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   635篇
  免费   21篇
  国内免费   5篇
安全科学   14篇
废物处理   33篇
环保管理   104篇
综合类   74篇
基础理论   193篇
污染及防治   167篇
评价与监测   48篇
社会与环境   23篇
灾害及防治   5篇
  2023年   6篇
  2022年   8篇
  2021年   7篇
  2020年   9篇
  2019年   10篇
  2018年   15篇
  2017年   28篇
  2016年   25篇
  2015年   18篇
  2014年   14篇
  2013年   66篇
  2012年   15篇
  2011年   26篇
  2010年   17篇
  2009年   26篇
  2008年   36篇
  2007年   38篇
  2006年   20篇
  2005年   22篇
  2004年   22篇
  2003年   15篇
  2002年   17篇
  2001年   20篇
  2000年   11篇
  1999年   8篇
  1998年   6篇
  1997年   8篇
  1996年   11篇
  1995年   10篇
  1994年   14篇
  1993年   8篇
  1992年   5篇
  1991年   3篇
  1990年   7篇
  1989年   5篇
  1988年   10篇
  1987年   7篇
  1986年   6篇
  1985年   5篇
  1984年   8篇
  1983年   4篇
  1982年   3篇
  1980年   5篇
  1979年   5篇
  1978年   4篇
  1977年   3篇
  1976年   4篇
  1973年   3篇
  1972年   5篇
  1969年   4篇
排序方式: 共有661条查询结果,搜索用时 921 毫秒
21.
Currently, a large number of companies consider recycling of materials as an opportunity to maximize profits and to reduce the environmental impact generated by these materials after they are disposed. However, there is also a strong constraint on the use of recycled materials mainly due to the lack of technical/scientific information, which would relate their physical properties to their recycling cycle. This information should be used in the initial phase of the product design to serve as reference for the simulation of a project to point out the physical properties obtained from recycling the Projected material (Pm). Thus, it would be possible to foresee some recycling strategy to keep the good characteristics of recycled materials by encouraging their use, regardless of the product to be designed.Therefore, the Recycling Cycle of Materials (RCM) is a tool that provides scientific/technical support in the selection of materials. It uses the information related to the physical properties of the Pm as a parameter for product design after five recycling cycles. For the case study, this tool has been applied to obtain the basic material of ABS/PC blend. Subsequently, this blend was evaluated using DSC, FTIR, traction and impact methods to obtain delimiting data for the definition of the mechanical properties resulting from the application of RCM.  相似文献   
22.
Rainwater characteristics can reveal emissions from various anthropogenic and natural sources into the atmosphere. The physico-chemical characteristics of 44 monthly rainfall events (collected between January and December 2012) from 4 weather stations (Bamenda, Ndop plain, Ndawara and Kumbo) in the Bamenda Highlands (BH) were investigated. The purpose was to determine the sources of chemical species, their seasonal inputs and suitability of the rainwater for drinking. The mean pH of 5 indicated the slightly acidic nature of the rainwater. Average total dissolved solids (TDS) were low (6.7 mg/L), characteristic of unpolluted atmospheric moisture/air. Major ion concentrations (mg/L) were low and in the order K+ 〉 Ca2+ 〉 Mg2~ 〉 Na+ for cations and NO3 〉〉 HCO3 〉 SO] 〉 CI- 〉 PO3- 〉 F- for anions. The average rainwater in the area was mixed Ca-Mg-SO4-CI water type. The CI-/Na+ ratio (1.04) was comparable to that of seawater (1.16), an indication that N a+ and CI originated mainly from marine (Atlantic Ocean) aerosols. High enrichments of Ca2+, Mg2+ and SO2- to Na+ ratios relative to seawater ratios (constituting 44% of the total ions) demonstrated their terrigenous origin, mainly from Saharan and Sahelian arid dusts. The K+/Na+ ratio (2.24), which was similar to tropical vegetation ash (2.38), and NO3 was essentially from biomass burning. Light (〈 100 mm) pre-monsoon and post-monsoon convective rains were enriched in major ions than the heavy (〉 100 mm) monsoon rains, indicating a high contribution of major ions during the low convective showers. Despite the acidic nature, the TDS and major ion concentrations classified the rainwater as potable based on the WHO guidelines.  相似文献   
23.
