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   950篇
  免费   41篇
  国内免费   70篇
安全科学   120篇
废物处理   17篇
环保管理   187篇
综合类   462篇
基础理论   132篇
污染及防治   33篇
评价与监测   60篇
社会与环境   33篇
灾害及防治   17篇
  2023年   9篇
  2022年   12篇
  2021年   23篇
  2020年   26篇
  2019年   17篇
  2018年   14篇
  2017年   34篇
  2016年   27篇
  2015年   35篇
  2014年   51篇
  2013年   73篇
  2012年   54篇
  2011年   91篇
  2010年   75篇
  2009年   62篇
  2008年   45篇
  2007年   83篇
  2006年   54篇
  2005年   49篇
  2004年   36篇
  2003年   45篇
  2002年   36篇
  2001年   17篇
  2000年   28篇
  1999年   14篇
  1998年   15篇
  1997年   6篇
  1996年   6篇
  1995年   6篇
  1994年   1篇
  1993年   4篇
  1992年   2篇
  1991年   1篇
  1990年   3篇
  1989年   2篇
  1987年   1篇
  1985年   2篇
  1980年   1篇
  1978年   1篇
排序方式: 共有1061条查询结果,搜索用时 546 毫秒
311.
中小型燃煤锅炉SO2治理技术现状及建议   总被引:3,自引:0,他引:3  
综述了国内中小型燃煤锅炉脱硫技术现状,在此基础上根据我国国情阐明了选择脱硫工艺应遵循的原则,并就中小型燃煤锅炉开展脱硫工作提出了建议。  相似文献   
312.
我国食用菌产业的发展现状及开发策略   总被引:7,自引:0,他引:7  
从食用菌栽培种类、栽培技术、加工技术、出口贸易等方面阐述了我国食用菌产业的发展现状,并在此基础上提出了持续、健康、稳定发展我国食用菌产业的开发策略:即大力开发种质资源;开发新原料、新配方;建立大型企业,实现标准化,创建特色品牌;加强食用菌保鲜和深加工的开发;建立健全质量标准体系,等。此外,还需加强食用菌遗传学、生理学、生态学、病虫害防治等方面的研究,以期为创造新品种、优质高产提供理论依据。  相似文献   
313.
PROBLEM: Twenty-nine percent of Americans failed to use their seat belts in 2000. Efforts to improve safety belt usage can be enhanced by identifying specific factors that motivate belt use. METHOD: Motorist survey data were used to examine the effect of Perceived Risk of being Ticketed (PRT) for a seat belt infraction on self-reported seat belt use. RESULTS: Analyses indicated that individuals and groups of individuals who have higher PRT typically report higher belt usage. Factorial analyses indicated that this perceived risk to belt use relationship holds both within groups with generally high (e.g., upper income) and generally low (e.g. young men) overall self-reported belt use. DISCUSSION: Applications of PRT to improve seat belt use are discussed. IMPACT ON INDUSTRY: Enforcement of existing laws, perhaps through selective traffic enforcement programs, and strengthening laws to create a higher perception of being ticketed by motorists should increase safety belt use thereby saving lives and reducing cost for individuals, government, and industry.  相似文献   
314.
由于化学合成抗抑郁药在长期服用后会出现严重的毒副作用,因此作用温和、副作用少的传统中药及其方剂越来越受到人们的关注和患者的欢迎.本文从几种中药及其方剂的作用机制和抗抑郁效果方面,对目前国内外抗抑郁中药的研究现状进行综述.参13.  相似文献   
315.
Xishuangbanna is on the northern margins of tropical Asia in southwestern China and has the largest area of tropical forest remaining in the country. It is in the Indo‐Burma hotspot and contains 16% of China's vascular flora in <0.2% of the country's total area (19,690 km2). Rapid expansion of monoculture crops in the last 20 years, particularly rubber, threatens this region's exceptional biodiversity. To understand the effects of land‐use change and collection on orchid species diversity and determine protection priorities, we conducted systematic field surveys, observed markets, interviewed orchid collectors, and then determined the conservation status of all orchids. We identified 426 orchid species in 115 genera in Xishuangbanna: 31% of all orchid species that occur in China. Species richness was highest at 1000–1200 m elevation. Three orchid species were assessed as possibly extinct in the wild, 15 as critically endangered, 82 as endangered, 124 as vulnerable, 186 as least concern, and 16 as data deficient. Declines over 20 years in harvested species suggested over‐collection was the major threat, and utility value (i.e., medicinal or ornamental value) was significantly related to endangerment. Expansion of rubber tree plantations was less of a threat to orchids than to other taxa because only 75 orchid species (17.6%) occurred below the 1000‐m‐elevation ceiling for rubber cultivation, and most of these (46) occurred in nature reserves. However, climate change is projected to lift this ceiling to around 1300 m by 2050, and the limited area at higher elevations reduces the potential for upslope range expansion. The Xishuangbanna Tropical Botanical Garden is committed to achieving zero plant extinctions in Xishuangbanna, and orchids are a high priority. Appropriate in and ex situ conservation strategies, including new protected areas and seed banking, have been developed for every threatened orchid species and are being implemented.  相似文献   
316.
