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   171篇
  免费   7篇
  国内免费   1篇
安全科学   16篇
废物处理   11篇
环保管理   41篇
综合类   35篇
基础理论   26篇
污染及防治   41篇
评价与监测   6篇
社会与环境   2篇
灾害及防治   1篇
  2023年   4篇
  2022年   2篇
  2020年   4篇
  2019年   4篇
  2018年   7篇
  2017年   3篇
  2016年   7篇
  2015年   7篇
  2014年   2篇
  2013年   15篇
  2012年   9篇
  2011年   6篇
  2010年   8篇
  2009年   9篇
  2008年   10篇
  2007年   6篇
  2006年   10篇
  2005年   2篇
  2004年   2篇
  2003年   6篇
  2002年   3篇
  1997年   4篇
  1996年   3篇
  1994年   2篇
  1993年   1篇
  1992年   1篇
  1991年   1篇
  1990年   1篇
  1989年   2篇
  1988年   1篇
  1987年   1篇
  1984年   2篇
  1982年   1篇
  1981年   1篇
  1976年   2篇
  1975年   4篇
  1974年   2篇
  1973年   1篇
  1968年   1篇
  1965年   1篇
  1962年   1篇
  1961年   1篇
  1959年   2篇
  1958年   4篇
  1957年   1篇
  1955年   3篇
  1954年   1篇
  1950年   2篇
  1947年   1篇
  1940年   1篇
排序方式: 共有179条查询结果,搜索用时 15 毫秒
91.
Understanding the environmental contributors to population structure is of paramount importance for conservation in urbanized environments. We used spatially explicit models to determine genetic population structure under current and future environmental conditions across a highly fragmented, human‐dominated environment in Southern California to assess the effects of natural ecological variation and urbanization. We focused on 7 common species with diverse habitat requirements, home‐range sizes, and dispersal abilities. We quantified the relative roles of potential barriers, including natural environmental characteristics and an anthropogenic barrier created by a major highway, in shaping genetic variation. The ability to predict genetic variation in our models differed among species: 11–81% of intraspecific genetic variation was explained by environmental variables. Although an anthropogenically induced barrier (a major highway) severely restricted gene flow and movement at broad scales for some species, genetic variation seemed to be primarily driven by natural environmental heterogeneity at a local level. Our results show how assessing environmentally associated variation for multiple species under current and future climate conditions can help identify priority regions for maximizing population persistence under environmental change in urbanized regions.  相似文献   
92.
93.
Collection of atmospheric H2O2 was performed by a cold trap method using dry ice-acetone as the refrigerant. The air was drawn by a pump into a glass gas trap immersed in the dry ice-acetone slush in a dewar flask at a flow rate of 2.5 l min-1 for approximately 2 h. Collection efficiency was > 99% and negligible interferences by O3, SO2 or organic matter with the collected H2O2 in the trap were observed. This method was compared with the air impinger bubbling method which has been previously described (Kok et al., 1978a, b, Envir. Sci. Technol. 12, 1072-1080). The measured total peroxide (H2O2 + organic peroxide) values in a series of aim samples collected by the impinger bubbling method (0.06-3.7 ppb) were always higher than those obtained by the cold trap method (0.02-1.2 ppb). Laboratory experiments suggest that the difference in values between the two methods probably results from the aqueous phase generation of H2O2 and organic peroxide in the impinger solution by a reaction of atmospheric O3 with olefinic and aromatic compounds. If these O3-organic compound reactions which occur in the impinger also occur in aqueous droplets in the atmosphere, the process could be very important for aqueous phase generation of H2O2 in clouds and rainwater.  相似文献   
94.
95.
Understanding the role of negative affectivity (NA) in relations between job stressors and resultant strains has been a major source of research interest in the organizational literature for almost two decades. In this study, we propose a contingency approach, whereby the role of NA depends on the nature of the strain construct under investigation. Specifically, we predicted that perceived job stressors would fully mediate the relationship between NA and turnover intentions, while job stressors would only partially mediate the relationship between NA and job and life satisfaction, and job stressors would be unrelated to depression once NA was taken into account. The relative fit of these four models is tested utilizing data from two divergent samples (sales representatives and managers) employing both self‐ and informant reports of strain measures where feasible. Hypotheses regarding the specified nature of the NA → stressor → strain relationship generally were supported and replicated across samples. In addition, an alternate model specifying that NA moderates the relationship between stressors and strains was not supported for any strain variable. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
96.
