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   1250篇
  免费   185篇
  国内免费   445篇
安全科学   281篇
废物处理   56篇
环保管理   173篇
综合类   938篇
基础理论   167篇
污染及防治   122篇
评价与监测   39篇
社会与环境   69篇
灾害及防治   35篇
  2024年   5篇
  2023年   31篇
  2022年   54篇
  2021年   60篇
  2020年   74篇
  2019年   68篇
  2018年   80篇
  2017年   75篇
  2016年   90篇
  2015年   69篇
  2014年   68篇
  2013年   112篇
  2012年   122篇
  2011年   121篇
  2010年   79篇
  2009年   102篇
  2008年   68篇
  2007年   96篇
  2006年   90篇
  2005年   68篇
  2004年   54篇
  2003年   51篇
  2002年   45篇
  2001年   42篇
  2000年   21篇
  1999年   25篇
  1998年   13篇
  1997年   20篇
  1996年   16篇
  1995年   10篇
  1994年   8篇
  1993年   7篇
  1992年   7篇
  1991年   8篇
  1990年   5篇
  1989年   1篇
  1987年   4篇
  1984年   1篇
  1982年   3篇
  1981年   1篇
  1980年   2篇
  1979年   2篇
  1977年   1篇
  1976年   1篇
排序方式: 共有1880条查询结果,搜索用时 116 毫秒
581.
Five students of a rescue training school cycled at 50 W for 20 min at 20 °C before walking at 5 km/hr up to 30 min in a climatic chamber at 55 °C and 30% relative humidity. 4 different types of clothing ensembles differing in terms of thickness and thermal insulation value were tested on separate days. All subjects completed 28–30 min in light clothing, but quit after 20–27 min in 3 firefighter ensembles due to a rectal temperature of 39 °C or subjective fatigue. No difference in the evolution of mean skin or rectal temperature was seen for the 3 turnout ensembles. Sweat production amounted to about 1000 g in the turnout gears of which less than 20% evaporated. It was concluded that the small differences between the turnout gears in terms of design, thickness and insulation value had no effect on the resulting heat physiological strain for the given experimental conditions.  相似文献   
582.
The heat transferred through protective clothing under long wave radiation compared to a reference condition without radiant stress was determined in thermal manikin experiments. The influence of clothing insulation and reflectivity, and the interaction with wind and wet underclothing were considered. Garments with different outer materials and colours and additionally an aluminised reflective suit were combined with different number and types of dry and pre-wetted underwear layers. Under radiant stress, whole body heat loss decreased, i.e., heat gain occurred compared to the reference. This heat gain increased with radiation intensity, and decreased with air velocity and clothing insulation. Except for the reflective outer layer that showed only minimal heat gain over the whole range of radiation intensities, the influence of the outer garments’ material and colour was small with dry clothing. Wetting the underclothing for simulating sweat accumulation, however, caused differing effects with higher heat gain in less permeable garments.  相似文献   
583.
热防护服是热环境下人体安全防护的主要装备,其标准的科学性和系统性对热环境下的人体安全防护具有重要的支持作用.国外对热防护服相关的技术标准予以充分重视,以性能测试技术方法为主体,建立了较为科学、完善的标准,并体现出新的发展趋势.通过对国外热防护服技术标准的调研,总结性能测试标准的共性内容,包括主要性能测试方法、实验设备、实验步骤、烧伤评估、人体模型和测试报告等.整套防护服装的性能测试技术及标准是研究的重点,出汗暖体假人将在防护服装性能测试领域被更为广泛的应用.最后,提出我国研制热防护服性能测试技术标准的建议.  相似文献   
584.
综述国内外烟气余热利用技术的研究及应用现状,主要包括热能直接回收、吸收式制冷、有机朗肯循环和温差发电等方式。结合气田开采实际,分析讨论各类余热利用技术在气田增压机组烟气余热利用中的应用潜力和发展方向。在选择余热利用方案时,应结合气田增压机组现有条件、机组性能以及运行模式等因素进行综合评估。  相似文献   
585.
