全文获取类型
收费全文 | 4125篇 |
免费 | 416篇 |
国内免费 | 1441篇 |
专业分类
安全科学 | 440篇 |
废物处理 | 212篇 |
环保管理 | 348篇 |
综合类 | 2728篇 |
基础理论 | 615篇 |
环境理论 | 3篇 |
污染及防治 | 921篇 |
评价与监测 | 246篇 |
社会与环境 | 225篇 |
灾害及防治 | 244篇 |
出版年
2024年 | 13篇 |
2023年 | 86篇 |
2022年 | 258篇 |
2021年 | 263篇 |
2020年 | 227篇 |
2019年 | 171篇 |
2018年 | 173篇 |
2017年 | 192篇 |
2016年 | 205篇 |
2015年 | 253篇 |
2014年 | 305篇 |
2013年 | 361篇 |
2012年 | 347篇 |
2011年 | 410篇 |
2010年 | 313篇 |
2009年 | 283篇 |
2008年 | 295篇 |
2007年 | 265篇 |
2006年 | 250篇 |
2005年 | 174篇 |
2004年 | 143篇 |
2003年 | 132篇 |
2002年 | 116篇 |
2001年 | 99篇 |
2000年 | 103篇 |
1999年 | 84篇 |
1998年 | 78篇 |
1997年 | 84篇 |
1996年 | 70篇 |
1995年 | 54篇 |
1994年 | 36篇 |
1993年 | 41篇 |
1992年 | 26篇 |
1991年 | 17篇 |
1990年 | 10篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 5篇 |
1930年 | 1篇 |
排序方式: 共有5982条查询结果,搜索用时 15 毫秒
371.
在我国提出大力发展乡村旅游的背景下,乡村旅游已成为社会主义新农村建设和城乡统筹发展的主要内容,并成为解决“三农”问题的一条重要途径。由于乡村旅游良好的“城乡联动”机制和广阔发展前景,将成为重庆城市带农村发展的重要举措。但从旅游学的角度看,乡村旅游产品具有一般旅游产品的特征,其发展历史较短而速度过快,已出现了众多棘手的问题。通过对重庆市乡村旅游资源及其发展现状分析,对发展中存在的问题进行了重点分析,从规划编制、精品培育、设施完善、资源保护、市场拓展、人才培养、示范带动等方面对乡村旅游发展对策进行了探讨。 相似文献
372.
In recent years, increasing attention has been paid to the trace-level contamination of pharmaceuticals in the water environment all over the world. Considering a large number of pharmaceuticals used, it is crucial to establish a priority list of pharmaceuticals that should be monitored and/or treated first. In the present study, we developed a ranking system based on the pharmaceutical consumption, removal performance in the wastewater treatment plants (WWTPs) and potential ecological effects, and applied to the situation of China. 39 pharmaceuticals, which had available consumption data and also been reported previously in the WWTPs of China, were selected as candidate pharmaceuticals. Among them, seventeen pharmaceuticals were considered as priority pharmaceuticals, out of which, erythromycin, diclofenac acid and ibuprofen, had the high priority. Compared with other literatures, we found that some pharmaceuticals given concerns to globally should also be included in the priority list in China; while some pharmaceuticals, not mentioned in other literatures, such as cefalexin, ketoconazole, should be also given prior consideration in China. Among all the therapeutic classes, antibiotics, which were grossly abused in China, contributed the most to the priority pharmaceuticals. However, priority antibiotics accounted for only 32% of candidate antibiotics, while 71% and 100% of the candidate anti-inflammatory and antilipidemic respectively were identified as the priority pharmaceuticals, indicating that antibiotics might be overanxiously considered in the previous studies on their behaviors in the WWTPs of China. 相似文献
373.
