全文获取类型
收费全文 | 42218篇 |
免费 | 528篇 |
国内免费 | 491篇 |
专业分类
安全科学 | 1343篇 |
废物处理 | 1582篇 |
环保管理 | 6070篇 |
综合类 | 6983篇 |
基础理论 | 11713篇 |
环境理论 | 27篇 |
污染及防治 | 10797篇 |
评价与监测 | 2424篇 |
社会与环境 | 1997篇 |
灾害及防治 | 301篇 |
出版年
2022年 | 330篇 |
2021年 | 355篇 |
2020年 | 365篇 |
2019年 | 396篇 |
2018年 | 597篇 |
2017年 | 594篇 |
2016年 | 883篇 |
2015年 | 752篇 |
2014年 | 997篇 |
2013年 | 3143篇 |
2012年 | 1302篇 |
2011年 | 1861篇 |
2010年 | 1507篇 |
2009年 | 1592篇 |
2008年 | 1821篇 |
2007年 | 1944篇 |
2006年 | 1690篇 |
2005年 | 1417篇 |
2004年 | 1423篇 |
2003年 | 1307篇 |
2002年 | 1298篇 |
2001年 | 1635篇 |
2000年 | 1183篇 |
1999年 | 755篇 |
1998年 | 578篇 |
1997年 | 588篇 |
1996年 | 594篇 |
1995年 | 658篇 |
1994年 | 581篇 |
1993年 | 533篇 |
1992年 | 532篇 |
1991年 | 503篇 |
1990年 | 506篇 |
1989年 | 522篇 |
1988年 | 455篇 |
1987年 | 392篇 |
1986年 | 382篇 |
1985年 | 408篇 |
1984年 | 428篇 |
1983年 | 426篇 |
1982年 | 448篇 |
1981年 | 386篇 |
1980年 | 340篇 |
1979年 | 374篇 |
1978年 | 294篇 |
1977年 | 265篇 |
1976年 | 251篇 |
1975年 | 253篇 |
1974年 | 242篇 |
1972年 | 266篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
91.
Anaerobic activated sludge 总被引:3,自引:0,他引:3
92.
Shelter, housing and recovery: a comparison of u.s. Disasters 总被引:3,自引:0,他引:3
In this paper we examine the issues associated with the temporary sheltering and housing of victims after natural disasters in the United States. Specific topics addressed include differential access to shelter and housing aid according to social class, ethnicity and related demographic factors; the relationship between post-disaster shelter and housing and long-term recovery; the role of social support networks in the sheltering of victims; and the implications of the research for the provision of shelter and housing aid after disasters. 相似文献
93.
Stone ML Whiles MR Webber JA Williard KW Reeve JD 《Journal of environmental quality》2005,34(3):907-917
Relationships between riparian land cover, in-stream habitat, water chemistry, and macroinvertebrates were examined in headwater streams draining an agricultural region of Illinois. Macroinvertebrates and organic matter were collected monthly for one year from three intensively monitored streams with a gradient of riparian forest cover (6, 22, and 31% of riparian area). Bioassessments and physical habitat analyses were also performed in these three streams and 12 other nearby headwater streams. The intensively monitored site with the least riparian forest cover had significantly greater percent silt substrates than the sites with medium and high forest cover, and significantly higher very fine organics in substrates than the medium and high forested sites. Macroinvertebrates were abundant in all streams, but communities reflected degraded conditions; noninsect groups, mostly oligochaetes and copepods, dominated density and oligochaetes and mollusks, mostly Sphaerium and Physella, dominated biomass. Of insects, dipterans, mostly Chironomidae, dominated density and dipterans and coleopterans were important contributors to biomass. Collector-gatherers dominated functional structure in all three intensively monitored sites, indicating that functional structure metrics may not be appropriate for assessing these systems. The intensively monitored site with lowest riparian forest cover had significantly greater macroinvertebrate density and biomass, but lowest insect density and biomass. Density and biomass of active collector-filterers (mostly Sphaerium) decreased with increasing riparian forest. Hilsenhoff scores from all 15 sites were significantly correlated with in-stream habitat scores, percent riparian forest, and orthophosphate concentrations, and multiple regression indicated that in-stream habitat was the primary factor influencing biotic integrity. Our results show that these "drainage ditches" harbor abundant macroinvertebrates that are typical of degraded conditions, but that they can reflect gradients of conditions in and around these streams. 相似文献
94.
