全文获取类型
收费全文 | 375篇 |
免费 | 36篇 |
国内免费 | 31篇 |
专业分类
安全科学 | 154篇 |
废物处理 | 2篇 |
环保管理 | 24篇 |
综合类 | 131篇 |
基础理论 | 53篇 |
污染及防治 | 16篇 |
评价与监测 | 18篇 |
社会与环境 | 28篇 |
灾害及防治 | 16篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 9篇 |
2021年 | 22篇 |
2020年 | 16篇 |
2019年 | 20篇 |
2018年 | 10篇 |
2017年 | 17篇 |
2016年 | 27篇 |
2015年 | 24篇 |
2014年 | 14篇 |
2013年 | 25篇 |
2012年 | 32篇 |
2011年 | 34篇 |
2010年 | 24篇 |
2009年 | 17篇 |
2008年 | 15篇 |
2007年 | 17篇 |
2006年 | 29篇 |
2005年 | 14篇 |
2004年 | 11篇 |
2003年 | 10篇 |
2002年 | 11篇 |
2001年 | 9篇 |
2000年 | 9篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有442条查询结果,搜索用时 31 毫秒
391.
392.
使用Web数据挖掘技术发挥网络教育中资源共享以及无时间局限性的优势,达到帮助学习者快速有效地寻找满足其个性需求的教学资源的目的,并且对其学习进程进行准确指导. 相似文献
393.
介绍等标污染负荷法和层次分析法的具体算法和特点,运用等标污染负荷法和层次分析法分别对七台河市新兴区的焦化工业大气污染源进行评价,比较排名顺序,从而得出层次分析法比等标污染负荷法更符合区域环境与经济的可持续发展要求. 相似文献
394.
改进的大气环境后量评价方法及应用 总被引:3,自引:0,他引:3
运用模糊集理论中的权距离和隶属度概念推导出一种改进的大气环境质量评价方法,评价过程能充分利用实际数据所包含的各种信息.实例应用结果表明,与广泛采用的模糊综合评判模型相比较,本文提出的评价方法得到的评价结果更为合理可靠. 相似文献
395.
396.
397.
Jason H. Peterson Bernard D. Roitberg J. H. Peterson 《Behavioral ecology and sociobiology》2006,59(5):589-596
Fisher's theoretical prediction of equal investment in each sex for a panmictic population (The genetical theory of natural selection. Clarendon, Oxford, 1930) can be altered by a number of factors. For example, the sex ratio theory predicts variation in
equal investment in each sex when the maternal fitness gains from increased investment differ between sexes. Changing sex
allocation because of changing payoffs may result from different ecological situations, such as foraging conditions. We investigated
the impact of foraging travel cost on relative investment in sons vs daughters. Field studies were carried out with the central-place-foraging
leafcutter bee Megachile rotundata (Fabricius), which has smaller males than females. Therefore, less investment is required to produce a viable son compared
with a daughter. We found that with increased flight distance to resources, females produced a greater proportion of sons.
Females also invested fewer resources in individual sons and daughters and produced fewer offspring with increased flight
distance. 相似文献
398.
To balance advantages and disadvantages of group living, some species have fission-fusion social systems in which members of the same group form frequently changing subgroups. This allows flexible responses of group size to external conditions while at the same time retaining group stability. In chimpanzees, subgroup (party) size and composition depend mainly on the presence of receptive females, food availability and the activity of the party. Here we analyse the extent to which fission-fusion parameters are influenced by changes of demographic variables like community size and composition. Data were collected from a habituated West African chimpanzee community (Taï forest, Côte dIvoire) over 10 years, during which total community size decreased from 51 to 21, and the number of adult males decreased from 9 to 2. Taï chimpanzees are highly gregarious, as they spend more than 80% of their time with unrelated conspecifics. With decreasing community size, party size, party duration and male-female association increased. Neither activity nor the presence of receptive females or feeding competition could explain the observed changes in grouping patterns. Thus, the decrease in community size led to an increase of party cohesion and also enhanced cohesiveness between the sexes, while general sociality remained unchanged. Therefore, our data support the notion that small communities are more cohesive and have a less flexible fission-fusion system.Communicated by D. Watts 相似文献
399.
400.
一种黄土滑坡滑距预测模型 总被引:1,自引:0,他引:1
针对目前黄土滑坡研究现状,本文提出了一种黄土滑坡滑距预测的新模型-模型信息优化处理模型。通过陕西榆林地区5个黄土滑坡的非母体验证,并经与其他预测方法所得的结果相比较,证明该模型精度较高,可用于黄土高原地区的防灾减灾工作。 相似文献