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   9685篇
  免费   2篇
  国内免费   1篇
安全科学   3篇
废物处理   770篇
环保管理   1216篇
综合类   937篇
基础理论   3115篇
环境理论   1篇
污染及防治   1742篇
评价与监测   1006篇
社会与环境   898篇
  2021年   1篇
  2020年   1篇
  2019年   3篇
  2018年   1474篇
  2017年   1374篇
  2016年   1195篇
  2015年   124篇
  2014年   20篇
  2013年   8篇
  2012年   463篇
  2011年   1341篇
  2010年   690篇
  2009年   598篇
  2008年   877篇
  2007年   1229篇
  2006年   5篇
  2005年   18篇
  2004年   34篇
  2003年   61篇
  2002年   98篇
  2001年   19篇
  2000年   15篇
  1999年   2篇
  1998年   9篇
  1996年   2篇
  1995年   1篇
  1993年   1篇
  1984年   12篇
  1983年   8篇
  1978年   2篇
  1972年   1篇
  1935年   2篇
排序方式: 共有9688条查询结果,搜索用时 15 毫秒
661.
662.

Purpose  

Many reports on purification of water containing pesticides are based on studies using unformulated active ingredients. However, most commercial formulations contain additives/adjuvants or are manufactured using microencapsulation which may influence the purification process. Therefore, the main objective of this work was to develop and test a pilot scheme for decontaminating water containing pesticides formulated with antifoaming/defoaming agents.  相似文献   
663.

