全文获取类型
收费全文 | 18830篇 |
免费 | 211篇 |
国内免费 | 165篇 |
专业分类
安全科学 | 526篇 |
废物处理 | 590篇 |
环保管理 | 3017篇 |
综合类 | 3903篇 |
基础理论 | 5198篇 |
环境理论 | 7篇 |
污染及防治 | 4335篇 |
评价与监测 | 910篇 |
社会与环境 | 621篇 |
灾害及防治 | 99篇 |
出版年
2018年 | 283篇 |
2017年 | 291篇 |
2016年 | 429篇 |
2015年 | 251篇 |
2014年 | 257篇 |
2013年 | 1227篇 |
2012年 | 811篇 |
2011年 | 760篇 |
2010年 | 438篇 |
2009年 | 546篇 |
2008年 | 634篇 |
2007年 | 663篇 |
2006年 | 602篇 |
2005年 | 973篇 |
2004年 | 1131篇 |
2003年 | 1033篇 |
2002年 | 444篇 |
2001年 | 551篇 |
2000年 | 379篇 |
1999年 | 261篇 |
1998年 | 198篇 |
1997年 | 175篇 |
1996年 | 213篇 |
1995年 | 228篇 |
1994年 | 235篇 |
1993年 | 221篇 |
1992年 | 220篇 |
1991年 | 200篇 |
1990年 | 233篇 |
1989年 | 212篇 |
1988年 | 187篇 |
1987年 | 177篇 |
1986年 | 165篇 |
1985年 | 191篇 |
1984年 | 166篇 |
1983年 | 180篇 |
1982年 | 191篇 |
1981年 | 193篇 |
1980年 | 176篇 |
1979年 | 165篇 |
1978年 | 164篇 |
1977年 | 140篇 |
1976年 | 143篇 |
1975年 | 121篇 |
1974年 | 151篇 |
1973年 | 131篇 |
1972年 | 136篇 |
1971年 | 111篇 |
1970年 | 109篇 |
1967年 | 116篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
751.
S. J. Herrmann J. A. Turner J. S. Carsella D. W. Lehmpuhl D. R. Nimmo 《Environmental management》2012,50(6):1111-1124
Aquatic bryophytes, Hygrohypnum ochraceum, were deployed “in situ” at 14 sites in the Fountain Creek Watershed, spring and fall, 2007 to study selenium (Se) accumulation. Dissolved, total, and pore (sediment derived) water samples were collected and water quality parameters determined while plants were exposed to the water for 10?days. There was a trend showing plant tissue-Se uptake with distance downstream and we found a strong correlation between Se in the water with total hardness in both seasons. There was a modest association between Se-uptake in plants with hardness in the spring of 2007 but not the fall. Plants bioconcentrated Se from the water by a factor of 5.8?×?103 at Green Mountain Falls and 1.5?×?104 at Manitou Springs in the fall of 2007. Both are examples of the bioconcentration abilities of the plants, primarily in the upper reaches of the watershed where bioconcentration factors were highest. However, the mean minima and maxima of Se in the plants in each of the three watershed segments appeared similar during both seasons. We found direct relationships between the pore and dissolved Se in water in the spring (R 2?=?0.84) and fall (R 2?=?0.95) and dissolved Se and total hardness in the spring and fall (R 2?=?0.92). The data indicate that H. ochraceum was a suitable indicator of Se bioavailability and Se uptake in other trophic levels in the Fountain Creek Watershed based on a subsequent study of Se accumulation in fish tissues at all 14 sites. 相似文献
752.
Simulating Land-Cover Change in Montane Mainland Southeast Asia 总被引:6,自引:0,他引:6
We used the conversion of land use and its effects (CLUE-s) model to simulate scenarios of land-cover change in Montane mainland
southeast Asia (MMSEA), a region in the midst of transformation due to rapid intensification of agriculture and expansion
of regional trade markets. Simulated changes affected approximately 10 % of the MMSEA landscape between 2001 and 2025 and
16 % between 2001 and 2050. Roughly 9 % of the current vegetation, which consists of native species of trees, shrubs, and
grasses, is projected to be replaced by tree plantations, tea, and other evergreen shrubs during the 50 years period. Importantly,
4 % of this transition is expected to be due to the expansion of rubber (Hevea brasiliensis), a tree plantation crop that may have important implications for local-to-regional scale hydrology because of its potentially
high water consumption in the dry season. 相似文献
753.
