全文获取类型
收费全文 | 19698篇 |
免费 | 186篇 |
国内免费 | 109篇 |
专业分类
安全科学 | 522篇 |
废物处理 | 696篇 |
环保管理 | 2688篇 |
综合类 | 4037篇 |
基础理论 | 4789篇 |
环境理论 | 13篇 |
污染及防治 | 4685篇 |
评价与监测 | 1211篇 |
社会与环境 | 1216篇 |
灾害及防治 | 136篇 |
出版年
2022年 | 165篇 |
2021年 | 194篇 |
2020年 | 162篇 |
2019年 | 202篇 |
2018年 | 248篇 |
2017年 | 296篇 |
2016年 | 418篇 |
2015年 | 329篇 |
2014年 | 473篇 |
2013年 | 1593篇 |
2012年 | 586篇 |
2011年 | 795篇 |
2010年 | 608篇 |
2009年 | 708篇 |
2008年 | 766篇 |
2007年 | 828篇 |
2006年 | 747篇 |
2005年 | 602篇 |
2004年 | 585篇 |
2003年 | 609篇 |
2002年 | 534篇 |
2001年 | 657篇 |
2000年 | 508篇 |
1999年 | 303篇 |
1998年 | 231篇 |
1997年 | 223篇 |
1996年 | 235篇 |
1995年 | 266篇 |
1994年 | 238篇 |
1993年 | 245篇 |
1992年 | 246篇 |
1991年 | 238篇 |
1990年 | 254篇 |
1989年 | 208篇 |
1988年 | 178篇 |
1987年 | 158篇 |
1986年 | 179篇 |
1985年 | 185篇 |
1984年 | 182篇 |
1983年 | 197篇 |
1982年 | 178篇 |
1981年 | 198篇 |
1980年 | 178篇 |
1979年 | 169篇 |
1978年 | 128篇 |
1977年 | 142篇 |
1974年 | 122篇 |
1973年 | 107篇 |
1972年 | 127篇 |
1970年 | 103篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
The aim of this work is the study of a new stochastic diffusion model with a cubic‐type drift coefficient. The model is considered as the solution of an Ito stochastic differential equation. Using the Ito's stochastic calculus and properties of the Kummer function, the trend functions and steady‐state distribution for the process are obtained. Statistical estimation and corresponding computational methodology are established. Finally, the model is applied to modelling and prediction of the global CO2 emission in Spain. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
82.
The product service systems’ (PSS) sustainability potential is described in the framework of the new types of stakeholder relationships and/or partnerships, producing new convergence of economic interests, and a potential concomitant systemic resources optimization.In this perspective, it is argued that the design competencies should move towards those of the ‘strategic design’, thus introducing the concept of ‘strategic design for sustainability’: the design of an innovation strategy, shifting the business focus from designing (and selling) physical products only, to designing (and selling) a system of products and services which are jointly capable of fulfilling specific client demands, while re-orienting current unsustainable trends in production and consumption practices.Some examples of PSS are presented and discussed using the PSS categories ‘services providing added value to the product life cycle’, ‘services providing final results to customers’, and ‘services providing enabling platforms for customers’. The cases derive from an analysis of the ‘environmental friendly innovation’ yearly endowed prize submissions. The Politecnico di Milano University together with the Bocconi University and Legambiente (an environmental NGO) promotes the initiative in Italy. 相似文献
83.
Gregory I. Holwell Claire Winnick Tom Tregenza Marie E. Herberstein 《Behavioral ecology and sociobiology》2010,64(4):617-625
The rapid divergence of male genitalia is a widely observed evolutionary phenomenon. Although sexual selection is currently
regarded as providing the most likely driving force behind genital diversification, the mechanisms responsible are still debated.
Here, we investigate the relationship between male genital morphology and sperm transfer in the praying mantid Ciulfina klassi using geometric morphometrics. The shape of male genitalia in C. klassi influenced sperm transfer duration and the number and proportion of sperm transferred, suggesting that genital morphology
is under sexual selection in this species. Genital size however was not correlated with any aspect of sperm transfer. Intriguingly,
two of the major genital shape components correlated positively with the number of sperm transferred, but negatively with
sperm transfer duration. Hence, males that most effectively transfer sperm to the female spermatheca do so in a relatively
short period of time. A direct negative relationship was also found between sperm transfer duration and sperm transfer success.
Overall, our study suggests that the variable genital shape of Ciulfina may have been selected for more efficient sperm transfer. 相似文献
84.
