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251.
The anthropogenic emission sources of methane (CH4) and nitrous oxide (N2O) in the Federal Republic of Germany were investigated. The object of the recently completed first phase of this research project was to summarize the present knowledge about the emission sources, make a first rough estimate of the emissions, identify the need for further research in the field, and - as far as possible - discuss the existing possibilities to reduce emissions. The main CH4 emission sources identified are the landfills, stock farming and pit mining, the main N2O sources are agriculture (including a minor contribution from animal wastes) and the production of adipic acid, the latter possibly being reducible by means of a new catalytic process. The total anthropogenic emissions of CH4 from Germany are estimated at 5.4 – 7.7 million tonnes per year, contributing a share of roughly 2 % to the world-wide anthropogenic emissions (350 million t/a). Those of N2O are estimated at 200 000 – 280 000 tonnes per year (world-wide 1.4 – 6.5 million t/a). 相似文献
252.
Rainer Haas Alfred Krippendorf Torsten C. Schmidt Klaus Steinbach und Eberhard v. L?w 《Umweltwissenschaften und Schadstoff-Forschung》1998,10(5):289-293
Zusammenfassung Arsenkampfstoffe sind in der Umwelt persistent und kontaminieren bis heute Boden und Grundwasser. In diesem Beitrag werden
die chemischen Reaktionen der Arsenkamptstoffe Diphenylarsinchlorid (CLARK I), Phenylarsindichlorid (PFIFFIKUS), Ethylarsindichlorid
(DICK) sowie von Chlorvinylarsinverbindungen (LEWISITE) dargestellt. Die M?glichkeiten der chemisch-analytischen Erfassung
dieser chemischen Kampfstoffe als Originalsubstanzen und als Thiol-Derivate werden pr?sentiert.
相似文献
253.
254.
Böhme F Rinklebe J Stärk HJ Wennrich R Mothes S Neue HU 《Environmental science and pollution research international》2005,12(3):133-135
Background Estimations of gaseous mercury volatilization from soils are often complex, stationary and expensive. Our objective was to develop a mobile and more simple, easy to handle and more cost-effective field method allowing rapid estimates of potential Hg emissions from soils.
Methods. The study site is located in Germany, about 100 kilometers south-westerly of Berlin and influenced by the river Elbe and its tributary Saale river. The site is representative for a lot of other floodplain locations at the river Elbe and highly polluted with Hg and other heavy metals. For our study we developed a system consisting of a glass chamber gas, two gold traps, a battery operated pump and a gas meter. Adsorbed total gaseous mercury (TGM) in the gold traps was determined by use of atomic absorption spectrometry (AAS).
Results and Discussion. In contrast to the common used flux chambers we designed a chamber without inlet and named it gas suck up chamber (GSC). TGM fluxes determined with the GSC showed a very close linear correlation (r = 0.993) between the TGM content in the gold traps and the corresponding pumped gas volume. The TGM adsorbed, increased proportional with increasing gas volume indicating homogenous concentrations of gaseous mercury in the soil air sucked. In contrast to the commonly used dynamic flux chamber with the aim of precisely measuring actual fluxes of Hg from a defined soil area, we focused on developing of a measurement system which will allow rapid estimates of potential Hg emissions of a site. Earlier research at the study site indicated a high potential for releasing volatile Hg from the soil to the atmosphere. Indeed, due to the high Hg content of the soil significant amounts of TGM could be detected and no shortage was reached.
Conclusion. Our initial measurements are still too few in number neither to generalize the achieved results nor discuss controlling factors and processes. However, we are pleased to communicate that the developed GSC is well suited to become an effective sampling set up to rapidly estimate the magnitude of Hg volatilization from soils.
Outlook. Further measurements at other polluted locations are necessary to verify the GSC method. In addition the use of a mercury analyzer instead of gold traps is planned for faster risk assessments. 相似文献
255.
Zusammenfassung Durch r?umlich integrale Bestimmung der Schadstofffrachten [1] und zeitlich integrales Monitoring mit Schadstoff-Dosimetern
[1] l?sst sich Topographie und Bewegung von Schadstofffahnen im Grundwasser bestimmen. Konventionelle Methoden der Entnahme
und Untersuchung von Wasserproben sind ungeeignet zur Erfüllung dieser Anforderungen. Sorptionsaktive Passivsammler, die für
entsprechende Untersuchungen in der Gasphase konzipiert sind, eignen sich nicht zur Aquiferuntersuchung.
