全文获取类型
收费全文 | 1451篇 |
免费 | 31篇 |
国内免费 | 16篇 |
专业分类
安全科学 | 77篇 |
废物处理 | 73篇 |
环保管理 | 293篇 |
综合类 | 152篇 |
基础理论 | 357篇 |
污染及防治 | 369篇 |
评价与监测 | 109篇 |
社会与环境 | 49篇 |
灾害及防治 | 19篇 |
出版年
2023年 | 17篇 |
2022年 | 15篇 |
2021年 | 20篇 |
2020年 | 28篇 |
2019年 | 28篇 |
2018年 | 35篇 |
2017年 | 33篇 |
2016年 | 32篇 |
2015年 | 36篇 |
2014年 | 48篇 |
2013年 | 191篇 |
2012年 | 64篇 |
2011年 | 69篇 |
2010年 | 47篇 |
2009年 | 55篇 |
2008年 | 60篇 |
2007年 | 73篇 |
2006年 | 56篇 |
2005年 | 52篇 |
2004年 | 40篇 |
2003年 | 44篇 |
2002年 | 42篇 |
2001年 | 41篇 |
2000年 | 24篇 |
1999年 | 25篇 |
1998年 | 20篇 |
1997年 | 18篇 |
1996年 | 19篇 |
1995年 | 13篇 |
1994年 | 18篇 |
1993年 | 18篇 |
1992年 | 13篇 |
1991年 | 13篇 |
1990年 | 12篇 |
1989年 | 9篇 |
1987年 | 14篇 |
1986年 | 14篇 |
1985年 | 12篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 14篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1979年 | 12篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1973年 | 6篇 |
1967年 | 4篇 |
排序方式: 共有1498条查询结果,搜索用时 31 毫秒
961.
962.
Over 114 different human enteric viruses are known. They are all excreted into sewage, and opportunities exist for them to find their way into water distribution systems. The characteristics of the illnesses caused by enteric viruses make their transmission by water difficult to recognize. Methods are not available for isolating all of the enteric viruses from water, so that finding any type of human virus in drinking water is an indication that other types may also be present. With improvements in technology, our laboratory has recently been able to detect group B coxsackieviruses, rotaviruses, and hepatitis A virus in chlorinated drinking water. At present, there are no uniform methods for concentrating, isolating, and identifying viruses in water. Emphasis should be placed on seeking uniformity in methods so that standards can be set for viruses in water. 相似文献
963.
The current article focuses on gasification as a primary disposal solution for cellulosic wastes derived from chicken farms, and the possibility to recover energy from this process. Wood shavings and chicken litter were characterized with a view to establishing their thermal parameters, compositional natures and calorific values. The main products obtained from the gasification of chicken litter, namely, producer gas, bio-oil and char, were also analysed in order to establish their potential as energy sources. The experimental protocol included bomb calorimetry, pyrolysis combustion flow calorimetry (PCFC), thermo-gravimetric analyses (TGA), differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, elemental analyses, X-ray diffraction (XRD), mineral content analyses and gas chromatography. The mass and energy balances of the gasification unit were also estimated. The results obtained confirmed that gasification is a viable method of chicken litter disposal. In addition to this, it is also possible to recover some energy from the process. However, energy content in the gas-phase was relatively low. This might be due to the low energy efficiency (19.6%) of the gasification unit, which could be improved by changing the operation parameters. 相似文献
964.
Population Structure and Cryptic Evolutionary Units in the Alligator Snapping Turtle 总被引:5,自引:0,他引:5
Joseph Roman Steven D. Santhuff Paul E. Moler & Brian W. Bowen 《Conservation biology》1999,13(1):135-142
The alligator snapping turtle ( Macroclemys temminckii ) is a long-lived, slow-growing chelydrid turtle found in Gulf of Mexico drainages from Florida to Texas (U.S.A.). Populations are thought to be depleted throughout the range due in part to an increased harvest in the 1960s through 1980s. To identify population and evolutionary units, 420 base pairs were sequenced within the mitochondrial DNA control region of 158 specimens from 12 drainages. Results indicate substantial phylogeographic structuring and strong population-level separations among river drainages. Eight of 11 haplotypes were observed to be river-specific, providing diagnostic markers for most drainages. Three partitions are resolved in the mtDNA genealogy, corresponding to the eastern, central, and western portion of the species' range. These separations coincide with recognized biogeographic provinces. The population structure by river system indicates that many drainages are distinct management units, with the Suwannee River lineage possibly deserving special attention, based on the criterion of genetic distinctiveness. The partitioning of M. temminckii into river-specific populations illustrates the management framework and conservation challenges that apply to a broad array of riverine species. Drainage-specific molecular markers may be used to identify the geographic origin of turtle products in the marketplace. 相似文献
965.
