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   715篇
  免费   54篇
  国内免费   202篇
安全科学   107篇
废物处理   38篇
环保管理   62篇
综合类   465篇
基础理论   124篇
污染及防治   89篇
评价与监测   47篇
社会与环境   19篇
灾害及防治   20篇
  2024年   2篇
  2023年   3篇
  2022年   13篇
  2021年   16篇
  2020年   18篇
  2019年   10篇
  2018年   20篇
  2017年   21篇
  2016年   25篇
  2015年   30篇
  2014年   28篇
  2013年   59篇
  2012年   72篇
  2011年   51篇
  2010年   46篇
  2009年   51篇
  2008年   46篇
  2007年   65篇
  2006年   76篇
  2005年   42篇
  2004年   41篇
  2003年   32篇
  2002年   34篇
  2001年   31篇
  2000年   26篇
  1999年   25篇
  1998年   22篇
  1997年   11篇
  1996年   14篇
  1995年   7篇
  1994年   8篇
  1993年   6篇
  1992年   4篇
  1991年   4篇
  1990年   4篇
  1989年   1篇
  1988年   2篇
  1986年   2篇
  1983年   1篇
  1982年   1篇
  1976年   1篇
排序方式: 共有971条查询结果,搜索用时 15 毫秒
881.
生活垃圾卫生填埋场填埋库区分期设计实例   总被引:1,自引:0,他引:1  
邱香贵 《环境工程》2010,28(4):76-78
提出山谷型生活垃圾卫生填埋场填埋库区采取分期设计的原则,以福建省连城县生活垃圾卫生填埋场为例,说明填埋库区采取分期设计后能有效地减少垃圾渗滤液的产生量,从而达到减少工程投资、加快工程进度、减少初期运行费用的目的。  相似文献   
882.
模拟酸雨淋溶下红壤中盐基离子释放及缓冲机制研究   总被引:10,自引:0,他引:10  
通过模拟酸雨淋溶实验,分析在不同酸度酸雨淋溶下红壤中盐基离子释放的规律和特点,研究红壤对酸雨的缓冲机制.结果表明:红壤对酸雨的缓冲主要可分为初级和次级2个缓冲体系,其盐基离子释放主要受H+输入量控制.当H+输入量少时,红壤对酸雨的缓冲以初级缓冲体系交换盐基离子为主;随着H+输入增多,红壤对质子的缓冲进入矿物风化阶段.酸度大的酸雨对红壤的矿物风化作用相对较大.不同酸度酸雨淋溶下,各盐基离子释放量最终趋于稳定.盐基离子对酸雨的敏感性顺序为Ca2+>Mg2+>K+>Na+.结果还表明,Ca2+与Mg2+的释放显著线性相关,n(Ca2+)/n(Mg2+)随酸雨pH和淋溶量增加而增大.强酸性酸雨淋溶下红壤矿物风化所导致的Na+释放的机理和来源可能与K+,Ca2+和Mg2+的不同.   相似文献   
883.
本文以现代管理学理论为基础,主要阐述了现代台站管理思想 --一方面强调"以人为本",另一方面又肯定以"法"治台;提出了二者的有机结合是现代台站管理思想这一主题;初步探讨了当代地震台站提高监测质量的途径.  相似文献   
884.
关于实行企业安全生产年审制的思考   总被引:1,自引:0,他引:1  
在经济体制改革后 ,政府转变职能 ,企业转换经营机制 ,企业与政府脱钩 ,政府放权予企业 ,由企业自主经营、自负盈亏 ,企业成为独立核算的法人。按照权、责统一和管生产必须管安全、谁主管谁负责的原则 ,企业的安全生产从企业与政府共同管理转移到自主管理 ,政府及其有关主管部门从管理向监督转变 ,政府与企业的关系由隶属关系变成监督与被监督的关系。随着社会主义市场经济的进一步发展和日益完善 ,安全生产面临前所未有的新情况。在新的形势下 ,如何建立安全生产的长效机制 ,是当前安全生产亟待解决的重要课题。笔者针对安全生产监督与管理上存在的问题 ,有针对性地提出了实行企业安全生产年审制的建议 ,认为建立企业安全生产年审制是切合当前实际的安全对策 ,并对如何实施这一对策进行了初步的探讨。  相似文献   
885.
ABSTRACT: Porous ceramic cups under constant tension (0.45 bar) were used to extract solutions from undisturbed soil columns. Solution concentration changed with length of extraction time. Significant relationships were found between extraction time and concentrations of P, Ca, and K in soil solution for two sample depths in an Omega loamy sand soil column. At two extraction time classes and at two sample depths, combined data from 12 soil columns representing two soil series reinforce the relationship. As time to extract a sample increases, the sample probably represents solution held by soil at tensions approaching those applied to the ceramic cup. We recommend that the choice of an extraction tension be given consideration in studies using porous ceramic cups under constant tension for monitoring constituents of soil solution. In addition, care must be taken to attain good physical contact between the cups and the soil material.  相似文献   
886.
