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351.
腐殖酸在氯离子体系中的电解氧化特性 总被引:1,自引:0,他引:1
通过小型实验对腐殖酸模拟废水进行了电解氧化处理,考察了阳极材料、氯离子初始浓度对腐殖酸电解氧化处理效果的影响,探讨了腐殖酸在电解处理过程中分子量分布的变化及电解产生的低分子量产物组成.研究结果表明,PbO2阳极的电解处理效果比 Ru-Ir/Ti阳极的处理效果好,当废水在氯离子体系中电解时.可缩小2种阳极对CODCr去除效果的差距;电解后溶液中溶解性有机物的分子量分布向小分子量方向转变;当溶液中有氯离子存在时,电解过程产生的 ClO-的间接氧化作用可有效地将大分子有机物降解为小分子有机物.腐殖酸在氯离子体系中电解生成的低分子量化合物主要有 CO2、氯仿、乙酸、苯酚、苯乙醇、2H-1,4 氯苯基双氮杂卓-2-1,1-(1,1-二甲基乙基)-萘酚、3-(3-羧基-4-羟基-5-硝基酚)-D-丙氨酸等. 相似文献
352.
The adsorption and desorption characteristics of Al3+ to/from humic acids at di erent pH, ionic strength, and temperature were
studied by the C-25 glucosan-gel chromatography method. The results showed that the maximum adsorption amount (Qmax) and
adsorption constant (k) increased, whereas, the absolute value of standard thermodynamic molar free energy change ( G0
m) decreased
with the increase of pH at constant ionic strength and temperature. With ionic strength increasing from 0 to 0.15 mol/L, Qmax and k
increased and the absolute value of G0
m decreased at constant pH and temperature. High temperature was unfavorable for the adsorption
reaction, as indicated by the dramatic decrease of Qmax and the absolute value of G0
m with an increase in temperature. The standard
thermodynamic molar free energy change ( G0
m) and the standard thermodynamic enthalpy change ( H0m
) of the adsorption reaction
were both negative, suggesting that adsorption reaction was spontaneous and exothermic. The desorption rate of HA-Al3+ complex
accelerated with the decrease of pH, and a significant linear relationship could be obtained between pH and the desorption rates of Al3+
from humic acids. These results demonstrated that the Al3+ adsorption reaction was a “biphase” reaction, and adsorption occurred at
both the interior and exterior adsorption sites of humic acids. 相似文献
353.
Humic substances are ubiquitous redox-active organic compounds of environment.In this study,experiments were conducted to determine the reduction capacity of humic acid in the matrix of bromate and Fe(Ⅲ) solutions and the role of Fe(Ⅲ) in this redox process.The results showed that the humic acid regenerated Fe(Ⅱ) and reduced bromate abiotically.The addition of Fe(Ⅲ) could accelerate the bromate reduction rate by forming humic acid-Fe(Ⅲ) complexes.Iron species acts as electron mediator and catalyst for the bromate reduction by humic acid,in which humic acid transfers electrons to the complexed Fe(Ⅲ) to form Fe(Ⅱ),and the regenerated Fe(Ⅱ) donate the electrons to bromate.The kinetics study on bromate reduction further indicated that bromate reduction by humic acid-Fe(Ⅲ) complexes is pH dependent.The rate decreased by 2-fold with the increase in solution pH by one unit.The reduction capacity of Aldrich humic acid was observed to be lower than that of humic acid or natural organic matter of Suwanne River,indicating that such redox process is expected to occur in the environment. 相似文献
354.
Chunyan YU Xie QUAN Xiaoxia OU Shuo CHEN 《Frontiers of Environmental Science & Engineering in China》2008,2(3):291-296
Four fractions (A, B, C, and D) of humic acids (HAs) were separated based on the polarity from weak to strong. UV-vis absorption
and Fourier transform infrared spectroscopy (FTIR) analysis show that the fractions C and Dpossessedmore aromatic C=C content.
The influences of HAs and their fractions on the photolysis were investigated by the photodegradation of 2,4-D solutions under
simulated solar light irradiation. The degradation rate of 2,4-D was found to decrease in the presence of bulk HAs or their
fractions especially at high HAs concentration. The fractions of strong polarity C and D retarded the degradation rate more
than the fractions of weak polarity A and B. This could be attributed to the different absorption intensity of the four HAs
fractions in the order of D ⩾ C > A > B, and the stronger π-π electron donor-acceptor interactions between the strong polar
fractions and 2,4-D. 相似文献
355.
