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   1263篇
  免费   74篇
  国内免费   176篇
安全科学   123篇
废物处理   22篇
环保管理   265篇
综合类   509篇
基础理论   204篇
环境理论   3篇
污染及防治   149篇
评价与监测   20篇
社会与环境   133篇
灾害及防治   85篇
  2024年   1篇
  2023年   15篇
  2022年   47篇
  2021年   46篇
  2020年   59篇
  2019年   49篇
  2018年   39篇
  2017年   70篇
  2016年   72篇
  2015年   53篇
  2014年   67篇
  2013年   137篇
  2012年   73篇
  2011年   90篇
  2010年   48篇
  2009年   60篇
  2008年   68篇
  2007年   87篇
  2006年   65篇
  2005年   45篇
  2004年   33篇
  2003年   56篇
  2002年   46篇
  2001年   29篇
  2000年   32篇
  1999年   11篇
  1998年   14篇
  1997年   10篇
  1996年   11篇
  1995年   11篇
  1994年   10篇
  1993年   15篇
  1992年   8篇
  1991年   12篇
  1990年   9篇
  1989年   5篇
  1988年   5篇
  1982年   1篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1973年   1篇
排序方式: 共有1513条查询结果,搜索用时 218 毫秒
781.
顺德区甘竹罐头食品有限公司二期污水处理工程设计处理能力为400吨/日,该工程采用上升流水解(酸化)-序列间歇式活性污泥法(SBR)新工艺,操作简单、运行稳定、效果优良、处理后水质达到中华人民共和国《肉类加工工业水污染物排放标准》(GB 13457-92)一级排放标准要求。本文按工艺流程介绍了系统中各构的设计参数、设备配置情况及半年来的运行体会,并对存在的问题进行了分析,提出了改进措施。  相似文献   
782.
城市食物生产与消费系统磷代谢研究   总被引:1,自引:1,他引:0  
研究运用物质流分析方法,构建基于物质代谢过程的城市食物生产与消费系统磷代谢分析框架,即追踪以"食物生产"、"食物加工"、"居民消费"、"废物处置"为主要过程的磷代谢路径,解析磷代谢主要过程机制并提出相应的核算方法;在此基础上,以合肥市食物生产与消费系统为例进行了案例研究.结果表明,2008年合肥市食物生产消费系统磷的总...  相似文献   
783.
厨余发酵菌株筛选及单菌发酵对其品质的影响   总被引:1,自引:1,他引:0  
为筛选出适合厨余发酵的菌种并探讨各菌种在发酵过程中的作用,文章从厨余发酵糟感官品质变化的角度出发,通过多次初筛、复筛得到发酵效果好的优良菌株,将各菌种接种于厨余中进行发酵,通过对各发酵组不同时间段微生物、真蛋白、葡萄糖等指标的分析,考察各菌种在发酵过程中的作用.结果表明:筛选出的4株菌分别为L22、Lc、Ydy、S1,...  相似文献   
784.
The use of lead poses significant hazardous occupational exposure to workers in the electronics industry, and also causes environmental challenges at the end of product life. For the past decade, there has been a global effort in the electronics industry to initiate a move towards using lead-free materials for the production of printed circuit boards. However, there are technical and economic challenges, such as long term reliability and rework capability, that remain to hinder the universal implementation of lead-free materials. As a result, many electronics products are still currently manufactured and assembled using materials containing lead.The costs for investigating and evaluating the various lead-free electronics materials and manufacturing processes can be cost prohibitive for an individual company to undertake alone. Consequently, the New England Lead-free Electronics Consortium was formed as a collaborative effort of New England companies spanning the electronics supply chain to help move the industry towards lead-free electronics. The Consortium is a working collaboration of industry, government, and academia. For the past several years, the Consortium has conducted research and testing for using various lead-free materials for the manufacture of printed circuit boards. The Consortium has been successful in identifying lead-free materials and processes to address the challenges of assembly and rework. The Consortium is currently conducting research to address the long-term reliability challenge of lead-free electronics.  相似文献   
785.
鄱阳湖区粮食供给功能的空间格局分析   总被引:4,自引:0,他引:4  
在种植制度复杂、地块破碎及多阴雨天气的南方地区,应用卫星遥感植被指数时间序列数据提取复种指数受到中低空间分辨率的限制。使用较高空间分辨率影像是提取该区域复种信息有效的数据源。论文以鄱阳湖区为研究区,通过遥感解译提取水田空间信息;在界定单/双季稻生长期物候历的前提下,根据水稻不同生长期内归一化植被指数(NDVI)的明显差异,选择合理时间窗口的TM影像获取水田NDVI数据,采用非监督分类法提取单/双季稻的空间分布信息;结合湖区乡镇不同熟制水稻单产数据估算出基于栅格的水稻产量。研究表明,4月下旬到6月下旬是判别双季早稻与单季稻空间分布的合理时间窗口;7月上旬到8月上旬及9月中旬到10上旬是判别单季稻与双季晚稻空间分布的合理时间窗口。2005年,单季稻播种面积为3 081.58 km2,晚稻/早稻播种面积为3 602.97 km2,水稻复种指数为153.9%。单季稻普遍分布在市县建成区周边,双季稻主要分布在河口三角洲等地。全年水稻总产量约1 650×104 t,单季稻占30.5%,双季稻占69.5%。赣江下游地区两种熟制水稻产量均较高,而湖汊及湖区外围丘陵地区产量较低。  相似文献   
786.
