全文获取类型
收费全文 | 563篇 |
免费 | 114篇 |
国内免费 | 146篇 |
专业分类
安全科学 | 54篇 |
废物处理 | 14篇 |
环保管理 | 133篇 |
综合类 | 393篇 |
基础理论 | 59篇 |
环境理论 | 5篇 |
污染及防治 | 38篇 |
评价与监测 | 39篇 |
社会与环境 | 36篇 |
灾害及防治 | 52篇 |
出版年
2024年 | 6篇 |
2023年 | 21篇 |
2022年 | 24篇 |
2021年 | 30篇 |
2020年 | 37篇 |
2019年 | 40篇 |
2018年 | 33篇 |
2017年 | 49篇 |
2016年 | 52篇 |
2015年 | 26篇 |
2014年 | 38篇 |
2013年 | 51篇 |
2012年 | 39篇 |
2011年 | 44篇 |
2010年 | 33篇 |
2009年 | 40篇 |
2008年 | 24篇 |
2007年 | 32篇 |
2006年 | 29篇 |
2005年 | 20篇 |
2004年 | 17篇 |
2003年 | 23篇 |
2002年 | 14篇 |
2001年 | 12篇 |
2000年 | 14篇 |
1999年 | 11篇 |
1998年 | 16篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 9篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1985年 | 2篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有823条查询结果,搜索用时 15 毫秒
101.
采用电化学和化学的方法制备了硫酸掺杂的p型导电聚苯胺和萘钠掺杂的n型导电聚苯胺,采用扫描电镜、X衍射分析、红外、紫外-可见分光光度计和和四探针法等手段对各种聚苯胺的形貌、结构和导电性等能进行了分析;将p型和n型导电聚苯胺组装成太阳能电池,研究了材料的结构、性能、电池的组装方式对太阳能电池性能的影响.结果表明:制备的p型和n型导电聚苯胺呈球形,堆砌结实,平均粒径在30—50nm,结晶度较大,导电性优异,在可见光区有强烈的吸收;由两者组成的双层太阳能电池性能优异,其开路电压为1.65V,短路电流为1.66mA.cm-2,填充因子为0.35,光电转换效率为2.96%. 相似文献
102.
Emiel A. Den Hartog George Havenith 《International journal of occupational safety and ergonomics》2013,19(2):245-261
For wearers of protective clothing in radiation environments there are no quantitative guidelines available for the effect of a radiative heat load on heat exchange. Under the European Union funded project ThermProtect an analytical effort was defined to address the issue of radiative heat load while wearing protective clothing. As within the ThermProtect project much information has become available from thermal manikin experiments in thermal radiation environments, these sets of experimental data are used to verify the analytical approach. The analytical approach provided a good prediction of the heat loss in the manikin experiments, 95% of the variance was explained by the model. The model has not yet been validated at high radiative heat loads and neglects some physical properties of the radiation emissivity. Still, the analytical approach provides a pragmatic approach and may be useful for practical implementation in protective clothing standards for moderate thermal radiation environments. 相似文献
103.
我国油田多采用絮凝剂处理含油污水。为得到高效、廉价的絮凝剂,使用赤泥最优化制备聚合氯化铝铁。通过化学分析法和X射线衍射分析,得出赤泥中铝﹑铁元素含量。正交实验结果表明:影响Fe溶出的因素由强到弱依次为盐酸用量系数﹑反应温度﹑目数和反应时间,最佳浸出条件为目数80~120、液固比5.5、反应温度95℃、反应时间3.5h。 相似文献
104.
The objective of this study was to investigate the efficacy of panel solar cookers in reducing urease activity in full-fat soybeans (Glycine max). Changes in urease activity of soaked (SM), coarse-milled (CM) and whole dry (WM) full fat soybeans were investigated by roasting for 0, 30, 60, 90, 120, 150 and 180 min in multiple reflector panel solar cookers, in a 3 3 3 factorial experiment. Soaking soybeans for 14 h reduced (p<0.05) 1 urease activity by 9%, from 6.58 meqNH3/g DM to 5.98 meqNH3/g DM. After 180 min of solar roasting, urease activity levels had declined by 81%, 67% and 23% in soaked, milled and whole dry soybeans respectively. Full fat soybean urease activity can be reduced faster in soaked than in dry soybeans. Findings suggest that there is potential in using multiple reflector panel solar cookers to reduce urease activity in full fat soybeans. 相似文献
105.
藻类的光谱吸收特征及其混合藻吸收系数的分离 总被引:5,自引:3,他引:2
利用定量滤膜技术测定了实验室培养的聚球藻(Synechococcus 7942)、铜绿微囊藻(Microcystis aeruginosa)、斜生栅藻(Scenedesmusobliquus)、蛋白核小球藻(Chlorella pyrenoidosa)、直链硅藻的吸收光谱(Melosira granulate Var.angustissima),通过其标准化吸收谱,分析了同种藻不同生长时期的吸收谱特征,并比较分析了不同藻类的标准化吸收谱.结果表明,同一藻的标准化吸收光谱在不同生长时期基本恒定不变.色素组成及其比例的不同是引起藻类间吸收光谱变化的主要原因,同时也是大型浅水湖泊中浮游植物种群演替的原因之一.蓝藻光谱主要存在620nm左右的吸收峰,使得其在水体中较易获取生长所需的光能.直链硅藻在短波范围内稍强的吸收能力被非藻类颗粒物、黄质所弱化,而其在630nm的吸收峰较低,因而难以成为浅水湖泊中的优势种;绿藻在655nm处的吸收肩峰有利于其光能竞争.通过纯种藻的标准化吸收谱,较为成功地对混合藻的吸收谱进行了分离. 相似文献
106.
