全文获取类型
收费全文 | 254篇 |
免费 | 5篇 |
国内免费 | 14篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 9篇 |
2021年 | 11篇 |
2020年 | 14篇 |
2019年 | 11篇 |
2018年 | 10篇 |
2017年 | 5篇 |
2016年 | 6篇 |
2015年 | 5篇 |
2014年 | 14篇 |
2013年 | 8篇 |
2012年 | 7篇 |
2011年 | 14篇 |
2010年 | 16篇 |
2009年 | 10篇 |
2008年 | 17篇 |
2007年 | 27篇 |
2006年 | 18篇 |
2005年 | 10篇 |
2004年 | 7篇 |
2003年 | 9篇 |
2002年 | 4篇 |
2001年 | 8篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有273条查询结果,搜索用时 31 毫秒
21.
Kagkli DM Vancanneyt M Vandamme P Hill C Cogan TM 《Journal of applied microbiology》2007,103(5):1393-1405
AIM: To determine the contribution of enterococci and coliforms from bovine faeces and teats to contamination of raw milk. Methods: Putative enterococci (n = 301) and coliforms (n = 365) were isolated from bovine faeces (n = 20), cows' teats (n = 20), the raw milk (n = 1) and the milking environment (n = 4) on one farm. The clonal relationships of each bacterial group were investigated using Pulsed-Field Gel Electrophoresis of genomic macrorestriction fragments. Representatives of the different clusters of enterococci were identified by molecular techniques including rep-PCR, SDS protein profiling, Fluorescent Amplified Fragment Length Polymorphism (FAFLP), phenylalanyl-tRNA synthase (pheS) sequence analysis and/or 16S rDNA gene sequencing. Coliforms were identified by API 20E strips. RESULTS: The majority of the bovine faecal enterococcal isolates were identified as a potential new species of Aerococcus (100 isolates); E. faecium (28 isolates), and Aerococcus viridans (28 isolates) were also found. All coliform isolates from the bovine faeces were identified as Escherichia coli. The coliforms present in the milk were Hafnia alvei, Serratia liquefaciens, Yersinia enterocolitica and Enterobacter amnigenus. No E. coli, Enterococcus or Aerococcus from the bovine faeces were found in the milk. A single clone of H. alvei was found in the water, the milking equipment and the milk, suggesting that the water was the source of the organism in the milk. No vancomycin-resistant aerococci or enterococci were found while most of the isolates tested showed the presence of at least one virulence gene. The milk-sock retained strains that adhered to particulate faecal material. Coliforms were present at approx. 2 orders of magnitude greater than enterococci in the bovine faeces. CONCLUSIONS: The results imply that bovine faeces are not an important source of contamination of raw milk with enterococci or coliforms. SIGNIFICANCE AND IMPACT OF THE STUDY: The results confirm those of two previous studies (Gelsomino et al. 2001, Int J Food Microbiol71, 177-188 and Kagkli et al. 2007, Int J Food Microbiol114, 243-251) on two other farms. The three studies show that contamination of milk by enterococci, lactobacilli and coliforms of bovine faecal origin is extremely low. The results also suggest that where raw milk is implicated in food infection, other factors in addition to faecal contamination must be involved. 相似文献
22.
Nitrogen outputs from fecal and urine deposition of small mammals: implications for nitrogen cycling 总被引:1,自引:0,他引:1
The contribution of small mammals to nitrogen cycling could have repercussions for the producer community in the maintaining
or perhaps magnifying of nitrogen availability. Our objective was to model nitrogen outputs (deposition of feces and urine)
of small mammals in an old-field ecosystem and estimate the amount of fecal and urinary nitrogen deposited annually. To address
this objective, we used models from laboratory studies and combined these with data from field studies to estimate dietary
nitrogen and monthly and annual nitrogen outputs from fecal and urine deposition of five rodent species. The models accounted
for monthly fluctuations in density and biomass of small-mammal populations. We estimated that the minimal amount of nitrogen
deposited by rodents was 1.0 (0.9–1.1) and 2.7 (2.6–2.9) kg Nha−1 year−1 from feces and urine, respectively, for a total contribution of 3.7 (3.5–4.0) kg Nha−1 year−1. Hispid cotton rats (Sigmodon hispidus) accounted for >75% of the total nitrogen output by small mammals. Our estimates of annual fecal and urinary nitrogen deposited
by rodents were comparable to nitrogen deposits by larger herbivores and other nitrogen fluxes in grassland ecosystems and
should be considered when assessing the potential effects of herbivory on terrestrial nitrogen cycles. 相似文献
23.
