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871.
1 概述稀土(Rare Earth)元素,位于元素周期表第57~71号,由性质十分相近的镧、铈、镨、钕等15种镧系元素以及钪、钇2个元素组成。通常,把57~63号的7个元素称为轻稀土元素,其它10个元素称为重稀土元素。地壳中,稀土元素含量与锌、铜、铅等元素含量不相上下。我国的稀土资源,居世界首位,共约3600万吨(R_2O_3),其中90%分布在包头地区。土壤及生物链中,均有稀土元素。进入环境中的稀土化合物,大部分来自岩石的风化物,其次来自煤的燃烧。稀土元素,主要用于冶金、石油化工、电子器械、玻璃陶瓷等工业上。稀土元素,通过口、呼吸道及皮肤的伤口进入人体。吸收后的稀土元素,从人体内排泄的半衰期为一年至十几年。 相似文献
872.
The waterquality of the downstream of Nanfei River and the northwest area of Lake Chao is evaluated from organic analysis aspect. PAHs such as fluoranthene, pyrene are detected in the waters collected from downstream river and river mouth. More phenolic compounds are found in the river water. Some halogenated hydrocarbons are present in the river and lake waters. A great many of aliphatic hydrocarbons and benzene hydrocarbons found in all the water samples are about one third of the total organics detected. The hydrophobic components are found to be present not only in water but also in suspended sediment. The ratio of the amount existing is 0.4 in sediment and 1 in particle-free water. The quantity of humic materials existing in lake water is larger than that in river water. The proportion of the humic materials in lake water to that in river water is 1.9 to 1. In the lake water, some natural substances, such as dimethyl disulfide, alpha-pinene, azulene, and 6- methyl -2-heptanone are observed. 相似文献
873.
A study for the photochemical behavior of some polyaromatic hydrocarbons (PAH), for example B(a )P, B( k )F and fluoranthene in coal smoke particles was performed by using indoor Teflon smog chamber.Experiments suggest that the photochemical reaction of PAH is first order reaction and kinetic rates of some PAH were obtained. It was shown that the reaction rate constant is proportional to light intensity and water vapor concentration. Temperature and PAH loading also have influence on PAH decay rate. A model for PAH loss has been set up on the basis of the results of our experiments and the simulating results of this model suggest that coal particle PAH half lives are of the order of a period of days in winter and a few hours in summer. Other factors which may have effect on the photochemical reaction of PAH have also been discussed. 相似文献
874.
Ren Shufen Zhang Xuelin Li Wencheng Wang Wensheng Wang Jin Wang Wenjun Zhang Yuxia 《环境科学学报(英文版)》1991,3(4):95-101
The humic acid contents in drinking water and soil in Kaschin-Beck disease areas were found more than that of non-disease areas in this research. Changes of free radical concentration in drinking water were agreed with that of humic acid contents in drinking water of Kaschin-Beck disease areas. A positive correlation of free radical concentration and humic acid content in drinking water has been shown (r=0.913) . The structure of I. R. spectra of humic acid under ultraviolet light has been changed. Thus it indicated that free radical was resulted from benzoqiunonyl groups of humic acid in environment. 相似文献
875.
用醋酸纤维素(CA)为聚合物材料,研制出了截留分子量2000—10000、对PEG截留率为90%以上的小孔径超滤膜.并就铸膜液组成,制膜条件及膜的透过特性等进行了实验. 相似文献
876.
877.
黄梅乱泥滩花岗岩侵入年龄为124.1Ma,完全冷却暴露地表年龄为80Ma,据岩石化学、稀土元素地球化学、~(87)Sr/~(86)Sr初始比值、∈Nd值、δ~(18)0值等综合分析,均显示该岩体具有“S”型花岗岩类的特征,其原始物质来自地壳。岩浆侵位深度为4.8km,结晶温度为798℃,氧逸度fO_2=1×10~(-11)a,压力P=6.57×10~8Pa岩体侵位时处于张性构造环境的陆内碰撞带。 相似文献
878.