The influence of carbon, nitrogen, and phosphate source, along with concentration, was determined for effect on the weight average molecular weight, molecular weight distribution, and yield of pullulan produced byAureobasidium pullulans NRRL-Y 6220. Batch systems, scale-up batch, and continuous fermentations of 1 L and 10 L were also evaluated as were processing variables, including solvents, and extraction conditions. Products with weight average molecular weight from 1.0 × 105 to 4.0 × 106 were produced in 100-g quantities by varying fermentation conditions such as constituents of the culture medium, pH, and length of incubation. Three sets of culture conditions were defined for the formation of low (<5.0×105), medium (1.0–2.0×106), and high (>2.0×106) weight average molecular weight polymer. These defined molecular weight fractions of pullulan were used in further studies in producing films and fibers.  相似文献   
97.
Discounting is traditionally interpreted as the technique for comparing the values of costs and benefits which occur at different points in time. It endeavors to incorporate how humans trade off values to be received in the future versus value received immediately into economic analysis. Interpreted as such, discounting neglects important spatial influences on how values are compared, thereby hindering cost-benefit analyses of climate change adaptation. In this article, we present new theory on space-time discounting and use it to analyze aspects of how humans adapt to climate change. Three climate change adaptation cases are considered. First, analysis of crop indemnity payments to farmers shows that failure to discount across space and time yields inaccurate evaluations of adaptation projects. Second, adaptation efforts of the Commonwealth of Nations show irregular patterns of international cooperation that suggest spatial discounting of adaptation which are not found in temporal discounting. Third, the nexus between climate change, migration, and conflict shows how various forms of space-time discounting can influence whether climate change and migration will lead to conflict. Collectively, these cases demonstrate the analytical power of the space-time discounting theory and also show how the complexity of climate change adaptation can challenge and strengthen this theory. Finally, this article’s analysis demonstrates that proper discounting must include space as well as time.  相似文献   
98.
Overwhelming evidence demonstrates the benefits of positive affect for various life and work outcomes. However, the relevant organizational research almost exclusively has focused on general positive affect, thereby implying that all positive affect has consistent and equal relationships with other work variables. The purposes of this theoretical paper are to review and highlight research from basic psychology demonstrating the unique nature and correlates of specific positive emotions and to translate those ideas and findings into the organizational context. Specifically, we discuss three discrete positive emotions—pride, interest, and gratitude—and offer propositions regarding their differential effects on relevant workplace outcomes and regarding the differential antecedents of them. Our hope is that this paper stimulates future research on this topic, and we offer specific research strategies and ideas to facilitate those endeavors. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
99.
The inheritance and functional roles of quantitative traits are central concerns of evolutionary ecology. We report two sets of experiments that investigated the heritability and reproductive consequences of body size phenotypes in a globally distributed lepidopteran frugivore, Cydia pomonella (L.). In our first set of experiments, we tested the hypotheses that (1) body size is heritable and (2) parental body size mediates egg production and offspring survival. Midparent–offspring regression analyses revealed that body mass is highly heritable for females and moderately heritable for males. The contribution of fathers to estimates of additive genetic variance was slightly greater than for mothers. Egg production increased with mean parental size, but offspring survival rates were equivalent. Based on this result, we tested two additional hypotheses in a second set of experiments: (3) male size moderates female egg production and egg fertility and (4) egg production, egg fertility, and offspring survival rate are influenced by female mating opportunities. Females paired with large males produced more eggs and a higher proportion of fertile eggs than females paired with small males. Females with multiple mating opportunities produced more fertile eggs than females paired with a single male. However, egg production and offspring survival rates were unaffected by the number of mating opportunities. Our experiments demonstrate that body mass is heritable in C. pomonella and that size phenotypes may mediate fecundity but not fitness. We conclude that male size can influence egg production and fertility, but female mate choice also plays a role in determining egg fertility.  相似文献   
100.
Despite compelling reasons to involve nonscientists in the production of ecological knowledge, cultural and institutional factors often dis-incentivize engagement between scientists and nonscientists. This paper details our efforts to develop a biweekly newspaper column to increase communication between ecological scientists, social scientists, and the communities within which they work. Addressing community-generated topics and written by a collective of social and natural scientists, the column is meant to foster public dialog about socio-environmental issues and to lay the groundwork for the coproduction of environmental knowledge. Our collective approach to writing addresses some major barriers to public engagement by scientists, but the need to insert ourselves as intermediaries limits these gains. Overall, our efforts at environmental communication praxis have not generated significant public debate, but they have supported future coproduction by making scientists a more visible presence in the community and providing easy pathways for them to begin engaging the public. Finally, this research highlights an underappreciated barrier to public engagement: scientists are not merely disconnected from the public, but also connected in ways that may be functional for their research. Many field scientists, for example, seek out neutral and narrowly defined connections that permit research access but are largely incompatible with efforts to address controversial issues of environmental governance.  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