Different municipal solid waste landfill methods and landfill ages had crucial impacts on bacterial abundance and composition in leachate.  相似文献   
787.
Actual textile wastewater and synthesized wastewater containing various textile dyes were photocatalytic degraded by the UVH2O2Fs-TiO2 process in an aimular-flow photocatalytic reactor. In this process, a photon kinetic-measure was adopted to obtain constant rates of dyes decomposition. It was theorized that, by illumination at different UV frequencies, the electrons within the semiconductor were excited from the valence band to the conduction band, yielding the formation of electron-hole pairs which are the pre-requisites for photocatalysis. CPT (critical photonic time) exposure required to cause 90% of vibrations between the double and single bonds along the molecular chain of the dyes to be oxidized, was taken to measure the photocatalytic activities. The CPTs varied with the frequencies of the UV spectral areas. The derivatization of CPT from the first-order kinetic law was presented.  相似文献   
788.
餐厨垃圾特性及处理技术研究   总被引:4,自引:0,他引:4  
餐厨垃圾是城市生活垃圾的主要组成部分.餐厨垃圾中有机物含量丰富、水分含量高,容易腐烂并产生臭味气味,会对环境卫生造成恶劣影响.介绍餐厨垃圾的主要组成成分、特性以及对环境产生的危害.综述餐厨垃圾常规处理方法,包括粉碎直排、堆肥填埋、厌氧发酵及好氧发酵.重点考察厌氧发酵过程中氢能源产生的影响因素.综合比较各种处理方法的特点、适用条件、处理效果、影响因素等方面.综上得出厌氧发酵是一种对环境危害较小,同时可回收能源的处理方法,具有广阔应用前景.其研究重点在于提高餐厨垃圾的氢气产量、氢气浓度、产氢速率等指标.  相似文献   
789.
An extended hazard and operability (HAZOP) analysis approach with dynamic fault tree is proposed to identify potential hazards in chemical plants. First, the conventional HAZOP analysis is used to identify the possible fault causes and consequences of abnormal conditions, which are called deviations. Based on HAZOP analysis results, hazard scenario models are built to explicitly represent the propagation pathway of faults. With the quantitative analysis requirements of HAZOP analysis and the time-dependent behavior of real failure events considered, the dynamic fault tree (DFT) analysis approach is then introduced to extend HAZOP analysis. To simplify the quantitative calculation, the DFT model is solved with modularization approach in which a binary decision diagram (BDD) and Markov chain approach are applied to solve static and dynamic subtrees, respectively. Subsequently, the occurrence probability of the top event and the probability importance of each basic event with respect to the top event are determined. Finally, a case study is performed to verify the effectiveness of the approach. Results indicate that compared with the conventional HAZOP approach, the proposed approach does not only identify effectively possible fault root causes but also quantitatively determines occurrence probability of the top event and the most likely fault causes. The approach can provide a reliable basis to improve process safety.  相似文献   
790.
The Urban Farming Movement is relatively young in Louisville, Kentucky but it seems to be off to a good start. Being in its earliest stages, assessments of this effort must be made cautiously, even tentatively. Examining a movement that is in progress requires a study of the state's land use and segregation policies, both of which have been dynamic in Kentucky. Further, this study is also relevant as there is a growing convergence of national and regional attitudes towards American obesity, while there are competing notions of food preference and food choice. All of which are influenced by racial politics, and there is a deep concern regarding food security. Considering all of these, it is necessary to examine the Government's efforts to address obesity/food imbalance in a variety of settings, especially where urban farming is expanding, such as Chicago and Detroit. In New York, roof-top gardens dot the landscape and the urban farm movement is largely a “success”. So, city leaders have chosen to address another health issue – trans fat. Rather than joining the food choice/preference debate by banning fast-food restaurants, city leaders have chosen to enact a trans-fat ban. Unpopular at first, other cities and states have followed, and the Federal Government will mandate a trans-fat ban this year. In Louisville, Chicago and Detroit, where the trans-fat bans did not succeed, the urban farm movement may be the primary means of addressing malnutrition, in the form of obesity.  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