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   42844篇
  免费   549篇
  国内免费   507篇
安全科学   1364篇
废物处理   1655篇
环保管理   6003篇
综合类   6974篇
基础理论   11866篇
环境理论   28篇
污染及防治   11088篇
评价与监测   2538篇
社会与环境   2081篇
灾害及防治   303篇
  2022年   320篇
  2021年   356篇
  2020年   320篇
  2019年   340篇
  2018年   636篇
  2017年   629篇
  2016年   915篇
  2015年   773篇
  2014年   1058篇
  2013年   3255篇
  2012年   1366篇
  2011年   1943篇
  2010年   1539篇
  2009年   1625篇
  2008年   1894篇
  2007年   2026篇
  2006年   1741篇
  2005年   1454篇
  2004年   1446篇
  2003年   1326篇
  2002年   1317篇
  2001年   1647篇
  2000年   1188篇
  1999年   760篇
  1998年   580篇
  1997年   592篇
  1996年   590篇
  1995年   666篇
  1994年   582篇
  1993年   535篇
  1992年   532篇
  1991年   506篇
  1990年   507篇
  1989年   523篇
  1988年   456篇
  1987年   392篇
  1986年   382篇
  1985年   408篇
  1984年   428篇
  1983年   428篇
  1982年   448篇
  1981年   387篇
  1980年   340篇
  1979年   375篇
  1978年   294篇
  1977年   265篇
  1976年   253篇
  1975年   254篇
  1974年   242篇
  1972年   266篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
1.
Environmental Science and Pollution Research - Legacy (i.e., polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCDD)) and alternative halogenated flame retardants (HFRs) were...  相似文献   
2.
Russian Journal of Ecology - Climate change entails shifts in the ranges of woody plants along both latitudinal and altitudinal gradients in the boreal forest biome. In this study,...  相似文献   
3.
The chemical recycling of cellulosic fibres may represent a next-generation fibre–fibre recycling system for cotton textiles, though remaining challenges include how to accommodate fibre blends, dyes, wrinkle-free finishes, and other impurities from finishing. These challenges may disrupt the regeneration process steps and reduce the fibre quality. This study examines the impact on regenerated viscose fibre properties of a novel alkaline/acid bleaching sequence to strip reactive dyes and dimethyloldihydroxyethyleneureas (DMDHEU) wrinkle-free finish from cotton textiles. Potentially, such a bleaching sequence could advantageously be integrated into the viscose process, reducing the costs and environmental impact of the product. The study investigates the spinning performance and mechanical properties (e.g., tenacity and elongation) of the regenerated viscose fibres. The alkaline/acid bleaching sequence was found to strip the reactive dye and DMDHEU wrinkle-free finish from the cotton fabric, so the resulting pulp could successfully be spun into viscose fibres, though the mechanical properties of these fibres were worse than those of commercial viscose fibres. This study finds that reactive dyes and DMDHEU wrinkle-free finish affect the viscose dope quality and the regeneration performance. The results might lead to progress in overcoming quality challenges in cellulosic chemical recycling.  相似文献   
4.
Objective: There have been substantial reductions in motor vehicle crash–related child fatalities due to advances in legislation, public safety campaigns, and engineering. Less is known about non-traffic injuries and fatalities to children in and around motor vehicles. The objective of this study was to describe the frequency of various non-traffic incidents, injuries, and fatalities to children using a unique surveillance system and database.

Methods: Instances of non-traffic injuries and fatalities in the United States to children 0–14 years were tracked from January 1990 to December 2014 using a compilation of sources including media reports, individual accounts from families of affected children, medical examiner reports, police reports, child death review teams, coroner reports, medical professionals, legal professionals, and other various modes of publication.

Results: Over the 25-year period, there were at least 11,759 events resulting in 3,396 deaths. The median age of the affected child was 3.7 years. The incident types included 3,115 children unattended in hot vehicles resulting in 729 deaths, 2,251 backovers resulting in 1,232 deaths, 1,439 frontovers resulting in 692 deaths, 777 vehicles knocked into motion resulting in 227 deaths, 415 underage drivers resulting in 203 deaths, 172 power window incidents resulting in 61 deaths, 134 falls resulting in 54 deaths, 79 fires resulting in 41 deaths, and 3,377 other incidents resulting in 157 deaths.

