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   597篇
  免费   8篇
  国内免费   18篇
安全科学   26篇
废物处理   22篇
环保管理   151篇
综合类   58篇
基础理论   141篇
污染及防治   162篇
评价与监测   40篇
社会与环境   19篇
灾害及防治   4篇
  2023年   2篇
  2022年   2篇
  2021年   2篇
  2020年   3篇
  2019年   2篇
  2018年   8篇
  2017年   4篇
  2016年   12篇
  2015年   11篇
  2014年   11篇
  2013年   81篇
  2012年   16篇
  2011年   14篇
  2010年   11篇
  2009年   19篇
  2008年   32篇
  2007年   29篇
  2006年   22篇
  2005年   20篇
  2004年   28篇
  2003年   24篇
  2002年   24篇
  2001年   20篇
  2000年   15篇
  1999年   12篇
  1998年   9篇
  1997年   6篇
  1996年   7篇
  1995年   8篇
  1994年   7篇
  1993年   5篇
  1992年   14篇
  1991年   8篇
  1990年   5篇
  1989年   9篇
  1988年   9篇
  1987年   4篇
  1986年   8篇
  1985年   10篇
  1984年   11篇
  1983年   15篇
  1982年   9篇
  1981年   8篇
  1980年   16篇
  1979年   7篇
  1978年   7篇
  1977年   3篇
  1976年   4篇
  1975年   3篇
  1974年   2篇
排序方式: 共有623条查询结果,搜索用时 296 毫秒
361.
We study the question of environmental equity via generalized linear modeling for the metropolitan New York City region and ask whether, after accounting for socioeconomic status, particular racial/ethnic populations bear a disproportionate burden of hosting environmentally undesirable sites. Our data consist of population demographics for 2216 census tracts linked to 354 environmentally undesirable facilities, including toxic release inventory sites, hazardous waste treatment, storage, and disposal facilities, and other common urban problem sites such as landfills, incinerators, bus garages and sewage treatment plants. Using generalized linear and additive modeling techniques, we find that racial/ethnic demographics, in particular the Hispanic percentage of a tract's population, are significantly associated with the presence of potentially environmentally adverse sites. This leads us to the conclusion that, over the whole metropolitan New York City area, the Hispanic population is proximate to more sites than other populations. At the same time, we find that both Hispanics and African-Americans are more proximate to these sites in the Bronx and Queens. However, we also find indications that Hispanics and African-Americans are less likely to be proximate to the sites in Manhattan. We establish an empirical relationship that warrants additional study in order to establish the causes for the population distribution and whether a basis for a claim of discrimination exists.  相似文献   
362.
363.
Abstract; Two habitats in Madagascar, secondary, montane heathland and high plateau prairie, are considered artificial, having been created by human-set fires soon after the island was colonized less than 2000 years ago. These prairie and secondary heathland habitats are also thought to be degraded and faunistically depauperate. To test the depauperate fauna hypothesis we measured levels of herpetofaunal (amphibian and reptile) endemicity between primary forest, montane secondary heathland, and high plateau prairie. We found no species endemic to high plateau prairie, but a significant percentage of the montane herpetofauna is restricted to post-fire secondary heathland. These results support the human-origin hypothesis for prairie, but secondary heathland appears to be a natural, post-fire successional stage that leads to a climax of sclero-phyllous forest. This suggests that careful management of montane heathland could establish new dispersal corridors between currently isolated montane forest blocks and, therefore, could offer new opportunities for conservation in Madagascar. Despite widespread burning, the montane heathlands of Madagascar have diverse herpetofaunal communities, demonstrating that these montane communities are not as seriously degraded as previously believed, and that they may be naturally resistant to fire.  相似文献   
364.
365.
366.
资源消耗是与建筑有关的最迫切的问题.要解决这一问题必须制定坚决贩政策.仅有针对具体问题的政策还不够;必须转向“非物质比“.发展中国家在建筑环境政策方面面临着特殊的障碍.发达世界和发展中世界的一些国家正在采取很有前途的措施,但是解决反弹效应等后果将需要超国家的强大努力.  相似文献   
367.
