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981.
基于GIS的复杂地形洪水淹没区计算方法 总被引:64,自引:0,他引:64
利用GIS技术计算洪水淹没区范围一直是灾害评估研究中的一个热点问题。通过给出两种情形下基于种子蔓延算法的淹没区计算方法,即有源 淹没和无源淹没。淹没区计算精度主要取决于空间数据精度的优劣;种子蔓延算法及探测分辨率决定了整个模型的效率。文中最后给出了该模型在“水利综合管理信息系统”中得到验证和实现的实例。 相似文献
982.
Chen Hao 《地理学报(英文版)》2001,11(1):71-79
From a long-term point of view, the balance between erosion and sediment yield in a drainage system can basically realize,
i.e., the delivery ratio can be close to 1. However, substantial variations among individual rainfall events or between annual
delivery ratio exist, causing frequent sediment retaining or re-erosion and re-delivery of the retained sediments in a short
period of time. Thus the delivery ratio will be < 1 or > 1. The sediment delivery ratio is closely related to the spatial
distribution of rainfall and magnitude of rise and fall of peak flood and that of runoff depth in the drainage system. Delivery
ratio of single event in a drainage system and changes of delivery capacity of silt-laden runoff in various classes of gullies
can be expressed by transformation mechanism of shear force of a single rainstorm event with flood resulting from increase
and decrease of peak flood per unit area. 相似文献
983.
According to classification system of wetland in Ramsar Convention, salt marsh belongs to inland salt lake formed by regional hydrogeologic and climatic conditions[1]. In western Songnen Plain, the most distinct characteristic of water environment in salt marsh wetlands is that many water bodies have high salt contents and pH values, so salt marsh wetlands are categorized as a special natural synthesis[2]. 1 Natural environment in western Songnen PlainThe Songnen Plain lies to the east of … 相似文献
984.
S. N. Rajaguru Avijit Gupta V. S. Kale Sheila Mishra R. K. Ganjoo L. L. Ely Yahouda Enzel V. R. Baker 《地球表面变化过程与地形》1995,20(5):407-421
The 1300 km long Narmada River flows along a structural lineament, alternating between constricting rocky gorges and rapids, and meandering wide alluvial reaches. Channel forms and processes were studied in a 120 km long section of an alluvial reach. Channel size, shape and bedforms in the Narmada River are related to very large floods which have occurred three times in this century. During such floods the entire 400 m wide channel is utilized and 10–15 m high cliffs on both sides operate as riverbanks. Normally, even the high flows of the south-western monsoon are insufficient to fill the whole channel, and hence their effects are limited to building of discontinuous floodplains between the cliffs and modifying bedforms and bars. A channel-in-channel topography is thus created. The very large floods are also responsible for erosion of the rocky stretches and building of point bars. The river meanders, but its movement is restricted because of (1) rocky gorges and scablands operating as anchor points at intervals, and (2) the presence of high alluvial cliffs which are topped on extremely rare occasions. In spite of being located in a tectonically active zone in a monsoon setting, it is the exceptional high-magnitude floods at irregular intervals which control the form and behaviour of the Narmada River. 相似文献
985.
Geraldene Wharton 《地球表面变化过程与地形》1995,20(7):649-660
All river engineering schemes require flood discharge estimates as part of the design and appraisal process. Unfortunately, continuous measurement of flood discharges is limited to those river sites with instrumented gauging stations, which constitute only a small proportion of channel reaches where information is required. Therefore, considerable research effort has been devoted to the development of reliable indirect techniques of flood discharge estimation. Research on the interrelationship of stream channel geometry and river discharge has provided the basis for an indirect method of flood estimation – the channel-geometry method – which employs river channel dimensions alone to estimate discharge characteristics at ungauged river sites. Channel-geometry equations are developed empirically by relating streamflow data from gauging stations and channel dimensions measured from natural river reaches in the vicinity of the gauge, and take the form of power function relations. Once regional channel-geometry equations have been defined, a channel width or channel capacity measurement is the only variable needed to estimate the flood flow characteristics at a specified river site. The method is useful as an alternative to traditional catchment-based approaches or as a rapid reconnaissance technique. In addition to the application for flood discharge prediction, channel-geometry equations could prove helpful in the management of river channels, first, by providing a basis for assessing local deviations in the channel form–discharge relation, deviations which could be employed as indicators of the sensitivity of particular stretches of river channel to change, and secondly, in the computation of natural channel dimensions for use in river channel design and river restoration. 相似文献
986.
J. R. Stedinger L. -H. Lu 《Stochastic Environmental Research and Risk Assessment (SERRA)》1995,9(1):49-75
Our results illustrate the performance of at-site and regional GEV/PWM flood quantile estimators in regions with different coefficients of variation, degrees of regional heterogeneity, record lengths, and number of sites. Analytic approximations of bias and variance are employed. For realistic GEV distributions and short records, the index-flood quantile estimator performs better than a 2-parameter GEV/PWM quantile estimator with a regional shape parameter, or a 3-parameter at-site GEV/PWM quantile estimator, in both humid and especially in arid regions, as long as the degree of regional heterogeneity is moderate. As regional heterogeneity or record lengths increases, 2-parameter estimators quickly dominate. Flood frequency models that assign probabilities larger than 2% to negative flows are unrealistic; experiments employing such distributions provide questionable results. This appraisal generally demonstrates the value of regionalizing estimators of the shape of a flood distribution, and sometimes the coefficient of variation. 相似文献
987.
满城冰雹云类型与特征分析 总被引:1,自引:0,他引:1
根据探空、雷达观测以及降雹资料,对河北满城地区1986-1990年64次降雹天气过程进行了分析,对冰雹云类型作了分类研究。结果表明,该地区冰雹云分为5种类型:强单体、点源雹云、传播雹云、多单体及弱单体雹云。5年的统计资料得出,满城地区以多单体、弱单体雹云为最多,强单体雹云和传播雹云是该地区主要成灾雹云。 相似文献
988.
塔里木河1994年大洪水及其相关问题分析 总被引:4,自引:1,他引:4
塔里木河阿拉尔站1994年7月发生了有记载以来的第二位最大洪峰流量,时段最大洪量。超过了以往的记录,在分析塔里木河洪水成因的基础上,对1994年洪水的形成,特性,沿程耗损作了剖析;回顾了1956年以来干流上,中,下游段耗用水比的变迁,并对其后果进行了分析。 相似文献
989.
990.
淮河中游行蓄洪区种植制度调整研究 总被引:1,自引:0,他引:1
行蓄洪区的行洪与蓄洪,影响了区内农业的发展,造成粮食产量长期徘徊,导致贫困的加剧。本文分析了区内自然环境,社会经济状况,提出一麦一稻之构想,通过示范研究获得成功,证实了其可行性。 相似文献