胺基官能基化的HMS吸附水体中的腐殖酸 总被引:1,自引:0,他引:1
研究了胺基表面官能化前后的HMS(hexagonal mesoporous silica)对腐殖酸的吸附, Freundlich方程拟合结果表明,表面官能化后吸附常数K值由0.56提高至105,反映出表面官能化能显著改善HMS对腐殖酸的吸附,且低pH值条件下吸附效果更佳.表征结果显示,腐殖酸分子主要吸附在表面胺化HMS的中孔孔道内,并首先占据吸附剂中较大的中孔孔道.吸附动力学结果显示腐殖酸在表面胺化的HMS上吸附符合二级动力学,吸附速率主要受孔道内扩散控制. 相似文献
356.
VUV/TiO_2/O_3去除水中微量硝基苯的研究 总被引:1,自引:0,他引:1
采用负载在钛片上的二氧化钛(TiO2)薄膜光催化剂,以能发射185 nm真空紫外线(VUV)的紫外灯为光源,研究臭氧强化的真空紫外光催化方法(VUV/TiO2/O3)对水中微量硝基苯的去除效果.结果表明,VUV/TiO2/O3是一种有效地去除水中微量硝基苯的方法,VUV/TiO2/O3的表观一级反应速率常数比UV/TiO2/O3和VUV/O3分别高102.8%和30.8%,去离子水中50 μg/L的硝基苯反应60 s后就降低到检测限以下.VUV/TiO2/O3对硝基苯的降解速率随臭氧投加量的增加而显著增大,臭氧投加量1.52 mg/L时的反应速率比不加臭氧时提高了134.4%;虽然表观一级反应速率常数随初始浓度增加而稍有下降,但初始浓度170 μg/L的硝基苯反应2 min后也无法检出.水中常见的重碳酸盐和腐殖酸对硝基苯降解有显著的抑制作用,两者浓度分别为2 mmol/L和3.2 mg/L时,VUV/TiO2/O3对硝基苯的表观反应速率常数分别下降82.9%和71.6%,反应速率常数的倒数与重碳酸氢根浓度线性相关.VUV/TiO2/O3能快速有效地去除地表水(含碳酸盐和天然有机物)中的微量硝基苯,4 min内初始浓度为90 μg/L的硝基苯去除率达到96%,UV254降低了80%. 相似文献
357.
腐殖酸缓效肥料的NO_3~--N田间淋溶及土壤残留 总被引:3,自引:0,他引:3
为探讨腐殖酸缓效肥料对地下水及土壤质量的潜在影响,分别在砂质(SS)和黏质土壤(CS)中,利用自制田间淋溶设备研究了不同肥料处理的NO3--N淋溶及土壤残留特性.结果表明,在2种不同质地土壤中,不同时间施肥处理淋溶液中的NO3--N浓度比不施氮肥处理高28.1%~222.2%,但腐殖酸缓效肥料可在一定程度上抑制NO3--N的向下淋溶,且在CS土壤中的抑制作用更有持续性.CS土壤淋溶液中NO3--N的浓度比SS土壤降低41.2%~59.1%,抑制NO3--N向下淋失的作用更强.施肥可造成NO3--N在土壤剖面中的累积,腐殖酸缓效肥料处理0~40cm土壤剖面中NO3--N所占比例显著高于尿素及复合肥处理,分别达59.8%和54.4%.SS土壤中NO3--N的总量显著低于CS土壤,HA缓施肥、尿素及复合肥处理分别降低81.7%、81.1%和47.6%.同常规施肥处理相比,腐殖酸缓效肥料处理可不同程度的提高土壤有机质、碱解氮、速效磷及阳离子交换量的含量,且在黏质土壤中水溶性盐总量比尿素及复合肥处理分别降低24.8%和22.5%.因此,施用腐殖酸缓效肥料可有效改善土壤理化性状、降低施肥对地下水等造成的潜在污染风险. 相似文献
358.
359.
Haloacetic acids, disinfection byproducts (DBPs) formed during drinking water chlorination process are carcinogens. The e cacy
of nanofiltration (NF) was examined for the removal of five regulated haloacetic acids (HAA5): chloro-, dichloro-, and trichloro-acetic
acid (CAA, DCAA, and TCAA); bromo-, and dibromo-acetic acid (BAA, and DBAA) in synthetic water. NF with the dense negatively
charged membrane (ES 10), is the most e cient in removing HAA5 than the loose negatively charged membrane (NTR 7410) and
neutral surface membrane (NTR 729HF), due to the greater electrostatic repulsion (Donan exclusion) and sieve e ect. Excellent HAA5
removal e ciency of 90%–100% could be obtained even at a low pressure of 1 105 Pa with ES 10. Changes in cross-flow velocity did
not e ect the performance of membranes with a small pore size such as ES 10 and NTR 729HF. The increase in HAA5 concentration
exhibited the adverse e ect on the performance of three membranes by strengthening the concentration polarization, which was the
driving force for the di usion of HAA anions across the membrane. 相似文献
360.