全文获取类型
收费全文 | 444篇 |
免费 | 56篇 |
国内免费 | 255篇 |
专业分类
安全科学 | 44篇 |
废物处理 | 29篇 |
环保管理 | 45篇 |
综合类 | 414篇 |
基础理论 | 69篇 |
污染及防治 | 139篇 |
评价与监测 | 8篇 |
社会与环境 | 5篇 |
灾害及防治 | 2篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 16篇 |
2021年 | 23篇 |
2020年 | 17篇 |
2019年 | 20篇 |
2018年 | 17篇 |
2017年 | 25篇 |
2016年 | 29篇 |
2015年 | 45篇 |
2014年 | 44篇 |
2013年 | 55篇 |
2012年 | 67篇 |
2011年 | 49篇 |
2010年 | 45篇 |
2009年 | 53篇 |
2008年 | 35篇 |
2007年 | 50篇 |
2006年 | 41篇 |
2005年 | 29篇 |
2004年 | 14篇 |
2003年 | 15篇 |
2002年 | 12篇 |
2001年 | 9篇 |
2000年 | 11篇 |
1999年 | 6篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1986年 | 1篇 |
排序方式: 共有755条查询结果,搜索用时 31 毫秒
671.
飞机驾驶舱人机几何适配性评价指标研究 总被引:2,自引:0,他引:2
飞机驾驶舱人机几何适配性评价对于保障人机效能的充分发挥和飞行安全至关重要。针对一些评价指标制定了相关标准和规范,但未形成一套可操作的指标体系。针对该问题,提出采用改进德尔菲法建立飞机驾驶舱人机几何适配性评价指标体系。通过对现有相关标准、规范和技术数据进行分析研究,初步确定出38个评价指标。针对确定的指标,聘请了飞过多种型号飞机的23名现役有经验飞行员作为专家咨询人员进行了两轮咨询,在对咨询结果进行统计处理的基础上,筛选出了21个评价指标,该指标体系的建立为飞机驾驶舱人机几何适配性综合评价奠定了基础,也可为航空工程部门的评价工作提供科学依据,并有一定的指导作用和实用价值。 相似文献
672.
One common method of criticizing genetically modified organisms (GMOs) is to label them as “magic bullets.” However, this criticism, like many in the debate over GMOs, is not very clear. What exactly is the “magic bullet criticism”? What are its origins? What flaw is it pointing out in GM crops and agricultural biotechnology? What is the scope of the criticism? Does it apply to all GMOs, or just some? Does it point to a fatal flaw, or something that can be fixed? The goal of this paper is to answer these questions and clarify the magic bullet criticism of agricultural biotechnology. It is hoped that the results of this exercise will be helpful in advancing deliberation over the role GMOs and agricultural biotechnology should play in 21st century agriculture. 相似文献
673.
674.
Hazard mitigation or mitigation hazard? 总被引:1,自引:1,他引:0
Reuter H Menzel G Pehlke H Breckling B 《Environmental science and pollution research international》2008,15(7):529-535
BACKGROUND, AIM AND SCOPE: Transgenic oilseed rape (Brassica napus L.; OSR) is estimated to be environmentally and economically problematic because volunteers and ferals occur frequently and because of its hybridisation potential with several wild and weedy species. A proposed mitigation strategy aims to reduce survival, in particular in conventional OSR crops, by coupling the transgenic target modification with a dwarfing gene to reduce competitive fitness. Our study allowed us to access potential ecological implications of this strategy. MATERIALS AND METHODS: On a large scale (>500 km(2)), we recorded phenological and population parameters of oilseed rape plants for several years in rural and urban areas of Northern Germany (Bremen and surroundings). The characterising parameter were analysed for differences between wild and cultivated plants. RESULTS: In rural areas, occurrences of feral and volunteer OSR together had an average density of 1.19 populations per square kilometre, in contrast to urban areas where we found 1.68 feral populations per square kilometre on average. Throughout the survey, the vegetation cover at the locations with feral OSR ranged from less than 10% to 100%. Our investigations gave clear empirical evidence that feral OSR was, on average, at least 41% smaller than cultivated OSR, independent of phenological state after onset of flowering. DISCUSSION: The findings can be interpreted as phenotypic adaptation of feral OSR plants. Therefore, it must be asked whether dwarfing could be interpreted as an improvement of pre-adaptation to feral environments. In most of the sites where feral plants occurred, germination and establishment were in locations with disturbed vegetation cover, allowing initial growth without competition. Unless feral establishment of genetically modified dwarfed traits are specifically studied, it would not be safe to assume that the mitigation strategy of dwarfing also reduces dispersal in feral environments. CONCLUSIONS AND RECOMMENDATIONS: With respect to OSR, we argue that the proposed mitigation approach could increase escape and persistence of transgene varieties rather than reducing them. We conclude that the development of effective hazard mitigation measures in the risk evaluation of genetically modified organisms requires thorough theoretical and empirical ecological analyses rather than assumptions about abstract fitness categories that apply only in parts of the environment where the plant can occur. 相似文献
675.
