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   397篇
  免费   30篇
  国内免费   102篇
测绘学   4篇
大气科学   218篇
地球物理   31篇
地质学   70篇
海洋学   34篇
天文学   4篇
综合类   29篇
自然地理   139篇
  2023年   3篇
  2022年   12篇
  2021年   15篇
  2020年   13篇
  2019年   28篇
  2018年   9篇
  2017年   13篇
  2016年   11篇
  2015年   17篇
  2014年   29篇
  2013年   51篇
  2012年   34篇
  2011年   34篇
  2010年   16篇
  2009年   31篇
  2008年   29篇
  2007年   24篇
  2006年   20篇
  2005年   7篇
  2004年   8篇
  2003年   12篇
  2002年   18篇
  2001年   5篇
  2000年   20篇
  1999年   12篇
  1998年   6篇
  1997年   8篇
  1996年   6篇
  1995年   3篇
  1994年   6篇
  1993年   2篇
  1992年   3篇
  1991年   5篇
  1990年   6篇
  1988年   3篇
  1987年   2篇
  1986年   1篇
  1985年   3篇
  1984年   2篇
  1983年   1篇
  1982年   1篇
排序方式: 共有529条查询结果,搜索用时 78 毫秒
161.
162.
For many Indigenous Peoples in the Circumpolar North, cultural engagement and continuity across generations is directly related to relationships between and among people, animals, and landscapes. However, minimal research outlines the emotional responses and disruptions to culture and identity that are driven by ecological change, and the subsequent cultural dimensions of coping and adapting to this uncertainty. Through a case study that explores how caribou population declines and a caribou hunting ban are impacting Inuit in the Nunatsiavut and NunatuKavut regions of Labrador, Canada, this article examines the critical interplay between cultural continuity and adaptive capacity for responding to ecological uncertainty. More specifically, this study: 1) described the central role that caribou play for Inuit emotional wellness, identity, and cultural continuity; 2) explored how the rapid declines of caribou in Labrador are affecting Inuit emotional wellness, identity, and cultural continuity; and 3) characterized the ways in which Inuit are adapting to these emotio-social, cultural, and ecological changes. Drawing from an Inuit-led, multi-year, multi-media qualitative and visual media research program, data from video interviews (n = 84: Nunatsiavut region: n = 54; NunatuKavut region: n = 30) were analyzed using a video-based qualitative analysis, constant-comparative methods, and inductive qualitative approach. Results indicated that caribou are a foundational element for Inuit emotional wellness, identity, and cultural continuity. The changes in caribou populations are resulting in complex emotional responses, losses to cultural meaning and knowledge, and alterations to Inuit identities. The impacts on emotions, identity, and cultural continuity related to Inuit-caribou relations at an individual and collective level reflect the interconnections between cultural continuity and adaptive capacity that underlie the loss of this culturally important species. Though this research focuses on two Inuit groups and caribou in Labrador, the insights from these lived experiences highlight the ongoing cultural and identity consequences associated with species declines occurring globally.  相似文献   
163.
The climatological mean state,seasonal variation and long-term upward trend of 1979–2005 latent heat flux(LHF) in historical runs of 14 coupled general circulation models from CMIP5(Coupled Model Intercomparison Project Phase 5) are evaluated against OAFlux(Objectively Analyzed air–sea Fluxes) data. Inter-model diversity of these models in simulating the annual mean climatological LHF is discussed. Results show that the models can capture the climatological LHF fairly well,but the amplitudes are generally overestimated. Model-simulated seasonal variations of LHF match well with observations with overestimated amplitudes. The possible origins of these biases are wind speed biases in the CMIP5 models. Inter-model diversity analysis shows that the overall stronger or weaker LHF over the tropical and subtropical Pacific region,and the meridional variability of LHF,are the two most notable diversities of the CMIP5 models. Regression analysis indicates that the inter-model diversity may come from the diversity of simulated SST and near-surface atmospheric specific humidity.Comparing the observed long-term upward trend,the trends of LHF and wind speed are largely underestimated,while trends of SST and air specific humidity are grossly overestimated,which may be the origins of the model biases in reproducing the trend of LHF.  相似文献   
164.
The concept of Ecosystem Services (ES), widely understood as the “benefits that humans receive from the natural functioning of healthy ecosystems” (Jeffers et al., 2015), depicts a one-way flow of services from ecosystems to people. We argue that this conceptualisation is overly simplistic and largely inaccurate, neglecting the reality that humans often contribute to the maintenance and enhancement of ecosystems, as often evidenced (but not exclusively) in many traditional and Indigenous societies. Management interventions arising from Ecosystem Services research are thus potentially damaging to both ecosystems and indigenous rights. We present the concept of ‘Services to Ecosystems’ (S2E) to address this, closing the loop of the reciprocal relationship between humans and ecosystems. Case studies from the biocultural ecosystems of Amazonia and the Pacific Northwest of North America (Cascadia) are used to illustrate the concept and provide examples of Services to Ecosystems in past and current societies. Finally, an alternative framework is presented, advancing the existing framework for Ecosystem Services by incorporating this reconceptualization and the loop of reciprocity. The framework aims to facilitate the inclusion of Services to Ecosystems in management strategies based upon Ecosystem Services, and highlights the need for ethnographic research in Ecosystem Service-based interventions.  相似文献   
165.
