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991.
针对高差对于地貌类型定义、不同地貌类型范围划定以及山地灾害危险性评价的重要意义,该文将坡脚的高程定义为基准高程,提出了动态窗口邻域统计的高差计算方法。计算每个栅格到坡脚的距离,作为该栅格的对应的窗口半径;利用邻域统计的方法,搜索该窗口范围内的最低高程值,即为坡脚的高程,作为该栅格高差计算的基准高程;最终通过高程值与基准高程相减运算,获取每个栅格点对应的高差。选取四川省都江堰市虹口地区为研究区,对比两种不同的高差计算方法。结果显示:在山脊和山肩部位,动态窗口计算的高差值大于静态窗口的高差值,而位于山脚动态窗口计算的高差值小于静态窗口计算的高差值;利用动态窗口获得的高差的精度明显高于静态窗口的计算结果,其平均偏差由75.53降低为13.24。 相似文献
992.
993.
王新洲 《武汉大学学报(信息科学版)》1994,19(4):315-321
应用贝叶斯统计理论推导了序贯平差公式.按本文推导的公式进行贝叶斯序贯平差,得到的未知参数X的贝叶斯估值与按经典序贯平差得到的结果完全相同,但单位权方差σ2的贝叶斯估值却与按经典平差方法得到的结果相差一个因子. 相似文献
994.
多光谱遥感图像的自适应各向异性扩散滤波 总被引:1,自引:0,他引:1
图像滤波预处理不仅有助于增强图像信噪比和减少类间(intra-c lass)光谱可变性,而且还能够对影像中亮度均匀的区域进行平滑,从而为影像地物识别、分割和分类提供有力的支持。在Pope和Acton提出的两个多光谱图像各向异性扩散滤波模型的基础上,通过各向异性扩散和稳健统计学的联系,建立了基于B iwe ight Estim ator误差模型的扩散系数,同时利用非线性退化技术对梯度阈值的改进,提出了两个基于各向异性扩散方程的非线性滤波方法。提出的方法不仅能够有效地消除传感器随机噪声的影响,而且还能够很好地保持遥感图像上重要的细节边缘和影像质量。实验结果表明,不论是视觉效果还是质量统计分析,提出的扩散模型的性能优于Pope和Acton的各向异性扩散模型,是理想的多光谱图像保边缘滤波方法。 相似文献
995.
A new unbiased plotting position formula for Gumbel distribution 总被引:1,自引:0,他引:1
The probability plots (graphical approach) are used to fit the probability distribution to given series, to identify the
outliers and to assess goodness of fit. The graphical approach requires probability of exceedence or non exceedence of various
events. This is obtained through the use of plotting position formula. In literature many plotting position formulae have
been reported. All of the many existing formulae provide different results particularly at the tails of the distribution and
hence there is need of unbiased plotting position formulae for different distributions. Expression for the largest expected
order statistics is found in a simple form. Using exact plotting position from Gumbel order statistics a new unbiased plotting
position formula has been developed for the Gumbel distribution. The developed formula better approximates the exact plotting
positions as compared to other existing formulae. 相似文献
996.
一次灾害性地震之后,有关部门分别提供的评估数字有时差别很大。该文据全世界地震灾害记录资料,提出并讨论以下事实;各家提供的地震评估数字普遍左别。一般比较来看,人员死亡数的差别较小,经济损失数额评估的差别较大。地震灾害经济损失评估的差别,将随着社会经济的发展和文化物质生活的不断提高而继续存在甚至扩大。 相似文献
997.
998.
本文引进应用极值顺序统计量推断一个概率分布尾部性质的方法,并介绍了参数估计的方法。文中举例说明如何应用这一理论预测灾害性地震。这种方法比传统极值方法更适用于无季节性变化的数据。 相似文献
999.
Alpine cold ecosystem with permafrost environment is quite sensitive to climatic changes and the changes in permafrost can significantly affect the alpine ecosystem. The vegetation coverage, grassland biomass and soil nutrient and texture are selected to indicate the regime of alpine cold ecosystems in the Qinghai-Tibet Plateau. The interactions between alpine ecosystem and permafrost were investigated with the depth of active layer, permafrost thickness and mean annual ground temperature (MAGTs). Based on the statistics model of GPTR for MAGTs and annual air temperatures, an analysis method was developed to analyze the impacts of permafrost changes on the alpine ecosystems. Under the climate change and human engineering activities, the permafrost change and its impacts on alpine ecosystems in the permafrost region between the Kunlun Mountains and the Tanggula Range of Qinghai-Tibet Plateau are studied in this paper. The results showed that the per- mafrost changes have a different influence on different alpine ecosystems. With the increase in the thickness of active layer, the vegetation cover and biomass of the alpine cold meadow exhibit a significant conic reduction, the soil organic matter content of the alpine cold meadow ecosystem shows an exponential decrease, and the surface soil materials become coarse and gravelly. The alpine cold steppe ecosystem, however, seems to have a relatively weak relation to the permafrost environment. Those relationships resulted in the fact that the distribution area of alpine cold meadow decreased by 7.98% and alpine cold swamp decreased by 28.11% under the permafrost environment degradation during recent 15 years. In the future 50 years the alpine cold meadow ecosystems in different geomorphologic units may have different responses to the changes of the permafrost under different climate warming conditions, among them the alpine cold meadow and swamp ecosystem located in the low mountain and plateau area will have a relatively serious degradation. Furthermore, from the angles of grassland coverage and biological production the variation characteristics of high-cold eco- systems in different representative regions and different geomorphologic units under different climatic conditions were quantitatively assessed. In the future, adopting effective measures to protect permafrost is of vital importance to maintaining the stability of permafrost engineering and alpine cold eco- systems in the plateau. 相似文献
1000.
Dion Weatherley 《Pure and Applied Geophysics》2006,163(9):1933-1947
The recurrence interval statistics for regional seismicity follows a universal distribution function, independent of the tectonic
setting or average rate of activity (Corral, 2004). The universal function is a modified gamma distribution with power-law
scaling of recurrence intervals shorter than the average rate of activity and exponential decay for larger intervals. We employ
the method of Corral (2004) to examine the recurrence statistics of a range of cellular automaton earthquake models. The majority
of models has an exponential distribution of recurrence intervals, the same as that of a Poisson process. One model, the Olami-Feder-Christensen
automaton, has recurrence statistics consistent with regional seismicity for a certain range of the conservation parameter
of that model. For conservation parameters in this range, the event size statistics are also consistent with regional seismicity.
Models whose dynamics are dominated by characteristic earthquakes do not appear to display universality of recurrence statistics. 相似文献