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   26392篇
  免费   425篇
  国内免费   1459篇
安全科学   829篇
废物处理   1256篇
环保管理   3594篇
综合类   5319篇
基础理论   6985篇
环境理论   8篇
污染及防治   6457篇
评价与监测   1557篇
社会与环境   2027篇
灾害及防治   244篇
  2023年   128篇
  2022年   317篇
  2021年   280篇
  2020年   282篇
  2019年   225篇
  2018年   917篇
  2017年   907篇
  2016年   943篇
  2015年   603篇
  2014年   701篇
  2013年   1787篇
  2012年   1087篇
  2011年   1867篇
  2010年   1269篇
  2009年   1440篇
  2008年   1642篇
  2007年   1843篇
  2006年   898篇
  2005年   813篇
  2004年   804篇
  2003年   814篇
  2002年   791篇
  2001年   828篇
  2000年   669篇
  1999年   444篇
  1998年   348篇
  1997年   343篇
  1996年   341篇
  1995年   355篇
  1994年   280篇
  1993年   270篇
  1992年   229篇
  1991年   209篇
  1990年   202篇
  1989年   200篇
  1988年   168篇
  1987年   146篇
  1986年   160篇
  1985年   155篇
  1984年   209篇
  1983年   159篇
  1982年   177篇
  1981年   162篇
  1980年   135篇
  1979年   153篇
  1978年   97篇
  1977年   99篇
  1975年   96篇
  1974年   102篇
  1972年   107篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
901.
液液萃取-气相色谱/串联质谱法测定水中五氯酚及其钠盐   总被引:1,自引:0,他引:1  
采用液液萃取处理水样,用气相色谱-串联质谱法测定样品中五氯酚及其钠盐,通过优化测定条件,使方法在1.00μg/L~500μg/L范围内线性良好.检出限和定量限分别为1.00μg/L和5.00μg/L,空白水样五氯酚钠3个质量浓度水平的加标回收率为89.8%~98.4%,5次平行试验测定结果的RSD为5.5%~10.7%...  相似文献   
902.
矿产资源规划理论的形成和发展   总被引:5,自引:0,他引:5  
矿产资源规划是区域发展规划的重要组成部分,是政府对矿业经济进行宏观调控的一种手段。本文从理论更新和完善的角度重新确立了区域矿产资源规划的理论体系,提出矿产资源规划理论经历形成、发展与创新三个阶段,并就矿产资源配置与价格规律、矿产资源经济区划理论和可持续发展理论在其中的深远影响进行了初步探讨。  相似文献   
903.
From 1975 to 2004, a municipal solid waste incinerator (MSWI) was operating in Montcada (Barcelona, Catalonia, Spain). Because of the potential health risks derived from emission of pollutants by the facility, especially polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), a long-term monitoring program focused on measuring the environmental levels of PCDD/Fs near the facility, and to assess the health risks for the population living in the neighborhood, was established between 1996 and 2002. A total number of 111 soil and 121 herbage samples were analyzed for PCDD/Fs during this period. Human health risks for the individuals living near the MSWI (500 and 1,000 m) were also assessed before (1998) and after modernization (2000) of the facility. It included PCDD/F inhalation, dermal contact, soil and dust ingestion, and food intake. All these data are here summarized. The environmental levels of PCDD/Fs showed that the MSWI was not the main responsible of the atmospheric pollution by these compounds. In turn, human health risks for the population living in the vicinity of the facility after introduction of a modern technology were negligible in comparison with the dietary PCDD/F exposure.  相似文献   
904.
Retention of estrogenic steroid hormones by selected New Zealand soils   总被引:1,自引:0,他引:1  
We performed batch sorption experiments for 17beta-estradiol (E2) and 17alpha-ethynylestradiol (EE2) on selected soils collected from dairy farming regions of New Zealand. Isotherms were constructed by measuring the liquid phase concentration and extracting the solid phase with dichloromethane, followed by an exchange step, and analysis by HPLC and UV detection. The corresponding metabolite estrone, (E1) formed during equilibration of E2 with soil was taken into account to estimate the total percentage recoveries for the compounds, which ranged from 47-105% (E2 and E1) and 83-102% (EE2). Measured isotherms were linear, although some deviation from linearity was observed in a few soils, which was attributed to the finer textured particles and/or the allophanic nature of the soils having high surface area. There was a marked difference in K(d)(eff) (effective distribution coefficient) values for E2 and EE2 among the soils, consistent with the soils organic carbon content and ranged from 14-170 L kg(-1) (E2), and 12-40 L kg(-1) (EE2) in the soils common for both compounds. The sorption affinity of hormones in the soils followed an order: EE2相似文献   
905.
赣江一级支流浮游植物群落动态特征分析——以袁河为例   总被引:1,自引:0,他引:1  
2009年6、11月和2010年4月共3个水情期(即丰、枯和平水期)对赣江下游一级支流袁河的浮游植物群落结构特征开展河流生态学调查分析。调查共发现浮游植物109种,隶属于6门61属。其中绿藻门物种种类数最多,共27属54种,其次为硅藻门,共15属30种,第三是蓝藻门11属12种。此外,裸藻门3属6种,甲藻门3属4种,隐藻门2属3种。调查样点的浮游植物丰度均处于1.12×105~129.20×105 ind./L,丰水期和枯水期浮游植物以蓝藻为优势类群,平水期则硅藻占绝对优势。丰水期浮游植物优势属为脆杆藻属和席藻属,枯水期为栅藻属,针杆属,蓝隐藻属和小环藻属,到了平水期小环藻属占绝对优势。3个水情期中优势种钝脆杆藻和小席藻(丰水期);尖尾蓝隐藻和双头针杆藻(枯水期);梅尼小环藻(平水期)等均为污水指示种。通过生物多样性指数分析发现藻类Shannon-Wiener指数、Simpson指数、Pielou均匀度指数和Margalef丰富度指数的变化范围分别为:1.14~2.92、0.45~0.93、0.36~0.92和0.42~2.78。通过指示生物群落法和生物多样性指数法对袁河进行水质评价发现两种评价结果基本一致,袁河处于α-β-中污染状态,不同采样点间污染程度差异性较大。  相似文献   
906.
