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   300篇
  免费   10篇
  国内免费   6篇
安全科学   18篇
废物处理   25篇
环保管理   82篇
综合类   23篇
基础理论   65篇
污染及防治   56篇
评价与监测   31篇
社会与环境   14篇
灾害及防治   2篇
  2023年   4篇
  2022年   2篇
  2021年   2篇
  2019年   9篇
  2018年   9篇
  2017年   4篇
  2016年   6篇
  2015年   13篇
  2014年   7篇
  2013年   41篇
  2012年   12篇
  2011年   10篇
  2010年   14篇
  2009年   11篇
  2008年   14篇
  2007年   13篇
  2006年   15篇
  2005年   14篇
  2004年   3篇
  2003年   9篇
  2002年   4篇
  2001年   6篇
  2000年   3篇
  1999年   6篇
  1998年   5篇
  1997年   3篇
  1996年   6篇
  1995年   2篇
  1994年   3篇
  1993年   2篇
  1991年   6篇
  1990年   2篇
  1988年   5篇
  1987年   6篇
  1986年   4篇
  1985年   5篇
  1984年   2篇
  1983年   3篇
  1982年   2篇
  1981年   5篇
  1980年   3篇
  1979年   2篇
  1977年   4篇
  1975年   2篇
  1973年   2篇
  1972年   2篇
  1970年   1篇
  1968年   1篇
  1959年   1篇
  1957年   1篇
排序方式: 共有316条查询结果,搜索用时 15 毫秒
131.
Residence time effects on phase transformation of silver nanoparticles (AgNPs) (15–50 nm, with and without polyvinylpyrrolidone (PVP) coating) were investigated in reducing soils using experimental geochemistry and synchrotron-based x-ray techniques. After 30 days of anaerobic incubation, a substantial fraction of PVP-coated AgNPs (15 nm) were transformed into Ag2S and or humic acid (HA) complexed Ag(I), whereas only the HA fraction was dominant in uncoated AgNPs (50 nm). Several investigations recently reported that sulfidation of AgNPs to Ag2S was the predominant mechanism controlling the fate of AgNP in soil–water environments. However, this investigation showed each AgNP underwent particle-specific chemical transformations to different end compounds after 30 days. Considering the small contribution of Ag(I) dissolution from all AgNPs (less than 5 %), we concluded that changes in solid-state chemical speciation of sorbed AgNPs was promoted by particle-specific interactions of NPs in soil chemical constituents, suggesting a critical role of soil absorbents in predicting the fate of AgNPs in terrestrial environments.  相似文献   
132.
ABSTRACT: Analyses of soil and water were made in a stretch of shallow ground north of a cypress head in South Florida. The area is covered with water for part of the year, and it flows slowly southward. The soil is primarily peat formed from the local graminid vegetation during its decay. The top layer consists of a blue-green algal mat whose decay products contribute to the peat also. Collections of soil (including the top layer) were made layer by layer and anlyzed for cations and anions and for ion exchange capacity. The latter appears to be high enough in all layers to account for the ion content within the soil and surrounding waters. It probably is a very important buffer system that retards limestone erosion. CEC values ranged from 20 to 190 meg/100 gm dry soil from bedrock to surface.  相似文献   
133.
Summary The influence of resident females on the settling patterns of subsequent females was examined for marsh wrens (Cistothorus palustris). Proportionally more females responded to a playback of a female intruder during the pre-laying stage than during the laying and incubation stages. The strength of the response was also greatest during pre-laying and laying stages (Table 1). Female wrens did not settle randomly with respect to the presence of other females, but rather settled with bachelor males more often than predicted by chance (Table 3). Female settlement within territories was more asynchronous than settlement between territories. An attempt to fit these data to two models of female settlement suggested that prospecting females were not displaced by residents, but rather avoided settling with mated males (Table 3). Females within territories were also more dispersed than predicted by chance, a pattern that may be enforced through aggression on the part of the resident female. Staggered settlement reduces the overlap in nestling stages of harem mates and so may be a strategy to reduce competition for resources at this critical stage.  相似文献   
134.
The overall objective of this project was to determine the cost and impacts of Hg control using sorbent injection into a Compact Hybrid Particulate Collector (COHPAC) at Alabama Power's Gaston Unit 3. This test is part of a program funded by the U.S. Department of Energy's National Energy Technology Laboratory (NETL) to obtain the necessary information to assess the costs of controlling Hg from coal-fired utility plants that do not have scrubbers for SO2 control. The economics will be developed based on various levels of Hg control. Gaston Unit 3 was chosen for testing because COHPAC represents a cost-effective retrofit option for utilities with existing electrostatic precipitators (ESPs). COHPAC is an EPRI-patented concept that places a high air-to-cloth ratio baghouse downstream of an existing ESP to improve overall particulate collection efficiency. Activated carbons were injected upstream of COHPAC and downstream of the ESP to obtain performance and operational data. Results were very encouraging, with up to 90% removal of Hg for short operating periods using powdered activated carbon (PAC). During the long-term tests, an average Hg removal efficiency of 78% was measured. The PAC injection rate for the long-term tests was chosen to maintain COHPAC cleaning frequency at less than 1.5 pulses/bag/hr.  相似文献   
135.
