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   1794篇
  免费   67篇
  国内免费   76篇
安全科学   151篇
废物处理   15篇
环保管理   381篇
综合类   786篇
基础理论   256篇
环境理论   1篇
污染及防治   80篇
评价与监测   164篇
社会与环境   73篇
灾害及防治   30篇
  2024年   3篇
  2023年   20篇
  2022年   23篇
  2021年   45篇
  2020年   79篇
  2019年   26篇
  2018年   26篇
  2017年   59篇
  2016年   54篇
  2015年   55篇
  2014年   90篇
  2013年   99篇
  2012年   76篇
  2011年   150篇
  2010年   97篇
  2009年   133篇
  2008年   92篇
  2007年   116篇
  2006年   82篇
  2005年   78篇
  2004年   54篇
  2003年   78篇
  2002年   71篇
  2001年   38篇
  2000年   65篇
  1999年   47篇
  1998年   34篇
  1997年   19篇
  1996年   18篇
  1995年   24篇
  1994年   9篇
  1993年   22篇
  1992年   15篇
  1991年   8篇
  1990年   9篇
  1989年   6篇
  1988年   3篇
  1987年   2篇
  1986年   3篇
  1985年   2篇
  1983年   1篇
  1982年   1篇
  1981年   3篇
  1978年   1篇
  1977年   1篇
排序方式: 共有1937条查询结果,搜索用时 15 毫秒
601.
Cosmic exergy based ecological assessment for a wetland in Beijing   总被引:1,自引:0,他引:1  
Wetlands research and restoration has become one of the critical concern due to their importance in providing ecosystem services. This study proposes a holistic methodology to assess the wetland ecosystem based on cosmic exergy as a thermodynamic orientor. This new approach is applied to two typical wastewater treatment facilities (an activated sludge system and a cyclic activated sludge system) and to a constructed wetland ecosystem in Beijing for comparison. Results show that the Beijing wetland ecosystem gains positive net present ecological value of 3.08E+14 Jc regarding its total life cycle. Comparison with the activated sludge system and cyclic activated sludge system, shows that the wetland ecosystem has greater dependencies on local resources (22% vs. 0% vs. 0%) and renewable resources (67% vs. 38% vs. 31%) as well as a larger ecological sustainability index (0.64157 vs. 0.00005 vs. 0.00008). This implies that the wetland ecosystem is more environmentally friendly and sustainable method for water treatment.  相似文献   
602.
Polder lakes in Flanders are stagnant waters that were flooded by the sea in the past. Several of these systems are colonized by exotic species, but have hardly been studied until present. The aim of the present study was: (1) to assess the influence of exotic macrobenthic species on the outcome of the Multimetric Macroinvertebrate Index Flanders (MMIF) and (2) to use classification trees for evaluating to what extent physical-chemical characteristics affect the presence of exotic species.In total, 27 mollusc and 10 macro-crustacean species were present in the monitored lakes of which respectively five and four were exotic. The exclusion of the exotic species from the MMIF resulted in a significant decline of this ecological index (−0.03 ± 0.04; p = 0.00). This elimination often resulted into a lower ecological water quality class and more samples were classified into the bad and poor ecological water quality classes.Single-target classification trees for Gammarus tigrinus and Potamopyrgus antipodarum were constructed, relating environmental parameters and ecological status (MMIF) to the occurrence of both exotic invasive species. The major advantages of using single-target classification trees are the transparency of the rule sets and the possibility to use relatively small datasets. However, this classification technique only predicts a single-target attribute and the trees of the different species are often hard to integrate and use for water managers. As a solution, a multi-target approach was used in the present study. Exotic molluscs and crustaceans communities were modelled based on environmental parameters and the ecological status (MMIF) using multi-target classification trees. Multi-target classification trees can be used in management planning and investment decisions as they can lead to integrated decisions for the whole set of exotic species and avoid the construction of many models for each individual species. These trees provide general insights concerning the occurrence patterns of individual crustaceans and molluscs in an integrated way.  相似文献   
603.
The eleven symposia organized for the 2009 conference of the International Society for Ecological Modelling (ISEM 2009) held in Quebec City, Canada, October 6-9, 2009, included facilitated discussion sessions following formal presentations. Each symposium focused on a specific subject, and all the subjects could be classified into three broad categories: theoretical development, population dynamics and ecosystem processes. Following discussions with the symposia organizers, which indicated that they all shared similar issues and concerns, the facilitated discussions were task-oriented around four basic questions: (1) key challenges in the research area, (2) generating and sharing new ideas, (3) improving collaboration and networking, and (4) increasing visibility to decision-makers, partners and clients. Common challenges that emerged from the symposia included the need for improved communication and collaboration among different academic disciplines, further progress in both theoretical and practical modelling approaches, and accentuation of technology transfer. Regarding the generation and sharing of new ideas, the main issue that emerged was the type of positive interactions that should be encouraged among potential collaborators. The usefulness of the Internet, particularly for the sharing of open-source software and conducting discussion forums, was highlighted for improving collaboration and networking. Several communication tools are available today, and it is important for modellers to use them more intensively. Visibility can be increased by publishing professional newsletters, maintaining informal contacts with the public, organizing educational sessions in primary and secondary schools, and developing simplified analytical frameworks and pilot studies. Specific issues raised in each symposium are also discussed.  相似文献   
604.