Conclusions: Non-traffic injuries and fatalities present an important threat to the safety and lives of very young children. Future efforts should consider complementary surveillance mechanisms to systematically and comprehensively capture all non-traffic incidents. Continued education, engineering modifications, advocacy, and legislation can help continue to prevent these incidents and must be incorporated in overall child vehicle safety initiatives.  相似文献   

5.
6.
Conservation conflicts are gaining importance in contemporary conservation scholarship such that conservation may have entered a conflict hype. We attempted to uncover and deconstruct the normative assumptions behind such studies by raising several questions: what are conservation conflicts, what justifies the attention they receive, do conservation-conflict studies limit wildlife conservation, is scientific knowledge stacked against wildlife in conservation conflicts, do conservation-conflict studies adopt a specific view of democracy, can laws be used to force conservation outcomes, why is flexibility needed in managing conservation conflicts, can conservation conflicts be managed by promoting tolerance, and who needs to compromise in conservation conflicts? We suggest that many of the intellectual premises in the field may defang conservation and prevent it from truly addressing the current conservation crisis as it accelerates. By framing conservation conflicts as conflicts between people about wildlife or nature, the field insidiously transfers guilt, whereby human activities are no longer blamed for causing species decline and extinctions but conservation is instead blamed for causing social conflicts. When the focus is on mitigating social conflicts without limiting in any powerful way human activities damaging to nature, conservation-conflict studies risk keeping conservation within the limits of human activities, instead of keeping human activities within the limits of nature. For conservation to successfully stop the biodiversity crisis, we suggest the alternative goal of recognizing nature's right to existence to maintenance of ecological functions and evolutionary processes. Nature being a rights bearer or legal person would imply its needs must be explicitly taken into account in conflict adjudication. If, even in conservation, nature's interests come second to human interests, it may be no surprise that conservation cannot succeed.  相似文献   
7.
8.
This study evaluated the hydrolysis and photolysis kinetics of pyraclostrobin in an aqueous solution using ultra-high-performance liquid chromatography–photodiode array detection and identified the resulting metabolites of pyraclostrobin by hydrolysis and photolysis in paddy water using high-resolution mass spectrometry coupled with liquid chromatography. The effect of solution pH, metal ions and surfactants on the hydrolysis of pyraclostrobin was explored. The hydrolysis half-lives of pyraclostrobin were 23.1–115.5?days and were stable in buffer solution at pH 5.0. The degradation rate of pyraclostrobin in an aqueous solution under sunlight was slower than that under UV photolysis reaction. The half-lives of pyraclostrobin in a buffer solution at pH 5.0, 7.0, 9.0 and in paddy water were less than 12?h under the two light irradiation types. The metabolites of the two processes were identified and compared to further understand the mechanisms underlying hydrolysis and photolysis of pyraclostrobin in natural water. The extracted ions obtained from paddy water were automatically annotated by Compound Discoverer software with manual confirmation of their fragments. Two metabolites were detected and identified in the pyraclostrobin hydrolysis, whereas three metabolites were detected and identified in the photolysis in paddy water.  相似文献   
9.
10.
Ecologically relevant traits of organisms in an assemblage determine an ecosystem's functional fingerprint (i.e., the shape, size, and position of multidimensional trait space). Quantifying changes in functional fingerprints can therefore provide information about the effects of diversity loss or gain through time on ecosystem condition and is a promising approach to monitoring ecological integrity. This, however, is seldom possible owing to limitations in historical surveys and a lack of data on organismal traits, particularly in diverse tropical regions. Using data from detailed bird surveys from 4 periods across more than a century, and morphological and ecological traits of 233 species, we quantified changes in the avian functional fingerprint of a tropical montane forest in the Andes of Colombia. We found that 78% of the variation in functional space, regardless of period, was described by 3 major axes summarizing body size, dispersal ability (indexed by wing shape), and habitat breadth. Changes in species composition significantly altered the functional fingerprint of the assemblage and functional richness and dispersion decreased 35–60%. Owing to species extirpations and to novel additions to the assemblage, functional space decreased over time, but at least 11% of its volume in the 2010s extended to areas of functional space that were unoccupied in the 1910s. The assemblage now includes fewer large-sized species, more species with greater dispersal ability, and fewer habitat specialists. Extirpated species had high functional uniqueness and distinctiveness, resulting in large reductions in functional richness and dispersion after their loss, which implies important consequences for ecosystem integrity. Conservation efforts aimed at maintaining ecosystem function must move beyond seeking to sustain species numbers to designing complementary strategies for the maintenance of ecological function by identifying and conserving species with traits conferring high vulnerability such as large body size, poor dispersal ability, and greater habitat specialization. Article impact statement: Changes in functional fingerprints provide a means to quantify the integrity of ecological assemblages affected by diversity loss or gain.  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