全文获取类型
收费全文 | 2568篇 |
免费 | 75篇 |
国内免费 | 24篇 |
专业分类
安全科学 | 182篇 |
废物处理 | 152篇 |
环保管理 | 544篇 |
综合类 | 298篇 |
基础理论 | 597篇 |
环境理论 | 3篇 |
污染及防治 | 583篇 |
评价与监测 | 179篇 |
社会与环境 | 94篇 |
灾害及防治 | 35篇 |
出版年
2023年 | 13篇 |
2022年 | 20篇 |
2021年 | 27篇 |
2020年 | 27篇 |
2019年 | 26篇 |
2018年 | 62篇 |
2017年 | 58篇 |
2016年 | 76篇 |
2015年 | 73篇 |
2014年 | 70篇 |
2013年 | 233篇 |
2012年 | 110篇 |
2011年 | 151篇 |
2010年 | 114篇 |
2009年 | 131篇 |
2008年 | 127篇 |
2007年 | 143篇 |
2006年 | 134篇 |
2005年 | 98篇 |
2004年 | 85篇 |
2003年 | 108篇 |
2002年 | 71篇 |
2001年 | 54篇 |
2000年 | 53篇 |
1999年 | 42篇 |
1998年 | 39篇 |
1997年 | 34篇 |
1996年 | 33篇 |
1995年 | 26篇 |
1994年 | 34篇 |
1993年 | 31篇 |
1992年 | 21篇 |
1991年 | 24篇 |
1990年 | 14篇 |
1989年 | 11篇 |
1988年 | 16篇 |
1987年 | 19篇 |
1986年 | 13篇 |
1985年 | 19篇 |
1984年 | 13篇 |
1983年 | 18篇 |
1982年 | 19篇 |
1981年 | 25篇 |
1980年 | 13篇 |
1979年 | 10篇 |
1978年 | 6篇 |
1977年 | 9篇 |
1971年 | 6篇 |
1957年 | 5篇 |
1955年 | 5篇 |
排序方式: 共有2667条查询结果,搜索用时 15 毫秒
581.
582.
Verrucaria rubrocincta Breuss is an endolithic lichen that inhabits caliche plates exposed on the surface of the Sonoran Desert. Caliche surface temperatures are regularly in excess of 60 degrees C during the summer and approach 0 degrees C in the winter. Incident light intensities are high, with photosynthetically active radiation levels typically to 2,600 micromol/m(2) s(-1) during the summer. A cross-section of rock inhabited by V. rubrocincta shows an anatomical zonation comprising an upper micrite layer, a photobiont layer containing clusters of algal cells, and a pseudomedulla embedded in the caliche. Hyphae of the pseudomedulla become less numerous with depth below the rock surface. Stable carbon and oxygen isotopic data for the caliche and micrite fall into two sloping, well-separated arrays on a delta(13)C-delta(18)O plot. The delta(13)C(PDB) of the micrite ranges from 2.1 to 8.1 and delta(18)O(SMOW) from 25.4 to 28.9, whereas delta(13)C(PDB) of the caliche ranges from -4.7 to 0.7 and delta(18)O(SMOW) from 23.7 to 29.2. The isotopic data of the micrite can be explained by preferential fixing of (12)C into the alga, leaving local (13)C enrichment and evaporative enrichment of (18)O in the water. The (14)C dates of the micrite range from recent to 884 years b.p., indicating that "dead" carbon from the caliche is not a significant source for the lichen-precipitated micrite. The endolithic growth is an adaptation to the environmental extremes of exposed rock surfaces in the hot desert. The micrite layer is highly reflective and reduces light intensity to the algae below and acts as an efficient sunscreen that blocks harmful UV radiation. The micrite also acts as a cap to the lichen and helps trap moisture. The lichen survives by the combined effects of biodeterioration and biomineralization. Biodeterioration of the caliche concomitant with biomineralization of a protective surface coating of micrite results in the distinctive anatomy of V. rubrocincta. 相似文献
583.
Akzo Nobel's Macro Porous Polymer Extraction (MPPE) technology effectively removes dissolved hydrocarbons from groundwater via liquid-liquid extraction with an innovative medium. Excellent performance in removal of chlorinated, aromatic, and aliphatic solvents, coupled with simple, robust design, make MPPE an attractive process for groundwater remediation applications. Hydrocarbon-contaminated water is passed through a column packed with MPPE particles. An extraction fluid, immobilized within the polymer matrix, removes the hydrocarbons from the water. All hydrocarbons with affinity for the extraction fluid (compared to water) are removed. Regeneration is accomplished in situ with low-pressure steam. The steam volatilizes the hydrocarbons but not theimmobilized extraction fluid. Volatilized hydrocarbons are condensed and then separated from condensate by gravity. The hydrocarbon product is available for recycle or reuse. MPPE systems achieve removal efficiencies of 99.99 percent for wide varieties and combinations of aliphatic, aromatic, and chlorinated compounds. For a broad range of mass loadings and effluent requirements, especially rigorous ones, the MPPE system offers lower investment and operating costs than traditional water treatment technologies. Currently, 14 industrial units are running or under construction in the United States and Europe. Eight of these are treating groundwater. 相似文献
584.