Sustainable development or sustainability has been highlighted as an essential principle in urban master planning, with increasing recognition that uncontrollable urbanization may well give rise to various issues such as overexploitation of natural resources, ecosystem destruction, environmental pollution and large-scale climate change. Thus, it is deemed necessary to modify the existing urban and regional administrative system so as to cope with the challenges urban planning is being confronted with and realize the purpose of urban sustainability. This paper contributed to proposing a mechanism which helps to make urban planning with full consideration of issues with respect to sustainable development. We suggested that the integration of urban planning, SEA and ecological planning be a multi-win strategy to offset deficiency of each mentioned political tool being individually applied. We also proposed a framework where SEA and ecological planning are fully incorporated into urban planning, which forms a two-way constraint mechanism to ascertain environmental quality of urban planning, although in practice, planning and SEA processes may conditionally be unified. Moreover, as shown in the case study, the integration of the three political tools may be constrained due to slow changes in the contextual factors, in particular the political and cultural dimensions. Currently within the context of China, there may be three major elements which facilitate integration of the three political tools, which are (1) regulatory requirement of PEIA on urban planning, (2) the promotion or strong administrative support from government on eco-district building, and (3) the willingness of urban planners to collaborate with SEA experts or ecologists.  相似文献   
605.
This paper identified the dimensions of proactive socialization behavior among Chinese employees. We examined the mediating effects of perceived insider status on the relationships between proactive socialization behavior and socialization outcomes, and the moderating effect of supervisors' traditionality on the relationship between proactive socialization behavior and perceived insider status. Results from 280 newcomer–supervisor pairs supported the hypotheses that proactive socialization behavior was positively associated with task performance and social integration through perceived insider status. In addition, supervisors' traditionality significantly influenced the indirect relationships that proactive socialization behavior had with task performance and social integration via perceived insider status, such that the relationships became weaker as supervisors' traditionality increased. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
606.
垫江县次级河流部分水质指标不容乐观,以种植污染、养殖污染和生活污染为代表的农村面源污染日渐成为垫江河流污染的主要因素。改变垫江河流水质现状,必须尽量减少化肥农药施用,改变传统养殖模式,完善农村垃圾收运系统,加快建设农村废水治理设施。  相似文献   
607.
It is difficult to manage the manufacturing hazardous waste (MHW) which is generated from a huge amount of complicated sources and causes very serious pollution. Therefore more and more attention has been paid to MHW pollution. Shanghai, as an industrial and economic center and an international metropolis in China, has a vast industrial system spanning a multitude of sectors, which generates MHW not only in a huge magnitude but also in a large variety of types from complicated sources, resulting in severe pollution. In 2003, the production of MHW in Shanghai is about 3.96 × 10^5 ton, involving 33 indices. Most of MHW in Shanghai is treated and disposed of, but a significant portion is not handled properly and effectively. This paper carries out infield investigation on the current status of MHW production and treatment in Shanghai, and puts forward scientific proposals that Shanghai should facilitate cleaner production and minimize haz- ardous waste; strictly enforce hazardous waste registration system, strengthen monitoring the certified enterprises; strengthen intent disposal center construction and realize hazardous waste reclamation; accelerate establishing the technical criteria and the management policy, promote the research and development on the treatment and disposal technology, and strengthen information management, thus realizing integrated management on MHW pollution.  相似文献   
608.
Honest advertisement models of sexual selection propose that exaggerated secondary sexual ornaments are condition-dependent, and that only individuals with superior disease resistance will be able to express costly ornamentation. Studies of secondary sexual ornamentation and their maintenance by sexual selection tend to focus on males. However, females may also possess showy ornaments. We investigated whether female ornaments, in the form of sexual swellings, reliably signal female fitness in a semifree-ranging colony of mandrills (Mandrillus sphinx) at the Centre International de Recherches Médicales, Franceville (CIRMF), Gabon. We measured swelling height and width using photographs of periovulatory females over three mating seasons and compared swelling size with parasitism (using fecal analysis over one annual cycle), immune status (ratio of lymphocytes to neutrophils in blood smears made during captures), and genetic diversity (microsatellite heterozygosity). Swelling size varied by up to 10% between cycles in individual females, giving some support to the hypothesis that size differences may indicate the quality of individual swelling cycles. However, there was no significant difference in swelling size between conceptive and nonconceptive cycles. Measures of swelling size varied more between females than within females across swelling cycles, implying that swelling size was a relatively consistent characteristic of individual females. Swelling size was not significantly related to either general measures of parasitism and immune status, or to the closest available measures to each swelling cycle. Nor was swelling size significantly related to genetic diversity. The healthy, provisioned nature of the colony and problems associated with observational, correlational studies restrict interpretation of our data. However, in combination with previous findings that females of higher reproductive success do not show larger swellings, and that males do not allocate mating effort as a function of swelling size, these results imply that sexual swelling size does not indicate female quality in these semifree-ranging mandrills.  相似文献   
609.
国家森林公园生态评价方法研究   总被引:4,自引:0,他引:4  
严山  周良 《环境导报》1998,(3):35-37
宝华山国家级森林公园是华东地区自然生态环境保存比较完好的北亚热带森林生态系统,通过建立多层次的生态评价指标体系,运用指标赋分和加权平均法,对宝华山林林公园进行评价。结果认为,该森林公园具有一定的代表意义和较高的保护开发价值。  相似文献   
610.
我国农村生态贫困研究   总被引:13,自引:0,他引:13  
本文在界定生态贫困内涵的基础上,对我国农村生态贫困的规模作了粗略的估计,并对我国农村生态贫困的特征、形成机理和治理对策进行了分析。  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