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991.
关于RosinRammler粒径分布函数的研究 总被引:1,自引:0,他引:1
Rosin Ramm ler分布函数是最常用的描述粉尘粒径分布的一种形式 ,本文对表达式中系数 a与指数 n之间的关系进行了分析 ,导出了二者之间的关系式。 相似文献
992.
Tassanee Chetwittayachan Ryosuke Kido Dai Shimazaki Kazuo Yamamoto 《Water, Air, & Soil Pollution: Focus》2002,2(5-6):203-227
Traffic emits particles under 1 m. The particles arethe most responsible to particle-bound polycyclic aromatichydrocarbon (pPAH) which can impact human health. To assessthem as health hazards, we monitored diurnal changes in theconcentration and distribution of pPAH near roads in Tokyo.The total pPAH concentration was determined using aphotoelectric aerosol sensor (PAS) which ionized PAH-adsorbingparticles. The total pPAH concentration was compared withchemical analyses by gas chromatography/mass spectrometry(GC/MS). Two sampling sessions, one in August and one inSeptember 2000, were done at three sampling sites at the Hongo Campus of the University of Tokyo. Monitoring was every two minutes for six consecutive days for the first session and for seven consecutive days for the second session.Correlation of the pPAH concentration with traffic flow andwith meteorological conditions were also assessed. The pPAHconcentration varied in the same manner on all days: it sharplyincreased in the early morning by a sudden burden of traffic, and it rapidly decreased during the daytime, probably owing tophotodegradation and/or dilution by rising in the mixingzone. The local wind field, and consequently thetransportation of pPAH from the road, were stronglyinfluenced by the configuration and location of thesurrounding buildings. The pPAH clearly changed in 1- and0.5 day cycles, particularly at the roadside. 相似文献
993.
Degradation kinetics of aldicarb [2-methyl-2-(methylthio) propionaldehyde O-(methyl carbamoyl) oxime] in surface and subsurface soil containing different levels of sodium dodecylbenzenesulfonate (SDBS) were determined to understand complex effect of SDBS on aldicarb degradation process. The results showed that degradation curves of aldicarb in soil can be described with first order kinetics formula and the degradation rate constant. k (d(-1)), in surface soil was larger than that in subsurface soil. SDBS can accelerate the degradation of aldicarb in soil and there was a good linear relationship between degradation rate constant and the logarithm of SDBS concentration. The possible reasons were that SDBS could change pH value of soil, have solubilization effect on aldicarb, and be used as carbon source of microorganisms. But SDBS had a larger promotion to the degradation of aldicarb in surface than in subsurface soil. When SDBS concentration was 1000 mg/kg of dried soil the first order degradation rate constant of aldicarb could be increased by 56.6 percent in surface soil and by 27.6 percent in subsurface soil, respectively. 相似文献
994.
河台金矿形成机制的实验研究 总被引:1,自引:0,他引:1
本文对河台金矿测定了形成时的物理化学条件,T=200~280℃,P=573.3×10°Pa,fo_2=10~(-37)—10~(-39),成矿溶液具有Na~+>K~+>Ca~(2+),HCO_3~->Cl~_>F~->ΣS,CO_2>CH_4的特点,从早期到晚期,成矿溶液中的Au与Na~+、K~+、F~-、Cl~-等呈同步增长。在高压釜中不同温度压力下以不同浓度的NaHCO_3、HCl为介质对含金建造进行了淋滤试验;模拟了成矿时的温度压力条件,成功地用硫化物还原出溶液中的金,揭示出硫化物、溶液与还原金的定量关系,并阐述了成矿物质、成矿溶液的来源以及金在成矿溶液中的迁移形式和沉淀机制。 相似文献
995.
Xiaosi Su Geng Cui Huang Wang Zhenxue Dai Nam-Chil Woo Wenzhen Yuan 《Environmental geochemistry and health》2018,40(3):1051-1066
As one of the important elements of controlling the redox system within the hyporheic and hypolentic zone, sulfur is involved in a series of complex biogeochemical processes such as carbon cycle, water acidification, formation of iron and manganese minerals, redox processes of trace metal elements and a series of important ecological processes. Previous studies on biogeochemistry of the hyporheic and hypolentic zones mostly concentrated on nutrients of nitrogen and phosphorus, heavy metals and other pollutants. Systematic study of biogeochemical behavior of sulfur and its main controlling factors within the lake hypolentic zone is very urgent and important. In this paper, a typical desert plateau lake, Dakebo Lake in northwestern China, was taken for example within which redox zonation and biogeochemical characteristics of sulfur affected by hydrodynamic conditions were studied based on not only traditional hydrochemical analysis, but also environmental isotope evidence. In the lake hypolentic zone of the study area, due to the different hydrodynamic conditions, vertical profile of sulfur species and environmental parameters differ at the two sites of the lake (western side and center). Reduction of sulfate, deposition and oxidation of sulfide, dissolution and precipitation of sulfur-bearing minerals occurred are responded well to Eh, dissolved oxygen, pH, organic carbon and microorganism according to which the lake hypolentic zone can be divided into reduced zone containing H2S, reduced zone containing no H2S, transition zone and oxidized zone. The results of this study provide valuable insights for understanding sulfur conversion processes and sulfur biogeochemical zonation within a lake hypolentic zone in an extreme plateau arid environment and for protecting the lake–wetland ecosystem in arid and semiarid regions. 相似文献
996.