Tao Tang Kun QianTianyu Shi Fang WangPingliang Li Jianqiang LiYongsong Cao 《Chemosphere》2012,89(11):1419-1425
Quinestrol is synthetic estrogen used in contraceptive and hormone replacement therapy and occasionally for treating breast cancer and prostate cancer. It can make its way into the environment through sewage discharge and waste disposal produced by human excretions. In this study, the photodegradation kinetics of quinestrol in various conditions was investigated by UV and solar irradiation. The affecting factors were studied including concentration of hydrogen peroxide, different water types, and the initial concentrations of quinestrol. Concurrently, the transformation products and presumed pathways of quinestrol in distilled water by UV irradiation were identified and proposed. The results showed that the degradation of quinestrol in both irradiation conditions followed the pseudo-first-order kinetics. More rapid degradation was observed by UV irradiation (k = 0.018 min−1) than solar irradiation (k = 0.004 h−1), and the photodegradation rate of quinestrol depended on the concentration of hydrogen peroxide, the initial concentration of quinestrol and water types. The transformation products of quinestrol in distilled water were identified by gas chromatography/mass spectrometry. When exposed to UV irradiation, quinestrol in aqueous solution was rapidly degraded, giving at least ten photodegradation products. The chemical structures of ten degradation products were identified on the basis of mass spectrum interpretation and literature data. 相似文献
374.
Liu YH Xie R Guo YR Zhu GN Tang FB 《Journal of environmental science and health. Part. B》2012,47(5):475-483
The effectiveness of homologous and heterologous formats in a nanocolloidal gold-based immunoassay for pesticide residue determination was investigated. Parathion, one of the most toxic organophosphorus pesticides, was used as the target analyte. One-step homologous and heterologous test strips based on a nanocolloidal gold-labeled monoclonal antibody were developed for the rapid detection of parathion residues. The results showed that the heterologous format was more effective than the homologous format, being more sensitive, more specific to parathion and more tolerant of matrix interferences. The best competitive hapten was found to have a moderate heterology and the opposite electronic distribution to the immunizing hapten. The detection limits for parathion using the preferred heterologous strip were 1 μg/L in water samples and 5 μg/kg in soil and food samples. 相似文献
375.
Fang H Tang FF Zhou W Cao ZY Wang DD Liu KL Wu XW Yu YL 《Journal of environmental science and health. Part. B》2012,47(2):104-110
The effects of repeated applications of the fungicide triadimefon in agricultural soil on the microbial functional diversity of the soil and on the persistence of the fungicide in the soil were investigated under laboratory conditions. The degradation half-lives of triadimefon at the recommended dosage, simulated by a first-order kinetic model, were 23.90, 22.95, and 21.52 days for the first, second, and third applications, respectively. Throughout this study, no significant inhibition of the Shannon-Wiener index (H') was observed. However, the Simpson index (1/D) and the McIntosh index (U) were obviously reduced (p ≤ 0.05) during the initial 3 days after the first triadimefon application and thereafter, gradually recovered to or exceeded the level of the control soil. A similar trend in variation but with a faster recovery in the 1/D and U was observed after the second and third triadimefon applications, respectively. Taken together, the above results indicate that the repeated application of triadimefon enhanced the degradation rate of the fungicide and the recovery rate of the soil microbial functional diversity. It is concluded that repeated triadimefon applications in soil have a transient or temporary inhibitory effect on soil microbial communities. 相似文献
376.
Li Y Tang J Yu X Xu X Cheng H Wang S 《Environmental science and pollution research international》2012,19(6):2329-2343
Introduction
Trends in precipitation pH and conductivity during 1992?C2009, and in ionic compositions from January 2007 to June 2009, are reported from Lushan Mountain, one of the highest mountains in mid-east China. Annual mean pH was in the range of 4.35?C5.01 and showed a statistically very significant (P?0.01) decreasing trend with time. Annual mean conductivity showed a statistically significant (P?0.05) increasing trend, although this was not the case for non-H conductivity. Increasing rainwater acidity was mainly caused by increasing amounts of acid substances entering the rain. The trends in precipitation pH and conductivity were directly associated with energy consumption.Results and discussions
Over the period of study, Lushan Mountain received more rainfall in spring and summer. The pH values varied seasonally with winter minima. The winter multiyear seasonal mean pH was 4.35. The corresponding summer value was 4.88. SO 4 2? and NO 3 ? were the main anions, and NH 4 + and Ca2+ the main cations. The anion to cation ratio was 0.8?C1.0, and that of [SO 4 2? ] to [NO 3 ? ] was 2.4-3.0, much lower than that of the 1980s. However, sulfuric acid was still the main acid present. The ratio of [NH 4 + ] to [Ca2+] was about 1.0, suggesting that these two alkaline substances provided close acid neutralizing capacity. The ratio of [Cl?] to [Na+] was about 0.67, somewhat lower than that of natural precipitation.Conclusions
Ionic composition varied seasonally and was closely correlated to the amounts of rainfall and pollution. Trajectory analyses showed that the trajectories to Lushan Mountain could be classified in six clusters and trajectories originating from the South Sea and the areas surrounding Lushan Mountain had the greatest impacts on precipitation chemistry. 相似文献377.