改性PES膜在MBR中膜阻力分析及膜污染机理研究 总被引:2,自引:0,他引:2
以聚醚砜(PES)、醋酸纤维素(CA)和纳米二氧化钛(TiO2)为膜材料,采用L-S相转化法制备共混改性PES膜。在24℃、0.2 MPa的操作条件下,制得的PES膜纯水通量为300 L/(m2.h)左右,CA改性PES膜为660 L/(m2.h)左右,TiO2改性PES膜为840 L/(m2.h)左右。通过膜生物反应器中膜阻力的测定,表明膜污染主要由浓差极化层及凝胶层引起的;通过活性污泥对膜污染机理的研究,判断出污泥的过滤过程基本符合沉积过滤定律。在MBR中运行时,改性PES膜稳定通量高于未改性膜,总阻力低于未改性膜;TiO2改性膜稳定通量高于CA改性膜,总阻力低于CA改性膜;通过扫描电镜分析,改性PES膜沉积层的厚度均比未改性膜薄,TiO2改性膜沉积层厚度小于CA改性膜,表明改性膜的抗污染性能提高了,TiO改性膜抗污染性能更优。 相似文献
676.
通过丁二酸酐与γ-氨丙基三甲氧基硅烷改性后的纳米SiO2(即可分散的纳米二氧化硅,简称DNS)反应,合成了羧基化的DNS,再经过与壳聚糖脱水生成酰胺的过程,合成了改性壳聚糖。通过红外光谱和扫描电镜对改性壳聚糖进行表征。研究了壳聚糖及改性壳聚糖微粒吸附Ni2+时溶液pH值、时间、吸附剂用量和Ni2+初始浓度等对吸附率的影响,并确定了最佳条件为:pH=7,吸附时间为120 min,吸附剂的投加量为0.3 g。改性壳聚糖比壳聚糖具有更强的吸附Ni2+的能力,吸附率达67.01%。 相似文献
677.
以甘肃临泽产凹凸棒黏土(以下简称凹土)为原料制备吸附剂,对120#溶剂油进行脱硫实验,同时采用脱硫率、X射线衍射(XRD)和红外光谱(IR)对吸附剂进行了表征.结果表明:(1)以临泽凹土为原料制备吸附剂的最佳条件为焙烧时间3.0h、焙烧温度350℃、未精制吸附剂质量和溶剂油体积的比值1∶5 g/mL、脱硫时间75 min.按此最佳条件制备吸附剂,可将120#溶剂油含硫量由424 μg/g降至213 μg/g.脱硫率可以达到49.8%.(2)经过XRD及IR分析,120 #溶剂油中的硫被脱除后在吸附剂中以硫醚和CaS的形式存在.用浸渍法制备的吸附剂达到了一定的脱硫效果. 相似文献
678.
In the present study, response surface methodology (RSM) based on the Box-Behnken design (BBD) was employed to investigate the effects of the different operating conditions on the removal of the fungicide (Vapam) onto soil modified with perlite using sorption process. The process parameters such as pH of the fungicide solution (2, 5 and 8), temperature (15, 25 and 35°C), shaking time (2, 13 and 24 h) and the percentage of perlite in the modified soil (0, 2 and 4 %) were investigated using a four-factor-three-level Box-Behnken design at an initial fungicide concentration of C0 = 1.6 mg/L as a fixed input parameter. A second-order quadratic model suggested the optimum conditions to be as follows: fungicide solution pH of 3.57, temperature of 15°C, shaking time of 3.5 h and 4% of perlite in the modified soil which resulted in the improvement of Vapam sorption. Under optimum conditions, the fungicide (Vapam) removal was predicted 12.88 μg/g by BBD. The confirmatory experiments were conducted and the results revealed that the fungicide removal was 13.14 μg/g which indicated that the predicted and the observed values of response (Vapam removal) were in close agreement. Therefore, the soil modified with perlite holds good potential for Vapam sorption. This is the first report on fungicide Vapam sorption onto soil modified with perlite using statistical experimental design employing response surface methodology. 相似文献
679.
680.
利用改性凹土与聚氨酯原料混合发泡,制备复合载体,对微污染河水的NH4+-N和TOC的去除效果进行实验研究,结果表明对NH4+-N、TOC的去除存在着明显的时段性,随着时间的延长,出水NH4+-N、TOC的去除效率逐渐降低,最终趋于稳定。改性后凹土制备的复合载体对NH4+-N、TOC处理能力得到提高,NH4+-N去除率从37.50%提升到75.10%;TOC去除率从15.34%提高到36.15%。 相似文献