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   298篇
  免费   3篇
  国内免费   7篇
安全科学   12篇
废物处理   13篇
环保管理   62篇
综合类   48篇
基础理论   63篇
环境理论   1篇
污染及防治   74篇
评价与监测   22篇
社会与环境   11篇
灾害及防治   2篇
  2023年   2篇
  2022年   3篇
  2020年   3篇
  2019年   7篇
  2018年   6篇
  2017年   4篇
  2016年   8篇
  2015年   5篇
  2014年   8篇
  2013年   32篇
  2012年   11篇
  2011年   24篇
  2010年   9篇
  2009年   8篇
  2008年   17篇
  2007年   21篇
  2006年   14篇
  2005年   20篇
  2004年   8篇
  2003年   11篇
  2002年   15篇
  2001年   7篇
  2000年   2篇
  1999年   4篇
  1998年   8篇
  1997年   4篇
  1996年   3篇
  1995年   3篇
  1994年   6篇
  1993年   4篇
  1992年   2篇
  1991年   1篇
  1990年   3篇
  1989年   2篇
  1985年   4篇
  1984年   1篇
  1983年   3篇
  1982年   3篇
  1979年   2篇
  1978年   1篇
  1977年   1篇
  1974年   1篇
  1932年   1篇
  1931年   1篇
  1930年   2篇
  1928年   1篇
  1926年   1篇
  1925年   1篇
排序方式: 共有308条查询结果,搜索用时 15 毫秒
121.
Previous studies have shown that some female black-capped chickadees (Poecile atricapillus) solicit copulations from males that rank higher in winter flocks than their social mates, and extra-pair paternity in nests occurs commonly enough to be considered a potential female mating tactic. This study uses blood samples collected in 1992–1995 from 58 families of black-capped chickadees to test whether females with extra-pair offspring have chosen extra-pair sires higher in social rank than their mates. Paternity was assessed with multilocus DNA fingerprinting in 1992–1994 nests and with microsatellite and single-locus minisatellite DNA typing in 1995 nests. Seventeen of 58 nests (29.3%) contained young genetically mismatched with their social father. In 11 of 15 cases where the identity of the extra-pair male was known, the extra-pair male was dominant to the social father. Using data from 29 nests located in 1994 and 1995 for which we had the most data on relative ranks of males, high-ranking males had greater realized reproductive success than low-ranking males as a result of extra-pair fertilizations. There was no significant difference between the number of nests containing extra-pair young of females mated to low-ranked versus high-ranked males. Two nests in 1995 contained young either genetically mismatched with both social parents (intraspecific brood parasitism) or, in one nest, genetically mismatched with the social mother but not the social father (quasi-parasitism). The implications of female strategies acquiring genetic benefits through extra-pair copulations are discussed. Received: 7 July 1997 / Accepted after revision: 14 March 1998  相似文献   
122.
123.
Boom and bust dynamics are a prominent characteristic of the crown-of-thorns starfish (Acanthaster planci) populations. Outbreaking starfish populations damage coral communities extensively and then often disappear quickly. In contrast, Onna village, on the central west coast of Okinawa Island, Japan, has been experiencing chronically high population densities of A. planci for decades. In this study, we examined spatial and temporal population dynamics of A. planci along the coast of Onna village, using removal data gathered over 24 years by a local fisheries cooperative. The results demonstrate that A. planci populations along the Onna coast often experienced high densities prior to 2003 and that recently, populations have again been increasing drastically. Size-frequency distributions suggest multiple, successive recruitment, as one of the driving factors maintaining A. planci populations in this location. Moreover, within the Onna area, the timing of outbreak peaks varied among different locations, showing a northward progression.  相似文献   
124.
125.
126.
127.
开恳  陈彬 《环境科技》2005,18(Z1):29-30
介绍了沸石吸附-生物再生活性污泥工艺的对比试验研究结果,试验结果表明沸石可以进行生物再生,再生后的沸石对COD、氨氮的去除效果良好,对于沸石的生物再生效果而言,缺氧/好氧工艺的效果好于单一曝气工艺.  相似文献   
128.
土壤中发生的挥发性有机硫气体的研究   总被引:11,自引:0,他引:11  
测定了张北、封丘、鹰潭、吴县、长沙、湛江等地旱地土壤和水稻土在室内培养情况下挥性有机硫气体的释放。结果表明,这些土壤中产生硫化氢、氧硫化碳、甲基硫醇、二甲基硫、二硫化碳和二甲基二硫等含硫气体。水稻土中产生的有机硫气体高于旱地土壤,同时施用有机肥和化肥后,土壤中发生的有机硫气体高于仅施用化肥,在厌氧条件下检测到的有机硫气体高旱地土壤、同时施用有机肥和化肥后,土壤中发赡有机硫气体高于仅施用化肥。在厌氧  相似文献   
129.
The overall objective of this project was to determine the cost and impacts of Hg control using sorbent injection into a Compact Hybrid Particulate Collector (COHPAC) at Alabama Power's Gaston Unit 3. This test is part of a program funded by the U.S. Department of Energy's National Energy Technology Laboratory (NETL) to obtain the necessary information to assess the costs of controlling Hg from coal-fired utility plants that do not have scrubbers for SO2 control. The economics will be developed based on various levels of Hg control. Gaston Unit 3 was chosen for testing because COHPAC represents a cost-effective retrofit option for utilities with existing electrostatic precipitators (ESPs). COHPAC is an EPRI-patented concept that places a high air-to-cloth ratio baghouse downstream of an existing ESP to improve overall particulate collection efficiency. Activated carbons were injected upstream of COHPAC and downstream of the ESP to obtain performance and operational data. Results were very encouraging, with up to 90% removal of Hg for short operating periods using powdered activated carbon (PAC). During the long-term tests, an average Hg removal efficiency of 78% was measured. The PAC injection rate for the long-term tests was chosen to maintain COHPAC cleaning frequency at less than 1.5 pulses/bag/hr.  相似文献   
130.
Control of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in emissions and thermal residues from incinerators has been a cause of public concern for more than one decade. Recently, several studies showed that other persistent organic pollutants (POPs) such as coplanar polychlorinated biphenyls (co-PCBs) also have dioxin-like activity and are released from incinerators. Therefore, the present study was aimed at making a risk assessment about dioxin-like activity in extracts of thermal waste residues (e.g. combustion gas; fly ash, slag) from incineration and melting processes in Germany and Japan. For this purpose, polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs), coplanar polychlorinated biphenyls (co-PCBs), polychlorinated naphthalenes (PCNs) and polyaromatic hydrocarbons (PAHs) were analyzed by chemical analysis. Additionally, 2, 3, 7, 8-TCDD equivalents (EROD-TEQs) were determined by in vitro Micro-EROD bioassay using rat H4IIE hepatoma cells. EROD-TEQs could be correlated to I-TEQ values (from PCDD/Fs/co-PCBs) analyzed by chemical analysis resulting in a maximal sixfold higher estimate. Our study indicates minor influences of co-PCBs, PAHs and PCNs to the sum of dioxin-like toxicity in the extracts of thermal waste residues as determined here. Furthermore, we showed that the levels of dioxins and co-PCBs contained in slag from melting processes and bottom ashes from incineration processes were lower by 1-2 orders of magnitude than that in fly ash.  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