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161.
Asexual reproduction by external budding in Homoscleromorpha is reported for the first time. Two Mediterranean sponge species
were studied, Oscarella lobularis and O. tuberculata. Buds are formed in the marginal basal part of sponge. Budding takes from 1 to 4 days and is defined in three budding stages.
First, small irregular protuberances, consisting of external parental tissue, are formed. Second, they elongate and acquire
more regular, nipple-like shape. These protuberances are tube like, their internal cavity derived from parental exhalant canal.
The wall consists of three layers: (a) external layer is flagellated exopinacoderm, (b) internal one is flagellated endopinacoderm
and (c) intermediate one is a thin layer of mesohyl. Third, a spherical bud with a large central cavity is formed. During
budding, we did not observe cell proliferation or transdifferentiation either in budding zone or in any special mitotically
active region. The bud attached to the substrate is similar to the rhagon developing after larva metamorphosis, it has a syconoid
organization. Morphogenetically, budding in Oscarella differes from that in other sponges. Occurring by epithelial morphogenesis, it is similar to morphallaxis during regeneration.
The presence in Homoscleromorpha of an epithelial morphogenesis is unique among sponges. This feature is shared by Homoscleromorpha
and Eumetazoa. 相似文献
162.
Tran B. Nguyen Adam P. Bateman David L. Bones Sergey A. Nizkorodov Julia Laskin Alexander Laskin 《Atmospheric environment (Oxford, England : 1994)》2010,44(8):1032-1042
The chemical composition of secondary organic aerosol (SOA) generated from the ozonolysis of isoprene (C5H8) in the presence of an OH scavenger was examined using high-resolution electrospray ionization mass spectrometry (ESI-MS) in the mass range m/z = 50–1000. The chemical composition of SOA is complex, with more than 1000 assigned peaks observed in the positive and negative ion mode spectra. Only a small fraction of peaks correspond to known products of isoprene oxidation, such as pyruvic acid, glycolic acid, methylglyoxal, etc. The absolute majority of the detected peaks correspond to highly oxidized oligomeric constituents of SOA, with an average O:C molar ratio of 0.6. The corresponding organic mass (OM) to organic oxygen (OO) ratio is 2.4. Approximately 8% of oxygen atoms in SOA are in the form of peroxides, as quantified with an iodide test. Double bond equivalency (DBE) factors, representing the sum of all double bonds and rings, increase by 1 for every 1–2 additional carbon atoms in the molecule. The number of unoxidized CC double bonds is estimated to be less than 10%; the remaining DBE is due to CO carbonyl groups. Kendrick analysis suggests that the prevalent oligomer building blocks are small carbonyls with a C1–C2 skeleton. Formaldehyde (CH2O) is identified as the most common repetitive building block in the observed oligomeric compounds. 相似文献
163.
Kolesarova A Capcarova M Bakova Z Galik B Juracek M Simko M Sirotkin AV 《Journal of environmental science and health. Part. B》2011,46(3):207-212
The general objective of this in vitro study was to examine the effect of bee pollen on the release of insulin-like growth factor I (IGF-I) and steroid hormone progesterone, and expression of markers of proliferation (PCNA) and apoptosis (caspase-3) in porcine ovarian granulosa cells. Concentrations of IGF-I and progesterone were determined by RIA method and expression of PCNA and caspase-3 by immunocytochemistry. Bee pollen addition at the dose of 10 ng/mL significantly (P<0.05) inhibited IGF-I release by porcine ovarian granulosa cells. This growth factor was not influenced by 100 and 1000 ng/mL doses of bee pollen. Progesterone release by cells was not influenced by bee pollen addition at the doses of 10, 100 and 1000 ng/mL as used in our study. Similarly expression of PCNA and caspase-3 was not affected by bee pollen addition. The present study shows dose-dependent regulation of IGF-I by experimental bee pollen addition in vitro. Progesterone release, expression of PCNA and caspase-3 in porcine ovarian granulosa cells was not induced by pollen. Our results contribute to new insights regarding the possible effect of bee pollen on IGF-I release, which is important for regulation of porcine ovarian functions. 相似文献
164.
