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排序方式: 共有165条查询结果,搜索用时 218 毫秒
41.
Mehri Kaviani Moghadam Saied Mohammad Firoozabadi Mahyar Janahmadi 《The Environmentalist》2008,28(4):341-347
In spite of growing concern about the influence of magnetic fields on biological systems, the interaction between extremely
low frequency magnetic field (ELF magnetic fields) and biological structures at the cellular level remains obscure. The aim
of this study was to investigate if 50 Hz magnetic fields could have an effect on the neuronal excitability and firing responses.
Under Current-Clamp condition, exposure to 50 Hz ELF magnetic fields at 2 mT or 0.8 mT intensities resulted in an increase
in the peak amplitude of action potential and after hyperpolaization potential in a time dependent manner. Both magnetic field
intensities decreased also the firing frequency and the duration of action potential. Taken together, these data suggest that
50 Hz ELF magnetic fields at 2 mT or 0.8 mT intensities may change the electrophysiological behavior of neuronal cells and
underlying ion channel currents. 相似文献
42.
磁种-磁滤技术处理污染河水的试验研究 总被引:1,自引:0,他引:1
采用磁种-磁滤技术处理广州市两条河涌的污染水,考察了磁种投加量、混凝剂用量、磁场强度和磁滤速度对出水浊度的影响,并确定了最佳试验条件。结果表明,该工艺对TP、SS和浊度的去除效果较好,去除率分别为96.2%、92.4%和93.9%,对CODCr有一定的去除效果,去除率为68.2%,但对NH4^ -N的去除效果较差,去除率仅为25%。 相似文献
43.
44.
Occupational exposure to radiofrequency (RF) and static magnetic fields at magnetic resonance imaging (MRI) suites is of continuing
concern to personnel who routinely work in this environment. Questions regarding the levels of occupational RF and static
field exposure have increased with the increasing demand for anesthetics to be administered in this environment. The present
study was thus designed towards addressing the above-mentioned problem by gaining information regarding exposure levels of
clinical personnel at MRI units in South Africa. Three 1.5 MRI units in Bloemfontein, South Africa were utilized to evaluate
the exposure of clinical personnel to the electromagnetic fields present in the MRI environment over a period of time and
during different clinical MRI procedures. Three rounds of measurements of RF fields in the MRI environment were done. All
the three measurement rounds were focused on the low frequencies, 5 Hz–32 kHz, as well as on the high frequencies, 300 kHz–40 GHz.
First round measurements were done to establish the background of the RF fields in and around the magnet room during an MRI
examination. Second round RF field measurements were done at a specific location, 1 m away from the bore on the right-hand
side of the bed, in the MRI room. The third round measurements were of the same format as the second round, but the specific
location was against the magnet bore. Two pieces of Narda Safety Test Solution instruments, the EFA-300 and EMR-300, were
used to measure the electromagnetic and magnetic exposure fields generated from the MRI scanners. Results of the measurements
indicate that the electromagnetic fields measured during different clinical procedures do not exceed the International Commission
on Non-Ionizing Radiation Protection (2000) guidelines in these units. Results from round two and three showed that the RF
and gradient exposure 1 m and up against the bore entrance does not exceed these guidelines (rms average over 6 min). Ongoing
new developments in MRI scanning create the need for continuously monitoring exposure of patients and workers to the EMF fields
in the MRI environment. 相似文献
45.
The magnetic properties of tree leaves along with their ecological, economical and aesthetic importance can be used to control
road derived respirable particulates. Isothermal remanent magnetization (IRM300 mT) of three different tree leaves viz. Mango (Mangifera indica), Sisso (Dalbergia sisso) and Banyan (Ficus benghalensis) were determined and IRM300 mT normalized for the leaf area. The normalized 2-D magnetization of leaves as shown by results is dominantly controlled
by leaf morphology and traffic density. F. benghalensis (Banyan) leaf has highest 2-D magnetization and D. sisso (Sisso) leaf having least 2-D magnetization suggesting greater ability of F. benghalensis (Banyan) tree leaves to reduce magnetic particulates. The particle size of the magnetic grains falls in the category of PM2.5,
a particle size hazardous to human health due to its capacity to be inhaled deeply into the lungs. 相似文献
46.
D'Emilio M Chianese D Coppola R Macchiato M Ragosta M 《Environmental monitoring and assessment》2007,125(1-3):137-146
In the framework of the development of new methods for measuring and monitoring soil pollution, this paper deals with the
use of magnetic methodologies to monitor the heavy metals presence in soils. In particular it shows a procedure for collecting
magnetic susceptibility measurements in order to interpret them as proxy variable for monitoring heavy metals in soils. Magnetic
measurements are carried out using a magnetic susceptibility meter with two different probes for in situ field surveys. The
experimental procedure is divided in two parts. In the first part we carry out laboratory tests aimed to evaluate, for both
the probes, the effective investigation depth for soil, the measurement reproducibility under different conditions, and the
influence of water content. We complete this part comparing in situ measurements obtained by means of two probes with different
characteristics. In the second part we carry out tests to evaluate the relationships between heavy metal levels and magnetic
susceptibility values of soil samples. We investigate the variability of the magnetic susceptibility measurements contaminating
different soil samples with well known concentration of heavy metals. Moreover we study the correlation between magnetic susceptibility
values and metal concentrations, determined by means of AAS, in soil samples collected during a field survey. Results suggest
that a careful check of the experimental procedure play a crucial role for using magnetic susceptibility measurements for
heavy metals in situ monitoring. This is very helpful both for improving the quality of data and for making simpler data interpretation. 相似文献
47.
