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   736篇
  免费   13篇
  国内免费   8篇
安全科学   27篇
废物处理   35篇
环保管理   169篇
综合类   56篇
基础理论   185篇
环境理论   2篇
污染及防治   168篇
评价与监测   71篇
社会与环境   27篇
灾害及防治   17篇
  2023年   5篇
  2022年   5篇
  2021年   8篇
  2020年   12篇
  2019年   5篇
  2018年   17篇
  2017年   16篇
  2016年   20篇
  2015年   11篇
  2014年   29篇
  2013年   57篇
  2012年   30篇
  2011年   46篇
  2010年   40篇
  2009年   31篇
  2008年   49篇
  2007年   41篇
  2006年   44篇
  2005年   32篇
  2004年   20篇
  2003年   30篇
  2002年   22篇
  2001年   11篇
  2000年   13篇
  1999年   8篇
  1998年   14篇
  1997年   10篇
  1996年   12篇
  1995年   11篇
  1994年   15篇
  1993年   10篇
  1992年   4篇
  1991年   12篇
  1990年   3篇
  1989年   6篇
  1988年   3篇
  1987年   5篇
  1985年   7篇
  1984年   6篇
  1983年   7篇
  1982年   8篇
  1980年   3篇
  1979年   5篇
  1978年   3篇
  1972年   1篇
  1971年   1篇
  1969年   1篇
  1967年   1篇
  1966年   1篇
  1964年   1篇
排序方式: 共有757条查询结果,搜索用时 15 毫秒
1.
2.
The potential for metabolic fingerprinting via Fourier-transform infrared (FT-IR) spectroscopy to provide a novel approach for the detection of plant biochemical responses to N deposition is examined. An example of spectral analysis using shoot samples taken from an open top chamber (OTC) experiment simulating wet ammonium deposition is given. Sample preparation involved oven drying and homogenisation via mill grinding. Slurries of a consistent dilution were then prepared prior to FT-IR analysis. Spectra from control, 8 and 16 kg N ha–1 yr–1 treatments were then subjected to cross-validated discriminant function analysis. Ordination diagrams showed clear separation between the three N treatments examined. The potential for using Calluna vulgaris (L.) Hull as a bioindicator of N deposition is further evident from these results. The results also clearly demonstrate the power of FT-IR in discriminating between subtle phenotypic alterations in overall plant biochemistry as affected by ammonium pollution.  相似文献   
3.
The government of Canada ratified the Kyoto Protocol on 17 December 2002, but over 100 Canadian municipalities had joined the International Council for Local Environmental Intitatives' (ICLEI) Cities for Climate Protection (CCP) campaign up to a decade earlier. A low-cost home energy rating system (HERS) evaluation and individualized energy plan was provided to 420 households in Kitchener, Ontario, from September 2000 to August 2001. To assess the impact of the energy efficiency program, natural gas consumption in the year prior to the evaluation was compared with that in the year following. Overall, a 5% reduction was achieved, but individual responses varied widely. Situational and psychological factors were evaluated for three groups of households: the conservers, the consumers and the steady middle group. Conservers (30% of households) had higher initial energy consumption levels and achieved two-thirds of the potential savings identified by the energy evaluation. Consumers (12% of households) had higher ownership rates of high-efficiency furnaces and water heaters and demonstrated the rebound effect of increased demand for energy services following the evaluation. Low-income groups were the most likely to behave as conservers (42%) while high-income groups were the least likely to be conservers (13%) and the most likely to be consumers. Local programs need to be inclusive of all income groups to increase participation and implementation rates by systematically reducing barriers (financial, knowledge, trust) or increasing incentives (financial, regulatory or social) if the desired goal (e.g. Kyoto target) is to be achieved.  相似文献   
4.
A marked decline in the contribution by Marovo Lagoon to the annual total bêche-de-mer production of the Solomon Islands from 58% in 1989 to 17% in 2003 prompted investigation of their current biomass and diversity. We also assessed changes to critical ecological services and the prospects for population recovery following a fisheries closure. Day time and nocturnal transects revealed a mean abundance of 32.4 (SD = 5.3) low value species per ha (e.g. Holothuria atra, H. edulis, H. coluber and Thelenota anax) and 15.2 (SD = 2.7) high value species per ha (e.g. H. fuscogilva, Actinopyga lecanora, Stichopus hermanni and Thelenota ananas). Following a 17 month closure of the fishery (2005–2007), the abundance of bêche-de-mer was reported by local fisherman to have increased; however, no scientific studies were conducted that can substantiate this community held belief. The current study aimed to document the impact of re-opening the fishery in 2007 and documented a decline in high value species of 9% over a 5 month period following the opening of the fishery, while low value species continued to increase in abundance by 11%, over the same period based on nocturnal surveys. Continued observation of the recovery, post closure, and any subsequent harvest in Marovo will be required to properly understand population dynamics and provide a sustainable harvest plan for bêche-de-mer in the future.  相似文献   
5.
