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861.
862.
Hans Schreier Sandra Brown George Kennedy Pravakar B. Shah 《Environmental management》1991,15(6):815-822
A GIS-based land evaluation model was developed to determine the food, feed, and fuelwood sufficiency of all districts in
Nepal. Resource surpluses or deficits were calculated for each district for 1981, the year for which the national land resource
data were available. Of the three resources, feed supplies were found to be the most critical. Feed deficits occurred in 57%
of all districts in 1981, while food and fuelwood deficits occurred in less than 10% of all districts. Different scenarios
were carried out for the year 2000 to estimate the magnitude of future resource deficits, assuming resource use and yields
in Nepal remain constant in the face of growing population and livestock numbers. Linking resource data with spreadsheet and
GIS systems provides a new way to understand and evaluate resources at the district and national levels. To more fully capture
the usefulness of this approach, information on rates of change in productivity and land use is needed. 相似文献
863.
ABSTRACT The calls for greater racial equity also means cleaning up the air, water, and soil. Poor people needlessly suffer more in Louisville than the same low-income people in West Coast cites. If we adopted the same tough, environmental regulations as our West Coast Counterparts West Louisville would surely bloom instead of slowly die. The unfairness between black and white neighbourhoods is stark and vivid. As the great urbanist, Jane Jacobs, once said: “everyone hungers for a first class neighbourhood for both pride and dignity?…?nobody wants a second class neighborhood.” First class neighbourhoods are safe, healthy, sustainable, and prosperous. It is a human right; a Worldwide right. 相似文献
864.
Paramecium generates persistent shifts of the membrane potential of a few millivolts depending on its orientation with respect to the
gravity vector. The resulting potential-induced modulation of the speed of propulsion is called gravikinesis because it acts
to neutralize, fully or in part, sedimentation. Gravisensitivity is maximal at neutral orientation, i.e., in horizontally
swimming cells, when the gravitational force per unit membrane area is at minimum. Stimulus-response relationships and energetic
considerations show that sensing of the gravity vector by a nonspecialized, single-cell organism ranks among the most sensitive
mechanoreceptors known in nature.
Received: 15 December 1998 / Accepted: 18 February 1999 相似文献
865.
866.
Hans?G.?ErkertEmail author Peter?M.?Kappeler 《Behavioral ecology and sociobiology》2004,57(2):174-186
Madagascar is characterised by pronounced annual climatic and ecological seasonality and harbours a radiation of closely related sympatric primates (Lemuriformes) that exhibit diurnal, nocturnal and cathemeral activity patterns. We collected continuous activity data over a complete annual cycle from wild diurnal Verreauxs sifakas (Propithecus v. verreauxi) to contribute detailed and comparative data: (1) to characterise their diel and seasonal activity rhythms, (2) to identify factors shaping variation in activity rhythms, and (3) to help reconstruct the evolutionary transition from nocturnal to diurnal activity. We fitted eight adult sifakas from seven different groups living in Kirindy forest with an accelerometer/data logger device and recorded their activity in 5-min bins for a total of 12 months. We characterise P. verreauxi as a strictly diurnal species with a pronounced bimodal activity pattern that briefly changed to a more unimodal pattern during their annual mating season (January to March). We documented significant annual variation in total daily activity, activity time, and activity level, as well as in most parameters characterising their bimodal activity pattern. Despite a significant positive correlation of the animals activity time with day length, pronounced annual variation in the phase position of onset and end of activity in relation to sunrise and sunset times could also be discerned. Minor enhancing effects of moonlight on nocturnal activity were only found for the first 3 h of the inactivity period. Bimodality of the activity pattern and the additional reduction of activity time during the cold and dry winter months associated with reduced food availability can be interpreted as flexible behavioural adaptations to reduce energy expenditure. We therefore propose that energetic and thermoregulatory benefits are important factors shaping these primates activity pattern.Communicated by C. Nunn 相似文献
867.
Contrary to vertebrates, sperm production in insects may bear considerable costs for males. This is especially true in species
that donate spermatophores containing sperm and nutrient-rich accessory gland products like in butterflies. Hence, spermatophores
at first and subsequent copulations can differ in a quantitative and qualitative way. Such effects have particularly been
shown in polyandrous species providing large spermatophores. Here we experimentally tested the effect of male mating status
(virgin male vs recently mated male) on copulation duration, spermatophore size and females’ fitness components in a monandrous
butterfly Pararge aegeria that typically donates small spermatophores. Copulations with non-virgin males lasted on average five times longer than that
with virgin males and resulted in a spermatophore which was on average three times smaller. Number of eggs laid and female
life span were not affected by the mating status treatment, but there was a significant effect on the number of living caterpillars
a female produced, as copulations with virgin males resulted in higher numbers of larval offspring. Interestingly, the difference
in spermatophore mass at the first and the second copulation increased with male body size. This suggests differential spermatophore
allocation decisions among males of different size. Consequences for females and potential mechanisms influencing female fitness
components are discussed. Given the small absolute size of spermatophores in P. aegeria, components other than consumable nutrients (perhaps hormones) should cause the observed effects. 相似文献
868.
869.
Michelle Casey Chris Gennings W Hans Carter Jr Virginia C Moser Jane Ellen Simmons 《Environmental and Ecological Statistics》2006,13(1):11-23
Response surface methodology, often supported by factorial designs, is the classical experimental approach that is widely
accepted for detecting and characterizing interactions among chemicals in a mixture. In an effort to reduce the experimental
effort as the number of compounds under study is increased, ray designs have been proposed to study combinations of chemicals.
When interest is restricted to relevant mixing ratios, we are only interested in making inference along the specific rays
of interest, as opposed to methods which use designs that require more experimental effort to support the estimation of a
response surface over a broader experimental region. Methods have been developed for the test of additivity along multiple
fixed-ratio rays. Of primary importance is the detection of interactions with reasonable power. The objective of this paper
is to address power and sample size issues related to the hypothesis of no interaction. 相似文献
870.
Dietrich von Holst Hans Hutzelmeyer Paul Kaetzke Martin Khaschei Heiko G. Rödel Hannelore Schrutka 《Behavioral ecology and sociobiology》2002,51(3):245-254
Wild European rabbits of both sexes have separate linear rank orders, which are established and maintained by intensive fights. This paper presents data from a 14-year study (1987-2000) on the population physiology and behavioural ecology of wild rabbits living in a 22,000 m2 enclosure and focuses on the relationship between social rank and reproduction in females. Group composition, social ranks, fecundity and reproductive success were known for all females (n=197) from the outset of their first reproductive season at an age of about 300 days until their death. The annual reproductive success of females was influenced to a large extent by their social rank. This depended on two effects of about equal strength: a higher fecundity of high-ranking females and a lower mortality of their offspring between birth and adulthood. The lifetime reproductive success of the females varied greatly. Only about 50% of all females had any reproductive success (range: on to nine adult offspring). The social rank achieved by the females during their first reproductive season substantially influenced their lifetime reproductive success: The mean reproductive lifespan and lifetime fitness of high-ranking females (ranks 1 and 2) was about 60% greater than that of lower-ranking females, although many of the latter also gained dominant positions in subsequent years. 相似文献