全文获取类型
收费全文 | 25663篇 |
免费 | 5105篇 |
国内免费 | 29600篇 |
专业分类
安全科学 | 2378篇 |
废物处理 | 1294篇 |
环保管理 | 2148篇 |
综合类 | 37152篇 |
基础理论 | 4419篇 |
环境理论 | 1篇 |
污染及防治 | 9199篇 |
评价与监测 | 2027篇 |
社会与环境 | 787篇 |
灾害及防治 | 963篇 |
出版年
2024年 | 39篇 |
2023年 | 332篇 |
2022年 | 909篇 |
2021年 | 870篇 |
2020年 | 1253篇 |
2019年 | 2348篇 |
2018年 | 2615篇 |
2017年 | 2740篇 |
2016年 | 2617篇 |
2015年 | 3144篇 |
2014年 | 3770篇 |
2013年 | 4234篇 |
2012年 | 3929篇 |
2011年 | 3570篇 |
2010年 | 3181篇 |
2009年 | 3203篇 |
2008年 | 2974篇 |
2007年 | 2746篇 |
2006年 | 2371篇 |
2005年 | 1675篇 |
2004年 | 1389篇 |
2003年 | 1184篇 |
2002年 | 1037篇 |
2001年 | 941篇 |
2000年 | 1128篇 |
1999年 | 964篇 |
1998年 | 734篇 |
1997年 | 720篇 |
1996年 | 690篇 |
1995年 | 600篇 |
1994年 | 409篇 |
1993年 | 328篇 |
1992年 | 376篇 |
1991年 | 309篇 |
1990年 | 259篇 |
1989年 | 210篇 |
1988年 | 158篇 |
1987年 | 79篇 |
1986年 | 84篇 |
1985年 | 53篇 |
1984年 | 55篇 |
1983年 | 40篇 |
1982年 | 47篇 |
1981年 | 34篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1972年 | 5篇 |
1971年 | 5篇 |
1958年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Potassium Release Kinetics and Water Retention of Controlled-Release Fertilizers Based on Chitosan Hydrogels 总被引:2,自引:0,他引:2
Controlled release fertilizer (CRF) hydrogels were prepared from poly(vinyl alcohol), poly(vinyl alcohol)/chitosan and chitosan
using glutaraldehyde as a crosslinker. Intermolecular interactions of the CRF hydrogels were elucidated using FTIR. Water
absorbency characteristics of the CRF hydrogels were also studied. It was found that the CRF hydrogels exhibited the equilibrium
swelling ratio (SR) in the range 70–300%. The water retention of soil containing the CRF hydrogels was also examined. It was
found that the CRF hydrogels increased the water retention of the soil. After 30 days, soil containing the PVA-, PVA/CS- and
CS-hydrogels showed the water retention capacities of 25%, 10% and 4%, respectively. While the soil without the CRF hydrogel
had already given off most of the water. The release behavior of potassium from the CRF hydrogels, both in deionized water
and in soil, was investigated. In soil, the potassium release mechanism from the PVA- and PVA/CS-hydrogels were non-Fickian
diffusion. On the other hand, the CS hydrogel showed, n value that was close to 1.0 corresponding to case II transport. In deionized water, all the CRF hydrogels showed small values
of release exponent (n < 0.5) indicating a quasi-Fickian diffusion mechanism. 相似文献
992.
湖北省武汉市青山区发改委 《再生资源与循环经济》2010,3(8):14-17
青山区作为全国著名的钢铁基地和老工业区,在推进钢铁、石化、环保等优势产业发展的同时,突破环境、资源限制"瓶颈",以理念创新、体制创新、机制创新和科技创新为动力,坚持规划引领,加强政府引导,突出企业主体,强化项目支撑,鼓励全民参与,全方位启动循环经济试点工作,推动了地区发展方式的转变和区域产业结构优化,为探索我国重化工聚集区走新型工业化道路提供借鉴。 相似文献
993.
