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51.
解放战争时期,由于战争、自然灾害、战勤等原因,解放区的难民、灾民等弱势群体问题十分严重。中国共产党在领导人民进行解放战争的同时,通过采取有计划地安置弱势群体、发放紧急赈济、防疫治病、对弱势群体进行心理干预、大力发展农业副业生产等措施,积极进行弱势群体的社会救助工作并取得了显著的成效。解放战争时期解放区的社会救助实践对当今的社会救助事业发展以及和谐社会的构建起到了很好的借鉴作用。  相似文献   
52.
To better understand the dust storm (hereafter DS) inducing circulation in the China–Mongolia (CM) DS activity area, the spring mean circulation features and differences on lower levels in three subregions of the CM DS area for the major- and minor-DS years have, as a whole (not partly), been analyzed, utilizing the National Centers for Environmental Prediction and the National Center for Atmospheric Research (NCEP/NCAR) reanalyzed gridded data, the observed DS frequency data in the CM area, and the composite analysis method. The main conclusions are as follows: (1) Judging from the differences in the DS-inducing systems, dust origins, paths of invading cold air, and main DS-strike areas, the whole CM DS area is roughly divided into the three subregions: the East-, Middle- and West-CM subregions (in this paper, referred to as E-, M-, and W-CM). (2) In major DSs during spring over the E-CM, the middle- and lower-level troughs or cyclones over the Japan Sea and northeastern China (NEC) dominate. The invading cold air along the northeastern (NE) or north by east (NE) path often causes the DS in the E-CM region. But nearly the opposite is true in minor DS during spring in E-CM. (3) In the major DS during spring over the M-CM region, the Mongolian troughs or cyclones are the main DS-inducing systems. The strong invading cold air along the northwestern (NW)- or north by west (Nw) path causes the DSs in the M-CM region. (4) In the major DSs during spring over the W-CM region, the South Xinjiang heat lows prevail, the intruding cold air has a western path, and creates the DSs in South Xinjiang. (5) In the past 50 years, the DSs over the M-CM region have had the most severe impact on the preceding three subregions of the CM DS area. Overall, DS activities over all of three regions of the CM area decreased in the past (particularly, over M- and W-CM regions since the mid-1980s. But there existed a short and sudden increasing in E-CM in the years 2000–2002. (6) It is circulation changes and desertification evolutions that cause the yearly and decadal changes of DS in CM area, especially the former. With the backdrop of global warming in the future, perhaps the decreased DS activities over M- and W-CM will persist for some time again, and special attention should be paid to ones over E-CM or to the individual DS events over M- and W-CM.  相似文献   
53.
The master plans for the management of river basins have been elaborated. The territory of Bulgaria is divided into four main hydrological zones - Danube, Black Sea, East and West Mediterranean hydrological zones. The rivers from Danube zone discharged directly to the Danube river, the North boundary of the country. All rivers from the eastern part of Bulgaria discharged directly to the Black Sea. The rivers from East and West Mediterranean hydrological zones discharged to Mediterranean Sea after flowing trough Greece and/or Turkey. The main river basins in Bulgaria were subjects to the evaluation of master plans.During the elaboration of the master plans the following elements have been investigated:
Demographical characteristics of the stakeholders in the river basin.
Economical overview of the stakeholders.
Estimation of surface water availabilities and resources; Water quantity.
Groundwater overview and estimation of available groundwater resources.
Water quality of surface and ground water; sediment load.
Estimation of water use for domestic, irrational, agricultural and industrial water supply.
Ecosystems in the river basin; Tundja river basin ecosystems.
Master Plans elaboration for 2010.
Water balance calculations for 1998 and 2010.
The aim of this paper is to present an overview of Tundja river basin management. Tundja is one of the biggest tributaries of Mariza river and it is join it in the territory of Turkey. The basin belongs to the East Mediterranean hydrological zone. The hydrological investigations and estimations of natural river flow along the main river body and it’s tributaries will be discussed in details. The calculations concern 1961-2004 study period. Long-term assessment has been performed. The characteristics of the monthly, annual, minimum and maximum river discharges have been obtained.  相似文献   
54.
