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   2092篇
  免费   511篇
  国内免费   177篇
安全科学   146篇
废物处理   103篇
环保管理   148篇
综合类   1096篇
基础理论   364篇
污染及防治   607篇
评价与监测   80篇
社会与环境   108篇
灾害及防治   128篇
  2025年   1篇
  2024年   17篇
  2023年   47篇
  2022年   99篇
  2021年   77篇
  2020年   76篇
  2019年   70篇
  2018年   84篇
  2017年   98篇
  2016年   108篇
  2015年   129篇
  2014年   146篇
  2013年   181篇
  2012年   116篇
  2011年   140篇
  2010年   109篇
  2009年   101篇
  2008年   124篇
  2007年   130篇
  2006年   85篇
  2005年   87篇
  2004年   67篇
  2003年   103篇
  2002年   102篇
  2001年   80篇
  2000年   83篇
  1999年   58篇
  1998年   46篇
  1997年   59篇
  1996年   31篇
  1995年   29篇
  1994年   28篇
  1993年   21篇
  1992年   16篇
  1991年   9篇
  1990年   8篇
  1989年   4篇
  1988年   6篇
  1987年   3篇
  1983年   1篇
  1981年   1篇
排序方式: 共有2780条查询结果,搜索用时 15 毫秒
101.
    
Many studies have shown soil degradation after the conversion of native forests to exotic Eucalyptus plantations. However, few studies have investigated the long-term impacts of short-rotation forestry practices on soil microorganisms. The impacts of Eucalyptus successive rotations on soil microbial communities were evaluated by comparing phospholipid fatty acid (PLFA) abundances, compositions, and enzyme activities of native Pinus massoniana plantations and adjacent 1st, 2nd, 3rd, 4th generation Eucalyptus plantations. The conversion from P. massoniana to Eucalyptus plantations significantly decreased soil microbial community size and enzyme activities, and increased microbial physiological stress. However, the PLFA abundances formed "U" shaped quadratic functions with Eucalyptus plantation age. Alternatively, physiological stress biomarkers, the ratios of monounsaturated to saturated fatty acid and Gram+ to Gram- bacteria, formed "∩" shaped quadratic functions, and the ratio of cy17:0 to 16: 1ω7c decreased with plantation age. The activities of phenol oxidase, peroxidase, and acid phosphatase increased with Eucalyptus plantation age, while the cellobiobydrolase activity formed "U" shaped quadratic functions. Soil N:P, alkaline hydrolytic nitrogen, soil organic carbon, and understory cover largely explained the variation in PLFA profiles while soil N:P, alkaline hydrolytic nitrogen, and understory cover explained most of the variability in enzyme activity. In conclusion, soil microbial structure and function under Eucalyptus plantations were strongly impacted by plantation age. Most of the changes could be explained by altered soil resource availability and understory cover associated with successive planting of Eucalyptus. Our results highlight the importance of plantation age for assessing the impacts of plantation conversion as well as the importance of reducing disturbance for plantation management.  相似文献   
102.
新疆油田公司稠油污水处理普遍采用成熟的离子调整旋流反应水处理技术,污水处理后达到回用锅炉水质标准SY/T 0097-2000《稠油油田采出水用于蒸汽发生器给水处理设计规范》,供给油田专用高压注汽锅炉用水。采用相同技术建成的采油一厂稠油处理站污水回用锅炉处理工艺投用后,处理后污水回用锅炉,减少了含油污水的外排,充分利用了稠油污水的热能,取得了良好的经济和社会效益。  相似文献   
103.
104.
陶瓷微滤膜过滤黑液的清洗与再生   总被引:4,自引:0,他引:4  
对无机陶瓷微滤膜过滤草桨黑液的膜清洗及再生的方法进行了研究。考察了物理和化学方法的再生效果、单种清洗剂的清洗效果、复合方法的清洗效果和效果的可重复性。结果表明物理冲洗、高温灼烧、单一的化学清洗剂清洗均可以提高陶瓷膜的再生通量;但是复合方法对陶瓷微滤膜的再生效果较好,其中按氢氧化钠溶液清洗、硝酸溶液清洗、次氯酸钠溶液清洗的实验步骤,膜的再生渗透通量高.且重复性强,可望在工业生产的在线清洗中应用。  相似文献   
105.
    
