首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   725篇
  免费   274篇
  国内免费   440篇
测绘学   10篇
大气科学   703篇
地球物理   184篇
地质学   143篇
海洋学   239篇
天文学   11篇
综合类   62篇
自然地理   87篇
  2024年   3篇
  2023年   11篇
  2022年   30篇
  2021年   34篇
  2020年   39篇
  2019年   41篇
  2018年   55篇
  2017年   59篇
  2016年   51篇
  2015年   54篇
  2014年   53篇
  2013年   87篇
  2012年   62篇
  2011年   44篇
  2010年   47篇
  2009年   59篇
  2008年   68篇
  2007年   64篇
  2006年   51篇
  2005年   72篇
  2004年   41篇
  2003年   58篇
  2002年   53篇
  2001年   43篇
  2000年   34篇
  1999年   33篇
  1998年   47篇
  1997年   19篇
  1996年   17篇
  1995年   15篇
  1994年   21篇
  1993年   23篇
  1992年   20篇
  1991年   11篇
  1990年   6篇
  1989年   5篇
  1988年   1篇
  1987年   1篇
  1986年   2篇
  1984年   2篇
  1983年   1篇
  1977年   1篇
  1954年   1篇
排序方式: 共有1439条查询结果,搜索用时 15 毫秒
91.
Obvious results have been achieved in the forecast of typhoon track that is improved with a consensus procedure Forecast experiments were conducted with the analogue model (TSF) and the Markov type model (MTSF)that are widely used and the results show that there has been significant increase in the capability of forecasting with the improvement by the consensus procedure.  相似文献   
92.
分析1950年以来中等强度以上的ElNiño和LaNina当年和次年夏季(7月)低纬度风场和500hPa高度距平场,发现有不同的特征。其中中-西太平洋近赤道地区850、200hPa上风场异常变化十分明显,这种异常变化与南北半球大气相互作用有密切关系。在500hPa高度距平场上,北半球中、高和低纬地区表现出不同的正、负距平分布型式。上述特点对气候短期预测有一定参考意义。  相似文献   
93.
2000—2019年秦岭南北实际蒸散发时空变化特征   总被引:1,自引:0,他引:1  
基于遥感数据全面认识复杂地形单元实际蒸散发时空规律,对区域可持续水资源管理具有重要的意义。论文基于MODIS实际蒸散发(ET)数据,对2000—2019年秦岭南北ET时空变化特征进行分析,探究不同分区ET对植被变化的响应关系,进而识别ET趋势和年代变化的高相关海气环流因素。结果表明:① 在变化趋势上,以1000 m等高线为界,即秦岭地区北亚热带和山地暖温带的分界线,低海拔河谷地带为ET显著增加区,山地高海拔地区为ET下降区;② 除城市、乡镇周边地区,研究期间秦岭南北下垫面相对稳定,转为生态用地的活跃区主要分布在山地1000 m过渡带,其是ET与NDVI变化显著相关区,而1000 m以上高海拔地区两者相关性较低;③ ENSO、青藏高原北部气压异常,与秦岭山地、汉江谷地ET的趋势变化和年代波动显著相关,而西太平洋副热带高压与ET的趋势显著相关,与年代波动特征相关较弱。即发生中部型厄尔尼诺事件时,西太平洋副热带高压偏强,对流层低层形成异常反气旋,导致中国东部雨带北移,秦岭山地和汉江谷地降水偏少,气温偏高,ET往往偏大。研究结果启示:秦岭南北科学适应气候变化时,应关注秦岭山地、汉江谷地ET变化显著相关的环流信号;应深刻理解秦岭高海拔地区蒸散发下降趋势对区域水资源管理的影响。  相似文献   
94.
A methodology for the characterization of deep carbonate aquifers has been developed and applied to El Maestrazgo Jurassic aquifer in Castellón, Spain. Characterization of these aquifer formations, located at more than 300 m deep, consisted of a previous phase of compilation, analysis and synthesis of the existing information about the area, followed by a coordinated combination of different speciality studies: geology, stratigraphy, structural analysis, hydrogeology, hydrochemistry, geophysics and remote sensing. Geological studies included geological mapping, definition of stratigraphical units and facies and structural analysis. The aim of the hydrogeology study was to define aquifer formations, recharge area, aquifer points inventory and groundwater flow directions for the establishment of piezometric and water quality observation nets. Special techniques were applied, like thermal infrared aerial images and the evaluation of submarine groundwater discharge by means of natural radium isotopes. Hydrochemical techniques, including majority elements characterization and stable isotopes (18O, 2H and 3H) determination, allowed classifying hydrochemical facies and establishing a renewal pattern for water within the system. Geophysics was useful in determining the aquifer geometry, the features of the basement and the petrophysical characteristics of the geological formations. Preliminary results show an important tectonic complexity and the possibilities for groundwater uses in the area of study.  相似文献   
95.
The inverse relationship between the warm phase of the El Ni?o Southern Oscillation(ENSO) and the Indian Summer Monsoon Rainfall(ISMR) is well established. Yet, some El Ni?o events that occur in the early months of the year(boreal spring) transform into a neutral phase before the start of summer, whereas others begin in the boreal summer and persist in a positive phase throughout the summer monsoon season. This study investigates the distinct influences of an exhausted spring El Ni?o(springtime)...  相似文献   
96.
1 IntroductionThe El Ni’o atmospheric physics oscillation is anabnormal phenomenon involved in the tropical Pacificocean- atmosphere interactions. Studies on the El Ni(ophenomenon are very attractive (Lin et al., 2000; Linet al., 2001, 2002; Wang, 2001; Feng et al., 2001;Feng et al., 2002; Liu et al., 2002; Wei and Chen,2003; Xie et al., 2002; Zhu et al., 2002; Pu et al.,2003; Gu et al., 2004; Yu and Liu, 2004). Lin and Mo(2004), Mo and Lin (2004) and Mo et al. (2004) alsostudied a s…  相似文献   
97.
Identification of the distinctive circulation patterns of storminess on the Atlantic margin of Europe forms the main objective of this study; dealing with storm frequency, intensity and tracking. The climatology of the extratropical cyclones that affect this region has been examined for the period 1940–1998. Coastal meteorological data from Ireland to Spain have been linked to the cyclone history for the North Atlantic in the analysis of storm records for European coasts. The study examines the evolution in the occurrence of storms since the 1940s and also their relationship with the North Atlantic Oscillation (NAO). Results indicate a seasonal shift in the wind climate, with regionally more severe winters and calmer summers established. This pattern appears to be linked to a northward displacement in the main North Atlantic cyclone track.

