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   1868篇
  免费   193篇
  国内免费   40篇
安全科学   150篇
废物处理   163篇
环保管理   382篇
综合类   106篇
基础理论   496篇
环境理论   1篇
污染及防治   504篇
评价与监测   173篇
社会与环境   60篇
灾害及防治   66篇
  2023年   32篇
  2022年   148篇
  2021年   114篇
  2020年   51篇
  2019年   80篇
  2018年   118篇
  2017年   109篇
  2016年   126篇
  2015年   80篇
  2014年   101篇
  2013年   354篇
  2012年   85篇
  2011年   102篇
  2010年   97篇
  2009年   67篇
  2008年   63篇
  2007年   50篇
  2006年   48篇
  2005年   33篇
  2004年   34篇
  2003年   34篇
  2002年   36篇
  2001年   28篇
  2000年   30篇
  1999年   19篇
  1998年   4篇
  1997年   6篇
  1996年   1篇
  1995年   8篇
  1994年   9篇
  1993年   2篇
  1992年   3篇
  1991年   3篇
  1990年   3篇
  1989年   1篇
  1988年   2篇
  1986年   1篇
  1985年   3篇
  1984年   1篇
  1983年   2篇
  1981年   1篇
  1979年   3篇
  1977年   2篇
  1976年   1篇
  1974年   1篇
  1970年   1篇
  1966年   1篇
  1964年   1篇
  1963年   1篇
  1959年   1篇
排序方式: 共有2101条查询结果,搜索用时 31 毫秒
991.
This study investigated attitudes and subjective norms related to workplace diversity initiatives and intentions to engage in diversity‐related behaviors in a sample of 852 public service employees. Participants completed a survey measuring behavioral intentions, attitudes, belief‐based norms, ethnic identity achievement, and demographic characteristics. Comparisons were made between people of color and Whites as well as between those with high and low ethnic identity achievement. Results showed a triple interaction among supervisor race, employee race, and employee ethnic identity achievement. Specifically, among people of color with high ethnic identity achievement, having a supervisor of color was more strongly associated with positive views of subjective norms toward inclusive behavior, understanding others, and treating others with respect than among people of color with low ethnic identity achievement. Implications of these findings and directions for future research are discussed. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
992.
993.
Abstract: A method was developed to characterize ecological integrity of riparian sites based on the abundance of hydric species. This wetland index can be calculated with species data, or with community type data as performed here. Classified riparian community types were used to describe vegetation at 14 livestock exclosures and adjacent grazed areas. Community type wetland index values were generated and used to calculate site wetland index values. It was hypothesized that removal of livestock would result in higher wetland index values because of release from herbivory and decreased physical disturbance of vegetation, streambanks, and soil. The wetland index for exclosures was about 12% higher than grazed sites; differences were statistically significant (p < 0.01) based on paired t‐tests. The increase in hydric vegetation after livestock exclusion may have contributed to the greater bank stability (p = 0.002) and smaller width‐to‐depth ratio (p = 0.005) in exclosures. Challenges were encountered in using community types to describe and compare site vegetation, which could be avoided with species data collection. The wetland index can be a tool to monitor sites over time, compare sites with similar environments, or compare sites for which environmental differences can be accounted.  相似文献   
994.
A pollution transport problem is formulated in a limited area. As the pollution sources we take emissions from industrial plants. Physically and mathematically suitable conditions are prescribed on the open boundaries. We show that the problem (as well as its adjoint) is well posed in the sense that a weak solution exists, is unique and depends continuously on its data. Direct and adjoint estimates of the average pollution concentration in an ecologically important zone are given, and the sensitivity of these estimates to perturbations in model parameters is analyzed.  相似文献   
995.
Researchers have been challenged to specify the processes that quality improvement (QI) practices could be expected to generate and to explain how they might contribute to organizational effectiveness. This research article meets that challenge through a study of 97 teams in the health care field. The authors developed a ‘Quality Improvement Practices Index’ and showed that QI practices could be differentiated from traditional team‐level variables, and that such practices affect both directly and indirectly (through team‐level variables) team effectiveness. Two models were tested using structural equation modelling. It was found that the perceptions of the impact of QI practices on team effectiveness varied depending on who was assessing the team's performance—members of the team or managers who were external to the team but responsible for the team's performance. The authors discuss the implications of these results both for researchers and practitioners. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
996.
