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   4050篇
  免费   33篇
  国内免费   14篇
安全科学   43篇
废物处理   262篇
环保管理   250篇
综合类   658篇
基础理论   819篇
环境理论   4篇
污染及防治   1431篇
评价与监测   378篇
社会与环境   244篇
灾害及防治   8篇
  2023年   44篇
  2022年   125篇
  2021年   124篇
  2020年   47篇
  2019年   51篇
  2018年   148篇
  2017年   109篇
  2016年   205篇
  2015年   109篇
  2014年   229篇
  2013年   388篇
  2012年   248篇
  2011年   242篇
  2010年   185篇
  2009年   139篇
  2008年   231篇
  2007年   232篇
  2006年   211篇
  2005年   146篇
  2004年   119篇
  2003年   107篇
  2002年   94篇
  2001年   59篇
  2000年   44篇
  1999年   34篇
  1998年   13篇
  1997年   12篇
  1996年   9篇
  1995年   23篇
  1994年   17篇
  1993年   12篇
  1992年   8篇
  1990年   10篇
  1989年   11篇
  1982年   6篇
  1970年   6篇
  1967年   7篇
  1966年   11篇
  1965年   15篇
  1964年   31篇
  1963年   12篇
  1962年   17篇
  1961年   11篇
  1960年   9篇
  1959年   27篇
  1958年   25篇
  1957年   18篇
  1956年   14篇
  1955年   18篇
  1954年   8篇
排序方式: 共有4097条查询结果,搜索用时 10 毫秒
681.
682.
Summary. We investigated the hypothesis that aggregation signals produced by male webbing clothes moths (WCM), Tineola bisselliella (Hum.) (Lepidoptera: Tineidae), and close-range male attractant signals produced by females have a pheromonal basis, at least in part. Gas chromatographic-electroantennographic detection (GC-EAD) and GC-mass spectrometric analyses of bioactive methanolic extracts of male WCM disclosed three candidate pheromone components: hexadecanoic acid methyl ester (16:Ester), (Z)-9-hexadecenoic acid methyl ester (Z9—16:Ester), and octadecanoic acid methyl ester (18:Ester). In bioassay experiments in a large Plexiglas™ arena, a blend of synthetic 16:Ester plus Z9—16:Ester was attractive to male and virgin (but not mated) female WCM; the 18:Ester was inactive. GC-EAD analyses of pheromone gland extracts from female WCM revealed (E,Z)-2,13-octadecadienal (E2Z13—18:Ald) and (E,Z)-2,13-octadecadienol (E2Z13—18:OH) as candidate sex pheromone components. In arena bioassay experiments, 1—5 female equivalents of synthetic E2Z13—18:Ald (0.2 ng) and E2Z13—18:OH (0.1 ng) were more attractive to male WCM than were two virgin female WCM. We anticipate that the combination of aggregation and sex pheromones, male-produced sonic aggregation signals, and habitat-derived semiochemicals will be highly effective in attracting male and female WCM to commercial traps. Received 12 January 2001; accepted 8 June 2001.  相似文献   
683.
With the aim of optimizing protocols for sampling moss, pine and oak for biomonitoring of atmospheric contamination and also for inclusion in an Environmental Specimen Bank, 50 sampling units of each species were collected from the study area for individual analysis. Levels of Ca, Cu, Fe, Hg, Ni, and Zn in the plants were determined and the distributions of the concentrations studied. In moss samples, the concentrations of Cu, Ni and Zn, considered to be trace pollutants in this species, showed highly variable long-normal distributions; in pine and oak samples only Ni concentrations were log-normally distributed. In addition to analytical error, the two main source of error found to be associated with making a collective sample were: (1) not carrying out measurements on individual sampling units; and (2) the number of sampling units collected and the corresponding sources of variation (microspatial, age and interindividual). We recommend that a minimum of 30 sampling units are collected when contamination is suspected.  相似文献   
684.
685.
686.
687.
Summary. Female Photuris fireflies contain defensive chemicals of two types. They sequester steroidal pyrones (lucibufagins) from male fireflies of the genus Photinus that they eat, and themselves produce the defensive betaine N-methylquinolinium 2-carboxylate. Chemical analyses of Photuris eggs showed that females that fed on Photinus males endow their eggs with both lucibufagin and the betaine, while those that did not feed on Photinus lay eggs that contain betaine, but virtually no lucibufagin. Photuris females collected in the field during the Photinus flight season laid eggs that invariably contained betaine, but lucibufagin only at times. Predation experiments showed that Photuris eggs are essentially unacceptable to larvae of a coccinellid beetle (Harmonia axyridis) and an ant (Leptothorax longispinosus), but moderately acceptable to an earwig (Forficula auricularia). When applied experimentally to palatable insect eggs, lucibufagin proved deterrent to these three predators, while the betaine proved deterrent to the ant and coccinellid larva only. Both types of defensive compound decreased egg predation in the field. By endowing their eggs with both exogenous and endogenous chemicals, Photuris females are essentially “maximizing their options”– when feeding on Photinus, their eggs are doubly protected, but they are not entirely defenseless when the females are unable to procure lucibufagin. Received 12 August 1999; accepted 27 August 1999  相似文献   
688.
Environmental Science and Pollution Research - A complete survey is presented on the inorganic composition of the euhalophyte annual succulent species Salicornia patula (Chenopodiaceae), including...  相似文献   
689.
690.
Journal of Material Cycles and Waste Management - Leather production is a technology that boosts the economy because of its versatility and durability. However, the wastes generated throughout the...  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