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521.
用~(32)P后标记方法,对一组22例接触苯乙烯的工人和8例未接触苯乙烯(空白)的工人进行测试,其静脉血中的淋巴细胞有4例(高浓度,大于40ppm)发现DNA-环氧苯乙烯加合物;而另外接触高浓度苯乙烯、低浓度苯乙烯和空白试样中,均未发现。在已测出的4例中,加合物形成水平为0.07—3.38加合物/10~7正常核酸,DNA的总损伤水平为5—9加合物/10~7正常核酸。 用小牛胸腺DNA、四种脱氧核苷3′-单磷酸分别与环氧苯乙烯进行体外反应,然后用~(32)P后标记法测定产物中的DNA加合物,初步确证有六种加合物及其衍生物存在,修饰位置是鸟苷碱基。并确证了其中三种加合物的化学结构,另外几种加合物的结构有待进一步鉴定。 ~(32)P后标记法测DNA加合物,灵敏度高达1加合物/10~(10)正常核酸,近于人体二倍体细胞基因水平(1.2×10~(10)碱基)。 相似文献
522.
污泥膨胀形成机理及控制措施研究现状和进展 总被引:4,自引:0,他引:4
污泥膨胀现象在全球污水处理厂普遍存在,已成为制约活性污泥工艺发展的重大难题之一.本文总结了丝状细菌研究现状;重点阐述了当前引起污泥膨胀的主要机理;说明了基于这些机理的选择器控制理论;给出了主要的选择器类型.对当前关于污泥膨胀的研究进展和方向,分别从微生物和数学模型2个方面进行了讨论,最后,提出了一系列亟待解决的问题. 相似文献
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526.
程序升温条件下铁及其氧化物在CO存在时对N_2O的还原机理 总被引:1,自引:0,他引:1
应用热综合分析仪 (TG FTIR)研究了在还原性气氛下Fe及其氧化物对N2 O的催化还原作用 .研究发现铁氧化物对氮氧化物的催化还原能力相当弱 ,而Fe可以高效地降低N2 O分解的初始温度和提高N2 O向N2 的转化率 .在Fe和CO的作用下 ,N2 O的初始分解温度为 92 0K和 10 0 0K .在 112 3K时 ,N2 O的转化率达到 95 %和 80 % .TG/DSC曲线表明了在Fe与N2 O反应过程中CO的作用表现为通过与N2 O在反应表面的竞争吸附使铁氧化物还原为金属铁 ,X射线衍射证明Fe与N2 O反应后的氧化物为Fe2 O3 ;扫描电镜对反应后Fe表面物理形态的研究发现 ,在CO作用下 ,Fe的表面呈松散结构 ,可以保证Fe对氮氧化物反应的连续进行 相似文献
527.
Pathak H Bhatia A Prasad S Singh S Kumar S Jain MC Kumar U 《Environmental monitoring and assessment》2002,77(2):163-178
Nitrous oxide (N2O) accounts for 5%of the total enhanced greenhouse effect and responsiblefor the destruction of the stratospheric ozone. The rice-wheat cropping system occupying 26 million ha ofproductive land in Asia could be a major source ofN2O as most of the fertilizer N in this region isconsumed by this system. Emission of N2O asinfluenced by application of urea, urea plus farm yardmanure (FYM), and urea plus dicyandiamide (DCD), anitrification inhibitor, was studied in rice-wheatsystems of Indo-Gangetic plains of India. Total emissionof N2O-N from the rice-wheat systems varied between654 g ha-1 in unfertilized plots and 1570 g ha-1 in urea fertilized plots. Application of FYM and DCDreduced emission of N2O-N in rice. The magnitude ofreduction was higher with DCD. In wheat also N2O-Nemission was reduced by DCD. FYM applied in rice had noresidual effect on N2O-N emission in wheat. In riceintermittent wetting and drying condition of soilresulted in higher N2O-N emission than that ofsaturated soil condition. Treatments with 5 irrigationsgave higher emissions in wheat than those with 3irrigations. In rice-wheat system, typical of a farmer'sfield in Indo-Gangetic plains, where 240 kg N isgenerally applied through urea, N2O-N emission is1570 g ha-1 (0.38% of applied N) and application ofFYM and DCD reduced it to 1415 and 1096 g ha-1,respectively. 相似文献
528.
Many trace constituents other than carbon dioxide affect the radiative budget of the atmosphere. The existing international agreement to limit greenhouse gases, the Kyoto Protocol, includes carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6) and credit for some carbon sinks. We investigate technological options for reducing emissions of these gases and the economic implications of including other greenhouse gases and sinks in the climate change control policy. We conduct an integreated assessment of costs using the MIT Emissions Prediction and Policy Analysis (EPPA) model combined with estimates of abatement costs for non-CO2 greenhouse gases and sinks. We find that failure to take advantage of the other gas and sink flexibility would nearly double aggregate Annex B costs. Including all the GHGs and sinks is actually cheaper than if only CO2 had been included in the Protocol and their inclusion achieves greater overall abatement. There remains considerable uncertainty in these estimates, the magnitude of the savings depends heavily on reference projections of emissions, for example, but these uncertainties do not change the overall conclusion that non-CO2 GHGs are an important part of a climate control policy. 相似文献
529.
以某污水处理厂好氧曝气池为研究对象,利用N_2O和NO在线检测仪,监测好氧池不同空间位置处N_2O和NO的释放量,考察了氮素浓度、溶解氧及p H值对N_2O和NO释放量的影响.该污水处理厂好氧池DO浓度在0.24~1.12mg/L之间,且大多处于0.6mg/L左右,较低的DO导致NO2--N浓度沿水流推流方向不断积累;相应的,N_2O和NO释放量沿水流推流方向不断升高,并于好氧池末段达到最高值.NO释放NO2--N量与浓度显著正相关,N_2O释放量与NO2--N浓度也有一定的相关性,但没有NO显著.基于空间检测数据估算获得该污水处理厂N_2O释放量占进水NH_4+-N比例为6.34%~8.83%,NO释放量占进水NH4+-N比例为0.033%~0.034%. 相似文献
530.
Impact of dicyandiamide on emissions of nitrous oxide, nitric oxide and ammonia from agricultural field in the North China Plain 总被引:1,自引:0,他引:1
Nitrous oxide(N_2O), nitric oxide(NO) and ammonia(NH_3) emissions from an agricultural field in the North China Plain were compared for three treatments during a whole maize growing period from 26 June to 11 October, 2012. Compared with the control treatment(without fertilization, designated as CK), remarkable pulse emissions of N_2O, NO and NH_3 were observed from the normal fertilization treatment(designated as NP) just after fertilization, whereas only N_2O and NH_3 pulse emissions were evident from the nitrification inhibitor treatment(designated as ND). The reduction proportions of N_2O and NO emissions from the ND treatment compared to those from the NP treatment during the whole maize growing period were 31% and 100%, respectively. A measurable increase of NH_3 emission from the ND treatment was found with a cumulative NH_3 emission of 3.8 ± 1.2 kg N/ha,which was 1.4 times greater than that from the NP treatment(2.7 ± 0.7 kg N/ha). 相似文献