To determine whether fundamental differences exist in the reproductive physiology of breeder and nonbreeder Florida scrub-jays (Aphelocoma coerulescens), we compared plasma levels of testosterone (T) and luteinizing hormone (LH) in males, and estradiol (E2) and LH in females. Although male breeders had higher overall T and larger testes, nonbreeders’ T paralleled that of breeders, and their testes were more than an order of magnitude larger than regressed testes. Breeder and nonbreeder males had equivalent baseline LH, and equivalent changes in LH following a gonadotropin-releasing hormone (cGnRH-I) challenge. The T, LH and GnRH challenge data indicate that nonbreeder males have functional hypothalamo-pituitary-gonadal (HPG) axes. We found no hormonal evidence of inbreeding suppression in males: nonbreeders that did not live with their mothers and those that did had similar T. Male nonbreeders that were exposed to E2-implanted females had higher T than did controls, suggesting that the lack of within-pair stimulation is a key factor in whether an individual delays breeding. Female nonbreeders had E2 titres equal to or higher than breeders and neither basal LH nor LH following GnRH challenge differed by breeding status. Nonbreeders’ ovarian follicles were smaller than breeders’, but were larger than they would be during the non-breeding season. These data suggest that nonbreeders were primed for breeding and were simply waiting for an opportunity or a required stimulus. Female nonbreeders that lived in a territory with an unrelated male breeder had significantly higher E2 than those that remained with their fathers. Similarly, nonbreeders that were captured away from their home territories had elevated E2. However, nonbreeders that lived with their fathers had E2 that was equivalent to breeding females, suggesting that inbreeding avoidance may not be the primary factor leading to delayed breeding in females. Received: 13 June 1995 /Accepted after revision: 27 April 1996  相似文献   
368.
High body mass caused by fat storage during migration is believed to increase a bird's risk of predation by decreasing its ability to escape predators. We demonstrate the negative effect of wing loading (mass/wing area) on escape speed and angle of two migrating species of shorebird. We also show significant differences in escape performance between the species and genders. To help explain these differences, we test two potential proximate causes, wing shape and leg bone length. Wing shape is correlated with differences in escape performance between the species, but we found no correlation of wing shape or leg bone length with gender. Ultimately, greater predation risk due to habitat use or larger body size, for the species and genders respectively, may have resulted in evolution of enhanced escape ability.  相似文献   
369.
The chemical accident at 12:45 AM on December 3, 1984 in Bhopal India had a profound effect on the practice of chemical process safety in the United States. Fearing the possibility of similar events occurring in the United States, the United States Congress convened several hearings and investigations into the causes of the disaster. The inquiries focused both on the state of process safety within the US chemical industry and on the readiness of communities located near chemical operations to respond to sudden and dangerous toxic discharges. Of equal significance were concerns over the safety of workers in chemical plants. This paper reviews the major legislative, academic, and industrial changes initiated in the area of process safety after the event, their influence on saving lives, and on improving living conditions surrounding chemical complexes in the United States.  相似文献   
370.
Surface water methane (CH4) and nitrous oxide (N2O) concentrations and fluxes were investigated in two subtropical coastal embayments (Bramble Bay and Deception Bay, which are part of the greater Moreton Bay, Australia). Measurements were done at 23 stations in seven campaigns covering different seasons during 2010–2012. Water–air fluxes were estimated using the Thin Boundary Layer approach with a combination of wind and currents-based models for the estimation of the gas transfer velocities. The two bays were strong sources of both CH4 and N2O with no significant differences in the degree of saturation of both gases between them during all measurement campaigns. Both CH4 and N2O concentrations had strong temporal but minimal spatial variability in both bays. During the seven seasons, CH4 varied between 500% and 4000% saturation while N2O varied between 128 and 255% in the two bays. Average seasonal CH4 fluxes for the two bays varied between 0.5 ± 0.2 and 6.0 ± 1.5 mg CH4/(m2·day) while N2O varied between 0.4 ± 0.1 and 1.6 ± 0.6 mg N2O/(m2·day). Weighted emissions (t CO2-e) were 63%–90% N2O dominated implying that a reduction in N2O inputs and/or nitrogen availability in the bays may significantly reduce the bays' greenhouse gas (GHG) budget. Emissions data for tropical and subtropical systems is still scarce. This work found subtropical bays to be significant aquatic sources of both CH4 and N2O and puts the estimated fluxes into the global context with measurements done from other climatic regions.  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