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排序方式: 共有574条查询结果,搜索用时 31 毫秒
541.
Roy JW Hall JC Parkin GW Wagner-Riddle C Clegg BS 《Journal of environmental quality》2001,30(4):1360-1370
The leaching of surface-applied herbicides, such as dicamba (2methoxy-3,6-dichlorobenzoic acid), to ground water is an environmental concern. Seasonal changes in soil temperature and water content, affecting infiltration and biodegradation, may control leaching. The objectives of this study were to (i) investigate the leaching of dicamba applied to turfgrass, (ii) measure the degradation rate of dicamba in soil and thatch in the laboratory under simulated field conditions, and (iii) test the ability of the model EXPRES (containing LEACHM) to simulate the field transport and degradation processes. Four field lysimeters, packed with sandy loam soil and topped with Kentucky bluegrass (Poa pratensis L.) sod, were monitored after receiving three applications (May, September, November) of dicamba. Concentrations of dicamba greater than 1 mg L(-1) were detected in soil water. Although drying of the soil during the summer prevented deep transport, greater leaching occurred in late autumn due to increased infiltration. From the batch experiment, the degradation rate for dicamba in thatch was 5.9 to 8.4 times greater than for soil, with a calculated half-life as low as 5.5 d. Computer modeling indicated that the soil and climatic conditions would influence the effectiveness of greater degradation in thatch for reducing dicamba leaching. In general, EXPRES predictions were similar to observed concentration profiles, though peak dicamba concentrations at the 10-cm depth tended to be higher than predicted in May and November. Differences between predictions and observations are probably a result of minor inaccuracies in the water-flow simulation and the model's inability to modify degradation rates with changing climatic conditions. 相似文献
542.
543.
Harry M. Ohlendorf Katherine C. Marois Roy W. Lowe Thomas E. Harvey Paul R. Kelly 《Environmental monitoring and assessment》1991,18(2):105-122
Surf scoters (Melanitta perspicillata) were collected from 6 locations in San Francisco Bay during January and March 1985. Overall, mean concentrations of cadmium and zinc were higher in livers of scoters from the southern region of the Bay, whereas mean iron and lead were higher in those from the northern Bay region. Mean concentrations of arsenic, copper, lead, zinc, aluminum (January only) and iron (January) also differed among individual locations. Mean concentrations of copper and zinc increased, arsenic decreased, and cadmium remained the same between January and March. Selenium and mercury concentrations in scoter livers were not significantly correlated (P>0.05), but cadmium concentrations in livers and kidneys were positively correlated (P<0.0001), and body weight was negatively related to mercury concentration in the liver (P<0.05). Body weight differed among locations but not between January and March. Body weight was correlated with lipid content (P<0.0001). DDE and PCBs were each detected in 34 of 36 scoter carcasses. DDE increased significantly between January and March at Richmond Harbor, but BCBs did not differ between January and March at the 3 locations that could be tested. 相似文献
544.
In this paper we use a dynamic three sector model to examine the neutrality and welfare effects of land income taxes. We find that (1) taxes that are neutral in long run equilibrium need not be neutral in the short run; (2) short run neutrality depends upon the tax treatment of development costs and losses; and (3) many of the neutrality results hold under both static and rational expectations assumptions. We also find that, even without externality assumptions, nonneutrality in the short run does not necessarily entail a welfare cost and may be welfare-enhancing when agents have less-than-perfect foresight. 相似文献
545.
Abstract: The spatial scale and location of land whose development has the strongest influence on aquatic ecosystems must be known to support land use decisions that protect water resources in urbanizing watersheds. We explored impacts of urbanization on streams in the West River watershed, New Haven, Connecticut, to identify the spatial scale of watershed imperviousness that was most strongly related to water chemistry, macroinvertebrates, and physical habitat. A multiparameter water quality index was used to characterize regional urban nonpoint source pollution levels. We identified a critical level of 5% impervious cover, above which stream health declined. Conditions declined with increasing imperviousness and leveled off in a constant state of impairment at 10%. Instream variables were most correlated (0.77 ≤ |r| ≤ 0.92, p < 0.0125) to total impervious area (TIA) in the 100‐m buffer of local contributing areas (~5‐km2 drainage area immediately upstream of each study site). Water and habitat quality had a relatively consistent strong relationship with TIA across each of the spatial scales of investigation, whereas macroinvertebrate metrics produced noticeably weaker relationships at the larger scales. Our findings illustrate the need for multiscale watershed management of aquatic ecosystems in small streams flowing through the spatial hierarchies that comprise watersheds with forest‐urban land use gradients. 相似文献
546.
Asbestos cement (AC) pipes were commonly installed in the drinking water distribution systems from the mid 1920s to the late 1980s. In recent years, an increase in the number of water main breaks has occurred in the AC portions of some pipe networks, which can be partially attributed to the corrosion of the aged pipes. This study evaluated the potential role that microorganisms may have played in the degeneration and failure of AC pipes. In this study, a fresh AC pipe section was collected from the distribution network of the City of Regina, Canada and examined for microbiological activities and growth on inside surfaces of pipe sample. Black slime bacterial growths were found to be attached to inner pipe surfaces and a distinctively fibrous internal coating (patina) with iron oxides was formed over the time. The microbial populations inside the patina and the black slime were tested with BART(tm) testers. Heterotrophic aerobic bacteria (HAB) and slime forming bacteria (SLYM) dominated in both the black growths and inside the patina. Iron related bacteria, denitrification bacteria and sulfate reducing bacteria were also commonly present. Microbial challenge assays were conducted by submerging the cut segments of the AC pipe into selected bacterial cultures for a period of 10 days under both aerobic and anaerobic environments. Weight changes were determined and the surface morphology was examined for each of the assayed pipe segments. Results indicated that acid producing bacteria, SLYM and HAB could facilitate the pipe weight loss under anaerobic environments. 相似文献
547.