Sea turtles migrate between feeding and nesting areas that are often geographically separated by hundreds or thousands of kilometers. Observations of their aggregations at sea and at nesting beaches have led to the hypothesis that sea turtles migrate in socially structured groups. While this migratory strategy is common to many marine vertebrates, socially facilitated behavior is not well documented in testudines. In 1990 and 1991, we attached satellite transmitters to olive ridleys (Lepidochelys olivacea Eschscholtz) found ovipositing together during a mass nesting at Nancite Beach, Costa Rica, to determine whether they migrate independently or in groups after they leave the nesting beach. Results showed that the turtles were not spatially associated during the internesting period, were capable of re-establishing themselves as a group during a subsequent nesting emergence, and were not spatially associated during their postnesting migrations to oceanic feeding areas. We suggested that what appear to be socially structured groups of L. olivacea are in fact individual turtles simultaneously using the same habitat.  相似文献   
997.
Municipal solid waste (MSW) quantity and composition analysis is fundamental for the planning of municipal waste management services. The purpose of this paper is to report the results and experiences of sampling household waste at the source of generation in Gaborone, Botswana. The average generation rate, in kg capita(-1) day(-1), and percentages of various components of waste in Gaborone were determined using a statistically designed household sampling survey. The survey covered 47 households with different socio-economic characteristics over 21 days with 893 samples obtained. The results showed that the average waste generation rate for Gaborone was 0.33 kg capita(-1) day(-1). Contrary to common belief, the waste generation rate measured as in weight units was found not be directly related to household income. However, the packaging fractions of plastic and paper measured as volume had a direct relationship with household income. Across all income groups, the putrescible waste fraction constituted the highest proportion of the waste stream at approximately 68%. The main general conclusion is on the importance of practical considerations. As much as statistically designed sampling procedures provide a useful means of estimating the quantity and composition of household waste at source of generation, there are some practical issues that should be carefully considered during sampling to improve the accuracy and relevance of the results.  相似文献   
998.
In Scotland, land use planning decisions have been aided by a series of National Planning Guidelines published over a period of nearly 20 years. The Guidelines represent a distinctive contribution to planning practice and have enabled the Scottish Office to inform local authorities of governmental policy on key land use issues. The Guidelines have been accompanied by Land Use Summary Sheets, providing assessments of specific land resources, and Circulars setting down ministerial policy. These instruments have attracted considerable interest outwith Scotland and their future development is also of wider significance. Current proposals seek to change these arrangements and, in particular, to replace the Guidelines with National Planning Policy Guidelines. The effects of the proposed changes are reviewed and discussed.  相似文献   
999.
在黄土高原沟壑区,通过16S rRNA基因片段和ITS高通量测序,研究沟道泥沙中细菌和真菌群落在上-中-下游的变化特征.结果表明:与沟头相比,把口站的细菌群落中拟杆菌门(Bacteroidetes)与厚壁菌门(Firmicutes)的相对丰度分别增加6.6%和10.5%,而变形菌门(Proteobacteria)的相对丰度降低15.1%;真菌群落中担子菌门(Basidiomycota)的相对丰度增加7.7%,而子囊菌门(Ascomycota)降低30.2%;泥沙中黏粒含量与细菌丰富度(Chao1指数)和多样性(Shannon指数)之间显著负相关(P<0.05),与真菌的丰富度和多样性无显著相关性;细菌和真菌群落多样性和丰富度的空间差异与SOC、Olsen-P的变化有关(P<0.05).因此,泥沙中颗粒组成物和养分含量可能是影响沟道微生物群落变化的主要因素.  相似文献   
1000.
Samples of atmospheric particulate matter obtained from representative areas of the city of Baghdad were collected on glass fiber filters using a high-volume sampler. Atomic absorption techniques were used to analyze the total suspended particulates (TSP) for the following trace metals; Fe, Cu, Zn, Pb, Mn, Cr, Cd, Co, and Hg. Sulfates were measured by turbidemetric method. Ion-selective electrodes was used for chloride analysis. It is concluded that the major components of TSP in the ambient air of Baghdad consist of mineral dust. Pb and Cd gave high enrichment factor values, which implies enrichment of these two metals from anthropogenic sources. High enrichment factors were also obtained for Zn and Cu. It is also concluded that in this arid area, the black smoke reflectance method is not suitable for measuring total suspended matter gravimetrically.  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