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131.
Ammara Habi Bin Chen Bushra Khali Saichun Tan Huizheng Che Tariq Mahmoo Guangyu Shi Muhammad Tahir Butt 《环境科学学报(英文版)》2019,31(2):154-166
This study presents detailed analysis of spatiotemporal variations and trend of dust optical properties i.e., Aerosol Optical Depth(AOD) and Angstrom component over Asian desert regions using thirteen years of data(i.e., 2001–2013) retrieved from Aerosol Robotic Network(AERONET), Moderate Resolution Imaging Spectroradiometer(MODIS) and Multi-angle Imaging Spectroradiometer(MISR). These regions include Solar Village, Dunhuang and Dalangzadgad and are considered as origin of desert aerosols in Asia. Mann–Kendall trend test was used to show the trend of AOD. The relationship of AOD with weather parameters and general AOD trend over different wavelengths has also been shown. AOD's trend has been observed significant throughout the year in Solar Village, while in Dunhuang and Dalanzadgad the significant trend has been found only in peak period(March–June).Analysis show high values of AOD and low values of angstrom in Solar Village during peak period. In Chinese desert regions, high values of AOD have been found during peak period and low values in pre-peak period. Significant relationship has been observed between AOD and average temperature in Solar Village and Dalanzadgad whereas rainfall and wind speed showed no significant impact on AOD in all desert regions. 相似文献
132.
生态足迹的实证分析--中国经济增长中的生态制约 总被引:15,自引:0,他引:15
本文通过中国生态足迹的实证分析,讨论了生态系统资源供给方面对经济增长的制约,资源生态足迹是生态足迹的主要部分,反映了经济系统的资源消费,计算发现,1961-1999年中国资源生态足迹持续增长,从1961年的3.3亿hm^2年递增到1999年的16.8亿hm^2年平均增长率为4.4%,资源生态足迹的增长支持了同期的经济增长,但是,实证比较发展资源生态承载力大大低于资源生态足迹,这些实证结果表晨;一方面,中国经济持续增长造成了资源消费持续增加,而另一方面,中国生态系统资源供给能力有限,不能支持当前的资源消费及其增长,由于自然资源是经济系统进行生产的特质基础,其供给不足必然成为经济增长的制约因素。 相似文献
133.
134.
广西农业可持续发展的策略和措施 总被引:3,自引:0,他引:3
广西地处亚热带,光热水资源丰富,具有农业发展的良好条件。近年来,广西采取了一系列的改革措施,农业经济得到了较快发展。但在农业经济发展的同时,也面临着许多资源与环境问题。本文在分析广西农业经济发展的现状及其存在问题的基础上,提出了广西农业可持续发展的策略和措施 相似文献
135.
Stable carbon isotope variability in marine macrophytes and its implications for food web studies 总被引:5,自引:0,他引:5
Stable carbon isotope ratios (13C) of eelgrass Zostera marina and of kelp Laminaria longicruris showed considerable variation in time and space. The isotopic composition of Z. marina varied seasonally from a mean of-6 for leaves formed in June to a mean of-10 for leaves formed in February. The maximum range for individual leaves was from-5 to-11.4. Once a leaf was fully formed, its isotopic composition appeared not to change. In L. longicruris there was no clear seasonal pattern of variation, but in any given blade there was a spatial pattern of variation, with the thickened central band tending to be least negative and the margins most negative. In one blade the range was from-12 to-20. Since this range overlaps values that are found in various other macrophytes and in seston, the value of the stable carbon isotope ratio as a tracer in food webs involving macroalgae is questioned. For Z. marina, in which the values are seasonally predictable, the technique may be useful if interpreted with care. The most probable explanation of variation in the ratios is differential storage of biochemical components of different isotopic compostion. 相似文献
136.