Facultative traits that have evolved under sexual selection, such as the acoustic ornaments present in the advertisement signals of male túngara frogs (Physalaemus pustulosus), offer a unique opportunity to examine selection for trait exaggeration with a focus on individual differences amongst signalers. By contrast, many studies of mate choice use experimental designs that obscure the inter-individual variation amongst signalers available for selection to act on—through the use of “typical” or average signals from the population. Here, we use dichotomous female phonotaxis choice tests to determine how the value of male call embellishment varies across 20 individual males frogs recorded from the wild—a sample which captures the acoustic diversity present in the population. We tested 20 females for each male call pair (i.e., 400 females). The results show widespread preference amongst females for ornamented calls (“whine–chucks”) over simple calls (“whines”), yet also demonstrate substantial variation in the relative benefits for individual male frogs—some males enjoy appreciable benefits by using ornaments while others (30% of males in this study) do not. We also show that the relative amplitude of the chuck to the whine correlates positively with the value of call elaborations across these 20 males. Finally, by manipulating the relative amplitude of whines and chucks using both natural and synthetic calls, we demonstrate directly that this single call parameter is key to determining the relative value of call elaborations across males. 相似文献
165.
R. Alexander Bentley Paul Ormerod Michael Batty 《Behavioral ecology and sociobiology》2011,65(3):537-546
Darwinian studies of collective human behaviour, which deal fluently with change and are grounded in the details of social influence among individuals, have much to offer “social” models from the physical sciences which have elegant statistical regularities. Although Darwinian evolution is often associated with selection and adaptation, “neutral” models of drift are equally relevant. Building on established neutral models, we present a general, yet highly parsimonious, stochastic model, which generates an entire family of real-world, right-skew socio-economic distributions, including exponential, winner-take-all, power law tails of varying exponents, and power laws across the whole data. The widely used Barabási and Albert (1999) Science 286: 509-512 “B-A” model of preferential attachment is a special case of this general model. In addition, the model produces the continuous turnover observed empirically within these distributions. Previous preferential attachment models have generated specific distributions with turnover using arbitrary add-on rules, but turnover is an inherent feature of our model. The model also replicates an intriguing new relationship, observed across a range of empirical studies, between the power law exponent and the proportion of data represented in the distribution. 相似文献
166.
Colles A Koppen G Hanot V Nelen V Dewolf MC Noël E Malisch R Kotz A Kypke K Biot P Vinkx C Schoeters G 《Chemosphere》2008,73(6):907-914
Persistent organic pollutants (POPs) are chemicals that accumulate in the food chain and are toxic to humans and wildlife. The fourth World Health Organization (WHO) survey on POP levels in human milk (2006-2009) aims to provide baseline and trend information on human exposure to POPs. So far Belgium participated in all three previous rounds (1988, 1992, 2001). Whereas the first three rounds focused on determination of dioxins and PCBs in pooled (mixed) samples, the fourth survey comprised the analyses of individual milk samples for nine "basic POPs" (chlorinated pesticides and indicator PCBs) and of pooled milk samples for "basic POPs", "advanced POPs" (dioxins and dioxin-like PCBs) and "optional POPs" (polybrominated diphenylethers [PBDEs], polybrominated dioxins and dibenzofurans [PBrDD/F], mixed halogenated dioxins and dibenzofurans [PXDD/F] and hexabromocyclododecane [HBCD]). For the Belgian participation human milk samples were collected during the summer of 2006 from 197 women between 18 and 30 years old distributed over all Belgian provinces. The individual samples were analyzed in a Belgian Laboratory for "basic" POPs. A pooled sample was made from 178 individual samples and analyzed by the WHO Reference Laboratory for the "basic, advanced and optional" POPs. The results indicate that most organochlorinated pesticides banned 25-30 years ago were below or around detection limits in Belgian human milk samples although DDE was still found at low levels in all samples. Over the last five years the levels of marker PCBs and PCDD/Fs in Belgian human milk decreased, respectively, by 58% and 39%. For some of the other emerging or older compounds recent international data are needed to allow comparison. This shows the importance of international studies as run by WHO. 相似文献
167.