48.
Environmental pollution, a major problem worldwide, poses considerable threat to human health and ecological environment. Efficient and reliable detection technologies, which focus on the appearance of emerging environmental and trace pollutants, are urgently needed. Surface-enhanced Raman scattering(SERS) has become an attractive analytical tool for sensing trace targets in environmental field because of its inherent molecular fingerprint specificity and high sensitivity. In this review, we focused on the recent developments in the integration of magnetic nanoparticles(MNPs) with SERS for facilitating sensitive detection of environmental pollutants. An overview and classification of different types of MNPs for SERS detection were initially provided, enabling us to categorize the huge amount of literature that was available in the interdisciplinary research field of MNPs based SERS technology. Then, the basic working principles and applications of MNPs in SERS detection were presented. Subsequently, the detection technologies integrating MNPs with SERS that eventually were used for the detection of various environmental pollutions were reviewed. Finally, the advantages of MNP-basedSERS detection technology for environmental pollutants were concluded, and the current challenges and future outlook of this technology in practical applications were highlighted. The application of the MNPsbasedSERS techniques for environmental analysis will be significantly advanced with the great progresses of the nanotechnologies, optics, and materials. 相似文献
49.
Hui Zhang Jianguo Liu Changjin Ou Faheem Jinyou Shen Hongxia Yu Zhenhuan Jiao Weiqing Han Xiuyun Sun Jiansheng Li Lianjun Wang 《环境科学学报(英文版)》2017,29(3):1-8
The potentially hazardous iron-containing sludge from the Fenton process requires proper treatment and disposal, which often results in high treatment cost. In this study, a novel method for the reuse of Fenton sludge as an iron source for the synthesis of nickel ferrite particles(NiFe_2O_4) is proposed. Through a co-precipitation method followed by sintering at 800°C, magnetic NiFe_2O_4 particles were successfully synthesized, which was confirmed by powder X-ray diffraction(XRD), scanning electronic microscopy(SEM), energy dispersive spectroscopy(EDS), Fourier transform infrared spectroscopy(FT-IR) and Raman spectroscopy. The synthesized NiFe_2O_4 could be used as an efficient catalyst in the heterogeneous Fenton process. In phenol degradation with H_2O_2 or NiFe_2O_4 alone, the phenol removal efficiencies within the reaction time of 330 min were as low as 5.9% ± 0.1% and 13.5% ±0.4%, respectively. However, in the presence of both NiFe_2O_4 and H_2O_2, phenol removal efficiency as high as 95% ± 3.4% could be achieved, indicating the excellent catalytic performance of NiFe_2O_4 in the heterogeneous Fenton process. Notably, a rapid electron exchange between_Ni II and_Fe III ions in the NiFe_2O_4 structure could be beneficial for the Fenton reaction. In addition, the magnetic catalyst was relatively stable, highly active and recoverable, and has potential applications in the Fenton process for organic pollutant removal. 相似文献
50.
Lagerstroemia speciosa bark (LB) embedded magnetic nanoparticles were prepared by co-precipitation of Fe2+ and Fe3+ salt solution with ammonia and LB for Cr(VI) removal from aqueous solution. The native LB, magnetic nanoparticle (MNP), L. speciosa embedded magnetic nanoparticle (MNPLB) and Cr(VI) adsorbed MNPLB particles were characterized by SEM–EDX, TEM, BET-surface area, FT-IR, XRD and TGA methods. TEM analysis confirmed nearly spherical shape of MNP with an average diameter of 8.76 nm and the surface modification did not result in the phase change of MNP as established by XRD analysis, while led to the formation of secondary particles of MNPLB with diameter of 18.54 nm. Characterization results revealed covalent binding between the hydroxyl group of MNP and carboxyl group of LB particles and further confirmed its physico-chemical nature favorable for Cr(VI) adsorption. The Cr(VI) adsorption on to MNPLB particle as an adsorbent was tested under different contact time, initial Cr(VI) concentration, adsorbent dose, initial pH, temperature and agitation speed. The results of the equilibrium and kinetics of adsorption were well described by Langmuir isotherm and pseudo-second-order model, respectively. The thermodynamic parameters suggest spontaneous and endothermic nature of Cr(VI) adsorption onto MNPLB. The maximum adsorption capacity for MNPLB was calculated to be 434.78 mg/g and these particles even after Cr(VI) adsorption were collected effortlessly from the aqueous solution by a magnet. The desorption of Cr(VI)-adsorbed MNPLB was found to be more than 93.72% with spent MNPLB depicting eleven successive adsorption–desorption cycles. 相似文献