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   354篇
  免费   26篇
  国内免费   45篇
安全科学   14篇
废物处理   9篇
环保管理   75篇
综合类   151篇
基础理论   97篇
污染及防治   41篇
评价与监测   11篇
社会与环境   11篇
灾害及防治   16篇
  2023年   7篇
  2022年   3篇
  2021年   8篇
  2020年   11篇
  2019年   5篇
  2018年   7篇
  2017年   9篇
  2016年   13篇
  2015年   13篇
  2014年   20篇
  2013年   40篇
  2012年   29篇
  2011年   29篇
  2010年   14篇
  2009年   25篇
  2008年   19篇
  2007年   19篇
  2006年   20篇
  2005年   23篇
  2004年   11篇
  2003年   12篇
  2002年   6篇
  2001年   8篇
  2000年   9篇
  1999年   11篇
  1998年   4篇
  1997年   5篇
  1996年   5篇
  1995年   4篇
  1994年   2篇
  1993年   5篇
  1992年   2篇
  1991年   2篇
  1990年   2篇
  1989年   1篇
  1988年   2篇
  1987年   1篇
  1986年   1篇
  1985年   4篇
  1984年   3篇
  1983年   1篇
  1982年   3篇
  1980年   1篇
  1979年   3篇
  1974年   1篇
  1969年   2篇
排序方式: 共有425条查询结果,搜索用时 0 毫秒
181.
浅论循环经济与环境污染综合治理   总被引:4,自引:0,他引:4  
介绍循环经济的主要特征及其对环境、资源的有利影响,指出化工企业的发展应走新型工业化道路。  相似文献   
182.
固定化细胞技术处理含酚废水的研究   总被引:9,自引:0,他引:9  
固定化细胞技术的关键是所用载体材料的性能。本文力求寻找一种价格低、寿命长、效率高的载体。通过同一菌种在固定状态和游离状态降解含酚废水的实验对比,证明红砖碎粒是一种优良的载体材料。利用正交实验,确定了该菌种在固定时的最佳运行条件。并对游离细胞和固定细胞降解苯酚的过程进行了动力学分析。结果表明,在两种情况下,该菌种降解苯酚的过程均符合Monod模型。  相似文献   
183.
Thalli of the red alga Audouinella saviana were exposed to 600 microM Cd2+ (LC50), 1000 microM Cd2+ and 1500 microM Cd2+ (final concentrations) for 5, 10 and 15 days (each dose) by adding cadmium nitrate to the culture medium. Untreated thalli were set in triplicate as controls for each experiment. Ultrastructural modifications due to cadmium ad/absorption were observed by TEM/SEM electron microscopy. SEM-EDS X-ray microanalysis, definining the accumulation sites, was performed on cryoprepared samples. TEM studies showed striking changes in the plasmalemma of treated algae, which became irregular and convoluted. Electron-transparent exocytic vesicles, possibly related to cell wall polysaccharide synthesis, were observed. The appearance of ribosomes and Golgi bodies, not significantly present in the cytoplasms of untreated cells, suggested enhanced protein and carbohydrate biosynthesis. The cell walls lost their initial grooves and became smooth and thick. More or less electron-dense vesicular systems were formed. Electron-dense sphaeroids occurred in the plasmalemma-cell wall interface, in the cell wall itself and in nearby vesicular membrane systems. Many small vacuoles containing large metal complexes were formed. Complexes were then sequestered into a large vacuole. SEM observations demonstrated that the cell wall and the membrane systems were the most involved in the defense responses. EDS-X-ray microanalysis confirmed the presence of cadmium in these compartments. Chloroplasts, where no Cd2+ signal was detected, were the least affected organelles, showing only a partial disorganization after lengthy exposure to high Cd2+ concentrations.  相似文献   
184.
通过对发生在浙江省近岸海域一次特大面积赤潮的剖析,阐述了赤潮造成的危害,探索了赤潮爆发的原因,最后还对如何防落赤潮提出了对策措施。  相似文献   
185.
Gastropod shells are limited resources for most hermit crab species, acting as primary factors in various aspects of their biology. To investigate the efficacy of different behavioral tactics adopted for their acquisition (locomotion, attendance at shell-supplying sites, interactions with conspecifics in aggregation) we conducted observations and experiments at a salt marsh in New England (USA). Locomotion, fast and meandering, significantly increased the chances of encountering empty shells and conspecifics. However, shell exchanges were rare. Simulated gastropod predation sites quickly attracted a larger number of hermit crabs than the other shell-supplying sites tested (live and dead conspecifics, live snails) and induced the rapid occupancy of all the empty shells offered, usually by the first crabs arriving at the site. Aggregations seemed not to function as shell exchange markets, as previously suggested for several other species. In the short run, exploitation seems to be more efficient for the acquisition of new shells by Pagurus longicarpus. In the long run, it is the density of nondestructive gastropod predators that regulates the availability of new shells of good quality in the pool available to this hermit crab species.  相似文献   
186.
