全文获取类型
收费全文 | 656篇 |
免费 | 91篇 |
国内免费 | 283篇 |
专业分类
安全科学 | 51篇 |
废物处理 | 174篇 |
环保管理 | 47篇 |
综合类 | 478篇 |
基础理论 | 120篇 |
污染及防治 | 128篇 |
评价与监测 | 29篇 |
社会与环境 | 2篇 |
灾害及防治 | 1篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 4篇 |
2021年 | 18篇 |
2020年 | 15篇 |
2019年 | 24篇 |
2018年 | 19篇 |
2017年 | 15篇 |
2016年 | 31篇 |
2015年 | 51篇 |
2014年 | 41篇 |
2013年 | 75篇 |
2012年 | 70篇 |
2011年 | 68篇 |
2010年 | 43篇 |
2009年 | 39篇 |
2008年 | 36篇 |
2007年 | 53篇 |
2006年 | 54篇 |
2005年 | 50篇 |
2004年 | 51篇 |
2003年 | 34篇 |
2002年 | 30篇 |
2001年 | 26篇 |
2000年 | 38篇 |
1999年 | 23篇 |
1998年 | 26篇 |
1997年 | 19篇 |
1996年 | 16篇 |
1995年 | 15篇 |
1994年 | 17篇 |
1993年 | 8篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有1030条查询结果,搜索用时 15 毫秒
21.
22.
针对对氯氰苄生产废水中氰化物浓度较高,提出了次氯酸钠氧化法治理工艺.实践表明,经该工艺处理,废水中COD、氰化物等污染物指标能达到GB8978-1996<污水综合排放标准>一级排放标准要求,除氰效果明显,具有显著的环境和经济效益. 相似文献
23.
沉淀—树脂吸附法处理对氨基偶氮苯盐酸盐生产废水的研究 总被引:3,自引:0,他引:3
对氨基偶氮苯盐酸盐(PABS)是生产染料的重要中间体。在PABS生产过程中,排放出高浓度(COD4万~8万mg/L)、高色度(4万~8万)、高毒性(含苯胺和对氨基偶氮苯)和高氯(Cl-4万~10万mg/L)的废水。利用中和沉淀—大孔吸附树脂吸附法进行了处理工艺的小试研究。结果表明,废水色度去除率达到999%,降到20以下;出水中基本不含对氨基偶氮苯(PAB);出水中苯胺的浓度降到3mg/L。GC/MS分析的结果表明,乙醇脱附液中苯胺是最主要的有机物,所以利用该工艺能实现苯胺的回收。 相似文献
24.
Research on biodegradable materials has been stimulated due to concern regarding the persistence of plastic wastes. Blending starch with poly(lactic acid) (PLA) is one of the most promising efforts because starch is an abundant and cheap biopolymer and PLA is biodegradable with good mechanical properties. Poly(vinyl alcohol) (PVOH) contains unhydrolytic residual groups of poly(vinyl acetate) and also has good compatibility with starch. It was added to a starch and PLA blend (50:50, w/w) to enhance compatibility and improve mechanical properties. PVOH (MW 6,000) at 10%, 20%, 30%, 40%, 50% (by weight) based on the total weight of starch and PLA, and 30% PVOH at various molecular weights (MW 6,000, 25,000, 78,000, and 125,000 dalton) were added to starch/PLA blends. PVOH interacted with starch. At proportions greater than 30%, PVOH form a continuous phase with starch. Tensile strength of the starch/PLA blends increased as PVOH concentration increased up to 40% and decreased as PVOH molecular weight increased. The increasing molecular weight of PVOH slightly affected water absorption, but increasing PVOH concentration to 40% or 50% increased water absorption. Effects of moisture content on the starch/PLA/PVOH blend also were explored. The blend containing gelatinized starch had higher tensile strength. However, gelatinized starch also resulted in increased water absorption. 相似文献
25.
Jon E. Schoonover Karl W. J. Williard 《Journal of the American Water Resources Association》2003,39(2):347-354
ABSTRACT: Ground water contamination by excess nitrate leaching in row‐crop fields is an important issue in intensive agricultural areas of the United States and abroad. Giant cane and forest riparian buffer zones were monitored to determine each cover type's ability to reduce ground water nitrate concentrations. Ground water was sampled at varying distances from the field edge to determine an effective width for maximum nitrate attenuation. Ground water samples were analyzed for nitrate concentrations as well as chloride concentrations, which were used as a conservative ion to assess dilution or concentration effects within the riparian zone. Significant nitrate reductions occurred in both the cane and the forest riparian buffer zones within the first 3.3 m, a relatively narrow width. In this first 3.3 m, the cane and forest buffer reduced ground water nitrate levels by 90 percent and 61 percent, respectively. Approximately 40 percent of the observed 99 percent nitrate reduction over the 10 m cane buffer could be attributed to dilution by upwelling ground water. Neither ground water dilution nor concentration was observed in the forest buffer. The ground water nitrate attenuation capabilities of the cane and forest riparian zones were not statistically different. During the spring, both plant assimilation and denitrification were probably important nitrate loss mechanisms, while in the summer nitrate was more likely lost via denitrification since the water table dropped below the rooting zone. 相似文献
26.
