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排序方式: 共有190条查询结果,搜索用时 15 毫秒
181.
182.
Hotz GA Cohn SM Nelson J Mishkin D Castelblanco A Li P Duncan R;Pediatric Pedestrian Injury Task Force 《Traffic injury prevention》2004,5(2):132-136
OBJECTIVE: To evaluate the implementation of the WalkSafe Program, a school based educational injury prevention program for children grades Kindergarten through 5. METHODS: A randomized comparative design was used for this study. The study was conducted in two high-risk urban school districts, which were chosen based on the geographic areas with the highest pedestrian injury and fatality rates. Four elementary schools (two in each district) were identified as potential study sites. Two intervention schools, one in each school district, were randomly chosen to receive the WalkSafe program; the other two schools served as controls, and received no intervention. The data was collected within the classroom setting for both the intervention and control schools. All elementary school children were administered the same pedestrian safety questionnaire as a pre-test, post-test and at three months following the intervention. RESULTS: A total of 2300 children participated in the WalkSafe program. The intervention (I) schools showed significant improvement in post-test scores then the control (C) schools (p = 0.012), and the (I) schools were able to maintain their test scores as reflected in a three-month follow-up evaluation (p = 0.47). Grades 3-5 of the (I) schools showed significant improvement in their test scores over grades K-2 (p < 0.0001). CONCLUSION: The WalkSafe program was shown to improve the pedestrian safety knowledge of elementary school children. Future research will include implementing the WalkSafe program at each elementary school within a single high-risk district. 相似文献
183.
Qafoku NP Ainsworth CC Szecsody JE Bish DL Young JS McCready DE Qafoku OS 《Journal of environmental quality》2003,32(6):2364-2372
The high-level radioactive, Al-rich, concentrated alkaline and saline waste fluids stored in underground tanks have accidentally leaked into the vadose zone at the Hanford Site in Washington State. In addition to dissolution, precipitation is likely to occur when these waste fluids contact the sediments. The objective of this study was to investigate the solid phase transformations caused by dissolution and precipitation in the sediments treated with solutions similar to the waste fluids. Batch experiments at 323 K were conducted in metal- and glass-free systems under CO2 and O2 free conditions. Results from X-ray diffraction (XRD), quantitative X-ray diffraction (QXRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and energy dispersive X-ray fluorescence spectroscopy (EDXRF) indicated that significant solid phase transformations occurred in the sediments contacted with Al-rich, hyperalkaline, and saline solutions. The XRD and QXRD analyses confirmed that smectite and most likely biotite underwent dissolution. The SEM and the qualitative EDS analyses confirmed the formation of alumino-silicates in the groups of cancrinite and probably sodalite. The morphology of the alumino-silicates secondary phases changed in response to changes in the Si/Al aqueous molar ratio. The transformations in the sediments triggered by dissolution (weathering of soil minerals) and precipitation (formation of secondary phases with high specific surface area and probably high sorption capacities) may play a significant role in the immobilization and ultimate fate of radionuclides and contaminants such as Cs, Sr, and U in the Hanford vadose zone. 相似文献
184.
Substantial amounts of self-boiling, Al-rich, hyperalkaline, and saline high-level waste fluids (HLWF) were deposited to the vadose zone at the Hanford Site, in Washington State. The objective of this study was to investigate the effects of similar fluids on the extent of dissolution and precipitation in the sediments. Metal- and glass-free systems were used to conduct batch experiments at 323 K under CO2 and O2 free conditions. Base-induced dissolution of the soil minerals was rapid in the first 48 h as indicated by immediate releases of Si and Fe into the soil solution. Potassium release lagged behind and dissolution of K-bearing minerals (mica and K-feldspar) proceeded faster only after 2 to 3 d of the experiment. Silicon and Fe release exhibited high dependence on aqueous [Al] (rate orders <-1), because Al decreased free OH concentration in the contact solution and probably inhibited soil mineral dissolution. Initial K release exhibited low dependence on [Al] (fractional rate orders). Initial dissolution rates calculated based on Si release varied with aqueous [Al] from 29.47 to 4.35 x 10(-12) mol m(-2) s(-1). Aluminum participated in the formation of the secondary phases (precipitation rates of 10(-8) mol s(-1)) but the overall precipitation rate of alumino-silicate secondary phases was probably controlled by aqueous [Si] (rates of 10(-9), and rate constants between 0.0054 and 0.0084 h(-1)). The changes in the soil solution chemistry (release of K, Si, Fe, and other elements) may play a significant role in the fate of radionuclides and contaminants like Cs, Sr, Cr, and U in the Hanford sediments. 相似文献
185.