Carbon dioxide fluxes from the surface of coarse woody debris (CWD) have been measured in Korean pine forests of the southern Sikhote-Alin mountain range. The seasonal dynamics of oxidative conversion of CWD carbon have been evaluated, and average values of the CO2 emission rate have been determined for CWD fragments of three tree species at different stages of decomposition. The degree of decomposition is an important factor of spatial variation in CO2 emission rate, and temporal variation in this parameter is adequately described by an exponential function of both CWD temperature and air temperature (R2 = 0.65–0.75).  相似文献   
907.
Thallium: a review of public health and environmental concerns   总被引:22,自引:0,他引:22  
Thallium (Tl) is a rare but widely dispersed element. All forms of thallium are soluble enough to be toxic to living organisms. Thallium is more toxic to humans than mercury, cadmium, lead, copper or zinc and has been responsible for many accidental, occupational, deliberate, and therapeutic poisonings since its discovery in 1861. Its chemical behavior resembles the heavy metals (lead, gold and silver) on the one hand and the alkali metals (K, Rb, Cs) on the other. It occurs almost exclusively in natural waters as monovalent thallous cation. The solubility of thallous compounds is relatively high so that monovalent thallium is readily transported through aqueous routes into the environment. Tl can be transferred from soils to crops readily and accrues in food crops. The fascinating chemistry and high toxicity potential make thallium and its compounds of particular scientific interest and environmental concern. Thallium was detected in base-metal mining effluents. The conventional removal of heavy metals from wastewater has little effect on thallium. In this review, various treatment options and removal technologies are enumerated in order to protect the environment from thallium toxicity.  相似文献   
908.
This article measures the changes in energy use, blue water footprint, and greenhouse gas (GHG) emissions associated with shifting from current US food consumption patterns to three dietary scenarios, which are based, in part, on the 2010 USDA Dietary Guidelines (US Department of Agriculture and US Department of Health and Human Services in Dietary Guidelines for Americans, 2010, 7th edn, US Government Printing Office, Washington, 2010). Amidst the current overweight and obesity epidemic in the USA, the Dietary Guidelines provide food and beverage recommendations that are intended to help individuals achieve and maintain healthy weight. The three dietary scenarios we examine include (1) reducing Caloric intake levels to achieve “normal” weight without shifting food mix, (2) switching current food mix to USDA recommended food patterns, without reducing Caloric intake, and (3) reducing Caloric intake levels and shifting current food mix to USDA recommended food patterns, which support healthy weight. This study finds that shifting from the current US diet to dietary Scenario 1 decreases energy use, blue water footprint, and GHG emissions by around 9 %, while shifting to dietary Scenario 2 increases energy use by 43 %, blue water footprint by 16 %, and GHG emissions by 11 %. Shifting to dietary Scenario 3, which accounts for both reduced Caloric intake and a shift to the USDA recommended food mix, increases energy use by 38 %, blue water footprint by 10 %, and GHG emissions by 6 %. These perhaps counterintuitive results are primarily due to USDA recommendations for greater Caloric intake of fruits, vegetables, dairy, and fish/seafood, which have relatively high resource use and emissions per Calorie.  相似文献   
909.
Key performance indicators (KPIs) are critical measures for determining the health of a manufacturing plant in relationship to the plant’s goals. In today’s competitive environment, manufacturers cannot be careless about their business; in fact, they must ensure that their KPIs are effective and use them to make improvements when necessary. This paper describes a method for suggesting improvements to a manufacturer’s KPIs, based on the results achieved from a workshop to score the KPI on a number of predefined criteria. The approach uses a prospect theory approach to weight the scoring. Different problem formulations were derived that allow for both recommendations for improvements and the recommendations for disinvestments to over-performing KPIs. The authors applied the developed approach to two workshop outputs, each from independent manufacturers, and the results highlighted the significant difference between the two manufacturers in terms of improvement priorities and KPI assessment. The optimal improvement suggestions were compared to those found through a fast heuristic. It was determined that given the underlying assumptions of the approach that the heuristic solutions were just as adequate as the optimal ones.  相似文献   
910.
Heat waves and heat-related stresses are increasing environmental concerns in urban areas. The impact of heat waves is dependent on the intensity and duration of each event and on underlying environmental and socio-demographic factors which influence population vulnerability. In order to develop effective adaptation strategies, it is important to develop a method to clearly identify the most vulnerable areas based on these factors. The purpose of this study is to develop and map a heat wave vulnerability index combined with heat exposure analysis to identify areas where interventions can be targeted. The vulnerability index was derived from a principle component analysis of eight key variables that influence heat wave vulnerability. Eight proxy measures of vulnerability were obtained from 2010 census and land-use data for the 1904 census districts of Osaka City. Three principle components explained >77 % of the variance (age, employment and education; social isolation; density and lack of green space). The components were combined and weighted to produce a vulnerability score for each census district. The vulnerability scores ranged from 0 to 106, were categorised into eight vulnerability levels and were overlaid with fine-scale air temperature observations. The resulting output identified the distribution of population vulnerability and exposure. This assessment of vulnerability, combining exposure and sensitivity components, can provide precedent for efficient, targeted action to be taken to reduce the impact of heat waves at present and under climate change.  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