Although variation of air temperature with respect to terrain altitude is widely understood, less is known about the altitudinal behaviour of precipitation. The eastern slope of Mexico is the most contrasting physiographic province of the country due to its relief. This area is also one of the most important regions of Mexico and of the intertropical region of America because of its biodiversity. Due to the vital and ecosystemic value of precipitation, this work seeks to analyse the altitudinal distribution of precipitation as a function of the relief. Our main methodology consisted of analysing the climatological normal of 86 weather stations to determine accumulated precipitation during rainy, dry and annual periods. Precipitation was correlated with the altitude of the relief, which allowed the study area to be divided into groups relative to the degree of accumulated rainfall throughout the year, as well as by the gradient of variation according to the elevation of the terrain. The results indicated that during the year, precipitation was favoured by the humidity of the Gulf of Mexico and decreased at a rate of -3.7 mm/m in coastal areas. Subsequently, precipitation increased with the altitude of the relief at a rate of 0.7 mm/m, between ~700 and ~ 1500 masl, which is where the greatest accumulation of rainfall was concentrated. Thereafter, it decreased by -0.9 mm/m until it reached the highest volcanic watershed. Crossing this watershed, the foehn effect caused rainfall rates to be much lower than on the windward slope, where the central plateau of the country begins.  相似文献   
166.
利用1981-2018年中国气象局上海台风研究所热带气旋最佳路径资料和国家基本气象站逐日降水资料,对登陆广东北上路径热带气旋活动及强降水特征进行统计分析.结果表明北上热带气旋从登陆时到登陆后48 h是陆地强降水产生的集中时段,登陆时24 h是陆地大暴雨最集中的时段.强降水从沿海向内陆逐渐减少,一般登陆后热带气旋持续时间...  相似文献   
167.
根据广州市番禺区2008—2012年红火蚁发生实测资料和同期气象资料,采用统计学、生物学等方法,建立了广州市番禺区红火蚁发生的气象等级指标。结果表明,红火蚁大发生的气象条件为温度22~27℃,湿度70%~85%或降雨量在1~100 mm,易发生的气象条件为温度22~27℃,较易发生的气象条件为温度20~22℃或27~30℃,不易发生的气象条件为低于20℃或高于30℃。2008—2012年红火蚁发生发展气象等级回代准确率达80%,2013年的试报红火蚁的大发生期4月上旬—5月中旬准确率达到92%。  相似文献   
168.
为加深对云浮高温天气特征的认识,对云浮地区1981—2010年高温天气及其与副高、热带气旋之间关系进行统计分析。结果表明:云浮地区年高温天气大体呈增加趋势,测站局地环境不一致导致各测站高温天气年变化的并不一致。云浮地区高温天气主要出现在6—8月,7月最多,8月次之。云浮地区高温环流形势可分为4类:副高型、台风Ⅰ型、台风Ⅱ型和其它型。500 hPa位势高度(台风强度)与云浮地区台风I型(台风Ⅱ型)高温的关系不明显。500 hPa位势高度较高有利于台风Ⅱ型、副高型、其它型高温的发生发展。500 hPa位势高度大值中心位于测站以北(以西)有利于台风II型(其它型)高温发生发展,位于测站以东时副高型高温较多,位于测站东南则不利于高温天气发生发展。台风中心位于测站东北、东、东南三个方位,台风中心与测站距离600~1 600 km,台风强度在TS及以上时,有利于台风I型高温的发生发展。台风中心位于测站东方方位,台风中心与测站距离1 600~2 200 km,有利于台风Ⅱ型高温的发生发展。  相似文献   
169.
连平鹰嘴蜜桃种植的气候适宜性分析   总被引:3,自引:0,他引:3  
采用连平县1981—2011年的地面观测气象资料,结合连平县气象局鹰嘴蜜桃课题研究组实地调查观测的鹰嘴蜜桃物候期资料及生长发育情况,运用统计学方法从气候基本要素气温、降水等方面分析该县适宜鹰嘴蜜桃种植的气候条件,结果发现该县北部上坪镇的山区坡地,适宜鹰嘴蜜桃的种植;鹰嘴蜜桃生产基地应选择在海拔较高、坡度平缓并且向阳的山坡地;本地正常年份开花时间在2月中旬初到3月上旬中期,鹰嘴蜜桃开花期呈现提前趋势;本地鹰嘴蜜桃种植仍有不利气候因素存在,包括冰雹、雷雨大风和骤雨、干旱、病虫害等,因此要做好相应的防御措施,尽量减少及避免损失。总之,连平北部独特的气候可为鹰嘴蜜桃的高产、高质提供可靠保证。  相似文献   
170.
广宁县白花油茶种植的气候条件分析   总被引:1,自引:0,他引:1  
从热量、水分和光照等方面对广宁县种植白花油茶进行了气候适应性分析,同时总结分析了影响白花油茶生长发育的主要气候灾害及应对措施,并结合广宁县的实际,因地制宜,得出了以下结论:(1)广宁县的热量、水分、光照均适合白花油茶种植;(2)发展广宁油茶种植可选择岑溪软枝油茶系列品种;(3)对原有低产油茶林改造,可以结合油茶林地护理、施肥进行全耕。  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