全文获取类型
收费全文 | 31253篇 |
免费 | 354篇 |
国内免费 | 469篇 |
专业分类
安全科学 | 991篇 |
废物处理 | 1478篇 |
环保管理 | 3826篇 |
综合类 | 5223篇 |
基础理论 | 8126篇 |
环境理论 | 20篇 |
污染及防治 | 8245篇 |
评价与监测 | 2153篇 |
社会与环境 | 1831篇 |
灾害及防治 | 183篇 |
出版年
2023年 | 153篇 |
2022年 | 344篇 |
2021年 | 342篇 |
2020年 | 254篇 |
2019年 | 304篇 |
2018年 | 507篇 |
2017年 | 500篇 |
2016年 | 766篇 |
2015年 | 591篇 |
2014年 | 914篇 |
2013年 | 2464篇 |
2012年 | 1105篇 |
2011年 | 1493篇 |
2010年 | 1207篇 |
2009年 | 1248篇 |
2008年 | 1481篇 |
2007年 | 1531篇 |
2006年 | 1298篇 |
2005年 | 1126篇 |
2004年 | 1026篇 |
2003年 | 1100篇 |
2002年 | 979篇 |
2001年 | 1256篇 |
2000年 | 876篇 |
1999年 | 529篇 |
1998年 | 364篇 |
1997年 | 367篇 |
1996年 | 371篇 |
1995年 | 432篇 |
1994年 | 452篇 |
1993年 | 359篇 |
1992年 | 381篇 |
1991年 | 358篇 |
1990年 | 395篇 |
1989年 | 348篇 |
1988年 | 299篇 |
1987年 | 280篇 |
1986年 | 231篇 |
1985年 | 252篇 |
1984年 | 273篇 |
1983年 | 263篇 |
1982年 | 249篇 |
1981年 | 223篇 |
1980年 | 176篇 |
1979年 | 197篇 |
1978年 | 178篇 |
1975年 | 142篇 |
1974年 | 119篇 |
1972年 | 131篇 |
1971年 | 132篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
942.
T.M. McIntire O.S. Ryder P.L. Gassman Z. Zhu S. Ghosal B.J. Finlayson-Pitts 《Atmospheric environment (Oxford, England : 1994)》2010,44(7):939-944
It is commonly assumed that atmospheric oxidation of hydrocarbon particles or hydrocarbon coatings on particles leads to polar products and increased water uptake, altering atmospheric visibility and increasing the likelihood they will act as cloud condensation nuclei (CCN). We show here through laboratory experiments that increased water uptake depends on the 3-dimensional structure of the particles. Laboratory studies of particles formed during ozonolysis of surface-bound alkenes, present as terminally unsaturated self-assembled monolayers (C8= SAM) on a silica substrate, were carried out at room temperature and 1 atm pressure. SAMs were exposed to ~1013 O3 molecules cm?3 for 40 min and resultant particles were analyzed using single particle Fourier transform infrared micro-spectroscopy (micro-FTIR) and secondary ion mass spectroscopy (SIMS). Spectroscopy results show that –COOH and other polar groups are formed but are buried inside a hydrophobic shell, consistent with earlier observations (McIntire et al., 2005, Moussa et al., 2009) that water uptake does not increase after reaction of the terminal alkene with O3. These insights into the 3-D structure of particles formed on oxidation have important implications for the ability of secondary organic aerosols to act as CCN. In addition, the nature of the surface of the particles is expected to determine their uptake into biological systems such as the surface of the lungs. 相似文献
943.
A.M.M. Manders M. Schaap X. Querol M.F.M.A. Albert J. Vercauteren T.A.J. Kuhlbusch R. Hoogerbrugge 《Atmospheric environment (Oxford, England : 1994)》2010,44(20):2434-2442
The oceans are a major source for particles that play an important role in many atmospheric processes. In Europe sea salt may contribute significantly to particulate matter concentrations. We have compiled sodium concentration data as a tracer for sea salt for 89 sites in Europe to provide more insight in the distribution of sea salt across Europe. The annual average sea salt concentrations above land were estimated to range between 0.3 and almost 13 μg m?3. Maximum concentrations are found at the Irish coast. At coastal sites along the Atlantic and North Sea coast concentrations tend to be around 5 μg m?3. More inland locations up to about 300 km away from the coast tend to show concentrations between 2 and 5 μg m?3, whereas sites further away from the coast are characterized by lower concentrations. An analysis of the representativity of the data with respect to a long term average showed that the long average is associated with a standard deviation of around 15%. The compilation of observations provides an improved overview of sea salt concentrations in Europe as well as an improved basis for model validation. Verification of the results of the LOTOS-EUROS model learned that the model represents well the spatial variability of the observed sea salt concentrations very well. However, the absolute concentrations are significantly overestimated due to large uncertainties in the emission and dry deposition parameterizations. Using the high explained variability in the gradients across Europe, the bias-corrected modelled distribution serves as a best estimate of the sea salt distribution across Europe for 2005. 相似文献
944.
S. Alfieri U. Amato M.F. Carfora M. Esposito V. Magliulo 《Atmospheric environment (Oxford, England : 1994)》2010,44(15):1866-1876
Quantifying trace gas emissions and the influence of surface exchange processes on the atmosphere is a necessary step towards the control of global greenhouse gas emissions and reliability of air quality models. This paper proposes a procedure based on the mass balance method and implemented on highly resolved aircraft data. It allows one to estimate surface exchanges on areas of several km2 and heterogeneous features exploiting the characteristics of convective boundary layer during steady state conditions that permit the estimation of emission/absorption terms as functions of advective fluxes only. A nonparametric approach is adopted and the fluxes on the surface of a virtual box surrounding the area of interest are reconstructed on the basis of scalar densities and wind vectors using Shepard functions. Two different techniques are also proposed to face lack of data on the top surface of the box. The method has been applied to experimental data coming from measurement campaigns on two different sites. It provides realistic estimates of the CO2 emission/absorption in the considered areas that are in good agreement with CO2 fluxes evaluated by Airborne Eddy Covariance and confirm the suitability of the proposed approach for the assessment of turbulent exchange of trace gases by composite landscapes. Uncertainties on the estimated emissions due to both propagation of the experimental error and interpolation have been quantified by bootstrap analysis as 6%. 相似文献
945.
