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   226篇
  免费   3篇
  国内免费   3篇
安全科学   14篇
废物处理   5篇
环保管理   82篇
综合类   10篇
基础理论   49篇
污染及防治   40篇
评价与监测   14篇
社会与环境   11篇
灾害及防治   7篇
  2022年   2篇
  2021年   1篇
  2019年   3篇
  2018年   4篇
  2017年   2篇
  2016年   9篇
  2015年   7篇
  2014年   3篇
  2013年   24篇
  2012年   9篇
  2011年   5篇
  2010年   7篇
  2009年   7篇
  2008年   11篇
  2007年   8篇
  2006年   13篇
  2005年   9篇
  2004年   6篇
  2003年   7篇
  2002年   12篇
  2001年   5篇
  2000年   1篇
  1999年   5篇
  1998年   3篇
  1997年   2篇
  1996年   7篇
  1995年   5篇
  1994年   2篇
  1993年   7篇
  1992年   4篇
  1991年   3篇
  1990年   3篇
  1989年   1篇
  1988年   3篇
  1987年   2篇
  1986年   4篇
  1985年   3篇
  1984年   4篇
  1982年   3篇
  1981年   2篇
  1980年   1篇
  1979年   3篇
  1978年   1篇
  1976年   1篇
  1975年   1篇
  1974年   2篇
  1971年   1篇
  1968年   1篇
  1931年   1篇
  1924年   1篇
排序方式: 共有232条查询结果,搜索用时 390 毫秒
181.
Regional Environmental Change - We develop and apply a synthetic framework for understanding potential adaptations to climate change in the Canadian agriculture sector through a case study of...  相似文献   
182.
It is unclear why some firms suffer greater negative consequences than others following a product recall. To shed light on this question, we extend attribution theory to the firm level to explore how consumers engage in an attributional process following product recalls that shapes their responses to firms. Integrating attribution theory and the demand side theoretical perspective, we assert that consumer judgments of responsibility toward manufacturers are shaped by causal data regarding the locus of causality (i.e., manufacturer or supplier) and controllability (i.e., prior knowledge or awareness) of a recalled product's potential for harm. We then examine the impact of product recall characteristics on judgments of responsibility and firm‐level outcomes using an experimental test involving responses from 320 subjects. Our findings suggest that judgments of responsibility are attributed to the manufacturing firm more when consumers are given causal information indicating that the firm is the source of, or is aware of, a product's defects. The results also indicate that judgments of responsibility can have costly firm‐level consequences in the form of reputational damage, diminished consumer purchase intentions, and increased legal damage recommendations. We discuss theoretical contributions, practical implications, and opportunities for further research.  相似文献   
183.
Fish body size, a key driver of many aspects of fish population biology and ecology, is affected by fisheries that deplete the largest individuals. Rockfish (genus Sebastes) are a diverse group that has been heavily fished on the U.S. West Coast in recent decades. We examined trawl survey data from 1980 to 2001 to determine spatial and temporal trends in body size and density of 16 shelf rockfish species, including six that are considered overfished. Mean individual mass and maximum observed mass declined in the majority of species in one or more zoogeographic regions between central California and Washington. Density changes were far more variable in time and space, but in all regions, density declines were most often associated with large-bodied rockfish. We next estimated the impact of size and density changes on energy consumption and fecundity in a five-species rockfish assemblage that includes bocaccio (S. paucispinis), a large-bodied, overfished species. Indexes of both consumption and fecundity by the assemblage increased in the southern portion of the study area between 1980 and 2001 but decreased in the northern portion. Allocation of energy and reproductive potential within the assemblage shifted dramatically: relative to bocaccio, total energy consumption and fecundity indexes for the other four species increased by orders of magnitude from 1980 to 2001. These changes in community structure may affect the ability of bocaccio and other large rockfish species to recover from overfishing, especially in light of long-term declines in zooplankton production that may also be affecting rockfish size and production. Addressing these issues may require a regional, multispecies management approach.  相似文献   
184.
Gametogenesis was studied histologically in the deep-sea species Pourtalesia jeffreysi (Wyville Thomson), P. miranda (A. Agassiz) and Echinosigra phiale (Wyville Thomson) collected during 1973–1983 from various positions at depths of 1 040 to 2 921 m in the Rockall Trough. The gonads are small and no synchrony in terms of the stage of gametogenic development was evident in females of the latter two species collected at different times of the year, indicating nonseasonal breeding. Males appear to be ripe at all times of the year. Follicle cells were well developed around the developing oocytes. Both the size range of the yolky ripe eggs (173 to 357 m diam) and potential fecundity within the range of 1 000 to 4 000 oocytes per individual, are indicative of an abbreviated, indirect, lecithotrophic mode of development occurring in all three species. Pourtalesiid postlarvae occurred also in fine-meshed trawl hauls, and their morphology is described. It was not possible to distinguish between P. miranda and E. phiale at sizes <3 mm in length.  相似文献   
185.