Introduction  

We conducted a yearly polluted-reference sampling to assess the effects of petroleum pollution on life cycle characteristics of the meiobenthic nematode Odontophora villoti. Samples were taken every 15 days between 26 November 2004 and 25 November 2005 from two beaches of Bizerte bay (Tunisia), Rimel and Tunisian Refining Industries Company (TRIC). The latter site is located in front of the “Tunisian Refining Industries Company” runoff.  相似文献   
664.
Previous studies on arthropods showed that seasonality and parity in breeding considerably impact the direction of sex differences in immunocompetence, and it has been suggested that life span and the time window available for breeding play key roles in shaping sex-differences in immunity. One proposed mechanism behind this phenomenon is differential investment into life history traits in sexes. Here, we tested whether in a seasonally breeding semelparous arthropod sexes differ in their immunocompetence, predicting that females would show weaker immune response than males. We compared encapsulation efficiency (a well-established and widely used method for assessing immunocompetence) of freshly matured, virgin males and females of the lycosid spider Pardosa agrestis (Westring, 1861). On average, males mounted stronger immune response than females and the extent of encapsulation was positively associated with prosoma length in males, but not in females. Also, time until maturation was positively related to the extent of encapsulation in both sexes, but did not significantly affect adult prosoma length. We propose that sex-difference in encapsulation is likely shaped by combined effects of relatively higher costs of reproduction in females, narrow time window of reproductive activity, and the absence of trade-off between current and future reproduction.  相似文献   
665.
Recent studies on ecological networks have quantified the contribution of ecological, historical, and evolutionary factors on the structure of local communities of interacting species. However, the influence of species’ biogeographical traits, such as migratory habits or phylogeographical history, on ecological networks is poorly understood. Meta-networks, i.e., networks that cover large spatial extensions and include species not co-occurring locally, enable us to investigate mechanisms that operate at larger spatial scales such as migratory patterns or phylogeographical distributions, as well as indirect relationships among species through shared partners. Using a meta-network of hummingbird-plant interaction across Mexico, we illustrate the usefulness of this approach by investigating (1) how biogeographical and morphological factors associate with observed interactions and (2) how species-specific biogeographical characteristics associate with species’ network roles. Our results show that all studied hummingbird and plant species in the meta-network were interrelated, either directly or through shared partners. The meta-network was structured into modules, resulting from hummingbirds and plants interacting preferentially with subsets of species, which differed in biogeographical, and, to a lesser extent, morphological traits. Furthermore, migrants and hummingbirds from Nearctic, Transition, and widespread regions had a higher topological importance in the meta-network. Our study illustrates how meta-networks may contribute to our current knowledge on species’ biogeographical traits and biotic interactions, providing a perspective complementary to local-scale networks.  相似文献   
666.
New finds of bones of the Egyptian Mongoose (Herpestes ichneumon), one from Portugal and one from Spain, were directly 14C dated to the first century AD. While the Portuguese specimen was found without connection to the Chalcolithic occupation of the Pedra Furada cave where it was recovered, the Spanish find, collected in the city of Mérida, comes from a ritual pit that also contained three human and 40 dog burials. The finds reported here show that the Egyptian mongoose, contrary to the traditional and predominant view, did not first arrive in the Iberian Peninsula during the Muslim occupation of Iberia. Instead, our findings are consistent with the hypothesis that the species was first introduced by the Romans, or at least sometime during the Roman occupation of Hispania. Therefore, radiocarbon dating of new archaeological finds of bones of the Egyptian Mongoose (Herpestes ichneumon) in the Iberian Peninsula push back the confirmed presence of the species in the region by approximately eight centuries, as the previously oldest dated record is from the ninth century. With these new dates, there are now a total of four 14C dated specimens of Egyptian mongooses from the Iberian Peninsula, and all of these dates fall within the last 2000 years. This offers support for the hypothesis that the presence of the species in Iberia is due to historical introductions and is at odds with a scenario of natural sweepstake dispersal across the Straits of Gibraltar in the Late Pleistocene (126,000–11,700 years ago), recently proposed based on genetic data.  相似文献   
667.
By 2050, 75 % of the world’s population will live in cities and the occurrence of heat wave events might have doubled. Mapping the climate and land use change impact for urban heat events should set the agenda for adaptation planning at the local scale. Literature on urban heat mapping does not reveal a clear indicator to visualise the urban heat impacts that includes consequences of land use and climate changes for planning purposes. This paper introduces a stepwise approach to develop a single complex indicator to map the urban heat impact for local climate adaptation planning processes. Information on climatic drivers and land use characteristics are combined and projected for future land use and climate change impacts. Next, several visualisation techniques are developed to investigate which techniques are most effective to visualise complex information with multiple variables in one visualisation. A usability test is performed to investigate how indicator and map meet the information and communication needs of policy makers. Our findings reveal that it is important to add information on future impacts to set the agenda for adaptation planning at the local scale. Applying cartographic techniques in a map series presentation has proven to be effective to map complex information in a single image and fulfil most of the identified information needs. Based on our finding, we introduce the information enrichment chain as a promising approach to support local adaptation planning.  相似文献   
668.
Coastal regions worldwide are during the process of rapid urban expansion. However, expanded urban settlements in land-sea interfaces have been faced with unprecedented threats from climate change related hazards. Adaptation to coastal hazards has received increasing attention from city managers and planners. Adaptation and land management practices are largely informed by remote sensing and land change modeling. This paper establishes a framework that integrates land change analysis, coastal flooding, and sea level rise adaptation. Multilayer perceptron neural network, similarity learning, and binary logistic regression were applied to analyze spatiotemporal changes of residential, commercial, and other built-up areas in Bay County, Florida, USA. The prediction maps of 2030 were produced by three models under four policy scenarios that included the population relocation strategy. Validation results reveal that three models return overall acceptable accuracies but generate distinct landscape patterns. Predictions indicate that planned retreat of residents can greatly reduce urban vulnerability to sea level rise induced flooding. While managed realignment of the coast brings large benefits, the paper recommends different mixes of adaptation strategies for different parts of the globe, and advocates the application of reflective land use planning to foster a more disaster resilient coastal community.  相似文献   
669.
Warming climatic conditions can pose problems for crop production in many parts of the world, but detailed information on the expression of heat and drought stress resistance genes of potentially affected crop plants is lacking. This information is important to have in order to most efficiently guide the breeding of crops that are adapted to new climatic conditions. A maize (Zea mays) gene microarray, a method used worldwide to evaluate the expression of tens of thousands of genes at once, was used to investigate changes in expression of genes involved in resistance to heat and water stress in milk stage popcorn kernels from undamaged and insect-damaged ears. Popcorn is a form of maize that is more susceptible to heat and drought stress due to its smaller root system. In years of heat and drought stress, expression of many heat shock- and senescence-related proteins increased compared to the year when weather was closer to average conditions, but the expression of many genes related to drought stress resistance decreased in years of weather stress. A different complex of heat shock protein and water stress resistance protein genes had higher expression in kernels from undamaged compared to insect-damaged ears in years of heat and drought stress. These results indicate that the interaction of biotic components, such as insects, are important to consider in developing crop lines with adaptation to stress as this will help identify additional genes and their regulatory components involved in heat and drought stress resistance that might otherwise be overlooked, and will likely be an important strategy for the most effective development of climate stress-tolerant crops globally.  相似文献   
670.
The risks related to global climate change are seen as threats to companies, taking into consideration their impact on the return on investment. In order to mitigate climate risk and introduce new opportunities to financiers, companies need to identify, manage, and report climate risks. The purpose of this paper is to investigate the climate risks disclosed by the 100 largest companies in the world, according to the Bloomberg and Price Waterhouse Coopers (PwC 2015) classification, and identify some characteristics of these companies that explain the disclosure level of such information. Preliminary results revealed that of the companies investigated, 14% did not disclose any climate risk information in the Carbon Disclosure Program (CDP) report. Also, from the companies that disclosed information according to the Global Reporting Initiative (GRI), 9.9% did not provide information regarding policies, actions, and strategies for mitigating the risks related to climate change. The results shown by the content analysis suggested that, in general, there is still a low level of disclosure about climate risks by these companies. The final results through econometric instruments and statistical tests indicate that the size of the company or the fact that corporations are from developed countries do not necessarily explain the level of information disclosed. However, the activity sector, the continent, and the efficiency of the Board of Directors are factors that strongly explain the level of climate risk disclosure. We conclude that more effort is needed to encourage an engaging attitude from corporations to develop actions, policies, and strategies to mitigate climate change risks and threats. In addition, the world’s largest companies should make a greater investment in climate risk disclosure.  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