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1.
We examine the relationship of the inbreeding coefficient (f) and molecular estimates of inbreeding (IR, sMLH) in the Icelandic sheepdog. The breed experienced a severe genetic bottleneck and near extinction in the last century. Molecular estimates and the inbreeding coefficient are significantly correlated despite the moderate number of markers and individuals used in this study. This is most likely an effect of the extreme relatedness and relatively high variance in individual inbreeding coefficients in the population. There is a significant relationship between inbreeding (f) and the occurrence of hip dysplasia. However, the molecular measures did not detect hip dysplasia as an inbreeding effect.  相似文献   
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Abstract:  The exceptionally preserved hyolithids Gompholites striatulus , Maxilites robustus , Maxilites snajdri and Maxilites sp. are described with particular emphasis on helen and muscle scar morphology. These two aspects of hyolithid morphology have remained controversial. In life position, each helen curved ventrally. When the operculum closed the aperture of the conch, each helen was locked at the commissure slit with its dorsal edge tilted forward. Inside the conch, it was held in the dorsal apertural plane and clear of the inner surface of the operculum. Previously unidentified muscle scars are described from both the operculum and the conch. Dorsal scars on the conch aperture held muscles directed to the operculum. Comparative study of the muscle insertion pattern indicates that hyolithids did not have serially arranged muscles and that all hyolithids may have had a common skeleto-muscular system. The arrangement of the muscle scars with respect to the helens suggests that the latter were capable of relatively complex movements and could have been used to propel the organism over the substrate. The general morphology and orientation of the helens suggests that in addition they functioned to stabilize the organism on the sea-floor.  相似文献   
3.
1. The objective was to identify the factors driving spatial and temporal variation in annual production (PA) and turnover (production/biomass) ratio (P/BA) of resident brown trout Salmo trutta in tributaries of the Rio Esva (Cantabrian Mountains, Asturias, north‐western Spain). We examined annual production (total production of all age‐classes over a year) (PA) and turnover (P/BA) ratios, in relation to year‐class production (production over the entire life time of a year‐class) (PT) and turnover (P/BT) ratio, over 14 years at a total of 12 sites along the length of four contrasting tributaries. In addition, we explored whether the importance of recruitment and site depth for spatial and temporal variations in year‐class production (PT), elucidated in previous studies, extends to annual production. 2. Large spatial (among sites) and temporal (among years) variation in annual production (range 1.9–40.3 g m?2 per year) and P/BA ratio (range 0.76–2.4 per year) typified these populations, values reported here including all the variation reported globally for salmonids streams inhabited by one or several species. 3. Despite substantial differences among streams and sites in all production attributes, when all data were pooled, annual (PA) and year‐class production (PT) and annual (P/BA) and year‐class P/BT ratios were tightly linked. Annual (PA) and year‐class production (PT) were similar but not identical, i.e. PT = 0.94 PA, whereas the P/BT ratios were 4 + P/BA ratios. 4. Recruitment (Rc) and mean annual density (NA) were major density‐dependent drivers of production and their relationships were described by simple mathematical models. While year‐class production (PT) was determined (R2 = 70.1%) by recruitment (Rc), annual production (PA) was determined (R2 = 60.3%) by mean annual density (NA). In turn, variation in recruitment explained R2 = 55.2% of variation in year‐class P/BT ratios, the latter attaining an asymptote at P/BT = 6 at progressively higher levels of recruitment. Similarly, variations in mean annual density (NA) explained R2 = 52.1% of variation in annual P/BA, the latter reaching an asymptote at P/BA = 2.1. This explained why P/BT is equal to P/BA plus the number of year‐classes at high but not at low densities. 5. Site depth was a major determinant of spatial (among sites) variation in production attributes. All these attributes described two‐phase trajectories with site depth, reaching a maximum at sites of intermediate depth and declining at shallower and deeper sites. As a consequence, at sites where recruitment and mean annual density reached minimum or maximum values, annual (PA) and year‐class production (PT) and annual (P/BA) and year‐class P/BT ratios also reached minimum and maximum values.  相似文献   
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5.
