全文获取类型
收费全文 | 114篇 |
免费 | 12篇 |
国内免费 | 19篇 |
专业分类
安全科学 | 5篇 |
废物处理 | 4篇 |
环保管理 | 22篇 |
综合类 | 60篇 |
基础理论 | 34篇 |
污染及防治 | 4篇 |
评价与监测 | 11篇 |
社会与环境 | 1篇 |
灾害及防治 | 4篇 |
出版年
2023年 | 5篇 |
2022年 | 1篇 |
2021年 | 5篇 |
2020年 | 3篇 |
2019年 | 1篇 |
2018年 | 5篇 |
2017年 | 7篇 |
2016年 | 2篇 |
2014年 | 3篇 |
2013年 | 10篇 |
2012年 | 5篇 |
2011年 | 11篇 |
2010年 | 13篇 |
2009年 | 7篇 |
2008年 | 4篇 |
2007年 | 9篇 |
2006年 | 3篇 |
2005年 | 8篇 |
2004年 | 6篇 |
2003年 | 10篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有145条查询结果,搜索用时 21 毫秒
31.
结合塔里木河下游输水和中游段输水堤防建设工程,在下游、中游分别设置了9个和3个地下水位和地下水化学特征监测断面,并在中游的3个断面和下游的6个典型断面进行了植物样方调查,以分析综合治理工程的实施对地下水和植被的影响.结果表明,在生态输水影响下,塔里木河下游断流河道两岸地下水位抬升显著,植被的盖度有明显增加,胡杨的当年生枝叶都表现出积极变化;塔里木河中游地区在建有输水堤防又有生态闸的断面地下水位、水质以及植被综合优势比均明显好于无生态闸断面. 相似文献
32.
33.
This study improved the application of the Holdridge life-zone model to simulate the distribution of desert vegetation in China which gives statistics to support eco-recovery and ecosystem reconstruction in desert area. This study classified the desert vegetation into four types: (1) LAD: little arbor desert; (2) SD: shrub desert: (3) HLHSD: half-shrub, little half-shrub desert; (4) LHSCD: little halfshrub cushion desert. Based on the classification of Xinjiang desert vegetation, the classical Holdridge life-zone model was used to simulate Xinjiang desert vegetation's distribution and compare the Kappa coefficient result of the model with table of accuracy represented by Kappa values. The Kappa value of the model was only 0.19, it means the simulation result was poor. To improve the life-zone model application to Xinjiang desert vegetation type, a set of plot standards for terrain factors was developed by using the plot standard as the reclassification criterion to climate sub-regime. Then the desert vegetation in Xinjiang was simulated. The average Kappa value of the second simulation to the respective climate regime was 0.45. The Kappa value of final modeling result was 0.64, which is the better value. The modification of the model made it in more application region. In the end, the model' s ecological relevance to the Xinjiang desert vegetation types was studied. 相似文献
34.
塔克拉玛干4种荒漠植物气体交换与环境因子的关系初探 总被引:17,自引:0,他引:17
研究了4种荒漠植物)胡杨,疏叶骆驼刺,头状沙拐枣,多枝柽柳)气体交换的季节变化及其与环境因子的关系。结果:(1)外界环境因子中,无论是对光合速率还是蒸腾速率,光照强度都是最重要的主导因子,其次是气温,大气湿度与植物的蒸腾速率成负相关,影响程度因不同植物及其环境因子的情况而有所不同。(2)在气温越高的地方,荒漠植物的温度生态位(包括最适温度和极限温度)也随之增高。(3)水分胁迫影响气温和叶温的差异,4种植物都能调整其叶温,使之低于沙漠地区的极度高温。 相似文献
35.
目的研究湿热海洋、干热沙漠两种典型大气环境对7A85铝合金腐蚀行为的影响。方法在万宁、敦煌两种典型环境中开展7A85铝合金大气暴露试验,利用金相显微镜分析7A85铝合金在我国两种典型大气环境中的腐蚀特征,定期测试该材料的拉伸强度和腐蚀深度。结果暴露3 a,7A85铝合金湿热海洋、干热沙漠两种典型大气环境中的最大腐蚀深度分别为254、90μm,抗拉强度分别下降了18%和5%,断后伸长率分别下降了72%和22%。结论 7A85铝合金暴露于相对湿度较低的干热沙漠环境,表面形成的腐蚀产物膜会阻止腐蚀的进一步发生;暴露于湿热海洋大气环境,随暴露时间的延长,7A85铝合金腐蚀逐渐加深。 相似文献
36.
