全文获取类型
收费全文 | 2309篇 |
免费 | 45篇 |
国内免费 | 389篇 |
专业分类
安全科学 | 107篇 |
废物处理 | 133篇 |
环保管理 | 213篇 |
综合类 | 711篇 |
基础理论 | 514篇 |
环境理论 | 1篇 |
污染及防治 | 708篇 |
评价与监测 | 135篇 |
社会与环境 | 151篇 |
灾害及防治 | 70篇 |
出版年
2023年 | 40篇 |
2022年 | 99篇 |
2021年 | 47篇 |
2020年 | 35篇 |
2019年 | 40篇 |
2018年 | 88篇 |
2017年 | 65篇 |
2016年 | 70篇 |
2015年 | 107篇 |
2014年 | 102篇 |
2013年 | 210篇 |
2012年 | 112篇 |
2011年 | 165篇 |
2010年 | 141篇 |
2009年 | 122篇 |
2008年 | 140篇 |
2007年 | 110篇 |
2006年 | 93篇 |
2005年 | 92篇 |
2004年 | 107篇 |
2003年 | 90篇 |
2002年 | 68篇 |
2001年 | 122篇 |
2000年 | 62篇 |
1999年 | 50篇 |
1998年 | 36篇 |
1997年 | 24篇 |
1996年 | 24篇 |
1995年 | 41篇 |
1994年 | 16篇 |
1993年 | 14篇 |
1992年 | 18篇 |
1991年 | 12篇 |
1990年 | 12篇 |
1989年 | 11篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1985年 | 8篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1980年 | 6篇 |
1975年 | 8篇 |
1974年 | 10篇 |
1973年 | 7篇 |
1972年 | 12篇 |
1966年 | 5篇 |
1965年 | 5篇 |
1959年 | 5篇 |
1957年 | 5篇 |
排序方式: 共有2743条查询结果,搜索用时 15 毫秒
871.
Predictions of binary sorption isotherms for the sorption of heavy metals by pine bark using single isotherm data 总被引:1,自引:0,他引:1
The adsorption of three heavy metal ions by pine bark was studied. The study was divided into two parts; single component adsorption of the metals Cu2+, Cd2+ and Ni2+ and bisolute adsorption of the three binary systems Cu2+-Cd2+, Cu2+-Ni2+ and Cd2+-Ni2+. Extended Langmuir model, extended Freundlich model. Sips model and ideal adsorption solution theory (IAST) models were used to predict the equilibrium uptake for Cu2+, Cd2+ and Ni2+ in the binary diluted solutions using the single adsorption constants. The experimental data of single isotherm adsorption process were found to follow Langmuir isotherm model with less accuracy than Freundlich and Sips models. Whereas, the predictions of bisolute adsorption isotherms of the mentioned three systems, Cu2+-Cd2+, Cu2+-Ni2+ and Cd2+-Ni2+, showed good agreement with experimental data when using Extended-Langmuir, Extended-Freundlich and IAST. However, the only good fit of the Sips model was with the Cu2+-Cd2+ system. 相似文献
872.
The thermogenic curves of the metabolism of mitochondria isolated from the heart of chicken Star-cross 288 and the effect of La3+ on it were studied by using an LKB-2277 BioActivity Monitor, ampoule method, at 37 degrees C. After isolation from the chicken heart tissue, mitochondria still have metabolic activity and can live for a long time by using the stored nutrients. From the thermogenic curves, we obtained the thermokinetic equations under different conditions. The kinetics show that La3+ has changed the metabolism completely. 相似文献
873.
Performance of Trickle-Bed Air Biofilter: A Comparative Study of a Hydrophilic and a Hydrophobic Voc
Two lab-scale trickle-bed air biofilters were operated for investigating the difference in performance between a hydrophilic
and a hydrophobic volatile organic compound (VOC). Methyl isobutyl ketone (MIBK) and styrene were selected as a model hydrophilic
and hydrophobic VOCs, respectively. Effects of loading rates, biofilter re-acclimation, removal profile along biofilter depth,
nitrogen consumption, and CO2 production were compared under three operating conditions, namely, backwashing and two non-use periods (starvation and stagnant).
Consistent over 99% removal efficiency up to loading rates of 3.26 kg COD/m3-day was obtained for the MIBK biofilter at 0.76 min empty bed retention time (EBRT) and 1.5 L/d nutrient flow. A similar
performance for the styrene biofilter was obtained for loading rates up to 1.9kg COD/m3-day at 2.02 min EBRT and 2.4 L/d nutrient flow. The MIBK biofilter required only an initial acclimation period of 16 days
while styrene biofilter required 46 days. Non-use periods can be used as another means of biomass control for both biofilters
when the employed loading rate did not exceed 1.27 and 2.17 kg COD/m3-day for styrene and MIBK biofilters, respectively. The re-acclimation of both biofilter was delayed with increase of loading
rate. MIBK biofilter re-acclimated in 90 min, while styrene biofilter re-acclimated in more than 600 min. Under similar loading
rates, MIBK biofilter utilized less biofilter depth than styrene biofilter. Nitrogen consumption behaviors were apparently
different between the two biofilters. Styrene biofilter had higher CO2 production than MIBK biofilter and its CO2 production was closely related to the theoretical complete chemical oxidation. 相似文献
874.
