全文获取类型
收费全文 | 110881篇 |
免费 | 9320篇 |
国内免费 | 1880篇 |
出版年
2023年 | 527篇 |
2022年 | 1270篇 |
2021年 | 2545篇 |
2020年 | 1595篇 |
2019年 | 1959篇 |
2018年 | 2138篇 |
2017年 | 1722篇 |
2016年 | 2746篇 |
2015年 | 4386篇 |
2014年 | 5063篇 |
2013年 | 6252篇 |
2012年 | 7599篇 |
2011年 | 7444篇 |
2010年 | 4810篇 |
2009年 | 4212篇 |
2008年 | 5801篇 |
2007年 | 5788篇 |
2006年 | 5440篇 |
2005年 | 5182篇 |
2004年 | 5161篇 |
2003年 | 4606篇 |
2002年 | 4502篇 |
2001年 | 1542篇 |
2000年 | 1288篇 |
1999年 | 1538篇 |
1998年 | 1566篇 |
1997年 | 1185篇 |
1996年 | 1140篇 |
1995年 | 1090篇 |
1994年 | 1063篇 |
1993年 | 898篇 |
1992年 | 971篇 |
1991年 | 869篇 |
1990年 | 883篇 |
1989年 | 869篇 |
1988年 | 712篇 |
1987年 | 679篇 |
1986年 | 610篇 |
1985年 | 726篇 |
1984年 | 862篇 |
1983年 | 732篇 |
1982年 | 836篇 |
1981年 | 856篇 |
1980年 | 765篇 |
1979年 | 574篇 |
1978年 | 612篇 |
1977年 | 579篇 |
1976年 | 564篇 |
1974年 | 545篇 |
1973年 | 501篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
Linda L. Laack Michael E. Tewes Aaron M. Haines John H. Rappole 《Acta theriologica》2005,50(4):505-514
The ocelotLeopardus pardalis Linnaeus, 1758 is an endangered felid in the United States currently restricted to southern Texas. The objectives of our
study were to obtain data on ocelot parturition dates, fecundity, sex ratios, den characteristics, and first year survival,
all of which are critical in development of population viability models. Sixteen parturition events were recorded ranging
from mid-April to late December for 12 wild ocelots. Cumulatively, litters consisted of 1 or 2 kittens (ˉ = 1.2 ± 0.44 SD).
Cumulative sex ratio was 1∶2.5 (male:female); however, there was no significant difference between the observed sex ratio
and a 1∶1 sex ratio. Ten den sites were in close proximity (≤ 10 m) to dense thornshrub. Adult female ocelots used 2 to 4
den sites for each litter with distance between consecutively occupied dens ranging from 110 to 280 m (ˉ = 158 m ± 93 SD).
An estimated annual survival for ocelots 0 to 1 year of age was 0.68. Evidence suggests that ocelots in the wild may breed
more frequently than had been previously hypothesized. 相似文献
73.
74.
75.
76.
77.
To clarify the mechanisms of Nosema ceranae parasitism, we deep-sequenced both honey bee host and parasite mRNAs throughout a complete 6-day infection cycle. By time-series analysis, 1122 parasite genes were significantly differently expressed during the reproduction cycle, clustering into 4 expression patterns. We found reactive mitochondrial oxygen species modulator 1 of the host to be significantly down regulated during the entire infection period. Our data support the hypothesis that apoptosis of honey bee cells was suppressed during infection. We further analyzed genome-wide genetic diversity of this parasite by comparing samples collected from the same site in 2007 and 2013. The number of SNP positions per gene and the proportion of non-synonymous substitutions per gene were significantly reduced over this time period, suggesting purifying selection on the parasite genome and supporting the hypothesis that a subset of N. ceranae strains might be dominating infection. 相似文献
78.
79.
RNA‐seq analysis reveals new candidate genes for drip loss in a Pietrain × Duroc × Landrace × Yorkshire population
下载免费PDF全文
![点击此处可从《Animal genetics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Bojiang Li Kaiqing Liu Qiannan Weng Pinghua Li Wei Wei Qifa Li Jie Chen Ruihua Huang Wangjun Wu Honglin Liu 《Animal genetics》2016,47(2):192-199
Drip loss, one of the most important meat quality traits, is characterized by low heritability. To date, the genetic factors affecting the drip loss trait have not been clearly elucidated. The objective of this study was to identify critical candidate genes affecting drip loss. First, we generated a Pietrain × Duroc × Landrace × Yorkshire commercial pig population and obtained phenotypic values for the drip loss trait. Furthermore, we constructed two RNA libraries from pooled samples of longissimus dorsi muscles with the highest (H group) and lowest (L group) drip loss and identified the differentially expressed genes (DEGs) between these extreme phenotypes using RNA‐seq technology. In total, 25 883 genes were detected in the H and L group libraries, and none was specifically expressed in only one library. Comparative analysis of gene expression levels found that 150 genes were differentially expressed, of which 127 were upregulated and 23 were downregulated in the H group relative to the L group. In addition, 68 drip loss quantitative trait loci (QTL) overlapping with 63 DEGs were identified, and these QTL were distributed mainly on chromosomes 1, 2, 5 and 6. Interestingly, the triadin (TRDN) gene, which is involved in muscle contraction and fat deposition, and the myostatin (MSTN) gene, which has a role in muscle growth, were localized to more than two drip loss QTL, suggesting that both are critical candidate genes responsible for drip loss. 相似文献
80.