Organic Farming Benefits Local Plant Diversity in Vineyard Farms Located in Intensive Agricultural Landscapes 总被引:1,自引:0,他引:1
The majority of research on organic farming has considered arable and grassland farming systems in Central and Northern Europe,
whilst only a few studies have been carried out in Mediterranean agro-systems, such as vineyards, despite their economic importance.
The main aim of the study was to test whether organic farming enhances local plant species richness in both crop and non-crop
areas of vineyard farms located in intensive conventional landscapes. Nine conventional and nine organic farms were selected
in an intensively cultivated region (i.e. no gradient in landscape composition) in northern Italy. In each farm, vascular
plants were sampled in one vineyard and in two non-crop linear habitats, grass strips and hedgerows, adjacent to vineyards
and therefore potentially influenced by farming. We used linear mixed models to test the effect of farming, and species longevity
(annual vs. perennial) separately for the three habitat types. In our intensive agricultural landscapes organic farming promoted
local plant species richness in vineyard fields, and grassland strips while we found no effect for linear hedgerows. Differences
in species richness were not associated to differences in species composition, indicating that similar plant communities were
hosted in vineyard farms independently of the management type. This negative effect of conventional farming was probably due
to the use of herbicides, while mechanical operations and mowing regime did not differ between organic and conventional farms.
In grassland strips, and only marginally in vineyards, we found that the positive effect of organic farming was more pronounced
for perennial than annual species. 相似文献
754.
In many regions of the world, fires are primarily of anthropogenic origin. In northwestern Patagonia, the number of fires
is not correlated with meteorological variables, but is concentrated in urban areas. This study was conducted in the wildland–urban
interface (WUI) area of San Carlos de Bariloche (Patagonia, Argentina), within the Nahuel Huapi National Park. WUI fires are
particularly problematic because, besides people and goods, they represent a danger to protected areas. We studied the relationship
between fire records and socioeconomic indicators within the WUI of San Carlos de Bariloche. We conducted a Multiple Correspondence
Factorial Analysis and an Ascendant Hierarchical Classification of the city neighborhoods. The results show that the neighborhoods
in Bariloche can be divided into three classes: High Socioeconomic Fire Risk neighborhoods, including neighborhoods with the
highest fire rates, where people have low instruction level, high levels of unsatisfied basic needs and high unemployment
levels; Low Socioeconomic Fire Risk neighborhoods, that groups neighborhoods which present the opposite characterization,
and Moderate Socioeconomic Fire Risk neighborhoods, which are more heterogeneous. Once neighborhoods were classified, a Socioeconomic
Fire Risk map was generated, supplementing the existing WUI Fire Danger map. Our results emphasize the relevance of socioeconomic
variables to fire policies. 相似文献
755.
Farm Crops Depredation by European Bison (Bison bonasus) in the Vicinity of Forest Habitats in Northeastern Poland 总被引:1,自引:0,他引:1
European bison, the largest mammal in Europe, after being exterminated in the wild and then restored during the 20th century is still listed by the International Union for Conservation of Nature (IUCN Red List of Threatened Species) as a species vulnerable to extinction. However, the increasing number of European bison, through creation of new and expansion of existing populations strongly increases the risk of human-bison conflict in the near future. We analyzed the depredation of farm crops by bison and the factors influencing the level of damage in the vicinity of two forest areas inhabited by bison in northeastern Poland. Between 2000 and 2010, the total cost of compensation was 196,200. The level of damage and amount of compensation was increasing from year to year in both forests and correlated with the number of bison. The majority of damage (57?% of cases) was recorded in winter (December-March). Snow depth and temperature did not influence the frequency of damage. The incidences of damage increased with decreasing distance from the woodland patches, therefore, 69?% of cases in Bia?owie?a Forest, and 80?% in Knyszyn Forest were recorded closer than 0.5?km from nearest woodland patch. The majority of the crops damaged by bison were cereals (61?%) but also hay (20?%) and rape (13?%). When compared to the availability of crops, bison strongly selected rape and rye in both regions. This study is the first addressing the increasing problem of human-bison conflict in re-introduced populations and analyzing long-term data on crop depredation. Such situations probably occur in the majority of growing and expanding bison populations, however, it has not yet to be monitored and is rather neglected in post-Soviet countries. 相似文献
756.