崔秀敏 《中国个体防护装备》2006,(5):42-44
目前,我国国家标准、行业标准、地方标准和企业标准,在编写格式、结构和引用文件方面都有特定的要求,其主要的指导性文件为GB/T1.1—2000《标准化工作导则第1部分:标准的结构和编写规则》、GB/T1.2—2002(标准化工作导则第2部分:标准中规范性技术要素内容的确定方法》。国家军用标准、军队部门标准编写的主要指导性文件为GJB0.1—2001《军用标准文件编制工作导则第1部分:军用标准和指导性技术文件编写规定》、GJB0.2—2001《军用标准文件编制工作导则第2部分:军用规范编写规定》和GJB0.3—2001((军用标准文件编制工作导则第3部分:出版印刷规定》。GJB0.1-0.3-2001与GB/T1.1-2000、GB/T1.2-2002相辅相成,技术内容基本一致,但标准格式、结构和技术要素各有侧重。 相似文献
875.
Olfactory perception and orientation behaviour of female and male flour beetles (Tribolium castaneum, T. confusum) to single stereoisomers of their aggregation pheromone revealed maximal receptor potentials and optimal attraction in response to 4R,8R-(?)-dimethyldecanal, whereas its optical antipode 4S,8S-(+)-dimethyldecanal was found to be inactive in this respect. Female flour beetles of both species were ≈ 103 times less attracted to 4R,8S-(+)- and 4S,8R-(?)-dimethyldecanal than to 4R,8R-(?)-dimethyldecanal, while male flour beetles failed to respond to the R,S-(+)- and S,R-(?)-stereoisomers. Pheromone extracts of prothoracic femora from unmated male flour beetles elicited higher receptor potentials in the antennae of females than in those of males. The results suggest that the aggregation pheromone emitted by maleT. castaneum as well as maleT. confusum has the stereochemical structure of 4R,8R-(?)-dimethyl-decanal, which acts as sex attractant for the females and as aggregant for the males of both species. 相似文献
876.
Summary Success of the hider strategy in ungulates depends, in part, on the mother's ability to minimize information she transmits about her young's hiding place while remaining close enough to distract or drive away a predator. We predicted that pronghorn (Antilocapra americana) mothers should: (1) maintain minimum distances from their hidden fawns sufficient to cause the expected energy gain for a ground predator, systematically searching around the mother, to fall below that expected when searching for some other prey; (2) orient the axes of either head or trunk towald the hidden fawn no more frequently than would be expected by chance; (3) schedule behavior so that no activity is more likely than another to occur when a visit to the hidden fawn is imminent. At the National Bison Range, where coyote (Canis latrans) predation on pronghorn fawns is frequent, pronghorn mothers conform to predictions (1) and (3), but not (2). Within the first 10% of their time away from fawns, mothers reached an average distance of 70.4 m from their fawns' biding places and remained at that distance until 95% of their time away was clapsed. At this mother-fawn distance a coyote, using the mother's position to begin a systematic search for the fawn, and searching at a rate of 4 m2/s, would gain energy at a lower rate than it would hunting ground squirrels (Spermophilus columbianus). Mothers pointed both head and trunk toward their hidden fawns more frequently than would be expected by chance and coyotes, able to use this information to establish a 90° quadrant to search, could expect rates of gain higher than those obtainable in 360° search. Mothers especially tended to orient both head and trunk toward their fawns when standing or moving. Coyotes that begin a 90° search based on the mother's head or trunk position only when mothers were standing or moving, could expect rates of energy gain almost double those expected in 360° search or ground squirrel hunting. Maternal activities (stand, feed, recline, or move) were distributed evenly across all mother-fawn distances and across percent total time away from the fawn. Thus, activity was not a good predictor of a mother's likelihood of soon returning to her fawn. Mothers also remained away from their fawns long enough to cause the expected rate of energy gain for a coyote hiding and watching for the mother's return to the fawn to fall well below the rate expected for searching or ground squirrel hunting. 相似文献
877.
Joseph Z. Z. Matowanyika 《The Environmentalist》1991,11(2):85-94
Summary Sustainable development is high on development analysts' agendas as people seek viable alternatives to current development concepts. These latter approaches have not satisfied people's livelihoods especially in developing countries. This paper suggests that the promotion of sustainable development must correctly identify the contexts within which it is to be pursued. It is essential to note that this is best done if people recognize that as a complex concept, sustainable development has several dimensions, including the resource base of a country/community/society; external factors impacting on it; internal factors at play within; population factors and political economic factors.For rural Africa, the context is one of small community and kinship based production groups largely dependent on their local environments for survival. It is essential to identify endogenous factors such as local knowledge bases, common property arrangements, other local social institutions and local environmental practices and to base sustainability strategies on these.There is growing awareness of the efficacy of these local indigenous systems but constraints to their promotion as a valuable resource are also significant. There is room for being hopeful that rural Africa might sustain itself if recognition of the correct contexts is sought.Mr Joseph Z.Z. Matowanyika obtained his Bachelor's and Master's Degrees respectively at the Universities of Reading and Nottingham, in the UK. He is currently undertaking research in the Department of Geography of the University of Waterloo for a Doctor of Philosophy. 相似文献
878.
879.
880.