全文获取类型
收费全文 | 19070篇 |
免费 | 172篇 |
国内免费 | 140篇 |
专业分类
安全科学 | 368篇 |
废物处理 | 750篇 |
环保管理 | 1962篇 |
综合类 | 5054篇 |
基础理论 | 4258篇 |
环境理论 | 10篇 |
污染及防治 | 4633篇 |
评价与监测 | 1167篇 |
社会与环境 | 1123篇 |
灾害及防治 | 57篇 |
出版年
2022年 | 144篇 |
2021年 | 148篇 |
2019年 | 126篇 |
2018年 | 250篇 |
2017年 | 232篇 |
2016年 | 373篇 |
2015年 | 290篇 |
2014年 | 439篇 |
2013年 | 1224篇 |
2012年 | 499篇 |
2011年 | 689篇 |
2010年 | 570篇 |
2009年 | 650篇 |
2008年 | 736篇 |
2007年 | 798篇 |
2006年 | 695篇 |
2005年 | 581篇 |
2004年 | 600篇 |
2003年 | 602篇 |
2002年 | 556篇 |
2001年 | 677篇 |
2000年 | 463篇 |
1999年 | 347篇 |
1998年 | 228篇 |
1997年 | 249篇 |
1996年 | 248篇 |
1995年 | 270篇 |
1994年 | 267篇 |
1993年 | 239篇 |
1992年 | 211篇 |
1991年 | 238篇 |
1990年 | 225篇 |
1989年 | 190篇 |
1988年 | 190篇 |
1987年 | 168篇 |
1986年 | 167篇 |
1985年 | 174篇 |
1984年 | 187篇 |
1983年 | 176篇 |
1982年 | 194篇 |
1981年 | 157篇 |
1980年 | 151篇 |
1979年 | 155篇 |
1978年 | 156篇 |
1977年 | 136篇 |
1974年 | 128篇 |
1967年 | 145篇 |
1964年 | 124篇 |
1963年 | 126篇 |
1957年 | 124篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Charles D. Ikenberry William G. Crumpton Jeffrey G. Arnold Michelle L. Soupir Philip W. Gassman 《Journal of the American Water Resources Association》2017,53(6):1267-1280
The ability to accurately simulate flow and nutrient removal in treatment wetlands within an agricultural, watershed‐scale model is needed to develop effective plans for meeting nutrient reduction goals associated with protection of drinking water supplies and reduction of the Gulf of Mexico hypoxic zone. The objectives of this study were to incorporate new equations for wetland hydrology and nutrient removal in Soil and Water Assessment Tool (SWAT), compare model performance using original and improved equations, and evaluate the ramifications of errors in watershed and tile drain simulation on prediction of NO3‐N dynamics in wetlands. The modified equations produced Nash‐Sutcliffe Efficiency values of 0.88 to 0.99 for daily NO3‐N load predictions, and percent bias values generally less than 6%. However, statistical improvement over the original equations was marginal and both old and new equations provided accurate simulations. The new equations reduce the model's dependence on detailed monitoring data and hydrologic calibration. Additionally, the modified equations increase SWAT's versatility by incorporating a weir equation and an irreducible nutrient concentration and temperature coefficient. Model improvements enhance the utility of SWAT for simulating flow and nutrients in wetlands and other impoundments, although performance is limited by the accuracy of inflow and NO3‐N predictions from the contributing watershed. Editor's note : This paper is part of the featured series on SWAT Applications for Emerging Hydrologic and Water Quality Challenges. See the February 2017 issue for the introduction and background to the series. 相似文献
982.
983.
Hariz Islas-Flores Leobardo Manuel Gómez-Oliván Marcela Galar-Martínez Sandra García-Medina Nadia Neri-Cruz Octavio Dublán-García 《Environmental science and pollution research international》2014,21(7):5157-5166
Although trace concentrations of ibuprofen (IBP) have been detected in diverse water bodies, there is currently insufficient information on the potentially deleterious effects of this xenobiotic. The present study aimed to determine whether IBP induces oxidative stress in brain, liver, gill, and blood of the common carp Cyprinus carpio. To this end, the median lethal concentration at 96 h (96-h LC50) was determined and the lowest observed adverse effect level was established. Carp were exposed to the latter concentration (17.6 mg L?1) for 12, 24, 48, 72, and 96 h, and the following biomarkers were evaluated: lipid peroxidation (LPX) and activity of the antioxidant enzymes superoxide dismutase, catalase, and glutathione peroxidase. Results indicated that LPX and antioxidant enzymes’ activity increased significantly (p?<?0.05) with respect to the control group in liver, gill, and blood, while no significant differences occurred in brain. In conclusion, IBP induced oxidative stress on C. carpio, the liver being the organ most affected by this damage. 相似文献
984.
