全文获取类型
收费全文 | 1143篇 |
免费 | 91篇 |
国内免费 | 1篇 |
出版年
2023年 | 13篇 |
2022年 | 21篇 |
2021年 | 45篇 |
2020年 | 32篇 |
2019年 | 38篇 |
2018年 | 48篇 |
2017年 | 29篇 |
2016年 | 55篇 |
2015年 | 76篇 |
2014年 | 85篇 |
2013年 | 86篇 |
2012年 | 108篇 |
2011年 | 105篇 |
2010年 | 58篇 |
2009年 | 34篇 |
2008年 | 57篇 |
2007年 | 37篇 |
2006年 | 43篇 |
2005年 | 36篇 |
2004年 | 30篇 |
2003年 | 27篇 |
2002年 | 12篇 |
2001年 | 8篇 |
2000年 | 9篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 10篇 |
1994年 | 7篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 13篇 |
1984年 | 9篇 |
1983年 | 3篇 |
1981年 | 4篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有1235条查询结果,搜索用时 46 毫秒
101.
Szwaczkowski T Wezyk S Stanisławska-Barczak E Badowski J Bielińska H Wolc A 《Journal of applied genetics》2007,48(3):253-260
Body weight is one of the most important traits in any genetic improvement program in geese for at least 2 reasons. First, measurements of the trait are very easy. Second, body weight is correlated with a number of other meat performance traits. However, the genetic background of body weight shows considerable complexity. Three genetic models (with direct, maternal genetic and permanent maternal environmental effects) were employed in this study. Records of 3076 individuals of maternal strain W11 and 2656 individuals of paternal strain W33 over 6 consecutive generations, kept in the pedigree farm of Ko?uda Wielka, were analysed. Body weight (in kilograms) was measured in weeks 8 (BW8) and 11 (BW11). The inbreeding levels in both populations were relatively low (0.14% and 0.02% for W11 and W33, respectively), therefore these effects were not included in the linear models to estimate genetic parameters. Three fixed effects (hatch period, sex and year) were included in each linear model. Two criteria (AIC, BIC) were used to check the goodness of fit of the models. The computations were performed by WOMBAT software. In general, the genetic parameter estimates varied across the traits, models and strains studied. Direct additive heritability estimates ranged from 0.0001 (for BW11 of W33) to 0.55 (for BW11 of W33). Maternal and total heritabilities were also variable. Estimates of ratios of direct-maternal effect covariance in phenotypic variance were both positive and negative, but they were negligible, whereas ratios of the permanent environmental maternal variance to phenotypic variance were close to zero. Both of the applied criteria of model adequacy indicate that the model with maternal genetic and environmental effects should be considered as optimal. Genetic trends were close to zero. It seems that they were influenced by long-term selection. Similar tendencies have been observed for phenotypic trends, as well. 相似文献
102.
103.
Brzostek A Dziadek B Rumijowska-Galewicz A Pawelczyk J Dziadek J 《FEMS microbiology letters》2007,275(1):106-112
Recent reports have indicated that cholesterol plays a crucial role during the uptake of mycobacteria by macrophages. However, the significance of cholesterol modification enzymes encoded by Mycobacterium tuberculosis for bacterial pathogenicity remains unknown. Here, the authors explored whether the well-known cholesterol modification enzyme, cholesterol oxidase (ChoD), is important for virulence of the tubercle bacillus. Homologous recombination was used to replace the choD gene from the M. tuberculosis genome with a nonfunctional copy. The resultant mutant (delta choD) was attenuated in peritoneal macrophages. No attenuation in macrophages was observed when the same strain was complemented with an intact choD gene controlled by a heat shock promoter (delta choDP(hsp)choD). The mice infection experiments confirm the significance of ChoD in the pathogenesis of M. tuberculosis. 相似文献
104.
