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201.
Lewis A. Mtashobya 《Environmental monitoring and assessment》2017,189(10):519
Assessment of levels of pesticide residues in vegetables was carried out in some villages in the Western Usambara and Uluguru Mountains of Tanzania where varieties of vegetables are grown. Tomatoes and cabbages were the most popular enterprise grown all year round and therefore were selected as the model crops for this study. Analysis of the cleaned sample extracts on a gas chromatography with electron capture detector (GC-ECD) and confirmation on the Gas chromatography–mass spectrometry (GC-MS) revealed dominance of organochlorine pesticides. Organophosphorous pesticides (parathion and marathion) were only detected in some samples, however, in most cases with higher concentrations compared to organochlorine pesticides. Levels of pesticide residues detected in vegetables were up to: parathion 5.07 μg/Kg, marathion 3.73 μg/Kg, α-endosulfan 0.32 μg/Kg, β-endosulfan 0.53 μg/Kg, dieldrin 1.36 μg/Kg, γ-HCH 0.25 μg/Kg, α-HCH 0.09 μg/Kg, and p, p′-DDT 0.64 μg/Kg. These results clearly show that vegetables are contaminated with different pesticide residues. However, the total levels of pesticide residues in both tomatoes and cabbages are lower than their respective codex alimentarius maximum residue levels (MRLs). This means that the vegetables produced in the area are suitable for human consumption. 相似文献
202.
Although the fitness consequences of herbivory on terrestrial plants have been extensively studied, considerably less is known
about how partial predation impacts the fitness of clonal marine organisms. The trophic role of Caribbean parrotfish on coral
reefs is complex: while these fish are important herbivores, as corallivores (consumers of live coral tissue), they selectively
graze specific species and colonies of reef-building corals. Though the benefits of parrotfish herbivory for reef resilience
and conservation are well documented, the negative consequences of parrotfish grazing for coral reproductive fitness have
not been previously determined. We examined recently grazed colonies of Montastraea annularis corals to determine whether grazing was positively associated with coral reproductive effort. We measured gonad number, egg
number and size, and proportional reproductive allocation for grazed and intact coral colonies 2–5 days prior to their annual
spawning time. We found that parrotfish selectively grazed coral polyps with high total reproductive effort (number of gonads),
providing the first evidence that parrotfish selectively target specific tissue areas within a single coral colony. The removal
of polyps with high reproductive effort has direct adverse affects on coral fitness, with additional indirect implications
for colony growth and survival. We conclude that chronic grazing by parrotfishes has negative fitness consequences for reef-building
corals, and by extension, reef ecosystems. 相似文献
203.
In insects, the last male to mate with a female often gains access to a disproportionate number of subsequent fertilizations.
This study examined last-male sperm precedence patterns in doubly and triply mated Tribolium castaneum females. Sperm storage processes were investigated by measuring the quantity of sperm stored within the female spermatheca
following single, double, and triple matings. Both doubly mated and triply mated females exhibited high last-male sperm precedence
for progeny produced during the first 48 h following the last mating, with females in both groups exhibiting parallel declines
in sperm precedence 1 and 2 weeks later. The number of sperm stored by females increased by 33% between singly mated and doubly
mated females, indicating that the spermatheca is filled to only two-thirds capacity following insemination by the first male.
Based on the proportion of stored sperm from first and second matings, we tested predictions about sperm precedence values
based on models of random sperm mixing. High initial last-male sperm precedence strongly supports stratification of last-male
sperm. By 1–2 weeks after double matings, sperm precedence declined to levels indistinguishable from values expected under
random mixing. These results provide insight into mechanisms of sperm storage and utilization in this species.
Received: 20 August 1997 / Accepted after revision: 24 May 1998 相似文献
204.
Nitrosomonas europaea, a model ammonia oxidizing bacterium, was exposed to a wide variety of aromatic hydrocarbons in 3 h batch assays. The expression of NE1545, a phenol sentinel gene involved in fatty acid metabolism, was monitored via quantitative real-time polymerase chain reaction (qRT-PCR) and a Coulter Counter technique was used to monitor changes in cell volume. Decreases in cell volume and NE1545 gene expression correlated strongly with exposure to aromatic hydrocarbons that possessed a single polar group substitution (e.g. phenol and aniline). Aromatic hydrocarbons that contain no polar group substitutions (e.g. toluene) or multiple polar group substitutions (e.g. p-hydroquinone) caused negligible changes in NE1545 expression and cell volume. The oxidation of aromatic hydrocarbons by N. europaea from configurations without a single polar group to one with two polar groups (e.g. p-cresol oxidized to 4-hydroxybenzyl alcohol) and from configurations with no polar groups to one with a single polar group (e.g. ethylbenzene oxidized to 4-ethylphenol) greatly influenced NE1545 gene expression and observed changes in cell volume. Nitrification inhibition in N. europaea by the aromatic hydrocarbons was found to be completely reversible; however, the decreases in cell volume were not reversible suggesting a physical change in cell membrane composition. Ammonia monooxygenase blocking studies showed that the chemical exposure that was responsible for the cell volume decrease and up-regulation in gene expression and not the observed inhibition. N. europaea is the first bacterium shown to experience significant changes in cell volume when exposed to μM concentrations of aromatic hydrocarbons, three orders of magnitude lower than previous studies with other bacteria. 相似文献
205.
