全文获取类型
收费全文 | 53941篇 |
免费 | 9503篇 |
国内免费 | 12799篇 |
学科分类
地球科学 | 76243篇 |
出版年
2024年 | 259篇 |
2023年 | 924篇 |
2022年 | 2215篇 |
2021年 | 2647篇 |
2020年 | 2204篇 |
2019年 | 2465篇 |
2018年 | 2885篇 |
2017年 | 2599篇 |
2016年 | 3057篇 |
2015年 | 2558篇 |
2014年 | 3220篇 |
2013年 | 3049篇 |
2012年 | 2903篇 |
2011年 | 2998篇 |
2010年 | 3162篇 |
2009年 | 3065篇 |
2008年 | 2791篇 |
2007年 | 2697篇 |
2006年 | 2153篇 |
2005年 | 1948篇 |
2004年 | 1584篇 |
2003年 | 1596篇 |
2002年 | 1523篇 |
2001年 | 1516篇 |
2000年 | 1828篇 |
1999年 | 2637篇 |
1998年 | 2158篇 |
1997年 | 2066篇 |
1996年 | 1894篇 |
1995年 | 1670篇 |
1994年 | 1508篇 |
1993年 | 1332篇 |
1992年 | 1060篇 |
1991年 | 840篇 |
1990年 | 614篇 |
1989年 | 581篇 |
1988年 | 509篇 |
1987年 | 306篇 |
1986年 | 271篇 |
1985年 | 201篇 |
1984年 | 159篇 |
1983年 | 125篇 |
1982年 | 124篇 |
1981年 | 103篇 |
1980年 | 67篇 |
1979年 | 59篇 |
1978年 | 20篇 |
1977年 | 14篇 |
1976年 | 12篇 |
1958年 | 43篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
By use of the H observations of the Astrophysical Observatory in Catania, Italy and the Purple Mountain Observatory in Nanking, China as well as hard X-ray and gamma-ray burst data from the Solar Maximum Mission (SMM) Gamma-Ray Spectrometer (GRS), a major eruptive loop prominence was studied during the limb solar flare event of 1981 April 27.Our preliminary analysis shows that there seems to exist a second abrupt energy release for this event, almost 20 min after the end of the impulsive phase of the flare. This energy release is probably associated with the rapidity in upward motion or activation of the loop prominence.A possible candidate for such a process could be the reconnection of the old magnetic field with a newly emerging magnetic field.A theoretical gross estimate for the energy release and particle acceleration has also been made in this work. It appears that the proposed model for charged particle acceleration is very efficient. 相似文献
63.
山西能源重化工基地建设关系到全国四个现代化的实现,被列为国家重点建设工程,制定了《山西能源重化工基地综合规划》。本文分析了80年代山西省经济建设的成就与问题。提出了“整体创新,综合开发”,把山西能源重化工基地建设成内陆经济开放区的战略大思路,为此,90年代应完成11项大型经济战略工程,同时展望了经济发展改革前景。 相似文献
64.
视电阻率定义在电法勘探中得到广泛的应用。目前在频率域电磁法中常常采用远区视电阻率定义。由于在频率域中收发距并非足够大,以致在低频段远区定义视电阻率往往不能反映地下电阻率值。我们定义全区电阻率及引入校正系数K,经二层三层模型及野外实测资料的计算,证明了方法的有效性。 相似文献
65.
66.
67.
The Anzishan ophiolite, a typical ophiolitic block of early Carboniferous age in the Mian-Lue suture zone of the Qinling Mountains, central China, consists of amphibolites/metabasalts, gabbros and gabbroic cumulates. All of these rocks, as well as those in the Hunshuiguan-Zhuangke (HZ) block, have compositions similar to normal MORB and back-arc basin basalts (BABB) with high εNd(t) values, indicating that they were derived from a depleted mantle source. The Mian-Lue suture zone also contains blocks of other lithologies, e.g., rift volcanic rocks in the Heigouxia block and arc volcanic rocks in the Sanchazi block. Although they are in fault contact with each other, the presence of these different blocks in the Mian-Lue suture zone may represent a complete Wilson cycle, from initial rifting to open ocean basin to final subduction and continent-continent collision, during the late Paleozoic-early Triassic. In this region, the North and South China Cratons were separated by Paleo-Tethys at least until the early Carboniferous, and final amalgamation of both cratons along the Qinling orogenic belt took place in the Triassic. 相似文献
68.
Mechanism for the rapid motion of the Qianjiangping landslide during reactivation by the first impoundment of the Three Gorges Dam reservoir, China 总被引:10,自引:6,他引:4
Fawu Wang Yeming Zhang Zhitao Huo Xuanming Peng Shimei Wang Shintaro Yamasaki 《Landslides》2008,5(4):379-386
The first impoundment of the Three Gorges Dam reservoir in China started from a water surface elevation of 95 m on June 1,
2003 and reached 135 m on June 15, 2003. Shortly after the water level reached 135 m, many slopes began to deform and some
landslides occurred. The Qianjiangping landslide is the largest one; it occurred on the early morning of July 14, 2003 and
caused great loss of lives and property. Field investigation revealed that, although failure occurred after the reservoir
reached 135 m, the stability of the slope was already reduced by preexisting sheared bedding planes. To study the mechanism
of the rapid motion of this reactivated landslide, two soil samples were taken from a yellow clay layer and a black silt layer
in the sliding zone, respectively, and a series of ring shear tests were conducted on the samples. One series of ring shear
tests simulates the creep deformation behavior, while the other series simulates different shear rates. Conclusions drawn
from analysis of the ring shear tests indicate that the mechanism of the rapid motion of the reactivated landslide was caused
by the rate effect of the black silt layer during the motion phase after the creep failure. The yellow clay layer did not
play any important role in the rapid motion in the 2003 event. 相似文献
69.
70.
At present, researches on climate change of the Heihe River basin mainly focus on the relationship between basin climate change
and regional water resources, regional desertification and dynamic climatic seasons of sandstorm, but less on climate change
of oasis region, where there are more intense and frequent human activities. Based on data of precipitation, temperature,
strong wind and dust events frequencies obtained from the six meteorological stations of Zhangye region in Heihe River basin,
the features of climate change during 1968–2005 were carefully studied. Results show that the regional temperature rise rate
exceeded the average level of China. The annual precipitation changed a little, but the precipitation had a slowly increasing
trend in spring and winter. Frequencies of strong wind and sandstorm days show obviously descending trends, which had a close
correlation with the regional temperature rise and the precipitation increase in spring and winter. Meanwhile, further human
economic activities and exploitations to the oasis in the inland valley of arid regions also affected the climate change of
this region, which has a sensitive and fragile eco-environment.
__________
Translated from Journal of Desert Research, 2007, 27(6): 1048–1054 [译自: 中国沙漠] 相似文献