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371.
采用理论计算和实测相结合的方法估计了江苏数字地震台网的地震监测能力。虽然用两种方法得到的监测区略有差异 ,但几何形状相近 ,其公共区域部分更趋合理地反映了目前江苏数字地震台网的监测范围。比较了速度型和位移型地震记录的差异 ,并讨论了其监测范围差异的原因 相似文献
372.
This study focuses on the effects of pH and fluoride at different molar ratios of fluoride to Al (RF:Al) on the removal of cadmium (Cd2+) and phosphate by Al coagulation. Fluoride at RF:Al ≥ 3:1 inhibits the removal of Cd over wide Al dose ranges from 5 to 10 mg/L as Al. The removal of phosphate decreases significantly at high RF:Al of 10:1 whereas at lowered RF:Al (i.e., ≤ 6:1), an adverse effect is observed only at insufficient Al doses below 2 mg/L. Fluoride shows inhibitive effects towards the removal of Cd at pH 7 and 8 and that of phosphate at pH 6. Fluoride decreases the ζ-potential in both systems, and the decreasing extent is positively correlated to the elevated RF:Al. The Al fluoride interactions include the formation of Al–F complexes and the adsorption of fluoride onto Al(OH)3 precipitates, i.e., the formation of Al(OH)nFm. Al–F complex formation inhibits Al hydrolysis and increases residual Al levels, and a more significant increase was observed at lower pH. Al–F complexes at high RF:Al complicate the coagulation behavior of Al towards both negative and positive ionic species. Moreover, fluoride at low RF:Al shows little effect on Al coagulation behavior towards Cd2 + and phosphate, and the spent defluoridation adsorbent, i.e., aluminum (Al) hydro(oxide) with adsorbed fluoride at RF:Al of below 0.1:1, may be reclaimed as a coagulant after being dissolved. 相似文献
373.
374.
真菌产黄青霉(Pcnioillium Chrysogonum)对致癌物质苯并(a)芘[B(a)P]的氧化 总被引:8,自引:1,他引:8
本试验证明,典型的土壤真菌202号和细菌91号能氧化B(a)P。细菌氧化B(a)P的产物除顺式二氢二醇无标准品未鉴定外,其余的产物与真菌的相同。 真菌产黄青霉氧化B(a)P为反式9,10-二氢二醇-B(a)P,反式-7,8-二氢二醇-B(a)p,1,6-醌-B(a)P,6,12-醌-B(a)P,3,6-醌-B(a)P,9-OH-B(a)P,3-OH-B(a)P。 用标记~(14)CB(a)P试验,真菌产黄青霉氧化B(a)P的动力学研究指出,在96小时内能氧化B(a)P2.8%,氧化产物包含水溶性的和酯溶性的。 氧化后的B(a)P产物的最大吸收光谱与B(a)P的不同,不能用常规检定B(a)P的方法检出,但其部分产物仍具致癌作用。为了弄清B(a)P在土壤中的转化,必须进一步研究B(a)P在土壤中与其它物质的结合和钝化。 相似文献
375.
银川市东郊设施蔬菜基地土壤中邻苯二甲酸酯污染特征及健康风险评价 总被引:5,自引:0,他引:5
在宁夏银川市东郊设施蔬菜基地共采集49个表层土样,采用气相色谱质谱联用检测方法,分析了土壤中16种邻苯二甲酸酯(Phthalate esters,PAEs)化合物含量,并对其污染分布、污染特征进行了评价,同时对美国EPA和欧盟优先控制的6种PAEs进行了人体暴露的健康风险评价.结果表明,银川市东郊设施蔬菜基地土壤中16种邻苯二甲酸酯化合物(∑16PAEs)的含量范围为2.123~17.271 mg·kg~(-1),平均值和中位数分别为5.120和4.324 mg·kg~(-1).土样中DMP、DEP、Dn BP、DIBP和DEHP的检出率为100%.其中,DMP、Dn BP和DEHP是研究区土壤中PAEs污染物的主要组成部分,DMP、Dn BP和DEHP分别占∑16PAEs总量的46.03%、26.55%和10.32%,三者之和占∑16PAEs的82.79%,占美国EPA 6种优先控制污染物水平的86.16%.对人体健康风险评价表明,研究区6种优先控制化合物对人体产生的非致癌风险均1,未超过EPA推荐的非致癌水平,表明非致癌风险在可接受范围之内.对于DEHP单体,居民通过饮食途径的致癌风险为(0.779±1.370)×10-5,超过EPA推荐的致癌水平,应引起一定的重视,而BBP和DEHP其它非饮食途径的致癌风险都在可接受范围,不会对人体健康产生危害. 相似文献
376.
