全文获取类型
收费全文 | 154篇 |
免费 | 6篇 |
出版年
2022年 | 1篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2017年 | 2篇 |
2016年 | 1篇 |
2015年 | 6篇 |
2014年 | 7篇 |
2013年 | 6篇 |
2012年 | 10篇 |
2011年 | 13篇 |
2010年 | 8篇 |
2009年 | 10篇 |
2008年 | 11篇 |
2007年 | 7篇 |
2006年 | 10篇 |
2005年 | 10篇 |
2004年 | 4篇 |
2003年 | 11篇 |
2002年 | 6篇 |
2001年 | 11篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1903年 | 1篇 |
排序方式: 共有160条查询结果,搜索用时 203 毫秒
1.
2.
Angela Schwarm Sylvia Ortmann Christian Wolf W. Jürgen Streich Marcus Clauss 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2009,152(4):504-512
The digestion of plant material in mammalian herbivores basically depends on the chemical and structural composition of the diet, the mean particle size to which the forage is processed, and the ingesta retention time. These different factors can be influenced by the animal, and they can presumably compensate for each other. The pygmy hippopotamus, a non-ruminating foregut fermenter, has longer mean retention times than ruminants; however hippos do not achieve higher (fibre) digestibilities on comparable diets, which could be due to ineffective mastication. We performed feeding trials with six pygmy hippos (Hexaprotodon liberiensis) and six banteng cattle (Bos javanicus) on a grass diet. As predicted, both species achieved similar dry matter, organic matter, crude protein and gross energy digestibilities. However, neutral and acid detergent fibre digestibility was lower in pygmy hippos. Apparently, in these species, fibre digestibility was more influenced by particle size, which was larger in pygmy hippos compared to banteng, than by retention time. In spite of their higher relative food intake, the banteng in this study did not have greater relative gut fills than the hippos. Ruminants traditionally appear intake-limited when compared to equids, because feed particles above a certain size cannot leave the rumen. But when compared to nonruminating foregut fermenters, rumination seems to free foregut fermenters from an intrinsic food intake limitation. The higher energy intakes and metabolic rates in wild cattle compared to hippos could have life-history consequences, such as a higher relative reproductive rate. 相似文献
3.
Marcus Clauss Julia Fritz Dorothee Bayer Jürgen Hummel W. Jürgen Streich Karl-Heinz Südekum Jean-Michel Hatt 《Zoology (Jena, Germany)》2009,112(3):195-205
In domestic ruminants, the stratification of forestomach contents – the results of flotation and sedimentation processes – is an important prerequisite for the selective particle retention in this organ. A series of anatomical and physiological measurements suggests that the degree of this stratification varies between browsing and grazing wild ruminants. We investigated the forestomach contents of free-ranging mouflon and roe deer shot during regular hunting procedures. There was no difference between the species in the degree by which forestomach ingesta separated according to size due to buoyancy characteristics in vitro. However, forestomach fluid of roe deer was more viscous than that of mouflon, and no difference in moisture content was evident between the dorsal and the ventral rumen in roe deer, in contrast to mouflon. Hence, the forestomach milieu in roe deer appears less favourable for gas or particle separation due to buoyancy characteristics. These findings are in accord with notable differences in forestomach papillation between the two species. In roe deer, particle separation is most likely restricted to the reticulum, whereas in mouflon, the whole rumen may pre-sort particles to a higher degree. The results suggest that differences in forestomach physiology may occur across ruminant species. 相似文献
4.
Marcus Clauss Jürgen Hummel W. Jürgen Streich 《European Journal of Wildlife Research》2006,52(2):88-98
Whether differences in digestive physiology exist between different ruminant feeding types has been an ongoing debate. In
this regard, potential differences in ingesta retention have been understood to be of particular importance. We analyzed a
data pool in which only mean retention time (MRT) data for the ruminoreticulum (RR) were collated that were obtained using
comparable techniques with either chromium or cobalt EDTA as a fluid marker and/or with chromium-mordanted fiber of less than
2 mm in size as a particle marker. Data were compared using one averaged value per species. In general, the paucity of species
in such a collection is striking and does not allow—in contrast to earlier statements—any final conclusions regarding the
influence of body weight (BW) or feeding type on ruminant MRTs. In particular, there was no significant correlation between
MRTparticlesRR or MRTfluidRR and BW, neither in the interspecific nor in the intraspecific comparisons, and no difference between the feeding types.
The trend that indicates longer MRTparticlesRR in grazers is based on too few species to be conclusive. Small browsers seemed to have shorter MRTfluidRR than similar-sized grazers. In contrast, there was a trend for large grazers to have shorter MRTfluidRR than large browsers. In direct pair-wise comparisons between cattle and the browsers giraffe, moose, and okapi, the latter
difference was significant. Cattle also had the highest relative RR fluid outflow rates among the species investigated. This
is in accord with the observation that grazers have larger omasa, a major function of which is water-reabsorption distal to
the RR. Grazers seem to have longer MRTparticlesRR per unit MRTfluidRR, and cattle are particular outliers in this respect. It is hypothesized that potentially shorter MRTfluidRR in large grazers and higher relative outflow rates are linked to a higher saliva production and a lesser viscosity of both
saliva and RR fluids. A constant supply of a fluid phase of low viscosity is proposed to be the prerogative for the physical
mechanisms of flotation and sedimentation that result in the stratification of RR contents and its selective particle retention
typical for large grazing species. 相似文献
5.
6.
