全文获取类型
收费全文 | 6222篇 |
免费 | 53篇 |
国内免费 | 32篇 |
专业分类
安全科学 | 139篇 |
废物处理 | 277篇 |
环保管理 | 465篇 |
综合类 | 996篇 |
基础理论 | 1536篇 |
环境理论 | 6篇 |
污染及防治 | 2022篇 |
评价与监测 | 478篇 |
社会与环境 | 368篇 |
灾害及防治 | 20篇 |
出版年
2023年 | 66篇 |
2022年 | 152篇 |
2021年 | 173篇 |
2020年 | 81篇 |
2019年 | 99篇 |
2018年 | 253篇 |
2017年 | 263篇 |
2016年 | 334篇 |
2015年 | 223篇 |
2014年 | 325篇 |
2013年 | 479篇 |
2012年 | 356篇 |
2011年 | 418篇 |
2010年 | 271篇 |
2009年 | 241篇 |
2008年 | 375篇 |
2007年 | 344篇 |
2006年 | 283篇 |
2005年 | 221篇 |
2004年 | 205篇 |
2003年 | 166篇 |
2002年 | 138篇 |
2001年 | 94篇 |
2000年 | 53篇 |
1999年 | 52篇 |
1998年 | 27篇 |
1997年 | 27篇 |
1996年 | 24篇 |
1995年 | 36篇 |
1994年 | 31篇 |
1993年 | 16篇 |
1992年 | 23篇 |
1991年 | 23篇 |
1990年 | 22篇 |
1989年 | 19篇 |
1988年 | 18篇 |
1987年 | 12篇 |
1986年 | 25篇 |
1985年 | 15篇 |
1984年 | 14篇 |
1983年 | 13篇 |
1982年 | 20篇 |
1980年 | 13篇 |
1976年 | 11篇 |
1972年 | 11篇 |
1966年 | 19篇 |
1965年 | 12篇 |
1964年 | 11篇 |
1956年 | 11篇 |
1954年 | 11篇 |
排序方式: 共有6307条查询结果,搜索用时 15 毫秒
621.
The amount of struvite (MgNH4PO4·6H2O) produced by Myxococcus xanthus as well as the culture parameter values (pH, total phosphorus, total Kjeldahl nitrogen) were dependent on the culture medium used. Struvite formation started during the exponential phase and the maximum concentration was observed at the beginning of stationary growth phase. The addition of each medium component to the liquid culture influenced the amount of crystal produced. This amount did not depend on the pH increase during the culture period. The moment of the bacterial growth phase, at which each medium component was added, influenced the struvite formation. 相似文献
622.
Andréa MM Peres TB Luchini LC Pettinelli A 《Journal of environmental science and health. Part. B》2000,35(3):297-307
The soil oxidative and anaerobic processes, as well as, the microbial biomass were followed during three years in a cotton farm (Tatuí) where the recommended pesticides have been used for several years, and in an experimental field (S?o Paulo) treated first time with the same pesticides. The oxidative process was monitored by the dehydrogenase (DHA)-activity using triphenyltetrazolium chloride (TTC) as substrate. The anaerobic process was followed by the iron-oxide reduction, and the microbial biomass was estimated by the substrate (glucose)-indiced respiration. Increases in DHA-activity and in the microbial biomass occurred only in the farm soil, with concomitant decreases in iron-reduction. In the experimental field soil, the increases in DHA-activity were followed only by decreases in iron-reduction. Soil characteristics were the determining factor for different biological parameters after pesticide inputs. All the pesticides produced at least one clear but transient effect. 相似文献
623.
Concentrations of Pb in livers of willow grouse (Lagopus lagopus), black grouse (Tetrao tetrix), and hare (Lepus timidus) were determined in samples collected during the period 1990-92 from 77 locations distributed across Norway. Our objective was to elucidate the impact of long-range atmospheric transport on the Pb exposure of the animals. The moss Hylocomium splendens was measured for atmospheric Pb deposition and Pb in soil at 60-cm depth was determined to reflect the natural geochemical background at the study locations. Strong positive relationships were found between Pb in liver and atmospheric deposition of Pb for all species and age groups studied. Results indicate that long-range atmospheric transport was the main source of Pb in the animals studied. This conclusion was supported by Pb analysis of typical food plants for the animals. Correlation between Pb in liver and Pb in soil mineral matter was observed only when considering sites with very low impact of atmospheric deposition. Even though the observed liver Pb concentrations may seem low (< or =12 microg g(-1) dw) they approach levels where sub-lethal effects cannot be ignored. 相似文献
624.
In this paper, we study empirically whether uncertainty has an influence on trade in the US sulfur dioxide allowances market.
In particular, we investigate the role of uncertainty on banking behavior. To do this, we introduce a tractable, structural
model of trading permits under uncertainty. The model establishes a relation between banking behavior and risk preferences,
especially prudence in the Kimball (1990) sense. We then test this model using data on allowances, for utilities submitted to the US Environmental Protection Agency’s
Acid Rain Program, carried over from one year to the next. Evidence is found of imprudence, namely, utilities bank permits
in order to favor higher profits. Another finding is that larger utilities do not adopt behavior significantly different from
that of smaller ones.
This paper was presented at the “International Workshop on Uncertainty in Greenhouse Gas Inventories: Verification, Compliance
& Trading” in Warsaw, Poland, September 2004, under the title “Portfolio Management of Emissions Permits and Prudence Behavior.” 相似文献
625.
J. L. Bardasano J. Álvarez-Ude I. Gutiérrez M. Raposo R. Goya 《The Environmentalist》2007,27(4):519-523
Objectives This paper aims to provide evidence of an inductive electromagnetic bioeffect on the human brain, which is independent from
sound waves and produced by mobile phones, in proximal field, through correlating the EEG data obtained from electrodes placed
on both normal and cochlear deaf individuals.
Methods Two groups of subjects are placed under controlled electromagnetic conditions inside a Faraday chamber, 12 healthy and another
12 suffering from cochlear deafness). Each is sitting on a chair, fitted with additional support, and holding a cellular phone
2 cm away form the right auricular, in order to avoid a thermal effect as much as possible. All of them, relaxed and with
their eyes closed, are EEG recorded in a basal state with their mobile phones off. Then, each of them is again recorded under
the same conditions but with the mobile on and listening to the same conversation. In order to assess the observed EEG changes,
a statistical analysis by means of the FFT (Fast Fourier Transform) was carried out.
Results For both, healthy and cochlear deaf, assimilation or integration of the mobile phone signal by some electrodes is to be found.
This is due to the increase of amplitudes for alpha and theta waves, whereas the signal is not integrated in other electrodes.
By correlating the spectra of frequencies of corresponding EEG records for the same brain areas, we have not observed significative
differences for both groups.
Conclusions A possible electromagnetic direct inductive, non-thermal, bioeffect on the human brain is observed. This effect is produced
by the use of mobile phones and it bears no relation to the sound waves. 相似文献
626.
627.
628.
629.
Annika Varnäs Berit Balfors Charlotta Faith-Ell 《Journal of Cleaner Production》2009,17(13):1214-1222
Research and initiatives concerning green procurement have to a great extent focused on products. This article, however, explores the current practice, problems and opportunities of green procurement of construction contracts. In particular, the application of environmental criteria for contract awarding is targeted. The findings of the study indicate that both public and private clients in the Swedish construction industry take environmental issues into consideration in their procurements. The environmental preferences are often formulated as environmental requirements. However, environmental criteria in tender evaluation are less common and seldom affect the award decisions. The environmental evaluation criteria that do occur often relate to the contractors' capabilities of managing the environmental work in the project. 相似文献
630.