为查明我国北方沙漠地区降水化学组成及来源,在阿拉善沙漠高原阿右旗气象站采集了2013—2015年的降水样品,测定了降水pH、EC(电导率)及主要离子当量浓度.结果表明:阿拉善沙漠阿右旗气象站降水pH和EC的范围分别为6.66~8.05和35~1 237 μS/cm;Ca2+、SO42-、Na+和Cl-为降水中的主要离子,其总和占总离子的85%以上.降水pH、EC和主要离子当量浓度是反映空气质量的基本参数,较高的降水pH反映出当地降水具有明显的碱性特征.与其他地区相比,该地区降水的EC和可溶性离子日均湿沉降通量也较高,且随月份有较大的变化,表明干旱沙漠粉尘对当地降水水化学的贡献较大.根据离子来源相对贡献的计算结果发现,降水中92.8%的SO42-和98%的NO3-来自人为源,98.8%的Ca2+和88.7%的K+为陆地来源,55%的Mg2+为海洋源,24.8%的Na+来自矿物风化,极少部分Cl-为人为源.研究显示:除降水中的NH4+外,其他主要离子之间的相关性表明各种成因物质在风力作用下同时进入了大气;基于[NH4+](NH4+的当量浓度)与[K+](K+的当量浓度)相关性分析,降水中的NH4+来自生物质燃烧、肥料使用、动物粪便等. 相似文献
37.
Gregory E. Insarov Serguei M. Semenov Irina D. Insarova 《Environmental monitoring and assessment》1999,55(2):279-298
The issue of biological monitoring of the local consequences of anticipated global climate change is considered for the Central Negev Highlands, Israel. Epilithic lichens are suggested as biological monitors. The proposed methodology of such monitoring consists of a sampling scheme, including lichen measurement along transects on flat calcareous rocks, and construction of a trend detection index (TDI). TDI is a sum of lichen species cover with coefficients chosen so as to ensure maximum ability to detect global climate trends. Coefficients have been estimated in a study of lichens along an altitudinal gradient from 500 to 1000 m a.s.l. The gradient study demonstrated that the TDI index is performed better than other integrated indices. Recommendations on this system to monitor climate change with epilthic lichens are given. Measuring, for instance, a hundred transects in fifty plots (two transet per plot scheme) allows one to detect a climate-driven change in the epilithic lichen community corresponding to a 0.8 °C shift in annual mean temperature. Such resolution appears sufficient in view of global warming of 2.5 °C considered by the Intergovernmental Panel on Climate Change as a realistic prediction for the end of the next century. 相似文献
38.
沙漠公路驾驶员心理、生理特性初探 总被引:5,自引:4,他引:1
针对沙漠公路交通安全现状,采用动体视力、速度估计、复杂(选择)反应、处置判断、血压脉搏检测仪等驾驶适宜性检测仪器,就长期从事沙漠公路运输活动的驾驶员群体进行了包括视觉、速度估计、反应、判断等在内的心理、生理特性的实地测试。检测结果初步表明,沙漠公路特殊的线形布设和修筑技术特征以及沿线的自然环境条件,使得驾驶员表现出有别于一般绿洲公路的驾驶心理和行为特性,其主要表现在在沙漠环境中,驾驶员的动体视力要较静体视力受到更大的影响;急躁心理影响,沙漠公路驾驶员的速度估计和复杂反应时间相应指标值均小于全国平均水平;沙漠公路驾驶员复杂反应错误次数和处置判断错误次数均高于绿洲公路。 相似文献
39.
Southern California desert public lands receive especially high levels of off-highway recreation due to large population centers
nearby and popular riding environments such as sand dunes. Controversy has developed over the flat-tailed horned lizard (Phrynosoma mcallii), previously a candidate for listing under the Endangered Species Act. Some evidence suggests lower lizard abundance in areas
of higher recreational use than in areas with low or no use. We designed a manipulative experiment to ensure maximum inference
in evaluating the direct impact of recreational riding of off-highway vehicles on lizards. Thirty-six lizards, in situ, were
treated with an off-highway vehicle treatment during hibernation season in three treatment groups: high impact, low impact,
and control. Treatments consisted of timed riding by off-highway vehicles. In all treatment groups survival was 100%, despite
hibernation of lizards at very shallow depths. Consequently, indirect effects of off-highway vehicles deserve increased attention.
The relative importance of direct versus indirect (i.e., degradation of lizard habitat) impacts caused by off-highway vehicles
remains unknown. These indirect effects may include the altering of vegetation, substrate, and prey. We recommend that a manipulative
approach be adopted to investigate these possibilities. 相似文献
40.
干旱区荒漠植被的特点及恢复问题的研究--以塔里木河流域胡杨林生态系统为例 总被引:2,自引:0,他引:2
干旱区除存在唯一的真正森林-胡杨(Populuseuphratica)林外,植被普遍极其稀疏,以降水稀少,蒸发显著为特点的干旱区,荒漠植被的存在对于生态环境的保护和良性发展起到极大的作用,干旱区的荒漠植被表现出特有的生理特征,本文研究塔里木河流域胡杨林的特征及对生态环境的适应规律,进一步提出了扩展荒漠植被的可能性及其措施。 相似文献