首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   30261篇
  免费   411篇
  国内免费   435篇
安全科学   939篇
废物处理   1287篇
环保管理   4111篇
综合类   5015篇
基础理论   8129篇
环境理论   11篇
污染及防治   7757篇
评价与监测   1864篇
社会与环境   1786篇
灾害及防治   208篇
  2022年   256篇
  2021年   242篇
  2020年   261篇
  2019年   228篇
  2018年   437篇
  2017年   459篇
  2016年   664篇
  2015年   541篇
  2014年   808篇
  2013年   2401篇
  2012年   1019篇
  2011年   1441篇
  2010年   1167篇
  2009年   1225篇
  2008年   1376篇
  2007年   1456篇
  2006年   1205篇
  2005年   1016篇
  2004年   1031篇
  2003年   986篇
  2002年   933篇
  2001年   1165篇
  2000年   887篇
  1999年   517篇
  1998年   349篇
  1997年   396篇
  1996年   400篇
  1995年   464篇
  1994年   414篇
  1993年   363篇
  1992年   343篇
  1991年   339篇
  1990年   351篇
  1989年   338篇
  1988年   285篇
  1987年   268篇
  1986年   285篇
  1985年   276篇
  1984年   309篇
  1983年   273篇
  1982年   271篇
  1981年   255篇
  1980年   224篇
  1979年   253篇
  1978年   184篇
  1977年   192篇
  1975年   156篇
  1974年   167篇
  1973年   169篇
  1972年   166篇
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
881.
Sexual selection theory predicts that female choice may favour the evolution of elaborate male signals. Darwin also suggested that sexual selection can favour elaborate receiver structures in order to better detect sexual signals, an idea that has been largely ignored. We evaluated this unorthodox perspective by documenting the antennal lengths of male Uraba lugens Walker (Lepidoptera: Nolidae) moths that were attracted to experimentally manipulated emissions of female sex pheromone. Either one or two females were placed in field traps for the duration of their adult lives in order to create differences in the quantity of pheromone emissions from the traps. The mean antennal length of males attracted to field traps baited with a single female was longer than that of males attracted to traps baited with two females, a pattern consistent with Darwin’s prediction assuming the latter emits higher pheromone concentrations. Furthermore, younger females attracted males with longer antennae, which may reflect age-specific changes in pheromone emission. These field experiments provide the first direct evidence of an unappreciated role for sexual selection in the evolution of sexual dimorphism in moth antennae and raise the intriguing possibility that females select males with longer antennae through strategic emission of pheromones.  相似文献   
882.
883.
大气作用下膨胀土地基的水分迁移与胀缩变形分析   总被引:1,自引:0,他引:1  
运用土体渗流和蒸发理论,建立了大气-非饱和土相互作用模型;以现场观测的气象数据作为边界条件,进行了地基土中水分迁移的数值模拟,得到了大气作用下地基土体含水量的动态分布规律.计算结果表明,地基土中含水量变化幅度随深度增加而递减,3.5m深度以下土体的体积含水量基本不变,从而确定了南宁地区膨胀土地基的大气影响层深度为3.5...  相似文献   
884.
Journal of Material Cycles and Waste Management - The daily use of facemask to prevent virus transmission increases the negative effect on the environment because of improper waste disposal. Due to...  相似文献   
885.
港口规划环境影响评价指标体系的研究   总被引:5,自引:0,他引:5  
介绍了规划环境影响评价的发展及应用,根据规划环境影响评价及港口规划的特点,对港口规划环境影响评价的内容、技术路线和指标体系的建立进行了研究,并提出港口规划的环境目标和评价指标,为我国港口规划环境影响评价技术的完善提供借鉴。  相似文献   
886.
Russian Journal of Ecology - Changes in the distribution of broadleaf tree species—Tilia cordata Mill., Quercus robur L., Acer platanoides L., and Ulmus glabra Huds.—in the central part...  相似文献   
887.
Russian Journal of Ecology - A study of the anthropogenic impacts on the on-shore aggregation of true seals was carried out at a haul-out located at the mouth of Piltun Bay (the northeastern part...  相似文献   
888.
Russian Journal of Ecology - To test the hypothesis that animals from habitats exposed to high anthropogenic pressure are more successful in adapting to captivity, immature narrow-skulled voles...  相似文献   
889.
Russian Journal of Ecology - Climate change entails shifts in the ranges of woody plants along both latitudinal and altitudinal gradients in the boreal forest biome. In this study,...  相似文献   
890.
Devils Lake is a terminal lake located in northeast North Dakota. Because of its glacial origin and accumulated salts from evaporation, the lake has a high concentration of sulfate compared to the surrounding water bodies. From 1993 to 2011, Devils Lake water levels rose by ~10 m, which flooded surrounding communities and increased the chance of an overspill to the Sheyenne River. To control the flooding, the State of North Dakota constructed two outlets to pump the lake water to the river. However, the pumped water has raised concerns about of water quality degradation and potential flooding risk of the Sheyenne River. To investigate these perceived impacts, a Soil and Water Assessment Tool (SWAT) model was developed for the Sheyenne River and it was linked to a coupled SWAT and CE‐QUAL‐W2 model that was developed for Devils Lake in a previous study. While the current outlet schedule has attempted to maintain the total river discharge within the confines of a two‐year flood (36 m3/s), our simulation from 2012 to 2018 revealed that the diversion increased the Sheyenne River sulfate concentration from an average of 125 to >750 mg/L. Furthermore, a conceptual optimization model was developed with a goal of better preserving the water quality of the Sheyenne River while effectively mitigating the flooding of Devils Lake. The optimal solution provides a “win–win” outlet management that maintains the efficiency of the outlets while reducing the Sheyenne River sulfate concentration to ≤600 mg/L.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号