Leaf longevity and nutrient resorption efficiency are important strategies to conserve plant nutrients. Theory suggests a negative relationship between them and also proposes that high concentration of phenolics in long‐lived leaves may reduce nutrient resorption. In order to provide new evidence on these relationships, we explored whether N‐resorption efficiency is related to leaf longevity, secondary compounds and other leaf traits in coexisting plant species of different life forms in the arid Patagonian Monte, Argentina. We assessed N‐resorption efficiency, green leaf traits (leaf mass per area (LMA), leaf longevity and lignin, total soluble phenolics and N concentrations) and N concentration in senescent leaves of 12 species of different life forms (evergreen shrubs, deciduous shrubs and perennial grasses) with contrasting leaf traits. We found that leaf longevity was positively correlated to LMA and lignin, and negatively correlated to N concentration in green leaves. N concentrations both in green and senescent leaves were positively related. N‐resorption efficiency was not associated with the concentration of secondary compounds (total soluble phenolics and lignin) but it was negatively related to LMA and leaf longevity and positively related to N concentration in green leaves. Furthermore, leaf traits overlapped among life forms highlighting that life forms are not a good indicator of the functional properties (at least in relation to nutrient conservation) of species. In conclusion, our findings indicated that differences in N‐resorption efficiency among coexisting species were more related to N concentration in green leaves, leaf lifespan and LMA than to the presence of secondary compounds at least those assessed in our study (soluble phenolics and lignin). Accordingly, N‐resorption efficiency seems to be modulated, at least in part, by the productivity–persistence trade‐off.  相似文献   
6.
    
Abstract: The ‘perleidiform’Mendocinichthys and Pseudobeaconia from the Potrerillos and Santa Clara Abajo formations (Upper Triassic; Argentina) are reviewed. Mendocinichthys has been known from a review of this species that is not based on the type material, but on referred specimens in the American Museum of Natural History. However, those specimens are found here to represent a new species of Pseudobeaconia, Pcelestae sp. nov. Consequently, Mendocinichthys is restricted here to the type material and, within it, to the only specimen that clearly represents a distinct taxon and is thus designated lectotype. We further performed a cladistic analysis and propose a new family, Pseudobeaconiidae for these two South American Triassic genera, which is mainly characterized by the presence of an incomplete dorsal ridge of spine‐like scales between the skull and the dorsal fin, and scales with straight posterior border, an elevated central region and marginal concentric ridges of ganoine. The cladistic analysis further indicates the existence of some lineages endemic to certain areas of Gondwana and Europe. Pseudobeaconia celestae sp. nov. represents the first record of Pseudobeaconia in the Cacheuta sub‐basin of the Cuyana Basin. The genus was previously known from the Santa Clara sub‐basin of the Cuyana Basin only, and the new record confirms the previous hypothesis of correlation between the sedimentary infilling of these sub‐basins.  相似文献   
7.
    
Increased understanding of the species–area relationship (SAR) can improve its usefulness as a tool for prediction of species loss for biodiversity conservation targets. This study was conducted: (i) to determine the best plant attribute for the SAR in the community of arthropods living within the grass Muhlenbergia robusta; (ii) to determine the contribution of phenophases of plant foliage (dry and fresh), shade and conspecific distance to the variation in arthropod richness within the plant; (iii) to determine the best functional model of changes in the abundance, diversity and biomass in communities of arthropods in response to increases in plant size; (iv) to determine the best host‐plant attribute for prediction of these community attributes; and (v) to determine the effect of the plant phenophase, shade and M. robusta isolation on the abundance, diversity and biomass of the arthropod community. The above‐ground dry weight of grass was found to be the best host‐plant attribute for the SAR, while the light environment explained the arthropod richness within the grass, with higher richness observed in shaded environments. This study also showed that the best functional mathematical models for estimation of changes in the abundance, dry weight and diversity of arthropods in response to increases in grass size (dry weight) are the power model, exponential model and logarithmic model, respectively. Furthermore, the host‐plant foliage phenophase, shade and the isolation of M. robusta with other conspecifics had no effect on the abundance, biomass or diversity per basal area of the grass.  相似文献   
8.
