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71.
本文综合探究了日平均气温、24h变温和气温日较差变化对缺血性心脑血管疾病发病人数的影响,采用分布滞后非线性模型(DLNM)与广义相加模型(GAM),分别探析了2015—2016年安徽省阜南县和贵州省锦屏县日平均气温、24h变温和气温日较差与缺血性心脑血管住院病人数的暴露—反应关系。结果表明:气温日较差大于15℃缺血性心脑血管疾病相对风险剧烈升高,并呈现明显的即时效应,且其相对风险随滞后日增加和气温日较差增加达到叠加效应的峰值。当24h内气温下降7℃以上,缺血性心脑血管疾病相对风险开始明显上升,下降10℃以上呈现显著的即时效应。统计分析发现,两县在春季达到上述阈值概率最高,因此缺血性心脑血管疾病住院人数也在春季达到峰值,特别是雨水至清明节气时段为两县住院人数共同最高峰时段;值得注意的是,地处西部的锦屏县夏季缺血性心脑血管疾病发病人数也较多。此外,降温过程与节气转换也是导致两县缺血性心脑血管疾病住院人数阶段性增多的主要天气与气候因素。 相似文献
72.
为研究气象要素对成人哮喘住院人数的影响,利用2013年1月1日至2016年12月31日石家庄市成人哮喘医保住院资料及气象、环境观测站数据,采用广义相加模型(GAM),在控制了时间趋势、节假日效应、空气污染等混杂因素后,分析气象要素与成人哮喘住院人数的暴露—反应关系。结果表明:各气象要素对成人哮喘住院人数的影响差异明显,日均气温(T)、日最高气温(Tmax)、日最低气温(Tmin)每上升1℃,成人哮喘住院风险分别减少0.7%、0.6%、0.7%;日均气压(P)每上升1 hPa,成人哮喘住院风险增加0.6%;日均风速(Ws)每增大1 m·s-1,成人哮喘住院风险减少5.2%;当相对湿度RH<24%时,相对湿度每增加1%,成人哮喘住院风险减少3.4%;当RH≥92%时,相对湿度每增加1%,成人哮喘住院风险增加12.5%;气温、气压、风速对成人哮喘住院人数的的影响均在当天或滞后1天(lag0—1)效应最大;根据各气象要素影响特点,可为健康气象预报服务及公众防御提供依据。 相似文献
73.
This paper proposes a saturated tracking controller for underactuated autonomous marine surface vehicles with limited torque. First, a second-order open-loop error dynamic model is developed in the actuated degrees of freedom to simplify the design procedure. Then, a saturated tracking controller is designed by utilizing generalized saturation functions to reduce the risk of actuator saturation. This, in turn, improves the transient performance of the control system. A multi-layer neural network and adaptive robust control techniques are also employed to preserve the controller robustness against unmodeled dynamics and environmental disturbances induced by waves and ocean currents. A Lyapunov stability analysis shows that all signals of the closed-loop system are bounded and tracking errors are semi-globally uniformly ultimately bounded. Finally, simulation results are provided for a hovercraft vehicle to illustrate the effectiveness of the proposed controller as a qualified candidate for real implementations in offshore applications. 相似文献
74.
本文在系统介绍遥感图像检索中边缘特征描述方法的基础上,将边缘特征归纳为边缘图和边缘方向两类特征。通过对遥感目标图像库和纹理图像库上所做实验的分析,揭示了不同算法的特性,并指出综合两类特征可进一步提高算法的检索性能。 相似文献
75.
A newly-discovered GPD-GEV relationship together with comparing their models of extreme precipitation in summer 总被引:3,自引:0,他引:3
It has been theoretically proven that at a high threshold an approximate expression for a quantile of GEV (Generalized Extreme Values) distribution can be derived from GPD (Generalized Pareto Distribution). Afterwards, a quantile of extreme rainfall events in a certain return period is found using L-moment estimation and extreme rainfall events simulated by GPD and GEV, with all aspects of their results compared. Numerical simulations show that POT (Peaks Over Threshold)-based GPD is advantageous in its simple operation and subjected to practically no effect of the sample size of the primitive series, producing steady high-precision fittings in the whole field of values (including the high-end heavy tailed). In comparison, BM (Block Maximum)-based GEV is limited, to some extent, to the probability and quantile simulation, thereby showing that GPD is an extension of GEV, the former being of greater utility and higher significance to climate research compared to the latter. 相似文献
76.
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78.
For linear forcing problems, a method is developed to provide a set of forcing modes which form a complete orthonormal basis for the finite-time response to steady forcing in the energy inner product space. The forcing modes are found by calculating eigenvectors of a positive definite and symmetric matrix determined from given equations of motion. The amplitude of responses to forcing modes is given in terms of the associated eigenvalues. This method is used in a nondivergent barotropic model linearized about the 300 hPa zonally-varying climatological flow both for northern summertime and wintertime. The results show that the amplitude of response varies considerably with different forcing modes. Only a few of forcing modes associated with the leading eigenvalues, called efficient forcing mode, can excite significant response. The efficient forcing modes possess highly localized spatial structure with wavetrain appearance. Most of the efficient forcings are located to the south of regions of the jet cor 相似文献
79.
80.
Spatial-temporal rainfall modelling for flood risk estimation 总被引:4,自引:6,他引:4
H. S. Wheater R. E. Chandler C. J. Onof V. S. Isham E. Bellone C. Yang D. Lekkas G. Lourmas M.-L. Segond 《Stochastic Environmental Research and Risk Assessment (SERRA)》2005,19(6):403-416
Some recent developments in the stochastic modelling of single site and spatial rainfall are summarised. Alternative single
site models based on Poisson cluster processes are introduced, fitting methods are discussed, and performance is compared
for representative UK hourly data. The representation of sub-hourly rainfall is discussed, and results from a temporal disaggregation
scheme are presented. Extension of the Poisson process methods to spatial-temporal rainfall, using radar data, is reported.
Current methods assume spatial and temporal stationarity; work in progress seeks to relax these restrictions. Unlike radar
data, long sequences of daily raingauge data are commonly available, and the use of generalized linear models (GLMs) (which
can represent both temporal and spatial non-stationarity) to represent the spatial structure of daily rainfall based on raingauge
data is illustrated for a network in the North of England. For flood simulation, disaggregation of daily rainfall is required.
A relatively simple methodology is described, in which a single site Poisson process model provides hourly sequences, conditioned
on the observed or GLM-simulated daily data. As a first step, complete spatial dependence is assumed. Results from the River
Lee catchment, near London, are promising. A relatively comprehensive set of methodologies is thus provided for hydrological
application. 相似文献