收费全文 | 14440篇 |
免费 | 593篇 |
国内免费 | 5194篇 |
安全科学 | 961篇 |
废物处理 | 894篇 |
环保管理 | 1105篇 |
综合类 | 8076篇 |
基础理论 | 2345篇 |
环境理论 | 6篇 |
污染及防治 | 5088篇 |
评价与监测 | 565篇 |
社会与环境 | 521篇 |
灾害及防治 | 666篇 |
2024年 | 6篇 |
2023年 | 235篇 |
2022年 | 700篇 |
2021年 | 561篇 |
2020年 | 432篇 |
2019年 | 423篇 |
2018年 | 547篇 |
2017年 | 649篇 |
2016年 | 633篇 |
2015年 | 822篇 |
2014年 | 1111篇 |
2013年 | 1471篇 |
2012年 | 1190篇 |
2011年 | 1366篇 |
2010年 | 1008篇 |
2009年 | 992篇 |
2008年 | 1017篇 |
2007年 | 822篇 |
2006年 | 782篇 |
2005年 | 544篇 |
2004年 | 409篇 |
2003年 | 517篇 |
2002年 | 450篇 |
2001年 | 367篇 |
2000年 | 410篇 |
1999年 | 465篇 |
1998年 | 381篇 |
1997年 | 357篇 |
1996年 | 345篇 |
1995年 | 298篇 |
1994年 | 215篇 |
1993年 | 190篇 |
1992年 | 126篇 |
1991年 | 102篇 |
1990年 | 72篇 |
1989年 | 61篇 |
1988年 | 46篇 |
1987年 | 22篇 |
1986年 | 25篇 |
1985年 | 13篇 |
1984年 | 13篇 |
1983年 | 12篇 |
1982年 | 11篇 |
1981年 | 3篇 |
1977年 | 1篇 |
1972年 | 2篇 |
1918年 | 1篇 |
1917年 | 1篇 |
1916年 | 1篇 |
Animal manure is an important source of antibiotics and antibiotic resistance genes (ARGs) in the environment. However, the difference of antibiotic residues and ARG profiles in layer and broiler manure as well as their compost remains unexplored. In this study, we investigated the profiles of twelve antibiotics, seventeen ARGs, and class 1 integrase gene (intI1) in layer and broiler manure, and the corresponding compost at large-scale. Compared with layer manure, broiler manure exhibited approximately six times more residual tetracyclines, especially chlortetracycline. The relative abundances of qnrS and ermA genes in broiler manure were significantly higher than those in layer manure. The concentration of tetracyclines not only had a significantly positive correlation with tetracycline resistance genes (tetA and tetC) but was also positively correlated with quinolone resistance (qepA, qnrB, and qnrS) and macrolide resistance (ermA and ermT). Most ARGs in manure were reduced after composting. However, the relative abundance of sulfonamide resistance gene sul1 increased up to 2.41% after composting, which was significantly higher than that of broiler (0.41%) and layer (0.62%) manure. The associated bacterial community was characterized by high-throughput 16S rRNA gene sequencing. The relative abundances of thermophilic bacteria had significant positive correlations with the abundance of sul1 in compost. The composting has a significant impact on the ARG-associated gut microbes in poultry manure. Variation partitioning analysis indicated that the change of bacterial community compositions and antibiotics contributed partially to the shift in ARG profiles. The results indicate that at industry-scale production broiler manure had more antibiotics and ARGs than layer manure did, and composting decreased most ARG abundances in poultry manure except for sulfonamide resistance genes.
相似文献Polycyclic aromatic hydrocarbon (PAH) exposure and genetic susceptibility were conductive to genotoxic effects including gene damage, which can increase mutational probability. We aimed to explore the dose-effect associations of PAH exposure with damage of exons of epidermal growth factor receptor (EGFR) and breast cancer susceptibility gene 1 (BRCA1), as well as their associations whether modified by Flap endonuclease 1 (FEN1) genotype. Two hundred eighty-eight coke oven male workers were recruited, and we detected the concentration of 1-hydroxypyrene (1-OH-pyr) as PAH exposure biomarker in urine and examined base modification in exons of EGFR and BRCA1 respectively, and genotyped FEN1 rs174538 polymorphism in plasma. We found that the damage indexes of exon 19 and 21 of EGFR (EGFR-19 and EGFR-21) were both significantly associated with increased urinary 1-OH-pyr (both Ptrend < 0.001). The levels of urinary 1-OH-pyr were both significantly associated with increased EGFR-19 and EGFR-21 in both smokers and nonsmokers (both P < 0.001). Additionally, we observed that the urinary 1-OH-pyr concentrations were linearly associated with both EGFR-19 and EGFR-21 only in rs174538 GA+AA genotype carriers (both P < 0.001). Moreover, FEN1rs rs174538 showed modifying effects on the associations of urinary 1-OH-pyr with EGFR-19 and EGFR-21 (both Pinteraction < 0.05). Our findings revealed the linear dose-effect association between exon damage of EGFR and PAH exposure and highlight differences in genetic contributions to exon damage and have the potential to identify at-risk subpopulations who are susceptible to adverse health effects induced by PAH exposure.
相似文献Size, morphology, and composition of airborne particles strongly affect human health and visibility, precipitation, and the kinetic characteristics of particles. In this study, the morphology and chemical composition of particles emitted from conventional (diesel and gasoline) and alternative (CNG and methanol) fuel vehicles were characterized through scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX). The SEM images revealed that the size of primary particles (without agglomeration) was approximately 10 nm in the exhaust from all the tested vehicles. The particles emitted from gasoline vehicle (GV), CNG vehicle (CNGV), and methanol vehicle (MV) had the same median diameter, 62 nm, which was smaller than those from heavy diesel vehicle (HDV) and light diesel vehicle (LDV). Soot was observed in the HDV, LDV, and GV samples but not in the CNGV and MV. The fractal dimension, which was used to quantify the degree of irregularity of soot, was 1.752 ± 0.014, 1.789 ± 0.076, and 1.769 ± 0.006 in the exhaust from HDV, LDV, and GV samples, respectively. The particles discharged by all tested vehicles contained the elements C, O, Fe, and Na. The main element in the samples of HDV, LDV, and GV was C, while O was the main element in the samples of alternative fuel vehicles. The profiles of minor elements were more complex in the emissions of alternative fuel vehicles than those in the emissions of conventional fuel vehicles. The results improved our understanding of the morphology and elemental composition of particles emitted from vehicles powered by diesel, gasoline, CNG, and methanol.
相似文献