首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   275篇
  免费   63篇
  国内免费   9篇
测绘学   5篇
大气科学   3篇
地球物理   209篇
地质学   112篇
海洋学   10篇
天文学   3篇
综合类   3篇
自然地理   2篇
  2024年   1篇
  2023年   1篇
  2022年   3篇
  2021年   4篇
  2020年   2篇
  2019年   9篇
  2018年   6篇
  2017年   6篇
  2016年   7篇
  2015年   6篇
  2014年   10篇
  2013年   9篇
  2012年   12篇
  2011年   17篇
  2010年   4篇
  2009年   18篇
  2008年   12篇
  2007年   14篇
  2006年   15篇
  2005年   13篇
  2004年   17篇
  2003年   4篇
  2002年   8篇
  2001年   7篇
  2000年   13篇
  1999年   11篇
  1998年   13篇
  1997年   17篇
  1996年   18篇
  1995年   13篇
  1994年   8篇
  1993年   9篇
  1992年   7篇
  1991年   4篇
  1990年   4篇
  1989年   1篇
  1988年   6篇
  1987年   2篇
  1986年   1篇
  1985年   3篇
  1984年   9篇
  1978年   1篇
  1977年   1篇
  1954年   1篇
排序方式: 共有347条查询结果,搜索用时 15 毫秒
81.
利用1992年10月22日-2001年7月17日扣除年循环的T/P和ERS-1/-2的卫星融合高度计资料,应用二维Radon变换方法,对太平洋和大西洋的洋盆东部、西部的大洋Rossby波的纬向传播速度进行了分析与对比,并将二者分别与经典线性理论值比较,得出洋盆西部的Rossby波普遍比洋盆东部传播要快;中纬度海域大洋Rossby波的传播速度观测值与理论值的比率小于前人结果;并且在热带及副热带海域,大洋Rossby波的传播速度的观测值要低于理论值的结论。  相似文献   
82.
222Rn was measured in the near-bottom waters of the continental slope of the Mid-Atlantic Bight. Separate measurements of the 222Rn supported by dissolved 226Ra allowed the excess 222Rn that is derived from the underlying sediments to be distinguished. Measurements of production of 222Rn by the sediments were used to calculate fluxes of 222Rn from sediments that would be expected as a result of molecular diffusion. On the upper slope and on the lower slope excess 222Rn standing crops were, respectively, greater than and consistent with fluxes of radon from sediments by molecular diffusion as are typical of most ocean environments. On the middle slope, however, observed excess 222Rn concentrations and standing crops were significantly lower than what would be expected from the calculated fluxes from the underlying sediments. This unusual feature of low radon concentrations on the middle slope is referred to as the low-radon zone (LRZ). This LRZ was always present over several years and seasons, but was variable in intensity (excess-radon concentration and standing crop) and in location on the slope. Low concentrations of suspended particulate matter and low current velocities observed by others in the same region are consistent with low mixing as a possible cause of the LRZ. Radon profile shapes and recent work by others on near bottom mixing due to interactions between topography and internal waves, however, suggest that high mixing due to internal waves is a more likely cause of the LRZ.  相似文献   
83.
李忠华  周尽 《地震研究》1992,15(3):234-239
本文采用“根据时间序列数据重建复杂系统动力学特征”的方法,对澜沧—耿马地震前后澜沧、普洱、思茅和芒市台的水氡旬均值进行了处理,得到震前澜沧.普洱和芒市台水氡状态吸引子维数d在1.0—3.0之间,这从理论上说明了澜沧—耿马地震孕育过程中此三台站水氡变化遵从某些确定性规律,并指出了这些确定性规律所依赖的基本变量数目范围,这对认识大震孕育过程中水氡变化的动力学行为具有一定意义。  相似文献   
84.
刘伟 《地质与勘探》2023,59(1):113-121
岩溶区页岩气钻井在近地表常揭露溶洞、地下河、强裂隙带等不良地质体,严重制约了页岩气资源勘探开发的进程。在岩溶页岩气靶区利用地球物理技术探测对钻探不利的近地表地质结构构造,可有效规避钻井钻遇近地表强岩溶发育带、断层破碎带的风险。综合运用高密度电阻率成像法、音频大地电磁法和测氡法对贵州都匀和广西融安碳酸盐岩区的2个油气靶区进行了地下构造识别,结果表明:高密度电阻率成像法和音频大地电磁法能有效确定浅地表地下低阻构造的位置、宽度和产状,高密度电阻率成像法在50 m以浅深度拥有更高的分辨率,音频大地电磁法探测深度更深,但对地下介质的分辨率不高,氡气测量能很好地识别地下低阻构造的属性。高密度电阻率成像法、音频大地电磁法与测氡法三者可优势互补,组成有效识别岩溶区近地表地质结构构造的技术方法体系,可为南方岩溶区页岩气钻井避开近地表强岩溶发育带、断层破碎带以及最终位置的确定提供可靠的技术支撑。  相似文献   
85.
