全文获取类型
收费全文 | 4897篇 |
免费 | 115篇 |
国内免费 | 74篇 |
专业分类
安全科学 | 226篇 |
废物处理 | 235篇 |
环保管理 | 1324篇 |
综合类 | 449篇 |
基础理论 | 1111篇 |
环境理论 | 5篇 |
污染及防治 | 1174篇 |
评价与监测 | 334篇 |
社会与环境 | 174篇 |
灾害及防治 | 54篇 |
出版年
2023年 | 24篇 |
2022年 | 21篇 |
2021年 | 50篇 |
2020年 | 29篇 |
2019年 | 61篇 |
2018年 | 73篇 |
2017年 | 97篇 |
2016年 | 115篇 |
2015年 | 115篇 |
2014年 | 108篇 |
2013年 | 551篇 |
2012年 | 182篇 |
2011年 | 255篇 |
2010年 | 198篇 |
2009年 | 197篇 |
2008年 | 264篇 |
2007年 | 264篇 |
2006年 | 239篇 |
2005年 | 166篇 |
2004年 | 194篇 |
2003年 | 194篇 |
2002年 | 171篇 |
2001年 | 86篇 |
2000年 | 109篇 |
1999年 | 99篇 |
1998年 | 75篇 |
1997年 | 65篇 |
1996年 | 78篇 |
1995年 | 72篇 |
1994年 | 66篇 |
1993年 | 67篇 |
1992年 | 73篇 |
1991年 | 44篇 |
1990年 | 55篇 |
1989年 | 43篇 |
1988年 | 36篇 |
1987年 | 40篇 |
1986年 | 46篇 |
1985年 | 40篇 |
1984年 | 45篇 |
1983年 | 49篇 |
1982年 | 42篇 |
1981年 | 56篇 |
1980年 | 46篇 |
1979年 | 22篇 |
1978年 | 27篇 |
1977年 | 18篇 |
1976年 | 12篇 |
1975年 | 14篇 |
1971年 | 13篇 |
排序方式: 共有5086条查询结果,搜索用时 0 毫秒
621.
Devon E. Pearse Fred J. Janzen John C. Avise 《Behavioral ecology and sociobiology》2002,51(2):164-171
When females receive no direct benefits from multiple matings, concurrent multiple paternity is often explained by indirect genetic benefits to offspring. To examine such possibilities, we analyzed genetic paternity for 1,272 hatchlings, representing 227 clutches, from a nesting population of painted turtles (Chrysemys picta) on the Mississippi River. Goals were to quantify the incidence and distribution of concurrent multiple paternity across clutches, examine temporal patterns of sperm storage by females, and deduce the extent to which indirect benefits result from polyandrous female behaviors. Blood samples from adult males also allowed us to genetically identify the sires of surveyed clutches and to assess phenotypic variation associated with male fitness. From the genetic data, female and male reproductive success were deduced and then interpreted together with field data to evaluate possible effects of female mating behaviors and sire identity on offspring fitness. We document that more than 30% of the clutches were likely fathered by multiple males, and that presence of multiple paternity was positively correlated with clutch size. Furthermore, the data indicate that the second male to mate typically had high paternity precedence over the first. 相似文献
622.
623.
624.
Patrick C. Mann John L. Mikesell 《Journal of the American Water Resources Association》1979,15(5):1301-1307
ABSTRACT: Several factors theoretically affect the cost behavior of water systems. These factors include scale, consumer density, and per capita usage. This analysis examines the several possible influences on the unit costs of water service. The statistical analyses indicate that among the factors of scale, per capita use, and consumer density, only the first two factors are important influences on water system costs. Water consumers appear to benefit from being served by large systems and being located in service areas characterized by relatively high per capita consumption. There is little statistical evidence indicating that more dense areas can be provided water service at lower costs than less dense areas. 相似文献
625.
Environmental Management - Are societal wastes all bad? Some of them, including heat from power plants and certain organic wastes, have been demonstrated to be potentially valuable for growing... 相似文献
626.
John C. Mycock Rodney A. Gibson Joyce M. Foster James H. Turner 《Environment international》1981,6(1-6)
As a follow-up to a pilot study, a full scale investigation of applying high velocity fabric filtration to coal-fired boiler fly ash control was conducted. Two filter systems were separately applied to two 60,000 lb/h coal-fired boilers. Performance evaluations conducted over the course of a year included total mass removal efficiency and fractional efficiencies. One filtration system employed Teflon felt as the filter media while the second system employed Gore-Tex, a Polytetrofluorethylene (PTFE) laminate on PTFE woven backing. During the course of the year, a limited number of glass felt and woven glass bags were introduced into the house containing Gore-Tex. As a separate option, the second system was outfitted entirely with woven glass bags. Preliminary results indicate acceptable performance at air-to-cloth ratio of 6 to 1. Future plans call for utilizing one of the baghouse systems for SO2 removal. 相似文献
627.
628.
629.
630.
We previously characterized levels of dioxin and dibenzofuran congeners in adipose tissue and plasma fraction of blood collected from 20 adult males, using paired speciments. It has been found that the 2,3,7,8-TCDD level reported on a lipid basis was similar, although not identical, in plasma lipid and in adipose tissue lipid from the same patients, however, higher levels of the more chlorinated dioxins and dibenzofurans existed in plasma lipid as compared to adipose tissue lipid. This study reports measurements from ten individuals' blood cell fraction and compares this to the plasms fraction and to adipose tissue lipid. In all cases where readily detectable amounts of PCDD/Fs were found, a minimum of 85% was in the plasma fraction and less than 15% in the cellular component. Congeners varied in percentage for each component. 相似文献