We have created a new method of ZnS nanospheres synthesis. By interface-mediated precipitation method (IMPM), monodisperse ZnS nanoparticles was synthesized on the particle surface of sulfate-reducing bacterium nutritious agar culture. Sulfate-reducing bacterium (SRB) was used as a sulfide producer because of its dissimilatory sulfate reduction capability, meanwhile produced a variety of amino acids acting as templates for nanomaterials synthesis. Then zinc acetate was dispersed into nutritious agar plate. Subsequently agar plate was broken into particles bearing much external surface, which successfully mediated the synthesis of monodisperse ZnS nanoparticles. The morphology of monodisperse ZnS nanospheres and SRB were examined by scanning electron microscopy (SEM), and the microstructure was investigated by X-ray diffraction (XRD). The thermostability of ZnS nanoparticles was determined by thermo gravimetric-differential thermo gravimetric (TG-DTG). The maximum absorption wavelengh was analysed with an ultravioletvisible spectrophotometer within a range of 199-700 nm. As a result, monodisperse ZnS nanoparticles were successfully synthesized, with an average diameter of 80 nm. Maximum absorption wavelengh was 228 nm, and heat decomposed temperature of monodisperse ZnS nanoparticles was 596℃.  相似文献   
106.
107.
印刷线路板厂含铜污泥固化处理工艺研究   总被引:10,自引:0,他引:10  
石太宏  汤兵 《环境工程》2000,18(3):47-49
研究采用水泥作固化基材固化处理某印刷线路板厂酸性废水用石灰混凝所产生的含铜、锡、金的污泥 ,对固化块在不同 pH的水中重金属Cu2 +的浸出实验结果表明 :水泥固化处理该混凝污泥效果良好 ,控制合适的条件 ,可得到混合性能好、初凝时间适当、抗压强度较好的固化块。Cu2 +的浸出率低于允许浸出浓度。混凝过程中加入硫脲硅酸钠等助剂 ,可提高固化效果。研究还对几种不同配比的固化块抗压强度进行了探讨。  相似文献   
108.
    
Fog harvesting is useful for passively collecting fresh water in arid regions, but the efficiency of current mesh‐based harvesters is compromised by their poor drainage. Inspired by the linear needles of redwood trees, “fog harps” are developed whose array of vertical wires enables an unobstructed drainage pathway. A full‐scale (1 m2 frame) fog harp is fabricated by winding a stainless steel wire around a spinning aluminum frame featuring threaded rods. The fog harp is field tested for a full year at a local farm (Blacksburg, VA, USA), alongside the control case of a mesh harvester. Under moderate fog conditions, the fog harp collects anywhere from 2 to 78 times more water compared to the mesh harvesters. Under light fog conditions, the fog harp collects up to several hundred milliliters of water per day while the mesh is unable to collect any water at all. The water harvesting performance of fog harps is therefore unprecedented in two ways: they substantively elevate the performance ceiling when exposed to healthy fog while also enabling, for the first time, appreciable water harvesting under light fog.  相似文献   
109.
本文目的是研究对羟基苯甲酸丙酯(羟苯丙酯;propylparaben,PP)和对羟基苯甲酸丁酯(羟苯丁酯;butylparaben,BP)对大鼠肝微粒体(rat liver microsomes,RLM)和人肝微粒体(human liver microsomes,HLM)细胞色素P450酶(cytochrome P450 enzyme,CYP)活性的抑制作用,并评价它们的相互作用潜能。在体外将系列浓度的羟苯丙酯和羟苯丁酯与大鼠和人肝微粒体孵育60 min,以非那西丁、安非他酮、甲苯磺丁脲、氯唑沙宗、香豆素、右美沙芬和咪达唑仑为CYP探针底物,应用质谱定量检测各探针底物的代谢产物生成量,计算得到IC50Ki值,评价2种化学受试物对大鼠和人肝微粒体CYP450酶的抑制活性和抑制类型,并对抑制强度进行分级。大鼠和人肝微粒体中羟苯丙酯是CYP1A2酶的中等强度抑制剂,羟苯丁酯在大鼠肝微粒体中是CYP1A2酶的弱抑制剂,在人肝微粒体中是CYP1A2酶的中等强度抑制剂,观察到对其他CYP450酶无抑制作用,这与用软件预测的羟苯丙酯和羟苯丁酯对CYP450酶的抑制种类结果一致,分子对接的结果也印证了羟苯丙酯和羟苯丁酯对CYP1A2酶活性的抑制作用,按照构效关系和同源CYP的物种敏感度预测模型,本文关于CYP的研究结果可以类推到其他哺乳动物和人类。  相似文献   
110.
This study investigated the soil nematode community structure along the Yellow River in the Lanzhou area of China, and analyzed the impact of heavy metals (Cd, Pb, Cr, Cu, and Zn) and polycyclic aromatic hydrocarbons (PAHs) on the nematode community. Soil samples from five locations (named A–E), which were chosen for soil analysis, showed significant differences in their heavy metal content (p < 0.01), as well as in the variety of nematodes (up to 41 genera) and families (up to 20) that were present. The different samples also differed significantly in the total PAH content (p < 0.05), as well as the six types of PAH present. Sites A–C showed the most severe contamination with heavy metals and PAHs; these sites had the lowest abundance of fungivores and omnivore/predators, but the proportion of bacteriovores was the highest (p < 0.05). Site E, in contrast, showed only minor pollution with heavy metals and PAHs, and it contained the highest abundance of plant parasites (p < 0.05). Several nematode ecological indicators were found to correlate with concentration of soil pollutants at all the sites tested: the maturity index (MI, in addition to plant parasites), plant parasite index (PPI), ΣMI (including all the soil nematodes), Shannon-Wiener diversity index (H′′), and Wasilewska index (WI). Disturbance to the soil environment was more severe when MI, ΣMI, and H′ values were lower. The results of the study show that the abundance and structure of the soil nematode communities in the sampling locations were strongly influenced by levels of heavy metals and PAHs in the soil. They also show that the diversity index H′ and the maturity index can be valuable tools for assessing the impact of pollutants on nematodes.  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