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71.
采用InSAR形变监测资料计算2015年西藏定日MW5.7地震同震形变场,反演发震断层几何参数和滑动分布。在此基础上,研究尼泊尔MW7.8主震对定日地震的静态库仑应力触发影响。综合分析地震滑动机制和构造特征,认为定日断层为西倾隐伏断层。反演结果表明,地震破裂相对集中,主要深度在6~9 km,破裂以正断滑动为主。发震断层走向约178°,倾角约 48°,破裂区长约5 km,宽约5 km,最大滑动量约0.2 m,释放的地震矩约3.7×1017 N·m,对应矩震级MW5.6。尼泊尔主震同震库仑应力在定日地震震源处约为0.2 bar,造成藏南申扎-定结拉张地堑应变加载。 相似文献
72.
Modeling and quality control for reliable precise point positioning integer ambiguity resolution with GNSS modernization 总被引:3,自引:2,他引:1
Recent research has demonstrated that the undifferenced integer ambiguities can be recovered using products from a network solution. The standard dual-frequency PPP integer ambiguity resolution consists of two aspects: Hatch-Melbourne-Wübbena wide-lane (WL) and ionosphere-free narrow-lane (NL) integer ambiguity resolution. A major issue affecting the performance of dual-frequency PPP applications is the time it takes to fix these two types of integer ambiguities, especially if the WL integer ambiguity resolution suffers from the noisy pseudorange measurements and strong multipath effects. With modernized Global Navigation Satellite Systems, triple-frequency measurements will be available to global users and an extra WL (EWL) model with very long wavelength can be formulated. Then, the easily resolved EWL integer ambiguities can be used to construct linear combinations to accelerate the PPP WL integer ambiguity resolution. Therefore, we propose a new reliable procedure for the modeling and quality control of triple-frequency PPP WL and NL integer ambiguity resolution. First, we analyze a WL integer ambiguity resolution model based on triple-frequency measurements. Then, an optimal pseudorange linear combination which is ionosphere-free and has minimum measurement noise is developed and used as constraint in the WL and the NL integer ambiguity resolution. Based on simulations, we have investigated the inefficiency of dual-frequency WL integer ambiguity resolution and the performance of EWL integer ambiguity resolution. Using almanacs of GPS, Galileo and BeiDou, the performances of the proposed triple-frequency WL and NL models have been evaluated in terms of success rate. Comparing with dual-frequency PPP, numerical results indicate that the proposed triple-frequency models can outperform the dual-frequency PPP WL and NL integer ambiguity resolution. With 1 s sampling rate, generally, only several minutes of data are required for reliable triple-frequency PPP WL and NL integer ambiguity resolution. Under benign observation situations and good geometries, the integer ambiguity can be reliably resolved even within 10 s. 相似文献
73.
Integer ambiguity validation is an essential quality control step for high-precision positioning and navigation with global navigation satellite systems (GNSS). In order to validate the resolved integer ambiguities, statistical tests, such as the R-ratio test, F-ratio test, W-ratio test, difference test, and projector test, have been favored. In practice, the critical values for these statistical tests are determined either empirically or from the assumed distributions. However, previous research has revealed that some of these statistics have upper bounds, which can be obtained from simulations. In this contribution, we find that under the framework of the integer aperture estimation, the upper bounds for these ambiguity validation statistical tests can be derived without actual measurements or simulation. As a result, the assumed distributions for these statistical tests are inappropriate. According to the derivation, it has been concluded that the upper bounds of these ambiguity validation tests depend only on the ambiguity geometry (e.g., the float ambiguity variance–covariance matrix) and can be obtained at the design stage of GNSS positioning. Thus, the critical value for these ambiguity validation statistics has a rigorous range, and it should be chosen to be smaller than a priori derived upper bound. Otherwise, no integer ambiguities can be obtained. 相似文献
74.
