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611.
The use of species distribution models (SDMs) to predict potential distributions of species is steadily increasing. A necessary
assumption when projecting models throughout space or time is that climatic niches are conservative, but recent findings of
niche shifts during biological invasion of particular plant and animal species have indicated that this assumption is not
categorically valid. One reason for observed shifts may relate to variable selection for modelling. In this study, we assess
differences in climatic niches in the native and invasive ranges of the Greenhouse frog (Eleutherodactylus planirostris). We analyze which variables are more ‘conserved’ in comparison to more ‘relaxed’ variables (i.e. subject to niche shift)
and how they influence transferability of SDMs developed with Maxent on the basis of ten bioclimatic layers best describing
the climatic requirements of the target species. We focus on degrees of niche similarity and conservatism using Schoener's
index and Hellinger distance. Significance of results are tested with null models. Results indicate that the degrees of niche
similarity and conservatism vary greatly among the predictive variables. Some shifts can be attributed to active habitat selection,
whereas others apparently reflect variation in the availability of climate conditions or biotic interactions between the frogs'
native and invasive ranges. Patterns suggesting active habitat selection also vary among variables. Our findings evoke considerable
implications on the transferability of SDMs over space and time, which is strongly affected by the choice and number of predictors.
The incorporation of ‘relaxed’ predictors not or only indirectly correlated with biologically meaningful predictors may lead
to erroneous predictions when projecting SDMs. We recommend thorough assessments of invasive species' ecology for the identification
biologically meaningful predictors facilitating transferability. 相似文献
612.
Testosterone mediates male reproductive trade-offs in vertebrates including mammals. In male edible dormice (Glis glis), reproductivity linked to high levels of testosterone reduces their ability to express torpor, which may be expected to dramatically increase thermoregulatory costs. Aims of this study were therefore to analyse behavioural and physiological consequences of reproductive activity in male edible dormice under ecologically and evolutionary relevant conditions in the field. As we frequently encountered sleeping groups in the field, we hypothesized that social thermoregulation should be an important measure to reduce energy expenditure especially in sexually active male edible dormice. Our results revealed that the occurrence of sleeping groups was negatively influenced by male body mass but not by reproductive status or ambient temperature. In reproductive as in non-reproductive males, the number of individuals huddling together was negatively influenced by their body mass. Thus in general males with a high body mass were sitting in smaller groups than males with a low body mass. However, in reproductive males group size was further negatively affected by ambient temperature and positively by testes size. Thus breeders formed larger sleeping groups at lower ambient temperatures and males with larger testes were found in larger groups than males with smaller testes. Measurements of oxygen consumption demonstrated that grouping behaviour represents an efficient strategy to reduce energy expenditure in edible dormice as it reduced energy requirements by almost 40%. In summary, results of this field study showcase how sexually active male edible dormice may, through behavioural adjustment, counterbalance high thermoregulatory costs associated with reproductive activity. 相似文献
613.
Kay Grossmann Thuro Arnold Robin Steudtner Stefan Weiss Gert Bernhard 《Die Naturwissenschaften》2009,96(8):963-974
Low-temperature alteration reactions on uranium phases may lead to the mobilization of uranium and thereby poses a potential
threat to humans living close to uranium-contaminated sites. In this study, the surface alteration of uraninite (UO2) and uranium tetrachloride (UCl4) in air atmosphere was studied by confocal laser scanning microscopy (CLSM) and laser-induced fluorescence spectroscopy using
an excitation wavelength of 408 nm. It was found that within minutes the oxidation state on the surface of the uraninite and
the uranium tetrachloride changed. During the surface alteration process U(IV) atoms on the uraninite and uranium tetrachloride
surface became stepwise oxidized by a one-electron step at first to U(V) and then further to U(VI). These observed changes
in the oxidation states of the uraninite surface were microscopically visualized and spectroscopically identified on the basis
of their fluorescence emission signal. A fluorescence signal in the wavelength range of 415–475 nm was indicative for metastable
uranium(V), and a fluorescence signal in the range of 480–560 nm was identified as uranium(VI). In addition, the oxidation
process of tetravalent uranium in aqueous solution at pH 0.3 was visualized by CLSM and U(V) was fluorescence spectroscopically
identified. The combination of microscopy and fluorescence spectroscopy provided a very convincing visualization of the brief
presence of U(V) as a metastable reaction intermediate and of the simultaneous coexistence of the three states U(IV), U(V),
and U(VI). These results have a significant importance for fundamental uranium redox chemistry and should contribute to a
better understanding of the geochemical behavior of uranium in nature.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
614.
Nicola Lugeri Zbigniew W. Kundzewicz Elisabetta Genovese Stefan Hochrainer Maciej Radziejewski 《Mitigation and Adaptation Strategies for Global Change》2010,15(7):621-639
Flood disasters have had a devastating effect worldwide over the past century, both in terms of human suffering and material
losses. The study of these events and development of more effective adaptation and mitigation policies has become a priority,
both in Europe and other parts of the globe. This paper detects and presents the spatial distribution of river flood risks
in Europe. The methodology we developed involves an assessment of three key risk components: exposure, vulnerability and hazard.
