全文获取类型
收费全文 | 4119篇 |
免费 | 75篇 |
国内免费 | 51篇 |
专业分类
安全科学 | 251篇 |
废物处理 | 153篇 |
环保管理 | 862篇 |
综合类 | 477篇 |
基础理论 | 1023篇 |
环境理论 | 3篇 |
污染及防治 | 956篇 |
评价与监测 | 313篇 |
社会与环境 | 166篇 |
灾害及防治 | 41篇 |
出版年
2024年 | 11篇 |
2023年 | 35篇 |
2022年 | 45篇 |
2021年 | 55篇 |
2020年 | 68篇 |
2019年 | 83篇 |
2018年 | 85篇 |
2017年 | 124篇 |
2016年 | 144篇 |
2015年 | 109篇 |
2014年 | 134篇 |
2013年 | 351篇 |
2012年 | 185篇 |
2011年 | 236篇 |
2010年 | 182篇 |
2009年 | 203篇 |
2008年 | 210篇 |
2007年 | 222篇 |
2006年 | 205篇 |
2005年 | 178篇 |
2004年 | 157篇 |
2003年 | 138篇 |
2002年 | 136篇 |
2001年 | 97篇 |
2000年 | 69篇 |
1999年 | 63篇 |
1998年 | 48篇 |
1997年 | 64篇 |
1996年 | 50篇 |
1995年 | 54篇 |
1994年 | 56篇 |
1993年 | 46篇 |
1992年 | 39篇 |
1991年 | 31篇 |
1990年 | 29篇 |
1989年 | 27篇 |
1988年 | 23篇 |
1987年 | 17篇 |
1986年 | 17篇 |
1985年 | 23篇 |
1984年 | 18篇 |
1983年 | 28篇 |
1982年 | 22篇 |
1981年 | 32篇 |
1980年 | 19篇 |
1979年 | 18篇 |
1978年 | 13篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1975年 | 5篇 |
排序方式: 共有4245条查询结果,搜索用时 15 毫秒
201.
The first prenatal diagnosis of Pallister-Killian syndrome by chorionic villus sampling is presented. Fetal hydrops was noted on ultrasound in early pregnancy, and the karyotype revealed isochromosome 12p mosaicism. 相似文献
202.
Cena LG Keren N Li W Carriquiry AL Pawlovich MD Freeman SA 《Journal of Safety Research》2011,42(4):241-252
Introduction
A common contention is that the construction of highway bypasses negatively impacts the economy of local communities by reducing pass-by traffic for businesses. However, as access to specific business' account records is limited, this impact is difficult to quantify. Another common contention is that bypasses contribute to a reduction in overall crashes in the community and in the surrounding areas. Even though a large number of bypasses have been constructed in the State of Iowa over the past several years, their actual impact in terms of traffic safety has not been quantified.Objectives
This study seeks answers to the following questions: (a) Are bypasses in Iowa associated with a reduction in crash frequencies and crash rates on the bypassed highway? (b) Do bypasses in Iowa introduce a reduction of overall crash frequencies and rates or do they merely shift crashes from the highways through the communities to the bypasses with no significant overall reduction?Method
We obtained crash information from the Iowa DOT at 19 sites on which a bypass was constructed sometime during the past 23 years. We also obtained the same information at six sites used as comparison sites on which no bypasses were constructed at least until 2005. We them employed a Bayesian approach to estimating the association between the construction of the bypass and crash rates, while also accounting for other factors.Results
The construction of bypasses in Iowa is associated with a significant increase in traffic safety both on the main road through town and on the combined main road and bypass roadway. 相似文献203.