正本清源,系统开发整治长江各支流网系的山丘土地   总被引:1,自引:0,他引:1  
长江流域泥沙问题仍值得重视。长江不同于黄河.黄河年输沙量16亿t,主要为悬移质;长江多年测得输沙量5.4亿t,这仅是长江的部分泥沙量-悬移质,还有数据不详的推移质随急流滚动位移。防治泥沙的良策是上游绿化造林,但还有很大面积的陡玻耕地,以及紫色土丘陵坡耕地与石灰岩区坡耕地等,仍应重点防护;至于广大的荒山、荒坡,更应多途径合理经营,从各大、小流域;溯江而上到源头径流发生处,采取工程与生物相结合的方法,节节设防,将泥沙来源减少到最低限度。最好利用大坝兴建的空隙期间,有计划有步骤地节节设防,以延长大坝寿命,当地居民亦可获利。  相似文献   
887.
Simulations of gas explosion of hydrogen/air mixture inside two rooms connected by ducts are carried out. Scalar transport chemical reaction model and LES turbulence model are utilized to reduce the calculation load and to conduct real-scale analysis. The effects of ignition source locations and volume of ignited room are analyzed, and the time history of pressure and rate of pressure rise in each room are focused in this study. When the volume of the ignited room is larger than the other room, the high pressure from the other room causes a force to act on the partition to the ignited room. This study indicates that the current technique can predict specific features of gas explosions inside two rooms connected by the ducts.  相似文献   
888.
Liming and/or application of specific nutrients have been proposed as countermeasures to the acidification of forest soils in southern Sweden. In this study the stem growth of Picea abies (L.) Karst. growing on acidic mineral soils in SW Sweden was investigated 10 years after additions of lime (Ca; 3000 kg lime ha−1), lime plus P (25 kg ha−1) and K (80 kg ha−1), or N in low doses (2 × 10 kg ha−1 yr−1) (treatments: CaPK, Ca, N, CaPKN, and 2Ca2P2K, respectively). Compared with the control, stem growth was increased following all treatments involving lime additions, including liming alone. The PK addition did not seem to affect growth. The most plausible cause of the observed growth increases was that the lime additions indirectly increased the supply of plant-available N. The annual low-dose N addition did not significantly affect growth. This suggests that air-borne deposition of N, which supplies very small doses of N throughout the year, has a minor or even negligible influence on P. abies growth.  相似文献   
889.
The effects of harvesting on the long-term mass balances of calcium (Ca), magnesium (Mg) and potassium (K) were evaluated on a regional level in Sweden. A new high-resolution weathering database was used together with estimates of total deposition, losses through harvest and leaching. Estimates were made for pine and spruce separately and for two harvesting intensity scenarios: stem harvesting and whole-tree harvesting. The mass balance calculations showed net losses of Ca and Mg in almost the whole country for both scenarios. The losses were smaller for pine than for spruce. The K balances were mainly positive for pine but negative for spruce. Leaching was a main factor in the mass balances, especially for Ca and Mg. Whole-tree harvesting in spruce forests led to substantially higher net losses of K and Ca than stem harvesting, according to the calculations. In the whole-tree harvesting scenario in spruce forests the estimated yearly net losses of Ca, Mg and K corresponded to at least 5%, 8% and 3% of the pools of exchangeable base cations, respectively, at 25% of the analysed sites. If losses of this magnitude continue the depletion of the pools of Ca, Mg and K may lead to very low base saturation of the soils, possibly accompanied by negative effects on soil fertility, runoff water quality, tree vitality and tree growth within a forest rotation in parts of Sweden. Avoiding whole-tree harvesting can improve the situation substantially for K, but the losses of Ca and Mg will still be significant.  相似文献   
890.
研究用食物废弃物制得的吸附剂(FRA)对水中多种重金属的吸附,并研究酒石酸钾钠对FRA吸附重金属的影响,探讨影响的机理。结果表明,两种重金属离子共存体系中重金属离子的竞争吸附系数相当,均在0.46~0.54之间。增加共存重金属种类减弱FRA对重金属的吸附效果。初始浓度较低时,竞争吸附对FRA吸附量的影响较小。较低p H值时酒石酸钾钠的浓度对重金属Cu~(2+),Zn~(2+)及Cd~(2+)的吸附去除效果影响更大。FRA对Cu~(2+),Zn~(2+),Pb~(2+)和Cd~(2+)的吸附符合Langmuir等温式。  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