全文获取类型
收费全文 | 16181篇 |
免费 | 102篇 |
国内免费 | 104篇 |
专业分类
安全科学 | 396篇 |
废物处理 | 762篇 |
环保管理 | 1822篇 |
综合类 | 3187篇 |
基础理论 | 3770篇 |
环境理论 | 6篇 |
污染及防治 | 4120篇 |
评价与监测 | 1031篇 |
社会与环境 | 1216篇 |
灾害及防治 | 77篇 |
出版年
2022年 | 161篇 |
2021年 | 147篇 |
2019年 | 108篇 |
2018年 | 216篇 |
2017年 | 206篇 |
2016年 | 318篇 |
2015年 | 231篇 |
2014年 | 375篇 |
2013年 | 1195篇 |
2012年 | 455篇 |
2011年 | 636篇 |
2010年 | 527篇 |
2009年 | 593篇 |
2008年 | 656篇 |
2007年 | 711篇 |
2006年 | 633篇 |
2005年 | 532篇 |
2004年 | 535篇 |
2003年 | 554篇 |
2002年 | 489篇 |
2001年 | 660篇 |
2000年 | 458篇 |
1999年 | 292篇 |
1998年 | 153篇 |
1997年 | 170篇 |
1996年 | 160篇 |
1995年 | 212篇 |
1994年 | 205篇 |
1993年 | 177篇 |
1992年 | 177篇 |
1991年 | 200篇 |
1990年 | 181篇 |
1989年 | 173篇 |
1988年 | 176篇 |
1987年 | 162篇 |
1986年 | 137篇 |
1985年 | 135篇 |
1984年 | 166篇 |
1983年 | 167篇 |
1982年 | 167篇 |
1981年 | 119篇 |
1980年 | 120篇 |
1979年 | 133篇 |
1978年 | 113篇 |
1977年 | 107篇 |
1976年 | 98篇 |
1975年 | 107篇 |
1974年 | 126篇 |
1973年 | 95篇 |
1972年 | 94篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
931.
932.
D. F. Adams S. O. Farwell M. R. Pack E. Robinson 《Journal of the Air & Waste Management Association (1995)》2013,63(10):1083-1089
Data are presented for the first systematic measurements of biogenic sulfur gas flux from the major soil orders within the eastern and southeastern United States. Sulfur flux samples were collected and analyzed on-site during the fall of 1977, spring and summer of 1978 and summer of 1979. A total of 27 sampling locales in 17 states were examined. Eight additional sites were visited in 1980. At some locales, two to four soils were examined, providing an even broader sampling of the soil orders. Three of the locales were revisited two or three times during the course of the study to establish the influence of seasonal climatology upon the measured emission rates and chemical composition of the sulfur flux mixtures. The sulfur gas enhancement of sulfur-free sweep air passing through dynamic emission flux chambers placed over selected sampling areas was determined by combined cryogenic enrichment sampling and wall-coated, open tubular, capillary column, cryogenic gas chromatography (WCOT/GC) using a sulfur selective, flame photometric detector (FPD). Sulfur gas mixtures varied with soil order, ambient temperature, insolation, soil moisture, cultivation, and vegetative cover. Statistical analyses indicated strong temperature and soil order relationships for sulfur emissions from soils. Fluxes ranged from 0.001 g to 1940 g of total sulfur as S/m2/yr. The calculated mean annual sulfur flux, weighted by soil order, was 0.03 g S/m2/yr for the study land area, or 110,872 metric tons (mT). The estimated annual average sulfur flux increased from 65 mT per 6400 km2 for the land grids in the northernmost east-west grid tier to an average 1800 mT for the land grids in the southern Florida grid tiers. This systematic sampling of major soils provides a much broader data base for estimating biogenic sulfur flux than previously reported for isolated intertidal sites, and presents the first sulfur flux estimates for inland soils which make up approximately 93% of the land of the eastern United States. 相似文献
933.
G. B. Howe R. K. M. Jayanty A. V. Rao W. F. Gutknecht C. E. Decker D. J. von Lehmden 《Journal of the Air & Waste Management Association (1995)》2013,63(9):823-826
A repository of 38 gaseous organic compounds in compressed gas cylinders has been established by EPA. This repository was established to provide standards for source test performance audits, that is, quantitative quality assurance tests. Among these compounds are ten halogenated organic species, which are the focus of this paper. Stability studies of all ten compounds have been performed to determine the feasibility of using them as performance audit standards. Results indicate that all of the halocarbons tested are adequately stable to be used as reliable audit standards. Subsequent to completion of stability studies, four of the ten halocarbons were used in source test performance audits. Results are available at this time for two of the four compounds; the results show agreement within 10% of the concentrations previously established by Research Triangle Institute. 相似文献
934.