Nitrate and phosphate export coefficient models were developed for coastal watersheds along the Santa Barbara Channel in central California. One approach was based on measurements of nutrient fluxes in streams from specific land use classes and included a watershed response function that scaled export up or down depending on antecedent moisture conditions. The second approach for nutrient export coefficient modeling used anthropogenic nutrient loading for land use classes and atmospheric nutrient deposition to model export. In an application of the first approach to one watershed, the nitrate and phosphate models were within 20% of measured values for most storms. When applied to another year, both nitrate and phosphate models generally performed adequately with annual, storm‐flow, and base‐flow values within 20% of measured nutrient loadings. Less satisfactory results were found when applied to neighboring watersheds with difference percentages of land use and hydrologic conditions. Application of the second approach was less successful than the first approach.  相似文献   
586.
Abstract

This article presents a case study of a projected solar assisted biomass district heating system in the north of Sweden. It is generally known that a biomass district heating system combined with solar heat brings many important benefits. The most common system solution is to install a heat store and a large solar collector field near the heating central. No plant of this type is however in operation in the northern part of Sweden. The main reason for this is that the solar irradiation at these latitudes is very low when the demand for heat is high. Solar heat could however be useful during summer in order to generate hot tap water. One problem is that the heat losses, calculated as percentage of the delivered heat, become very large during these months. This article presents the idea of allowing the connected households to generate their own hot tap water using solar collectors and heat stores installed in each house. The district heating network can therefore be closed in summer, which eliminates the heat losses outside the heating period. A case study of a projected plant has been carried out and it is shown that it is possible to reduce the heat losses by 20% compared to a conventional system. This idea also provides many other important technical and economic benefits.  相似文献   
587.
ABSTRACT: A 1990 nitrogen and phosphorus mass balance calculated for eight National Stream Quality Accounting Network (NASQAN) basins in the Albemarle-Pamlico Drainage Basin indicated the importance of agricultural nonpoint sources of nitrogen and phosphorus and watershed nitrogen retention and processing capabilities. Basin total nitrogen and phosphorus input estimates were calculated for atmospheric deposition (which averaged 27 percent of total nitrogen inputs and 22 percent of total phosphorus inputs); crop fertilizer (27 and 25 percent); animal-waste (22 and 50 percent, respectively); point sources (3 percent each of total nitrogen and total phosphorus inputs); and biological nitrogen fixation (21 percent of total nitrogen inputs). Highest in-stream nitrogen and phosphorus loads were measured in predominantly agricultural drainage areas. Intermediate loads were observed in mixed agricultural/urban drainage areas; the lowest loads were measured in mixed agricultural/forested drainage areas. The difference between the sum of the nutrient input categories and the sum of the in-stream nutrient loads and crop-harvest nutrient removal was assigned to a residual category for the basin. The residual category averaged 51 percent of total nitrogen inputs and 54 percent of total phosphorus inputs.  相似文献   
588.
589.
During the JCO-accident in Tokai-mura in 1999, the surrounding village was irradiated by an uncontrolled neutron flux. At some locations in that village, the thermal neutron flux was determined retrospectively by measurement of the very low activity of 51Cr and 60Co in stainless-steel spoons using γ-ray spectrometry in underground laboratories. Activities determined in the HADES underground facility are presented here, together with calibrations performed using a well-defined thermal neutron flux to directly estimate the fluence of thermal neutrons independent of most assumptions. The results show measurable 51Cr in three samples and 60Co in four samples taken from locations at distances of up to 430 m from the accident location despite the elapse of 4 half-lives of 51Cr before measurement. Effects of air transport of the samples were considered and shown to be negligible.  相似文献   
590.
介绍了石化废水污泥焚烧处理的工艺流程、主要影响因素,分析了该项技术的优缺点。  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