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   28382篇
  免费   2375篇
  国内免费   3285篇
安全科学   3888篇
废物处理   369篇
环保管理   4974篇
综合类   14612篇
基础理论   2785篇
环境理论   58篇
污染及防治   1396篇
评价与监测   2660篇
社会与环境   2151篇
灾害及防治   1149篇
  2024年   72篇
  2023年   332篇
  2022年   569篇
  2021年   765篇
  2020年   810篇
  2019年   694篇
  2018年   647篇
  2017年   1002篇
  2016年   1152篇
  2015年   1252篇
  2014年   1255篇
  2013年   1742篇
  2012年   1981篇
  2011年   2100篇
  2010年   1607篇
  2009年   1580篇
  2008年   1201篇
  2007年   1851篇
  2006年   1868篇
  2005年   1593篇
  2004年   1317篇
  2003年   1450篇
  2002年   1107篇
  2001年   994篇
  2000年   919篇
  1999年   774篇
  1998年   592篇
  1997年   501篇
  1996年   408篇
  1995年   388篇
  1994年   331篇
  1993年   290篇
  1992年   208篇
  1991年   152篇
  1990年   110篇
  1989年   71篇
  1988年   55篇
  1987年   29篇
  1986年   31篇
  1985年   35篇
  1984年   22篇
  1983年   20篇
  1982年   19篇
  1981年   18篇
  1980年   19篇
  1979年   23篇
  1977年   17篇
  1974年   9篇
  1973年   15篇
  1972年   9篇
排序方式: 共有10000条查询结果,搜索用时 565 毫秒
71.
环境质量评价的生物方法研究   总被引:1,自引:0,他引:1  
环境质量的生物评价是以生物对环境污染的表现为基础的.环境质量评价的生物方法包括环境指示生物的选择,环境质量生物评价指标的确定和环境质量分类等3个步骤.论述了环境污染的生物表现,提出了选择环境指示生物的原则,给出了环境质量生物评价的3类指标,建立了环境质量4级分类体系.  相似文献   
72.
竹子坝料场是官地水电站混凝土浇筑骨料的重要来源之一。结合竹子坝料场的地形地质情况,以及料场开挖后形成的东、南、西三段人工边坡,运用刚体极限平衡的方法进行稳定性分析及其影响因数的研究。  相似文献   
73.
Mycorrhiza is the main spatial and temporal linkage between different constituents in a forest ecosystem. The functional compatibility and stress tolerance of ectomycorrhizal types is species specific, and therefore the information on the ectomycorrhizal community structure can add to the understanding of processes in forest ecosystems and can also be applied as tools for bioindication of pollution stress in forest soils. We have studied the effects of pollution (N and S) on trees and forest soils by: (1) quantification of ECM types diversity as in situ indicators in forest stands, (2) determination and quantification of pollution-sensitive or -insensitive ECM types as passive monitors, (3) root growth and development of ECM on nonmycorrhizal spruce seedlings, planted at the studied sites (active monitors), and (4) ECM infection (a bioassay based on mycorrhizal inoculum potential) of seedlings in an experimental set-up as ex situ testers. ECM species richness for Norway spruce trees (Picea abies) showed higher values in unpolluted sites than in polluted ones, while the differences were not significant for European beech trees (Fagus sylvatica). As pollution-sensitive or -insensitive ECM species in spruce forests, we suggest Hydnum rufescens (sensitive) and Paxillus involutus (unsensitive). Mycorrhizal potential in Norway spruce seedlings as a bioassay for soil N and S pollution was effective, and is suggested as an additional, standardized and widely comparable system in bioindication of soil pollution.  相似文献   
74.
现行财税体制下我国耕地资源数量变化的实证研究   总被引:1,自引:0,他引:1  
耕地资源数量变化受到人口、经济等诸多因素的影响,而财税体制是影响耕地资源数量变化的更深屡次原因。通过数量关系的初步观察和作用机理分析说明我国现行财税体制对耕地资源数量变化存在正反两方面作用,总体来看,对耕地资源保护不利。计量结果进一步证实了我国现行财税体制对耕地资源数量变化存在显著影响。揭示了其影响的方向和大小。根据研究结果,文章有针对性地提出了增加地方财政预算收入,合理分配土地出让金比例和科学使用土地出让金等相关政策建议。  相似文献   
75.
