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121.
122.
利用广西邕宁、灵山地应力资料预报周边地区中强震发震时间的初步探讨 总被引:1,自引:1,他引:0
采用回归分析及周期分析法消除了广西邕宁和灵山地应力测值因观测室室温、湿度等因素所引起的年变化;又对地应力资料做了去除长趋势变化和用卡尔曼滤波平滑地应力曲线的处理后,可以看出邕宁、灵山地应力对于200km范围内的Ms4.5—4.7级地震、300km范围内的Ms4.8—5.4级地震以及400km范围内的M5≥5.5级地震具有一定的预报能力。在中强震发生之前的2年内,邕宁、灵山地应力某分向会出现2次以上的超1.5倍均方差异常,且在2次异常所跨越的时段内至少另有1个分向也会显示有1次以上的异常,当第2次异常结束后的8个月内,在上述规定的距离范围内发生中强震的可能性很大。 相似文献
123.
Pine plantations in Australia are subject to a range of abiotic and biotic damaging agents that affect tree health and productivity. In order to optimise management decisions, plantation managers require regular intelligence relating to the status and trends in the health and condition of trees within individual compartments. Remote sensing technology offers an alternative to traditional ground-based assessment of these plantations. Automated estimation of foliar crown health, especially in degraded crowns, can be difficult due to mixed pixels when there is low or fragmented vegetation cover. In this study we apply a linear spectral unmixing approach to high spatial resolution (50 cm) multispectral imagery to quantify the fractional abundances of the key image endmembers: sunlit canopy, shadow, and soil. A number of Pinus radiata tree crown attributes were modelled using multiple linear regression and endmember fraction images. We found high levels of significance (r2 = 0.80) for the overall crown colour and colour of the crown leader (r2 = 0.79) in tree crowns affected by the fungal pathogen Sphaeropsis sapinea, which produces both needle necrosis and chlorosis. Results for stands associated with defoliation and chlorosis through infestation by the aphid Essigella californica were lower with an r2 = 0.33 for crown transparency and r2 = 0.31 for proportion of crown affected. Similar analysis of data from a nitrogen deficient site produced an outcome somewhat in between the other two damaging agents. Overall the sunlit canopy image fraction has been the most important variable used in the modelling of forest condition for all damaging agents. 相似文献
124.
HDF 5格式特点及其对遥感数据格式标准化的几点启示 总被引:3,自引:0,他引:3
阐述了HDF 5数据格式的特点及其对遥感数据标准化的启示和借鉴作用。HDF 5格式层次式的逻辑结构、B树的物理存储方式,面向对象的特性、数据类型的广泛支持、自我描述以及内容与表达的分离等特点,使得它在记录和存储科学数据时具有强大的优势。遥感数据标准化如何设计一种结构简单且扩展性很好,同时支持不同平台的标准格式,可以从HDF 5的实现方法上得到借鉴。 相似文献
125.
A Bayesian method for linear, inequality-constrained adjustment and its application to GPS positioning 总被引:7,自引:0,他引:7
One of the typical approaches to linear, inequality-constrained adjustment (LICA) is to solve a least-squares (LS) problem subject to the linear inequality constraints. The main disadvantage of this approach is that the statistical properties of the estimate are not easily determined and thus no general conclusions about the superiority of the estimate can be made. A new approach to solving the LICA problem is proposed. The linear inequality constraints are converted into prior information on the parameters with a uniform distribution, and consequently the LICA problem is reformulated into a Bayesian estimation problem. It is shown that the LS estimate of the LICA problem is identical to the Bayesian estimate based on the mode of the posterior distribution. Finally, the Bayesian method is applied to GPS positioning. Results for four field tests show that, when height information is used, the GPS phase ambiguity resolution can be improved significantly and the new approach is feasible. 相似文献
126.