Shuangshuang Liu Jared Streich Justin O. Borevitz Kevin J. Rice Tingting Li Bo Li Kent J. Bradford 《Oikos》2019,128(2):171-184
Intraspecific trait variation within natural populations (i.e. intra‐population trait variation, IPTV) is the basic source for selection and can have significant ecological consequences. Higher IPTV may increase a population's niche breath and benefit interspecies competition under a resource‐limited environment, thus affecting the ability of a species to move into novel habitats. However, the reciprocal influences of variation in environmental conditions and phenotypic trait expression in spreading plant populations are not clearly defined. We propose that during invasion, IPTV and its relative change in response to key resource enrichment may increase with the resource deficit of invaded sites, and that this relationship may facilitate plant invasions into resource‐limited environments. We analyzed the invasion trend, IPTV and its response to water enrichment, and moisture variability among populations of an annual grass Brachypodium hybridum in California, United States. We incorporated a genotyping‐by‐sequencing approach, a common garden experiment that had two water level treatments, and public plant and climate databases. Our hypothesis was supported by the observation that for populations that invaded sites with higher spring moisture deficit, both their seed biomass IPTV (for the water‐enriched treatment only) and relative change of the IPTV across water treatments were larger when examined in the common garden experiment. A generally north to south spreading direction was found in these B. hybridum populations, towards a drier and warmer climate exhibiting higher moisture deficit for plant growth. Our results suggest a role for interactions between IPTV (rather than trait means) and environmental resource availability in promoting plant invasions, providing new insights into the significance of IPTV in shaping plant geographic distributions. 相似文献
7.
Marcus Clauss Reinhold R. Hofmann Jörns Fickel W. Jürgen Streich Jürgen Hummel 《Journal of morphology》2009,270(8):929-942
Browsing and grazing ruminants are thought to differ in the degree their rumen contents are stratified—which may be due to different characteristics of their respective forages, to particular adaptations of the animals, or both. However, this stratification is difficult to measure in live animals. The papillation of the rumen has been suggested as an anatomical proxy for stratification—with even papillation indicating homogenous contents, and uneven papillation (with few and small dorsal and ventral papillae, and prominent papillae in the atrium ruminis) stratified contents. Using the surface enlargement factor (SEF, indicating how basal mucosa surface is increased by papillae) of over 55 ruminant species, we demonstrate that differences between the SEFdorsal or SEFventral and the SEFatrium are significantly related to the percentage of grass in the natural diet. The more a species is adapted to grass, the more distinct this difference, with extreme grazers having unpapillated dorsal and ventral mucosa. The relative SEFdorsal as anatomical proxy for stratification, and the difference in particle and fluid retention in the rumen as physiological proxy for stratification, are highly correlated in species (n = 9) for which both kind of data are available. The results support the concept that the stratification of rumen contents varies among ruminants, with more homogenous contents in the more browsing and more stratified contents in the more grazing species. J. Morphol., 2009. © 2009 Wiley‐Liss, Inc. 相似文献
8.
A. Berger K. -M. Scheibe A. Brelurut F. Schober W. J. Streich 《Biological Rhythm Research》2002,33(3):237-253
To describe the normal rhythmic behavioural patterns and to test procedures for the detection of short-time disturbances, 4 red deer were studied in 2 quasi-natural enclosures. Activity and feeding were recorded by means of the storage-telemetrysystem ETHOSYS®. Daily and monthly mean values, power spectra and 'Degrees of Functional Coupling' (DFC) were calculated. DFC were applied to measure stability and harmonic synchronisation between ultradian rhythms and the 24-hours period. The general patterns of activity and feeding were nearly identical in all animals and closely related to photoperiod change. Levels of total activity and feeding were lowest in winter and highest in summer. In winter highest activity was generally observed in daylight hours and shifted gradually to dark hours in summer. Spectral analysis of activity and feeding revealed a time pattern in which ultradian components, between 4.8 and 12 hrs in period length, mostly exceeded the diurnal rhythm power. Compared to winter higher frequencies were found in activity and feeding in spring, summer and autumn. During such periods up to 8 strong bouts of activity per day (3-hrs rhythm) were observed. These rhythmic patterns are discussed in the context of red deer feeding strategy. Short-term disturbances by humans and changing feeding conditions resulted in lowered DFCs. Time pattern analysis of long-term and continuously measured behavioural parameters proved to be an appropriate approach for observing general living conditions and for detecting disturbances. 相似文献
9.
Marcus Clauss Matthias Lechner-Doll Anke Behrend Karin Lason Denise Lang Wolf J. Streich 《Acta theriologica》2001,46(1):103-107
A combination of a flotation/sedimentation experiment and sieve analysis for the reticulorumen (RR) contents of roe deerCapreolus capreolus Linnaeus, 1758, a browsing ruminant, showed that there was no correlation between particle size and particle density. Large particles were present in both the sedimented and the buoyant fraction, which is in accord with the reported absence of stratification of RR contents in browsing ruminants. Comparative sieve analysis of roe deer RR and caecal/rectal material demonstrated that there must be some selective particle retention in the browsing ruminant as well, as a certain fraction of large particles in RR contents does not occur in the caecal/rectal material. These results lead to the explanatory dilemma that, while selective particle retention is observed, it cannot be due to the mechanisms known to work in grazing ruminants. 相似文献
10.
Hanna W van Steenbergen Jessica AB van Nies Tom WJ Huizinga Monique Reijnierse Annette HM van der Helm-van Mil 《Arthritis research & therapy》2014,16(2):R92