全文获取类型
收费全文 | 2378篇 |
免费 | 566篇 |
国内免费 | 842篇 |
专业分类
测绘学 | 442篇 |
大气科学 | 342篇 |
地球物理 | 552篇 |
地质学 | 1496篇 |
海洋学 | 439篇 |
天文学 | 18篇 |
综合类 | 188篇 |
自然地理 | 309篇 |
出版年
2024年 | 25篇 |
2023年 | 84篇 |
2022年 | 160篇 |
2021年 | 203篇 |
2020年 | 138篇 |
2019年 | 200篇 |
2018年 | 147篇 |
2017年 | 130篇 |
2016年 | 159篇 |
2015年 | 186篇 |
2014年 | 152篇 |
2013年 | 192篇 |
2012年 | 202篇 |
2011年 | 236篇 |
2010年 | 220篇 |
2009年 | 190篇 |
2008年 | 211篇 |
2007年 | 178篇 |
2006年 | 182篇 |
2005年 | 134篇 |
2004年 | 90篇 |
2003年 | 68篇 |
2002年 | 74篇 |
2001年 | 75篇 |
2000年 | 48篇 |
1999年 | 25篇 |
1998年 | 11篇 |
1997年 | 12篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
1954年 | 2篇 |
排序方式: 共有3786条查询结果,搜索用时 24 毫秒
851.
RUILIN WEN JULE XIAO ZHIGANG CHANG DAYOU ZHAI QINGHAI XU YUECONG LI SHIGERU ITOH 《Boreas: An International Journal of Quaternary Research》2010,39(2):262-272
Wen, R. L., Xiao, J. L., Chang, Z. G., Zhai, D. Y., Xu, Q. H., Li, Y. C. & Itoh, S. 2009: Holocene precipitation and temperature variations in the East Asian monsoonal margin from pollen data from Hulun Lake in northeastern Inner Mongolia, China. Boreas, 10.1111/j.1502‐3885.2009.00125.x. ISSN 0300‐9483. Quantitative palaeoclimatic reconstruction with the weighted averaging partial least squares method was applied to the pollen profile from Hulun Lake in northeastern Inner Mongolia. The data provide a detailed history of variations in precipitation and temperature over the northeastern margin of the East Asian summer monsoon during the Holocene. A warm and dry climate prevailed over the lake region until c. 8000 cal. BP. During the period c. 8000–4400 cal. BP, precipitation increased markedly and temperature gradually declined. The interval between c. 4400 and 3350 cal. BP was marked by extremely dry and relatively cold conditions. Precipitation recovered from c. 3350 to 1000 cal. BP, with temperatures rising c. 3350–2050 cal. BP and dropping c. 2050–1000 cal. BP. During the last 500 years, the climate of the lake region displayed a general trend of warming and wetting. While Holocene temperature variations in the mid‐high latitude monsoonal margin were controlled by changes in summer solar radiation in the Northern Hemisphere, they could also be related to the strength of the East Asian summer monsoon. The lack of precipitation during the early Holocene could be attributed to the weakened summer monsoon resulting from the existence of remnant ice sheets in the Northern Hemisphere. Changes in the monsoonal precipitation during the middle to late Holocene would have been associated with the ocean–atmosphere interacting processes occurring in the western tropical Pacific. 相似文献
852.
853.
854.
855.
856.
857.
为实现对全国天气雷达不同波段、不同型号、不同区域的回波差异进行检测和评估,确保雷达组网数据的均一性,利用经过严格数据质量控制后的单站雷达CAPPI格点数据,建立了可靠的相邻雷达回波强度均一性检测算法,并根据我国天气雷达回波差异实际状况制定了均一性评估标准,实现均一性算法的业务运行,使雷达观测同一区域回波反射率的实时均一性评估成为可能。从评估结果来看:①S波段雷达整体均一性强于C波段雷达,SA雷达均一性状况最好,CC、CD雷达均一性状况较差;②以SA型号雷达为主的华东、华南地区均一性较好;③雷达波段不一,型号繁多的偏远区域均一性较差。均一性评估系统对有回波但回波强度、回波位置不正确以及雷达数据时间错位的情况,能有效弥补其他质控算法的短板,及时发现雷达回波异常,缩短故障修复时间,提高雷达数据准确性。 相似文献
858.
本文根据区域台网的观测资料,研究了云南省龙陵地区1971年至1980年的小震平均节面解的变化特点。结果表明:1.1971年2月至1975年11月,平均节面解的P轴方位同北东-南西向的区域应力场一致;2.大震前半年和大震后两天的P轴方位变为340°和176°,同主震的P轴相一致;3.强余震前的小震平均节面解同强余震的节面解相似;4.1977年至1980年3月,P波初动符号的矛盾比上升到30%以上,在此期间本区未发生5级以上的地震。最后讨论了本文所得的结果及其前兆意义。 相似文献
859.
安徽铜陵凤凰山岩体若干特征及成矿关系 总被引:1,自引:0,他引:1
<正> 安徽铜陵凤凰山岩体,出露面积约9km2,呈似岩株状,总体成分属正常的钙碱系列的花岗闪长岩,副矿物为磁铁矿、榍石、磷灰石型,主要侵入于中三叠纪扁担山组灰岩中。岩体接触带北部向北陡倾,东部向东中等倾斜,南部向南倾较缓,西部超覆于围岩之上而产状较复杂。 相似文献
860.
ZHANG Ming-li WEN Zhi DONG Jian-hua WANG De-kai YUE Guo-dong WANG Bin GAO Qiang 《岩土力学》2020,41(5):1549-1559
In order to understand the hydrothermal activity mechanism of active layers to rainfall in permafrost regions caused by humidification of climate, the differences of ground surface energy balance and hydrothermal activity in different types of shallow soil with the consideration of rainfall were discussed. Based on the meteorological data in 2013 observed at Beiluhe observation station of Tibet Plateau, three types of shallow ground soil (i.e., sandy soil, sandy loam and silty clay) were selected to compare the differences in the water content and energy balance at the ground surface, dynamic processes of water and energy transport in active layers and coupling mechanism under rainfall condition in the plateau using a coupled water-vapor-heat transport model. The results show that the increase of soil particle size leads to the increase of surface net radiation and latent heat of evaporation, but the decrease of soil heat flux. The difference of surface energy balance, especially the sensible heat flux and latent heat of evaporation, are larger in the warm season but smaller in the cold season. The liquid water transport under hydraulic gradient and the water-vapor transport under thermal gradient are obvious as the particle size in soil increases. However, the water-vapor flux under thermal gradient increases but the liquid water flux under hydraulic potential gradient decreases. As a result, the water content in shallow soil decreases accordingly but it increases slightly at the depth of 25 ~75 cm. Moreover, with the increase of soil particle size, the thermal conductivity of soil, convective heat transfer under rainfall and surface evaporation increase, but the soil heat conduction flux and soil temperature gradient decrease. Thus, soil temperature in sandy soil is much higher than that of sandy loam and silty clay at the same depth. The permafrost table declines with the increase of the thickness of active layer, which is unfavourable to permafrost stability. The results can provide theoretical reference for stability prediction and protection of permafrost caused by humidification of climate. 相似文献