Guocheng Hu Zhencheng Xu Jiayin Dai Bixian Mai Hong Cao Jianshe Wang Zhimin Shi Muqi Xu 《环境科学学报(英文版)》2010,22(12):1833-1839
Nineteen surface sediment samples collected from Baiyangdian Lake and its inflowing river (Fuhe River) in North China were
analyzed for polybrominated diphenyl ethers (PBDEs) and decabromodiphenylethane (DBDPE). The concentrations of PBDEs and
DBDPE in sediments ranged from 5.5 to 300.7 ng/g dry weight (dw) and 1.1 to 68.2 ng/g dw, respectively. Their levels in sediments in
Fuhe River were significantly higher than those in Baiyandian Lake. Compared to data from other regions, the PBDE levels in surface
sediments from Baiyangdian Lake and Fuhe River were in the medium to lower range. Among the PBDE congeners, BDE209 was
predominant, with contributions to the total PBDEs ranging from 79.4% to 97.3% in sediment samples. For the lowly brominated
congeners (tri- to hepta-BDE), BDE47 and BDE99 were the most abundant, which contributed 52.1% and 44.1% to the sum of
tri- to hepta-BDEs in the sediments from Baiyangdian Lake and Fuhe River, respectively. The compositional patterns of PBDEs in
Baiyangdian Lake sediments indicated that technical deca-BDE mixture was the major pollutant sources with a minor contribution
of penta-BDE mixture. The present study suggested that the importance of Fuhe River as a possibly potential sources of PBDEs
contamination in Baiyangdian Lake. 相似文献
997.
提高中国环境影响评价公众参与制度有效性研究 总被引:1,自引:0,他引:1
在对中国现阶段环境影响评价工作中公众参与所发挥的作用以及现状进行总结的基础上,分析了中国公众参与取得的成绩,同时讨论了现阶段中国公众参与在环境影响评价中存在的普遍问题,主要集中在如何提高公众参与的有效性方面。通过对中国公众参与环境影响评价进行分析,找出了其中存在的问题,如公众参与信息公开不够,公众的意见不被重视等。最后,根据中国环境影响评价中公众参与存在的问题,提出了针对性的对策和建议。 相似文献
998.
999.
Cationic organobismuth complex as an effective catalyst for conversion of CO2 into cyclic carbonates
Xiaowen Zhang Weili Dai Shuangfeng Yin Shenglian Luo Chak-Tong Au 《Frontiers of Environmental Science & Engineering in China》2009,3(1):32-37
In order to achieve high-efficiency conversion of CO2 into valuable chemicals, and to exploit new applications of organobismuth compounds, cationic organobismuth complex with
5,6,7,12-tetrahydrodibenz[c,f][1,5] azabismocine framework was examined for the first time for the coupling of CO2 into cyclic carbonates, using terminal epoxides as substrates and tetrabutylammonium halide as co-catalyst in a solvent-free
environment under mild conditions. It is shown that the catalyst exhibited high activity and selectivity for the coupling
reaction of CO2 with a wide range of terminal epoxide. The selectivity of propylene carbonates could reach 100%, and the maximum turnover
frequency was up to 10740 h−1 at 120°C and 3 MPa CO2 pressure when tetrabutylammonium iodide was used as co-catalyst. Moreover, the catalyst is environment friendly, resistant
to air and water, and can be readily reused and recycled without any loss of activity, demonstrating a potential in industrial
application. 相似文献
1000.
酚类物质作为一类主要的污染物,已引起国内外高度重视,但目前其对陆生生物的毒性研究较少。本试验探究了4-叔丁基苯酚、间甲酚、2-氯苯酚、2-甲酚、2,4-二氯苯酚这5种酚类物质对中国本土物种中国白羽鹌鹑和中华蜜蜂的急性毒性。在中国白羽鹌鹑的急性经口试验中,2-氯苯酚、2-甲酚的7 d的半致死浓度(7 d-LC50)分别为331 mg·kg~(-1)和413 mg·kg~(-1),其他3种酚类物质的7 d-LC50均大于限度值1 000 mg·kg~(-1);在中国白羽鹌鹑的急性饲喂试验中,5种酚类物质的8 d-LC50均大于限度值2 000 mg·kg~(-1);在中华蜜蜂的急性经口试验中,2-氯苯酚、2-甲酚和2,4-二氯苯酚的48 h-LC50分别为306 mg·L~(-1)、358 mg·L~(-1)和364 mg·L~(-1);在中华蜜蜂的急性接触试验中,2,4-二氯苯酚的48 h的半致死量(48 h-LD50)为2.6μg·蜂~(-1),其他4种酚类物质的48h-LD50均大于限度值100μg·蜂~(-1)。研究结果表明不同的酚类物质由于其结构不同亦表现出不同的毒性,甲酚的邻位取代比间位取代对中国白羽鹌鹑和中华蜜蜂的毒性更高,不同物种表现出了相似的规律性。5种酚类物质对我国本土物种中国白羽鹌鹑和中华蜜蜂毒性比对其他水生生物更敏感,存在良好的剂量效应关系。 相似文献