The ongoing development of microbial source tracking has made it possible to identify contamination sources with varying accuracy, depending on the method used. The purpose of this study was to test the efficiency of the antibiotic resistance analysis (ARA) method under low resistance by tracking the fecal sources at Turkey Creek, Oklahoma exhibiting this condition. The resistance patterns of 772 water-isolates, tested with nine antibiotics, were analyzed by discriminant analysis (DA) utilizing a five-source library containing 2250 isolates. The library passed various representativeness tests; however, two of the pulled-sample tests suggested insufficient sampling. The resubstitution test of the library individual sources showed significant isolate misclassification with an average rate of correct classification (ARCC) of 58%. These misclassifications were explained by low antibiotic resistance (Wilcoxon test P < 0.0001). Seasonal DA of stream E. coli isolates for the pooled sources human/livestock/deer indicated that in fall, the human source dominated (P < 0.0001) at a rate of 56%, and that human and livestock respective contributions in winter (35 and 39%), spring (43 and 40%), and summer (37 and 35%) were similar. Deer scored lower (17–28%) than human and livestock at every season. The DA was revised using results from a misclassification analysis to provide a perspective of the effect caused by low antibiotic resistance and a more realistic determination of the fecal source rates at Turkey Creek. The revision increased livestock rates by 13–14% (0.04 ≤ P ≤ 0.06), and decreased human and deer by 6–7%. Negative misclassification into livestock was significant (0.04 ≤ P ≤ 0.06). Low antibiotic resistance showed the greatest effect in this category.  相似文献   
76.
77.
浅论国家环境权   总被引:1,自引:0,他引:1  
随着全球环境的日益恶化和公民环保意识的不断增强,环境权理论迅速发展。国家环境权作为一项重要的环境权。在环境法理论逐步变革和权利内涵不断演进的趋势下,已成为法学界研究探讨的重要课题。通过分析国家环境权的国内、国际法律基础。论证了国家环境权的确立。利用类比的方法。阐述了国家环境权与其他宪法权利的不同之处。从权利义务的对等统一和国内国际两个层面。重新归纳了国家环境权的内容。初步构建了国家环境权的基本理论框架。  相似文献   
78.
根据环境意识结构.设计了旅游管理部门环境意识调查问卷。其主要的指标体系包括:旅游环境知识水平、旅游环境态度、旅游环境评价和旅游环境行为四个方面。对指标体系各部分之间以及每一指标部分的每一题目之间的相对重要性进行权重的确定.而且对各部分的每道题目的各个选项予以赋分。基于权重和赋分.结合调查问卷的实际情况,设计了指标体系各部分评价模型和环境意识总体评价模型。以此来计算草原旅游发展中旅游管理部门环境意识水平的综合得分。经过分析得知,旅游管理部门环境意识模式是“环境知识制约型”模式。  相似文献   
79.
Volunteer monitoring of natural resources is promoted for its ability to increase public awareness, to provide valuable knowledge, and to encourage policy change that promotes ecosystem health. We used the case of volunteer macroinvertebrate monitoring (VMM) in streams to investigate whether the quality of data collected is correlated with data use and organizers' perception of whether they have achieved these outcomes. We examined the relation between site and group characteristics, data quality, data use, and perceived outcomes (education, social capital, and policy change). We found that group size and the degree to which citizen groups perform tasks on their own (rather than aided by professionals) positively correlated with the quality of data collected. Group size and number of years monitoring positively influenced whether a group used their data. While one might expect that groups committed to collecting good-quality data would be more likely to use it, there was no relation between data quality and data use, and no relation between data quality and perceived outcomes. More data use was, however, correlated with a group's feeling of connection to a network of engaged citizens and professionals. While VMM may hold promise for bringing citizens and scientists together to work on joint conservation agendas, our data illustrate that data quality does not correlate with a volunteer group's desire to use their data to promote regulatory change. Therefore, we encourage scientists and citizens alike to recognize this potential disconnect and strive to be explicit about the role of data in conservation efforts.  相似文献   
80.
最优环境税:庇古法则与税制协调   总被引:2,自引:0,他引:2  
从经济学的角度对国外关于最优环境税的经典理论——庇古法则及近十年来研究的前沿内容——一般均衡模型等作出阐释,并在外部性理论的基础上通过一个一般均衡模型考察环境税的效率特性和在次优情形下最优环境税的决定因素。随后是对我国开征环境税的几点思考:环境税的课征范围应暂定为排放各种废水、废气(烟尘)和固体废弃物的行为。环境税税率的确定可以采用“反复迭代”的方法,即“环境效益优先,兼顾税收协调和收入分配等效应。”其他相关问题的处理,如环境税和其它政策手段的配合使用,环境税税收的使用等。  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