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281.
282.
把走时CT结果作为地震衍射CT(DCT)的背景场可以改善DCT之成像质量。本文由Radon变换、泛函分析变分原理和微分几何导出程函方程后,采取有限差分法求解,实行波前追踪。通过对反射地震勘探和VSP 结构的源——接收系统编程实际运算,表明该波前追踪程序输入简单,适合于多层介质模型,各网格点的走时能迅速确定。 相似文献
283.
Variationofstressfieldinthesourceregionaroundastrongshock:anexampleGut-LingDIAO(刁桂苓),Li-MinYU(于利民)andQin-ZuLI(李钦祖)(Seismologi... 相似文献
284.
285.
黄河中游马兰黄土中若干微量元素的平均含量及相关性研究 总被引:1,自引:0,他引:1
本文根据采自山西,陕西,甘肃,宁夏四省区71个县市的130个样点,共147块马兰黄土样品中17种微量元素的分析结果,对马兰黄土中微量元素的含量和区域分布特征及相关性进行了研究。 相似文献
286.
针对点质量核径向基函数应用于局部重力场建模中的设计矩阵严重病态问题,本文引入Tikhonov正则化方法对传统点质量核径向基函数方程进行改造,建立了相应的正则化模型。通过模拟数据进行仿真实验,以传统格网化方法作为对比试验,利用"标靶法"确定两种模型的最优结构。实验结果表明:正则化点质量核径向基函数可以直接利用离散数据进行局部重力场建模。在两种模型的最优结构下,当实测数据无污染时,正则化方法达到与传统格网化方法相当的精度;当实测值中加入3 mGal的高斯白噪声时,正则化方法的精度获得了27.9%的提升。这说明本文方法可以应用于局部重力场建模中,且模型结构更优,抗干扰能力更强。 相似文献
287.
针对水下潜器搭载的惯性导航系统圆锥运动这一复杂特性,研究经典多子样算法、优化多子样算法、扩展圆锥误差补偿算法和基于四元数微分方程迭代算法的姿态求解精度与适用性情况,并以圆锥运动作为测试输入进行仿真实验.结果表明,采用子样数大于3的迭代算法进行水下重力辅助惯性导航姿态解算,能够满足角度漂移小于1″/h的精度要求. 相似文献
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289.
On May 12, 2008, a magnitude 7.9 earthquake ruptured the Longmenshan fault system in Sichuan Province, China, collapsing buildings
and killing tens of thousands people. As predicted, aftershocks may last for at least one year, and moreover, large aftershocks
are likely to occur. Therefore, it is critical to outline the areas with potential aftershocks before reconstruction and re-settling
people as to avoid future disasters. It is demonstrated that the redistribution of stress induced by an earthquake should
trigger successive seismic activity. Based on static stress triggering theory, we calculated the coseismic stress changes
on major faults induced by the Wenchuan earthquake, with elastic dislocation theory and the multilayered crustal model. We
also discuss the stress distribution and its significance for future seismic activity under the impact of the Wenchuan earthquake.
It is shown that coulomb failure stress (CFS) increases obviously on the Daofu-Kangding segment of the Xianshuihe Fault, the
Maqu and Nanping segment of the Eastern Kunlun Fault, the Qingchuan Fault, southern segment of the Minjiang Fault, Pengxian-Guanxian
Fault, Jiangyou-Guangyuan Fault, and Jiangyou-Guanxian Fault. The increased stress raises the probability of earthquake occurrence
on these faults. Since these areas are highly populated, earthquake monitoring and early disaster alarm system are needed.
CFS increases with a magnitude of 0.03–0.06 MPa on the Qingchuan Fault, which is close to the northern end of the rapture
of Wenchuan earthquake. The occurrence of some strong aftershocks, including three events with magnitude higher than 5.0,
indicates that the seismic activities have been triggered by the main shock. Aftershocks seem to migrate northwards. Since
the CFS change on the Lueyang-Mianxian Fault located on the NEE of the Qingchuan Fault is rather small (±0.01 MPa), the migration
of aftershocks might be terminated in the area near Hanzhong City. The CFS change on the western Qinling Fault is around 10
Pa, and the impact of static triggering can be neglected. The increment of CFS on the Pengxian-Guanxian Fault and Beichuan-Yingxiu
Fault southwest to the main rupture is 0.005–0.015 MPa, which would facilitate earthquake triggering in these areas. Very
few aftershocks in these areas indicate that the accumulated stress has not been released sufficiently. High seismic risk
is predicated in these areas due to co-seismic CFS loading. The Wenchuan earthquake released the accumulated CFS on the Fubianhe
Fault, the Huya Fault, the Ha’nan-Qingshanwan Fault, and the Diebu-Bailongjiang Fault. The decrement of CFS changes on the
Longquanshan Fault east to Chengdu City is about 0.002 MPa. The seismic activity will be depressed by decrement of CFS on
these faults.
Supported by Knowledge Innovation Program of Chinese Academy of Sciences (Grant No. KZCX-SW-153), National Natural Science
Foundation of China (Grant Nos. 40574011 and 40474028) 相似文献
290.
Based on the earthquake catalog reported by the Chinese digital seismic network in recent years, we select the earthquakes with both surface wave magnitude and local magnitude and fit them into a relationship between the two magnitudes. The systematic difference is found from the formula which has been used for 30 years. Because of a large dynamic range and wide frequency range of the current digital observation system, in addition to a larger number of stations and earthquakes being used compared to before, the relation obtained in this paper seems more reliable. Our calculation shows that there is no significant difference before and after magnitude conversion so we suggest the abandonment of magnitude conversion. The site response of a station consists of amplification at different frequencies. The amplification is equal to about 1 and changes little with frequency at stations located on basement rock, and it is greater than 1 at low frequency ranges and less than 1 at high frequency ranges at stations located on sediment layers. The difference between magnitudes from single station located on sediment layer and the average magnitude from the whole network increases from negative to positive with period. It seems that there is no fixed station correction factor and the station correction method does not work to improve the accuracy and magnitude estimates. 相似文献