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721.
提出了一种利用天文观测手段获取的CCD图像序列对空间碎片进行自动识别和追踪的方法。该方法采用计算机图像处理、图像识别与分析和计算机视觉等相关技术,自动识别出每幅CCD图像中的空间碎片以及背景恒星等空间目标,并定量计算其有关特征;然后根据空间碎片移动较快的特点,在CCD图像序列中结合基于Snake模型的主动轮廓追踪和特征相似性比较两种方法,对其中出现的空间碎片目标进行自动识别和追踪。实验结果显示,该方法能准确地对空间碎片目标进行自动识别和追踪。 相似文献
722.
This article presents a new public domain tool for generalized Lagrangian particle tracking in rivers. The approach can be applied with a variety of two- and three-dimensional flow solvers. Particle advection by the flow is incorporated using flow fields from the chosen solver assuming particles follow the Reynolds-averaged flow, although some other simple passive and active particle behaviors are also treated. Turbulence effects are treated using a random walk algorithm with spatial step lengths randomly chosen from Gaussian distributions characterized by the diffusivity from the flow solver. Our work extends this concept to a general framework that is solver and coordinate system independent to allow easy comparisons between differing flow treatments. To better treat problems where detailed information is required in specific regions, the approach includes novel cloning and colligation algorithms which enhance local resolution at modest computational expense. We also provide tools for computing local concentrations and total exposure over a user-specified time interval. Several examples of predictions are provided to illustrate applications of the technique, including examination of the role of curvature-driven secondary flows, storage in lateral separation eddies, treatment of larval drift, treatment of fuel spill dispersion, river-floodplain connections, and sedimentation in floodplain ponds by tie channel connections. We also demonstrate that the model can reproduce analytically derived concentration profiles for simple diffusivities. These examples show that the Lagrangian particle tracking approach and the extensions proposed here are broadly applicable and viable for treating difficult river problems with multiple temporal and spatial scales. The examples also illustrate the utility of the cloning/colligation extensions and show how these can decrease the computational effort required on problems where high local resolution is required. Enhancement of the tools and even broader applicability can be achieved through the inclusion of multiple particle populations and particle–particle interactions. 相似文献
723.
724.
基于WRF-WVT水汽追踪模式,对2022年6—8月长江流域极端干旱情况下的水循环进行模拟研究,分析了长江流域蒸散发对长江流域局地和非局地降水的影响。结果表明,2022年夏季干旱导致长江中下游陆地水储量在5—8月期间减少100~150 mm。6—8月长江流域约45%的蒸散发在当地和华北形成降水,其中6月长江流域蒸散发主要贡献当地降水,而7、8月对当地和华北降水的贡献大致相等。6—8月长江流域蒸散发贡献的当地降水逐月减少,总量为8.2×107 m3(长江流域平均91.2 mm),并且降水强度越高当地蒸散发贡献率越小,对当地降水贡献最大的区域为四川盆地附近(最大超过40%)。长江流域蒸散发为华北提供的降水在6—8月先增多后小幅度减少,总量为5.3×107 m3(华北平均58.4 mm),并且降水强度越高长江流域蒸散发贡献率越大。2022年夏季长江流域蒸散发对当地和华北地区暴雨的贡献率都为12%左右。 相似文献
725.