An experiment with the ECHAM4 A-GCM at high resolution (T106) has also been used to model the effect of a greenhouse gases induced warming climate on the climatology of coastal storms in the region. The experiment consists of (1), a 30-year control time-slice representing present-day equivalent CO2 concentrations and (2), a 30-year perturbed period corresponding to a time when the radiative forcing has doubled in terms of equivalent CO2 concentrations. The boundary conditions have been obtained from an atmosphere-ocean coupled OA-GCM simulation at low horizontal resolution. An algorithm was developed to allow the identification of individual cyclone movements in selected coastal zones. For most of the northern part of the study region, covering Ireland and Scotland, results describe the establishment by ca. 2060 of a tendency for fewer but more intense storms.

The impacts of these changes in storminess for the vulnerability of European Atlantic coasts are considered. For low-lying, exposed and ‘soft’ sedimentary coasts, as in Ireland, these changes in storminess are likely to result in significant localised increases in coastal erosion.  相似文献   

98.
Anomalous change of the Antarctic sea ice and global sea level change   总被引:3,自引:0,他引:3  
AnomalouschangeoftheAntarcticseaiceandglobalsealevelchange¥XieSimei;ZouBing;WangYiandBaoChenglan(1.NationalMarineEnvironmentF...  相似文献   
99.
100.
This paper is part of a comprehensive review of the oceanography of the eastern tropical Pacific, the oceanic region centered on the eastern Pacific warm pool, but also including the equatorial cold tongue and equatorial current system, and summarizes what is known about oceanographic influences on seabirds and cetaceans there. The eastern tropical Pacific supports on the order of 50 species of seabirds and 30 species of cetaceans as regular residents; these include four endemic species, the world’s largest populations for several others, three endemic sub-species, and a multi-species community that is relatively unique to this ecosystem. Three of the meso-scale physical features of the region are particularly significant to seabirds and cetaceans: the Costa Rica Dome for blue whales and short-beaked common dolphins, the Equatorial Front for planktivorous seabirds, and the countercurrent thermocline ridge for flocking seabirds that associate with mixed-species schools of spotted and spinner dolphins and yellowfin tuna. A few qualitative studies of meso- to macro-scale distribution patterns have indicated that some seabirds and cetaceans have species-specific preferences for surface currents. More common are associations with distinct water masses; these relationships have been quantified for a number of species using several different analytical methods. The mechanisms underlying tropical species–habitat relationships are not well understood, in contrast to a number of higher-latitude systems. This may be due to the fact that physical variables have been used as proxies for prey abundance and distribution in species–habitat research in the eastern tropical Pacific.Though seasonal and interannual patterns tend to be complex, species–habitat relationships appear to remain relatively stable over time, and distribution patterns co-vary with patterns of preferred habitat for a number of species. The interactions between seasonal and interannual variation in oceanographic conditions with seasonal patterns in the biology of seabirds and cetaceans may account for some of the complexity in species–habitat relationship patterns.Little work has been done to investigate effects of El Niño-Southern Oscillation cycles on cetaceans, and results of the few studies focusing on oceanic seabirds are complex and not easy to interpret. Although much has been made of the detrimental effects of El Niño events on apex predators, more research is needed to understand the magnitude, and even direction, of these effects on seabirds and cetaceans in space and time.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号