SNPs in the porcine <Emphasis Type="Italic">PPARGC1a</Emphasis> gene: Interbreed differences and their phenotypic effects 总被引:1,自引:0,他引:1
Stachowiak M Szydlowski M Cieslak J Switonski M 《Cellular & molecular biology letters》2007,12(2):231-239
Due to its function, the peroxisome proliferative activated receptor-γ, coactivator-1α (PPARGC1A) gene is a candidate in the search for genes that may affect production traits in the pig. The purpose of this study was
to screen for new SNPs in exon 8 of the porcine PPARGC1A gene and to test their possible association with production traits. Altogether 736 pigs representing five breeds Polish Landrace,
n=242; Polish Large White, n=192; Hampshire, n=27; Duroc, 21; Pietrain, n=12) and synthetic line 990 (n=242) were scanned
via SSCP assay. Four SNPs were found; two new ones: C/G (His338Gln) and G/A Thr359Thr), and two previously reported ones:
C/A (Arg369Arg) and T/A Cys430Ser). The missense T/A and C/G SNPs demonstrated pronounced interbreed variability in terms
of allele frequencies, including the exclusive presence of the C/G substitution in the Hampshire breed. The tested SNPs occurred
in five putative haplotypes, and their frequency also differed substantially between breeds. The association of the SNPs with
production traits was tested for G/A (Thr359Thr), C/A (Arg369Arg) and T/A (Cys430Ser) substitutions in Polish Large White,
Polish Landrace and line 990. The analysis revealed only breed-specific associations. The T/A (Cys430Ser) SNP was related
to the feed conversion ratio in the Polish Large White (P=0.02), and the silent G/A and C/A substitutions were respectively
associated with abdominal fat in line 990 and backfat thickness in Polish Landrace (P=0.04). The combined effects of the substitutions
were estimated as haplotype effects. Three significant contrasts between haplotypes were calculated, but the observed associations
were again only breed-specific. 相似文献
105.
Hydrobiologia - Springs as ecotones represent a suitable environment for testing hypotheses regarding the principles of a benthic community assembly. In this study, we aimed to uncover the... 相似文献
106.
107.
108.
109.
Jakub Kreisinger Géraldine Bastien Heidi C Hauffe Julian Marchesi Sarah E Perkins 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2015,370(1675)
The gut microbiota is vital to host health and, as such, it is important to elucidate the mechanisms altering its composition and diversity. Intestinal helminths are host immunomodulators and have evolved both temporally and spatially in close association with the gut microbiota, resulting in potential mechanistic interplay. Host–helminth and host–microbiota interactions are comparatively well-examined, unlike microbiota–helminth relationships, which typically focus on experimental infection with a single helminth species in laboratory animals. Here, in addition to a review of the literature on helminth–microbiota interactions, we examined empirically the association between microbiota diversity and composition and natural infection of multiple helminth species in wild mice (Apodemus flavicollis), using 16S rRNA gene catalogues (metataxonomics). In general, helminth presence is linked with high microbiota diversity, which may confer health benefits to the host. Within our wild rodent system variation in the composition and abundance of gut microbial taxa associated with helminths was specific to each helminth species and occurred both up- and downstream of a given helminth''s niche (gut position). The most pronounced helminth–microbiota association was between the presence of tapeworms in the small intestine and increased S24–7 (Bacteroidetes) family in the stomach. Helminths clearly have the potential to alter gut homeostasis. Free-living rodents with a diverse helminth community offer a useful model system that enables both correlative (this study) and manipulative inference to elucidate helminth–microbiota interactions. 相似文献
110.
Jana Hurnakova Jakub Zavada Petra Hanova Hana Hulejova Martin Klein Herman Mann Olga Sleglova Marta Olejarova Sarka Forejtova Olga Ruzickova Martin Komarc Jiri Vencovsky Karel Pavelka Ladislav Senolt 《Arthritis research & therapy》2015,17(1)
IntroductionCalprotectin, a heterodimeric complex of S100A8/9 (MRP8/14), has been proposed as an important serum biomarker that reflects disease activity and structural joint damage in rheumatoid arthritis (RA). The objective of this cross-sectional study was to test the hypothesis that calprotectin is associated with clinical and ultrasound-determined disease activity in patients with RA.MethodsA total of 37 patients with RA (including 24 females, a mean disease duration of 20 months) underwent a clinical examination and 7-joint ultrasound score (German US-7) of the clinically dominant hand and foot to assess synovitis by grey-scale (GS) and synovial vascularity by power Doppler (PD) ultrasound using semiquantitative 0–3 grading. The levels of serum calprotectin and C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) were determined at the time of the ultrasound assessment. We analysed the relationship between serum calprotectin level, traditional inflammatory markers, and ultrasound-determined synovitis.ResultsThe levels of serum calprotectin were significantly correlated with swollen joint count (r = 0.465, p < 0.005), DAS28-ESR (r = 0.430, p < 0.01), ESR (r = 0.370, p < 0.05) and, in particular, CRP (r = 0.629, p < 0.001). Calprotectin was significantly associated with GS (r = 0.359, p < 0.05) and PD synovitis scores (r = 0.497, p < 0.005). Using multivariate regression analysis, calprotectin, adjusted for age and sex, was a better predictor of PD synovitis score (R2 = 0.765, p < 0.001) than CRP (R2 = 0.496, p < 0.001).ConclusionsThe serum levels of calprotectin are significantly associated with clinical, laboratory and ultrasound assessments of RA disease activity. These results suggest that calprotectin might be superior to CRP for monitoring ultrasound-determined synovial inflammation in RA patients. 相似文献