首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   11385篇
  免费   71篇
  国内免费   56篇
安全科学   255篇
废物处理   547篇
环保管理   974篇
综合类   1733篇
基础理论   2648篇
环境理论   4篇
污染及防治   2829篇
评价与监测   901篇
社会与环境   1565篇
灾害及防治   56篇
  2023年   62篇
  2022年   137篇
  2021年   129篇
  2020年   63篇
  2019年   91篇
  2018年   176篇
  2017年   204篇
  2016年   261篇
  2015年   177篇
  2014年   341篇
  2013年   905篇
  2012年   380篇
  2011年   502篇
  2010年   420篇
  2009年   454篇
  2008年   532篇
  2007年   554篇
  2006年   488篇
  2005年   439篇
  2004年   414篇
  2003年   406篇
  2002年   354篇
  2001年   468篇
  2000年   333篇
  1999年   184篇
  1998年   104篇
  1997年   130篇
  1996年   112篇
  1995年   133篇
  1994年   128篇
  1993年   112篇
  1992年   111篇
  1991年   116篇
  1990年   131篇
  1989年   104篇
  1988年   93篇
  1987年   90篇
  1986年   96篇
  1985年   86篇
  1984年   96篇
  1983年   80篇
  1982年   91篇
  1981年   58篇
  1980年   73篇
  1979年   75篇
  1978年   55篇
  1977年   56篇
  1974年   61篇
  1973年   60篇
  1972年   66篇
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
321.
Objective: Drink-driving represents a critical issue on international organizations’ agendas as one of the key behavioral risk factors in road traffic safety, alongside speed and nonuse of motorcycle helmets, seat belts, and child restraints. Changing road user behaviors regarding these 5 factors is a critical component in reducing road traffic injuries and casualties. The objective of this study is the identification of drivers who are more likely to contribute to crashes in the UK while impaired by alcohol to design targeted drink drive compliance campaigns.

Method: To profile drivers with the factor “impaired by alcohol” assigned in collisions, an extensive data set is used, including all reported injury collisions between 2011 and 2015 in the UK (police records), merged with the Experian Mosaic Database. A multilevel mixed-effects logistic regression is conducted, utilizing the hierarchical nature of the data (drivers within Mosaic types).

Results: Using multilevel mixed-effects logistic regression analysis, the finding is that some driver profiles are more likely to contribute to crashes and are assigned the contributory factor “impaired by alcohol.” Drink-related crashes are more common in some circumstances or for some crash-involved driver groups than others. For instance, alcohol-related crashes are more likely to occur on single carriageways and among males and 25- to 35-year-olds. Drink-drive-related crashes are found to be strongly associated with dark lighting conditions and, more specifically, with late night hours (the interval between 3:00 a.m. and 4:00 a.m. accounts for a third of the drink-drive-related collisions). Using the Experian Mosaic Database which divides the UK population into 66 types based on demographic, lifestyle, and behavior characteristics, the finding is that, among crash-involved drivers, some Mosaic types are significantly more likely (e.g., pocket pensions, dependent greys, streetwise singles) and others are significantly less likely (e.g., crowded kaleidoscope, cultural comfort, penthouse chic) to contribute to a drink-related crash.

Conclusions: The outcome is a more nuanced understanding of drivers contributing to drink-related crashes in the UK. The study concludes by discussing the implications for governments and other interested bodies for better targeting and delivery of public education campaigns and interventions.  相似文献   