The present study aims to identify the potential habitat for swamp deer (Cervus duvauceli duvauceli Cuvier) in Jhilmil Jheel Conservation Reserve in the Uttarakhand province of India using multi-criteria analysis. The study
area represents one of the last remnant habitats of the flagship species, the swamp deer in Uttarakhand, which is considered
as vulnerable. The study showed that only 6.08% of the study area (225 km2) was highly suitable to suitable for the swamp deer. An area of 135.52 km2 (60.23%) turned out to be moderately suitable. Within the officially designated Conservation Reserve (area 37.84 km2), 10.91% (4.13 km2) area was found highly suitable to suitable, while 74.19% (28.07 km2) happens to be moderately suitable. Only 14 km2 area, which was found as suitable habitat for swamp deer falls short of the space required by a population of 134 animals.
The problem could be mitigated if the agricultural land (2.47 km2) adjacent to the Jhilmil Jheel is brought under the Reserve management. This would provide additional area to meet the fodder
requirement. The study brings out a particularly grim situation with limited options for conservation and management of the
swamp deer in the Indo-Gangetic plains. It also emphasizes the role of geospatial techniques in quick appraisal of habitat
attributes and identification of potential sites for protected areas. 相似文献
757.
The study investigated vegetative and soil properties in four created mitigation wetlands, ranging in age from three to ten
years, all created in the Virginia Piedmont. Vegetation attributes included percent cover, richness (S), diversity (H′), floristic
quality assessment index (FQAI), prevalence index (PI), and productivity [i.e., peak above-ground biomass (AGB) and below-ground
biomass]. Soil attributes included soil organic matter (SOM), gravimetric soil moisture (GSM), pH, and bulk density (Db) for the top 10 cm. Species dominance (e.g., Juncus effusus, Scirpus cyperinus, Arthraxon hispidus) led to a lack of differences in vegetative attributes between sites. However, site-based differences were found for GSM,
pH, and SOM (P < 0.001). Soil attributes were analyzed using Euclidean cluster analysis, resulting in four soil condition (SC) categories
where plots were grouped based on common attribute levels (i.e., SC1 > SC2 > SC3 > SC4, trended more to less developed). When
vegetation attributes were compared between SC groups, greater SOM, lower Db, more circumneutral pH, and higher GSM, all indicative of maturation, were associated with higher H′ (P < 0.05), FQAI (P < 0.05), and total and volunteer percent cover (P < 0.05), and lower AGB (P < 0.001), PI (P < 0.05), and seeded percent cover (P < 0.05). The outcome of the study shows that site age does not necessarily equate with site development with soil and vegetation
developmental rates varying both within and among sites. The inclusion of soil attributes in post-construction monitoring
should be required to enhance our understanding and prediction of developmental trajectory of created mitigation wetlands. 相似文献
758.
Groninger JW 《Environmental management》2012,49(4):833-845
Foreign and domestic government agencies and other international organizations pursue reforestation programs in rural upper
watershed areas of Afghanistan over the past decade to alleviate poverty, combat the insurgency and rehabilitate a depleted
forest resource base. Popular programs incorporate cash-for-work to conduct hillside terracing, check dam construction and
tree-planting for nut production, fuel wood, timber, dune stabilization, and erosion abatement. Programmatic approaches have
varied as a function of accessibility, security and local objectives. Uncertain land tenure and use rights, weak local environmental
management capacity, and a focus on agricultural production to meet immediate needs limit interest, nationally and locally.