Seasonal changes in the composition of the diet of the sika deer population in the Shiranuka Hills, eastern Hokkaido, in 1998 were determined by fecal analyses. The deer were dependent on Sasa nipponica, a dwarf bamboo, throughout the year, particularly in winter when it accounted for as much as 77.7% of the diet. It accounted for 33.1% and 45.6% in spring and summer, respectively, and this decreased to 12.2% in autumn. Besides S. nipponica, all the graminoid categories accounted for large amounts (66–96.7%), while dicotyledonous plants accounted for little (3–8%) except in autumn when they accounted for 31%. The strong dependence of the Shiranuka population on graminoids was different from other Hokkaido deer populations, for example the population from Ashoro/Onbetsu and the extremely high density population on Nakanoshima Island. In spite of these differences, food for all Hokkaido sika deer was poor in winter. Along the north–south geographical cline in the food composition of sika deer along the Japanese archipelago, the Shiranuka population was positioned as a grazer type, in contrast to the southern populations. However, it is important to note that variations are great among local populations in Hokkaido. 相似文献
24.
Savannah baboons are one of the few mammalian species that do not exhibit seasonal reproduction patterns and are therefore ideally suited to study the effect of female reproductive states (cycling, pregnant, lactating) on cortisol levels independent of seasonal factors. Fecal samples from 10 free-ranging female chacma baboons (Papio hamadryas ursinus), collected during a period of 17 months, were analyzed using a steroid-extraction method. Reproductive state had a significant effect on fecal cortisol, with lowest levels found in estrous females. Fertility was not related to fecal cortisol levels; we found no significant differences between samples collected on conceptive and nonconceptive cycles. Environmental factors explained most of the variance of fecal cortisol levels. Cortisol measures were strongly correlated with seasonal differences such as daylight duration, temperature and the amount of time that baboons spent resting. We measured higher cortisol levels during winter months and suggest that this could be related to shorter resting periods and to the cold minimum ambient temperatures at this study site. Finally, we found no relationship between social rank nor the rate of agonistic interactions with basal fecal cortisol levels. 相似文献
25.
Impaired daily glucocorticoid rhythm in Per1
Brd
mice 总被引:1,自引:0,他引:1
Robert Dallmann Chadi Touma Rupert Palme Urs Albrecht Stephan Steinlechner 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2006,192(7):769-775
Biological clocks have evolved in all kinds of organisms in order to anticipate and adjust to the daily light–dark cycle. Within the last decade, the molecular machinery underlying the circadian system was unraveled. In the present study, the impact of the loss of the Per1 or Per2 genes, key components of the core clock oscillator, on body mass, food and water intake, glucose metabolism, and hypothalamic-pituitary-adrenal axis, was investigated in the Per1
Brd
and Per2
Brd
mouse models. The results reveal that the lack of Per1 but not Per2 has severe consequences for the regulation of these parameters. Specifically, in Per1
Brd
animals, we found an impaired daily glucocorticoid rhythm, with markedly elevated levels during the day compared to control animals. In addition, Per1
Brd
mice showed significant differences in body mass as well as food and water intake. Although the Per1
Brd
are lighter than wildtype mice, food and water intake per gram body mass is elevated. In addition, the Per1
Brd
mice exhibit an increased glucose metabolism after i.p. injection with glucose. In conclusion, our study presents first evidence for a link between an altered metabolism in Per1 and Per2 deficient mice, which in the case of the Per1
Brd
animals might be due to an impaired corticosterone rhythm. 相似文献
26.
The aim of the present study was to investigate the safety and efficacy of deslorelin, a GnRH agonist, implants in suppressing estrus behavior and matings in a controlled ambient environment in feline queens in the presence of a tomcat. Local and utero-ovarian side effects of deslorelin implants were also investigated. The queens were housed in groups and assigned to one of three treatments: group 1 received 9.5 mg deslorelin implants (N = 14), group 2 received 5 mg megestrol acetate tablets and 9.5 mg deslorelin implants (N = 7), and group 3 were given placebo implants (N = 7). All implants were placed subcutaneously cranial to the interscapular region under xylazine hydrochloride sedation. Ovarian activity was monitored by fecal estradiol (E2) analyses. The animals were observed daily and checked individually at three-day intervals for behavioral signs of estrus. After 18.5 mo of trial, queens were ovariohysterectomized, and ovaries and uteri were weighed and evaluated histologically. E2 levels were significantly lower in group 1 and 2 than in group 3 with an average of 128.48 ± 19.97 ng/g, 90.44 ± 7.16 ng/g and 283.26 ± 39.21 ng/g, respectively, excepting the first week of treatment. After inserting implants an initial estrus-like increase in fecal E2 concentrations occurred in all treated queens except one female in group 2. Ovarian and uterine weights were significantly different among the groups (P < 0.01), and were lowest in groups 1 and 2. Primordial and primary follicle numbers were significantly higher in groups 1 and 2 than in group 3 (P < 0.001). Endometrial gland, antral follicle, and corpus luteum (CL) numbers were highest in group 3 (P < 0.01, 0.001, and 0.001, respectively) compared with groups 1 and 2. Deslorelin implants successfully suppressed estrus behavior and E2 secretion in queens for 18.5 mo of the study period. Further investigations are needed to demonstrate the effects of GnRH agonists on ovarian interstitial tissue. 相似文献
27.
