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71.
大气棕碳(BrC)是对大气颗粒物中具有吸光能力的一类有机物的总称,其对空气能见度及气候系统均有重要影响.自2021年3月至2022年2月底于南京北郊利用黑碳仪测定了气溶胶中BrC的光吸收系数,利用最小相关性法分别定量一次(BrCpri)和二次棕碳(BrCsec)贡献,结合后向轨迹、潜在来源和日均变化,分析季节变化特征.结果表明,观测期间BrC的平均光吸收系数(370 nm)为(7.76±7.17)Mm-1,对于总气溶胶光吸收贡献率为(22.0±8.8)%.不同波长下棕碳吸光系数在四季呈现U字形变化,即春季和冬季高,夏季和秋季低.BrCpri和BrCsec(370 nm)全年光吸收贡献分别为(62.9±21.4)%和(37.1±21.4)%;前者在四季均占主导,但随着波长增加,BrCsec的贡献逐渐增加并最终占主导(如在660 nm时).除冬季以外,BrC在其他季节受到来自海上气团的显著影响,而冬季受当地及周边地区排放影响更为显著.交通排放在春、夏和秋季对一... 相似文献
72.
为了评估非寄主植物次生物质对褐飞虱3~4龄若虫的驱避与触杀活性,本文用乙醇浸提了11种在华南地区分布广泛的植物获得其乙醇提取物。分析了这11种植物乙醇提取物对褐飞虱3~4龄若虫的驱避作用,采用药膜法测定了其对褐飞虱3~4龄若虫的触杀作用。结果表明,10 mg·mL-1的质量浓度下,花椒(Zanthoxylum bungeanum)和小茴香(Foeniculum vulgare)提取物对褐飞虱若虫有显著地拒避作用,24 h的拒避率分别为53.3%和43.3%;塞楝(Khaya senegalensis)、胜红蓟(Ageratum conyzoides)、桉树(Eucalyptus exsetrta)和毛麻楝(Chukrasia tabularis)提取物对褐飞虱若虫有显著地引诱作用,24 h着落率分别为75.0%、73.3%、73.3%和71.7%。花椒和小茴香提取物对褐飞虱若虫的拒避作用随着质量浓度的上升而增加,在10~40 mg·mL-1的质量浓度下均对褐飞虱3~4龄若虫有显著地拒避活性,40 mg·mL-1时拒避作用最明显,24 h拒避率分别为66.7%和60.0%。塞楝、胜红蓟、桉树和毛麻楝提取物对褐飞虱若虫的引诱作用均随着质量浓度的上升先增加后降低。塞楝和毛麻楝乙醇提取物对褐飞虱若虫的拒避与引诱活性因其质量浓度的不同而有差异,当质量浓度小时(10 mg·mL1)对褐飞虱若虫有显著地引诱作用;当质量浓度大时(40 mg·mL1)对褐飞虱若虫有显著地拒避作用,24 h后,拒避率分别为50.0%和40.0%。胜红蓟乙醇提取物在5和10 mg·mL-1的质量浓度下对褐飞虱若虫具有显著地引诱作用,24 h后,着落率分别为71.7%和73.3%;桉树乙醇提取物在10和20 mg·mL-1的质量浓度下对褐飞虱若虫具有显著地引诱作用,24 h后,着落率分别为73.3%和71.7%。辣椒(Capsicum annuum)、小茴香、花椒、胜红蓟和鬼针草(Bidens pilosa)乙醇提取物对褐飞虱若虫的触杀活性效果显著,在95.69μg·cm-2的剂量下,24 h校正死亡率达到85%以上,LD50值依次为15.46,25.66,33.61,33.57和37.85μg·cm-2。塞楝和蟛蜞菊(Wedelia chinensis)提取物对褐飞虱若虫也具有较好地触杀活性,在95.69μg·cm-2的剂量下,24 h校正死亡率达到50%以上。研究所选11种不同科属非寄主植物的乙醇提取物在一定质量浓度下,对褐飞虱均会产生不同程度的拒避作用。其中辣椒、小茴香、花椒、胜红蓟和鬼针草5种植物乙醇提取物对褐飞虱若虫的触杀效果明显。辣椒、小茴香、花椒属于经济作物,本研究表明,这3种作物还具有开发为生物农药的价值。胜红蓟和鬼针草在华南地区分布广泛,易采集,植物资源丰富,具有开发成植物源杀虫剂的巨大潜力。 相似文献
73.
William L. Goodfellow Dennis T. Burton William C. Graves Lenwood W. Hall Keith R. Cooper 《Journal of the American Water Resources Association》1983,19(4):641-648
ABSTRACT Picric acid (2,4,6-trinitrophenol) and picramic acid (2-amino-4,6-dinitrophenol) are potential water pollutents due to a variety of industrial and munition uses. The possible impacts of picric and picramic acid to two recreationally and commercially important species, rainbow trout, Salmo gairdneri, and American oysters, Crassostrea virginica, were evaluated. Picramic acid was more toxic than picric acid to both species tested. The 96-h LC50s for picric and picramic acids for rainbow trout were 109.6 and 46.2 mg/1, respectively. The 144-h LC50s for picric and picramic acid for American oysters were 254.9 and 69.8 mg/1, respectively. Sublethal no growth EC50s and shell deposition EC50s for oysters showed that both compounds caused adverse effects at much lower concentrations than indicated by the LC50s. For example, the 144-h shell deposition EC50s were 27.9 mg/1 for picric acid and 5.6 mg/1 for picramic acid. Sediment adsorbtion studies in estuarine water indicated that both compounds are not readily adsorbed which suggests that sediment would not play a major role as a sink in contaminated systems. Oysters, which filter large quantities of particulate matter, would more likely be affected by picric and picramic acids in the water column than by exposure to contaminated sediment. 相似文献
74.