Chengzhi Xing Cheng Liu Qihou Hu Qingyan Fu Shanshan Wang Hua Lin Yizhi Zhu Shuntian Wang Weiwei Wang Zeeshan Jave Xiangguang Ji Jianguo Liu 《环境科学学报(英文版)》2021,33(7):44-55
Ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) observations were operated from 02 to 21 December 2018 in Leshan, southwest China, to measure HONO, NO2 and aerosol extinction vertical distributions, and these were the first MAX-DOAS measurement results in Sichuan Basin. During the measurement period, characteristic ranges for surface concentration were found to be 0.26–4.58 km?1 and averaged at 0.93 km?1 for aerosol extinction, 0.49 to 35.2 ppb and averaged at 4.57 ppb for NO2 and 0.03 to 7.38 ppb and averaged at 1.05 ppb for HONO. Moreover, vertical profiles of aerosol, NO2 and HONO were retrieved from MAX-DOAS measurements using the Heidelberg Profile (HEIPRO) algorithm. By analysing the vertical gradients of pollutants and meteorological information, we found that aerosol and HONO are strongly localised, while NO2 is mainly transmitted from the north direction (city center direction). Nitrogen oxides such as HONO and NO2 are important for the production of hydroxyl radical (OH) and oxidative capacity in the troposphere. In this study, the averaged value of OH production rate from HONO is about 0.63 ppb/hr and maximum value of ratio between OH production from HONO and from (HONO+O3) is > 93% before12:00 in Leshan. In addition, combustion emission contributes to 26% for the source of HONO in Leshan, and we found that more NO2 being converted to HONO under the conditions with high aerosol extinction coefficient and high relative humidity is also a dominant factor for the secondary produce of HONO. 相似文献
377.
Photochemical reactions can alter the transformation of sedimentary organic matter into dissolved organic matter (DOM) and affect its ultimate fate in water ecosystems. In the present study, the photorelease of DOM and Fe from resuspended lake sediments was investigated under different O2 and NO3? concentration conditions to study the mechanisms of DOM and Fe photorelease. The amount of photoreleased Fe, which ranged from 0.22 to 0.70 μmol/L, was significantly linearly correlated with the amount of photoreleased DOM. O2 and NO3? could promote the photochemical release of DOM and Fe, especially during the initial 4 h irradiation. In general, the order of the photorelease rates of DOM and Fe under different conditions was as follows: NO3?/aerobic > aerobic ≈ NO3?/anaerobic > anaerobic. The photorelease rates of DOM and Fe were higher for the initial 4 hr irradiation than these for the subsequent 8 hr irradiation. The photorelease of DOM and Fe is thought to proceed via direct photodissolution and indirect processes. The relative contributions of indirect processes (>60%) was much greater than that of direct photodissolution (<40%). The photoproduced H2O2 under aerobic and anaerobic conditions indicated that hydroxyl radicals (?OH) are involved in the photorelease of DOM. Using ?OH scavengers, it was found that 38.7%, 53.7%, and 77.6% of photoreleased DOM was attributed to ?OH under anaerobic, aerobic, and NO3?/aerobic conditions, respectively. Our findings provide insights for understanding the mechanisms and the important role of ?OH in the DOM and Fe photorelease from resuspended sediments. 相似文献
378.
379.
船用燃油超标识别方法的建立和技术发展是进行船舶排放控制区(Domestic Emission Control Areas,DECA)政策执行的重要保障.本研究建立了基于船舶自动识别系统(Automatic Identification System,AIS)数据的船舶排放实时计算模型和岸基环境观测相结合的技术方法,选取上海吴淞口航道水域开展实地外场观测实验,实现了对观测船只排放烟羽中SO2和NO2浓度的在线观测和对燃油硫含量(Fuel Sulfur Content,FSC)进行同步识别和反算.观测期间,通过差分吸收光谱(Differential Optical Absorption Spectroscopy,DOAS)技术共捕捉到1505艘次船舶的烟羽.经过观测截面的船舶总吨位为30~14308 t,船舶排放烟羽浓度峰值的平均持续时间为3~10 min.受船舶烟羽影响期间,SO2和NO2的浓度增量分别在0.03~35.51 ppb和0.02~39.26 ppb之间,实时排放模型估算出SO2和NO2的排放强度分别为1.32~28.06 g·min-1和2.89~123.80 g·min-1.结合在线观测和实时排放模型基于硫氮比对船用燃油硫含量进行反算识别,并与实测燃油硫含量数据样本进行对比验证,结果表明,实际燃油硫含量在0.05%以上时,反算硫含量数值误差在10%以内.本研究可为船舶燃油超标识别提供新的技术思路,并为船舶排放控制区政策落实提供科学基础. 相似文献
380.
通过紫外分光光度法,研究了Cd2+和Pb2+对四环素超声降解过程的影响。研究结果表明,Cd2+和Pb2+在水中与四环素发生络合反应后,在紫外光谱上发生蓝移,在206 nm处产生新的峰值。同时,在低摩尔比(四环素∶重金属1)时,Cd2+和Pb2+可以加快四环素的超声降解。0.01 mmol/L四环素溶液24 h的超声降解率为7.54%,加入Pb2+和Cd2+离子后,四环素去除率分别升高至20.82%和18.75%。在高摩尔比(四环素∶重金属2)时,Cd2+和Pb2+抑制了四环素的降解,在0.08 mmol/L四环素溶液中,加入Pb2+和Cd2+离子反而使四环素去除率从4.69%分别降低至2.04%和1.40%。 相似文献