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191.
Lifjeld JT Kleven O Jacobsen F McGraw KJ Safran RJ Robertson RJ 《Behavioral ecology and sociobiology》2011,65(9):1687-1697
When males become more ornamented and reproduce more successfully as they grow older, phenotypic correlations between ornament
exaggeration and reproductive success can be confounded with age effects in cross-sectional studies, and thus say relatively
little about sexual selection on these traits. This is exemplified here in a correlative study of male fertilization success
in a large colony of American barn swallows (Hirundo rustica erythrogaster). Previous studies of this species have indicated that two sexually dimorphic traits, tail length and ventral plumage coloration,
are positively correlated with male fertilization success, and a mechanism of sexual selection by female choice has been invoked.
However, these studies did not control for potential age-related variation in trait expression. Here, we show that male fertilization
success was positively correlated with male tail length but not with plumage coloration. We also show that 1-year-old males
had shorter tails and lower fertilization success than older males. This age effect accounted for much of the covariance between
tail length and fertilization success. Still, there was a positive relationship between tail length and fertilization success
among older males. But as this group consisted of males from different age classes, an age effect may be hidden in this relationship
as well. Our data also revealed a longitudinal increase in both tail length and fertilization success for individual males.
We argue that age-dependent ornament expression and reproductive performance in males complicate inferences about female preferences
and sexual selection. 相似文献
192.
193.
This paper presents a mathematical model to investigate type II profile of suspension concentration distribution (i.e., the concentration profile where the maximum concentration appears at some distance above the bed surface) in a steady, uniform turbulent flow through open-channels. Starting from the mass and momentum conservation equations of two-phase flow, a theoretical model has been derived. The distribution equation is derived considering the effects of fluid lift force, drag force, particle inertia, particle–particle interactions, particle velocity fluctuations and drift diffusion. The equation is solved numerically and is compared with available experimental data as well as with other models existing in the literature. Good agreement between the observed value and computed result, and minimum error in comparison to other models indicate that the present model can be applied in predicting particle concentration distribution for type II profile for a wide range of flow conditions. The proposed model is also able to show the transition from type I profile to type II profile. 相似文献
194.
Dror Hawlena 《Behavioral ecology and sociobiology》2009,64(2):205-213
Colorful tails that become cryptic during ontogeny are found in diverse taxa. Nevertheless, the evolutionary bases for this
change remain debated. Recent work suggests that colorful tails, deflective displays, and striped patterns may represent antipredator
mechanisms used by immature lizards to compensate for being more active and hence more vulnerable to predation (increased
movement hypothesis, IMH). I challenged the generality of IMH by comparing foraging behavior and frequency of tail displays
across five Acanthodactylus lizards that vary in fundamental life history traits, before and after the tail changed color. As these species underwent
changes in tail coloration, they congruently adopted less risky behaviors and reduced the frequencies of tail displays. Contrary
to expectation, in two species, the hatchling risky behavior resulted not from increased movements but from longer stay in
exposed microhabitats. I suggest that colorful tails and deflective tail displays are synergistic antipredator mechanisms
neonates use to minimize the fitness consequences of using various risky behaviors rather than increased movement alone. 相似文献
195.
Cornelia Meinert Emma Schymanski Eberhard Küster Ralph Kühne Gerrit Schüürmann Werner Brack 《Environmental science and pollution research international》2010,17(4):885-897
Background, aim and scope
The importance of groundwater for human life cannot be overemphasised. Besides fulfilling essential ecological functions, it is a major source of drinking water. However, in the industrial area of Bitterfeld, it is contaminated with a multitude of harmful chemicals, including genotoxicants. Therefore, recently developed methodologies including preparative capillary gas chromatography (pcGC), MOLGEN-MS structure generation and mutagenicity prediction were applied within effect-directed analysis (EDA) to reduce sample complexity and to identify candidate mutagens in the samples. A major focus was put on the added value of these tools compared to conventional EDA combining reversed-phase liquid chromatography (RP-LC) followed by GC/MS analysis and MS library search. 相似文献196.
Process,Characterization and Biodegradability of Aliphatic Aromatic Polyester/Sisal Fiber Composites
Chin-San Wu 《Journal of Polymers and the Environment》2011,19(3):706-713
The biodegradability, morphology, and mechanical properties of composite materials made of Poly(butylene adipate-co-terephthalate) (PBAT) and sisal fiber (SF) were evaluated. Composites containing acrylic acid-grafted PBAT (PBAT-g-AA/SF)
exhibited noticeably superior mechanical properties due to greater compatibility between the two components. The dispersion
of SF in the PBAT-g-AA matrix was highly homogeneous as a result of ester formation between the carboxyl groups of PBAT-g-AA
and hydroxyl groups in SF and the consequent creation of branched and cross-linked macromolecules. Each composite was subjected
to biodegradation tests in Rhizopus oryzae compost. Morphological observations indicated severe disruption of film structure after 60 days of incubation, and both the
PBAT and the PBAT-g-AA/SF composite films were eventually completely degraded. Water resistance of PBAT-g-AA/SF was higher
than that of PBAT/SF, although weight loss of composites buried in Rhizopus oryzae compost indicated that both were biodegradable, even at high levels of SF substitution. The PBAT-g-AA/SF films were more
biodegradable than those made of PBAT, implying a strong connection between these characteristics and biodegradability. 相似文献
197.
Awareness of farm animal welfare issues is growing in Canada, as part of a larger food movement. The baseline Canadian standards
for farm animal welfare—the Recommended Codes of Practice for the Care and Handling of Farm Animals—are up for revision. The success of these standards will depend in part on perceived legitimacy, which helps determine whether
voluntary code systems are adopted, implemented, and accepted by target audiences. In the context of the Codes, legitimacy
will also hinge on whether the standards-developers marshal narratives about farm animals that accord with their audiences’
expectations. The aim of this paper is to catalogue factors that influence legitimacy in farm animal welfare standard-setting,
including which narratives of animal welfare are emphasized by standard-setters. Drawing upon the example of the baseline
Canadian standards, and the National Farm Animal Care Council, the paper will present a theoretical and methodological framework
for analyzing legitimacy in the context of animal welfare standards-development and discuss associated policy considerations. 相似文献
198.
A 2D analytical turbulent diffusion model for particle dispersion and deposition at different heights along the pipe flow
and circumferential deposition has been developed. This liquid–solid turbulent diffusion model presented in this paper has
emanated from an existing gas–liquid turbulent diffusion model. This model can be used as a handy tool for quick estimation
one and two-dimensional deposition fluxes of particles in water distribution networks. A comprehensive 3D numerical investigation
has been carried out using multiphase mixture model available in “Fluent 6.2” to verify the above analytical model. Different
particles sizes and densities were used for 3D numerical investigations. The deposition was studied as a function of particle
diameter, density, and fluid velocity. The deposition of particles, along the periphery of the pipe wall and at different
depths, was investigated. Both the models findings matched with qualitative phenomena such as deposition of heavier particles
at the bottom of the pipe wall were higher at lower velocities and lower at higher velocities. The lighter particles were
found mostly suspended with homogeneous distribution. Smaller particles were also suspended with marginal higher concentration
near the bottom of the pipe wall. This marginal higher concentration of the smaller particles was found to be slightly pronounced
for lower velocity. These analogies of particles are well discussed with the ratio between free-flight velocity and the gravitational
settling velocity. Extended analytical model results were compared with the 3D computational fluid dynamics simulation results.
Discrepancies in the model results were discussed. 相似文献
199.
200.