Liang B Yao Q Cheng H Gao S Kong F Cui D Guo Y Ren N Wang A 《Environmental science and pollution research international》2012,19(5):1385-1391
Purpose
With the aim of enhanced degradation of azo dye alizarin yellow R (AY) and further removal of the low-strength recalcitrant matter (LsRM) of the secondary effluent as much as possible, our research focused on the combination of aerobic bio-contact oxidation (ABO) with iron/carbon microelectrolysis (ICME) process.Materials and methods
The combined ABO (with effective volume of 2.4?l) and ICME (with effectively volume of 0.4?l) process were studied with relatively short hydraulic retention time (HRT) of 4 or 6?h.Results
At the HRT of 6?h with the reflux ratio of 1 and 2, the AY degradation efficiency in the final effluent was >96.5%, and the total organic carbon (TOC) removal efficiency were 69.86% and 79.44%, respectively. At the HRT of 4?h and the reflux ratio of 2, TOC removal efficiency and AY degradation efficiency were 73.94% and 94.89%, respectively. The ICME process obviously enhanced the total AY removal and the generated micromolecule acids and aldehydes then that wastewater backflow to the ABO where they were further biodegraded.Conclusion
The present research might provide the potential options for the advanced treatment azo dyes wastewater with short HRT and acceptable running costs. 相似文献378.
城市污水处理厂污水处理系统中四环素类药物耐药菌的分布特性研究 总被引:4,自引:0,他引:4
采用微生物平板涂布法对2家城市污水处理厂污水处理各阶段的四环素类药物(四环素、金霉素、土霉素)耐药菌分布进行了测定,分析了污水处理的各阶段对四环素类药物耐药菌的去除效果。结果显示,2家污水处理厂污水处理系统中均能检出土霉素、四环素、金霉素耐药菌,数量分布均为土霉素耐药菌>四环素耐药菌>金霉素耐药菌。3种耐药菌的浓度均在加氯消毒出水中为最小(在0~103 cfu/mL),在外排污泥中最大(高于进水浓度,在105~107 cfu/mL)。四环素耐药菌数从进水的1.1×105~1.6×105 cfu/mL降为出水的0~5.5×102 cfu/mL,说明污水处理过程对四环素耐药菌有一定的去除效果,但四环素耐药菌占总菌数的百分比没有明显下降或上升,相比于进水的1.1%~3.4%,出水仍然保持在3.1%~4.3%左右,表明污水处理过程中没有选择性的富集或去除四环素耐药菌。 相似文献
379.
VFAs、TOC及COD作为生物除磷能力指标的探讨 总被引:3,自引:0,他引:3
在实际生活污水的处理中,研究了通过A/O运行模式对生物除磷过程中磷的变化情况及在厌氧释磷过程中COD、TOC与VFAs变化之间的关系。结果表明,在厌氧释磷过程中VFAs的变化更能准确地反映系统内释磷进程,实际生活污水中能直接用于磷释放的有机物含量占COD的13.33%,并且释放1 mg P所需VFAs为1.401 mg,此值明显低于前期研究结果。通过对COD、TOC和VFAs 3种组分的分析,可将实际生活污水中的有机底物分为3类:易生物降解含碳有机物、难降解的含碳有机物和水中存在的无机性还原物质,含量分别占COD的13.33%、31.7%和54.97%,其中只有13.33%的含量对生物释磷有直接作用,并可对实际生活污水除磷有指导意义。 相似文献
380.