全文获取类型
收费全文 | 814篇 |
免费 | 95篇 |
国内免费 | 61篇 |
出版年
2024年 | 1篇 |
2023年 | 29篇 |
2022年 | 30篇 |
2021年 | 48篇 |
2020年 | 48篇 |
2019年 | 35篇 |
2018年 | 41篇 |
2017年 | 46篇 |
2016年 | 27篇 |
2015年 | 44篇 |
2014年 | 54篇 |
2013年 | 67篇 |
2012年 | 35篇 |
2011年 | 29篇 |
2010年 | 24篇 |
2009年 | 37篇 |
2008年 | 44篇 |
2007年 | 24篇 |
2006年 | 26篇 |
2005年 | 35篇 |
2004年 | 22篇 |
2003年 | 17篇 |
2002年 | 18篇 |
2001年 | 11篇 |
2000年 | 11篇 |
1999年 | 4篇 |
1998年 | 11篇 |
1997年 | 14篇 |
1996年 | 9篇 |
1995年 | 11篇 |
1994年 | 12篇 |
1993年 | 11篇 |
1992年 | 11篇 |
1991年 | 16篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
排序方式: 共有970条查询结果,搜索用时 15 毫秒
1.
Abstract cDNA-RNA liquid hybridization analysis was used to compare the RNA sequence homology between two members of the Nudaurelia β virus family, Trichoplusia ni virus ( T.ni V) and Dasychira pudibunda virus ( D.p V). Heterologous hybridization experiments demonstrated that these viruses shared little sequence homology. Using oligo(dT) chromatography and oligo(dT)12–18 as a primer for cDNA synthesis it was shown that neither T.ni V nor D.p V RNA genomes possess a poly(A) tract at the 3' end. 相似文献
2.
3.
《Cell》2021,184(25):6037-6051.e14
4.
Estimates of protozoan- and viral-mediated mortality of bacterioplankton in Lake Bourget (France) 总被引:2,自引:0,他引:2
STÉPHAN JACQUET ISABELLE DOMAIZON SÉBASTIEN PERSONNIC ANGIA SRIRAM PRADEEP RAM MIKAL HEDAL SOLANGE DUHAMEL TÉLESPHORE SIME-NGANDO 《Freshwater Biology》2005,50(4):627-645
1. We performed three, 1‐week in situ experiments in March‐April (expt 1), May (expt 2) and August (expt 3) 2003 in order to assess protozoan and virus‐induced mortality of heterotrophic bacteria in a French lake. Viral and bacterial abundances were obtained using flow cytometry (FCM) while protozoa were counted using epifluorescence microscopy (EFM). 2. A dilution approach, applied to pretreated grazer‐free samples, allowed us to estimate that viral lysis could be responsible for 60% (expt 1), 35% (expt 2) and 52% (expt 3) of daily heterotrophic bacterial mortality. Flagellate (both mixotrophic and heterotrophic) grazing in untreated samples, was responsible for 56% (expt 1), 63% (expt 2) and 18% (expt 3) of daily heterotrophic bacteria removal. 3. These results therefore suggest that both viral lysis and flagellate grazing had a strong impact on bacterial mortality, and this impact varied seasonally. 4. From parallel transmission electron microscopy (TEM) analysis, we found that the burst size (i.e. the number of viruses potentially released per lysed cell) ranged from nine to 25 (expt 1), 10 to 35 (expt 2) and eight to 25 (expt 3). The percentage of infected heterotrophic bacteria was 5.7% (expt 1), 3.4% (expt 2) and 5.7% (expt 3) so that the calculated percentage of bacterial mortality induced by viruses was 6.3% (expt 1), 3.7% (expt 2) and 6.3% (expt 3). 5. It is clear that the dilution‐FCM and TEM methods yielded different estimates of viral impact, although both methods revealed an increased impact of viruses during summer. 相似文献
5.
