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   1073篇
  免费   137篇
  国内免费   198篇
安全科学   148篇
废物处理   57篇
环保管理   105篇
综合类   585篇
基础理论   267篇
环境理论   7篇
污染及防治   104篇
评价与监测   61篇
社会与环境   53篇
灾害及防治   21篇
  2024年   2篇
  2023年   19篇
  2022年   27篇
  2021年   38篇
  2020年   49篇
  2019年   49篇
  2018年   82篇
  2017年   74篇
  2016年   69篇
  2015年   65篇
  2014年   89篇
  2013年   157篇
  2012年   51篇
  2011年   61篇
  2010年   46篇
  2009年   41篇
  2008年   38篇
  2007年   52篇
  2006年   58篇
  2005年   43篇
  2004年   46篇
  2003年   33篇
  2002年   35篇
  2001年   30篇
  2000年   28篇
  1999年   8篇
  1998年   10篇
  1997年   13篇
  1996年   16篇
  1995年   19篇
  1994年   7篇
  1993年   8篇
  1992年   6篇
  1991年   6篇
  1990年   4篇
  1989年   4篇
  1988年   2篇
  1987年   5篇
  1986年   3篇
  1985年   5篇
  1984年   2篇
  1983年   5篇
  1982年   1篇
  1981年   2篇
排序方式: 共有1408条查询结果,搜索用时 15 毫秒
91.
随着人们生活水平的提高,服装更新速度越来越快,废旧衣服既污染环境,其再利用价值也没有发挥出来.把循环经济中的“3R原则”应用到废旧衣服回收中,以发挥废旧衣服的最大价值.  相似文献   
92.

The overall objective of this study was to evaluate the potential ability of nitrocompounds to reduce ammonia volatilization by inhibiting uric acid–utilizing microorganisms. Experiment I was conducted to evaluate the effects of nitrocompounds on the growth of uric acid–utilizing microorganisms isolated from poultry manure during six-hour incubation. There were five treatments: (1) control, (2) 50 mM nitroethane, (3) 50 mM nitroethanol, (4) 50 mM nitropropanol, and (5) 50 mM nitropropionic acid. Optical density values of nitrocompounds were significantly lower than that of control at two, four, and six hours. Plate counts of uric acid–utilizing microorganisms after six-hour incubation exhibited that nitrocompounds greatly reduced the growth of these microorganisms except for the nitroethane (P < 0.05). The nitropropanol and nitropropionic acid treatments showed significantly higher inhibitory effects compared to the nitroethanol. Experiments II and III were conducted to evaluate inhibitory effects of nitrocompounds on growth of uric acid–utilizing microorganisms compared to non-nitrocompounds such as ethanol, propanol, and propionic acid. Experiments II and III consisted of seven treatments: (1) control, (2) nitroethanol, (3) nitropropanol, (4) nitropropionic acid, (5) ethanol, (6) propanol, and (7) propionic acid. The incubation times of Experiments II and III were 6 and 24 h, respectively. The nitrocompounds were significantly more successful in inhibiting growth of uric acid–utilizing microorganisms compared to those non-nitrocompounds. These results suggest that nitrocompounds exhibit potential to reduce ammonia volatilization in poultry manure by inhibiting growth of uric acid–utilizing microorganisms.  相似文献   
93.
The high‐performance liquid‐chromatographic retentions of red‐wine pesticide residues are modeled by structure–property relationships. The effect of different types of features is analyzed: geometric, lipophilic, etc. The properties are fractal dimensions, partition coefficient, etc., in linear and nonlinear correlation models. Biological plastic evolution is an evolutionary perspective conjugating the effect of acquired characters and relations that emerge among the principles of evolutionary indeterminacy, morphological determination and natural selection. It is applied to design the co‐ordination index that is used to characterize pesticide retentions. The parameters used to calculate the co‐ordination index are the molar formation enthalpy, molecular weight and surface area. The morphological and co‐ordination indices barely improve the correlations. The fractal dimension averaged for non?buried atoms, partition coefficient, etc. distinguishes the pesticide molecular structures. The structural and constituent classification is based on nonplanarity, and the number of cycles, and O, S, N and Cl atoms. Different behavior depends on the number of cycles.  相似文献   
94.
