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   1310篇
  免费   144篇
  国内免费   353篇
安全科学   260篇
废物处理   101篇
环保管理   147篇
综合类   781篇
基础理论   141篇
环境理论   1篇
污染及防治   142篇
评价与监测   59篇
社会与环境   23篇
灾害及防治   152篇
  2024年   4篇
  2023年   16篇
  2022年   38篇
  2021年   44篇
  2020年   39篇
  2019年   40篇
  2018年   37篇
  2017年   39篇
  2016年   45篇
  2015年   53篇
  2014年   67篇
  2013年   110篇
  2012年   149篇
  2011年   120篇
  2010年   89篇
  2009年   79篇
  2008年   68篇
  2007年   121篇
  2006年   109篇
  2005年   89篇
  2004年   76篇
  2003年   67篇
  2002年   58篇
  2001年   51篇
  2000年   40篇
  1999年   28篇
  1998年   26篇
  1997年   18篇
  1996年   29篇
  1995年   14篇
  1994年   14篇
  1993年   10篇
  1992年   6篇
  1991年   2篇
  1990年   5篇
  1988年   1篇
  1986年   1篇
  1984年   1篇
  1982年   2篇
  1978年   1篇
  1975年   1篇
排序方式: 共有1807条查询结果,搜索用时 312 毫秒
31.
随着开采深度及范围的扩大,邢台煤矿井下高压出水点越来越多,既浪费了大量的排水费用,又对岩溶水环境和水资源造成了严重破坏。针对上述情况,用四种不同的方法分别进行了封堵和重新利用,使矿井减少了480m^3/h的无效排水,经济效益和环保效益均十分明显。  相似文献   
32.
绿色高强混凝土——硅灰混凝土   总被引:4,自引:0,他引:4  
硅灰是冶金厂生产硅铁和工业硅过程中产生的废灰,硅灰混凝土为绿色混凝土,它不仅节约了水泥熟料,而且改善了环境,大大促进了混凝土和建筑工程的健康发展,混凝土中掺入硅灰可得到高强和超高强混凝土,用此混凝土浇制的结构物其安全度大大提高,经济效益显著,硅灰混凝土还可以有效抑制碱骨料反应,提高结构物的安全度和耐久性,延长使用寿命。  相似文献   
33.
测定了25℃时活性炭自水中吸附苯、苯酚、苯胺、对-氯苯酚、苯甲酸、对-羟基苯甲酸、对-氯苯胺、硝基苯、对-氨基苯甲酸、对-硝式苯酚、对-硝基苯胺、对硝基苯甲酸的等温线,它们的等温线均为Langmuir型的,利用Langmuir参数计算了吸吸标准自由能变化△G^0,计算结果表明,△G^0具有加和性,即化合物的△G^0是组成该化合物各基团贡献之总和,化合物的分子量及分子连接性指数与△G^0有近似的线性关系。  相似文献   
34.
The turbidity variation in artificial water and samples from a water plant was investigated in the presence of organics with different relative molecular mass. The results show that recessive turbidity existed when water chemical conditions were changing. The formation of turbidity depended on organic relative molecular mass and their conformations on particles. At higher pH and lower ionic strength, the organic chains with a more extended conformation resulted in rising turbidity of the suspension. At lower pH, the reconformation of organics took place due to charge neutralization by the proton, resulting in a decline in turbidity. The addition of NaCl and MgCl2 at pH 7.00 also resulted in a decrease of turbidity in the suspension. It is believed that the occurrence of recessive turbidity has a significant influence on the stability of water supply quality.  相似文献   
35.
室内空气中甲醛和苯系物检测与净化   总被引:2,自引:0,他引:2  
通过对哈尔滨市装饰装修竣工一年内的60户室内空气污染物检测分析,结果表明:室内空气甲醛超标64.1%,苯超标54.1%,甲苯超标35.6%,二甲苯超标30.6%.采用臭氧法,光催化氧化法和药剂法三种方法对室内空气污染物甲醛和苯进行净化效果实验研究,评价其净化效果,比较了三种方法的优劣.  相似文献   
36.
