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161.
Variations of seismic mode in the region of the Avachinsky Gulf (Kamchatka, Russia) are considered. Observed anomalies (seismic quiescence, the ring seismicity, reduction of the slope of the earthquake recurrence diagram) provide a basis to consider this region as a place of strong earthquake preparation. The Kamchatka regional catalogues of earthquakes between 1962–1995 were used in the analysis. A reduced seismicity rate is observed during 10 years in an area of 150 km × 60 km in size. During the last five years, in the vicinity of the area considered, earthquakes with M > 5 occurred three times more often than the average over thirty years. It is interpreted as ring seismicity. The block of 220 km × 220~km in size, including the quiescence zone, is characterized by a continuous decrease of the recurrence diagram slope, which has reached a minimum value for the last 33 years in this region. 相似文献
162.
1998年第四季度,全球共发生6级以上地震11次,其中11月29日塞兰海地震为7.7级,地震频度低而强度高。1996 ̄1998年,全球地震活动呈逐年下降趋势。1998年全年共发生6级以上地震(包括深震)78次,其中有2次7.7级以上大地震。本年度6级以上浅源地震频数继续减少,全年只有64次。1996 ̄、998年,Ⅰ带和Ⅱ带地震活动逐年减弱;亚欧带有起伏,1997年最高,1998年回落。中国大陆地震 相似文献
163.
We analyzed more than 1700 earthquakes related to the 1982 eruption of El Chichon volcano in southern Mexico. The data were
recorded at specific periods throughout the whole eruptive interval of March to April 1982, by three different networks. The
seismic activity began several months before the first eruption on 28 March. During this period the seismicity consisted of
hybrid and long-period shallow earthquakes most likely related to processes of faulting, fracturing, and fluid movement underneath
the volcano. The foci of events occurring before the eruption circumscribe an aseismic zone from approximately 7 to 13 km
below the volcano. After the eruption, the seismic activity consisted of tectonic-type earthquakes that peaked at 1200 events/h.
This later activity occurred over a wide range of depths, mostly between 5 and 20 km, that includes the former aseismic zone
and is roughly limited by the major tectonic faults in the area.
Received: 19 May 1998 / Accepted: 13 June 1999 相似文献
164.
研究了川滇22 次 M≥6 34 级地震前区域性中强震活动变化情况。验证了某些震兆特征的客观性和普遍性。本文研究结果给出, (1) 强震前区域性中强震活动相对活跃; (2) 震源附近可能发生多次5 ~6级地震; (3) 震中周围出现5 级以上地震组成的相对活动区或活动带; (4) 震源区周围相当范围内显示平静特征。追踪区域性中强震活动变化对于预测未来较大强震的危险性有实际意义。 相似文献
165.
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168.
WEN-ZHENG YANG 《地震学报(英文版)》1999,12(1):35-45
With the theory of subcritical crack growth, we can deduce the fundamental equation of regional seismicity acceleration model. Applying this model to intraplate earthquake regions, we select three earthquake subplates: North China Subplate, Chuan-Dian Block and Xinjiang Subplate, and divide the three subplates into seven researched regions by the difference of seismicity and tectonic conditions. With the modified equation given by Sornette and Sammis (1995), we analysis the seismicity of each region. To those strong earthquakes already occurred in these region, the model can give close fitting of magnitude and occurrence time, and the result in this article indicates that the seismicity acceleration model can also be used for describing the seismicity of intraplate. In the article, we give the magnitude and occurrence time of possible strong earthquakes in Shanxi, Ordos, Bole-Tuokexun, Ayinke-Wuqia earthquake regions. In the same subplate or block, the earthquake periods for each earthquake region are similar in time interval. The constant αin model can be used to describe the intensity of regional seismicity, and for the Chinese Mainland, α is 0.4 generally. To the seismicity in Taiwan and other regions with complex tectonic conditions, the model does not fit well at present. 相似文献
169.
GUI-PING LIU 《地震学报(英文版)》1999,12(3):277-284
The time and spatial feature of the regional seismicity triggered by the Hyogo-Ken Nanbu, Japan, M=7.2 earthquake on January 17,1995, was studied. The concerned region is about several hundred kilometers in length and breadth surrounding the epicenter (33°~37°N, 133°~138°E). It is divided into 16 subregions. The seismicity of these subregions from January of 1976 to June of 1996 has been analyzed. It is showed that,① there were significant seismicity changes in 10 subregions triggered by the Hyogo-Ken Nanbu, Japan, M=7.2 earthquake on January 17, 1995. These changes passed a Z statistic test exceeding 0.95 confidence level and the greatest epicenter distance of these subregions was 280 km;②seismicity changes were triggered within 1~5 days in three subregions near the main shock while in other subregions the seismicity changes were triggered within several ten days after the main shock;③ the greatest triggered event is 5.4, which is about the same size as the greatest aftershock;④the regional stress change resulted from the main shock may be the triggered mechanism of the regional seismicity. 相似文献
170.