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741.
以渤海湾西岸天津段入海河流的径流量和输沙量数据为基础,采用Kendall秩相关检验法和Mann-Kendall法对近50年入海径流量和输沙量进行了趋势分析和突变性检验.结果表明,近50年来渤海湾西岸天津段入海径流量和输沙量均呈显著下降的趋势.近50年来华北地区降水量减少、天然径流偏低是导致入海径流量减少的自然因素,而流域人类活动如水库和防潮闸的建设,以及沿河取水取沙也是不可忽视的重要因素.该段海岸入海径流量和输沙量的减少已导致河口区盐度上升、水质恶化、沉积物污染等问题,最终会影响河口生态系统的结构和生物资源的可持续发展与利用. 相似文献
742.
南极普里兹湾与太平洋、印度洋海水中90Sr和137Cs的研究 总被引:3,自引:0,他引:3
通过对太平洋、印度洋、南极普里北湾表层海水中^90Sr、^137Cs的分析,可以看出北半球放射必疹高于南半球。南极海域活度最你荒废 域人工放射性核素仍与大气沉降有关。全球人工放性活度吾下降趋势,但各海区下降的程度不同。南极普里兹湾夏季深层水的通升是影响该海区放射性水平的一个重要因素。局部区域的人工放射必不知 度与采样时间和地理位置有关。 相似文献
743.
744.
745.
本文研究了锦州湾海域水体中重金属锌、铅、镉各化学形态的含量及其各形态分布特征,其特征变化动态表明,该海域中重金属以可溶态为主要存在形式,其中以水合氧化物为重要清除载体.重金属除周边岩石风化物质的自然背景值外,主要来源于沿岸工厂排废.水体中重金属是在潮流水动力作用下,受各种理化因素的影响,产生迁移和转化.三种元素形态转化强度 Zn>Pb>Cd,它们污染程度为Cd>Zn>Pb.通过多元回归计算求得重金属与环境因素 pH 值(X_(PH))、Eh 值(X_(Eb))、氯度(X_(cl))、溶解氧(X_(DO))、化学耗氧量(X(COD))的多元一次方程. 相似文献
746.
The impact of wake wash from high-speed ferries on the coastal environment in non-tidal seas is analysed in terms of wave
energy and power, and properties of the largest waves. Shown is that hydrodynamic loads caused by heavy high-speed traffic
may play a decisive role not only in low-energy coasts but also in certain areas with high wind wave activity. For example,
ship-generated waves form, at least, about 5–8% from the total wave energy and about 18–35% from the wave power in the coastal
areas of Tallinn Bay exposed to dominating winds. The periods of wake waves from high-speed ships frequently are much larger
than dominating periods of wind waves. The leading waves typically have a height of about 1 m and a period of 10–15 s. Such
waves extremely seldom occur in natural conditions in many regions of semi-enclosed seas. They cause unusually high hydrodynamic
loads in the deeper part of the nearshore. The fast ferry traffic thus is a qualitatively new forcing component of vital impact
on the local ecosystem. It is demonstrated that wakes from high-speed ferries may trigger considerable changes of the existing
balance of coastal processes. Owing to their low decay rates combined with their exceptional compactness after crossing many
kilometres of the sea surface, such wakes may cause considerable remote impact of the ship traffic. This feature has to be
addressed in the analysis of the impact of harbours and associated ship traffic in the neighbourhood of vulnerable areas. 相似文献
747.
Boesch Donald F. 《Journal of Coastal Conservation》1996,2(1):103-114
The influence of science in the recognition of the effects of landscape changes on coastal ecosystems and in the development
of effective policy for managing and restoring these ecosystems is examined through four case studies: Chesapeake Bay, San
Francisco Bay, the Mississippi Delta, and Florida Bay. These ecosystems have undergone major alterations as a result of changes
in the delivery of water, sediments and nutrients from their watersheds. Both science and management have been challenged
by the spatial, functional and temporal scale mismatches inherent in the watershed-coastal ecosystem relationship. Key factors
affecting the influence of science on management include (1) sustained scientific investigation, responsive to but not totally
defined by managers; (2) clear evidence of change, the scale of the change and the causes of the change; (3) consensus among
the scientific communities associated with various interests; (4) the development of models to guide management actions; (5)
identification of effective and feasible solutions to the problems. 相似文献
748.
Donald F. Boesch 《Journal of Coastal Conservation》1996,2(2):103-114
The influence of science in the recognition of the effects of landscape changes on coastal ecosystems and in the development
of effective policy for managing and restoring these ecosystems is examined through four case studies: Chesapeake Bay, San
Francisco Bay, the Mississippi Delta, and Florida Bay. These ecosystems have undergone major alterations as a result of changes
in the delivery of water, sediments and nutrients from their watersheds. Both science and management have been challenged
by the spatial, functional and temporal scale mismatches inherent in the watershed-coastal ecosystem relationship. Key factors
affecting the influence of science on management include (1) sustained scientific investigation, responsive to but not totally
defined by managers; (2) clear evidence of change, the scale of the change and the causes of the change; (3) consensus among
the scientific communities associated with various interests; (4) the development of models to guide management actions; (5)
identification of effective and feasible solutions to the problems. 相似文献
749.
辽东湾北部至辽西沿岸海域营养盐分布及水质评价 总被引:12,自引:2,他引:12
根据1995-1999年5a对辽东湾北部至辽西沿岸海域的监测资料,分析和评价了该海域营养盐的分布特性及时空变化,评价了营养盐对该海域的污染程度和水质的富营养状况,结果表明该海域营养盐普遍偏高,在5a当中各站位无机氮平均值有56%超一类海水,无机磷有73%超一类海水,辽东湾北部海域高于辽西沿岸海域,最高值位于辽河口和双台子河口的三道沟、裤裆、二界沟3个站位,无机氮高于其他站位3-5倍,这3个站位水质严重污染,处于富营养化状态,随时可诱发赤潮。 相似文献
750.