Recent studies of female insects indicate that reproductive activities, such as mating and oviposition, can impair immune ability. Using the two tropical damselfly species Argia anceps Garrison and Hetaerina americana (Fabricius), egg production and phenoloxidase (PO) activity, a key enzyme in insect immunity, are measured in mating, ovipositing and perching females in December and March. Perching females of both species have fewer eggs compared with mating and ovipositing females, which suggests that perching females are not engaged in reproduction. There is seasonal variation in egg number for the three categories in H. americana but not in A. anceps, which can be interpreted in terms of adaptive changes in egg production depending on female–male interactions in the former species but not in the latter species. There is no difference in PO activity among mating, ovipositing or perching females within either species, although measurements in December and March indicate distinct seasonal changes. Juvenile Hormone (JH) is known to reduce the effectiveness of the immune system by favouring the use of resources for reproduction. A possible role for JH is examined in H. americana, using the JH analogue methoprene to manipulate hormone activity, revealing that PO activity is reduced in methoprene‐treated H. americana females. Thus, although the results of the present study are indicative of possible hormone‐driven changes in PO, there is not necessarily a down‐regulation of immune function (as determined by PO activity) during mating or oviposition. The results complement some recent studies countering the idea that reproductive activities reduce the immune ability in insects.  相似文献   
9.
Morphological variation of the Y chromosome has been observed in different populations. This variation is mostly related to the heteromorphic Yq12 band, which is composed of a variable block of constitutive heterochromatin. The Yqh+ heteromorphism has a worldwide frequency of 2.85% and is considered clinically innocuous. The aim of this study was to identify the ancestry of the Yqh+ heteromorphism present in individuals from western Mexico. For this purpose, 17 Y-chromosome single nucleotide polymorphisms were analysed by multiplex polymerase chain reaction and SNaPshot assays. In 28 Yqh+ males, only five haplogroups were observed; with a haplogroup diversity of 0.4841 ± 0.1094, which was less than that observed in a study of unselected Mexican mestizo population. Differences were specifically conferred by the high frequencies of haplogroups R1b1 and P*(xQ,R), and by the absence of the Amerindian haplogroup Q (Q*(xQ1a3a) plus Q1a3a) from the Yqh+ group. This study suggests a post-1492 incorporation for Yqh+ chromosomes into the Mexican northwestern population.  相似文献   
10.
    
Diplotaxini Kirby is one of the 29 tribes of Melolonthinae with Nearctic, Neotropical, Paleartic, Afrotropical and Oriental distribution. According to the current classification, Diplotaxini is composed of 706 species described in 21 genera. Neotropical Diplotaxini comprise 94 species, of which 78 are members of Liogenys Guérin Méneville, the largest Neotropical genus. Until now, no phylogenetic studies on Diplotaxini have tested whether the tribe is natural or artificial. This study tested the relationships among Diplotaxini genera, created hypotheses for better defining them, and assessed the monophyly of Liogenys. Cladistic analyses using 167 adult morphological characters were performed. The 83 included taxa represent three subfamilies of Melolonthidae, four tribes of Melolonthinae, and most genera of Diplotaxini, with emphasis on Liogenys. The data were analysed using parsimony under equal and implied weights. In both analyses, the traditional concept of Diplotaxini is shown to be a polyphyletic assemblage. Empecta Erichson and Clypeasta Fairmaire are closely related to Melolontha melolontha (Linnaeus) and Pseudoliogenys Moser close to Myloxenoides Martínez (Tanyproctini). Pachrodema Blanchard is identified as the sister group of Liogenys. The monophyly of both Pacuvia Curtis and Homalochilus Blanchard is confirmed and the paraphyly of Diplotaxis Kirby is suggested. The analyses strongly supported the polyphyly of Liogenys. To render this genus monophyletic, we transferred L. ferrugata Mannerheim (related to M. melolontha) to Phyllophaga Harris, and L. micropyga Burmeister to Diplotaxis, forming Diplotaxis micropyga (Burmeister, 1855) comb.n. ; and included Homoliogenys tarsalis (Moser) and Hilarianus anguliceps Blanchard in Liogenys. As H. anguliceps is syn. junior of Liogenys punctaticollis, Hilarianus is synonymized with Liogenys. Hilarianus ovalis and Hilarianus rufinus are here assigned to Manonychus, and Hilarianus uniformis and Hilarianus suboblongus to Blepharotoma, forming: Blepharotoma uniformis comb.n. , Blepharotoma suboblongus comb.n. , Manonychus ovalis comb.n. and Manonychus rufinus comb.n.  相似文献   
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