The paper examines trends in the average copper content of mined ores over the years. It has tended to decline over the long term, but by no means evenly. US averages are not typical of global averages, at least in the past four decades. Those have been both higher, and less volatile than in the US. One reason for falling averages is a change in the type of deposit mined, with a rise in the share of relatively low grade porphyry deposits. The different nature of their deposits is reflected in marked differences in grades between the different continents. African and Australian average grades are higher than the global average, and changes in the share of Central Africa in global output have affected the global average grade. Yields are have been consistently lower in North America than elsewhere, and Latin American average grades have trended downwards, reflecting both the ageing of mines and the rising share of production from porphyry deposits. Typically the yield of mines declines over time as mining proceeds. The average copper content of ore deposits is usually below the average yield of the ore accessed in the early years of production. The initial grades of new mines have not declined over the past forty years, and there has been no perceptible tendency for the average grade of porphyry deposits brought into production to decline over time. There is no apparent correlation between average grade and deposit size, but mine operators tend to exploit economies of scale to offset low grades. The relationship between the annual percentage yields (the head grade) and the reserve grades of deposits is not static. In recent years head grades have fallen closer to reserve grades. The relationship may be affected by movements in metal prices. Although the evidence about the influence of prices is not clear-cut, it does suggest that prices and cut-off grades may be inversely related. As many ores contain other valuable metals besides copper, copper yields will sometimes be subordinated to the extraction of these other metals. Copper equivalent grades have not moved in the same way as copper grades alone.  相似文献   
95.
This paper critically reflects on the challenges of engaging, proactively, in Corporate Social Responsibility (CSR) in oil-rich sub-Saharan Africa. Most of the region's oil production takes place in enclave-type environments offshore and in countries ruled by autocratic governments which generally exert minimal pressure on companies to embrace CSR. With companies having little sense of who to target in their local economic development policies and programs, there is always a possibility of ‘offshore CSR’ – recognized here as potentially-effective ideas for improving social welfare that linger within the enclave and never fully materialize – surfacing. The aim is to conceptualize and broaden understanding of the challenge of developing CSR programs in these settings, where there are no clear linkages to communities or local economies more generally.  相似文献   
96.
Xu Z  Deng S  Yang Y  Zhang T  Cao Q  Huang J  Yu G 《Chemosphere》2012,87(9):1032-1038
Pentachlorobenzene (PeCB) in simulated flue gas was destructed by a commercial V2O5-WO3/TiO2 catalyst in this study. The effects of reaction temperature, oxygen concentration, space velocity and some co-existing pollutants on PeCB conversion were investigated. Furthermore, a possible mechanism for the oxidation of PeCB over the vanadium oxide on the catalysts was proposed. Results show that the increase of gas hourly space velocity (GHSV) and the decrease of operating temperature both resulted in the decrease of PeCB removal over the catalyst, while the effect of the oxygen content in the range of 5-20% (v/v) on PeCB conversion was negligible. PeCB decomposition could be obviously affected by the denitration reactions under the conditions because of the positive effect of NO but negative effect of NH3. The introduction of SO2 caused the catalyst poisoning, probably due to the sulfur-containing species formed and deposited on the catalyst surface. The PeCB molecules were first adsorbed on the catalyst surface, and then oxidized into the non-aromatic acyclic intermediates, low chlorinated aromatics and maleic anhydride.  相似文献   
97.
98.
樊丽  徐龙君  王辉 《环境工程学报》2012,6(8):2809-2812
为考察较低温度(<17℃)条件下添加微量金属元素对厌氧发酵产气量的影响,在发酵底物TS(含固率)为10%下采用10 L玻璃瓶作反应器,以牛粪为原料,向厌氧生物反应器中分别添加MnSO4、FeSO4·7H2O、电解锰渣,分析了厌氧消化系统运行过程中的产气量、COD(化学需氧量)和pH的变化。结果表明,锰元素能促进低温下牛粪的厌氧发酵,加速反应启动。当添加6 g MnSO4、100 g电解锰渣时,单位质量VS产气率分别为0.26 mL/g和0.64 mL/g,添加6 g FeSO4·7H2O与空白对照组均未见明显产气。  相似文献   
99.
利用实验室小试SBR在(33±1)℃的条件下,通过动态调控溶氧浓度(DO)(2~7 mg/L)和水力停留时间(2~5 d),经过130 d的运行成功启动了晚期垃圾渗滤液(NH4+-N含量1 227~2 133 mg/L)的部分亚硝化,使出水NO2--N∶NH4+-N稳定维持在1∶1左右,为后续的厌氧氨氧化工艺创造了进水条件。利用实时荧光定量PCR研究启动过程中的特异微生物氨氧化细菌的含量变化表明,氨氧化细菌的含量与NO2--N的生成速率和出水NO2--N稳定性有着显著相关性。  相似文献   
100.
珠芽魔芋种子5苗接力生长当年形成商品芋技术   总被引:1,自引:0,他引:1  
首次提出珠芽魔芋种子具有5苗接力生长的生物学特性。种子能在一个不间断的生长周期中积累最大生物产量,避免魔芋需反复"换头"种植3—4年才能收获商品芋的低产生长模式,使魔芋的膨大系数由块茎的低于10倍提高到种子最高约7000倍,所获地下球茎重量平均达1560g。采用种子种植当年即可获用于加工的商品芋,消除了魔芋种植过程中固有的风险,使魔芋由低产作物变成高产作物,魔芋多糖总量将实现跨越式增长。  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