Kai-Chung Cheng Marian D. Goebes Lynn M. Hildemann 《Atmospheric environment (Oxford, England : 1994)》2010,44(16):2062-2066
The effect of foot traffic on indoor particle resuspension was evaluated by associating non-prescribed foot traffic with simultaneous size-resolved airborne particulate matter (PM) concentrations in a northern California hospital. Foot traffic and PM were measured every 15 min in a carpeted hallway over two 27-h periods. The PM concentration in the hallway was modeled based on the foot traffic intensity, including the previous PM concentration via an autocorrelation regression method based on the well-mixed box model. All 5 size ranges of PM, ranging from 0.75–1 μm to 5–7.5 μm, were highly correlated with foot traffic measurements for both monitoring periods (p < 0.001, R2 = 0.87–0.90). However, correlations during daytime hours were less significant than nighttime. Coefficients found via this autoregressive analysis can be interpreted to reveal (i) time-independent contributions of walking activities on PM levels for a specific location; and (ii) size-specific characteristics of the resuspended PM. 相似文献
946.
Developed countries are major markets for developing country fresh produce. Demand by developed country consumers for spotless
produce has encouraged developing country consumers to rely increasingly on pesticides in producing fresh export vegetables.
However developed country pesticide standards enacted in response to reports of increased farmer and farm worker pesticide
poisoning and the food safety scandals of the 1980s and 1990s require changes in the way growers use pesticides. The EU has
especially developed stringent food safety standards relating to, among other things, pesticide usage. Under EU pesticide
standards (EU-PS) farmers are trained by their buyers on safe use of pesticides and then closely monitored under contract.
This paper looks at the impact of these standards on developing country farmers’ use of alternative pest management practices,
pesticide protective clothing and the actual usage of pesticides. It finds that compliance with EU-PS increases the use of
alternative pest management practices and protective clothing. However, EU-PS has mixed effect on the quantity of pesticides
used. The paper also finds that farmer’s education and access to information play an important role in the use of alternative
pest management practices. The paper concludes that EU-PS encourage the use of alternative pest management practices and pesticide
protective gear in production of fresh export vegetables. The findings imply that EU-PS promote environmentally-friendly methods
of production of fresh export vegetables in developing countries. 相似文献
947.
J. Ram Pillarisetti Jeroen C. J. M. van den Bergh 《Environment, Development and Sustainability》2010,12(1):49-62
What is a ‘sustainable nation’ and how can we identify and rank ‘sustainable nations?’ Are nations producing and consuming in a sustainable way? Although several aggregate indexes have been proposed to answer such questions, comprehensive and internationally comparable data are not available for most of these. This paper quantitatively compares three aggregate indexes of sustainability: the World Bank’s ‘Genuine Savings’ measure, the ‘Ecological Footprint,’ and the ‘Environmental Sustainability Index.’ These three indexes are available for a large number of countries and also seem to be the most influential among the aggregate indexes. This paper first discusses the main limitations and weaknesses of each of these indexes. Subsequently, it shows that rankings of sustainable nations and aggregate assessments of unsustainable world population and world GDP shares vary considerably among these indexes. This disagreement leads to suggestions for analysis and policy. One important insight is that climate change, arguable the most serious threat currently faced by humanity, is not or arbitrarily captured by the indexes. 相似文献
948.
This paper presents the present status of food security and ecological footprint, an indicator of environmental sustainability of the coastal zones of Bangladesh. To estimate the present status of the food security and ecological footprint of the coastal zone of Bangladesh, primary and secondary data were collected, and the present status of food security and environmental degradation (in terms of ecological footprint) were calculated. To estimate the household food security, primary data were also collected from all the households in a representative selected village. A quantitative method for computation of food security in grain equivalent based on economic returns (price) is developed, and a method of measuring sustainable development in terms of ecological footprint developed by Wackernagel is used to estimate the environmental sustainability (Wackernagel and Rees in Our ecological footprint: reducing human impact on the earth. New Society, Gabrioala, BC, 1996; Chambers et al. in Sharing nature’s interest-ecological footprint as an indicator of sustainability. Earthscan, London, 2000). Overall status of food security at upazila levels is good for all the upazilas except Shoronkhola, Shyamnager and Morrelgonj, and the best is the Kalapara upazila. But the status of food security at household levels is poor. Environmental status in the coastal zones is poor for all the upazilas except Kalapara and Galachipa. The worst is in the Mongla upazila. Environmental status has degraded mainly due to shrimp culture. This study suggests that control measures are needed for affected upazilas and any further expansion of the shrimp aquaculture to enhance the food security must take into account the environmental aspects of the locality under consideration. 相似文献
949.
The effect of invertebrate predation pressure by the cladoceran Leptodora kindti on the population structure of Daphnia galeata and D. hyalina has been estimated by analyzing the occurrence frequency of the normal and spined morphotypes in Lake Baikal. It is shown
that the growth of L. kindti population density leads to an increase in the proportion of the spined morphotype, while that of that of the normal morphotype
decreases. 相似文献
950.
A set of criteria allowing demarcation between algocenoses is proposed. These criteria characterize the species composition,
group of dominants, and taxonomic and ecological structure of algocenoses. 相似文献