585.
Thomas K. Rudel Birthe Paul Douglas White I. M. Rao Rein Van Der Hoek Aracely Castro Maryline Boval Amy Lerner Laura Schneider Michael Peters 《Ambio》2015,44(7):685-693
The increased use of grain-based feed for livestock during the last two decades has contributed, along with other factors, to a rise in grain prices that has reduced human food security. This circumstance argues for feeding more forages to livestock, particularly in the tropics where many livestock are reared on small farms. Efforts to accomplish this end, referred to as the ‘LivestockPlus’ approach, intensify in sustainable ways the management of grasses, shrubs, trees, and animals. By decoupling the human food and livestock feed systems, these efforts would increase the resilience of the global food system. Effective LivestockPlus approaches take one of two forms: (1) simple improvements such as new forage varieties and animal management practices that spread from farmer to farmer by word of mouth, or (2) complex sets of new practices that integrate forage production more closely into farms’ other agricultural activities and agro-ecologies. 相似文献
586.
Paul Steenhof 《Environmental Modeling and Assessment》2009,14(1):17-28
The success of the Clean Development Mechanism of the Kyoto Protocol to reduce global greenhouse gas emissions requires that
there are scientifically sound and usable measurement methods for the emission baseline. Three different methods are investigated
in the context of China’s electrical sector: simulation with dispatch analysis, decomposition analysis, and operating and
build margin analysis. It is found that dispatch analysis is the best method available as it is able to consider important
regional and temporal dimensions, while decomposition analysis can help quantify the potential effects of different energy
and environment policy choices. 相似文献
587.
Janet A. Nestlerode Virginia D. Engle Pete Bourgeois Paul T. Heitmuller John M. Macauley Yvonne C. Allen 《Environmental monitoring and assessment》2009,150(1-4):21-29
The Environmental Protection Agency (EPA) and U.S. Geological Survey (USGS) initiated a two-year regional pilot survey in 2007 to develop, test, and validate tools and approaches to assess the condition of northern Gulf of Mexico (GOM) coastal wetlands. Sampling sites were selected from estuarine and palustrine wetland areas with herbaceous, forested, and shrub/scrub habitats delineated by the US Fish and Wildlife Service National Wetlands Inventory Status and Trends (NWI S&T) program and contained within northern GOM coastal watersheds. A multi-level, stepwise, iterative survey approach is being applied to multiple wetland classes at 100 probabilistically-selected coastal wetlands sites. Tier 1 provides information at the landscape scale about habitat inventory, land use, and environmental stressors associated with the watershed in which each wetland site is located. Tier 2, a rapid assessment conducted through a combination of office and field work, is based on best professional judgment and on-site evidence. Tier 3, an intensive site assessment, involves on-site collection of vegetation, water, and sediment samples to establish an integrated understanding of current wetland condition and validate methods and findings from Tiers 1 and 2. The results from this survey, along with other similar regional pilots from the Mid-Atlantic, West Coast, and Great Lakes Regions will contribute to a design and implementation approach for the National Wetlands Condition Assessment to be conducted by EPA’s Office of Water in 2011. 相似文献
588.
Conjunctive use of saline/non-saline irrigation waters is generally aimed at minimizing yield losses and enhancing flexibility
of cropping, without much alteration in farming operations. Recommendation of location-specific suitable conjunctive water
use plans requires assessment of their long-term impacts on soil salinization/sodification and crop yield reductions. This
is conventionally achieved through long-term field experiments. However such impact evaluations are site specific, expensive
and time consuming. Appropriate decision support systems (DSS) can be time-efficient and cost-effective means for such long-term
impact evaluations. This study demonstrates the application of one such (indigenously developed) DSS for recommending best
conjunctive water use plans for a, rice-wheat growing, salt affected farmer’s field in Gurgaon district of Haryana (India).