A Pierré M Richou F Lawrence M Robert-Géro P Vigier 《Biochemical and biophysical research communications》1977,76(3):813-819
An increase of methylase activity is often related to neoplastic transformation. SAH, the natural inhibitor of transmethylases, does not inhibit cell transformation induced by RSV, in contrast to one of its synthetic analogues, SIBA. This inefficiency was thought to be due to the rapid metabolism of SAH by transformed cells. We now show, that, on the contrary, 70 % of the added amount of SAH disappears in one hour in cell-free extracts of normal cell against only 14 % in extracts of transformed cells. This decreased rate of degradation occurred one day post infection. Cells infected with the non transforming RAV1 degrade SAH at the same rate as normal cells. A decrease of SAH-hydrolase and adenosine deaminase activity was also observed in infected cells. The decrease of the first enzyme seems to be related to the transformed state, whereas that of the second enzyme seems to depend only on infection, since it is also observed in cells infected with RAV1. 相似文献
6.
Different genetic stains of avian RNA tumor virus (ATV) were labeled with the fluorescent membrane probe R-18 (rhodamine conjugated
to a hydrocarbon chain) and cellular receptors for virus infection were analyzed on a rapid, single-cell basis by a multiparameter
cell sorter. Chicken cells genetically susceptible to various R-18 ATV were found to adsorb much more virus, as measured by
increased fluorescent binding, than did genetically resistant chicken cells. Virus binding to receptor sites could be saturated
with increased concentrations of labeled virus. This binding could be altered by removal of the polycation, polybrene, indicating
the important influence of electrostatic forces. Correlated time measurements of virus binding to single cells were taken
with these fluorescence measurements allowing for a minute-to-minute study of the kinetics of viral adsorption to resistant
and susceptible cells. The ratio of fluorescence (proportional to the number of virions bound per cell) to light scatter (proportional
to cell surface area) on a cell-to-cell basis was analyzed to examine the heterogeneity in fluorescent virion bound per unit
cell surface area within a given cell type. With these calculations, it was found that a large amount, but not all, of observed
fluorescence heterogeneity merely reflects differences in cell surface areas. However, there are significant differences in
viral receptor site densities within this supposedly homogeneous population of cells. This study represents a successful application
of fluorescent membrane probes and flow cytometry to the study of cellular responses to viral infection at the single-cell
level. Sine large numbers of cells can be examined rapidly, small subpopulations of live virally susceptible or resistant
cells can be cloned by multiparameter cell sorting. 相似文献
7.
8.
Mavericks are virus-like mobile genetic elements found in the genomes of eukaryotes. Although Mavericks encode capsid morphogenesis homologs, their viral particles have not been observed. Here, we provide new evidence supporting the viral nature of Mavericks and the potential existence of virions. To this end, we conducted a phylogenomic analysis of Mavericks in hundreds of vertebrate genomes, discovering 134 elements with an intact coding capacity in 17 host species. We reveal an extensive genomic fossil record in 143 species and date three groups of elements to the Late Cretaceous. Bayesian phylogenetic analysis using genomic fossil orthologs suggests that Mavericks have infected osteichthyans for ∼419 My. They have undergone frequent cross-species transmissions in cyprinid fish and all core genes are subject to strong purifying selection. We conclude that vertebrate Mavericks form an ancient lineage of aquatic dsDNA viruses which are probably still functional in some vertebrate lineages. 相似文献
9.
C.S. Fagnant-Sperati Y. Ren N.A. Zhou E. Komen B. Mwangi J. Hassan A. Chepkurui R. Nzunza J. Nyangao W.B. van Zyl M. Wolfaardt P.N. Matsapola F.B. Ngwana S. Jeffries-Miles A. Coulliette-Salmond S. Peñaranda E. Vega J.H. Shirai A.L. Kossik N.K. Beck D.S. Boyle C.C. Burns M.B. Taylor P. Borus J.S. Meschke 《Journal of applied microbiology》2021,130(3):971-981
10.
An endogenous virus, denoted ev A, is present at high frequency in all brown egg layer lines. Using inverse polymerase chain reaction (PCR) based on the viral LTR regions, products were obtained containing cellular sequences 5' and 3' to the viral insertion point. PCR of chicken genomic DNA was carried out, using primers chosen from the 5' and 3' cellular sequences and a primer chosen from either the U3 or U5 portions of the viral LTR. Amplification of DNA from birds that did not carry ev A with the primer triplets always gave a single 364bp reaction product, interpreted as representing the flank-to-flank amplification product. Amplification of DNA from known homozygous or heterozygous ev A carriers, with the same primer triplets, always gave both the expected junction product and 364bp product. Therefore, these primer sequences can be used to distinguish ev A carriers from non-carriers but cannot distinguish between homozygous and heterozygous ev A carriers. 相似文献