张超  胡志根 《水科学进展》2014,25(6):873-879
在考虑高堆石坝坝体中期临时挡水度汛不允许坝面过水条件下,综合考虑坝前洪水位与防洪度汛高程的随机性,构建高堆石坝工程中期度汛挡水风险数学模型.针对堆石坝施工系统的特点,考虑各月停工天数与日平均上升速度的随机性,建立了防洪度汛高程仿真计算模型.基于Monte-Carlo方法原理,耦合水文、水力和施工随机因素对风险模型进行求解,并研究了日均控制最低上升速度这一施工可控指标对风险率的影响.通过大渡河流域某大型工程实例分析表明,风险模型与计算方法可行、有效.  相似文献   
55.
两千年来中国自然与人文地理环境变迁及启示   总被引:1,自引:1,他引:1  
科学理解中国自然与人文地理环境变迁的历史逻辑、基本规律和发展趋势,有助于找准历史方位,确立国土空间开发保护格局优化方向,推进“美丽中国”建设与经济社会可持续发展。本文集成现有研究成果,梳理了两千年来中国自然与人文地理环境变迁过程,总结了主要要素的变迁特点,探讨了这些历史变迁对“美丽中国”建设的启示。研究表明,两千年来中国自然地理环境变化主要表现为气候的多尺度准周期波动、黄土高原破碎化、北方地区沙漠化土地扩张、河口三角洲海岸在泥沙沉积作用下逐步外移、黄河和长江中下游湖泊萎缩、森林和温带草原面积下降。人文地理环境变迁突出表现在人口增长和格局变化、经济中心向东南迁移、耕地向外围扩张、交通网络由道路网和运河网向立体化综合交通网转变。依据上述变化的历史逻辑,未来基本自然地理格局和地理界线仍将长期存在,长江和黄河中下游星罗棋布的湖泊水系已难再现,南粮北运成为历史,但森林覆盖率仍有较大提升空间,交通网络建设仍需进一步推进,同时还要加强沿海城市应对气候变化威胁的防控体系建设。  相似文献   
56.
陆表海碳酸盐岩台地沉积期微地貌起伏差异小,难于确定。分析了沉积期微地貌控制着颗粒滩储层的发育及分布,因此,可通过对颗粒滩储层的研究,反演微地貌起伏。按此原理,建议具体研究步骤为:颗粒岩沉积为主体的等时地质体选取、储层成因确定、暴露时间确定、沉积期地貌恢复,以及成果检验应用。以四川盆地磨溪气田嘉陵江组嘉二2亚段A层为例,利用丰富的钻孔取心资料进行了实例研究,取得良好效果,表明该方法值得推广应用,尤其适用于钻探程度高、资料老、缺乏三孔隙度测井系列的盆地老区,这对于储层预测和新层挖潜具有重要参考意义。  相似文献   
57.
Based on the daily maximum temperature data covering the period 1961-2005, temporal and spatial characteristics and their changing in mean annual and monthly high temperature days(HTDs)and the mean daily maximum temperature(MDMT)during annual and monthly HTDs in East China were studied.The results show that the mean annual HTDs were 15.1 and the MDMT during annual HTDs was 36.3℃in the past 45 years.Both the mean annual HTDs and the MDMT during annual HTDs were negative anomaly in the1980s and positive anomaly in the other periods of time,oscillating with a cycle of about 12-15 years.The mean annual HTDs were more in the southern part,but less in the northern part of East China.The MDMT during annual HTDs was higher in Zhejiang,Anhui and Jiangxi provinces in the central and western parts of East China.The high temperature process(HTP) was more in the southwestern part,but less in northeastern part of East China.Both the HTDs and the numbers of HTP were at most in July,and the MDMT during monthly HTDs was also the highest in July.In the first 5 years of the 21st century,the mean annual HTDs and the MDMT during annual HTDs increased at most of the stations,both the mean monthly HTDs and the MDMT during monthly HTDs were positive anomalies from April to October,the number of each type of HTP generally was at most and the MDMT in each type of HTP was also the highest.  相似文献   
58.