Michael B. Lester Charles van Riper III 《Environmental monitoring and assessment》2014,186(8):4779-4791
Heavy metals are persistent environmental contaminants, and transport of metals into the environment poses a threat to ecosystems, as plants and wildlife are susceptible to long-term exposure, bioaccumulation, and potential toxicity. We investigated the distribution and cascading extent of heavy metal accumulation in southwestern song sparrows (Melospiza melodia fallax), a resident riparian bird species that occurs along the US/Mexico border in Arizona’s upper Santa Cruz River watershed. This study had three goals: (1) quantify the degree of heavy metal accumulation in sparrows and determine the distributional patterns among study sites, (2) compare concentrations of metals found in this study to those found in studies performed prior to a 2009 international wastewater facility upgrade, and (3) assess the condition of song sparrows among sites with differing potential levels of exposure. We examined five study sites along with a reference site that reflect different potential sources of contamination. Body mass residuals and leukocyte counts were used to assess sparrow condition. Birds at our study sites typically had higher metal concentrations than birds at the reference site. Copper, mercury, nickel, and selenium in song sparrows did exceed background levels, although most metals were below background concentrations determined from previous studies. Song sparrows generally showed lower heavy metal concentrations compared to studies conducted prior to the 2009 wastewater facility upgrade. We found no cascading effects as a result of metal exposure. 相似文献
204.
Anastasis Christou Elena Eliadou Costas Michael Evroula Hapeshi Despo Fatta-Kassinos 《Environmental monitoring and assessment》2014,186(8):4857-4870
An extensive field survey was employed for assessing the impacts of long-term wastewater irrigation of forage crops and orange orchards in three suburban agricultural areas in Cyprus (areas I, II, and III), as compared to rainfed agriculture, on the soil geochemical properties and the bioaccumulation of heavy metals (Zn, Ni, Mn, Cu, Co) to the agricultural products. Both ryegrass fields and orange orchards in areas I and II were continuously wastewater irrigated for 10 years, whereas clover fields in area III for 0.5, 4, and 8 years. The results revealed that wastewater reuse for irrigation caused a slight increase in soil salinity and Cl? content in areas I and II, and a remarkable increase, having strong correlation with the period in which wastewater irrigation was practiced, in area III. Soil salinization in area III was due to the high electrical conductivity (EC) of the wastewater applied for irrigation, attributed to the influx of seawater to the sewage collection network in area III. In addition, the wastewater irrigation practice resulted in a slight decrease of the soil pH values in area III, while a subtle impact was identified regarding the CaCO3, Fe, and heavy metal content in the three areas surveyed. The heavy metal content quantified in the forage plants’ above-ground parts was below the critical levels of phytotoxicity and the maximum acceptable concentration in dairy feed, whereas heavy metals quantified in orange fruit pulp were below the maximum permissible levels (MPLs). Heavy metal phytoavailability was confined due to soil properties (high pH and clay content), as evidenced by the calculated low transfer factor (TF). 相似文献
205.
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
206.
Michael Saffle 《The Environmentalist》2012,32(3):326-331
In American academic circles, peer-reviewed hard-copy book publishing remains a crucial part of the tenure and promotion process as well as a method of bestowing prestige upon authors accepted by university presses and other mainstream venues. Although a few respected individuals self-published as early as the seventeenth century, the emergence of desktop publishing during the 1980s led to hard-copy and virtual (self-)publishing venues of several kinds, including PDF formatting and the establishment of POD (print on demand) firms. Online, PDF, POD printing, and other challenges to traditional academic publishing can save money and improve efficiency as well as help sustain our forests and other natural resources. 相似文献
207.
Consumers influence climate change through their consumption patterns and their support or dismissal of climate mitigation policy measures. Both climate-friendly actions and policy support comprise a broad range of options, which vary in manifold ways and, therefore, might be influenced by different factors. The aims of the study were, therefore, two-fold: first, we intended to find a meaningful way to classify different ways of addressing climate change. Second, we aimed to examine which determinants influence people's willingness to engage in these behaviors. We conducted a large-scale mail survey in Switzerland in which respondents rated, among other items, their willingness to act or support a range of possible actions and mitigations measures. A principal component analysis indicated that a distinction in terms of a behavior's directness as well as a differentiation according to perceived costs seem to be appropriate to classify climate-friendly actions. Multiple regression analyses showed that perceived costs and perceived climate benefit turned out to be the strongest predictors for willingness to act or to support climate policy measures. The strong influence of perceived climate benefit might reflect a strategy of reducing cognitive dissonance. As high-cost behaviors are more difficult to adopt, consumers may reduce dissonance by dismissing high-cost behaviors as not effective in terms of climate mitigation. Political affiliation proved to be another strong determinant of willingness to act or support. Participants on the right wing were less willing to show indirect climate-friendly behaviors, change their mobility behaviors, and to support any type of climate mitigation policy measures. Climate-friendly low-cost behaviors, however, were not influenced by political affiliation. 相似文献
208.