322.
Research on urban insect pollinators is changing views on the biological value and ecological importance of cities. The abundance and diversity of native bee species in urban landscapes that are absent in nearby rural lands evidence the biological value and ecological importance of cities and have implications for biodiversity conservation. Lagging behind this revised image of the city are urban conservation programs that historically have invested in education and outreach rather than programs designed to achieve high‐priority species conservation results. We synthesized research on urban bee species diversity and abundance to determine how urban conservation could be repositioned to better align with new views on the ecological importance of urban landscapes. Due to insect pollinators’ relatively small functional requirements—habitat range, life cycle, and nesting behavior—relative to larger mammals, we argue that pollinators put high‐priority and high‐impact urban conservation within reach. In a rapidly urbanizing world, transforming how environmental managers view the city can improve citizen engagement and contribute to the development of more sustainable urbanization.  相似文献   
323.
324.
Approaches to prioritize conservation actions are gaining popularity. However, limited empirical evidence exists on which species might benefit most from threat mitigation and on what combination of threats, if mitigated simultaneously, would result in the best outcomes for biodiversity. We devised a way to prioritize threat mitigation at a regional scale with empirical evidence based on predicted changes to population dynamics—information that is lacking in most threat‐management prioritization frameworks that rely on expert elicitation. We used dynamic occupancy models to investigate the effects of multiple threats (tree cover, grazing, and presence of an hyperaggressive competitor, the Noisy Miner (Manorina melanocephala) on bird‐population dynamics in an endangered woodland community in southeastern Australia. The 3 threatening processes had different effects on different species. We used predicted patch‐colonization probabilities to estimate the benefit to each species of removing one or more threats. We then determined the complementary set of threat‐mitigation strategies that maximized colonization of all species while ensuring that redundant actions with little benefit were avoided. The single action that resulted in the highest colonization was increasing tree cover, which increased patch colonization by 5% and 11% on average across all species and for declining species, respectively. Combining Noisy Miner control with increasing tree cover increased species colonization by 10% and 19% on average for all species and for declining species respectively, and was a higher priority than changing grazing regimes. Guidance for prioritizing threat mitigation is critical in the face of cumulative threatening processes. By incorporating population dynamics in prioritization of threat management, our approach helps ensure funding is not wasted on ineffective management programs that target the wrong threats or species.  相似文献   
325.
Parabens are used because of their antimicrobial effects, yet they have multiple adverse effects. The aim of this work was to evaluate the bactericidal activity and bacterial toxicity of the most common parabens: methylparaben, ethylparaben, propylparaben, isopropylparaben, butylparaben, isobutylparaben and phenylparaben. The bactericidal action was evaluated by means of the dilution-neutralization method against Escherichia coli and Staphylococcus aureus, and the biotest of inhibition of growth of E. coli was applied for the bacterial toxicity assay. Bactericidal concentrations were reached only for propylparaben, butylparaben and isobutylparaben. The toxicity study showed methylparaben to be the least toxic, whereas the most toxic one was phenylparaben. It can be concluded that the disinfectant activity of the parabens studied is insignificant against S. aureus and E. coli. Acute toxicity is very low, and the inhibitory effect is weak. Our results provide information about the risk–benefit balance of parabens use.  相似文献   
326.
We have identified new arsenic-tolerant plant species Borreria verticillata (Rubiaceae) that has mine and non-mine populations at a highly contaminated site (CS) and an uncontaminated site (UCS), respectively, in Brazil. Plants of B. verticillata from both sites were cultivated at different As and P concentrations. At low P concentration, CS plants showed reduced As uptake, higher P translocation to shoots, higher constitutive levels of phenolic compounds in roots, and higher tolerance to this metalloid. At the lowest P and highest As concentration, CS plants showed higher biomass. In addition, CS plants showed higher P uptake in the absence of As, suggesting that more efficient P translocation could contribute more to tolerance than decreased As uptake. In contrast, at low P concentration, UCS plants showed higher As content in shoot and root, increase in phenol levels in roots, reduction in dry biomass, and decrease of the effective efficiency of photochemical reactions and the electron transport rate. Under higher P concentrations, the decrease in As uptake was similar in both populations. The differences between the two populations with respect to As and P uptake suggest that altered kinetic properties or expression of P transporters contribute to higher As tolerance in B. verticillata from CS. As a ruderal and As-tolerant plant, B. verticillata could be successfully used for the revegetation of contaminated soils.  相似文献   
327.
A novel approach for the green synthesis of silver nanoparticles (AgNPs) from aqueous solution of AgNO3 using culture supernatant of phenol degraded broth is reported in this work. The synthesis was observed within 10 h, and AgNPs showed characteristic surface plasmon resonance around 410 nm. Spherical nanoparticles of size less than 30 nm were observed in transmission electron microscopy. X-ray diffraction pattern corresponding to 111, 200, 220, and 311 revealed the crystalline nature of the as-formed nanoparticles. It was found that the colloidal solution of AgNP suspensions exhibited excellent stability over a wide range of ionic strength, pH, and temperature. The effect of pH and ionic strength indicated that stabilization is due to electrostatic repulsion arising from the negative charge of the conjugate proteins. The AgNPs showed highly potent antimicrobial activity against Gram-positive, Gram-negative, and fungal microorganisms. The as-prepared AgNPs showed excellent catalytic activity in reduction of 4-nitrophenol to 4-aminophenol by NaBH4. By manufacturing magnetic alginate beads, the reusability of the AgNPs for the catalytic reaction has been demonstrated.  相似文献   
328.
Isotopic analysis has become an important tool in the study of lateral links between ecosystems. The isotopic composition of carbon in terrestrial and aquatic primary producers can differ significantly, which provides an opportunity to identify the “marine” or “freshwater” carbon in the tissues of terrestrial animals. We measured the isotopic composition of C and N in tissues of soil invertebrates and estimated the proportion of “aquatic” carbon in the energy budget of terrestrial food webs at different distances from the Black Sea and a freshwater lake. Terrestrial predators are actively subsidized with carbon from the Black Sea to distance of up to about 50 m. The carbon subsidy from the freshwater lake is significant in the zone extending no farther than the forest border (ca. 15 m). Thus, the effect of allochthonous organic matter on terrestrial communities in both cases manifests itself only in a relatively narrow coastal strip.  相似文献   
329.
Mitigating the massive impacts of defaunation on natural ecosystems requires understanding and predicting hunting effort across the landscape. But such understanding has been hindered by the difficulty of assessing the movement patterns of hunters in thick forests and across complex terrain. We statistically tested hypotheses about the spatial distribution of hunting with circuit theory and structural equation models. We used a data set of >7000 known kill locations in Guyana and hunter movement models to test these methods. Comparing models with different resistance layers (i.e., different estimates of how terrain and land cover influence human movement speed) showed that rivers, on average, limited movement rather than serving as transport arteries. Moreover, far more kills occurred close to villages than in remote areas. This, combined with the lack of support for structural equation models that included latent terms for prey depletion driven by past overhunting, suggests that kill locations in this system tended to be driven by where hunters were currently foraging rather than by influences of historical harvest. These analyses are generalizable to a variety of ecosystems, species, and data types, providing a powerful way of enhancing maps and predictions of hunting effort across complex landscapes.  相似文献   
330.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号