6.
7.
The local food movement has been touted by some as a profoundly effective way to make our food system become more healthy, just, and sustainable. Others have criticized the movement as being less a challenge to the status quo and more an easily co-opted support offering just another set of choices for affluent consumers. In this paper, we analyze three distinct sub-movements within the local food movement, the individual-focused sub-movement, the systems-focused sub-movement, and the community-focused sub-movement. These movements can be combined within any particular campaign or within the goals of any particular organization or individual activist, but they are nevertheless quite different from each other, and come out of different conceptualizations of what food, people, and locality are. We argue that most of the critiques leveled against local food are actually directed against the individual-focused sub-movement, which is most compatible with the current industrial food system, and perhaps not surprisingly receives the most mainstream attention. Further, we argue that while each movement has its own strengths and weaknesses, it is the community-focused sub-movement that has the most potential to radically transform the global food system.  相似文献   
8.
9.
Southeast Asian countries are confronting climate variability, challenging agricultural sustainability and rural livelihoods. However, little research effort has been devoted to exploring how farmers in those countries perceive climate variability and how the perceptions link to adaptive responses. This paper deploys information from three focus group discussions with 30 male farmers; and six in-depth interviews with one female and five male agricultural officers in the Mekong Delta, Vietnam. Recorded 34-year meteorological data in the delta from 1978 to 2011 is also incorporated to demonstrate the actual climate variability of the region. We find that farmers are becoming increasingly conscious of local climate variability issues. However, they have limited understanding of the importance of adaptation to their livelihoods. They also have limited knowledge of where and who to contact for appropriate climate change adaptation information. No opinions about the link between global warming and local climate variability and change were observed. Casual observation via public media and personal experience dominated farmers’ sources of information. Barriers to farmers’ adaptation are not exclusively restricted to socio-economic factors and resource constraints; e.g. land tenure, technical knowledge, market, social relationship, credit, information, health care, and demographics. Maladaptation, habit, and the perception of the importance of climate variability and adaptation are found as additional constraints. Observed differences in farmers’ and agricultural officers’ perspectives regarding barriers to farmers’ adaptation suggest important policy implications.  相似文献   
10.
Ammonia (NH3) fluxes from waste treatment lagoons and barns at two conventional swine farms in eastern North Carolina were measured. The waste treatment lagoon data were analyzed to elucidate the temporal (seasonal and diurnal) variability and to derive regression relationships between NH3 flux and lagoon temperature, pH and ammonium content of the lagoon, and the most relevant meteorological parameters. NH3 fluxes were measured at various sampling locations on the lagoons by a flowthrough dynamic chamber system interfaced to an environmentally controlled mobile laboratory. Two sets of open-path Fourier transform infrared (FTIR) spectrometers were also used to measure NH3 concentrations for estimating NH3 emissions from the animal housing units (barns) at the lagoon and spray technology (LST) sites. Two different types of ventilation systems were used at the two farms. Moore farm used fan ventilation, and Stokes farm used natural ventilation. The early fall and winter season intensive measurement campaigns were conducted during September 9 to October 11, 2002 (lagoon temperature ranged from 21.2 to 33.6 degrees C) and January 6 to February 2, 2003 (lagoon temperature ranged from 1.7 to 12 degrees C), respectively. Significant differences in seasonal NH3 fluxes from the waste treatment lagoons were found at both farms. Typical diurnal variation of NH3 flux with its maximum value in the afternoon was observed during both experimental periods. Exponentially increasing flux with increasing surface lagoon temperature was observed, and a linear regression relationship between logarithm of NH3 flux and lagoon surface temperature (T1) was obtained. Correlations between lagoon NH3 flux and chemical parameters, such as pH, total Kjeldahl nitrogen (TKN), and total ammoniacal nitrogen (TAN) were found to be statistically insignificant or weak. In addition to lagoon surface temperature, the difference (D) between air temperature and the lagoon surface temperature was also found to influence the NH3 flux, especially when D > 0 (i.e., air hotter than lagoon). This hot-air effect is included in the statistical-observational model obtained in this study, which was used further in the companion study (Part II), to compare the emissions from potential environmental superior technologies to evaluate the effectiveness of each technology.  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