An earlier study showed large changes in ovarian phosphoprotein, a characteristic component of vertebrate yolk, during post-vitellogenic meiotic maturation (ripening) of ovaries of teleosts with pelagic eggs. Here, the study of four phosphorus-containing ovarian fractions is extended to other teleost families with pelagic eggs and to species with demersal eggs. Fishes were caught in the sea and lakes of western Scotland between 1982 and 1984. In the codGadus morhua, spratSprattus sprattus, dragonetCallionymus lyra, Norway poutTrisopterus esmarkii, saithePollachius virens, lingMolva molva and flounderPlatichthys flesus, all of which spawn pelagic eggs, the massive water influx during ripening which renders the eggs buoyant was accompanied by large changes in yolk phosphoprotein which were apparent as decrease or disappearance of protein phosphorus as conventionally determined. During ripening of the demersal eggs of the herringClupea harengus, both the water uptake and the decrease in protein phosphorus were less pronounced. In the three-spined sticklebackGasterosteus aculeatus, sea sticklebackSpinachia spinachia, sand gobyPomatoschistus minutus and perchPerca fluviatilis, little or no changes in water content or protein phosphorus both usually increased in species with pronounced water uptake and decreased in species with little or no water uptake. Lipid phosphorus showed little change in all species examined except herring, in which it increased. It is concluded that the characteristic changes in phosphoprotein and other phosphorus-containing fractions are most pronounced in species with pelagic eggs exhibiting massive water uptake on ripening, but are found to a lesser extent in species with demersal eggs in which considerable water uptake accompanies ripening.  相似文献   
186.
An eighteen-year-old clone of Sitka spruce (Picea sitchensis (Bong.) Carr) growing in the field was used to evaluate the whole tree response of 'mature' Sitka spruce to acid mist treatment. The mist, an equimolar mixture of H(2)SO(4) and NH(4)NO(3) at pH 2.5 with or without particles (soda glass ballotini < 20 microm diameter), was applied twice weekly (equivalent to 4 mm precipitation week(-1)) throughout the growing season, May-November 1990-1992. The annual dose of S, N, H applied as mist (at 51, 48 and 3.3 kg ha(-1), respectively) was 2.5 times that measured in the Scottish uplands. Throughout the experiment there was no evidence of visible injury symptoms, yet there was a highly significant reduction (p < 0.02) in the stem-area increment relative to the stem area at the start, measured using vernier dendrometer bands. There was no significant difference between the (acid mist + particle) and the acid mist only treatments. The mean relative stem-area increment over two complete growing seasons (1991-1992) was 65% for control trees, but only 53% for acid-misted trees.  相似文献   
187.
The influence of physicochemical characteristics and motility on bacterial transport in groundwater were examined in flow-through columns. Four strains of bacteria isolated from a crystalline rock groundwater system were investigated, with carboxylate-modified and amidine-modified latex microspheres and bromide as reference tracers. The bacterial isolates included a gram-positive rod (ML1), a gram-negative motile rod (ML2), a nonmotile mutant of ML2 (ML2m), and a gram-positive coccoid (ML3). Experiments were repeated at two flow velocities, in a glass column packed with glass beads, and in another packed with iron-oxyhydroxide coated glass beads. Bacteria breakthrough curves were interpreted using a transport equation that incorporates a sorption model from microscopic observation of bacterial deposition in flow-cell experiments. The model predicts that bacterial desorption rate will decrease exponentially with the amount of time the cell is attached to the solid surface. Desorption kinetics appeared to influence transport at the lower flow rate, but were not discernable at the higher flow rate. Iron-oxyhydroxide coatings had a lower-than-expected effect on bacterial breakthrough and no effect on the microsphere recovery in the column experiments. Cell wall type and shape also had minor effects on breakthrough. Motility tended to increase the adsorption rate, and decrease the desorption rate. The transport model predicts that at field scale, desorption rate kinetics may be important to the prediction of bacteria transport rates.  相似文献   
188.
189.
The ability of Section 404 of the Clean Water Act to act as an effective, efficient, and equitable land-use planning tool was assessed through a survey of Section 404 permits in Wisconsin. In a six-month period of permitting, the 404 program reduced wetland losses in the state by 15%. Several factors were examined that may affect permit decisions; these factors are water dependency, alternatives, project type, wetland type, and public or agency comments. Only the water dependency of the project had a statistically significant effect on permit decisions, although development projects that were perceived to provide public good were more likely to be permitted. Environmental impacts of a proposed fill project were not adequately assessed in any of the permit decisions. Because of the way Section 404 is interpreted and administered by the US Army Corps of Engineers, increasing net benefits and achieving an equitable distribution of those benefits is difficult. The corps does not perform any functional evaluations of wetlands nor do they attempt to measure economic value and environmental impacts. In addition, the 404 review process is, in effect, inaccessible to the public. The de facto interpretations of the Section 404 regulations and a lack of program funding and trained personnel all contribute to the program's ineffectiveness.  相似文献   
190.
Summary This paper seeks to set the appropriate standards for monitoring and enforcement for the management of industrial wastes and effluents in developing countries. It applies these environmental protection measures to the proposed Samutprakam Province improvement programme in Thailand.Dr Harvey F. Ludwig is a regular contributor toThe Environmentalist (see, for instance, Ludwig, 1990; Ludwig and Browder, 1992). He is Chairman of Seatec International Consulting Engineers where Sow Kim Leng is a consulting engineer. Wanida Srichai is based at the World Environment Center, Thailand Office, Bangkok, Thailand.  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