本文介绍了一种新研制的磁化率仪,它可测定自然界中大多数物质(良导体除外)的初始磁化率,特别适合于岩石的磁化率及其各向异性(AMS)测量。仪器工作磁场300A/m,频率920Hz,样机总磁化率测量灵敏度达到 2×10~(-12)m~3,读数采用数字显示方式并具有自动锁定功能。与计算机的联机采用了标准EIARS-232C串行接口,因此具有良好的通用性。在软件的控制下,计算机可自动完成测量数据的采集、计算处理、座标转换以及成图或存贮等工作,AMS参数的测量效率得到很大提高。 相似文献
879.
Chunmiao Wang Jianwei Yu Qingyuan Guo Yu Zhao Nan Cao Zhiyong Yu Min Yang 《环境科学学报(英文版)》2019,31(5):100-110
A wide range of compounds with various structural features can cause taste and odor(TO)problems in drinking water. It would be desirable to determine all of these compounds using a simple analytical method. In this paper, a sensitive method combining liquid–liquid extraction(LLE) with gas chromatography-triple quadrupole tandem mass spectrometry(GC–MS/MS)was established to simultaneously analyze 51 odor-causing compounds in drinking water,including organic sulfides, aldehydes, benzenes, phenols, ethers, esters, ketones, nitrogenous heterocyclic compounds, 2-methylisoborneol and geosmin. Three deuterated analogs of target analytes, dimethyl disulfide-d6, benzaldehyde-d6 and o-cresol-3,4,5,6-d4,were used to correct the variations in recovery, and five isotope-labeled internal standards(4-chlorotoluene-d4, 1, 4-dichlorobenzene-d4, naphthalene-d8, acenaphthene-d10, phenanthrene-d10 respectively) were used prior to analysis to correct the variations arising from instrument fluctuations and injection errors. The calibration curves of the target compounds showed good linearity(R2 0.99, level = 7),and method detection limits(MDLs) below 1/10 of the odor threshold concentrations were achieved for most of the odorants(0.10–20.55 ng/L). The average recoveries of most of the analytes in tap water samples were between 70% and 120%, and the method was reproducible(RSD 20%, n = 7). Additionally, concentrations of odor-causing compounds in water samples collected from three drinking water treatment plants(DWTPs) were analyzed by this method.According to the results, dimethyl trisulfide, dimethyl disulfide and indole were considered to be the key odorants responsible for the swampy/septic odor. 2-Methylisoborneol and geosmin were detected as the main odor-causing compounds for musty/earthy odor in DWTP B. 相似文献
880.
Yanguo Teng Dan Feng Liuting Song Jinsheng Wang Jian Li 《Environmental monitoring and assessment》2013,185(11):9559-9569
In order to investigate the distribution of the total petroleum hydrocarbons (TPH) in groundwater and soil, a total of 71 groundwater samples (26 unconfined groundwater samples, 37 confined groundwater samples, and 8 deeper confined groundwater samples) and 80 soil samples were collected in the Songyuan oilfield, Northeast China, and the vertical variation and spatial variability of TPH in groundwater and soil were assessed. For the groundwater from the unconfined aquifer, petroleum hydrocarbons were not detected in three samples, and for the other 23 samples, concentrations were in the range 0.01–1.74 mg/l. In the groundwater from the confined aquifer, petroleum hydrocarbons were not detected in two samples, and in the other 35 samples, the concentrations were 0.04–0.82 mg/l. The TPH concentration in unconfined aquifer may be influenced by polluted surface water and polluted soil; for confined aquifer, the injection wells leakage and left open hole wells may be mainly responsible for the pollution. For soils, the concentrations of TPH varied with sampling depth and were 0–15 cm (average concentration, 0.63 mg/g), >40–55 cm (average concentration, 0.36 mg/g), >100–115 cm (average concentration, 0.29 mg/g), and >500–515 cm (average concentration, 0.26 mg/g). The results showed that oil spillage and losses were possibly the main sources of TPH in soil. The consequences concluded here suggested that counter measures such as remediation and long-term monitoring should be commenced in the near future, and effective measures should be taken to assure that the oilfields area would not be a threat to human health. 相似文献