For 30-40 years airborne fluoride, usually in the form of HF or SiF4, was one of the most important and damaging air pollutants affecting forests, crops and natural vegetation. It is much more toxic than most other air pollutants such as O3 or SO2 because injury to the most sensitive species begins when they are exposed to a concentration below 1 ppb (ca. 0.8 microg m(-3)) for a 1- to 3-day period. The long-term threshold concentration is around 0.25-0.30 microg m(-3). Higher concentrations and longer durations of exposure induce much more rapid and extensive injury. However, there is a difference in sensitivity between the most and least sensitive species of around 2-3 orders of magnitude and most species possess a degree of resistance. Dramatic improvements in engineering technology have greatly reduced emissions but because of the high toxicity, cases of vegetation injury are still common, even in developed countries, and cases involving litigation still occur. Therefore there is a continuing need for bioindicators and biomonitoring of fluorides, so this paper reviews the subject, drawing attention to the strengths and limitations of the techniques. Visible symptoms are described and illustrated and tables of relative sensitivity are given and their limitations discussed. Finally, examples of biomonitoring in Europe and the USA are presented.  相似文献   
136.
137.
138.
Provisioning rules in tree swallows   总被引:7,自引:0,他引:7  
Conflict between parents and offspring may result in offspring exaggerating their needs and parents devaluing their begging signals. To determine whether this occurs, it is first necessary to establish the link between need, begging and parental response. The purpose of our study was to examine these relationships in tree swallows (Tachycineta bicolor). Parents preferentially fed nestlings that begged sooner, reached higher and were closer to the front of the nestbox (Fig. 1). Begging intensity of both individuals and entire broods increased with relatively long periods between feeding visits. Within broods, parents responded to increased begging intensity by increasing their feeding rate, although this effect was relatively weak. Large and small nestlings did not differ in their begging behavior and all nestlings, regardless of size, were fed at similar rates. Despite the overall equity in feeding, male parents preferentially fed larger nestlings while female parents fed smaller nestlings. Nestlings did not increase their begging intensity in response to begging by nestmates. Our results suggest that begging is related to need in this species and that parents respond to variation in begging intensity. Received: 4 May 1995/Accepted after revision: 17 December 1995  相似文献   
139.
Water solubilities (SW) determined by the HPLC generator column method are reported for a series of chlorinated dibenzo-p-dioxins (PCDDs) with SW ranging from 0.4 ng/L (ppt) for octa-chlorodibenzo-p-dioxin to 430 ng/L for 1,2,3,7-tetrachlorodibenzo-p-dioxin at 20°C. A correlation is demonstrated between SW and HPLC capacity factors (k′) for these extremely hydrophobic compounds, allowing calculation of SW of PCDDs from k′ and melting point data.  相似文献   
140.
There are important linkages between the health of humans and theenvironment, restoration of degraded lands, and long-term stewardship of public lands, yet most environmental indicators deal only with assessing the physical and biological aspects ofecosystems. In this article, we examine the ratings of perceptionsof several environmental problems for their utility as indicatorsof environmental quality, and examine perceptions of future land use by people interviewed in Santa Fe, New Mexico, near the Department of Energy's (DOE) Los Alamos National Laboratory (LANL). Overall, people with lower incomes rated environmental problems as more severe than others, were more willing to spend federal funds to solve them, and were consistent in their ratingsof severity of environmental problems and their willingness to spend federal funds. Cleaning up LANL and other Department of Energy sites, received the highest rating for expenditure of federal funds. The highest rated future uses for DOE sites were for recreation and for National Environmental Research Parks. People with less education generally gave higher ratings to mostfuture land uses for DOE than did those with more education. However, those with higher education gave higher ratings to nuclear reprocessing, and nuclear material storage. Where there were differences, the people interviewed at Santa Fe rated all environmental problems (except pesticides) as more severe than did those previously interviewed in Albuquerque (located fartherfrom the LANL site), and they were more willing to spend federalfunds on these problems. Ratings for all future land uses did notdiffer between the Santa Fe and Albuquerque respondents. These perception-based indicators show general agreement among peopleliving close and farther away from LANL with respect to cleaningup LANL and the future land uses for the site. These indicators should be considered by regulators, site personnel, and policy makers in future management and land use decisions.  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