Chen D Liu ZL Banwart W 《Environmental science and pollution research international》2011,18(6):908-917
The potential RDX contamination of food chain from polluted soil is a significant concern in regards to both human health
and environment. Using a hydroponic system and selected soils spiked with RDX, this study disclosed that four crop plant species
maize (Zea mays), sorghum (Sorghum sudanese), wheat (Triticum aestivum), and soybean (Glycine max) were capable of RDX uptake with more in aerial parts than roots. The accumulation of RDX in the plant tissue is concentration-dependent
up to 21 mg RDX/L solution or 100 mg RDX/kg soil but not proportionally at higher RDX levels from 220 to 903 mg/kg soil. While
wheat plant tissue harbored the highest RDX concentration of 2,800 μg per gram dry biomass, maize was able to remove a maximum
of 3,267 μg RDX from soil per pot by five 4-week plants at 100 mg/kg of soil. Although RDX is toxic to plants, maize, sorghum,
and wheat showed reasonable growth in the presence of the chemical, whereas soybeans were more sensitive to RDX. Results of
this study facilitate assessment of the potential invasion of food chain by RDX-contaminated soils. 相似文献
206.
Lewis P. Goldshore John J. Tozzi 《Journal of the Air & Waste Management Association (1995)》2013,63(3):115-117
This paper examines the history of air pollution control in the State of New Jersey, particularly, how it relates to the development of the state-local governmental relationship, and to the coordination of their respective control efforts. It also describes the methodology for developing local control programs. The information presented in the paper is directed to those individuals who may be able to analogize the experience in New Jersey to situations developing in their own jurisdictions. 相似文献
207.
Lewis H. Rogers 《Journal of the Air & Waste Management Association (1995)》2013,63(8):828-829
The activities and accomplishments of the Air Pollution Control Association during 1974-1975 continued to show growth and expansion, although there was a decline in membership. We have a financial surplus to report in spite of the fact that our publications program was plagued with inflationary price increases in paper, printing and distribution. 相似文献
208.
Reinhold H. Ufrecht Jude T. Sommerfeld H. Clay Lewis 《Journal of the Air & Waste Management Association (1995)》2013,63(12):1348-1352
The purpose of this paper is to provide a helpful tool for the design of adsorption equipment, recognizing in particular the recent, more stringent regulations on air pollution. This work is based on an earlier paper by Hougen and Marshall,1 who developed therein an analytical adsorption model. Under certain assumptions, especially that of linear adsorption equilibrium, it is possible to express the results in the form of convenient usable charts. Although more sophisticated models2 have recently been developed, the numerical effort involved in solving the associated partial differential equations is such that practical application is often questionable. 相似文献
209.
The modulation of worker behavior by the vibration signal during house hunting in swarms of the honeybee, Apis mellifera 总被引:3,自引:3,他引:0
During house hunting, honeybee, Apis melli- fera, workers perform the vibration signal, which may function in a modulatory manner to influence several aspects of nestsite
selection and colony movement. We examined the role of the vibration signal in the house-hunting process of seven honeybee
swarms. The signal was performed by a small proportion of the older bees, and 20% of the vibrating bees also performed waggle
dances for nestsites. Compared to non-vibrating controls, vibrating bees exhibited increased rates of locomotion, were more
likely to move into the interiors of the swarms, and were more likely to fly from the clusters and perform waggle dances.
Recipients responded to the signal with increased locomotion and were more likely than non- vibrated controls to fly from
the swarms. Because vibration signals were intermixed with waggle dances by some vibrators, and because they stimulated flight
in recipients, the signals may have enhanced nestsite scouting and recruitment early in the house-hunting process. All swarms
exhibited increased vibration activity within 0.5–1 h of departure. During these final periods, numerous vibrating bees wove
repeatedly in and out of the clusters while signaling and motion on the swarms increased until it culminated in mass flight.
The peaks of vibration activity observed at the end of the house-hunting process may therefore have activated the entire swarm
for liftoff once a new nestsite had been selected. Thus, the vibration signal may help to integrate the behavior of numerous
groups of workers during nestsite selection and colony relocation.
Received: 17 January 2000 / Received in revised form: 5 April 2000 / Accepted: 3 May 2000 相似文献
210.
Management of microbial contamination in storm runoff from California coastal dairy pastures 总被引:1,自引:0,他引:1
Lewis DJ Atwill ER Lennox MS Pereira MD Miller WA Conrad PA Tate KW 《Journal of environmental quality》2010,39(5):1782-1789
A survey of storm runoff fecal coliform bacteria (FCB) from working farm and ranch pastures is presented in conjunction with a survey of FCB in manure management systems (MMS). The cross-sectional survey of pasture runoff was conducted on 34 pastures on five different dairies over 2 yr under varying conditions of precipitation, slope, manure management, and use of conservation practices such as vegetative filter strips. The MMS cross-sectional survey consisted of samples collected during 1 yr on nine different dairies from six loafing barns, nine primary lagoons, 12 secondary lagoons, and six irrigation sample points. Pasture runoff samples were additionally analyzed for Cryptosporidium sp. and Giardia duodenalis, whereby detectable concentrations occurred sporadically at higher FCB concentrations resulting in poor correlations with FCB. Prevalence of both parasites was lower relative to high-use areas studied simultaneously on these same farms. Application of manure to pastures more than 2 wk in advance of storm-associated runoff was related to a > or =80% reduction in FCB concentration and load compared to applications within 2 wk before a runoff event. For every 10 m of buffer length, a 24% reduction in FCB concentration was documented. A one-half (75%), one (90%), and two (99%) log10 reduction in manure FCB concentration was observed for manure holding times in MMS of approximately 20, 66, and 133 d, respectively. These results suggest that there are several management and conservation practices for working farms that may result in reduced FCB fluxes from agricultural operations. 相似文献