Hydrocarbon micro and macro seeps alter chemical and mineral composition of the Earth’s surface, providing prospects for detection with remote sensing tools. There have been several studies focusing on mapping these anomalies by utilizing ever evolving multispectral and hyperspectral imaging instruments, which has proven their capacity for mapping both hydrocarbons and hydrocarbon-induced alterations so far. These studies broadly comprise of methods like calculating band ratios, spectral angle mapping, spectral feature fitting, and principal component analysis as detection techniques. However, there is a lack of concentration on advanced signature based detection algorithms and unmixing methods for mapping surface manifestations of hydrocarbon microseeps. Signature based detection algorithms utilize target spectra to correlate with each pixel’s spectrum in order to allocate possible target locations. Unmixing methods, on the other hand, require no input spectra beforehand, aiming to resolve each pixel’s spectral constituents and their corresponding abundance fractions. In this paper, the potential of all these methods in mapping microseepage related anomalies are evaluated by implementing and comparing them for Gemrik Anticline, one of the prospective hydrocarbon exploration fields in Turkey. Hence, it provides a complete knowledge on determination surface manifestations of hydrocarbon microseeps with the help of well known supervised target detection algorithms and hyperspectral unmixing algorithms. The study area is located in the Southeastern Anatolia, between the cities of Adıyaman and Şanlıurfa. The spectral signatures were collected with Analytical Spectral Devices Inc. (ASD) spectrometer during the field studies conducted by Avcıoğlu (2010), to be utilized as an input to the signature based detection algorithms as well as a reference to select the related abundance map among the outputs of unmixing methods. Advanced Space Borne Thermal Emission and Radiometer (ASTER) image of the study region, with an atmospheric correction before running the algorithms, is selected for the applications. Among the applied algorithms, Simplex Identification via Split Augmented Lagrangian (SISAL) is selected as a base of comparison, as it possess minimum calculated error metrics in the experiments. Another unmixing method, the Minimum Volume Simplex Algorithm (MVSA), and signature-based techniques, Desired Target Detection and Classification Algorithm (DTDCA) & Spectral Matched Filter (SMF) follow the success of the SISAL, respectively. The Crosta technique, which is performed as a conventional approach for experimental comparisons, has also shown its capability, succeeding these algorithms. The study provides an overall assessment for methodologies to be used for hydrocarbon microseepage mapping, which also serves guidance for further exploration studies in the region. The potential of ASTER data for hydrocarbon-induced alterations is also emphasized as a cost effective tool for the future applications. 相似文献
726.
基于AIS信息校准的双频地波雷达的船只融合跟踪 总被引:2,自引:0,他引:2
高频地波雷达(HFSWR)和自动船只确认系统(AIS)是船只跟踪的重要传感器。高频地波雷达可以用来跟踪探测区域的所有船只,而AIS只能用来确认合作船只的信息。由于海杂波的干扰,使用单频率地波雷达的船只跟踪会淹没在布拉格峰值的盲区里,改变探测频率是克服这一缺点的有效手段。在这种背景下,我们提出一种基于AIS校准的双频雷达融合探测算法。因为不同频率的地波雷达测量与AIS的测量值存在系统误差,所以AIS信息可以用来估计和校准地波雷达的每个频率的系统误差。首先,将合作目标的点迹测量与地波雷达的点迹测量通过JVC分配算法进行点迹关联。从合作船只的点迹关联结果中,双频雷达的系统误差可以估计和校准。其次,基于校准的双频雷达数据,使用融合JPDA-UKF算法进行船只跟踪。通过真实探测的数据的实验结果显示所提算法可以实时跟踪船只,相比单频率跟踪可以进一步提高跟踪能力和跟踪精度。 相似文献
727.
728.
基于SAR偏移量跟踪法提取岗纳楼冰川流速 总被引:2,自引:1,他引:1
冰川动态变化监测有助于反映全球和区域气候演变,保护自然环境和自然资源。近年来,基于SAR数据研究冰川运动已成为主流技术之一。基于SAR提取冰川流速主要包括合成孔径雷达干涉测量、多孔径雷达干涉和偏移量追踪法。本文采用SAR偏移量追踪法中的强度追踪法,提取青海省哈拉湖东北部岗纳楼冰川沿距离向、方位向的冰川流速。试验结果表明,距离向冰川运动速度提取效果较好,最大流速达15.36 m/a,流速从中轴向两侧递减,在冰舌末端趋于0;方位向提取的冰流速最大达18.27 m/a,但因电离层干扰,方位向流速图中存在一些方位向条纹。此外,由于冰流速在方位向分量小等因素的影响,本文研究提取的方位向流速精度低于距离向。 相似文献
729.
考虑参考输入由外系统给出的状态含有时滞的线性系统在正弦干扰下的最优输出跟踪问题.利用逐次逼近法,通过构造线性非齐次两点边值问题序列,求得了用于补偿时滞的伴随向量.分别利用参考输入外系统状态、干扰及其导数信号引入前馈控制作用.得到的控制律包含精确反馈项、前馈项和伴随向量极限形式的时滞补偿项.通过引入参考输入观测器解决由于引入外系统状态而导致的前馈控制律的物理不可实现问题.仿真结果表明该方法的有效性. 相似文献
730.