966.
967.
John M. Pierrard Ronald D. Snee Joseph Zelson 《Journal of the Air & Waste Management Association (1995)》2013,63(9):841-848
Urban ambient air quality trend analysis was evaluated as an alternative to rollback analysis to estimate vehicle emission standards needed to achieve national ambient air quality standards. Examination of the trends of monthly maximum 8 hour average carbon monoxide concentrations, central business district traffic activity, and emission rates from vehicles on the road suggests that the automotive exhaust emission standard for carbon monoxide derived in response to the requirements of the Clean Air Act Amendments of 1970 may be ten times too severe. The excessive stringency of the vehicle emission standard for carbon monoxide was confirmed by two different analyses of the correlation between annual mean carbon monoxide concentration and frequency of occurrence of carbon monoxide concentrations above the level of the 8-hour standard. One correlation analysis using all available CAMP data involved an empirical approach and the other assumed that carbon monoxide concentrations are described by the lognormal distribution. Based on the analysis of CAMP air quality data, a vehicle carbon monoxide emission standard of approximately 29 grams per mile appears adequate to meet the ambient air quality standard. The large difference between the results of this analysis and the 1976 Federal vehicle carbon monoxide emission standard indicates the advisability of applying this methodology to verification of the standards for hydrocarbons and oxides of nitrogen. 相似文献
968.
969.
Fine-scale movement patterns in penaeid prawns are rarely observed in situ, but are essential in understanding habitat use,
foraging, and anti-predator behaviour. Acoustic telemetry was applied to examine the activity, space utilization, and habitat
use of the eastern king prawn Penaeus (Melicertus) plebejus, at small temporal and spatial scales. Tracking of sub-adult P. plebejus (n = 9) in Wallagoot Lake (36.789°S, 149.959°E; 23 April–12 May 2009) and calculation of a minimum activity index (MAI) revealed high variation in activity rates across diel periods and in different habitats. Elevated activity rates and movement
indicated foraging in unvegetated habitats during the night. Areas within the 95 and 50% space utilization contours averaged
2,654.1 ± 502.0 and 379.9 ± 103.9 m2, respectively, and there was a significant negative relationship between these areas and prawn activity rates in unvegetated
habitats. This study provides the first estimates of prawn activity rates and space utilization in the field. Application
of acoustic telemetry can increase knowledge of prawn movements and their interactions with other marine species in different
habitats. 相似文献
970.
J. O. Ivie M. D. Thomas O. C. Taylor C. Ray Thompson W. M. Dugger JR. B. L. Richards 《Journal of the Air & Waste Management Association (1995)》2013,63(8):355-359
A discussion of the methods used to determine the most economic design of chimney for a new thermal power station or large industrial plant is presented, with the objective that ground level concentration of pollutants will be kept at a minimum. Attention is paid to the geography and climatology of the site, with special reference to the frequency and height of inversions and the prevailing wind direction and speed. A method is illustrated in using a large thermal power station as an example. The maximum sulfur dioxide concentrations at ground level are computed for several chimney heights and gas exit velocities. The values of these sulfur dioxide concentrations, the capital cost of the chimney, the pumping costs, and the gas pressures within the chimney are considered in selecting a suitable chimney height and a gas exit velocity which will meet most economically the stated objective. The paper deals primarily with chimneys for industrial or power boiler plant of maximum continuous rating greater than 450 million Btu/hr (about 450,000 lbs of steam/hr), or to chimneys serving furnaces burning fuel at a maximum rate greater than 50,000 lbs/hr of coal, or 80,000 lbs/hr of oil. For chimneys serving plant with smaller heat inputs, chimney selection by reference to Clean Air Act 1956, Memorandum on Chimney Heights is suggested. 相似文献