Inna P. Solyanikova Andrej L. Mulyukin Natalja E. Suzina Galina I. El-Registan Ludmila A. Golovleva 《Journal of environmental science and health. Part. B》2013,48(7):638-647
The goals of the present work were as follows: to obtain the dormant forms of R. opacus 1cp; to study the phenotypic variability during their germination; to compare phenotypic variants during the growth on selective and elective media; and to reveal changes in the ability of the strain to destruct xenobiotics that had not been degradable before dormancy. It was shown that Rhodococcus opacus 1cp (the strain degrading chlorinated phenols) became able to utilize a broader spectrum of xenobiotics after storage in the dormant state. Germination of the dormant forms of R. opacus 1cp on an agarized medium was followed by emergence and development of phenotypic variants that could grow on 4-chlorophenol and 2,4,6-trichlorophenol without adaptation. The cells of R. opacus 1cp phenotypic variants also utilized all of the tested chlorinated phenols: 2,3-, 2,5-, and 2,6-dichloro-, 2,3,4- and 2,4,5-trichloro-, pentachlorophenol, and 1,2,4,5-tetrachlorobenzene in concentrations up to 60 mg/L, though at the lower rates than 4-CP and 2,4,6-TCP. The improved degradation of chlorinated phenols by R. opacus strain 1cp exposed to the growth arrest conditions demonstrates the significance of dormancy for further manifestation of the adaptive potential of populations. A new principle of selection of variants with improved biodegradative properties was proposed. It embraces introduction of the dormancy stage into the cell life cycle with subsequent direct inoculation of morphologically different colonies into the media with different toxicants, including those previously not degraded by the strain. 相似文献
85.
Michael D Aitken Mark D Sobsey Mina Shehee Kimberly E Blauth Vincent R Hill Joseph B Farrell Sharon P Nappier Glenn W Walters Phillip L Crunk Nicole Van Abel 《Water environment research》2005,77(7):3028-3036
Thermophilic-anaerobic digestion in a single-stage, mixed, continuous-flow reactor is not approved in the United States as a process capable of producing Class A biosolids for land application. This study was designed to evaluate the inactivation of pathogens and indicator organisms in such a reactor followed by batch treatment in a smaller reactor. The combined process was evaluated at 53 degrees C with sludges from three different sources and at 51 and 55 degrees C with sludge from one of the sources. Feed sludge to the continuous-flow reactor was spiked with the pathogen surrogates Ascaris suum and vaccine-strain poliovirus. Feed and effluent were analyzed for these organisms and for indigenous Salmonella spp., fecal coliforms, Clostridium perfringens spores, and somatic and male-specific coliphages. No viable Ascaris eggs were observed in the effluent from the continuous reactor at 53 or 55 degrees C, with greater than 2-log removals across the digester in all cases. Approximately 2-log removal was observed at 51 degrees C, but all samples of effluent biosolids contained at least one viable Ascaris egg at 51 degrees C. No viable poliovirus was found in the digester effluent at any of the operating conditions, and viable Salmonella spp. were measured in the digester effluent in only one sample throughout the study. The ability of the continuous reactor to remove fecal coliforms to below the Class A monitoring limit depended on the concentration in the feed sludge. There was no significant removal of Clostridium perfringens across the continuous reactor under any condition, and there also was limited removal of somatic coliphages. The removal of male-specific coliphages across the continuous reactor appeared to be related to temperature. Overall, at least one of the Class A pathogen criteria or the fecal coliform limit was exceeded in at least one sample in the continuous-reactor effluent at each temperature. Over the range of temperatures evaluated, the maximum time required to meet the Class A criteria by batch treatment of the continuous-reactor effluent was 1 hour for Ascaris suum and Salmonella spp. and 2 hours for fecal coliforms. 相似文献
86.
J. Morgan Grove Dexter H. Locke Jarlath P. M. O’Neil-Dunne 《Environmental management》2014,54(3):402-419
Several social theories have been proposed to explain the uneven distribution of vegetation in urban residential areas: population density, social stratification, luxury effect, and ecology of prestige. We evaluate these theories using a combination of demographic and socio-economic predictors of vegetative cover on all residential lands in New York City. We use diverse data sources including the City’s property database, time-series demographic and socio-economic data from the US Census, and land cover data from the University of Vermont’s Spatial Analysis Lab (SAL). These data are analyzed using a multi-model inferential, spatial econometrics approach. We also examine the distribution of vegetation within distinct market categories using Claritas’ Potential Rating Index for Zipcode Markets (PRIZM?) database. These categories can be disaggregated, corresponding to the four social theories. We compare the econometric and categorical results for validation. Models associated with ecology of prestige theory are more effective for predicting the distribution of vegetation. This suggests that private, residential patterns of vegetation, reflecting the consumption of environmentally relevant goods and services, are associated with different lifestyles and lifestages. Further, our spatial and temporal analyses suggest that there are significant spatial and temporal dependencies that have theoretical and methodological implications for understanding urban ecological systems. These findings may have policy implications. Decision makers may need to consider how to most effectively reach different social groups in terms of messages and messengers in order to advance land management practices and achieve urban sustainability. 相似文献
87.