The diet of the Iberian hare (Lepus granatensis) was studied through microhistological pellet analysis in two areas from a mountain ecosystem in Central Portugal. Fecal
pellets were collected monthly in 24 plots spatially distributed throughout the two study areas. For each period, a sample
of 15 to 20 pellets was milled and 400 epidermal fragments were identified, by comparison with a reference collection. A wide
range of plant species was observed in hare’s diet. Grasses represent the basis of the Iberian hare diet, with frequencies
always higher than 50% in both study areas (annual average = 69.98%). Most of the 35 species of grasses assembled for the
reference collection (91.43%) were identified in the pellets. Nevertheless, only six of these were consumed in proportions
greater than 5%, being Anthoxanthum odoratum, Secale cereale and Agrostis spp. the species ingested in higher frequencies. The rate of grasses consumption reached 80.69% in winter but decreased in
summer to around 55%. In this season, a concurrent rise in the ingestion of other plant groups, like herbs and shrubs, and
of plant inflorescences was observed. This work provides the first results on the Iberian hare’s diet on mountain ecosystems,
and suggests that the Iberian hare diet in a mountain ecosystem is similar to the observed in L. europaeus and L. timidus. 相似文献
28.
Obestatin, a novel putative 23-amino acid peptide, was found to be derived from a mammalian preproghrelin gene by using a bioinformatics approach. Although the effects of obestatin on food intake and upper gut motility remain controversial, no studies have been carried out to explore its influence on lower gut motility and secretion. We investigated the impacts of intravenous (IV) injection of obestatin on rat colonic motor and secretory functions. Colonic transit time, fecal pellet output, and fecal content were measured in freely fed, conscious rats, which were chronically implanted with IV and colonic catheters. To test the validity of this animal model, human/rat corticotropin-releasing factor (h/rCRF) served as a stimulatory inducer of colonic motility and secretion. IV injection of obestatin (45, 100, and 300nmol/kg) did not affect the colonic transit time, whereas IV injection of h/rCRF (30nmol/kg) effectively accelerated colonic transit time. IV obestatin, in every dose we tested, also did not modify fecal pellet output, frequency of watery diarrhea, total fecal weight, fecal dried solid weight, or fecal fluid weight in the first hour after injection. On the other hand, IV injection of h/rCRF significantly enhanced fecal pellet output, as well as increased the frequency of watery diarrhea, total fecal weight, fecal dried solid weight, and fecal fluid weight during the first hour after injection compared with IV saline controls. In conclusion, peripheral obestatin administration has no impact on colonic motility and secretion in conscious fed rats. 相似文献
29.
Rodolfo Martínez-Mota Carolina Valdespino Juan Arturo Rivera Rebolledo Rupert Palme 《International journal of primatology》2008,29(5):1365-1373
Measuring fecal glucocorticoid metabolites is now a common practice to assess the stress response in primates. Nevertheless,
it is important to validate the utilized immunoassay for each primate species before the technique is applied to populations
in the wild. We determined the stress response of black howlers (Alouatta pigra) via 2 different group-specific enzyme immunoassays (EIAs). 11-oxoetiocholanolone EIAs are suited to assess the stress response
of black howlers via fecal glucocorticoid metabolites. Levels of fecal glucocorticoid metabolites increased after we applied
a stressor, i.e. anesthesia, reaching peak concentrations 24–96 h poststressor. Both basal and stress-induced fecal glucocorticoid
metabolite levels showed individual variations. The increase of fecal glucocorticoid metabolites after the stressor (paralleling
increases in serum) indicates that one can effectively measure adrenocortical activity in Alouatta pigra via these 2 enzyme immunoassays. However, it is important to consider individual variations in the excretion of fecal glucocorticoid
metabolites when planning field endocrinological research on Alouatta pigra. Fecal glucocorticoid metabolite excretion takes 1–3 d poststressor depending on the individual. Further, there is an important
individual variability in the concentrations of glucocorticoid metabolites, which might reflect differences in stress reactivity
or fecal glucocorticoid metabolite metabolism and excretion. 相似文献
30.
Elisabet Börjesson Annika Sundin Rhys Leeming Lennart Torstensson 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1998,713(2):62
A new method has been developed to determine a number of sterols in urine using non-chlorinated solvents, namely methyl tert.-butyl ether and methanol (the MTB method). The method involves liquid–liquid extraction, saponification, reextraction, silylation and final identification and quantification by GC–FID. The sterols determined were coprostanol, epicoprostanol, cholesterol and dihydrocholesterol. 5α-Cholestane was used as internal standard. The limit of detection for the sterols in this experiment was 2 μg l−1 urine. Recovery of coprostanol over the range 5–100 μg l−1 urine by this method was between 80 and 92%. 相似文献