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   448篇
  免费   4篇
  国内免费   11篇
安全科学   26篇
废物处理   17篇
环保管理   94篇
综合类   51篇
基础理论   81篇
污染及防治   123篇
评价与监测   42篇
社会与环境   26篇
灾害及防治   3篇
  2023年   5篇
  2022年   12篇
  2021年   15篇
  2020年   4篇
  2018年   10篇
  2017年   9篇
  2016年   15篇
  2015年   11篇
  2014年   14篇
  2013年   48篇
  2012年   10篇
  2011年   24篇
  2010年   19篇
  2009年   16篇
  2008年   20篇
  2007年   22篇
  2006年   19篇
  2005年   11篇
  2004年   16篇
  2003年   17篇
  2002年   17篇
  2001年   7篇
  2000年   5篇
  1999年   4篇
  1998年   9篇
  1997年   10篇
  1996年   7篇
  1995年   3篇
  1993年   8篇
  1992年   6篇
  1991年   5篇
  1990年   4篇
  1989年   3篇
  1987年   3篇
  1986年   2篇
  1985年   5篇
  1984年   4篇
  1983年   2篇
  1982年   4篇
  1981年   2篇
  1979年   4篇
  1978年   2篇
  1975年   2篇
  1973年   2篇
  1964年   2篇
  1963年   2篇
  1958年   2篇
  1957年   2篇
  1956年   3篇
  1955年   3篇
排序方式: 共有463条查询结果,搜索用时 640 毫秒
291.
Airborne particulate matter has been collected from within,and proximal to, an opencast coal mine in south Wales. Thiswork forms the first part of a three year project to collectand characterise, then determine the possible toxicology ofairborne particles in the south Wales region. High-resolutionField Emission SEM has shown that the coal mine dusts consistlargely of an assemblage of mineral grains and vehicle exhaustparticles. SEM-EDX has shown that the mineralogical make-up ofthe PM10 is complex, heterogeneous, and constantly changing.These findings are supported by analytical TEM-EPXMA.However, patterns can be determined relating the mineralogicalcomposition of the airborne particles to collection locationsand mining activities within the opencast. At our studyopencast, Park Slip West, quartz, which has known healtheffects, never exceeded 30% of the total collection mass, andaverage levels were much less. Vehicle exhaust emissions wasthe largest source in terms of particle numbers. The mass ofairborne particulate matter within the pit averagedapproximately twice that of outside the pit: importantlyhowever, this higher mass was due to relatively large, andnon-respirable, mineral grains. This study demonstrates that the physicochemical andmineralogical characterisation of airborne particles frommining and quarrying is essential to quantify the respirablefraction, and to identify potentially hazardous componentswithin the PM10.  相似文献   
292.
Summary Defense behavior by brooding Gonodactylus bredini females was studied in staged fights against conspecific challengers. Females brooding eggs were more successful at defending their dwelling cavities than were nonreproductive females. Females caring for larvae were no more successful at cavity defense than were controls.Brooding females do not defend cavities by using more aggressive acts or by engaging in longer fights than nonreproductive females. The increase in defense success seems to be due to a greater willingness to continue a contest after being struck by a challenger. Also, brooding females make more frequent use of threats, in particular the Meral Spread display, than controls.Females defend cavities as vigorously as if they still had eggs 4 or 5 days after their eggs have been removed. Within the first 24 h after oviposition, a female's success at defending a cavity is greatly reduced compared to that of a female just 1 day later.  相似文献   
293.
The LC50 values of eight triorganotin compounds for crab zoeae, Rhithropanopeusharrisii correlate with substituent constants reflecting partitioning effects. Computed molar surface areas predict toxicity as well as any parameter used suggesting that partitioning into lipids controls the toxicity.  相似文献   
294.
295.
In recent years, the so-called ‘resource curse’ syndrome has gained increasing currency. Growing evidence suggests that many African countries with significant natural wealth have actually reaped limited rewards, instead experiencing underdevelopment, corruption, political instability, and in some cases, violent conflict. In the small West African state of Sierra Leone, it has been suggested that diamonds played a key role in fuelling a brutal civil war during the 1990s, an issue that has given rise to a burgeoning literature on ‘blood diamonds’. However, as Sierra Leone emerges from a decade of destruction, other research suggests that diamonds could actually provide the impetus for post-war reconstruction. This paper explores the role of alluvial diamond mining in post-conflict Sierra Leone, focusing on two communities in the Eastern Province that were badly affected by the war. Drawing on field-based research conducted between 2002 and 2007, the paper considers the diamond mining situation in the context of broader development strategies in post-conflict reconstruction. It is argued that sustainable development can only be achieved if future policies are based on a detailed understanding of relationships between diamond mining and rural development at local, regional and national levels.  相似文献   
296.