Comparing Costs of Onsite Best Management Practices to Nutrient Credits for Stormwater Management: A Case Study in Virginia 下载免费PDF全文
Alicia L. Nobles Jonathan L. Goodall G. Michael Fitch 《Journal of the American Water Resources Association》2017,53(1):131-143
Best management practices (BMPs) are widely used to mitigate impacts of increased impervious surfaces on stormwater runoff. However, there is limited detailed and up‐to‐date information available on the cost of designing, constructing, and maintaining BMPs over their lifetime. The objective of this study is to analyze BMPs recently constructed by the Virginia Department of Transportation (VDOT) to quantify their total cost per pound of phosphorus removed annually. A motivating factor for the study is recent changes to regulatory guidelines in Virginia which allow for full or partial substitution of purchased nutrient credits in lieu of constructing onsite BMPs to achieve compliance with stormwater quality regulations. Results of the analysis of nine BMPs found their cost ranged from $20,100 to $74,900, in 2014 dollars, per pound ($44,313‐$165,126 per kg) of phosphorus removed. Based on these results and assuming current credit prices procured by VDOT, purchasing nutrient credits is a cost‐effective option for the agency, especially when factoring in the cost of additional right of way for the BMP. Based on this finding, we expect compliance with stormwater quality regulations through credit purchases to become more widely used in Virginia. Moving forward, we suggest more direct tracking of BMP costs to support comparisons between BMP costs across a range of types and conditions to credit purchases for meeting stormwater regulations. 相似文献
985.
Beverly Z.L. Oh Ana M.M. Sequeira Mark G. Meekan Jonathan L.W. Ruppert Jessica J. Meeuwig 《Conservation biology》2017,31(3):635-645
Fishing and habitat degradation have increased the extinction risk of sharks, and conservation strategies recognize that survival of juveniles is critical for the effective management of shark populations. Despite the rapid expansion of marine protected areas (MPAs) globally, the paucity of shark‐monitoring data on large scales (100s–1000s km) means that the effectiveness of MPAs in halting shark declines remains unclear. Using data collected by baited remote underwater video systems (BRUVS) in northwestern Australia, we developed generalized linear models to elucidate the ecological drivers of habitat suitability for juvenile sharks. We assessed occurrence patterns at the order and species levels. We included all juvenile sharks sampled and the 3 most abundant species sampled separately (grey reef [Carcharhinus amblyrhynchos], sandbar [Carcharhinus plumbeus], and whitetip reef sharks [Triaenodon obesus]). We predicted the occurrence of juvenile sharks across 490,515 km2 of coastal waters and quantified the representation of highly suitable habitats within MPAs. Our species‐level models had higher accuracy (? ≥ 0.69) and deviance explained (≥48%) than our order‐level model (? = 0.36 and deviance explained of 10%). Maps of predicted occurrence revealed different species‐specific patterns of highly suitable habitat. These differences likely reflect different physiological or resource requirements between individual species and validate concerns over the utility of conservation targets based on aggregate species groups as opposed to a species‐focused approach. Highly suitable habitats were poorly represented in MPAs with the most restrictions on extractive activities. This spatial mismatch possibly indicates a lack of explicit conservation targets and information on species distribution during the planning process. Non‐extractive BRUVS provided a useful platform for building the suitability models across large scales to assist conservation planning across multiple maritime jurisdictions, and our approach provides a simple for method for testing the effectiveness of MPAs. 相似文献
986.
987.
