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471.
Keke Xiao Zecong Yu Kangyue Pei Mei Sun Yuwei Zhu Sha Liang Huijie Hou Bingchuan Liu Jingping Hu Jiakuan Yang 《Frontiers of Environmental Science & Engineering》2022,16(2):23
472.
Junlang Qiu Caley Craven Nicholas Wawryk Kristin Carroll Xing-Fang Li 《环境科学学报(英文版)》2022,34(7):190-196
Amino acids (AAs) are prevalent in source water, particularly during spring run-off. Monitoring of amino acids in source water is desirable for water treatment plants (WTP) to indicate changes in source water quality. The objective of this study was to establish analytical procedures for reliable monitoring of amino acids in source water. Therefore, we examined two different methods, large volume inject (LVI) and solid phase extraction (SPE), for sample preparation prior to HILIC-MS/MS. The LVI-HILIC-MS/MS method can provide fast and sensitive detection for clean samples, but suffers from matrix effects, resulting in irreproducible separation and shortening column lifetime. We have demonstrated that SPE was necessary prior to HILIC-MS/MS to achieve reproducible and reliable quantification of AAs in source water. A natural heterocyclic amine 1-methyl-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid (MTCCA) was also included in the method to indicate changes in other natural nitrogenous compounds in source water. The SPE-HILIC-MS/MS method was able to achieve limits of detection from 2.6-3400 ng/L for the amino acids and MTCCA with RSDs (n=3) of 1.1%-4.8%. As well, retention times (RT) of the analytes were reproducible with variation less than 0.01 min (n=3) through the entire project. We further applied the SPE-HILIC-MS/MS method to determine AAs in authentic source water samples collected from two drinking water treatment plants (WTPs) during the 2021 spring run-off season. The results support that the SPE-HILIC-MS/MS method does not require derivatization and can provide reliable, accurate, and robust analysis of AAs and MTCCA in source water, supporting future monitoring of source water quality. 相似文献
473.
474.
必需脂肪酸及其代谢转化产物的营养生理功能研究进展 总被引:1,自引:0,他引:1
为了开发富含n-3多不饱和脂肪酸(n-3PUFA)这一功能性食品,需要我们更深入地认识n-3和n-6脂肪酸.必需脂肪酸α-亚麻酸和亚油酸分别是n-3和n-6多不饱和脂肪酸的母体,两者及其碳链延长产物是不能相互转化的.n-3和n-6脂肪酸的作用也不能相互替代.作为功能性食品成分的n-3和n-6脂肪酸具有预防心血管疾病、治疗高血脂症、轻度老年痴呆症、降低胆固醇血症的危险等作用.本文主要综述n-3和n-6脂肪酸的特殊作用、n-6和n-3脂肪酸之间的相互关系以及在开发富含n-3PUFA动物产品及食品方面的研究进展,并提出了今后尚待解决的问题. 相似文献
475.
Schobert R 《Die Naturwissenschaften》2007,94(1):1-11
Natural products containing tetronic acid or tetramic acid moieties continue to attract the interest of chemists, biologists,
and physicians due to their challenging structures and to the wide range of biological activities they display. This review
portrays the structural varieties of tetronic and tetramic acids and the spectrum of possible therapeutically relevant effects
in man for exemplary derivatives. Their biosynthetic origin from α-amino and α-hydroxy acids is briefly discussed as is the
relationship between their structures and their modes of interaction with biochemical effectors such as metal cations or enzymes.
A short overview of laboratory syntheses of the heterocyclic core structures of tetramic and tetronic acids is provided with
an emphasis on those emulating the biosynthesis. A synthesis from the α-amino or α-hydroxy esters and the cumulated phosphorus
ylide Ph3PCCO based upon a domino addition–intra-Wittig alkenation sequence is presented with applications to the preparation of the
antibiotics reutericyclin and tenuazonic acid, the cytotoxic melophlin B, and the enzyme inhibitor RK-682. Procedural advantages
of immobilizing either starting component by attaching it to a resin and its exploitation in the parallel synthesis of libraries
of potential drug candidates are described. The basic domino reaction can even be extended by further C–C bond forming steps
when starting from suitable α-hydroxy or α-amino allyl esters. Depending on the chosen reaction conditions, bioactive intermediates
of formally three to seven step long cascades can be obtained. Among them, herbicidal 3-alkyltetronic acids and lactone endoperoxides
with antiplasmodial activity exceeding that of the natural antimalarial lead artemisinin. Hence, this domino reaction gives
access to diversely functionalized derivatives of tetronic and tetramic acids. As it can also be ported to solid phase, it
is ideally suited for parallel and combinatorial processing. Future developments might include running such domino sequences
in continuous mode in arrays of “labs on microchips”. 相似文献
476.
