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131.
S.?R.?Sudhamani A.?Eugene?Raj Baldev?RajEmail author M.?S.?Prasad 《Journal of Polymers and the Environment》2005,13(3):253-260
Moisture sorption characteristics of microbial polysaccharide (Ps.C101) from Pseudomonas caryophilli and polyvinyl alcohol (PVA) blends have been carried out at 27°C for water activity from 0.1 to 0.9. The sorption data was used to fit six different sorption isotherm models proposed in literature. The model constants were determined by linear fitting of the sorption equations. The ranges of applicability of water activity for isotherm models reported in this paper lie in between 0.1 and 0.4 for Brunaur–Emmet–Teller (BET) model (monolayer), and in between 0.2 and 0.9 for other models. The value of the coefficient of determination (R2 = 0.97 ± 0.02) confirms the applicability of the equations studied. 相似文献
132.
D. Briassoulis 《Journal of Polymers and the Environment》2004,12(2):65-81
The mechanical behavior of various types of biodegradable materials depends, mainly, on their chemical composition and the application conditions. Various additives are added into the bioblends to improve their properties, which sometimes even reach the levels of the conventional plastics. It is well known that the environmental conditions during production, storage, and usage of these materials influence their mechanical properties. Ageing during the useful lifetime also causes great losses in the elongation. In the present paper, the overall mechanical behavior of biodegradable films, which may be considered suitable for agricultural applications, but also of partially biodegradable films, is reviewed and analyzed. Selected critical mechanical properties of films before their exposure to biodegradation are investigated and compared against those of conventional agricultural films. 相似文献
133.
Biodegradable Soy-Based Plastics: Opportunities and Challenges 总被引:3,自引:0,他引:3
S. N. Swain S. M. Biswal P. K. Nanda Padma L. Nayak 《Journal of Polymers and the Environment》2004,12(1):35-42
Today's plastics are designed with little consideration for their ultimate disposability or the effect of the resources (feedstocks) used in making them. This has resulted in mounting worldwide concerns over the environmental consequences of such materials when they enter the mainstream after their intended uses. This led to the concept of designing and engineering new biodegradable materials–materials that have the performance characteristics of today's materials but that undergo biodegradation along with other organic waste to soil humic materials. Hence, the production of biodegradable materials from annually renewable agricultural feedstocks has attracted attention in recent years. Agricultural materials such as starches and proteins are biodegradable and environmentally friendly. Soybean is a good candidate for manufacturing a large number of chemicals, including biodegradable plastics, as it is abundantly available and cheap. Soy protein concentrate, isolate, or flakes could be compounded with synthetic biodegradable plastics such as polycaprolactone or poly (lactic acid) to make molded products or edible films or shopping bags and make the environment cleaner and greener. 相似文献
134.
溶胶-凝胶工艺制备掺铅TiO_2纳米薄膜及其光催化性能的研究 总被引:19,自引:0,他引:19
通过sol-gel工艺在玻璃表面制得了均匀透明的掺铅和未掺铅TiO2纳米薄膜;在宏观上,膜层表面光滑平整;在微观上,TiO2薄膜由TiO2球形颗粒组成,其颗粒大小在50~150nm范围内。掺铅TiO2镀膜玻璃在紫外光附近的透光率明显小于未掺铅TiO2镀膜玻璃的透光率,这说明掺铅TiO2镀膜玻璃对紫外光具有明显的吸收。敌敌畏水溶液的光摧化降解实验表明,掺铅TiO2镀膜玻璃对有机磷农药的光解率明显高于未掺铅TiO2镀膜玻璃的光解率。这为进一步提高TiO2的光催化效率开辟了新的途径。 相似文献
135.
136.
光电催化降解2,4-二氯苯酚的研究 总被引:3,自引:0,他引:3
采用Sol-Gel法制备了纳米TiO2/导电玻璃薄膜电极,应用XRD表征了TiO2薄膜的物相和粒度,以上述电极为工作电极和光催化剂,研究了2,4-二氯苯酚溶液的光催化和光电催化降解行为,结果表明,外加阳极偏压为0.7V,时间100min时,光电催化降解率为85%,高出光催化降解25%,2,4-DCP初始浓度(C0)与反应速率(r0)的关系符合Langmuir-Hinshelwood方程,当C0≤0.50mmol.L^-1时,光电催化降解速率可用一级动力学模式来描述。 相似文献
137.
