全文获取类型
收费全文 | 369篇 |
免费 | 62篇 |
国内免费 | 68篇 |
专业分类
测绘学 | 30篇 |
大气科学 | 55篇 |
地球物理 | 64篇 |
地质学 | 92篇 |
海洋学 | 155篇 |
综合类 | 49篇 |
自然地理 | 54篇 |
出版年
2024年 | 2篇 |
2023年 | 8篇 |
2022年 | 15篇 |
2021年 | 18篇 |
2020年 | 13篇 |
2019年 | 16篇 |
2018年 | 6篇 |
2017年 | 12篇 |
2016年 | 9篇 |
2015年 | 9篇 |
2014年 | 27篇 |
2013年 | 17篇 |
2012年 | 14篇 |
2011年 | 12篇 |
2010年 | 33篇 |
2009年 | 13篇 |
2008年 | 18篇 |
2007年 | 32篇 |
2006年 | 24篇 |
2005年 | 23篇 |
2004年 | 18篇 |
2003年 | 22篇 |
2002年 | 14篇 |
2001年 | 13篇 |
2000年 | 16篇 |
1999年 | 16篇 |
1998年 | 13篇 |
1997年 | 11篇 |
1996年 | 5篇 |
1995年 | 18篇 |
1994年 | 6篇 |
1993年 | 9篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有499条查询结果,搜索用时 15 毫秒
121.
利用多时相的高光谱航空图像监测冬小麦条锈病 总被引:31,自引:1,他引:31
冬小麦发生锈病 ,叶绿素被大量破坏 ,水分蒸滕量大大增加 ,叶片细胞大小、形态、叶片结构发生了改变 ,从而改变了叶片和冠层的光学特性 ,使得遥感探测与评价成为可能。利用多时相的高光谱航空飞行图像数据 ,了解、分析和发现条锈病病害对作物光谱的影响及其光谱特征 ;设计了病害光谱指数 ,成功地监测了冬小麦条锈病病害程度与范围。对比 3个生育期的条锈病与正常生长冬小麦的PHI图像光谱及光谱特征 ,发现 :5 6 0— 6 70nm黄边、红谷波段 ,条锈病病害冬小麦的冠层反射率高于正常生长的冬小麦光谱反射率 ;近红外波段 ,条锈病病害的冠层反射率低于正常生长的冬小麦光谱反射率 ;条锈病冬小麦冠层光谱红谷吸收深度和绿峰的反射峰高度都会减小 相似文献
122.
疾病发病与特殊天气过程的相关特征 总被引:6,自引:2,他引:6
利用2002、2003年8次特殊天气过程期间的社区医院疾病调查资料以及同期的气象资料,分析和讨论了各种天气对疾病发病的影响,特别是对心脑血管疾病的影响。所得结果表明:①各种天气过程中,冷空气、大雾天气对人体健康和疾病发生影响较大;②对于60岁以上的老人来说,寒冷天气、强对流天气、闷热天气和大雪天气对男性的影响明显大于女性;③特殊天气的敏感人群是60岁以上的老人。患有心脑血管疾病的患者应特别注意大雾、闷热和寒冷天气,而高血压患者应特别注意低气压天气,特别是冬季的大雪天气。 相似文献
123.
文章通过瑞雷面波法在呼集高速公路路基病害调查中的工作实例及现场工作方法,论述了该技术在高速公路路基病害调查中的应用前景及推广价值. 相似文献
124.