Die Passivsammler zur Untersuchung im ungest?rten Aquifer sind zentraler Bestandteil eines Systems von Probenahme- und Messsonden,
das die Autoren für das Monitoring chemischer und hydraulischer Wasser-Parameter entwickelt haben.
Mit den Passivsammlern lassen sich die relativen Schadstofffrachten in beliebig enger tiefenorientierter Anordnung der Messpunkte
und auch zeitlich integriert zur Gewinnung von vertikalen relativen Schadstofffracht-Profilen ermitteln. Organische und anorganische
relative Schadstofffrachten k?nnen damit bestimmt werden.
Die gaiasafe-Passivsammler sind einfach handhabbar und lassen sich nach standardisierten chemischen Analysenmethoden auswerten.
Damit erfüllen sie eine Reihe wesentlicher Anforderungen an das zielführende Monitoring von Schadstofffahnen. Die Passivsammler
sind auch geeignet für die In-situ-Untersuchung von ruhigen und bewegten Gew?ssern auch in gro?er Tiefe z.B. Abw?sserkan?le,
Kl?ranlagen, Flüsse und Meere und insbesondere zum Nachweis von Kontaminanten und Spurenstoffen in Wasserproben.
Online First: 10. 01. 2001 相似文献
256.
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259.
Rainer Sütfeld 《Chemoecology》1993,4(2):108-114
Summary Seedlings ofNuphar lutea (L.) Sm. were raised from seeds and cultivated in a synthetic sterile nutrient solution under physiologically controlled and undisturbed conditions. The extracellular release of carbon compounds from the plants into the surrounding medium was examined by direct carbon estimation, by various specific chemical assays and by HPLC analysis. Direct carbon estimation was not sensitive enough to obtain reliable values; five of six specific chemical assays also failed. Only the Folin-Denis assay indicated there was a production of phenolic compounds, which followed a linear course that took up to six days of incubation. The phenolic compounds ranged between 0.2 and 1.3 µg/h g dry weight. Rp-HPLC with UV detection yielded a major fraction containing at least five highly polar compounds (not retainable on reversed phase), and a minor fraction of at least eight less polar (rp-retainable) compounds. Exudation followed a linear course for some days up to a distinct level of saturation in the surrounding medium. Cultures incubated in light or absolute darkness exhibit the same production rates; however, lower temperatures caused significant reduction in the production rate and on the pattern of exuded compounds as well. After withdrawing the exuded compounds by rinsing the cultures, a new production can be repeatedly induced many times until the potential of the system is seemingly exhausted. Nuphar seedlings procedures are introduced as a new macrophyte system suitable for studying the mechanism of extracellular secretion among aquatic macrophytes. 相似文献
260.
Schobert R 《Die Naturwissenschaften》2007,94(1):1-11
Natural products containing tetronic acid or tetramic acid moieties continue to attract the interest of chemists, biologists,
and physicians due to their challenging structures and to the wide range of biological activities they display. This review
portrays the structural varieties of tetronic and tetramic acids and the spectrum of possible therapeutically relevant effects
in man for exemplary derivatives. Their biosynthetic origin from α-amino and α-hydroxy acids is briefly discussed as is the
relationship between their structures and their modes of interaction with biochemical effectors such as metal cations or enzymes.
A short overview of laboratory syntheses of the heterocyclic core structures of tetramic and tetronic acids is provided with
an emphasis on those emulating the biosynthesis. A synthesis from the α-amino or α-hydroxy esters and the cumulated phosphorus
ylide Ph3PCCO based upon a domino addition–intra-Wittig alkenation sequence is presented with applications to the preparation of the
antibiotics reutericyclin and tenuazonic acid, the cytotoxic melophlin B, and the enzyme inhibitor RK-682. Procedural advantages
of immobilizing either starting component by attaching it to a resin and its exploitation in the parallel synthesis of libraries
of potential drug candidates are described. The basic domino reaction can even be extended by further C–C bond forming steps
when starting from suitable α-hydroxy or α-amino allyl esters. Depending on the chosen reaction conditions, bioactive intermediates
of formally three to seven step long cascades can be obtained. Among them, herbicidal 3-alkyltetronic acids and lactone endoperoxides
with antiplasmodial activity exceeding that of the natural antimalarial lead artemisinin. Hence, this domino reaction gives
access to diversely functionalized derivatives of tetronic and tetramic acids. As it can also be ported to solid phase, it
is ideally suited for parallel and combinatorial processing. Future developments might include running such domino sequences
in continuous mode in arrays of “labs on microchips”. 相似文献