A number of socioecological models assume that within-group food competition is either weak or absent among folivorous primates. This assumption is made because their food resources are presumed to be superabundant and evenly dispersed. However, recent evidence increasingly suggests that folivore group size is food-limited, that the primates prefer patchily distributed high-quality foods, and display some of the expected responses to within-group scramble competition. To investigate this apparent contradiction between theoretical models and recent empirical data, we examined the foraging behaviour of red colobus monkeys (Piliocolobus tephrosceles) in Kibale National Park, Uganda. We found that red colobus monkeys foraged in a manner that suggests they deplete patches of preferred foods: intake rate slowed significantly during patch occupancy while movement rate, an index of foraging effort, increased. Furthermore, patch occupancy was related to the size of the feeding group and the size of the patch. These results suggest that within-group scramble competition occurs, may limit folivore group size, and should be considered in models of folivore behavioural ecology.  相似文献   
187.
水资源与城镇化的关系问题是水科学研究的热点,二者之间存在着复杂的交织关系。论文选取典型干旱区城市张掖市为研究对象,以最严格水资源管理制度为约束条件,基于水资源约束下的城镇化水平阈值计算思路,引入节水量和灰水足迹测算方法改进了传统水量水质双要素水资源承载力计算模型,并在此基础上统筹可供水量、可节水量及水功能区纳污能力构建了水资源管理“三条红线”约束下的城镇化水平阈值计算模型;通过分析张掖市城镇化水平与水资源开发利用的历史数据并进行情景模拟,对2020年和2030年张掖市城镇化水平阈值做出了预测。结果表明:1)在水资源开发利用红线约束下,到2030年张掖市可利用水资源量为23.02×108 m3,与现状基本一致,且以当前的水资源开发利用水平,水量承载能力难以支撑政府未来规划中的城镇化进程与经济增长的用水需求;2)严格遵照用水效率控制红线中所规定的用水定额标准时,张掖市将有望改善水量承载能力不足问题,且到2030年时,水量承载城镇人口能力可达331.91×104人,其中水量承载能力提升主要得益于农业部门节水;3)在水功能区限制纳污红线的约束下,2030年张掖市水质可承载能力上限为62.47×104人,仅为规划城镇人口数量的78%,水质可承载能力对城镇化进程形成了强烈的约束作用,约束力主要来自于城镇区域氨氮排放;4)在水资源管理“三条红线”约束下,到2030年时张掖市城镇化水平阈值上限为48.05%。  相似文献   
188.
Global amphibian declines are one of the biggest challenges currently facing the conservation community, and captive breeding is one way to address this crisis. Using information from the International Species Information System zoo network, we examined trends in global zoo amphibian holdings across species, zoo region, and species geographical region of origin from 1994 to 2014. These trends were compared before and after the 2004 Global Amphibian Assessment to assess whether any changes occurred and whether zoo amphibian conservation effort had increased. The numbers of globally threatened species (GTS) and their proportional representation in global zoo holdings increased and this rate of increase was significantly greater after 2004. North American, European, and Oceanian GTS were best represented in zoos globally, and proportions of Oceanian GTS held increased the most since 2004. South American and Asian GTS had the lowest proportional representation in zoos. At a regional zoo level, European zoos held the lowest proportions of GTS, and this proportion did not increase after 2004. Since 1994, the number of species held in viable populations has increased, and these species are distributed among more institutions. However, as of 2014, zoos held 6.2% of globally threatened amphibians, a much smaller figure than for other vertebrate groups and one that falls considerably short of the number of species for which ex situ management may be desirable. Although the increased effort zoos have put into amphibian conservation over the past 20 years is encouraging, more focus is needed on ex situ conservation priority species. This includes building expertise and capacity in countries that hold them and tracking existing conservation efforts if the evidence‐based approach to amphibian conservation planning at a global level is to be further developed.  相似文献   
189.
Abstract: An essential foundation of any science is a standard lexicon. Any given conservation project can be described in terms of the biodiversity targets, direct threats, contributing factors at the project site, and the conservation actions that the project team is employing to change the situation. These common elements can be linked in a causal chain, which represents a theory of change about how the conservation actions are intended to bring about desired project outcomes. If project teams want to describe and share their work and learn from one another, they need a standard and precise lexicon to specifically describe each node along this chain. To date, there have been several independent efforts to develop standard classifications for the direct threats that affect biodiversity and the conservation actions required to counteract these threats. Recognizing that it is far more effective to have only one accepted global scheme, we merged these separate efforts into unified classifications of threats and actions, which we present here. Each classification is a hierarchical listing of terms and associated definitions. The classifications are comprehensive and exclusive at the upper levels of the hierarchy, expandable at the lower levels, and simple, consistent, and scalable at all levels. We tested these classifications by applying them post hoc to 1191 threatened bird species and 737 conservation projects. Almost all threats and actions could be assigned to the new classification systems, save for some cases lacking detailed information. Furthermore, the new classification systems provided an improved way of analyzing and comparing information across projects when compared with earlier systems. We believe that widespread adoption of these classifications will help practitioners more systematically identify threats and appropriate actions, managers to more efficiently set priorities and allocate resources, and most important, facilitate cross‐project learning and the development of a systematic science of conservation.  相似文献   
190.
浙江近岸海域有害赤潮发生区麻痹性贝毒素研究   总被引:4,自引:0,他引:4  
用小白鼠生物检测法和高效液相色谱法对采自浙江舟山海域和浙江中南部海域的麻痹性贝毒素进行了调查分析。结果表明,浙江舟山海域六横岛的西格织纹螺含有贝毒,其毒素为3,7Mu/g,舟山海域有毒贝类检出率为3.1%;浙江中南部海域南麂列岛的棒锥螺含有贝毒,其毒素〈1.7Mu/g,浙江中、南部海域有毒贝类检出率为9.1%。  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