Unreliable security, a lack of high quality tree planting stock, limited technical knowledge and coordination among government
agencies, and poor security hamper program expansion. Reforestation success would be most likely where these issues are least
acute. The Afghan government should focus on supporting community based natural resource management, developing and disseminating
improved conservation tree nursery strategies, and promoting watershed management schemes that incorporate forestry, range
management and agronomic production. Reforestation practitioners could benefit from the human and material resources now present
as part of the international war effort. Successes and failures encountered in Afghanistan should be considered in order to
address similar problems in insecure regions elsewhere when reforestation may help reverse environmental degradation and contribute
to broader social stabilization efforts. 相似文献
759.
Relationships Between Nitrogen Transformation Rates and Gene Abundance in a Riparian Buffer Soil 总被引:1,自引:0,他引:1
Lin Wu Deanna L. Osmond Alexandria K. Graves Michael R. Burchell Owen W. Duckworth 《Environmental management》2012,50(5):861-874
Denitrification is a critical biogeochemical process that results in the conversion of nitrate to volatile products, and thus is a major route of nitrogen loss from terrestrial environments. Riparian buffers are an important management tool that is widely utilized to protect water from non-point source pollution. However, riparian buffers vary in their nitrate removal effectiveness, and thus there is a need for mechanistic studies to explore nitrate dynamics in buffer soils. The objectives of this study were to examine the influence of specific types of soluble organic matter on nitrate loss and nitrous oxide production rates, and to elucidate the relationships between these rates and the abundances of functional genes in a riparian buffer soil. Continuous-flow soil column experiments were performed to investigate the effect of three types of soluble organic matter (citric acid, alginic acid, and Suwannee River dissolved organic carbon) on rates of nitrate loss and nitrous oxide production. We found that nitrate loss rates increased as citric acid concentrations increased; however, rates of nitrate loss were weakly affected or not affected by the addition of the other types of organic matter. In all experiments, rates of nitrous oxide production mirrored nitrate loss rates. In addition, quantitative polymerase chain reaction (qPCR) was utilized to quantify the number of genes known to encode enzymes that catalyze nitrite reduction (i.e., nirS and nirK) in soil that was collected at the conclusion of column experiments. Nitrate loss and nitrous oxide production rates trended with copy numbers of both nir and 16s rDNA genes. The results suggest that low-molecular mass organic species are more effective at promoting nitrogen transformations than large biopolymers or humic substances, and also help to link genetic potential to chemical reactivity. 相似文献
760.
Nutrient removal in tropical subsurface flow constructed wetlands under batch and continuous flow conditions 总被引:1,自引:0,他引:1
Zhang DQ Tan SK Gersberg RM Zhu J Sadreddini S Li Y 《Journal of environmental management》2012,96(1):1-6
The aim of this investigation was to evaluate the influence of batch versus continuous flow on the removal efficiencies of chemical oxygen demand (COD), nitrogen (N) and total phosphorus (TP) in tropical subsurface flow constructed wetlands (SSF CW). The quantitative role of the higher aquatic plants in nutrient removal in these two operational modes was also investigated. Results indicated no significant difference (p > 0.05) in COD removal between batch and continuous flow modes for either the planted or unplanted treatments. Furthermore, the batch-loaded planted wetlands showed significantly (p < 0.05) higher ammonium removal efficiencies (95.2%) compared with the continuously fed systems (80.4%), most probably because the drain and fill batch mode presented systematically more oxidized environmental conditions. With respect to TP removal, for both planted and unplanted beds, there was significant enhancement (p < 0.05) in batch flow operation (69.6% for planted beds; 39.1% for unplanted beds) as compared to continuous flow operation (46.8% for planted beds; 25.5% for unplanted beds). In addition, at a 4-day hydraulic retention time (HRT), the presence of plants significantly enhanced both ammonia oxidation and TP removal in both batch and continuous modes of operation as compared to that for unplanted beds. An estimation of the quantitative role of aeration from drain and fill operation at a 4-day HRT, as compared to rhizosphere aeration by the higher aquatic plant, indicated that drain and fill operation might account for only less than half of the higher aquatic plant's quantitative contribution of oxygen (1.55 g O2 per m2 per day for batch flow versus 1.13 g O2 per m2 per day for continuous flow). 相似文献