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   901篇
  免费   81篇
  国内免费   438篇
安全科学   96篇
废物处理   72篇
环保管理   72篇
综合类   625篇
基础理论   130篇
污染及防治   286篇
评价与监测   38篇
社会与环境   44篇
灾害及防治   57篇
  2024年   11篇
  2023年   20篇
  2022年   75篇
  2021年   75篇
  2020年   66篇
  2019年   50篇
  2018年   47篇
  2017年   65篇
  2016年   67篇
  2015年   67篇
  2014年   58篇
  2013年   69篇
  2012年   64篇
  2011年   79篇
  2010年   71篇
  2009年   68篇
  2008年   67篇
  2007年   42篇
  2006年   49篇
  2005年   49篇
  2004年   46篇
  2003年   16篇
  2002年   17篇
  2001年   17篇
  2000年   30篇
  1999年   23篇
  1998年   19篇
  1997年   25篇
  1996年   17篇
  1995年   13篇
  1994年   12篇
  1993年   6篇
  1992年   4篇
  1991年   1篇
  1990年   7篇
  1989年   1篇
  1988年   1篇
  1986年   5篇
  1985年   1篇
排序方式: 共有1420条查询结果,搜索用时 31 毫秒
71.
With the environmental carrying capacity reaching its limits and the decreasing margin benefits of traditional production factors, the green transformation and green development through technological innovations has been a major direction for the future development of Chinese industries. However, the characteristics and heterogeneities of various types of industries call for different approaches regarding technological innovations. How to choose the most effective mode of technological innovation according to the characteristics of a certain industry has been a key issue. This paper measures the green total factor productivity of 32 industrial trades using the Slacks Based Measure(SBM)-DDF method. The effects of three innovation modes in the green transformation of industrial industry, including the independent innovation(Ⅱ), the technology introduction(TI), and the government support(GS), are empirically analyzed based on industry heterogeneity. Results indicate that the green total factor productivities of different industries show significant differences if taking into account the energy input and the undesirable output of pollutant emissions. The green total factor productivities of traditional high input,high pollution, and high energy consumption industrial trades were significantly lower than those with obvious green features. The year of 2009 is a leap year for the industrial green transformation in China. For resource-intensive industries, the II and the GS are the important ways to achieve green transformation. For labor-intensive industries, the TI is the best path to achieve green transformation, while for technology-intensive industries, the II is the primary driving force for the promotion of green developments. In addition, the innovation-compensating effect of the current Chinese environmental regulations to the resource-intensive industries has been revealed. Improving the overall scale and the industrial concentration of the industries is also beneficial for the green transformation of the industries.  相似文献   
72.
The annual relative mass of storage organs cycle of Bufo gargarizans in southwestern China was studied from December 2005 to November 2006. We described how those organs changed in response to extreme temperatures. Energy reservation dropped to the lowest levels after dormancy for both sexes, and then increased for period of 4.25 month. However, the mass of these organs dropped again rapidly until August (liver) and September (fat bodies) due to the constraint from extreme high temperature occurred during the summer, and then non-significantly increased before hibernation. For ovaries, varied with a different profile to those of liver and fat bodies have a resting period of four months. In addition, the toads’ ovaries kept growing when the mass of liver and fat bodies declining accordingly during hibernation. Therefore, ovarian mass increased during the hibernation and non-hibernation period.  相似文献   
73.
生物难降解有机污染物的治理对策   总被引:11,自引:0,他引:11  
赵庆祥  林哲 《化工环保》1995,15(5):276-279
针对废水中难降解化学合成有机污染物的种类和数量不断增加,生物处理出水达标困难的现状,总结了国内外的经验和研究成果,对现有处理装置改造提出了若干建议,并介绍了几种国外废水处理新技术。  相似文献   
74.
基于长江中下游地区1961~2100年区域气候模式COSMO-CLM(CCLM)模拟与1961~2005年气象站观测的逐日降水数据,通过统计计算年降水量、强降水量、暴雨日数和极端降水贡献率4个极端降水指数,研究全球升温1.5℃与2.0℃情景下,长江中下游地区极端降水的时空变化特征。结果表明:(1)全球升温1.5℃情景下,年降水量相对于1986~2005年减少5%,强降水量、暴雨日数和极端降水贡献率分别增加7%、33%和4%;概率密度曲线表明,年降水量均值下降,强降水量、暴雨日数和极端降水贡献率均值上升,极端降水方差增大;年降水量、强降水量和暴雨日数在空间上表现为南部增加北部减少,极端降水贡献率则相反。(2)全球升温2.0℃情景下,年降水量下降3%,强降水量、暴雨日数和极端降水贡献率分别上升15%、46%和15%;年降水量均值稍有减少且方差稍有上升,强降水量、暴雨日数和极端降水贡献率均值和方差明显增加;年降水量减少区域位于长江主干以北,强降水量、暴雨日数和极端降水贡献率表现为绝大部分地区增加的空间变化特征。(3)全球升温由1.5℃至2.0℃时,年降水量、强降水量、暴雨日数和极端降水贡献率分别增加3%、7%、10%和11%;随升温幅度的增加极端降水均值和方差上升;极端降水呈增加态势的范围扩大。因此,努力将升温控制在1.5℃对降低极端降水的影响具有重要意义。  相似文献   
75.
