全文获取类型
收费全文 | 781篇 |
免费 | 92篇 |
国内免费 | 210篇 |
专业分类
安全科学 | 178篇 |
废物处理 | 20篇 |
环保管理 | 87篇 |
综合类 | 471篇 |
基础理论 | 123篇 |
环境理论 | 4篇 |
污染及防治 | 135篇 |
评价与监测 | 19篇 |
社会与环境 | 20篇 |
灾害及防治 | 26篇 |
出版年
2024年 | 1篇 |
2023年 | 10篇 |
2022年 | 25篇 |
2021年 | 18篇 |
2020年 | 27篇 |
2019年 | 24篇 |
2018年 | 30篇 |
2017年 | 41篇 |
2016年 | 39篇 |
2015年 | 54篇 |
2014年 | 46篇 |
2013年 | 48篇 |
2012年 | 93篇 |
2011年 | 60篇 |
2010年 | 46篇 |
2009年 | 64篇 |
2008年 | 47篇 |
2007年 | 66篇 |
2006年 | 67篇 |
2005年 | 48篇 |
2004年 | 33篇 |
2003年 | 35篇 |
2002年 | 29篇 |
2001年 | 33篇 |
2000年 | 20篇 |
1999年 | 17篇 |
1998年 | 16篇 |
1997年 | 14篇 |
1996年 | 12篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1989年 | 1篇 |
排序方式: 共有1083条查询结果,搜索用时 15 毫秒
721.
722.
为了加快平板膜-生物反应器的工程化应用步伐,以上海白龙港水质净化厂400 t/d的示范工程为依托,对平板膜-生物反应器的污染物去除效果、膜污染情况和清洗效果等进行了研究。平板膜-生物反应器的出水COD在20 mg/L左右,浊度小于5 NTU,氨氮小于5 mg/L,基本满足杂用水水质标准(GB/T18920-2002),可以回用作厂区内冲厕和绿化用水等。正交实验结果表明,对在线清洗效果影响较大的因素是曝气量和清洗点的跨膜压力,影响较小的是清洗时间;跨膜压力为45 kPa,停抽时间为2 h,曝气量为100 m3/h为在线清洗的最佳操作条件。 相似文献
723.
选取7种具有10 a以上种植史的菜地土壤,通过室外盆栽试验研究施尿素条件下影响冬季菜地N2O排放的主要土壤因素.结果表明,不同土壤间N2O排放具有显著差异.对照菜地的季节性N2O-N排放总量为2.74~4.37 mg·盆-1,排放量与土壤本底的铵态氮、硝态氮含量及pH值呈弱线性相关.施尿素不仅促进了N2O的排放,而且加大了土壤间N2O排放的差异,季节性排放总量为6.39~29.38 mg·盆-1.与2000-2001年麦田相比,虽然菜地施尿素量低于麦地,但是N2O排放量无明显减少,菜地和麦地土壤的N2O排放均与土壤有机碳含量、全氮含量、C/N比值呈显著负相关.此外,施尿素菜地的N2O排放与土壤粘粒含量呈显著负相关,与土壤砂粒含量呈显著正相关.进一步研究表明,化肥氮的N2O-N转化系数主要受土壤碳、氮含量的影响. 相似文献
724.
Nadia Scascighini Letizia Mattiacci Marco D’Alessandro Alan Hern Anja Sybille Rott Silvia Dorn 《Chemoecology》2005,15(2):97-104
Summary. It is well known that feeding by Pieris brassicae caterpillars on cabbage leaves triggers the release of volatiles that attract natural antagonists such as the parasitoid Cotesia glomerata. The temporal dynamics in the emissions of parasitoid attracting volatiles has never been elucidated in this system. In a time course experiment, caterpillar infested leaves attracted the parasitoid within one hour after infestation. At such an early stage of infestation, as much as fifty percent of the parasitoids flew towards the infested plant in a wind tunnel bioassay, while only five percent flew towards the non-infested control plant. Three hours after infestation and later, the response to the volatiles from the infested plant reached its maximum and then continued at a constantly high level for the remaining 14 hours of the experiment. Chemical analyses of volatiles collected from infested leaves at short time intervals during the first 24 hours identified a total of ten compounds, comprising green leaf volatiles, terpenoids, and a nitrile. Significant increase of emission within the first 5 hours following initial herbivory was detected for (Z)-3-hexen-1-ol, (Z)-3-hexen-1-yl acetate, cineole and benzylcyanide. Subsequently, a coupled bioassay-chemical analysis procedure was developed allowing for testing and analyzing the same sample for future identification of the bioactive compounds. This was achieved by using stir bar sorptive extraction for the analysis of solvent extracts of caterpillar-damaged leaves. 相似文献
725.
Summary. Many aquatic species use chemosensory information to assess predation risk. The cues used in such risk assessment can come
either from the predator (predator odour) or from injured prey (alarm cues). The information conveyed through chemicals may,
however, be inaccurate both spatially and temporally, as chemicals may persist in the environment long after the predator
is gone. Thus, the level of accuracy of the cues for risk assessment may depend on the persistency of the chemicals in the
habitat. Here, we investigated the persistency of alarm cues of a larval amphibian, the woodfrog (Rana sylvatica) in a ephemeral pond, their natural habitat. We introduced either alarm cues or control water in enclosed sleeves (~10 L)
installed in the pond. The sleeve water was then sampled after 5 min and every two hours for eight hours. We used the behavioural
response of woodfrog tadpoles to alarm cues as a bioassay to assess how long the alarm cues persisted in the environment.
We found that tadpoles responded with an antipredator response to the pond water containing alarm cues 5 min after the injection
of the cues in the sleeves but did not respond to that same pond water after two hours. Our results indicate that biodegradation
and/or photodegradation of alarm cues in natural habitats might occur relatively quickly as the loss of a response to the
cues in our experiment was independent of a dilution effect. This contrasts with previous laboratory results indicating that
chemicals may be active after several hours. 相似文献
726.
Recent empirical evidence suggests that important disparities exist between willingness to pay and compensation demanded for the same good. These results, which clearly contradict closely held economic doctrines, have led some influential commentators to call for an entirely new economic paradigm to displace conventional neoclassical theory. This study examines the generality of these experimental findings by going to a well-functioning marketplace and examining more than 350 individual decisions across two incentive-compatible elicitation mechanisms. The data suggest that behavior of individuals with intense experience approaches neoclassical predictions: any observed WTA/WTP disparity amongst this group is negligible. 相似文献
727.
728.
729.
介绍了地表水监测分析中对Cr6 测定方法的改进,通过活性炭吸附预处理后的水样消除水样中色度的干扰,并对活性炭的用量进行了分析,确定了活性炭的用量,以及对显色剂的改进.对基层监测站Cr6 测定有实际意义. 相似文献
730.