Bjørn Mejdell Larsen Odd Terje Sandlund Hans Mack Berger Trygve Hesthagen 《Water, Air, & Soil Pollution: Focus》2007,7(1-3):285-291
We describe the development of the fish community in the acidified and limed river Litleåna in southern Norway, and describe how chemical restoration, compensatory introductions of exotics, and accidental invasion of exotics interact to influence the population of the naturally occurring brown trout (Salmo trutta). The river Litleåna is a tributary to the river Kvina in Vest-Agder County, southern Norway. During the years 1996–2004, annual mean pH was 4.9–5.0 and 6.1–6.4 above and below the liming facility, which was installed in 1994. Originally, brown trout was the only fish species in the river, but brook trout (Salvelinus fontinalis) have been intentionally introduced, whereas European minnow (Phoxinus phoxinus) was introduced by accident. Fish densities were recorded by means of electrofishing annually over the ten year period 1995–2004. Although close to extinction before liming was initiated, brown trout fry densities increased from 1995 to 1999, with subsequent varying densities. There has been a simultaneous major increase in the occurrence and density of European minnow since 1997. Our results show that both brown trout and European minnow increase after liming. Minnow densities are negatively affected by low pH episodes in the river. The growth rates of brown trout fry are negatively correlated to minnow densities, indicating competition between the species. Brook trout densities have decreased since liming started, and during the brown trout recovery. 相似文献
75.
76.
通过对阜新市高德东山矿山废弃地的总体规划,使矿区废弃的矸石山得以综合利用。在保证矿山地质环境安全的前提下,根据矸石废弃地的立地条件及历史文化特征,本着变废为宝、以人为本和科学布局相结合的规划原则,通过道路、景观、建筑、绿地等各方面的布置把项目区规划为一处集矿山生态修复、矿山废弃地改造、教育娱乐等功能为一体的矿山公园。这种"变废为宝"和可持续利用的设计理念缓解了人地矛盾,修复了生态环境,争取了社会经济发展空间,满足了场地功能多样性,具有一定的现实意义。 相似文献
77.
Resource conservation strategies for rice‐wheat cropping systems on partially reclaimed sodic soils of the Indo‐Gangetic region,and their effects on soil carbon 下载免费PDF全文
V.K. Mishra S. Srivastava A.K. Bhardwaj D.K. Sharma Y.P. Singh A.K. Nayak 《Natural resources forum》2015,39(2):110-122
The Indo‐Gangetic plain is characterized by intensive agriculture, largely by resource‐poor small and marginal farmers. Vast swathes of salt‐affected areas in the region provide both challenges and opportunities to bolster food security and sequester carbon after reclamation. Sustainable management of reclaimed soils via resource conservation strategies, such as residue retention, is key to the prosperity of the farmer, as well as increases the efficiency of expensive initiatives to further reclaim sodic land areas, which currently lay barren. After five years of experimentation on resource conservation strategies for rice‐wheat systems on partially reclaimed sodic soils of the Indo‐Gangetic region, we evaluated changes in different soil carbon pools and crop yield. Out of all resource conservation techniques which were tested, rice‐wheat crop residue addition (30% of total production) was most effective in increasing soil organic carbon (SOC). In rice, without crop residue addition (WCR), soils under zero‐tillage with transplanting, summer ploughing with transplanting and direct seeding with brown manuring showed a significant increase in SOC over the control (puddling in rice, conventional tillage in wheat). In these treatments relatively higher levels of carbon were attained in all aggregate fractions compared to the control. Soil aggregate sizes in meso (0.25‐2.0 mm) and macro (2‐8 mm) ranges increased, whereas micro (< 0.25 mm) fractions decreased in soils under zero‐till practices, both with and without crop residue addition. Direct seeding with brown manuring and zero tillage with transplanting also showed an increase of 135% and 95%, respectively, over the control in microbial biomass carbon, without crop residue incorporation. In zero tillage with transplanting treatment, both with and without crop residue showed significant increase in soil carbon sequestration potential. Though the changes in accrued soil carbon did not bring about significant differences in terms of grain yield, overall synthesis in terms of balance between yield and carbon sequestration indicated that summer ploughing with transplanting and zero tillage with transplanting sequestered significantly higher rates of carbon, yet yielded on par with conventional practices. These could be appropriate alternatives to immediately replace conventional tillage and planting practices for rice‐wheat cropping systems in the sodic soils of the Indo‐Gangetic region. 相似文献
78.
Maud C. O. Ferrari Meaghan A. Vavrek Chris K. Elvidge Bryan Fridman Douglas P. Chivers Grant E. Brown 《Behavioral ecology and sociobiology》2008,63(1):113-121
Following disturbance, some aquatic prey species release chemicals that act as a warning cue and increase vigilance in nearby
conspecifics. Such disturbance cues evoke consistent low intensity anti-predator responses. In contrast, alarm cues from injured
conspecifics often evoke stronger intensity responses in prey animals. In this study, we test the sensory complement hypothesis,
which suggests that multiple cues act in an additive or synergistic fashion to provide additional information for risk assessment
by prey. In the first experiment, we showed that juvenile rainbow trout pre-exposed to disturbance cues respond to a given
concentration of damage-released alarm cues with a higher intensity of response than the trout that were pre-exposed to cues
from undisturbed conspecifics. The two cues acted in an additive fashion. In the second experiment, we demonstrated that disturbance
cues alone were not enough to elicit a conditioned response to the odour of a novel predator. We also showed that while disturbance
cues elicit an increase in the response of trout to alarm cues, this increase does not translate into a stronger learned response
to the predator when the predator odour is paired with alarm cues. Future studies should take into account sensory complementation
to avoid underestimating the responses of prey to predators. 相似文献
79.
80.