全文获取类型
收费全文 | 282篇 |
免费 | 6篇 |
国内免费 | 10篇 |
专业分类
安全科学 | 29篇 |
废物处理 | 3篇 |
环保管理 | 31篇 |
综合类 | 36篇 |
基础理论 | 72篇 |
污染及防治 | 110篇 |
评价与监测 | 7篇 |
社会与环境 | 8篇 |
灾害及防治 | 2篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 1篇 |
2021年 | 5篇 |
2020年 | 7篇 |
2019年 | 5篇 |
2018年 | 5篇 |
2017年 | 7篇 |
2016年 | 6篇 |
2015年 | 7篇 |
2014年 | 5篇 |
2013年 | 29篇 |
2012年 | 6篇 |
2011年 | 12篇 |
2010年 | 2篇 |
2009年 | 16篇 |
2008年 | 37篇 |
2007年 | 11篇 |
2006年 | 6篇 |
2005年 | 11篇 |
2004年 | 10篇 |
2003年 | 14篇 |
2002年 | 6篇 |
2001年 | 16篇 |
2000年 | 19篇 |
1999年 | 16篇 |
1998年 | 11篇 |
1997年 | 9篇 |
1995年 | 12篇 |
1993年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有298条查询结果,搜索用时 46 毫秒
91.
A study was conducted in southern Ethiopia to evaluate the nutrient status on smallholder farms with respect to land use class
(garden, grassland, and outfield) and slope position (upper, middle, and lower). Soil physical and chemical properties were
quantified using soil samples collected at two depths (0–15 and 15–30 cm). Available phosphorous was significantly different
among the three land use classes. However, organic carbon and total nitrogen were lower in the outfield compared to the garden
and grass land but not significantly different. The lower than expected nutrient status of the garden and grassland, which
receive almost all available organic supplements, was attributed to the overall low availability of these inputs. Similarly,
pH and cation exchange capacity were not significantly different among the different land use classes. However, the sum of
the exchangeable cations was significantly higher in the garden compared to the outfields. Comparison at landscape level revealed
that the sand fraction was significantly greater, whereas the silt fractions were significantly smaller, on the lower slopes
relative to the middle slopes. Moreover, the organic carbon, total nitrogen, cation exchange capacity, Ca, and Mg values were
significantly less on lower slopes than upper and middle slopes. Perhaps this is because of leaching and the effect of deposition
of coarser sediments from the prevailing gully system. Overall, the fertility of the soil was adequate for supporting smallholder
farming, but consideration must be given to reducing pressure on the land resources, addressing erosion problems, and providing
a line of credit for purchasing inputs. 相似文献
92.
本文将毛泽东的谈话风格概括为广征博引、形散神聚;幽默轻松、寓庄于谐;妙用比喻、以小见大;通俗朴实、平中见奇等四个方面.并认为,高校思想政治理论课教师在教学风格和教学艺术方面应当积极借鉴毛泽东的上述谈话风格,在博览群书的基础上,突破就思想谈思想、就政治讲政治的教学习惯,使思想政治理论课教学进一步丰富化、趣味化、生活化和休闲化. 相似文献
93.
Elke Bruns-Weller 《Umweltwissenschaften und Schadstoff-Forschung》2000,12(3):125-130
Zusammenfassung Es wurden 25 Lebensmittel-, 5 Frauenmilch-, 4 Staub- und 16 Textilproben auf Phthals?ureester untersucht. In allen Proben
waren Phthalate nachweisbar, wobei Di(2-ethylhexyl)phthalat (DEHP) und Di-n-butylphthalat (DBP) am h?ufigsten gefunden wurden.
In Rohmilchproben lagen die Gesamtphthalat-Konzentrationen im Mittel bei 0,1 mg/kg. Konsummilch wies keine h?here Belastung
als Rohmilch auf, auch die Lagerung von Milchproben bis zum Ablauf des Mindesthaltbarkeitsdatums führte nicht zu h?heren Gehalten.
Fettarme Milch war weniger belaster als Vollmilch. Die in Sahneproben gefundenen h?heren DEHP-sowie Gesamptphthalatgehalte
lassen sich durch den h?heren Fettgehalt erkl?ren.
Mit Konzentrationen von bis zu 1,54 mg/kg zeigten gemahlene Haselnüsse, Mandeln und Muskatnüsse, die in Kunststofffolie verpackt
waren, eine vergleichsweise hohe Belastung. In S?uglingsnahrung waren nur Spuren von DEHP und DBP zu finden, weitete Phthals?ureester
konnten nicht nachgewiesen werden. Auch die Frauenmilchproben wiesen nur geringe Gehalte von ca. 0,1 mg/kg auf, eine Akkumulation
der Phthalester im menschlichen K?rper scheint also nicht stattzufinden.