为讨论表面改性对活性炭吸附特性的影响,用氨改性活性炭对Pb(Ⅱ)的吸附性能进行了研究。通过高温氨气吹扫对活性炭进行表面改性处理,观察了改性后活性炭物化性质的变化,研究了氨改性活性炭对Pb(Ⅱ)的吸附等温关系与动力学,并对吸附前后氨改性活性炭的形貌进行了分析。结果表明,氨改性后活性炭比表面积和总孔孔容均略有增大,活性炭中N元素含量明显增高,含氧官能团数量减少,零电荷点增大。氨改性后活性炭对Pb(Ⅱ)的吸附效果明显提高,吸附过程数据可用等温吸附方程描述,改性后活性炭对Pb(Ⅱ)的吸附符合拟二级动力学。Pb(Ⅱ)在氨改性活性炭表面上的附着明显可见。通过红外光谱分析,活性炭表面含氮官能团与Pb(Ⅱ)发生缔合作用。  相似文献   
76.
Effect of the addition of poly(ethylene glycol) terminated by benzoate (PEG-BA) on the crystallization behavior and dynamic mechanical properties of poly(l-lactic acid) PLLA is studied as compared with poly(ethylene glycol) (PEG-OH). It is found that PEG-BA is miscible with PLLA and shows good plasticizing effect. Because PEG-OH having the same degree of polymerization is immiscible with PLLA, the end group in PEG-BA, i.e., benzoate, plays an important role in the miscibility. Furthermore, PEG-BA does not induce the PLLA degradation at melt-processing, whereas PEG-OH leads to the hydrolysis degradation. Finally, the addition of PEG-BA pronounces the crystallization rate of PLLA at low crystallization temperatures and thus enhances the degree of crystallinity at conventional processing. Consequently, the temperature dependence of dynamic mechanical properties are similar to that for isotactic polypropylene.  相似文献   
77.
Thermal desorption is widely used for remediation of soil contaminated with volatiles, such as solvents and distillates. In this study, a soil contaminated with semivolatile polychlorinated biphenyls (PCBs) was sampled at an interim storage point for waste PCB transformers and heated to temperatures from 300 to 600 °C in a flow of nitrogen to investigate the effect of temperature and particle size on thermal desorption. Two size fractions were tested: coarse soil of 420–841 μm and fine soil with particles <250 μm. A PCB removal efficiency of 98.0 % was attained after 1 h of thermal treatment at 600 °C. The residual amount of PCBs in this soil decreased with rising thermal treatment temperature while the amount transferred to the gas phase increased up to 550 °C; at 600 °C, destruction of PCBs became more obvious. At low temperature, the thermally treated soil still had a similar PCB homologue distribution as raw soil, indicating thermal desorption as a main mechanism in removal. Dechlorination and decomposition increasingly occurred at high temperature, since shifts in average chlorination level were observed, from 3.34 in the raw soil to 2.75 in soil treated at 600 °C. Fine soil particles showed higher removal efficiency and destruction efficiency than coarse particles, suggesting that desorption from coarse particles is influenced by mass transfer.  相似文献   
78.
Some technical issues in managing PCBs   总被引:1,自引:0,他引:1  
Polychlorinated biphenyls (PCBs) were important industrial chemicals featuring high thermal and chemical stability and low flammability. They were widely used as dielectric and thermal fluid in closed electro-technical applications (transformers, capacitors…) and also in numerous dispersive uses, ranking from auto-copying paper to sealant or coatings. During the 1960s, severe environmental consequences started becoming apparent. The stability of PCBs contributed to their persistence in the environment, their lipophilic character to bio-magnification. Fish-eating species seemed threatened in their existence. In Japan and in Taiwan, thousands of people consumed PCB-contaminated oil. The production of PCBs stopped completely during the 1980s. Usage could continue in closed applications only. In this paper, particular attention is given to two issues: the cleaning of PCB electric transformers and the potential impact of PCB-containing building materials. Other contributions will cover the management and treatment of PCB-contaminated soil, sludge or fly ash. The complete survey is being prepared by request of the Knowledge Center for Engineers and Professionals.  相似文献   
79.
孙亚月  佘铜 《化工环保》2014,34(6):590-594
以钠基蒙脱土(MMT)为载体,先采用溶胶-凝胶法将纳米TiO2引入到MMT层间,再采用化学沉积法将纳米Cu2O负载在TiO2/MMT上,制备出TiO2-Cu2O/MMT纳米复合光催化剂。采用XRD、SEM、紫外-可见漫反射技术对催化剂进行了表征。以甲基橙为目标污染物,考察了催化剂的光催化性能。表征结果显示:TiO2与Cu2O均匀分布在MMT的表面与片层孔隙中;TiO2-Cu2O/MMT结合了TiO2和Cu2O的特性,拓宽了催化剂的光吸收范围。实验结果表明,在光源为可见光、初始甲基橙质量浓度为20 mg/L、光催化剂加入量为2 g/L的条件下,TiO2-Cu2O/MMT纳米复合光催化剂对甲基橙的光催化降解效果明显优于单一负载的Cu2O/MMT和TiO2/MMT,大幅提高了催化剂的光催化效率,反应300 min时TiO2-Cu2O/MMT对甲基橙溶液的脱色率达到93%。  相似文献   
80.
石化行业的VOCs排放控制管理   总被引:2,自引:0,他引:2  
郭森  童莉  周学双  韩建华 《化工环保》2014,34(4):356-360
概述了我国挥发性有机化合物(VOCs)的排放情况。介绍了国内外VOCs的管理现状。分析了国内石化行业VOCs排放控制管理中存在的主要问题以及污染物排放过程的类别。提出了明确定义、制定相关标准、完善分类管理体系、研究最佳的可行性控制技术等加强VOCs排放控制管理的对策和建议。  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