releasing) CO2. Therefore, La Nina cold event (or El Nino warm event) may occur, which is caused by wanning - up or cooling - down air above the ocean. Volcanic action at sea bottom is also controlled by strong tide. 相似文献
956.
Based on investigations of the Zhongwei Nanshan aeolian section situated in the southeastern margin of Tengger Desert, carbon-14 and TL (thermoluminescence) dating results and paleoclimatie proxies such as magnetic susceptibility and grain size, we inferred that the northwestern margin of East Asian monsoon region experienced abrupt climatic changes during the last deglaciation. Six oscillation events were identified: Oldest Dryas, Bφlling, Older Dryas, Allerφd, Intra-Allerφd Cold Period (IACP) and Younger Dryas (YD). The summer monsoon was weaker during Oldest Dryas and Younger Dryas when the winter monsoon was stronger. However, during the B/A (Bφlling/Allerφd) period, the summer monsoon strengthened, reflected by magnetic susceptibility, when the winter monsoon also became strong, which is different from the paleoclimatic pattern established in the East Asian monsoon region. Furthermore, the summer monsoon was nearly in phase with the climate changes inferred from the oxygen isotopic records of 相似文献
957.
958.
LU La-chang 《中国地理科学(英文版)》2001,(2)
1 INTRODUCTION China is a country with many nationalities. The western China includes Zhuang Autonomous Region of Guangxi, Guizhou Province, Yunnan Province, Chongqing City, Sichuan Province, Xizang(Tibet) Autonomous Region, Uygur Autonomous Region of Xijiang, Qinghai Province, Hui Autonomous Region of Ningxia, Gansu Province, Shaanxi Province and the Inner Mongolia Autonomous Region, these places are densely populated with 46 minorities out of a total of 55 minorities of C… 相似文献
959.
1 INTRODUCTIONAccording to historical records, there has existed the large-area desert in the northwest of China for a long time, which formed in the geologic age and historical periods, and continuously evolved because of climate changes and human activities. Although a certain amount of achievement has been obtained since the 1950s, land desertification went on expanding quickly. For desertification by wind erosion, the average expansion speed was 1560km2 per year from the late 1950s … 相似文献
960.
人类和每一种生物的生理生存都依赖于水,而许多人类食品的生产却又破坏了水质(如灌溉、鱼类产卵场的维护等)。要想评价地表水水质是比较困难的。与海水相比,它的离子含量变化非常大,海水是很均一的。 相似文献