Two hexazinone-degrading bacterial strains were isolated from soil by enrichment culture technique, and identified as Pseudomonas sp. and Enterobacter cloacap. The two purified isolates, designated as WFX-1 and WFX-2, could rapidly degrade hexazinone with a half-life of 3.08 days and 2.95 days in mineral salt medium (MSM), while their mixed bacterial culture was found to degrade hexazinone, at an initial concentration of 50 microg/ml, by enhancing 2.3-fold over that when the isolates were used alone. Two microbial metabolites (A and D) were obtained by preparative TLC and identified on the basis of the spectral data of IR, 1H NMR and HPLC-ESI-MS, but both of them were known products as they had been reported in soil and vegetation metabolites of hexazinone. However, metabolites B and C were new degradates, whose molecular weights (MW) were 157 and 156, respectively, being reported from microbial metabolism for the first time. 相似文献
137.
在污水压力输送管道中,污水中气体的存在会影响液体的流动,以污水管中的气、液相流为研究对象,运用集中空穴模型(气泡离散分布模型)和均匀分布模型两种计算方法,来研究停泵水锤过程的压力和流速的变化趋势,实例计算结果表,在设有止回阀的水锤现象中,利用离散分布模型所得的最高水位要比利用均匀分布模型的计算值高,在不设止回阀的水锤现象中,两者的结构基本保持一致。均匀分布模型假定气体在水中呈均匀分布,因此在计算断面上的气体量变化不如离散分布模型来得剧烈,其水位正峰值比离散分布模型低,负峰值比离散分布模型高。 相似文献
138.
Contrasting structure and composition of the understory in species-rich tropical rain forests 总被引:1,自引:0,他引:1
LaFrankie JV Ashton PS Chuyong GB Co L Condit R Davies SJ Foster R Hubbell SP Kenfack D Lagunzad D Losos EC Nor NS Tan S Thomas DW Valencia R Villa G 《Ecology》2006,87(9):2298-2305
In large samples of trees > or = 1 cm dbh (more than 1 million trees and 3000 species), in six lowland tropical forests on three continents, we assigned species with >30 individuals to one of six classes of stature at maturity (SAM). We then compared the proportional representation of understory trees (1-2 cm dbh) among these classes. The understory of the three Asian sites was predominantly composed of the saplings of large-canopy trees whereas the African and American sites were more richly stocked with trees of the smaller SAM classes. Differences in class representation were related to taxonomic families that were present exclusively in one continent or another. Families found in the Asian plots but not in the American plot (e.g., Dipterocarpaceae, Fagaceae) were predominantly species of the largest SAM classes, whereas families exclusive to the American plots (e.g., Melastomataceae sensu stricto, Piperaceae, and Malvaceae [Bombacacoidea]) were predominantly species of small classes. The African plot was similar to Asia in the absence of those American families rich in understory species, while similar to America in lacking the Asian families rich in canopy species. The numerous understory species of Africa were chiefly derived from families shared with Asia and/or America. The ratio of saplings (1-2 cm dbh) to conspecific canopy trees (>40 cm dbh) was lower in American plots than in the Asian plots. Possible explanations for these differences include phenology, moisture and soil fertility regimes, phyletic constraints, and the role of early successional plants in forest development. These results demonstrate that tropical forests that appear similar in tree number, basal area, and the family taxonomy of canopy trees nonetheless differ in ecological structure in ways that may impact the ecology of pollinators, dispersers, and herbivores and might reflect fundamental differences in canopy tree regeneration. 相似文献
139.
Application of SO(4)(2-)/TiO2 solid superacid in decontaminating radioactive pollutants 总被引:4,自引:0,他引:4
Polyaniline doped with SO(4)(2-)/TiO(2) superacid shows good conductive ability. When used in a strippable coating film for decontaminating radioactive pollutants, the SO(4)(2-)/TiO(2) solid superacid replacing HCl exhibits higher electrical conductivity (7.01 s/cm) and a decontamination ratio higher than 97%. Coating and electrolyzing the film in solution or in dry medium were effective methods, the latter was more promising for decontaminating radioactive pollutants which were attached to the surface or within the body of equipments used in nuclear industry. 相似文献
140.
某厂氩气纯化器是由1Cr18Ni9不锈钢制成,在使用过程中出现致密性的网状裂纹开裂。详细论述了氩气纯化器开裂失效的原因,并通过理论分析及实践摸索,找出了应对氩气纯化器失效的对策。并在实际运行中得到了验证,确保了新制氩气纯化器的安全可靠运行。 相似文献