Ksenya V. Mjachina Chris. W. Baynard Alexander A. Chibilyev Robert D. Richardson 《国际发展与全球生态学杂志》2018,25(6):541-553
Exploration and development of oil and gas (O&G) energy resources can create large-scale and permanent landscape effects that are best measured and understood via fieldwork and geospatial technologies. In this article, we examine O&G surface disturbance in the Orenburg steppe region of southwestern Russia for the year 2015. Utilizing field surveys, remote-sensing data and geographic information system (GIS) techniques, we apply a two-pronged approach. First, we map and measure the landscape infrastructure footprint (LIF) to determine the pattern and extent of direct surface disturbance created by O&G facilities and access roads. Second, we conduct a site suitability analysis to identify specific O&G production locations that are most vulnerable to environmental degradation. The approach considers both the particular properties of hydrocarbon production and specific natural features of steppe zones. Suitability patterns represent three indicators: two morphometric parameters (slope and aspect) and one spatial (the remoteness of O&G objects from water bodies). Our findings suggest that O&G production disturbs just over 3% of soil-vegetation cover in our study plot, while more than 13% of O&G objects are located in unsuitable zones based on topographic aspect, and about 11% lie in unsuitable zones regarding distance to water. 相似文献
168.
Ruben Kos’yan Sergey Kuklev Boris Khanukaev Alexander Kochergin 《Journal of Coastal Conservation》2012,16(3):243-250
The seacoasts protection does not stand standard solutions. Every part of a shore needs to be creatively approached and its hydrodynamic, lithodynamic, geological, geomorphological and other peculiarities must be thoroughly studied for each particular situation. It takes a complex scientific approach considering not only local features, but also the reaction of the whole lithodynamic system in limits of which the coast protective activity is planned with consideration of calculated hydrodynamic parameters (waves, sea level, etc.). 相似文献
169.
Alexander D. M. Wilson Emily M. Whattam Rachel Bennett Laksanavadee Visanuvimol Chris Lauzon Susan M. Bertram 《Behavioral ecology and sociobiology》2010,64(5):703-715
Recently, there has been increasing interest in behavioral syndrome research across a range of taxa. Behavioral syndromes
are suites of correlated behaviors that are expressed either within a given behavioral context (e.g., mating) or between different
contexts (e.g., foraging and mating). Syndrome research holds profound implications for animal behavior as it promotes a holistic
view in which seemingly autonomous behaviors may not evolve independently, but as a “suite” or “package.” We tested whether
laboratory-reared male and female European house crickets, Acheta domesticus, exhibited behavioral syndromes by quantifying individual differences in activity, exploration, mate attraction, aggressiveness,
and antipredator behavior. To our knowledge, our study is the first to consider such a breadth of behavioral traits in one
organism using the syndrome framework. We found positive correlations across mating, exploratory, and antipredatory contexts,
but not aggression and general activity. These behavioral differences were not correlated with body size or condition, although
age explained some of the variation in motivation to mate. We suggest that these across-context correlations represent a boldness
syndrome as individual risk-taking and exploration was central to across-context mating and antipredation correlations in
both sexes. 相似文献
170.
Alexander D. M. Wilson Robert L. McLaughlin 《Behavioral ecology and sociobiology》2010,64(11):1905-1914
Recently emerged brook charr (Salvelinus fontinalis) foraging in still-water pools along the sides of streams are either active, feeding on insects from the upper portion of
the water column away from the stream bank, or sedentary, feeding on crustaceans emerging from the hyporheic zone near the
stream bank. We tested whether the frequency of movement displayed by individual brook charr searching for prey in the field
was related to the relative volume of the telencephalon, a brain region involved with movement and space use in fishes. Movement
of individuals searching for prey was quantified in the field, individuals were captured and volumes of the telencephalon
and of the olfactory bulbs, a brain region neighbouring the telencephalon but not implicated in space use, were measured.
Individuals with larger telencephalon volumes moved more frequently on average while searching for prey in the field than
did individuals with smaller telencephalon volumes. The frequency of movement was unrelated to differences in the volume of
the olfactory bulbs, suggesting that the relationship between telencephalon volume and movement was not a consequence of differences
in overall brain size. Demonstrating a correlation between foraging behaviour and brain morphology for brook charr exhibiting
different foraging tactics suggests that diversification in brain structure and function could be important aspects of the
foraging specialization believed to occur during early stages in the evolution and development of resource polymorphisms. 相似文献