While local food production may be beneficial in terms of developing the local economy and reducing greenhouse gases from transportation, sustainability strategies focused on local food production may generate their own risks due to yield variability. We have developed a robust optimization (RO) model to determine the minimum amount of land (cropland and pasture) required to grow food items that would satisfy a local population’s (accounting for gender and age) calorie and nutrient needs. This model has been applied to Boone County, Missouri, which has a population of approximately 170,000. Boone County is 1790 km2, with 16% of the land defined as cropland and 30% defined as pasture. The model includes 27 nutrients from 17 potential foods that could be produced: six fruits and vegetables, five grains and six animal-sourced foods. Yield estimates are based on the predominate methods of agriculture in the USA. We first run our model assuming no variability, using the midpoint yield estimates. Then, to quantify uncertainty in yield for different food types, we use historical yield data over 10 years to estimate this variability and run our RO model under these variability estimates. We compare the two model results to illustrate the impact of data uncertainty on meeting sustainable local food for communities. Solutions suggest that nutrition needs can be met for the Boone County population within the land area defined. 相似文献
988.
G.L. Sivakumar Babu Krishna R. Reddy Sandeep K. Chouksey 《Waste management (New York, N.Y.)》2010,30(1):11-22
A constitutive model is proposed to describe the stress–strain behavior of municipal solid waste (MSW) under loading using the critical state soil mechanics framework. The modified cam clay model is extended to incorporate the effects of mechanical creep and time dependent biodegradation to calculate total compression under loading. Model parameters are evaluated based on one-dimensional compression and triaxial consolidated undrained test series conducted on three types of MSW: (a) fresh MSW obtained from working phase of a landfill, (b) landfilled waste retrieved from a landfill after 1.5 years of degradation, and (c) synthetic MSW with controlled composition. The model captures the stress–strain and pore water pressure response of these three types of MSW adequately. The model is useful for assessing the deformation and stability of landfills and any post-closure development structures located on landfills. 相似文献
989.
G. Pecl 《Marine Biology》2001,138(1):93-101
A major difficulty confronting the determination of cephalopod reproductive life history is assessing over what portion of
the life span an individual is reproductively mature and actively depositing eggs. This paper assesses the potential of the
tropical Sepioteuthis lessoniana and two genetic types of the temperate Sepioteuthis australis, to spawn multiple batches of eggs at discrete times throughout the adult life span. This is achieved by histological examination
of the ovarian gametogenic cycle and detailed morphological assessments of the reproductive system, in conjunction with other
biological information. The genetic type of S. australis found at the northern limits of its Australian distribution showed evidence of a high correlation between body size and quantity
of mature eggs, suggesting that eggs may be accumulating to be laid in a single batch. Although maturation was also a size-related
process in S. lessoniana and Tasmanian S. australis, oviduct size was not correlated with body weight in mature females, which is indicative of multiple spawning. Further supporting
evidence includes relatively low gonadosomatic indices, the heavier weight of the ovary relative to the oviduct, and the feeding
activity of mature animals. Mature S. lessoniana and S. australis individuals were present at each location over very wide age and size ranges. In Tasmanian waters, there were distinct seasonal
differences in the reproductive biology of S. australis. Summer-caught individuals had much higher gonadosomatic indices and may have been laying larger batches of eggs compared
with winter-caught individuals. Summer-caught females also showed a negative correlation between egg size and egg number within
the oviduct, suggesting that some individuals were producing fewer, larger eggs and others many smaller eggs. Evidence suggests
that considerable flexibility is inherent in the reproductive strategy of both S. lessoniana and S. australis.
Received: 11 May 2000 / Accepted: 12 September 2000 相似文献
990.
G. Grueiro-Noche S. Muniategui-Lorenzo D. Prada-Rodríguez 《Environmental pollution (Barking, Essex : 1987)》2010,158(1):207-91
In November 2002 the oil tanker ‘Prestige’ released 65 000 tons of a heavy fuel oil throughout the Galician coastline (NW Spain), causing extensive damage to marine life, natural resources and economic activities at Northern Portugal, Spain and SW France. To evaluate the impact of the oil spill on the aquatic system, 30 polycyclic aromatic hydrocarbons (PAHs), including alkylated derivatives, were analyzed in seawater on five different sampling campaigns from 2002 to 2004. Sampling was made along the Galician continental shelf. In each station three samples were collected at three different depths (surface, mid-depth and bottom). Four different approaches for 3-way analyses (Catenated-PCA, Matrix-Augmented Principal Components Analysis, Parallel Factor Analysis and Procrustes rotation) have been used to asses the major sources of PAHs into the seawater. They revealed two main pollution patterns: one related to oil spillages and discharge of petroleum products, and another more associated with a diffuse anthropogenic origin. 相似文献