Wang Y Li Y Kim H Walker SL Abriola LM Pennell KD 《Journal of environmental quality》2010,39(6):1925-1933
Commercial production and use of fullerene (C60) nanomaterials will inevitably lead to their release into the environment, where knowledge of C60 fate and transport is limited. In this study, a series of one-dimensional column experiments was conducted to assess the transport and retention of nanoscale fullerene aggregates (nC60) in water-saturated soils. Under the experimental conditions, complete retention of nC60 was observed in columns (2.5 cm inside diameter x 11 cm length) packed with Appling or Webster soil, which contain 0.75 and 3.33% organic carbon by weight, respectively. When the volume of aqueous nC60 suspension (approximately 4.5 mg L(-1)) applied to Appling soil was increased from 5 to 65 pore volumes, the travel distance increased from 3 to 8 cm, and the retention capacity approached a limiting value of 130 microg g(-1), although nC60 was not detected in the column effluent. The addition of 20 mg C L(-1) Suwannee River humic acid to the influent suspension increased the nC60 transport in Appling soil but did not resul in breakthrough. Attempts to simulate the experimental data using clean-bed filtration theory were not satisfactory, yielding retention profiles that failed to match observed data. Subsequent incorporation of a limiting retention capacity expression into the mathematical model resulted in accurate predictions of the measured nC60 retention profiles and transport behavior. The sizable retention capacities observed in this study suggest that transport of nC60 is limited in relatively fine-textured soils containing appreciable amounts of clay minerals and organic matter, with substantial accumulation of nC60 aggregates near the point of release. 相似文献
994.
995.
996.
Laboratory batch and column experiments were conducted to investigate the immobilization of phosphorus (P) in soils using synthetic magnetite nanoparticles stabilized with sodium carboxymethyl cellulose (CMC-NP). Although CMC-stabilized magnetite particles were at the nanoscale, phosphorus removal by the nanoparticles was less than that of microparticles (MP) without the stabilizer due to the reduced P reactivity caused by the coating. The P reactivity of CMC-NP was effectively recovered when cellulase was added to degrade the coating. For subsurface non-point P pollution control for a water pond, it is possible to inject CMC-NP to form an enclosed protection wall in the surrounding soils. Non-stabilized “nanomagnetite” could not pass through the soil column under gravity because it quickly agglomerated into microparticles. The immobilized P was 30% in the control soil column, 33% when treated by non-stabilized MP, 45% when treated by CMC-NP, and 73% when treated by both CMC-NP and cellulase. 相似文献
997.
Ruiqiang Yang An Li Chuanyong Jing Pu Wang Guibin Jiang 《Environmental pollution (Barking, Essex : 1987)》2010,158(6):2310-2316
High mountains may play significant roles in the global transport of persistent organic pollutants (POPs). This work aims to investigate the levels, patterns and distribution of semi-volatile organoclorine pollutants and to improve the understanding of the long-range atmospheric transport and fate of contaminants on the Tibetan Plateau. A total of 60 fish samples were collected from eight lakes located between 2813 and 4718 m above sea level across the Plateau. Concentrations of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) including dichlorodiphenyltrichloroethane and its metabolites (DDTs), hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) were measured in fish muscle. The results showed that concentrations of DDT, HCH and HCB were comparable to or lower than those found in remote mountains of Europe, Canada and US, while PCB concentrations in fish were, on average, about 4-150 times lower on Tibet than at other mountain areas. The transport and fate of contaminants in the Plateau are significantly influenced by the unique climatological and meteorological conditions, particularly by the summer Indian monsoon and winter westerly jet stream. 相似文献
998.
999.
K. Hund-Rinke K. Schlich A. Wenzel 《Umweltwissenschaften und Schadstoff-Forschung》2010,22(5):517-528
Abstract
Purpose Little is known about the ecotoxicity of nanomaterials and there are no specific guidelines for sample preparation and testing.
We set out to establish whether the method used to prepare TiO2 dispersions had a significant impact on aquatic ecotoxicity. We also followed the formation of agglomerates during the incubation
period. 相似文献
1000.
维生素和酮苷生产废水中难降解污染物的溯源研究 总被引:2,自引:1,他引:1
研究了维生素和酮苷生产过程中各生产工段排水的生物降解特性,评价了各生产工段对生产废水中难降解有机物的贡献率,追溯了可能的难降解特征污染物。结果表明,维生素生产废水中的难降解物质主要来自W1-1、W1-3、W1-5和W1-6生产工段,甲醛、丁烯酮、醛酮聚合物和吡啶可能是导致生产废水难降解的重要原因;酮苷生产废水中的难降解物质主要来自W2-1、W2-3和W2-7生产工段,氯代有机溶剂和苯环类物质可能是导致生产废水难降解的重要原因。建议根据具体生产工段排水的水质特征,有针对性地进行物化处理,提高废水可生化性。 相似文献