Sonia Akter Roy Brouwer Saria Choudhury Salina Aziz 《Mitigation and Adaptation Strategies for Global Change》2009,14(3):215-229
The study aims to assess the commercial viability of a potential crop insurance market in Bangladesh. In a large scale household
survey, agricultural farm households were asked for their preferences for a hypothetical crop insurance scheme using double
bounded (DB) contingent valuation (CV) method. Both revenue and production cost based indemnity payment approaches were applied
to assess the commercial viability of a crop insurance program assuming a partner-agent (PA) model of insurance supply. Crop
insurance is found marginally commercially viable in riverine flood plain areas. The expected indemnity payable consistently
exceeds the expected insurance premium receivable by the insurer for the households living in wetland basin and coastal floodplain.
We conclude that a uniform structure of crop insurance market does not exist in Bangladesh. The nature of the disaster risks
faced by the farm households and the socio-economic characteristics of the rural farm communities need to be taken into careful
consideration while designing such an insurance scheme.
相似文献
Sonia AkterEmail: |
548.
Kazuya Goto Hiromichi Okabe Firoz Alam Chowdhury Shinkichi Shimizu Yuichi Fujioka Masami Onoda 《International Journal of Greenhouse Gas Control》2011,5(5):1214-1219
In order to establish energy-saving technology for CO2 capture from blast furnace gas, novel absorbents were developed in the laboratory and evaluated at a 1 tCO2/d test plant. At first, CO2 absorption and desorption behaviors of single-component amine solvents for simulated blast furnace gas (CO2/N2 = 20%/80%) were investigated through a screening test using a small scrubbing bottle. These amine solvents were additionally analyzed using nuclear magnetic resonance (13C NMR) spectroscopy and reaction calorimetry. The results of the laboratory experiments showed that there was a trade-off between absorption rate and enthalpy of absorption but some absorbents had unique features. For example, 2-isopropylaminoethanol (IPAE) had high absorption rate and small enthalpy of absorption. Then, new IPAE-based amine solvents (RITE solvents: RITE-A and RITE-B) were formulated and evaluated at the 1 tCO2/d test plant. CO2 regeneration energies of the RITE solvents were 3.3 and 3.1 GJ/tCO2, respectively. With certain process conditions and plant specifications optimized, RITE-B was estimated to have the potential to achieve 2.5 GJ/tCO2. 相似文献
549.
Srivastava R Roy BK 《Journal of environmental biology / Academy of Environmental Biology, India》2011,32(5):629-634
The isolation procedure of the seed proteins of Amaranthus blitum have been analyzed at different pH conditions. Qualitative studies were carried out by using electrophoretic technique sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Mainly four protein fractions i.e. albumin, globulin, prolamin and glutelin were obtained. Protein isolates were prepared by (a) extraction at different alkaline pH (9, 10, 11 and 12) and precipitation atpH 5 and (b) extraction at pH 9 and precipitation atdifferentpH (4, 5, 6 and 7). The composition of isolates, prepared by method (a), depended on extraction pH. The isolate extracted at pH 8 was mainly composed of albumin and globulin, whereas at pH 9, 10 and 11 showed the presence of prolamin and glutelin. Electrophoretic pattern of different isolates had five major bands with molecular weight of 30, 45, 72, 84 and 90 kDt respectively. The increase of the extraction pH led to the increase in protein yield. With method (b) isolates obtained were variable in composition. At pH 7 albumin and prolamine were present, whereas at pH 4, 5 and 6 all 4 protein fractions were precipitated. According to the quantitative estimation of the albumin, globulin, prolamin and glutelin in the seed flour the contents were 26.4, 25, 5.81 and 42.7%, respectively. The results suggest that composition of protein isolates could be controlled by different extraction and precipitation pH. 相似文献
550.
Henriette?I.?JagerEmail author Mark?S.?Bevelhimer Roy?L.?King Katy?A.?Smith 《Environmental management》2011,48(4):795-807
Military landscapes represent a mixture of undisturbed natural ecosystems, developed areas, and lands that support different
types and intensities of military training. Research to understand water-quality influences of military landscapes usually
involves intensive sampling in a few watersheds. In this study, we developed a survey design of accessible headwater watersheds
intended to improve our ability to distinguish land–water relationships in general, and training influences, in particular,
on Fort Stewart, GA. We sampled and analyzed water from watershed outlets. We successfully developed correlative models for
total suspended solids (TSS), total nitrogen (TN), organic carbon (OC), and organic nitrogen (ON), which dominated in this
blackwater ecosystem. TSS tended to be greater in samples after rainfall and during the growing season, and models that included
%Wetland suggested a “build-and-flush” relationship. We also detected a positive association between TSS and tank-training, which
suggests a need to intercept sediment-laden runoff from training areas. Models for OC showed a negative association with %Grassland. TN and ON both showed negative associations with %Grassland, %Wetland, and %Forest. Unexpected positive associations were observed between OC and equipment-training activity and between ON and %Bare ground + Roads. Future studies that combine our survey-based approach with more intensive monitoring of the timing and intensity of training
would be needed to better understand the mechanisms for these empirical relationships involving military training. Looking
beyond local effects on Fort Stewart streams, we explore questions about how exports of OC and nitrogen from coastal military
installations ultimately influence estuaries downstream. 相似文献