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   1579篇
  免费   154篇
  国内免费   245篇
安全科学   22篇
废物处理   11篇
环保管理   198篇
综合类   848篇
基础理论   546篇
污染及防治   59篇
评价与监测   74篇
社会与环境   209篇
灾害及防治   11篇
  2024年   11篇
  2023年   38篇
  2022年   72篇
  2021年   55篇
  2020年   52篇
  2019年   47篇
  2018年   55篇
  2017年   72篇
  2016年   63篇
  2015年   76篇
  2014年   72篇
  2013年   107篇
  2012年   85篇
  2011年   132篇
  2010年   110篇
  2009年   97篇
  2008年   75篇
  2007年   109篇
  2006年   122篇
  2005年   87篇
  2004年   76篇
  2003年   72篇
  2002年   42篇
  2001年   37篇
  2000年   36篇
  1999年   28篇
  1998年   26篇
  1997年   20篇
  1996年   23篇
  1995年   21篇
  1994年   12篇
  1993年   15篇
  1992年   7篇
  1991年   6篇
  1990年   7篇
  1989年   1篇
  1988年   4篇
  1987年   1篇
  1986年   2篇
  1981年   1篇
  1980年   1篇
  1979年   1篇
  1977年   2篇
排序方式: 共有1978条查询结果,搜索用时 15 毫秒
441.
Abstract: The Mediterranean Basin is a global hotspot of biodiversity. Hotspots are said to be experiencing a major loss of habitat, but an added risk could be the decline of some species having a special role in ecological relationships of the system. We reviewed the role of European rabbits (Oryctolagus cuniculus) as a keystone species in the Iberian Peninsula portion of the Mediterranean hotspot. Rabbits conspicuously alter plant species composition and vegetation structure through grazing and seed dispersal, which creates open areas and preserves plant species diversity. Moreover, rabbit latrines have a demonstrable effect on soil fertility and plant growth and provide new feeding resources for many invertebrate species. Rabbit burrows provide nest sites and shelter for vertebrates and invertebrates. In addition, rabbits serve as prey for a number of predators, including the critically endangered Iberian lynx (Lynx pardinus) and Spanish Imperial Eagle (Aquila adalberti). Thus, the Mediterranean ecosystem of the Iberian Peninsula should be termed “the rabbit's ecosystem.” To our knowledge, this is the first empirical support for existence of a multifunctional keystone species in a global hotspot of biodiversity. Rabbit populations have declined drastically on the Iberian Peninsula, with potential cascading effects and serious ecological and economic consequences. From this perspective, rabbit recovery is one of the biggest challenges for conservation of the Mediterranean Basin hotspot.  相似文献   
442.
Ladybirds (Coleoptera: Coccinellidae) provide services that are critical to food production, and they fulfill an ecological role as a food source for predators. The richness, abundance, and distribution of ladybirds, however, are compromised by many anthropogenic threats. Meanwhile, a lack of knowledge of the conservation status of most species and the factors driving their population dynamics hinders the development and implementation of conservation strategies for ladybirds. We conducted a review of the literature on the ecology, diversity, and conservation of ladybirds to identify their key ecological threats. Ladybird populations are most affected by climate factors, landscape composition, and biological invasions. We suggest mitigating actions for ladybird conservation and recovery. Short-term actions include citizen science programs and education, protective measures for habitat recovery and threatened species, prevention of the introduction of non-native species, and the maintenance and restoration of natural areas and landscape heterogeneity. Mid-term actions involve the analysis of data from monitoring programs and insect collections to disentangle the effect of different threats to ladybird populations, understand habitat use by taxa on which there is limited knowledge, and quantify temporal trends of abundance, diversity, and biomass along a management-intensity gradient. Long-term actions include the development of a worldwide monitoring program based on standardized sampling to fill data gaps, increase explanatory power, streamline analyses, and facilitate global collaborations.  相似文献   
443.
根据大量的观测分析资料,论述了刚果W5桉树人工林生态系统养分的地球化学循环和生物小循环。研究结果表明,每公顷每年通过地表径流和地下渗漏从生态系统输出的养分质量以K最多,达21.25 kg/(hm2a);其次为N,达17.21 kg/(hm2a)。桉树人工林生态系统养分流通质量的净变化值f(K)、f(Ca)为负值,f(N)、f(P)、f(Mg)为正值;桉树人工林生态系统养分的生物小循环研究表明,在一个轮伐期内,每公顷桉树吸收养分的质量,依次为Ca 429.03 kg/hm2,其次为N 277.01 kg/hm2和K 208.12 kg/hm2。而在一个轮伐期中归还的养分质量,Ca只有99.78 kg/hm2,K为113.04 kg/hm2。在养分循环率方面,与热带半落叶季雨林比较,桉树人工林生态系统的养分循环率要小得多,说明桉树人工林土壤养分趋向于减少。  相似文献   
444.