高分子重金属絮凝剂处理含镍废水性能研究 总被引:2,自引:0,他引:2
为提高重金属废水处理的效率及简化处理流程,以聚乙烯亚胺、NaOH、CS2为原料,合成了一种既能捕集重金属离子又能除浊的新型高分子重金属絮凝剂PEX.通过絮凝实验研究了PEX在不同pH值下捕集Ni2 的性能,考察了废水中含有的不同有机配位剂柠檬酸铵、氨基乙酸、EDTA、腐殖酸等对PEX去除Ni2 的影响,并讨论了浊度和Ni2 对PEX絮凝效果的相互影响.实验结果表明:该絮凝剂对Ni2 有很好的捕集功能,Ni2 的最高去除率可达99%以上;pH值对Ni2 的去除率有一定的影响,但只要PEX投加量足够,pH值对Ni2 的最高去除率影响不大;水中存在有柠檬酸铵或氨基乙酸时,在一定程度上会抑制Ni2 的去除,但增加PEX投加量会减小此影响;当有EDTA存在时,会明显促进Ni2 的去除;当有腐殖酸存在时,在较低pH值下会抑制Ni2 的去除,但当pH值升高时其对Ni2 的去除有促进作用;Ni2 和致浊物质共存时,会相互促进彼此的去除,浊度的去除率在99%以上.PEX具有双重功效,对重金属离子和浊度的去除率高,具有一定的推广应用前景. 相似文献
477.
以胃蛋白酶(蛋白质)、谷胱甘肽(氨基酸多肽)、葡萄糖(糖类)作为模型物质代表藻来源有机物,并以Fluka腐殖酸为对照,研究其耗氯量、三卤甲烷(主要是氯仿)、卤乙酸(主要是二氯乙酸(DCAA)、三氯乙酸(TCAA))的形成情况.结果显示4种模型物质在氯化后,其余氯在前2 h迅速降低,6 h后则下降速度渐缓;其中耗氯量最大的是谷胱甘肽(96 h:7.1 mg·mg-1(以每毫克碳计,下同)),其次是胃蛋白酶(96 h:4.2 mg·mg-1)、腐殖酸(96 h:3.0 mg·mg-1),而葡萄糖最小(96 h:0.7 mg·mg-1).4种模型物质氯仿、DCAA、TCAA的生成速度也是在起初的2 h较快,随后渐缓;但从单位碳的产量来看,腐殖酸和胃蛋白酶形成氯仿(96h: 15.1~55.2 μg·mg-1(以每毫克碳计,下同))、DCAA(96 h: 15.1~55.2 μg·mg-1)、TCAA(96h: 15.1~55.2 μg·mg-1)均较多,而谷胱甘肽、葡萄糖则相对较少(氯仿-96 h:2.5~5.1 μg·mg-1;DCAA-96 h:0.6~8.0 μg·mg-1;TCAA-96 h:0.12~3.8 μg·mg-1);而从前驱物特性来说,氯仿、TCAA的前驱物具有较高的芳香度(即高的SUV254值),而DCAA前驱物的SUV254相对较低.对于富含蛋白质、多肽、糖类等的富营养化饮用水源,则要格外注意饮用水中DCAA所带来的健康风险. 相似文献
478.
基于PCA-LSSVM的厌氧废水处理系统出水VFA在线预测模型 总被引:2,自引:1,他引:1
采用IC厌氧废水处理系统处理人工合成废水,并利用PCA-LSSVM模型对系统出水挥发性脂肪酸(VFA)进行预测.首先利用主成分分析法(PCA)分析影响厌氧废水出水VFA浓度的多个变量的相关性并降低输入变量维数,然后用网格搜索结合10倍交叉验证优化LSSVM模型参数sig2和gam,最后利用建立的模型对实验数据进行仿真预测.仿真结果表明,稳态LSSVM模型对稳态条件下厌氧废水处理系统出水VFA具有很好的仿真预测能力,相对误差在4.72%以内,平均相对百分比误差(MAPE)为1.61%,均方根误差(RMSE)为1.08,相关系数达0.9996;稳态干扰LSSVM模型对厌氧废水处理系统出水VFA的仿真预测精度有所降低但仍然具有较好的预测能力,平均相对百分比误差(MAPE)为15.83%,均方根误差(RMSE)为15.45,相关系数为0.9984,该方法可为厌氧出水VFA在线预测和厌氧废水处理系统的优化控制提供指导. 相似文献
479.
Joaquim C.G. Esteves da Silva Adélio A.S.C. Machado Marta S.S.D.S. Pinto 《Journal of environmental science and health. Part. B》2013,48(4):469-482
Abstract The fulvic acid (fua) fractions of two samples of composted solid wastes [urban (urfua) and livestock (lsfua) wastes], commercialized to be used in agriculture as organic correctives or fertilizers, were analyzed for their affinity towards Cu(II) at pH=6. Molecular fluorescence spectroscopy (synchronous mode) was used to monitor the quenching caused by the complexation upon addition of Cu(II) to fua. Spectral data were preprocessed by a chemometric self‐modeling mixture analysis method (SIMPLISMA) to detect the number of different types of fluorescent binding sites that exist in each fua, their spectra and the corresponding quenching profiles [fluorescence intensity as function of the total Cu(II) concentration]. From the analysis of the quenching profiles, the amount of binding sites (Cl) and the corresponding conditional stability constants (K') were calculated. Both fua samples have approximately Cl = 0.21 mmol/g and the logarithms of K’ are 4.21(3) and 4.51(8), respectively for urfua and lsfua. The differences detected between these fua samples and those extracted from natural soils can be attributed mainly to the relatively small humification extent of the present anthropogenic fua samples. 相似文献
480.
Andrew B. Sparks Eric T. Wang Craig A. Struble Wade Barrett Renee Stokowski Celeste McBride Jacob Zahn Kevin Lee Naiping Shen Jigna Doshi Michel Sun Jill Garrison Jay Sandler Desiree Hollemon Patrick Pattee Aoy Tomita-Mitchell Michael Mitchell John Stuelpnagel Ken Song Arnold Oliphant 《黑龙江环境通报》2012,32(1):3-9