935.
Roy E. Bickelhaupt Ralph F. Altman 《Journal of the Air & Waste Management Association (1995)》2013,63(8):831-838
Research has been conducted to develop a technique for predicting the effective volume resistivity of a fly ash layer that has been exposed to circumstances leading to a hot-side precipitator problem known as sodium depletion. Eight fly ashes, representing a major portion of U.S. coals, were evaluated by subjecting 0.5 cm ash layers to a continuously applied voltage gradient of 4 kV/cm for periods of time up to 35 days at a temperature of 350°C (662°F). Resistivity was determined at 350°C before the test started and after the long period of applied voltage used to create the sodium depleted situation. In this condition, resistivity was also determined at 280°C (536°F) for an average electric field Intensity of 4 kV/cm and immediately prior to breakdown. This experimental method can be used with any ash sample to estimate resistivity In a sodium depleted condition. But in addition, a correlation resulting from these resistivity data has been developed. This correlation Is combined with an existing technique for predicting resistivity to produce a method for calculating the expected ash layer resistivity after sodium depletion has occurred. 相似文献
936.
937.
Robert F. Hodanbosi Robert Brodkey 《Journal of the Air & Waste Management Association (1995)》2013,63(4):371-374
Coal combustion is the primary contributor to atmospheric pollution in China, especially so In big cities. Particulate matter and sulfur dioxide are the two main pollutants worthy of attention. Concentration of suspended particles is usually higher in northern cities than in southern cities and higher in winter than in summer. In the case of sulfur dioxide, concentrations are high in the heating season (wintertime) in northern cities, but also in some of the cities in the southwest part of China. Rainfall with pH less than 5.6 occurs mostly to the south of the Yangtze River, especially so in the cities of Chongqing and Gueiyang, and their neighboring areas, and also In the southwest part of China. No acid rain, however, has been found in Beijing and Tianjin. Although the formation of acid rain can thus be thought of as dependent on the presence of enough sulfur dioxide, other factors such as airborne particles and ammonia also play an important role. The difference is, therefore, explained and theorem postulated with supporting data. Ways of abating atmospheric pollution are, in essence, related to improved coal burning; some simple methods are suggested for nationwide control options. 相似文献
938.
939.
Experimental Characterization of Atmospheric Diffusion in Complex Terrain with Land-Sea Interactions
M. M. Mill´n E. Otamendi L. A. Alonso I. Ureta 《Journal of the Air & Waste Management Association (1995)》2013,63(7):807-811
The body of information presented in this paper is directed to scientists working in atmospheric dispersion research and model development. Two years of field measurements in the coastal area of Bilbao in northern Spain show that the diffusion behavior in this complex terrain can be classified into several well defined patterns, which correspond to certain meteorological conditions. The approach taken has been the systematic use of SO2 remote sensors (COSPEC) and ground level monitors in moving platforms which are used to follow and document the flow of the air mass. Results to date show that complex reentry cycles can occur and that synoptically different flows may be indistinguishable by wind sensors at ground level (affected by channeling), and yet result in totally different observed pollution levels by a fixed monitoring network (affected by topographical effects). These results are being used to parameterize the cause-effect relationships and guide the modeling efforts in this area of complex terrain. 相似文献
940.
A. G. Blasewitz B. F. Judson 《Journal of the Air & Waste Management Association (1995)》2013,63(4):223-229
Abstract An ozone (O3) exposure assessment study was conducted in Toronto, Ontario, Canada during the winter and summer of 1992. A new passive O3 sampler developed by Harvard was used to measure indoor, outdoor, and personal O3 concentrations. Measurements were taken weekly and daily during the winter and summer, respectively. Indoor samples were collected at a total of 50 homes and workplaces of study participants. Outdoor O3 concentrations were measured both at home sites using the passive sampler and at 20 ambient monitoring sites with continuous monitors. Personal O3 measurements were collected from 123 participants, who also completed detailed time-activity diaries. A total of 2,274 O3 samples were collected. In addition, weekly air exchange rates of homes were measured. This study demonstrates the performance of our O3 sampler for exposure assessment. The data obtained are further used to examine the relationships between personal, indoor (home and workplace), and outdoor O3 concentrations, and to investigate outdoor and indoor spatial variations in O3 concentrations. Based on home outdoor and indoor, workplace, and ambient O3 concentrations measured at the Ontario Ministry of the Environment (MOE) sites, the traditional microenvironmental model predicts 72% of the variability in measured personal exposures. An alternative personal O3 exposure model based on outdoor measurements and time-activity information is able to predict the mean personal exposures in a large population, with the highest R2 value of 0.41. 相似文献