运用灰色关联法对南亚热带鹤山丘陵试验站4种森林生态系统植被状况影响地表径流系数进行了定量分析,结果表明:对于本文所选取的植被状况参数对地表径流系数影响的大小顺序是:枯落叶层厚度〉草本层盖度〉灌木层盖度〉林分高;4种森林生态系统的植被状况对地表径流系数的影响,马占相思林最大,平权关联度与非平权灰关联度分别为0.782和0.766;林果苗系统最小,平权关联度与非平权灰关联度分别为0.532和0.535  相似文献   
445.
扬州市水复合生态系统问题的生态学实质及调控对策   总被引:5,自引:0,他引:5  
分析了扬州市水复合生态问题的生态学实质:水生态过程的生态阻滞或耗竭;生态系统结构的破碎与功能的板结;水生态调控机制的匮缺和水生态意识的低下,并针对性地提出了水复合生态系统的调控对策。  相似文献   
446.
生态系统的数据结构不同于商用数据结构。本文参考美国LTERN的Sevilleta站生态系统的数据管理模式,结合中国科学院封丘农业生态实验站的实际情况,着重介绍了生态系统的数据文档文件的特点、结构和应用,而这些都是研究生态系统数据管理的最基础工作。  相似文献   
447.
涕灭威污染体系研究现场土壤生态系统表征   总被引:1,自引:0,他引:1  
以湖北省卢龙县刘天庄邵时各村农田生态系统为例,阐述了生态系统的表生方法,得出该生态系统利于做复合污染物的研究,且系统中农药的降解有明显的复杂性,与实验室模拟有差异。为进一步研究复合化学污染物在该生态系统中多介质多界面的环境行为提供了依据。  相似文献   
448.
城市生态安全评价研究   总被引:47,自引:4,他引:47  
城市生态安全是指城市生态环境支撑条件以及所面临生态环境问题不对其生存和发展造成威胁,即城市生态系统功能和过程能够满足其持续生存与发展需求。以佛山市为例,选择了资源、环境、生物和灾害等因素,各因素再选择若干评价要素,采用几何平均法计算了城市生态系统安全指数。资源安全评价选择了能源、水资源和粮食等要素,其安全指数为0.22;环境安全评价选择了水环境、大气环境、固体废物和农业环境,其安全指数为0.58;生物安全因素安全评价选择了生物多样性保护、外来入侵物种、森林植被等要素,其安全指数为0.30;选择水土流失、地质灾害、气象灾害和生物灾害等要素进行生态灾害安全评价,指数为0.79;佛山市生态安全综合指数为0.42。研究还表明,生态安全评价宜根据最小限制因子定律,选择关键影响因子进行评价。  相似文献   
449.
大量梯级水电开发对河流生态系统的健康状况产生重要影响。以乌溪江梯级水库为研究区域,2017年6—11月对上游湖南镇水库和下游黄坛口水库的营养特征及浮游植物组成进行了调查,并应用生物完整性评价指数对水库水生态系统进行健康评价。结果表明,乌溪江梯级水库氮、磷、有机物含量较低,处于贫营养状态。调查期间共鉴定浮游植物8门152种,其中蓝藻门和绿藻门的密度较高,下游黄坛口水库的浮游植物密度低于上游湖南镇水库。生物完整性指数评价结果显示,乌溪江梯级水库生物完整性较高,处于一般到亚健康状态,该指数受水温影响明显,水温低时黄坛口水库的健康状况较好,水温高时湖南镇水库的健康状况较好。  相似文献   
450.
As a special ecosystem, an urban forest park, which is different from a regular “forest park”, is one of the key elements involved in improving the urban ecological environment and promoting the sustainable development of a city. The “urban forest park” can also significantly improve living conditions by acting as a greenbelt. The Chengdu Longquan Mountain Urban Forest Park is a rare mountain urban forest park located in the center of the city. This “urban forest park” not only provides more ecological products and maintains ecological security but also meets the growing needs of people for food, environmental quality, and spirituality. To comprehensively assess the ecological value of the Chengdu Longquan Mountain Urban Forest Park, this study used the literature analogy and questionnaire survey methods to establish a targeted ecosystem service assessment system in this study area. In addition, combined with the hierarchical analysis method, the indicator system was tested, and the specific evaluation index was determined. In the Longquan Mountain Urban Forest Park Ecosystem Service Value Index System, three first-level indicators, such as ecological material products (with a weight of 0.412 6), ecological regulation (0.327 5), and dwelling culture (0.259 9); eight secondary indicators, such as product production (0.206 3), resource supply (0.206 3), and biodiversity (0.194 4); and twenty-three tertiary indicators, such as air negative oxygen ion (0.154 7), habitat quality (0.095 9), and ecological health benefit (0.075 5), were identified. From the weights of the first and second indicators, it was clear that the supply of ecological material products is the main service function in the Longquan Mountain Urban Forest Park ecosystem. Moreover, from the weights of the third indicator, the public’s cognition and concept of the ecosystem service value of the “urban forest park” gradually shifted from the supply service of products and resources to cultural services. In summary, the ecosystem service value assessment system designed for the Longquan Mountain Urban Forest Park in this study has certain feasibility and extensibility that lays a theoretical foundation for the scientific assessment of ecological value and ecological value realization mechanism for other “forest parks” worldwide. © 2022 Authors. All rights reserved.  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