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991.
商丘市紫外线辐射与气象因子的关系 总被引:1,自引:0,他引:1
利用2003年4月至2006年6月商丘太阳紫外线辐射强度资料及气象资料,分析了商丘市紫外线辐射的月、日变化规律及气象因子对紫外线辐射的影响。结果表明:商丘紫外线辐射月际分布是,年初、年底辐射量小,3~9月辐射量大,最大辐射指数为11.4;紫外线辐射的日变化规律显著,基本上遵循正态分布,呈抛物线型变化,早晚辐射量小、中午前后紫外线辐射量大;紫外线辐射强度与总云量呈反相关,与能见度呈正相关,与气温呈正相关,与相对湿度呈反相关。 相似文献
992.
993.
华北和西北区干湿年间水汽场及东亚夏季风的对比分析 总被引:30,自引:31,他引:30
为了更好地理解华北及西北地区的夏季降水气候,我们利用NCEP的再分析格点资料等,对华北和西北两区干,湿年(月)的水汽场及夏季风状况作了对比分析,主要结论是:(1)近50年来华北和西北区东部明显干旱化,这可能与同期内东亚夏季风强度趋弱,大气可降水量逐渐减少有关;(2)两地区干,湿年(月)间气柱可降水量差别明显;(3)两地区干,湿年(月)的夏季风,水汽输送通道的位置及强度,以及水汽通量的辐散辐合情况均不同;(4)高原与太平洋间的海陆温差指数及东亚夏季风指数(SMI)对表征东亚夏季风的季节变化及夏季风强度的年际变化有一定的能力,冬春季高原与太平洋间的海陆温差对其后东亚夏季风的强弱及西北和华北区的干湿状况有部分指示意义;作西北区夏季降水预报时要注意四川盆地的水汽场及广元-汉中一带,以及闽,台和两广的水汽输送状况。 相似文献
994.
995.
In active geodynamic areas, such as the Italian Southern Apennines, the specific structural conditions have a profound effect on both the superficial and deep gravitational evolution of slopes. Chain sectors commonly exhibit structural complexities due to the superimposition, in space and time, of diverse tectonic stress fields. In this paper, attention is focused on particular structural configurations, connected to the tectonic quaternary phases that have affected the Southern Apennines, constituting a peculiar type of lateral spread gravitational deformations – which have not been previously described.The study area is characterized by regional roughly east-verging overthrusts (Holigo–Miocene). Superimposed on these, is a system of transpressive thrust ramps (Quaternary), connected to the activity of strike-slip faults. The latest tectonic phase, still active, has been characterized by an extensional stress field, which has produced differentiated uplifts along normal faults. All these factors have encouraged an intense and widespread processes of erosion, the creation of considerable relief energy and the development of both superficial and deep gravitational phenomena.It has been ascertained that the late extensional phases favoured gravitational reactivations (with normal movements) along those most recent thrust ramps whose attitude was kinematically consistent with the main extension direction of the stress field. Such reactivations were accommodated by antithetic neo-formational structures – these are also characterized by normal kinematics. Overall, such mechanisms lead to the individuation of wedge-shaped rock portions delimited by the normally reactivated thrust ramps, on one side, and by the antithetic structures, on the other.Structural wedges represent a particular type of lateral spread phenomena. On the basis of their orientation with respect to the orography, three typical situations have been defined: (1) wedge perpendicular to the ridge; (2) wedge parallel to the ridge; (3) wedge oblique to the ridge.In this paper three Calabrian case studies, exemplifying the above-mentioned situations, are described. The same framework can be applied to sectors of chain with an analogous structural setting, for a better understanding of the kinematic features of observed gravitational phenomena. 相似文献
996.
系统地收集了国内已公开发表的东北地区热流数据81个,并对其进行了初步统计分析。这些数据的地理分布还很不均匀,热流值变化范围为30-94mW/m^2,多种统计平均方法得到的结果表明,东北大陆地区平均热流值变化范围为60-63mW/m62。然后,根据上述统计结果初步讨论了我国东北地区地热场分布的基本特征和概况,并阐述了这项研究的地质和地球物理意义。 相似文献
997.
本文通过可可西里-金沙江地震带震级频度关系的确定及其参数b值与a值、值(地震年平均发生率)和Mmax(最大震级a/b)之间的相关性分析, 以说明地震危险性概率分析中的地震活动性参数值与b值也应有某种相关性。当地震带未来一定时期内地震活动震级上限Muz和b值被确定后, 未来地震活动的值的取值范围似将受到一定的限制。如假设可可西里-金沙江地震带的Muz为8级, b值为0.73后, 相应的值若取13.943, 可能偏小。 相似文献
998.
The performance‐based philosophy has been accepted as a more reasonable design concept for engineering structures. For this purpose, capacity evaluation and demand prediction procedures for civil engineering structures under earthquake excitations are of great significance. This work presents a displacement‐based seismic performance verification procedure including capacity and seismic demand predictions for steel arch bridges and investigates its applicability. Pushover analyses is employed as a basis in this method to investigate the structure's behaviors. A failure criterion for steel members accounting for the effect of local buckling is involved and an equivalent single‐degree‐of‐freedom (ESDOF) system with a simplified bilinear hysteretic model formulated using pushover analyses results is introduced to estimate the displacement capacity and maximum demand of steel arch bridges under major earthquakes. To check the accuracy of the proposed method, seismic capacities and demands from multi‐degree‐of‐freedom (MDOF) time‐history analyses with Level‐II design earthquake record inputs modeling major earthquakes are used as benchmarks for comparison. By a case study, it is clarified that the proposed prediction procedure can give accurate estimations of displacement capacities and demands of the steel arch bridge in the transverse direction, while insufficient for the longitudinal direction, which confirms the conclusion drawn in other structure types about the applicability of pushover analyses. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
999.
旅游客流对比分析与驱动力研究--以湖北省为例 总被引:2,自引:0,他引:2
旅游客流作为旅游产业链的基础,其重要性日益突出,因此旅游客流驱动模式研究已成为旅游界研究的一个新热点。本文以湖北省为例,通过对湖北旅游客流统计资料的科学分析,总结出客流系统的规律性特征并归纳出其客流驱动模式为资源驱动型,并分析了资源驱动型客流模式存在的问题,在此基础上探讨与构建一种系统性的客流驱动优化模式——客流综合驱动模式,以促进旅游产业良性循环。 相似文献
1000.