以2012年"泰利"和"苏拉"台风期间的福州台和漳州台秒采样的重力固体潮为研究对象,首先通过巴特沃斯高通滤波,提取出重力固体潮中高频的台风扰动;其次采用傅里叶变换分析福州台和漳州台重力的功率谱特征。分析结果表明:台风中心距台站越近、风速越大、气压越低,重力固体潮的扰动也越明显。"泰利"和"苏拉"台风引起的重力扰动主要频率范围为0.16~0.28 Hz,而福州台和漳州台无台风影响时的正常重力地脉动脉动频率为0.25~0.35 Hz。 相似文献
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76.
Experimental Simulations of Extreme Precipitation Based on the Multi-Status Markov Chain Model
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A multi-status Markov chain model is proposed to produce daily rainfall, and based on which extreme rainfall is simulated with the generalized Pareto distribution (GPD). The simulated daily rainfall shows high precision at most stations, especially in pluvial regions of East China. The analysis reveals that the multistatus Markov chain model excels the bi-status Markov chain model in simulating climatic features of extreme rainfall. Results from the selected six stations demonstrate excellent simulations in the following aspects:standard deviation of monthly precipitation,daily maximum precipitation,the monthly mean rainfall days,standard deviation of daily precipitation and mean daily precipitation, which are proved to be consistent with the observations. A comparative study involving 78 stations in East China also reveals good consistency in monthly mean rainfall days and mean daily maximum rainfall, except mean daily rainfall. Simulation results at the above 6 stations have shown satisfactory fitting capability of the extreme precipitation GPD method. Good analogy is also found between simulation and observation in threshold and return values. As
the errors of the threshold decrease, so do the di?erences between the return and real values. All the above demonstrates the applicability of the Markov chain model to extreme rainfall simulations. 相似文献
77.
南京市历史文化层中土壤重金属元素的分布规律初探 总被引:14,自引:2,他引:12
文章对南京市城区不同地点出现的多个文化层中土壤的理化特征进行了系统研究。研究结果表明,文化层中土壤的重金属元素含量比南京市非城市土壤和背景平均值有增高的趋势,局部地段有巨量增高。从剖面纵向上看(时间上),这种增高现象主要发生在近现代、明清和六朝3个历史时期,这与历史上这些时期南京相对发达有关;而从横向地域上看(空间上),重金属元素含量的分布明显可以分成两组,两个组分别代表了地域上的不同,如明故宫-大行宫-中山东路一带历史上许多时期是皇城区,而内秦淮河流域一带则可能是古代的手工业和制造业区、商贸区和普通大众的生活区,这种明显的差别揭示出南京在各历史时期上的城市功能区是各不相同的。磁化率特征研究结果表明文化层中土壤的磁化率在各历史时期分布是不同的,磁化率的高峰时期有近现代、清朝和明朝时期;频率磁化率特征研究结果表明磁性矿物主要是外源输入造成的。与此同时磁化率高峰时期基本上与重金属元素增高地段是一致的,这进一步印证了文化层中重金属元素增高主要是由于外源污染物质的输入造成的。 相似文献
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79.
80.
GPS无线电掩星技术监测地球大气 总被引:6,自引:0,他引:6
GPS无线电掩星技术是从行星掩星(飞行器)探测行星大气[1~3]的遥感技术发展而来的。1995年4月3日小型卫星MicroLab1的发射升空,标志着以GPS无线电掩星建议为基础GPS/MET计划纳入了正式实验阶段。实验结果证实了GPS无线电掩星技术在探测地球大气方面潜在的科学价值与实用意义。简要系统地介绍了利用GPS无线电掩星技术监测地球大气折射率、温度、气压和水蒸汽丰度等物理参量廓线分布的基本原理、主要误差源和空间分辨率,以及数字模拟结果和初步实验结果,并分析了GPS无线电掩星技术在监测全球气候变化和提高数值天气预报精度等方面的潜在贡献。 相似文献