Lake water level regimes are influenced by climate, hydrology and land use. Intensive land use has led to a decline in lake levels in many regions, with direct impacts on lake hydrology, ecology and ecosystem services. This study examined the role of climate and river flow regime in controlling lake regimes using three different lakes with different hydraulic characteristics (volume-inflow ratio, CIR). The regime changes in the lakes were determined for five different river inflows and five different climate patterns (hot-arid, tropical, moderate, cold-arid, cold-wet), giving 75 different combinations of governing factors in lake hydrology. The input data were scaled to unify them for lake comparisons. By considering the historical lake volume fluctuations, the duration (number of months) of lake volume in different ‘wetness’ regimes from ‘dry’ to ‘wet’ was used to develop a new index for lake regime characterisation, ‘Degree of Lake Wetness’ (DLW). DLW is presented as two indices: DLW1, providing a measure of lake filling percentage based on observed values and lake geometry, and DLW2, providing an index for lake regimes based on historical fluctuation patterns. These indices were used to classify lake types based on their historical time series for variable climate and river inflow. The lake response time to changes in hydrology or climate was evaluated. Both DLW1 and DLW2 were sensitive to climate and hydrological changes. The results showed that lake level in high CIR systems depends on climate, whereas in systems with low CIR it depends more on river regime.  相似文献   
59.
Based on the daily precipitation data of more than 2 000 meteorological stations from 1960 to 2017 and the tropical cyclone (TC) best-track data of the China Meteorological Administration, the TC precipitation was identified by the Objective Synoptic Analysis Technique (OSAT). The research shows that the TC precipitation in China has a significant downward trend, which is slower than that of the research results 12 years ago. The TC precipitation in the peaking season (July to Sepember) accounted for 78.5% of the total TC precipitation. Both TC precipitation in peaking season and other months showed a significant downward trend. The TC precipitation climate trend is mainly characterized by reduction in spatial distribution, and shows obvious regional differences. From south to north, there is a distribution of “decreasing-increasing-decreasing”, and the decreasing trend centers are located in Guangdong and Hainan. According to the maximum intensity in the TC influence period, we classified TCs into three levels (weak TCs, medium intensity TCs and strong TCs) and studied the variations of TC precipitation in different intensities. The results show that the strong TC precipitation shows a significant decrease trend, which mainly determines the influence range and trend of TC total precipitation. Further analysis found that the frequency of affecting TC showed a significant reduction trend during the time period of 1960-2017 and an abrupt shift occurred in 1995. A comparative study of the two periods before and after 1995 showed that compared with the previous period (1960-1994), the frequency of TCs in the latter period (1995-2017) showed a significant decreasing trend in the south of 20°N. The maximum decreasing center was located in the northern part of the South China Sea, and this feature was mainly affected by the strong TC. It was decided that this trend of strong TC led to a decrease trend in the number of precipitation days in South China, especially in Guangdong and Hainan, which led to a decrease trend in TC precipitation.  相似文献   
60.
改进密云水库汛期调度方案的途径   总被引:2,自引:0,他引:2  
廖松 《水文》1996,(1):10-15
密云水库是华北最大的水库,确定密云水库汛期调度方案的原则是20年前制定的,按现代观点看来,其设计防洪库容过大,因而降低了密云水库的蓄水能力。在深入分析潮白河水文特征的基础上,并考虑新建3个水库对下游汉域洪峰流量的影响,提出了几个新的方案,每一个新的方案,每一个建议的方案都能显著提高密云水库的效益。  相似文献   
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