Biodegradable polyesters were synthesized by ring-opening copolymerization of -butyrolactone (BL) and its derivatives withl-lactide (LLA). Although tetraphenyl tin was the main catalyst used, other organometallic catalysts were used as well.1H and13C NMR spectra showed that poly(BL-co-LLA)s were statistical and that their number-average molecular weights were as high as 7×104. The maximum BL content obtained from copolymerization BL/LLA was around 17%. TheT m andT g values of the copolymers showed a gradual depression with an increase in BL content. NoT m was obtained for the copolymers containing more than 13 mol% BL. The biodegradability of the copolyesters was evaluated by enzymatic hydrolysis and nonenzymatic hydrolysis tests. The enzymatic hydrolysis was carried out at 37°C for 24 h using lipases fromRhizopus arrhizus andR. delemar. Hydrolyses by both lipases showed that an increase in BL content of the copolymer resulted in enhanced biodegradability. Nonenzymatic accelerated hydrolysis of copolymers at 70°C was found to increase proportionally to their exposure time. The hydrolysis rate of these copolymers was considerably faster than that of PLLA. The higher hydrolyzability was recorded for the BL-rich copolymers. The copolymerization of -methyl--butyrolactone (MBL) or -ethyl--butyrolactone (EBL) with LLA resulted in relatively LA-rich copolymers.  相似文献   
37.
根据钢筋混凝土多层框架的设计经验和设计规范,对如何调整电算结果中的梁,柱截面尺寸,配筋率,裂缝宽度和梁,柱配筋等问题进行探讨,并提出相应的建议。  相似文献   
38.
Pork producers in Western Europe moreand more encounter a variety of societalconcerns about pork and pork production. Sofar, however, producers predominantly focusedon low consumer prices, therewith addressingjust one concern. This resulted in an intensiveand large-scale production system, decreasinglyrelated to the area of farm land, andaccompanied with increasing concerns aboutsafety and healthiness of pork, animal welfare,environmental pollution, and others.An overview was given of possible concernsabout West-European pork production with theconsumers, citizens, and producers, and thoseconcerns are traced back to the pork productionsystem. The various kinds and qualities ofinformation about the pork production system onwhich possible concerns are based have beenworked out extensively in this paper. Knowledgeabout the aspects of pork production that cangive rise to concerns can be used in two ways.First, the communication about those aspectstowards consumers and citizens can be adjustedor extended to give them better possibilitiesto make food choices or to develop their ownopinions about pork production. Second,producers could change the pork productionsystem such that it better satisfies consumersand citizens. Such adaptations are wellpossible, as three pork quality schemes, whichhave been evaluated, illustrate. However, mostof these adaptations can only be carried out atthe cost of the present low consumer prices andwill not occur spontaneously on a large scale.Therefore, accounting for the type andrelevance of the concerns, legislation isnecessary to address societal concerns in abalanced way such that pork production systemsbecome acceptable for the majority of oursociety.  相似文献   
39.
火灾中均布荷载作用下钢筋混凝土方板的极限分析   总被引:6,自引:0,他引:6  
本文利用有限差分法确定了火灾时钢筋混凝土板的温度分布,并基于塑性铰线理论确定了火灾时钢筋混凝土方板的破坏机制,根据高温下混凝土和钢筋的力学性能对火灾过程中塑性铰截面的弯矩及板的极限荷载进行了分析,可为建筑结构的耐火设计提供依据。  相似文献   
40.
加碱混凝沉淀工艺在处理含磷废水中的应用   总被引:1,自引:0,他引:1  
介绍了加碱混凝沉淀法处理含磷废水的工艺。采用工艺处理效果好,出水稳定,经监测废水中总磷的去除效率可达96%,实际运行证明,该工艺是切实可行的。  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