Atiqur Rahman 《GeoJournal》2006,65(3):211-227
The main objectives of the present study are: (i) to assess the income-wise household environmental conditions of the sampled
households in Aligarh city, (ii) to examine income-wise disease profile of the population, (iii) to assess the relationship
between income and four most occurring diseases, (iv) draw out inter-relationship between income, non-ideal household environmental
conditions and environment related diseases. The quality of life and diseases in any urban areas get reflected by the immediate
neighborhood in different parts of the city which depends upon the income strata of the households, their way of living, and
their understanding of their household environment. This is because it is the household environment, which exerts the most
and immediate influence on the life of the people. This study was carried out in order to assess household environmental conditions
(i.e. housing conditions, bathroom and sanitation conditions, water supply conditions, water logging conditions, household
garbage and solid waste, household pests, indoor air and indoor noise pollution) and their effect on the health of the resident
population of Aligarh city. The method includes household survey of Aligarh city using questionnaires. The sampled households
were classified into five income groups from very low to very high. Relationship was tested between income and household environmental
conditions and also between income and diseases using Chi-Square technique. About 55% of the total sampled households suffer
from diarrhea/dysentery, 43% jaundice, 42% malaria and 41% respiratory diseases. About 40% suffer from skin diseases, small
pox/chicken pox. All these diseases are a result of poor household environmental conditions. Whereas 35% people reported other
diseases (i.e. heart disease, hypertension and diabetes), only 14.42% households reported of tuberculosis. The study concludes
that there exists a significant positive relationship between income level and household environmental conditions, and also
between income and various diseases among sampled households of Aligarh city. 相似文献
125.
126.
The North Atlantic Younger Dryas climatic reversal did not cause a glacier advance on Mount Rainier. The glaciers on Mount Rainier seem to have advanced in response to regional or local shifts in climate. However, the Younger Dryas climatic reversal may have affected the Mount Rainier area, causing a cold, but dry, climate unfavorable to glacier advances. Glaciers in the vicinity of Mount Rainier advanced twice during late glacial/early Holocene time. Radiocarbon dates obtained from lake sediments adjacent to the corresponding moraines are concordant, indicating that the ages for the advances are closely limiting. The first advance occurred before 11,300 14C yr BP (13,200 cal yr BP). During the North Atlantic Younger Dryas event, between 11,000 and 10,000 14C yr BP (12,900 and 11,600 cal yr BP), glaciers retreated on Mount Rainier, probably due to a lack of available moisture, but conditions may have remained cold. The onset of warmer conditions on Mount Rainier occurred around 10,000 14C yr BP (11,600 cal yr BP). Organic sedimentation lasted for at least 700 years before glaciers readvanced between 9800 and 8950 14C yr BP (10,900 and 9950 cal yr BP). 相似文献
127.
Prosopis 《Journal of Arid Environments》1995,30(4)
Canker and tip-dieback diseases have been found in field and greenhouse plantings ofProsopisbeing examined in agroforestry trials in South Texas. Several fungal species were associated with the field cankers, most notably aLasiodiplodiaand aPestalotiopsis. In the greenhouse, a tip-dieback as well as a canker disease that began at pruning cuts on the stock plants was seen.Pestalotiopsiswas most commonly isolated from these plants. Isolated cultures of theLasiodiplodiaand thePestalotiopsistogether with several other often associated fungi, (includingAlternariaFusarium) were tested for pathogenicity on young mesquite plants. OnlyLasiodiplodiaandPestalotiopsisproduced cankers under the conditions tested when spores were applied using wound inoculation techniques.Pestalotiopsisrequired high wound inoculation techniques.Pestalotiopsisrequired high humidity and proved much less damaging compared toLasiodiplodia, which closely mimicked the field symptoms. Benlate was found to give the greatest growth inhibition of these fungal pathogens inin vitrofungicide tests. 相似文献
128.
1IntroductionSongbaiTown—thecapitaloftheShengnongjiaforestdistrictisthecenteroflocalpolitics,eco nomicsandculture ,anditisalsoanimportanttourismbase.Butinrecentyears,thelocalinhabi tantsinthisareahavesufferedfromcalculusdiseaseoccasionallyandthediseaseseemstobeofmoreandmorefrequentoccurrence .Thisnotonlycausesmasspanicandinfluencesnormalworkandstudyofthelocalpeople ,butalsobringsaboutnegativeeffectsontouristindustryofthisareaandrestrictsthedevelopmentoflocaleconomy .Inordertounderstandthesta… 相似文献
129.
130.
在研究区生态系统中,岩石、粮作物中硒含量正常,而土壤、水、儿童患头发中硒含量明显不足;人体硒摄入量不足是该区大骨节病病情复发活跃的主要因素之一。采用有效的补硒措施,提高和改善人体硒水平是预防大骨节病复发的关键。 相似文献