East African cichlids display extensive variation in sex determination systems. The species Astatotilapia calliptera is one of the few cichlids that reside both in Lake Malawi and in surrounding waterways. A. calliptera is of interest in evolutionary studies as a putative immediate outgroup species for the Lake Malawi species flock and possibly as a prototype ancestor-like species for the radiation. Here, we use linkage mapping to test association of sex in A. calliptera with loci that have been previously associated with genetic sex determination in East African cichlid species. We identify a male heterogametic XY system segregating at linkage group (LG) 7 in an A. calliptera line that originated from Lake Malawi, at a locus previously shown to act as an XY sex determination system in multiple species of Lake Malawi cichlids. Significant association of genetic markers and sex produce a broad genetic interval of approximately 26 megabases (Mb) using the Nile tilapia genome to orient markers; however, we note that the marker with the strongest association with sex is near a gene that acts as a master sex determiner in other fish species. We demonstrate that alleles of the marker are perfectly associated with sex in Metriaclima mbenjii, a species from the rock-dwelling clade of Lake Malawi. While we do not rule out the possibility of other sex determination loci in A. calliptera, this study provides a foundation for fine mapping of the cichlid sex determination gene on LG7 and evolutionary context regarding the origin and persistence of the LG7 XY across diverse, rapidly evolving lineages.  相似文献   
24.
25.
The use of multistage, dry, fluidized beds of continuously recycled, coal-based activated carbon appears technically and economically attractive for both adsorption of stack gas So2 and sequential conversion to elemental sulfur. Conceptual design details and economic factors are discussed for the treatment of power plant or oil refinery SO2 effluents with by-product sulfur recovery.  相似文献   
26.
Soil removal of propane, isobutane and n-butane from a waste air stream was evaluated in the laboratory and in a prototype soil bioreactor. Laboratory investigations indicated first-order kinetics and the potential to degrade light aliphatic hydrocarbons and trichlorethylene, a compound ordinarily resistant to aerobic biological treatment. The predicted behavior of the bioreactor, based on laboratory studies, agreed closely with the actual behavior of the Reid system. The prototype bioreactor reduced the hydrocarbon concentrations in the air by at least 90percent with a residence time of 15 minutes and a pressure drop of 85 cm of water. The bioreactor functioned well through a range of temperatures, 12°C to 24°C.  相似文献   
27.
Environmental Science and Pollution Research - Urban-dwelling birds can be useful biomonitors to assess the impact of the urbanisation on both public and wildlife health. Widely distributed urban...  相似文献   
28.
Over the last few decades the animal communication community has become increasingly aware that much communication occurs using multiple signals in multiple modalities. The majority of this work has been empirical, with less theoretical work on the advantages conferred by such communication. In the present paper, we ask: Why should animals communicate with multiple signals in multiple modalities? To tackle this question we use game theoretic techniques, and highlight developments in the economic signaling literature that might offer insight into biological problems. We start by establishing a signaling game, and investigate signal honesty under two prevailing paradigms of honest communication – costly signaling and cheap talk. In both paradigms, without further constraint, it is simple to show that anything that can be achieved with multiple signals can be achieved with one. We go on to investigate different sets of possible constraints that may make multiple signals and multimodal signals in particular more likely to evolve. We suggest that constraints on cost functions and bandwidths, orthogonal noise across modalities, strategically distinct modes, multiple qualities, multiple signalers, and multiple audiences, all provide biologically plausible scenarios that theoretically favor multiple and multimodal signaling.  相似文献   
29.
This research demonstrates the contribution of phenomenological inquiry within the realm of geographic and environmental planning. The contention is that a focus on the wide range of individual meanings and values ascribed to landscapes, a marginalized element in many planning assessments, can bring out data to more substantively inform decision making, A case study of user meanings imparted to residual waterfront land in Hoboken, New Jersey, USA, suggests that such property provides an array of amenities to residents. Most importantly, it expands the range of recreational activities, creates visual relief from the monotonous urban milieu, and provides scenic vistas to promote an awareness of the quality of life still possible in cities. The study concludes that planners can use phenomenology to generate data for more judicious decision making.  相似文献   
30.
ABSTRACT: Irrigation development of the dolomite aquifer in eastera Kankakee and northern Iroquois Counties, Illinois, is extensive and increasing. Interruptions of domestic supplies have been reported with increasing frequency during the 1980's. To address this issue, a regional assessment of the ground-water resources of the region was conducted in 1987 and 1988. Options for managing the dolomite aquifer were also investigated. Hydrogeology of the dolomite aquifer was determined using five aquifer tests. Tranamissivity values of the dolomite aquifer ranged from 14,000 to 50,000 gpd/ft (168 to 600 m3/m/day). Storage coefficients were between 0.0001 and 0.0002, within the range of a confined (artesian) aquifer. Based on flow-net analyses, recharge of the dolomite aquifer ranged from 85,000 to 285,000 gpd/mi2 (124.4 to 417.0 m3/day/km2). Water levels of the dolomite aquifer were mapped during five periods in 1987 and 1988 by measuring up to 226 wells completed in the dolomite aquifer. Maximum regional water-level declines because of irrigation pumpage were 44 feet (13.4 m) in 1987 and 72 feet (21.9 m) during the drought of 1988. Based on ground-water use data, precipitation records, and hydrogeologic information, the magnitude of water-level declines can be attributed more to differing hydrogeologic conditions than to pumpage or climatic changes. Existing ground-water management methods for resolving conflicts over the ground-water resources of the study area are reviewed and alternative management options explored.  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