James A. Stoeckel Jade Morris Elizabeth Ames David C. Glover Michael J. Vanni William Renwick María J. González 《Journal of the American Water Resources Association》2012,48(3):616-634
Stoeckel, James A., Jade Morris, Elizabeth Ames, David C. Glover, Michael J. Vanni, William Renwick, and María J. González, 2012. Exposure Times to the Spring Atrazine Flush Along a Stream-Reservoir System. Journal of the American Water Resources Association (JAWRA) 48(3): 616-634. DOI: 10.1111/j.1752-1688.2011.00633.x Abstract: We used enzyme-linked immunosorbent assay to examine reservoir-mediated shifts in spring to fall exposure of aquatic organisms to the spring atrazine pulse over four years in a Midwestern stream-reservoir system. Peak atrazine concentrations in the major inflowing stream exceeded 10 μg/l in all four years. The reservoir had a beneficial effect in two of four years by diluting atrazine below the 10 μg/l threshold. However, during the other two years, exposure times above 10 μg/l were approximately doubled in the reservoir compared to the major inflowing stream. Thresholds of 3 and 5 μg/l were exceeded during all four years in the reservoir. The uplake and downlake reservoir sites were four to five times more likely to exceed these thresholds and aquatic organisms were subjected to longer exposure times above these thresholds compared to the inflowing stream. Release of elevated atrazine concentrations from the reservoir extended exposure times in the outflowing stream. This effect was most pronounced just below the dam. Aquatic organisms upstream of the reservoir were most likely to experience acute exposures whereas organisms within and immediately downstream of the reservoir were more likely to experience chronic exposures. The ubiquity of reservoirs and the annual spring herbicide flush highlight the importance of considering the presence and relative location of reservoirs when assessing risk to aquatic communities as well as locations of drinking water intakes. 相似文献
209.
Recent levels of organochlorine pesticides and polychlorinated biphenyls in sediments of the sewer system in Hanoi, Vietnam 总被引:2,自引:0,他引:2
Pham Manh Hoai Nguyen Hung Minh Michael Berg Walter Giger 《Environmental pollution (Barking, Essex : 1987)》2010,158(3):913-920
The occurrence, temporal trend, sources and toxicity of PCBs and organochlorine pesticides were investigated in sediment samples from the sewer system of Hanoi City, including the rivers Nhue, To Lich, Lu, Set, Kim Nguu and the Yen So Lake. In general, the concentrations of the pollutants followed the order DDTs > PCBs > HCHs (β-HCH) > HCB. However, the pollution pattern was different for the DDTs and PCBs when the sampling locations were individually evaluated. The concentrations of the DDTs, PCBs, HCHs, and HCB ranged from 4.4 to 1100, 1.3 to 384, <0.2 to 36 and <0.2 to 22 ng/g d.w., respectively. These levels are higher than at any other location in Vietnam. Compared to measurements from 1997, the DDTs, PCBs, β-HCH and HCB levels show an increasing trend with DDT/DDE ratios, indicating very recent inputs into the environment although these persistent compounds are banned in Vietnam since 1995. 相似文献
210.
Johannes Kobler Walter J. Fitz Michael Mirtl 《Environmental pollution (Barking, Essex : 1987)》2010,158(3):849-854
Anthropogenic trace element emissions have declined. However, top soils all over the world remain enriched in trace elements. We investigated Pb and Cd migration in forest soils of a remote monitoring site in the Austrian limestone Alps between 1992 and 2004. Large spatial variability masked temporal changes in the mineral soil of Lithic Leptosols (Skeltic), whereas a significant reduction of Pb concentrations in their forest floors occurred. Reductions of concentrations in the less heterogeneous Cambisols (Chromic) were significant. In contrast, virtually no migration of Pb and Cd were found in Stagnosols due to their impeded drainage. Very low element concentrations (<1 μg l−1) in field-collected soil solutions using tension lysimeters (0.2 μm nylon filters) imply that migration largely occurred by preferential flow as particulate-bound species during intensive rainfall events. Our results indicate that the extent of Pb and Cd migration in soils is largely influenced by soil type. 相似文献