Au?ergew?hnlich hohe Konzentrationen wurden in Staubproben gefunden; die Werte lagen zwischen 300 und 5370 mg/kg Staub, wobei
DEHP die Hauptkomponente darstellte. Die Belastung des Staubes l?sst auf eine erhebliche Bedeutung des Luftpfades beim Transfer
der Phthals?ureester schlie?en. Da Staub erhebliche Anteile an Textilfasern enth?lt, wurden auch Textilien untersucht. Die
Phthals?ureester-Gehalte in den Textilproben reichten von 3,42 bis 34,44 mg/kg. Die hohen Phthalester-Kontaminationen des
Staubes k?nnen daher nicht durch Textilfasern erkl?rt werden.
Online-Publikation: 07. Februar 2000 相似文献
94.
Meaghan A. Vavrek Chris K. Elvidge Robert DeCaire Brenna Belland Christopher D. Jackson Grant E. Brown 《Chemoecology》2008,18(4):255-261
Summary. Several freshwater invertebrate and vertebrate prey species rely on chemosensory cues, including non-injury released disturbance
cues, to assess and avoid local predation threats. The prevailing hypothesis is that a pulse of ammonia released by disturbed
or stressed prey functions as the disturbance cue. Here, we test this hypothesis in two phylogenetically distant freshwater
prey fishes, convict cichlids and rainbow trout. In our first experiment, we measured NH4
+ concentration in tanks containing shoals of cichlid or trout before and after exposure to a realistic model predator (or
left undisturbed). We failed to find an increase in ambient NH4
+ concentration for either cichlids or trout. In our second experiment, we exposed cichlids or trout to NH4
+ at 0.1 or 0.5 mg L−1 (or a distilled water control) and measured the change in antipredator behaviour (time moving, foraging rate and area use).
We found no consistent increase in antipredator behaviour in response to NH4
+. In our third study, we exposed cichlids and trout to the disturbance cues of cichlids or trout (versus the odour of undisturbed
donors). We found significant increases in antipredator behaviour, regardless of donor species, for both cichlids and trout.
Thus, the results of our first two experiments do not support the hypothesis that ammonium functions as a disturbance cue
in prey fishes. However, the results of our final experiment do confirm the use of disturbance cues in convict cichlids and
rainbow trout and support that hypothesis that the disturbance cue is indeed some generalized metabolic byproduct. 相似文献
95.
Summary. To exploit biologically active compounds from white clover (Trifolium repens L.) for suppressing weeds and soil-borne diseases, either as isolated products (biopesticides) or through cultivars with
enhanced production of these compounds, the biologically active compounds must be identified, plant content measured, and
their fate in soil known. The present review summarizes the published knowledge needed for such exploitation; providing essential
information on structure and concentration of flavonols, flavones, condensed tannins, isoflavones, isoflavanones, pterocarpans,
coumestans, cyanogenic glucosides, and saponins in healthy and stressed white clover plants. Various stresses and particular
cultivars affect the concentrations of several of the compounds. Information on biological effects and the degradation/transformation
of these compounds in plants or by microorganisms is available. There is no information on the degradation pathway in soil,
the mechanisms of exudation and leaching of compounds from plants, and soil sorption properties of the compounds. The clover
soil fatigue problem is increasing in grasslands and causes problems especially in organic farming. Research efforts focused
on biological elements of clover soil fatigue have not explained it, and the influence of secondary metabolites has not been
investigated. There are few investigations into the interaction between beneficial fungi/fungal-diseases and the occurrence
of biologically active secondary metabolites in white clover plants. Such studies are critical to better understand beneficial
fungi and pathogens. 相似文献
96.
97.
Fang Xu Ting-Ting Zhu Qing-Quan Rao Sheng-Wen Shui Wen-Wei Li Hong-Bo He Ri-Sheng Yao 《环境科学学报(英文版)》2017,29(3):132-140
Lignocellulosic biomass offers the most abundant renewable resource in replacing traditional fossil resources. However, it is still a major challenge to directly convert the lignin component into value-added materials. The availability of plentiful hydroxyl groups in lignin macromolecules and its unique three-dimensional structure make it an ideal precursor for mesoporous biosorbents. In this work, we reported an environmentally friendly and economically feasible method for the fabrication of mesoporous lignin-based biosorbent (MLBB) from lignocellulosic biomass through a SO3 micro-thermal-explosion process, as a byproduct of microcrystalline cellulose. BET analysis reveal the average pore-size distribution of 5.50 nm, the average pore value of 0.35 cm3/g, and the specific surface area of 186 m2/g. The physicochemical properties of MLBB were studied by fourier transform infrared spectroscopy (FTIR), attenuated-total-reflection fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and element analysis. These results showed that there are large amounts of sulfonic functional groups existing on the surface of this biosorbent. Pb(II) was used as a model heavy-metal-ion to demonstrate the technical feasibility for heavy-metal-ion removal. Considering that lignocellulosic biomass is a naturally abundant and renewable resource and SO3 micro-thermal-explosion is a proven technique, this biosorbent can be easily produced at large scale and become a sustainable and reliable resource for wastewater treatment. 相似文献
98.