P. Tittonell B. Vanlauwe P.A. Leffelaar E.C. Rowe K.E. Giller 《Agriculture, ecosystems & environment》2005,110(3-4):149-165
The processes of nutrient depletion and soil degradation that limit productivity of smallholder African farms are spatially heterogeneous. Causes of variability in soil fertility management at different scales of analysis are both biophysical and socio-economic. Such heterogeneity is categorised in this study, which quantifies its impact on nutrient flows and soil fertility status at region and farm scales, as a first step in identifying spatial and temporal niches for targeting of soil fertility management strategies and technologies. Transects for soil profile observation, participatory rural appraisal techniques and classical soil sampling and chemical analysis were sampled across 60 farms in three sub-locations (Emuhaia, Shinyalu, Aludeka), which together represent much of the variability found in the highlands of western Kenya. Five representative farm types were identified using socio-economic information and considering production activities, household objectives and the main constraints faced by farmers. Soil fertility management and nutrient resource flows were studied for each farm type and related to differences in soil fertility status at farm scale. Farm types 1 and 2 were the wealthiest; the former relied on off-farm income and farmed small pieces of land (0.6–1.1 ha) while the latter farmed relatively large land areas (1.6–3.8 ha) mainly with cash crops. The poorest farm type 5 also farmed small pieces of land (0.4–1.0 ha) but relied on low wages derived from working for wealthier farmers. Both farm types 1 and 5 relied on off-farm earnings and sold the least amounts of farm produce to the market, though the magnitude of their cash, labour and nutrient flows was contrasting. Farms of types 3 and 4 were intermediate in size and wealth, and represented different crop production strategies for self-consumption and the market. Average grain yields fluctuated around 1 t ha−1 year−1 for all farm types and sub-locations. Grain production by farms of types 4 and 5 was much below annual family requirements, estimated at 170 kg person−1 year−1. Household wealth and production orientation affected the pattern of resource flow at farm scale. In the land-constrained farms of type 1, mineral fertilisers were often used more intensively (ca. 50 kg ha−1), though with varying application rates (14–92 kg ha−1). The use of animal manure in such small farms (e.g. 2.2 t year−1) represented intensities of use of up to 8 t ha−1, and a net accumulation of C and macronutrients brought into the farm by livestock. In farms of type 5, intensities of use of mineral and organic fertilisers ranged between 0–12 kg ha−1 and 0–0.5 t ha−1, respectively. A consistent trend of decreasing input use from farm types 1–5 was generally observed, but nutrient resources and land management practices (e.g. fallow) differed enormously between sub-locations. Inputs of nutrients were almost nil in Aludeka farms. Both inherent soil properties and management explained the variability found in soil fertility status. Texture explained the variation observed in soil C and related total N between sub-locations, whereas P availability varied mainly between farm types as affected by input use. 相似文献
138.
通过对锥形件产品的研制 ,论证了采用复合挤压、变薄拉伸和扩锥挤压相结合的工艺方法是加工深孔薄壁锥形件的可靠工艺方法 ,得出了变薄拉伸加工中加工率不应处于临界加工率状态的结论。 相似文献
139.
以釉面陶瓷和普通钠钙玻璃为载体,用溶胶凝胶法在其表面进行了纳米TiO2薄膜的负载.采用X射线衍射法(XRD)、扫描电子显微镜(SEM)和X射线光电子能谱仪(XPS)对薄膜进行了表征与分析.结果表明,TiO2为完全的锐钛矿型,平均粒径约为15nm;TiO2薄膜在2种载体上分布均匀,膜厚约为300nm;TiO2薄膜在釉面陶瓷表面呈连续分布,而在玻璃表面上出现了破裂现象;2种载体中的一些基质离子在TiO2薄膜均有渗透.光降解实验表明,2种载体上的TiO2薄膜对亚甲基蓝的降解均符合一级反应动力学.TiO2/釉面陶瓷催化活性大于TiO2/玻璃,该薄膜对实际生产多菌灵废水具有催化降解作用.2种载体上的TiO2薄膜重复使用20次,对亚甲基蓝的去除率降低约2%. 相似文献
140.
Gerald K. Moore Gary W. North 《Journal of the American Water Resources Association》1974,10(5):1082-1096
ABSTRACT: Panchromatic black and white, color, and color infrared photographs and thermal infrared imagery are compared for a capability to show flood boundaries. In open agricultural and urban areas, these boundaries are easily delineated on all types of am. Boundaries are more difficult to see in wooded areas. In March, hardwood trees are dormant, but black and white photographs and color photographs show only the tops of these trees. Color infrared photographs in January and March have a distinctive color or tone in inundated woods; the limit of this tone is the flood boundary. Daytime thermal infrared imagery in March shows that inundated woods are cooler than dry land but warmer than open water. After about April 1, both color infrared photography and thermal infrared imagery show only the top of the tree canopy and do not reflect underlying flood water. Inundated areas can be delineated easily on ERTS satellite imagery from December through March. On imagery from May 4–5, 1973, however, most inundation boundaries had to be drawn as dashed lines; the tree canopy obscures flood waters in wooded areas. Despite this problem, the results of mapping flood boundaries on May imagery are believed to be reasonable for the scale of the imagery. 相似文献