Anderson P Davidson CM Duncan AL Littlejohn D Ure AM Garden LM 《Journal of environmental monitoring : JEM》2000,2(3):234-239
Made-up ground collected from layers of a trial pit excavated on a former industrial site was treated with artificial rainwater in a series of column leaching and sorption experiments. Metal mobility and the ability of various layers of material obtained from the pit to act as sources or sinks of potentially toxic elements were assessed. Samples from different layers varied in their abilities to raise the pH of rainwater applied at pH 3.5 and 4.3, and this was reflected in the amounts of metals mobilised by the rainwater as it percolated through the soil column. Material from the top two layers of the pit released cadmium, copper, manganese, lead, nickel and zinc to the aqueous phase, but the lower layers, with higher buffering capacity, were able to resist acidification even when the equivalent of 12 months' rainfall (western UK) was applied. Column sorption experiments confirmed the ability of material from layer 4 (48-50 cm) to take up copper, manganese and zinc. Metals were determined in the leachates by flame and electrothermal atomic absorption spectrometry and principle anions by ion chromatography. 相似文献
186.
A 30 x 0.9 cm piece of steel rod bent in the shape of an “L” and attached by hose clamps to a 15 x 3.2 cm section of plastic pipe sliding on an 86 x 1.9 cm steel shaft was tested for use in measuring scour and fill of salmon spawning riffles. Installed along channel cross-sections, results of tests at four sites on two hydraulically different streams showed the device to be useful in monitoring event specific scour and fill. Measurement error was estimated to be ± 10 mm. 相似文献
187.
Despite a recent emphasis on ‘evidence based policy’ accompanied by an abundance of ‘green’ policy instruments, experience from the European Union and OECD countries shows that decisions which truly aim to balance environmental considerations with social and economic ones remain thin on the ground. Moreover, many policies seem to fall short of, or directly contradict what the available ‘evidence’ suggests is required. This is a synthesis paper bringing together literature from the fields of political science, geography, sociology and science and technology studies to outline some of the obscurities relating to the use of scientific evidence in environmental decision-making. In this paper, we suggest that an exploration of three key inter-related issues is necessary to develop a richer understanding of why evidence and policy interact as they do. These are the nature of evidence itself; the normative, moral or ethical ‘politics’ of policy-making; and the operation of power in the policy process. Our primary goal is to bring various literatures together to better conceptualise the evidence–policy relationship. In so doing, we outline specific challenges for knowledge producers who set research priorities, and design and direct research projects. We also highlight significant implications for policy decision-making processes. 相似文献
188.
Mark K. Greco Dorothee Hoffmann Anne Dollin Michael Duncan Robert Spooner-Hart Peter Neumann 《Die Naturwissenschaften》2010,97(3):319-323
Workers from social insect colonies use different defence strategies to combat invaders. Nevertheless, some parasitic species
are able to bypass colony defences. In particular, some beetle nest invaders cannot be killed or removed by workers of social
bees, thus creating the need for alternative social defence strategies to ensure colony survival. Here we show, using diagnostic
radioentomology, that stingless bee workers (Trigona carbonaria) immediately mummify invading adult small hive beetles (Aethina tumida) alive by coating them with a mixture of resin, wax and mud, thereby preventing severe damage to the colony. In sharp contrast
to the responses of honeybee and bumblebee colonies, the rapid live mummification strategy of T. carbonaria effectively prevents beetle advancements and removes their ability to reproduce. The convergent evolution of mummification
in stingless bees and encapsulation in honeybees is another striking example of co-evolution between insect societies and
their parasites. 相似文献
189.
Efficient cooperation in eusocial insect colonies requires effective communication, and there is abundant evidence of non-volatile
chemicals playing a role in regulating reproduction within colonies. In contrast, there have been fewer studies investigating
the role of volatile chemicals. This study investigated the potential role of volatile chemicals in regulating queen reproduction
either by directly inhibiting queen reproduction or by honestly signalling queen fecundity to workers. We tested this using
multiple queen colonies of the ant (Leptothorax acervorum) from a functionally monogynous population where one queen monopolizes all reproduction. Nine colonies, each with an established
laying queen, were split to produce two colony fragments—one containing the reproducing queen (group 1) and one containing
only previously non-reproducing queens (group 2). Each group was separated by a fine wire mesh preventing physical contact,
but allowing volatile chemical contact. In each group 2 fragment, we found that a single formerly non-reproductive queen commenced
reproduction and that the rate of egg laying and maximum number of eggs recorded did not significantly differ between groups
1 and 2, results that do not support volatile chemicals as playing a role in regulating queen reproduction. Instead, our findings
suggest that physical contact is necessary to maintain functional monogyny. 相似文献
190.
Benettayeb Asmaa Usman Muhammad Tinashe Coffee Calvin Adam Traore Haddou Boumediene 《Environmental science and pollution research international》2022,29(32):48185-48209
Environmental Science and Pollution Research - The increasing demand for using competent and inexpensive methods based on biomaterials, like adsorption and biosorption, has given rise... 相似文献