Before application, the DSS was extensively validated on several farmers and controlled experimental fields in Gurgaon and
Karnal districts of Haryana (India). Validation of DSS showed its potential to give realistic estimates of root zone soil
salinity (with R = 0.76–0.94; AMRE = 0.03–0.06; RMSPD = 0.51–0.90); sodicity (with R = 0.99; AMRE = 0.02; RMSPD = 0.84) and relative crop yield reductions (AMRE = 0.24), under existing (local) resource management
practices. Long term (10 years) root zone salt build ups and associated rice/wheat crop yield reductions, in a salt affected
farmer’s field, under varied conjunctive water use scenarios were evaluated with the validated DSS. It was observed that long-term
applications of canal (CW) and tube well (TW) waters in a cycle and in 1:1 mixed mode, during Kharif season, predicted higher average root zone salt reductions (2–9%) and lower rice crop yield reductions (4–5%) than the existing
practice of 3-CW, 3-TW, 3-CW. Besides this, long-term application of 75% CW mixed with 25% TW, during Rabi season, predicted about 17% lower average root-zone salt reductions than the cyclic applications of (1-CW, 1-TW, 2-CW) and
(2-CW, 1-TW, 1-CW, i.e., existing irrigation strategy). However, average wheat crop yield reductions (16–17%) simulated under
all these strategies were almost at par. In general, cyclic-conjunctive water use strategies emerged as better options than
the blending modes. These results were in complete confirmation with actual long-term conjunctive water use experiments on
similar soils. It was thus observed that such pre-validated tools could be efficient means for designing, local resource and
target crop yield-specific, appropriate conjunctive water use plans for irrigated agricultural lands. 相似文献
589.
Brima EI Jenkins RO Lythgoe PR Gault AG Polya DA Haris PI 《Journal of environmental monitoring : JEM》2007,9(1):98-103
Millions of people in some of the poorest regions of the world are exposed to high levels of arsenic through drinking contaminated water. It has been reported that development of cancer caused by arsenic exposure in such populations is dependent on dietary and nutritional factors which can modulate arsenic metabolism. Many people in arsenic exposed regions of Bangladesh and India practice fasting for at least one month every year when they refrain from consumption of food and fluid during daylight hours. How such practices may modulate arsenic metabolism has not been previously investigated. This study investigated this issue by determining total arsenic and its species in urine samples from a group of 29 unexposed volunteers at the beginning of the fasting and at the end of approximately 12 h of fasting period. Inductively coupled plasma mass spectrometry (ICP-MS) and high performance liquid chromatography (HPLC) coupled with ICP-MS was used to measure the total arsenic and arsenic speciation in the urine samples, respectively. The mean total levels of arsenic at the beginning of fasting (18.3 microg g(-1) creatinine) and at the end of approximately 12 h of fasting (17.7 microg g(-1) creatinine) did not differ significantly (p > 0.05). However, the percentages of urinary arsenic as the methylated arsenic species methylarsonate (MA) were found to be significantly different (p < 0.05) and this species was observed more frequently at the end of fasting, although its overall concentration was similar. There were no significant differences (p > 0.05) in both the concentrations and percentages of other urinary arsenic species detected, namely arsenobetaine (AB) and dimethylarsinate (DMA). Arsenite (As(III)) and arsenate (As(V)) were also analyzed, but were not detected. We conclude that fasting for a period of 12 h results in a significant increase in the percentage of urinary arsenic as MA, and its frequency of detection in the volunteers at the end of the fasting period is almost nine fold higher. This suggests that metabolism of arsenic is altered by fasting. 相似文献
590.
The environmental behaviour of polychlorinated phenols and its relevance to cork forest ecosystems: a review 总被引:1,自引:0,他引:1
McLellan I Carvalho M Silva Pereira C Hursthouse A Morrison C Tatner P Martins I San Romão MV Leitão M 《Journal of environmental monitoring : JEM》2007,9(10):1055-1063
Pentachlorophenol (PCP) has been used as a herbicide, biocide and preservative worldwide since the 1930s and as a result, extensive and prolonged contamination exists. The environmental impact increases when its many degradation products are taken into consideration. A number of chloroanisols and their related chlorophenols have been found in cork slabs collected from Portuguese oak tree forests before stopper manufacturing, and contamination by PCP and polychlorinated anisole (PCA) has been detected in Canadian forests. It is suggested that the use of polychlorinated phenols, in particular PCP, is thought to be a cause of the cork taint problem in wine, a major socio-economic impact not only for industry but on sensitive and highly biodiverse ecosystems. It also highlights particular issues relating to the regional regulation of potentially toxic chemicals and global economics world wide. To fully understand the impact of contamination sources, the mechanisms responsible for the fate and transport of PCP and its degradation products and assessment of their environmental behaviour is required. This review looks at the current state of knowledge of soil sorption, fate and bioavailability and identifies the challenges of degradation product identification and the contradictory evidence from field and laboratory observations. The need for a systematic evaluation of PCP contamination in relation to cork forest ecosystems and transfer of PCP between trophic levels is emphasised by discrepancies in bioaccumulation and toxicity. This is essential to enable long term management of not only transboundary contaminants, but also the sustainable management of socially and economically important forest ecosystems. 相似文献