《组织行为杂志》2017,38(5):692-711
A well‐known downside of organizational mergers is that employees fail to identify with the newly formed organization. We argue that developing an understanding of factors that affect post‐merger identification requires taking the pre‐merger status of the merger partners relative to each other into account. This is because relative pre‐merger status determines employees' susceptibility to different aspects of the merger process. Specifically, for employees of a high status pre‐merger organization, we expected post‐merger identification to be strongly influenced by (i) pre‐merger identification and (ii) the perceived change in the status. In contrast, we expected post‐merger identification of employees of a low status pre‐merger organization to be strongly affected by the perceived justice of the merger event. Longitudinal data were obtained from a merger of two public sector organizations and the results supported our hypotheses. Our study shows that the extent to which pre‐merger identification, status change, and justice are important determinants of post‐merger identification depends on the relative pre‐merger status of the merger partners. Our discussion focuses on theoretical implications and managerial ramifications of these findings. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
317.
根据2002年-2011年同安湾海域水质监测结果,采用单因子污染指数评价法和富营养化水平法对同安湾海域近十年水质状况进行分析与评价。结果表明,该海域主要污染因子为无机氮和活性磷酸盐,各年均值大部分超三类海水水质标准;溶解氧、化学需氧量、重金属(汞、铜、铅、镉)及砷、油类均符合一类海水水质标准。该海域目前处于N高P低的富营养状态,氮磷比趋势不够稳定,但磷限制性富营养化趋势有所下降。  相似文献   
318.
随着农村经济的不断发展,农村环境污染日趋严重。虽然吉林省在农村环境污染防治和生态保护方面取得了一些成效,但农村环保工作仍然十分薄弱。农村环境连片整治示范项目以饮用水水源保护和人居环境质量改善为主要目标,重点支持农村饮用水水源地保护、生活污水和生活垃圾污染治理、畜禽养殖污染治理与综合利用等项目。基于吉林省农村环境存在的共性问题和污染成因分析,有关人士提出了“切实保护农村饮用水源地,加强村庄生活污染治理力度,畜禽养殖污染治理,工矿企业污染治理,农业面源污染治理”等五方面治理措施,有利于促进全省农村环境的有效改善。  相似文献   
319.
有机聚集体(OA)是水体中物质循环和能量流通的重要枢纽,但在不同营养水平湖泊中的比较研究仍相当匮乏.于2019~2021年间,采集了不同季节贫营养抚仙湖、中营养天目湖、中度富营养太湖和重度富营养星云湖表层水样,利用扫描电镜、表面荧光显微镜和流式细胞仪等研究了4个典型湖泊中OA及其附着细菌的时空变化特征.结果表明:(1)抚仙湖、天目湖、太湖和星云湖中,OA丰度的年均值分别为1.4×104、 7.0×104、 27.7×104和16.0×104ind·mL-1; OA附着细菌丰度的年均值分别为0.3×106、 1.9×106、 4.9×106和6.2×106 cells·mL-1;附着细菌占总细菌的比值分别为30%、 31%、 50%和38%.(2)夏季OA丰度显著高于秋冬季;但夏季附着细菌占总细菌的比值为26%,显著低于其它3个季节.(3)湖泊营养状态是影响OA及其附着细...  相似文献   
320.
从海洋大气的环境试验能力和环境试验方法 2方面展开了国内外多环境因素组合/综合的对比分析,探讨了海洋大气主要环境因素温度、湿度、盐雾、太阳辐射和诱发环境因素振动产生的环境效应及其相互影响,分别列举了2、3、4、5种环境因素耦合环境试验方法与成果。最后,针对装备海洋大气环境多因素组合/综合试验及方法目前的研究现状,提出了建议和展望。  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