Fed-batch cultures of recombinantEscherichia coli strains were carried out for the production of poly(3-hydroxybutyric acid) (PHB) in a chemically defined medium. TheE. coli strains used were XL1-Blue, harboring pSYL105, a stable high-copy number plasmid containing theAlcaligenes eutrophus polyhydroxyalkanoate (PHA) genes, and XL1-Blue, harboring pSYL107, which is pSYL105 containing theE. coli ftsZ gene to suppress filamentation. With XL1-Blue(pSYL105) the final cell mass and PHB concentration obtained in 62 h were 102 and 22.5 g/L, respectively. Fed-batch culture of XL1-Blue(pSYL107) under identical conditions resulted in a final cell mass and PHB concentration of 127.5 and 48.2 g/L, respectively. The PHB contents obtained with XL1-Blue(pSYL105) and XL1-Blue(pSYL107) were 22.1 and 37.8%, respectively. Therefore, PHB was more efficiently produced in a defined medium by employing filamentation-suppressed recombinantE. coli. 相似文献
27.
Thermal and mechanical properties of poly(lactic Acid) and poly(ethylene/butylene Succinate) blends 总被引:2,自引:0,他引:2
In this study, blends of poly (lactic acid) (PLA) with poly(ethylene/butylene succinate) (Bionolle) have been investigated
for their thermal and mechanical properties as a function of the concentration of Bionolle. Differential scanning calorimetry
(DSC), dynamic mechanical analysis (DMA), and tensile tests were used to characterize the blends. From the results of the
DMA and DSC, it was found that this blend system was not miscible within the compositions studied. DSC results showed that
adding Bionolle aids in crystallization of PLA. It was observed that increasing the Bionolle concentration led to a slight
increase in the strain-at-break of the blends but a decrease in the Young’s modulus and ultimate tensile strength. Biaxially
oriented films showed an increase in tensile strength, modulus, and strain-at-break. 相似文献
28.
火灾是一种灾害性燃烧现象 ,给人员和财产安全带来极大损失。氯化氢 (HCl)是火灾烟气中阻碍人员逃生的最重要的刺激性气体之一。以典型的小尺度和大尺度实验为例 ,分析了加热程度和通风供氧对常用有机材料起火后释放HCl的影响 ,发现不论小尺度还是大尺度 ,HCl的形成只与燃烧过程有关 ,与氧化过程无关 ,HCl的生成率不随通风情况不同而改变。实验中影响HCl释放的主要因素是热 (辐射加热热流密度或温度 )。当超过CCl键发生断裂的温度后 ,继续升温HCl释放速率不发生改变 ,出现稳定释放阶段。在反映HCl释放过程不同尺度间存在共性 ,因此 ,利用小尺度的结果进行释放规律内在机理的探索是合理的方法 相似文献
29.
Nugraha E. Suyatma Alain Copinet Lan Tighzert Veronique Coma 《Journal of Polymers and the Environment》2004,12(1):1-6
Biodegradable film blends of chitosan with poly(lactic acid) (PLA) were prepared by solution mixing and film casting. The main goal of these blends is to improve the water vapor barrier of chitosan by blending it with a hydrophobic biodegradable polymer from renewable resources. Mechanical properties of obtained films were assessed by tensile test. Thermal properties, water barrier properties, and water sensitivity were studied by differential scanning calorimeter analysis, water vapor permeability measurements, and surface-angle contact tests, respectively. The incorporation of PLA to chitosan improved the water barrier properties and decreased the water sensitivity of chitosan film. However, the tensile strength and elastic modulus of chitosan decreased with the addition of PLA. Mechanical and thermal properties revealed that chitosan and PLA blends are incompatible, consistent with the results of Fourier transform infrared (FTIR) analysis that showed the absence of specific interaction between chitosan and PLA. 相似文献
30.
Gregory M. Glenn Artur K. Klamczynski Bor-Sen Chiou Delilah Wood William J. Orts Syed H. Imam 《Journal of Polymers and the Environment》2004,12(3):189-196
Starch aquagel-based lightweight concrete has properties similar to those of other lightweight concrete products. However, starch aquagels are unstable in the strongly alkaline conditions typical of Portland Cement-based concrete and may interfere with the setting process. The effect of alkali treatments on the physical, mechanical, and functional properties of starch aquagels and aquagels from starch/polymer blends was investigated. Starch was blended at 100–115°C in a twin-screw extruder with five different polymers to determine whether the blends improved alkaline resistance. Polymer blends containing 5%, 15%, and 30% of the polymer hydrated and formed aquagels when equilibrated in water for 24 h. However, equilibrium moisture content was lower for the blends compared to the starch control. Aquagels equilibrated in 0.15 N NaOH swelled, lost compressive strength and had greater than 90% moisture. The blend of starch and 30% PVOH absorbed less moisture and was more resistant to alkaline dissolution in 1 N NaOH than the other blends tested making it a more suitable material for aquagel-based concrete. The moisture content of starch-based aquagels and mixing time were critical factors in determining setting times. The size of aquagel blends had a minor effect on density and compressive strength. 相似文献