Maarten Kroesen Eric J.E. Molin Bert van Wee 《Journal of environmental psychology》2011,31(2):147-157
In this paper, we hypothesize and test the ideas that (1) people’s subjectivity in relation to aircraft noise is shaped by the policy discourse, (2) this results in a limited number of frames towards aircraft noise, (3) the frames inform people how to think and feel about aircraft noise and (4) the distribution of the frames in the population is dependent on structural variables related to the individual. To reveal subjects’ frames of aircraft noise a latent class model is estimated based on survey data gathered among a sample of 250 residents living near Amsterdam Airport Schiphol, a major international airport in the Netherlands. In line with expectations, the results show that there are four evaluative frames of aircraft noise, three of which are strongly linked to the policy discourse. The frames are associated with fitting levels of annoyance response. In turn, frame membership is influenced by two structural variables, namely aircraft noise exposure and noise sensitivity. The results indicate that social factors operate discursively in the explanation of subjective reaction to noise, while psychological factors operate within a traditional cause-and-effect model. The paper concludes with several policy implications. 相似文献
99.
Z. WangR.F. Grant M.A. ArainB.N. Chen N. CoopsR. Hember W.A. KurzD.T. Price G. StinsonJ.A. Trofymow J. Yeluripati Z. Chen 《Ecological modelling》2011,222(17):3236-3249
Forest productivity is strongly affected by seasonal weather patterns and by natural or anthropogenic disturbances. However weather effects on forest productivity are not currently represented in inventory-based models such as CBM-CFS3 used in national forest C accounting programs. To evaluate different approaches to modelling these effects, a model intercomparison was conducted among CBM-CFS3 and four process models (ecosys, CN-CLASS, Can-IBIS and 3PG) over a 2500 ha landscape in the Oyster River (OR) area of British Columbia, Canada. The process models used local weather data to simulate net primary productivity (NPP), net ecosystem productivity (NEP) and net biome productivity (NBP) from 1920 to 2005. Other inputs used by the process and inventory models were generated from soil, land cover and disturbance records. During a period of intense disturbance from 1928 to 1943, simulated NBP diverged considerably among the models. This divergence was attributed to differences among models in the sizes of detrital and humus C stocks in different soil layers to which a uniform set of soil C transformation coefficients was applied during disturbances. After the disturbance period, divergence in modelled NBP among models was much smaller, and attributed mainly to differences in simulated NPP caused by different approaches to modelling weather effects on productivity. In spite of these differences, age-detrended variation in annual NPP and NEP of closed canopy forest stands was negatively correlated with mean daily maximum air temperature during July-September (Tamax) in all process models (R2 = 0.4-0.6), indicating that these correlations were robust. The negative correlation between Tamax and NEP was attributed to different processes in different models, which were tested by comparing CO2 fluxes from these models with those measured by eddy covariance (EC) under contrasting air temperatures (Ta). The general agreement in sensitivity of annual NPP to Tamax among the process models led to the development of a generalized algorithm for weather effects on NPP of coastal temperate coniferous forests for use in inventory-based models such as CBM-CFS3: NPP′ = NPP − 57.1 (Tamax − 18.6), where NPP and NPP′ are the current and temperature-adjusted annual NPP estimates from the inventory-based model, 18.6 is the long-term mean daily maximum air temperature during July-September, and Tamax is the mean value for the current year. Our analysis indicated that the sensitivity of NPP to Tamax was nonlinear, so that this algorithm should not be extrapolated beyond the conditions of this study. However the process-based methodology to estimate weather effects on NPP and NEP developed in this study is widely applicable to other forest types and may be adopted for other inventory based forest carbon cycle models. 相似文献
100.
Grzegorz Owczarek Adam Pościk Zygmunt Kubacki Maciej Karolewski 《International journal of occupational safety and ergonomics》2013,19(3):277-284
With the help of the research results presented here and on the basis of a graphic analysis we aim to prove the existence of a relationship between the difference in prismatic refractive power and the thickness, curvature radius, and type of material used for panoramic oculars in protective spectacles, goggles, and face shields. The difference in the prismatic refractive power is a fundamental optical characteristic of a protective ocular without corrective effect. According to Standard No. EN 165:1995 (European Committee for Standardization, 1995) the difference in the prismatic refractive power is a difference in the prismatic effect at 2 observation points of an eye-protector. 相似文献