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981.
982.
983.
对氧化铝厂蒸发器发生应力腐蚀的危害性作了介绍 ,描述了应力腐蚀裂纹的特征 ;对应力腐蚀产生的原因进行了分析 ,并提出了防治措施 相似文献
984.
粉煤灰黑液胶凝材料的研究 总被引:4,自引:0,他引:4
研究了改性黑液作粉煤灰的激发剂,并与石灰、磷石膏一起制成一种新型的胶凝材料,讨论了粉煤灰、石灰、磷石膏及黑液的用量对胶凝材料性能的影响,并通过正交试验与模糊数学分析求出了最佳工艺参数。试验结果表明,该种新材料的抗压强度能达≥20MPa,耐水性良好,且工艺简单、成本低。 相似文献
985.
我国地质环境与社会经济的物质流分析 总被引:2,自引:1,他引:1
论文利用物质流分析方法对2000~2005年我国地质环境与社会经济的物质流进行了核算与分析。结果表明:近年我国社会经济发展从地质环境获取的物质需求总量呈增加态势,2005年达到了439.6×108t,显著超过了国外主要发达国家,致使我国地质环境压力不断增大;我国经济增长在依赖于地质资源的同时,物质生产力从240.9元/t增长到416.5元/t,但与主要发达国家相比,我国经济发展仍属于资源消耗型,可持续发展能力较低;我国人均物质消耗量为33.6t,明显低于主要发达国家,按照发达国家人均物质消耗量开发地质资源将远远超过我国的地质环境承载力,决定了我国只能走资源节约型的经济发展道路。 相似文献
986.
Anna Dornhaus Jo-Anne Holley Victoria G. Pook Gemma Worswick Nigel R. Franks 《Behavioral ecology and sociobiology》2008,63(1):43-51
Here, we study distribution of workload and its relationship to colony size among worker ants of Temnothorax albipennis, in the context of colony emigrations. We find that one major aspect of workload, number of items transported by each worker,
was more evenly distributed in larger colonies. By contrast, in small colonies, a small number of individuals perform most
of the work in this task (in one colony, a single ant transported 57% of all items moved in the emigration). Transporters
in small colonies carried more items to the new nest per individual and achieved a higher overall efficiency in transport
(more items moved per transporter and unit time). Our results suggest that small colonies may be extremely dependent on a
few key individuals. In studying colony organisation and division of labour, the amount of work performed by each individual,
not just task repertoire (which tasks are performed at all), should be taken into account. 相似文献
987.
Insect larvae increase in size with several orders of magnitude throughout development making them more conspicuous to visually
hunting predators. This change in predation pressure is likely to impose selection on larval anti-predator behaviour and since
the risk of detection is likely to decrease in darkness, the night may offer safer foraging opportunities to large individuals.
However, forsaking day foraging reduces development rate and could be extra costly if prey are subjected to seasonal time
stress. Here we test if size-dependent risk and time constraints on feeding affect the foraging–predation risk trade-off expressed
by the use of the diurnal–nocturnal period. We exposed larvae of one seasonal and one non-seasonal butterfly to different
levels of seasonal time stress and time for diurnal–nocturnal feeding by rearing them in two photoperiods. In both species,
diurnal foraging ceased at large sizes while nocturnal foraging remained constant or increased, thus larvae showed ontogenetic
shifts in behaviour. Short night lengths forced small individuals to take higher risks and forage more during daytime, postponing
the shift to strict night foraging to later on in development. In the non-seasonal species, seasonal time stress had a small
effect on development and the diurnal–nocturnal foraging mode. In contrast, in the seasonal species, time for pupation and
the timing of the foraging shift were strongly affected. We argue that a large part of the observed variation in larval diurnal–nocturnal
activity and resulting growth rates is explained by changes in the cost/benefit ratio of foraging mediated by size-dependent
predation and time stress. 相似文献
988.
Six firing range soils were analyzed, representing different environments, firing conditions, and maintenance practices. The
particle size distribution and lead (Pb) concentration in each soil fraction were determined for samples obtained from the
backstop berms. The main factors that were found to influence Pb fragment size were the type of soil used to construct the
berms and the type of weapon fired. The firing of high velocity weapons, i.e., rifles, onto highly angular soils induced significant
fragmentation of the bullets and/or pulverization of the soil itself. This resulted in the accumulation of Pb in the finer
soil fractions and the spread of Pb contamination beyond the vicinity of the backstop berm. Conversely, the use of clay as
backstop and the use of low velocity pistols proved to be favorable for soil clean-up and range maintenance, since Pb was
mainly present as large metallic fragments that can be recovered by a simple screening process. Other factors that played
important roles in Pb particle size distribution were soil chemistry, firing distance, and maintenance practices, such as
the use of water spray for dust suppression and deflectors prior to impact. Overall, coarse Pb particles provide much easier
and more cost-effective maintenance, soil clean-up, and remediation via physical separation. Fine Pb particles release Pb
more easily, pose an airborne Pb hazard, and require the application of stabilization/solidification treatment methods. Thus,
to ensure sustainable firing range operations by means of cost-effective design, maintenance, and clean-up, especially when
high velocity weapons are used, the above mentioned factors should be carefully considered. 相似文献
989.
990.
比较系统地研究了疏浚污泥的各种参数 ,如渗透系数、浸出毒性、重金属含量等 ,以及作为垃圾覆盖土的可行性。研究结果表明 ,用该污泥作垃圾填埋场覆盖土的边坡稳定性能较好 ,基本上满足作为覆盖土的技术要求 ,使用后不会给垃圾渗滤液的处理增加负担。因此 ,以疏浚污泥作为生活垃圾填埋场覆盖土 ,可同时解决平原型填埋场缺土和疏浚污泥的最终出路问题。 相似文献