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   12767篇
  免费   89篇
  国内免费   1182篇
安全科学   174篇
废物处理   963篇
环保管理   1456篇
综合类   2654篇
基础理论   3599篇
污染及防治   2959篇
评价与监测   1104篇
社会与环境   994篇
灾害及防治   135篇
  2024年   1篇
  2023年   50篇
  2022年   161篇
  2021年   124篇
  2020年   88篇
  2019年   86篇
  2018年   1568篇
  2017年   1499篇
  2016年   1356篇
  2015年   321篇
  2014年   318篇
  2013年   329篇
  2012年   719篇
  2011年   1625篇
  2010年   914篇
  2009年   808篇
  2008年   1156篇
  2007年   1418篇
  2006年   179篇
  2005年   140篇
  2004年   110篇
  2003年   156篇
  2002年   179篇
  2001年   97篇
  2000年   84篇
  1999年   72篇
  1998年   93篇
  1997年   68篇
  1996年   64篇
  1995年   56篇
  1994年   28篇
  1993年   36篇
  1992年   31篇
  1991年   16篇
  1990年   13篇
  1989年   15篇
  1988年   9篇
  1987年   11篇
  1986年   5篇
  1985年   2篇
  1984年   15篇
  1983年   11篇
  1982年   1篇
  1981年   3篇
  1970年   1篇
  1935年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
122.
Recent publications by Pogge (Global ethics: seminal essays. St. Paul: Paragon House 2008) and by Singer (The life you can save: acting now to end world poverty. New York: Random House 2009) have resuscitated a debate over the justifiability of famine relief between Singer and ecologist Garrett Hardin in the 1970s. Yet that debate concluded with a general recognition that (a) general considerations of development ethics presented more compelling ethical problems than famine relief; and (b) some form of development would be essential to avoiding the problems of growth noted by Hardin. Better than renewing the debate, we should recognize two points. First, food needs do indeed evoke a moral response that is more direct and compelling than the philosophical positions often generated to rationalize a duty to bring aid. As such the argument for feeding hungry people cannot be generalized into a paradigm for development ethics without distortions that undercut the morally valid elements in Singer’s original argument. Second, contrary to prevailing assumptions in present day development ethics, food aid and famine relief continue to be important priorities for international agencies, notably the World Food Program. Emergency food assistance, the nominal topic of Singer’s original article, thus is an important issue for agricultural as well as development ethics, though one that should indeed be seen as distinct from more complex duties to address the conditions of chronic poverty and underdevelopment.  相似文献   
123.

Purpose  

To protect the environmental quality of soil, groundwater, and surface water near the landfill site, it is necessary to make an accurate assessment of the heavy metal mobility. This study aims to present the bio-immobilization behavior of heavy metals in landfill and provide some reference suggestion for the manipulation of heavy metal pollution control after closure.  相似文献   
124.
Two fresh refuse bioreactors (F1 and F2) were operated under semi-aerobic and anaerobic conditions, respectively. The leachate from the bioreactors F1 and F2 was introduced into the aged refuse bioreactors (A1 and A2), and the effluent from A1 and A2 was subsequently recirculated into F1 and F2, respectively. The effect of the semi-aerobic recirculation process on refuse degradation was investigated, comparing it with that of the anaerobic recirculation process. Results indicate that the semi-aerobic recirculation process can increase the accumulated net production of leachate and promote evaporation. The accumulated net production of refuse in F1 is 320 mL/kg and that of F2 is 248 mL/kg, with leachate reduction amounting to 315 and 244 mL/kg refuse, respectively. The leachate quantity reduction of semi-aerobic and anaerobic leachate recirculation process accounted for 98.4% and 98.3% of the accumulated net production of leachate, respectively. The semi-aerobic leachate recirculation process can improve the biodegradation of organic matter from fresh refuse and the reduction rate of the pollutant concentration in leachate. This should shorten considerably the time required to meet the discharge standard and the time of stabilization of the refuse as observed in the anaerobic recirculation process. It was predicted that the COD concentration of leachate from the anaerobic recirculation process would reach 1000 mg/L in the anaerobic recirculation process after 2.2 years, as for semi-aerobic leachate recirculation process it is about 100 days. Compared with anaerobic recirculation process, the semi-aerobic recirculation process is more effective on NH3-N transformation and TN removal. The NH3-N and TN concentration of F1 is far below those of F2 at the end of our experiment. Refuse settlement in the semi-aerobic recirculation process was faster than that in the anaerobic recirculation process. At the end of the experiment, refuse settlement ratios in the semi-aerobic and anaerobic bioreactors were 33.5% and 18%, respectively.  相似文献   
125.
The circular economy has been developing rapidly in recent years in China. A legislative system has been created to provide legal protection for the development of a circular economy, including a series of price and tax measures in the waste management area. These measures form the basic foundation for promoting better waste management under the circular economic model. Many challenges, however, remain. For instance, the legal system needs to incorporate more sophisticated science, and China lacks key waste treatment technology that could support the further development of a circular economy. There is also a need to educate the public about the concept of the circular economy and its benefits. Specific suggestions are made for the development and implementation of the circular economic model.  相似文献   
126.