L.J. Deacon L.J. Pankhurst G.H. Drew E.T. Hayes S. Jackson P.J. Longhurst J.W.S. Longhurst J. Liu S.J.T. Pollard S.F. Tyrrel 《Atmospheric environment (Oxford, England : 1994)》2009,43(35):5698-5701
Information on the particle size distribution of bioaerosols emitted from open air composting operations is valuable in evaluating potential health impacts and is a requirement for improved dispersion simulation modelling. The membrane filter method was used to study the particle size distribution of Aspergillus fumigatus spores in air 50 m downwind of a green waste compost screening operation at a commercial facility. The highest concentrations (approximately 8 × 104 CFU m−3) of culturable spores were found on filters with pore diameters in the range 1–2 μm which suggests that the majority of spores are emitted as single cells. The findings were compared to published data collected using an Andersen sampler. Results were significantly correlated (p < 0.01) indicating that the two methods are directly comparable across all particles sizes for Aspergillus spores. 相似文献
88.
The classical problem of pooling data of two independent random samples drawn possibly from two identical arbitrary populations is considered. Decision to pool the two samples or not is based on the outcome of the preliminary test and then a shrinkage technique is used. In an asymptotic setup, the distributional risks of the proposed estimators are derived and compared. This study reveals the robustness property of the proposed shrinkage preliminary test maximum likelihood estimator (SPTMLE) when the assumed restraints may not hold. It is shown that the proposed estimator provides a wider range than the usual preliminary test maximum likelihood estimator (PTMLE) in which it dominates the classical estimator. More importantly, the SPTMLE provides more meaningful size for the preliminary test. 相似文献
89.
Effects of ethylenediurea (EDU) on ozone-induced acceleration of foliar senescence in potato (Solanum tuberosum L.) 总被引:1,自引:0,他引:1
Experiments were conducted to examine the effects of the anti-ozonant ethylenediurea (EDU) and chronic ozone (O3) exposure on leaf physiology and senescence in an O3-sensitive potato cultivar (Solanum tuberosum L. cv. Norland). A dose-response experiment showed that an EDU concentration of 15 mg l(-1) soil (given as a soil drench) provided complete protection from accelerated foliar senescence induced by exposure to 0.1 microl l(-1) O3 for 5 h day(-1) for 11 days. EDU doses of 45 and 75 mg active ingredient l(-1) soil also gave protection but were associated with symptoms of toxicity and delayed senescence. In further experiments, plants were given 0 or 15 mg EDU l(-1) soil and exposed to clean air or 0.1 microl l(-1) O3 for 5 h day(-1) for 14 days. Chronic O3 exposure in the absence of EDU resulted in accelerated foliar senescence, characterized by early declines in net photosynthesis and Rubisco quantity in O3-treated plants relative to controls. EDU in the presence of O3 gave complete protection against symptoms of accelerated senescence. Senescence was not delayed in plants that received EDU in the absence of O3, and no symptoms of EDU toxicity were evident. The results suggest that EDU-induced tolerance to O3 was not based on 'anti-senescent' properties of this anti-ozonant. 相似文献
90.
Song ranging by the dusky antbird,Cercomacra tyrannina: ranging without song learning 总被引:2,自引:0,他引:2
In a population of dusky antbirds (Cercomacra tyrannina), less aggressive responses to distance-degraded playbacks than to undegraded playbacks of pair duets show that this tropical
suboscine passerine uses sound degradation to range distance from singing conspecifics. This is the first example of song-ranging
in a species that does not learn songs, supporting the hypothesis that ranging preceded the song learning that occurs in more
recently evolved passerine birds (oscines). Both sexes sing and are able to use song degradation to range distance from singers
when their sex-specific song is played back.
Received: 27 May 1994/Accepted after revision: 24 March 1996 相似文献