全文获取类型
收费全文 | 117762篇 |
免费 | 27042篇 |
国内免费 | 53940篇 |
专业分类
测绘学 | 12916篇 |
大气科学 | 27661篇 |
地球物理 | 27465篇 |
地质学 | 74789篇 |
海洋学 | 26575篇 |
天文学 | 9905篇 |
综合类 | 7651篇 |
自然地理 | 11782篇 |
出版年
2024年 | 844篇 |
2023年 | 2041篇 |
2022年 | 4159篇 |
2021年 | 5259篇 |
2020年 | 5348篇 |
2019年 | 8325篇 |
2018年 | 8405篇 |
2017年 | 8090篇 |
2016年 | 8285篇 |
2015年 | 8022篇 |
2014年 | 7775篇 |
2013年 | 9841篇 |
2012年 | 9530篇 |
2011年 | 9700篇 |
2010年 | 9624篇 |
2009年 | 9004篇 |
2008年 | 8349篇 |
2007年 | 8170篇 |
2006年 | 7460篇 |
2005年 | 6237篇 |
2004年 | 5792篇 |
2003年 | 4935篇 |
2002年 | 4648篇 |
2001年 | 4132篇 |
2000年 | 3523篇 |
1999年 | 2702篇 |
1998年 | 2478篇 |
1997年 | 2543篇 |
1996年 | 1993篇 |
1995年 | 1877篇 |
1994年 | 1700篇 |
1993年 | 1614篇 |
1992年 | 1401篇 |
1991年 | 1155篇 |
1990年 | 1144篇 |
1989年 | 970篇 |
1988年 | 878篇 |
1987年 | 820篇 |
1986年 | 760篇 |
1985年 | 768篇 |
1984年 | 831篇 |
1983年 | 718篇 |
1982年 | 715篇 |
1981年 | 615篇 |
1980年 | 539篇 |
1979年 | 538篇 |
1978年 | 422篇 |
1977年 | 428篇 |
1976年 | 377篇 |
1973年 | 387篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
本文通过对辽西及邻区中生代盆地火山岩稀土元素配分特征的研究及模拟运算,探讨了其岩浆成因及过程。结果显示南北岩区岩浆成因不同,南岩区岩源为MORB地幔和长期富集型幔熔融混合而成,北岩区为MORB和近期亏损型地幔熔融混合而成。 相似文献
73.
74.
75.
1 INTRODUCTION Sitting in the central part of the Pearl River Delta, Guangzhou is one of the cities in China that are most polluted by acid rain. Broad attention has been brought to the problem. Since the early 1980s, a series of observation and studies h… 相似文献
76.
The characteristics of atmospheric heat source associated with the summer monsoon onset in the South China Sea (SCS) are studied using ECMWF reanalysis data from 1979 to 1993. A criterion of the SCS summer monsoon onset is defined by the atmospheric hea… 相似文献
77.
78.
详细介绍了内江松柏寨的七山、七堰、八景等自然景观;对以般若寺为代表的寺庙、寨门以及历代名人所留下的行踪和墨迹作了生动描写;提出以生态旅游为理念进行统一规划,并采取保护性开发的若干建议。 相似文献
79.
The Sanchazi mafic-ultramafic complex in Mianlue tectonic zone, South Qinling can be subdivided into two blocks, i.e. Sanchazi paleo-magmatic arc and Zhuangkegou paleo-oceanic crust fragment (ophiolite). The Sanchazi paleo-magmatic arc is mainly composed of andesite, basaltic and basalt-andesitic gabbro (or diorite), andesitic dyke, plagiogranite and minor ultramafic rocks, which have typical geochemical features of island arc volcanic rocks, such as high field strength element (e.g. Nb, Ti) depletions and lower Cr, Ni contents. The Light rare earth element (LREE) and K enrichments of these rocks and zircon xenocrystals of 900 Ma from plagiogranite suggest that this magmatic arc was developed on the South active continental margin of the South Qinling micro-continent. The U-Pb age of (300 ± 61)Ma for zircons from plagiogranite indicates that the Mianlue paleo-oceanic crust was probably subducted underneath the South Qinling micro-continent in Carboniferous. This is consistent with the formation time (309Ma) of the Huwan eclogite originating from oceanic subduction in Dabie Mountains, suggesting that the Mianlue paleo-ocean probably extended eastward to the Dabie Mountains in Carboniferous. The high-Mg adakitic rocks in Sanchazi paleo-magmatic arc suggest that the subducted oceanic crust was relatively young (<25Ma) and hot. 相似文献
80.
Lakes in arid zone are sensitive to climatic changes. The lacustrine sediment sequence in Sogo Nur has well and truly recorded climatic events such as the Sui-Tang Dynasty Warm Period, the Song-Liao Dynasty Cold Period, the Medieval Warm Period, the Little Ice Age and the 20th Century Warm Period. Commonly, the climate in warm Periods was relatively humid,accordingly the lake area extended and water level rose, and vice versa. Apart from climatic change, human activity is also an important factor of influencing lake vicissitude, and they played the dominant role alternatively during different periods; the factor of climatic change predominated in historical period, while since the beginning of the 20th century the utilization of water resources by human has became decisive. 相似文献