Effective handling of municipal digested sludge requires that the product cake have low water content. To this end, we investigated the change in sludge dewaterability after the addition of fly ash to municipal digested sludge, dewatering of which is difficult because of its high organic content. The performance of the dewatering is compared with that of electroosmotic dewatering (EDW) and conventional mechanical dewatering (CMD). Fly ash classified by sieving to the size of 25–75 μm and >75 μm is added to the municipal digested sludge by 10, 20, and 50 wt% by wet base. When adding fly ash particles to municipal digested sludge, dewatering efficiency improved with smaller fly ash particle size and with increase in the amount. When sludge was dewatered using an electroosmotic dewatering method, the dewatering efficiency is improved about 40% by adding fly ash of 25–75 μm particle size with 20 wt% when compared with conventional mechanical dewatering method without adding the fly ash. It is concluded that fly ash particles rich in inorganic material are helpful in the dewatering process when added to municipal digested sludge and EDW is more effective than CDW.  相似文献   
127.
In this study the possibility of poly (3-hydroxybutyrate) production from glycerol was investigated and optimized by Halorcula sp. IRU1, a novel archaea isolated from Urmia lake, Iran in batch experiments. Using Taguchi methodology, three important independent parameters (glycerol, yeast extract and KH2PO4) were evaluated for their individual and interactive effects on poly (3-hydroxybutyrate) production. It was shown that the glycerol concentration was the most significant factor affecting the yield of poly (3-hydroxybutyrate). The optimum factor levels were a glycerol concentration of 8% (v/v), yeast extract 0.8% (w/v) and KH2PO4 0.002% (w/v). The predicted value obtained for poly (3-hydroxybutyrate) production under these conditions was about 81.87%. We can conclude that Haloarcula sp. IRU1 has a high potential for synthesis of poly (3-hydroxybutyrate) from glycerol.  相似文献   
128.
Investigations have continued for production high performance agro-based composites using environmentally acceptable approaches. This study examines the role of adding amide-containing biopolymers during synthesis of urea–formaldehyde (UF) on properties of adhesive produced, especially its adhesion potential. The environmental performance of UF-resin synthesized in the presence of modified amide-containing biopolymer was evaluated by evaluating the free-HCHO of both adhesive (during processing) and of the eventual engineered composite product. Also, the benefits of this synthesis-modified adhesive in enhancing the bondability of sugar-cane fibers used in engineered composite panels was evaluated and compared to using UF-resin. The results obtained show that, static bending of the produced composites varied from 27.7 to 33.13 N/mm2 of modulus of rupture (MOR) and from 2860 to 3374 N/mm2 of Modulus of Elasticity (MOE); while for internal bond (IB) it’s varied from 0.64 to 0.866 N/mm2. Based on the ANSI and EN Standards modified UF-based agro composites produced meet the performance requirements for high grade particleboards with respect to static bending strength. These agro-based composite also tested out as having free-HCHO values of ~13 mg/100 g board.  相似文献   
129.
The study was carried out to investigate the effects of filler content and two different compatibilizing agents (Eastman G-3003 and G-3216) on the mechanical properties of polypropylene reinforced with corn stalk and wood flour. In the sample preparation, three levels of filler loading (30, 40 and 50 wt%) and one level of compatibilizing agent content (2.5 wt%) were used. For overall trend, with addition of both grades of the compatibilizing agents, tensile and flexural properties of the composites significantly improved, as compared with the pure PP. Tensile and flexural properties reach a maximum at 40 wt% filler content and gradually decrease with a further increase in wood particle content. The composites treated with G-3003 gave better results in comparison with G-3216. This could be caused by the high melt viscosity of G-3003. In general, corn stalk flour filled composites showed superior mechanical properties.  相似文献   
130.
Plasticized starch (PLS) is a renewable, degradable, and inexpensive polymer, but it suffers from poor mechanical properties. The mechanical properties can be improved by blending PLS with polyolefins, nonetheless, at high PLS content, the mechanical properties remain poor. Here we show that addition of clay can greatly improve the mechanical properties of PLS/polypropylene blends at high starch content. Unmodified and organically modified montmorillonite clays, MMT and Cloisite 30B respectively, were added to blends of glycerol-plasticized starch and polypropylene, compatibilized using maleated polypropylene. TEM indicates that MMT is well dispersed in the PLS phase of the blends, while Cloisite 30B is located both within the PLS phase as well as at the interface between PLS and PP. At high PLS content, the addition of clay increased the tensile strength and tensile modulus by an order of magnitude, while reducing the ultimate elongation only slightly. Such improvements are attributable to both the addition of clay as a reinforcing component, as well as to the change in the two phase morphology due to addition of clay.  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