过林  马莉  叶诗淳 《东北测绘》2012,(1):150-153
针对频域变换的旋转不变纹理特征,提出Radon变换结合树型小波变换的纹理特征提取方法。以Radon变换处理影像将影像纹理的旋转转化成平移信息,对变换后的影像进行非完全树型小波变换。此时可以将能量作为旋转不变纹理特征,但得到的小波系数所携带信息较少,所以本文采用小波系数直方图作为纹理特征。采用此方法对居民地进行提取,实验结果表明利用该方法能得到比较有效稳定的旋转不变纹理特征,并且对不同的中小比例尺遥感影像都有较好的适应性。  相似文献   
86.
在深海多缆、长拖缆地震勘探的各种噪音影响中,多次波对深层的有效反射影响难以消除。笔者介绍了一种高分辨率各向异性 Radon 变换方法,在 Radon 变换积分路径中增加非椭圆率 eta 参数,将传统 Radon 变换积分曲线由慢度、偏移距两参数改为慢度、偏移距及非椭圆率三参数,更好地刻画了长偏移距下反射非双曲时差。通过对某海域实际采集的多缆长偏移距地震数据进行压制多次波处理,与传统方法相比取得了较为理想的效果,为后续深层构造成像提供了基础数据。  相似文献   
87.
The Badgastein spa shows almost all the special geological and hydrological features existing in the northeastern central Alps. Situated within the Tauern window, the open joint system enables the infiltration of surface water to great depths. There it becomes heated and loaded with radon and trace elements such as fluor. The water discharges as thermal water springs at the steep right flank of the cascade of the Gastein-Ache. This hydraulic process occurs during a span of 3600–3800 years. The springs are captured in galleries, and the largest discharge is in gallery IX (2518 m3/d–1). The spa became known worldwide in the 19th century by visiting aristocrats from Central and Eastern Europe. The most important event in the 20th century was the discovery of the heat joint in the Böckstein gallery. In 1940 an effort to reactivate gold mining in the Radhausberg near Böckstein south of Badgastein failed. However, the miners had the unexpected experience of being cured of rheumatism. A connection between the great depth and high temperature in the gallery was made by the discovery of the joint set with heat and radon emanation. In the medical stations of the Böckstein gallery treatment of polyarthritis has become especially successful.  相似文献   
88.
吴慧山  林玉飞 《铀矿地质》1995,11(2):106-109
本文介绍了放射性同位素氡和镭测量在油气勘查与开采中的某些应用和相应的机理。  相似文献   
89.
Radon anomalies on three kinds of faults in California   总被引:1,自引:0,他引:1  
Radon emanation is known to be anomalously high along active faults in many parts of the world. We tested this relationship in California during July and early August 1992, using a portable radonmeter to conduct soil-air radon surveys at 5 sites across three kinds of faults: Creeping, locked, and freshly broken.Along a 350-m long survey line across a creeping segment of the San Andreas fault at Nyland Ranch in San Juan Bautista, we found anomalous radon concentrations not in the creep zone itself as determined by a creepmeter, but on the adjacent sides, 10 and 30 meters from the center line of the fault. The anomalous values were 5 times higher than the background values measured farther away from the fault. A similar radon anomaly was observed along a 420-m long survey line across a creeping segment of the Calaveras fault near 7th Street in Hollister. There, the anomalous values were about 6 to 11 times the background values and about 40 and 50 m from the center line of the fault. The double-peaked featire of the anomalies may be indicative of a relatively low gas permeability of the fault-gouge materials in the creeping zones and high permeability of fractured rocks in the adjacent shear zones.Along a 144-m survey line across the currently locked segment of the San Andreas fault at the Earthquake Trail near Olema, the radon concentration was indeed anomalously high in the fault zone, by a factor of two above background values. However, the maximum values (3 to 6 times background) again were recorded about 10 meters from the center line.Three weeks after the magnitude 7.5 Landers earthquake of 28 June 1992, we conducted a survey along a 300-m line across the earthquake fault alongside Encantado Road in the epicenter area. The radon values measured at the two main fault breaks were an order of magnitude higher than the background values. A similar result was found along a 420-m line alongside Reche Road about 1.7 km south of Encantado Road.  相似文献   
90.
鹤壁井煤燃烧的水氡效应分析   总被引:1,自引:0,他引:1  
杜广仁 《地震》1994,(5):92-96
本文通过鹤壁深井煤层特大火灾热源的影响导致的井水氡变化实例,验证了鹤壁井水氡化学组分在温压条件发生变化时具有灵敏的反映。水氡变化曲线图象表现为氡值下降,并讨论了其形成机制。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号