C. Kotsakis 《Journal of Geodesy》2005,79(6-7):341-350
The objective of this paper is the comparison of various types of estimators that can be used in linear models with uniformly biased data. This particular case refers to adjustment problems where the available measurements are affected by a common, unknown and uniform offset. The classic least-squares (LS) unbiased estimators for this type of models are reviewed in detail, and some additional remarks on their properties and performance are given. Furthermore, a family of biased estimators for linear models with uniformly biased data is introduced, which has the potential to provide better performance (in terms of mean squared estimation error) than the ordinary LS unbiased solutions. A number of different regularization viewpoints that can be equivalently associated with these biased estimators are presented, along with a discussion on various selection strategies that can be employed for the choice of the regularization parameter that enters into the biased estimation algorithm. 相似文献
127.
Effects of spatially variable ground motions on the seismic response of a skewed, multi-span, RC highway bridge 总被引:4,自引:0,他引:4
This paper presents a study of the influence of spatially variable ground motions on the longitudinal seismic response of a short, three-span, 30-degree skewed, reinforced concrete highway bridge. Linear and nonlinear finite element models are created for the bridge and linear elastic and nonlinear inelastic time history analyses conducted. Three different types of illustrative excitations are considered: The first utilizes spatially variable ground motions incorporating the effects of variable soil conditions, loss of coherency and wave passage as input motions at the structures' supports. The time history with the smallest peak displacement and the one with the largest peak displacement from the spatially variable ones are then used as uniform input motions at all bridge supports. The comparative analysis of the bridge model shows that the uniform ground motion input with the largest peak displacement cannot provide conservative seismic demands for all structural components—in a number of cases it results in lower response than that predicted by spatially variable motions. The present results indicate that there is difficulty in establishing uniform input motions that would have the same effect on the response of bridge models as spatially variable ones. Consequently, spatially variable input motions need to be applied as excitations at the bridge supports. 相似文献
128.
Tsutsumi S Yamaguchi Y Nishida I Akiyama K Zakaria MP Takada H 《Marine pollution bulletin》2002,45(1-12):325-331
Alkylbenzenes, molecular markers of sewage, were measured in 34 green mussels collected from India, Indonesia, Malaysia, Thailand, Cambodia, Vietnam, and the Philippines together with blue mussels collected from Tokyo Bay, Japan. Linear alkylbenzene (LAB) concentrations in South and South East Asian countries ranged from 10 to 1640 ng-∑LAB/g-dry tissue. In some populous cities, LAB concentrations were similar or higher than those found in northern Tokyo Bay which is heavily impacted by sewage effluents. I/E ratios (a ratio of internal to external isomers of LABs) in the South and South East Asian countries (1–3) were much lower than those in Tokyo Bay (3–8), indicating sewage discharged in the coastal zone is poorly treated (e.g., raw sewage and/or primary effluents). Alkylbenzenes with branched alkyl chains, tetrapropylene-based alkylbenzenes, were also detected in mussels from Indonesia and Philippines. This “tell-tale” sign indicates that poorly degradable detergents are still in use in this area, although they have long been phased-out in many industrialized countries. 相似文献
129.
本文利用彩红外航片和野外调查等方法,对三峡大坝坝区的线性构造和断裂系统进行了解译,对断裂构造特征进行了解析,从中得出以下结论:坝区主要存在四组方向的断裂,即NNW向、SN-NNE向、NW-NWW向以及NE-NEE向断裂组,其中NNW向断裂最为发育,NE-NEE向断裂组次之。SN-NNE向断裂组稍弱,NW-NWW向断裂发育最弱。通过数理统计的方法,对网格单元内线性构造的长度、条数、断裂交汇点数进行了统计,分析总结了该区断裂分布之规律及其对坝区岩体质量和坝基稳定性的影响。此外,文中还利用矿物流体包裹体特征,对断裂形成时的温度(T)、压力(P)等物理环境和变形史进行了探讨。 相似文献
130.
详细推导了加权线性回归诊断中hu的统计分布,针对G-M模型与线性回归模型的差异,指出测量数据处理中,使用的统计量hu的不合理性,给出了适于测量数据诊断的公式,并以数字实例加以分析和说明。 相似文献