A topography-based flood hazard map of Europe, identifying low-lying areas adjacent to rivers, is presented and used to identify
risk, together with land-use data and damage-stage relationship for different land uses. The study covers river flood risk
for the entire European continent. This methodology can be used to determine the level of future risk, using the estimations
on Hazard, Exposure and Vulnerability from specific climate and economic development models. Annual average flood damage is
estimated for European regions, in absolute monetary terms and in % of regional Gross Domestic Product (GDP). The results
highlight regions where the threat to the economy from river flood hazard is of major concern. 相似文献
615.
616.
The stridulation of the giant pill-millipede genus Sphaerotherium from South Africa, one of only three groups of millipedes that produce sounds, was studied. One hundred one stridulation
series of a total of nine different species (Sphaerotherium dorsaloide, Sphaerotherium hanstroemi, Sphaerotherium mahaium, Sphaerotherium similare, Sphaerotherium punctulatum, Sphaerotherium convexitarsum, Sphaerotherium dorsale, Sphaerotherium rotundatum, and Sphaerotherium perbrincki) were analyzed. Stridulation sounds are produced only with a special field of ribs on the posterior surface of the posterior
telopod, which is actively moved over a field of sclerotized nubs on the inner margin of the anal shield. The Sphaerotherium male usually stridulates only when in contact with a female to initiate mating. This seems to prevent the female from volvating
into a ball or stimulate the female to uncoil when already rolled in. The sound analyzes revealed a broad frequency spectrum
in all stridulation sounds produced, without obvious differences in frequency distribution among species. However, the temporal
pattern of the stridulation varies greatly between species and seems to be species-specific, arguing for a species recognition
function of the stridulation during courtship behavior. A single species (S. punctulatum) was found to stridulate during mating while three species also show postcopulatory stridulation. Apparently, pill-millipedes
are not capable of acoustic perception, as no hearing organs are known, indicating that the communication is mainly based
on perception of temporal vibration patterns, and not of the acoustic signal itself. The need to overcome the rolling-in reflex
of the female is developed as a hypothesis why stridulation exists only in millipedes able to coil into a ball, and apparently
evolved four times independently in the superorder Oniscomorpha. 相似文献
617.
This study combines biology and mathematics, showing that a relatively simple question from molecular biology can lead to
complicated mathematics. The question is how to calculate the number of theoretically possible aliphatic amino acids as a
function of the number of carbon atoms in the side chain. The presented calculation is based on earlier results from theoretical
chemistry concerning alkyl compounds. Mathematical properties of this number series are highlighted. We discuss which of the
theoretically possible structures really occur in living organisms, such as leucine and isoleucine with a chain length of
four. This is done both for a strict definition of aliphatic amino acids only involving carbon and hydrogen atoms in their
side chain and for a less strict definition allowing sulphur, nitrogen and oxygen atoms. While the main focus is on proteinogenic
amino acids, we also give several examples of non-proteinogenic aliphatic amino acids, playing a role, for instance, in signalling.
The results are in agreement with a general phenomenon found in biology: Usually, only a small number of molecules are chosen
as building blocks to assemble an inconceivable number of different macromolecules as proteins. Thus, natural biological complexity
arises from the multifarious combination of building blocks. 相似文献
618.
Supply chain and logistics issues of bio-energy production 总被引:1,自引:0,他引:1
Stefan Gold 《Journal of Cleaner Production》2011,19(1):32-42
619.
Advancing sustainable urban transformation 总被引:1,自引:0,他引:1
620.
Stefan Gold 《Mitigation and Adaptation Strategies for Global Change》2011,16(4):439-462
What are the management challenges and opportunities of bio-energy chains for both running their business efficiently and effectively and fostering the relationships with most relevant external stakeholders? This question is approached by systematically reviewing papers at the interface of bio-energy and supply chain or logistics issues. The review conducted as content analysis is based on an analytic framework that conceives bio-energy chains between challenges and benefits of bio-energy production with simultaneous internal supply chain management and external stakeholder management needs. Smartly designed and operated bio-energy projects hold promising potentials of contributing to sustainable development by both mitigating climate change and strengthening adaptation capabilities. Our analysis distils specific strategies and success factors for tapping this potential on two levels: On a supply chain level, individually adapted and designed supply chain systems relying on trustful information exchange, cooperation and relational governance safeguard profitability while holding adverse ecological and social impacts of operation down; they allow, for instance, minimising costs and emissions, implementing new technologies, and coping with environmental uncertainties such as crop failures and volatile prices. On a stakeholder level, governments as key actors for designing the future legal framework of bio-energy are primary targets for lobbying activities of bio-energy representatives. Respective arguments may focus on economic development and job generation. By minimising its adverse impacts on society and eco-systems and by communicating these efforts credibly, bio-energy warrants its superiority over fossil energy systems. Involving NGOs and residents in early stages of bio-energy projects via transparent two-way communication considerably increase societal acceptance. 相似文献