《International Journal of Sustainable Engineering》2013,6(4-5):280-293
The thermal performances of an evacuated tube collector (ETC) and flat-plate solar air collector (FPC) are experimentally investigated at different air flow rates. To investigate the performance of the ETC and FPC, experimental set-ups were fabricated. Air was used as a working fluid and tested at the same climatic conditions. The ETC had 15 evacuated tubes with a surface area of 1.66 m2. The experimental set-up consisted of a header with a hollow pipe (square pipe) in the centre through which the air flowed. The flat-plate collector had a surface area of 1.35 m2. The FPC had a black painted absorber sheet which divides the collector into two sections. The air flowed through the upper and the lower sections parallel to the collector to minimize the overall heat loss. The temperature of the outlet air depends on several factors along with the airflow rate and the intensity of the solar radiation. It was found that during the day at high flow rates, the efficiency of the ETC varies from 0.12 to 0.5, and for the flat plate it was from 0.29 to 0.68. The maximum temperature of the air was 56.7°C for the ETC and 25.7°C for the FPC. 相似文献
107.
《International Journal of Sustainable Engineering》2013,6(5):291-302
ABSTRACTDemand of electrical energy is exponentially increasing causing environmental problems due to extensive use of fossil fuels. Hence, research has been promoted in renewable energy technologies to mitigate environmental pollution. Indian subcontinent is rich in renewable energy sources (RES). This paper describes potential of RES and region-wise installed capacity in India. Estimated potential of RES is 57 GW which is targeted to be 175 GW by 2022. A logical framework for our future research work has been presented. This includes performance optimisation of solar pumping system and reliability assessments of the designed system using reliability indices.Abbreviation: RES: Renewable energy resources; SHP: small hydro plants; GOI: Government of India; MNRE: Ministry of New and Renewable Energy; LHP: large hydropower; BCM: billion cubic metres; PEC: per-capita energy consumption; JNNSM: Jawaharlal Nehru National Solar Mission; DNI: direct normal irradiance; SPV: solar photovoltaic; UMPP: ultra mega green solar power project; GIS: geographic information systems; WMS: wind monitoring stations; MPWL: Madhya Pradesh windfarms Ltd.; MIB: mat river basin; SWAT: Soil and Water Assessment Tool; ROR: run of river; SMS: short message service; CDM: clean development mechanism; NIOT: national institute of ocean technology; LOLP: loss of load probability; CSO: Central Statistics Office; CEA: Central Electricity Authority; TERI: The Energy and Resources Institute; WPI: Wind Power India; IEA: International Energy Agency; EAI: Energy Alternatives India; BKP: Biomass Knowledge Portal; IRENA: International Renewable Energy Agency; GAIN: Global Agricultural Information Network; NITI: National Institution for Transforming India; NIWE: National Institute of Wind Energy; UP: Uttar Pradesh; J&K: Jammu and Kashmir; HP: Himachal Pradesh; NR: northern region; MP: Madhya Pradesh; WR: western region; TN: Tamil Nadu; AP: Andhra Pradesh; SR: southern region; ER: eastern region; NER: north eastern region; A&N: Andaman & Nicobar 相似文献
108.
采用紫外-可见吸收光谱(UV-vis)和三维荧光光谱结合平行因子法(EEMs-PARAFAC)研究两条面源输入强度不同的城市河流春夏两季水体中溶解性有机质(DOM)含量和组成变化.结果表明,两条河流夏季水体DOM腐殖化程度和相对分子质量均显著高于春季(P<0.01). PARAFAC模型共解析出C1(UVC类富里酸)、 C2(类色氨酸)、 C3(类胡敏酸)和C4(UVA类富里酸)这4个化学组分,C1[(31±6)%]和C2[(31±4)%]为水体DOM中主要荧光组分.高面源输入水平的河流春季各组分荧光强度均低于夏季,而低面源输入水平的河流与之相反.随机森林回归模型表明,C3%对河流水质变化敏感度最高(R2=0.75,P<0.001),具有很好的指示作用;水面覆盖率(Cover)对C4%有显著预测重要性(P<0.001), C4%易受光化学氧化作用影响.主成分分析(PCA)和Adonis检验表明,氮和磷为水体自生源过程的重要推动力,面源输入强度和季节变化对城市河流水体状况有显著影响(R2=0.775,P<0.001).城... 相似文献
109.
结合工程实际,介绍了太阳能产业用多晶硅片切割过程中产生的割液废液的处理工艺及回收工艺,并分析了它的投资成本和经济效益。 相似文献
110.
基于Hilbert谱信息熵的煤矸放落振动特征分析 总被引:3,自引:2,他引:1
针对煤矿安全生产中的综放工作面煤矸界面探测问题,提出利用煤矸下落冲击钢板的振动特征来探测煤矸界面的方法。煤矸振动信号表现出非平稳特征,采用经验模态分解方法将复杂矿井环境下的煤矸振动信号分解成固有模态分量。选择包含煤矸振动特征的前7个本征模函数(IMF)分量,通过Hilbert变换得到Hilbert谱。分析不同放煤状态下钢板振动信号的Hilbert谱发现,顶煤下落时的Hilbert谱分布较均匀,而煤矸混放时的Hilbert谱呈现不均匀分布。根据信息熵理论,提出了基于Hilbert谱信息熵的煤矸振动特征提取方法。试验结果表明,顶煤下落时的Hilbert谱信息熵要大于煤矸混放时的Hilbert谱信息熵,因此,煤矸振动的Hilbert谱信息熵特征能够准确地反映放煤状态。 相似文献