African savanna elephants, Loxodonta africana, live in stable family groups consisting of adult females and their dependent offspring. During the dry season, clans consisting of several family groups typically share a common home range. We compared spatial relationships and mitochondrial DNA (mtDNA) haplotypes among 14 adult female elephants within 3 clans during the dry season in northern Zimbabwe. Spatial relationships were studied by radio-tracking. Home-range similarity was quantified by correlating the estimated utilization distributions of all pairs of elephants. Clans were identified by cluster analysis of the home-range similarity values. All three clans contained at least two of the five mtDNA haplotypes that were found, indicating that clan members are not necessarily matrilineally related. Within clans, home ranges of elephants with the same haplotype were not significantly more similar to each other than those of elephants with different haplotypes. Most elephants within each clan used their shared home ranges independently of each other: the distribution of distances between their positions at any given time did not differ from the distribution expected by chance. However, 8 out of the 26 within-clan pairs exhibited long-term coordination of space use by remaining within known hearing distance of each others low-frequency calls significantly more often than expected by chance. At least four of these coordinated pairs consisted of animals in different family groups. Elephants in three of the four different-family pairs whose movements were coordinated had different haplotypes. Further research is needed to determine the relationship between these coordinated movements and conventionally defined bond-group behavior.Electronic Supplementary Material Supplementary material is available in the online version of this article at .Communicated by C. Nunn  相似文献   
297.
ABSTRACT: Ground water nitrate contamination and water level decline are common concern in Nebraska. Effects of artificial recharge on ground water quality and aquifer storage recovery (ASR) were studied with spreading basins constructed in the highly agricultural region of the Central Platte, Nebraska. A total of 1.10 million m3 of Platte River water recharged the aquifer through 5000 m2 of the recharge basins during 1992, 1993, and 1994. This is equivalent to the quantity needed to completely displace the ground water beneath 34 ha of the local primary aquifer with 13 m thickness and 0.25 porosity. Successful NO3-N remediation was documented beneath and downgradient of the recharge basins, where NO3-N declined from 20 to 2 mg L-1. Ground water atrazine concentrations at the site decreased from 2 to 0.2 mg L-1 due to recharge. Both NO3-N and atrazine contamination dramatically improved from concentrations exceeding the maximum contaminant levels to those of drinking water quality. The water table at the site rose rapidly in response to recharge during the early stage then leveled off as infiltration rates declined. At the end of the 1992 recharge season, the water table 12 m downgradient from the basins was elevated 1.36 m above the preproject level; however, at the end of the 1993 recharge season, any increase in the water table from artificial recharge was masked by extremely slow infiltration rates and heavy recharge from precipitation from the wettest growing season in over 100 years. The water table rose 1.37 m during the 1994 recharge season. Resultant ground water quality and ASR improvement from the artificial recharge were measured at 1000 m downgradient and 600 m upgradient from the recharge basins. Constant infiltration rates were not sustained in any of the three years, and rates always decreased with time presumably because of clogging. Scraping the basin floor increased infiltration rates. Using a pulsed recharge to create dry and wet cycles and maintaining low standing water heads in the basins appeared to reduce microbial growth, and therefore enhanced infiltration.  相似文献   
298.
This study compares the recidivism rates of two groups of Illinois drivers who had their driver's licenses revoked for alcohol-impaired driving and who received restricted driving permits. Drivers in both groups had more than two driving under the influence (DUI) actions against their record within 5 years or were classed as level III alcohol dependents. Drivers in one group were required to install breath alcohol ignition interlock devices in their vehicles and drivers in the other group were not. The research found that drivers with the interlock were one-fifth as likely to be arrested for DUI during the 1 year the device was installed as the comparison group, which did not have the device. However, once the ignition interlock was removed, drivers in this group rapidly returned to DUI arrest rates similar to those in the comparison group. These findings echo previous literature. Additionally, the study showed that this voluntary program in Illinois reached only 16% of the drivers who met the requirements for installing the interlock device. Finally, this study found that individuals who were removed from the interlock program and returned to revoked status continued to drive. Within 3 years, approximately 50% of this latter group were involved in a crash or were arrested for DUI or with an invalid driver's license. Conclusions drawn from the study suggest that the breath alcohol ignition interlock device is effective in preventing continued driving while impaired. However, the large-scale effectiveness of the device is limited since most of the drivers eligible for the device do not have it installed. To have a significant impact, the interlock device must represent a better alternative to drivers whose licenses were suspended or revoked because of alcohol arrests compared to remaining on revoked status without having the device installed. Finally the research suggests that, given the rapid return to predevice recidivism, the devices should remain installed until drivers can demonstrate an extended period of being alcohol free.  相似文献   
299.
Environment, Development and Sustainability - The large-scale water-induced erosion is one of the most determining elements on land degradation in subtropical monsoon-dominated region. From this...  相似文献   
300.
资源利用与资源退化在时间及空间领域上的表现有所分异。识别出那些受人为干扰严重且易于发生资源退化的区域(资源利用的热点地区),对这些区域给予重视并采取特殊的管理机制以避免资源的进一步退化和环境的恶化,对资源的可持续利用具有重要的现实意义。论文以印度北部山地小流域的研究为例,根据当地实际情况,选取4个参数作为评价指标,即资源利用的重要性、资源的需求程度、资源利用的可获取性以及人类活动造成的景观生态学的干扰指数,利用遥感技术和地理信息系统对资源利用热点地区的识别进行了初步探讨。通过研究,将该流域划分为3种区域,即高度敏感区、中度敏感区和低敏感区,分别体现了不同的资源退化在空间上的分布。  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