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251.
Ultrasensitive determination of carbendazim in water and orange juice using a carbon paste electrode
Gilberto J. Arruda Fábio De Lima Claudia A. L. Cardoso 《Journal of environmental science and health. Part. B》2016,51(8):534-539
A carbon paste electrode was used for the electrochemical quantification of carbendazim in water and orange juice samples. Carbendazim oxidation on the electrode surface was found to be controlled by adsorption. The novel electrochemical procedure for carbendazim quantification employed differential pulse voltammetry using a carbon paste electrode under optimal conditions. Carbendazim oxidation currents were linear at concentrations of 2.84 to 45.44 µg L?1, with a limit of detection of 0.96 µg L?1. The proposed method was applied to carbendazim quantification in ultrapurified water, river water, and orange juice. Recovery rates in water and orange juice samples were in the 97%–101% range, indicating that the method can be employed to determine carbendazim in these matrices, with advantages including shorter analysis time and lower cost than routine methods such as chromatography or spectroscopy. The electrode showed good reproducibility, remarkable stability, and especially good surface renewability by simple mechanical polishing. The recovery rates observed were highly concordant with those obtained for high-performance liquid chromatography, having a relative standard deviation of less than 1.3%. 相似文献
252.
A. O. Mehder Mohamed A. Dastageer Yusuf B. Habibullah Mohammed A. Iqbal Luqman E. Oloore 《Journal of environmental science and health. Part. B》2016,51(6):358-365
Laser induced breakdown spectroscopy (LIBS) was applied for the detection of carcinogenic elements like bromine in four representative brands of loaf bread samples and the measured bromine concentrations were 352, 157, 451, and 311 ppm, using Br I (827.2 nm) atomic transition line as the finger print atomic transition. Our LIBS system is equipped with a pulsed laser of wavelength 266 nm with energy 25 mJ pulse?1, 8 ns pulse duration, 20 Hz repetition rate, and a gated ICCD camera. The LIBS system was calibrated with the standards of known concentrations in the sample (bread) matrix and such plot is linear in 20–500 ppm range. The capability of our system in terms of limit of detection and relative accuracy with respect to the standard inductively coupled plasma mass spectrometry (ICPMS) technique was evaluated and these values were 5.09 ppm and 0.01–0.05, respectively, which ensures the applicability of our system for Br trace level detection, and LIBS results are in excellent agreement with that of ICPMS results. 相似文献
253.
Manuel H. Barcelo-Quintal Maria C. Cebada-Ricalde Angel R. Trejo-Irigoyen Reyna B. Rendon-Osorio Jose A. Manzanilla-Cano 《Journal of environmental science and health. Part. B》2013,48(2):120-126
Kinetic studies of endosulfan photochemical degradation in controlled aqueous systems were carried out by ultraviolet light irradiation at λ = 254 nm. The photolysis of (α + β: 2 + 1) endosulfan, α-endosulfan and β-endosulfan were first-order kinetics. The observed rate constants obtained from linear least-squares analysis of the data were 1 × 10?4 s?1; 1 × 10?4 s?1; and 2 × 10?5 s?1, respectively, and the calculated quantum yields (φ) were 1, 1 and 1.6, respectively. Preliminary differential pulse polarographic (DPP) analysis allowed to observe the possible endosulfan photochemical degradation pathway. This degradation route involves the formation of the endosulfan diol, its transformation to endosulfan ether and finally the ether's complete degradation by observing the potential shifts. 相似文献
254.
José A. Manzanilla-Cano Manuel H. Barceló-Quintal Reyna B. Rendón-Osorio Julio Flores-RodrÍguez 《Journal of environmental science and health. Part. B》2013,48(5):515-522
A study was undertaken to determine the transformation kinetic of methylparathion (O, O, -dimethyl O-4 nitrophenylphosphorotioate) in the presence of Fe(III) between pH 2 and 7. The Fe(III) was not electroactive under the conditions used in this study, and polarographic signals were exhibited by methylparathion and main degradation product only. Data suggest that hydrolysis of methylparathion in an acid medium is catalyzed by Fe(III) and the pesticide did not degrade in this medium without this cation. Methylparathion degradation was observed at all the pHs studied and was independent of the predominant chemical form of Fe(III) in the aqueous medium. The reaction was first-order with pH-dependent rate constant (k) values ranging from 3.3 × 10? 3 h? 1 to 7.0 × 10? 3 h? 1. The k values increased as pH decreased, suggesting that Fe(III) acted as an electrophile in the reaction mechanism. 相似文献
255.
分析了化学发光法和差分吸收光谱法(DOAS)测定环境中氮氧化物的原理及相应分析仪器的系统结构,指出了化学发光法氮氧化物分析仪的技术瓶颈及差分吸收光谱法的难点和关键技术。并对两种方法的优缺点及发展趋势进行分析。实验表明,化学发光法与差分吸收光谱法测定的结果具有很好的相关性。 相似文献
256.
应用全差示光度法测定水和废水中的微量氰化物 总被引:2,自引:0,他引:2
在pH80时,CN-与3甲基1苯基5吡唑啉酮、吡啶及氯胺T反应形成稳定的蓝色产物,最大吸收波长为617nm,表观摩尔吸收系数为12×105L/mol·cm。实验了采用全差示光度法测定微量氰化物的条件。通过蒸馏富集,建立了改进的吡唑啉酮法测定氰化物的分析方法,并对实际样品进行了测定。本方法的检出限为0001mgCN-/L,检测范围为0001~025mgCN-/L,可应用于水和废水中微量氰化物的测定。 相似文献
258.
预应力钢筋混凝土梁破坏过程的声发射特性实验研究 总被引:9,自引:0,他引:9
利用全波形声发射技术记录了预应力钢筋混凝土梁在3点弯曲荷载下整个破坏过程的声发射信号,并在研究了声发射累计能量随时间变化关系曲线的基础上,采用谱分析对声发射全波形数据进行了分析和处理。以全波形声发射信号的能量分布特性为依据,通过对时域和频域内信号的振幅、频率特征和构件破坏过程的比较,初步得出了预应力钢筋混凝土梁破坏过程的声发射信号的参数特性,发现全波形声发射信号能够实时反映预应力混凝土梁破坏过程中的特征信息。 相似文献
259.
密度场干涉测量及其条纹处理计算 总被引:2,自引:0,他引:2
本文将普通纹影仪改造成激光差分干涉仪,并用于火焰等密度场的显示与测量。编制了条纹预处理和细化软件系统,并对干涉条纹进行了处理和细化计算。另外,针对细化后的条纹,编制了密度场的计算软件,并对蜡烛火焰和超声速轴对称绕流流场进行了计算,得到了密度场定量的结果。 相似文献
260.