95.
96.
Personal exposure levels and microenvironmental concentrations of formaldehyde and acetaldehyde in the Helsinki metropolitan area, Finland 总被引:1,自引:0,他引:1
Jurvelin J Vartiainen M Jantunen M Pasanen P 《Journal of the Air & Waste Management Association (1995)》2001,51(1):17-24
Personal 48-hr exposures to formaldehyde and acetaldehyde of 15 randomly selected participants were measured during the summer/autumn of 1997 using Sep-Pak DNPH-Silica cartridges as a part of the EXPOLIS study in Helsinki, Finland. In addition to personal exposures, simultaneous measurements of microenvironmental concentrations were conducted at each participant's residence (indoor and outdoor) and workplace. Mean personal exposure levels were 21.4 ppb for formaldehyde and 7.9 ppb for acetaldehyde. Personal exposures were systematically lower than indoor residential concentrations for both compounds, and ambient air concentrations were lower than both indoor residential concentrations and personal exposure levels. Mean workplace concentrations of both compounds were lower than mean indoor residential concentrations. Correlation between personal exposures and indoor residential concentrations was statistically significant for both compounds. This indicated that indoor residential concentrations of formaldehyde and acetaldehyde are a better estimate of personal exposures than are concentrations in ambient air. In addition, a time-weighted exposure model did not improve the estimation of personal exposures above that obtained using indoor residential concentrations as a surrogate for personal exposures. Correlation between formaldehyde and acetaldehyde was statistically significant in outdoor microenvironments, suggesting that both compounds have similar sources and sinks in ambient urban air. 相似文献
97.
Comparative study of the oxidation of atrazine and acetone by H2O2/UV, Fe(III)/UV, Fe(iii)/H2O2/UV and Fe(II) or Fe(III)/H2O2 总被引:1,自引:0,他引:1
In this study, the rates of degradation of organic compounds by several AOPs (H2O2/UV, Fe(III)/UV, Fe(III)/H2O2/UV, Fe(II)/H2O2 and Fe(III)/H2O2) have been compared. Experiments were carried out at pH ≈ 3 (perchloric acid / sodium perchlorate solutions) and with UV reactors equipped with a low-pressure mercury vapour lamp (emission at 253.7 run). The data obtained with atrazine ([Atrazine]o = 100 μg/L) showed that the rate of degradation of atrazine in very dilute aqueous solution is much more rapid with Fe(III)/UV than with H2O2/UV. Photo-Fenton process (Fe(III)/H2O2/UV) was found to be more efficient than H2O2/UV and Fe(II)/H2O2 for the mineralization of acetone ([Acetone]o = 1 mM). 相似文献
98.
99.
The copepod community observed during an 18-month period at the mouth of eutrophic Kingston Harbour, Jamaica, was dominated
by small species of Parvocalanus, Temora, Oithona, and Corycaeus. Mean copepod biomass was 22.1 mg AFDW m−3 (331 mg m−2). Annual production was 1679 kJ m−2, partitioned as 174 kJ m−2 naupliar, 936 kJ m−2 copepodite, 475 kJ m−2 egg and 93 kJ m−2 exuvial production. All nauplii, most copepodites and many adults, equivalent to half of the biomass and production, were
missed by a standard 200-μm plankton net, emphasizing the importance of nauplii and small species in secondary production
estimates. The evidence suggests that growth rates and production are generally not food limited, and we speculate that size-selective
predation shapes the structure of the harbour community. Biomass and production are higher than previous estimates for tropical
coastal waters, but comparable to other eutrophic tropical embayments and many productive temperate ecosystems. Far from being
regions of low productivity, tropical zooplankton communities may have significant production and deserve greater research
attention than they currently receive.
Received: 19 September 1997 / Accepted: 21 October 1997 相似文献
100.
Stuart J. Marsden 《Conservation biology》1998,12(3):605-611