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991.
一种新的基于高斯混合模型的纹理图像分割方法 总被引:1,自引:0,他引:1
提出了一种新的结合了小波变换的高斯混合模型纹理分割方法。该方法包括预处理、小波变换、模型训练、计算后验概率和标记图像等5个阶段,并分析了将高斯混合模型引入纹理分割需要注意的几个方面。试验结果表明,该算法具有较好的分割性能。 相似文献
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Jörg F. Wagner 《GPS Solutions》2005,9(3):179-193
During the last years, the International Symposia on Precision Approach and Automatic Landing (ISPA) have shown a considerable change in the significance of integrated landing systems. At the first ISPA conference in 1995, the combination of inertial sensors and GNSS receivers was thoroughly discussed and appeared to be a very promising concept, especially with respect to ‘Integrity’ and ‘Continuity’. Ever since, this particular combination of sensors has received little attention. A comprehensive discussion of the technical background of this setback for integrated landing systems did not take place, primarily because of the popular opinion that the Kalman filter algorithm, which is the system integration kernel, is not sufficiently stable. The true reason has meanwhile been identified. The aiding of an inertial navigation system by only one GNSS antenna is insufficient in phases of low aircraft dynamics such as in the case of final approach. Instead, a multi-antenna system is required with antennas widely distributed over the aircraft structure. This latter approach, however, causes problems due to structural flexibilities. To show that an integrated system based on inertial sensors and widely distributed GNSS antennas is technically feasible, the paper discusses the following topics. (1) Unstable system performance during final approach for 1-antenna-aiding. (2) Improving the system performance prior to using additional antennas. (3) Effect of the antenna distribution. (4) Integrated systems for distributed sensors and flexible aircraft structures. The paper shows that integrated systems are still an attractive candidate for automatic landing equipment preserving the advantages with respect to ‘Integrity’ and ‘Continuity’. 相似文献
995.
An efficient method is proposed for the analysis of atmospheric pressure effects on gravity variations. It processes gravity
and pressure signals using an orthogonal filter bank derived from high-degree Daubechies wavelets. The method introduces the
atmospheric pressure admittance, which is both time- and frequency-dependent, and thus provides more information about when
and how the frequency components in the pressure signal influence gravity variations. We demonstrate the efficiency of the
wavelet method by applying it to observations from the Wuhan (China) superconducting gravimeter station. The analysis of gravity
and pressure signals in 14 sub-bands with different bandwidths covering a frequency range from 0.176 to 720 cpd (cycles per
day) reveals that local atmospheric pressure fluctuations start to induce obvious effects on gravity variations in the seismic
band 0.52–1.04 mHz (periods 16 to 32 min) and highly correlate with gravity variation in the long-period seismic mode band
0.26–0.52 mHz (periods 32–64 min). The harmonics of solar-heating-induced atmospheric tides play a leading role in interfering
with the variation of gravity residuals in the frequency band 0.704–11.25 cpd (periods 128 min to 1.42 day). Local atmospheric
pressure effects on gravity variation are very strong in the frequency band 0.176–0.704 cpd (periods 1.42–5.69 day). Accurately
filtering quarter-diurnal tides into a narrow band further demonstrates the efficiency of the wavelet method. After removing
secular gravity changes and long-period atmospheric pressure variations, we show that there are obvious variations of local
pressure admittance on time scales of hours to days. We also reveal seasonal variability of pressure admittances in the band
0.176–0.352 cpd (periods 2.84–5.69 day) after removing the effects of solar-heating atmospheric tides. 相似文献
996.
一种针对激光雷达强度图像的滤波算法研究 总被引:5,自引:1,他引:5
基于激光雷达数据的特点.提出了一种融合的中值滤波算法。运用此算法和传统的中值滤波算法以及均值算法对激光雷达数据进行了处理,并且使用多种指标对处理的结果进行了比较,证明本算法既保持了传统中值滤波的优点,又改进了对弱边缘目标的保护。 相似文献
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Optimum design of structures for earthquake is achieved by simulated annealing. To reduce the computational work, a fast wavelet transform is used by means of which the number of points in the earthquake record is decreased. The record is decomposed into two parts. One part contains the low frequency of the record, and the other contains the high frequency of the record. The low‐frequency content is the effective part, since most of the energy of the record is contained in this part of the record. Thus, the low‐frequency part of the record is used for dynamic analysis. Then, using a wavelet neural network, the dynamic responses of the structures are approximated. By such approximation, the dynamic analysis of the structure becomes unnecessary in the process of optimization. The wavelet neural networks have been employed as a general approximation tool for the time history dynamic analysis. A number of structures are designed for optimal weight and the results are compared to those corresponding to the exact dynamic analysis. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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流量过程线分割方法的分析探讨 总被引:8,自引:3,他引:8
对流量过程线分割方法进行了深入的研究,讨论了对基流问题的认识,给出了较合理的基流定义;分析探讨了几种常见的流量过程线分割方法以及存在的问题,并对这些分割方法从物理成因和水文产汇流规律等方面进行了比较研究。 相似文献
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