全文获取类型
收费全文 | 37449篇 |
免费 | 2861篇 |
国内免费 | 5496篇 |
出版年
2024年 | 113篇 |
2023年 | 781篇 |
2022年 | 924篇 |
2021年 | 1315篇 |
2020年 | 1284篇 |
2019年 | 1580篇 |
2018年 | 1293篇 |
2017年 | 1189篇 |
2016年 | 1210篇 |
2015年 | 1392篇 |
2014年 | 1807篇 |
2013年 | 2464篇 |
2012年 | 1720篇 |
2011年 | 1734篇 |
2010年 | 1539篇 |
2009年 | 1874篇 |
2008年 | 2021篇 |
2007年 | 2172篇 |
2006年 | 2208篇 |
2005年 | 2061篇 |
2004年 | 1906篇 |
2003年 | 1754篇 |
2002年 | 1599篇 |
2001年 | 1305篇 |
2000年 | 1107篇 |
1999年 | 987篇 |
1998年 | 878篇 |
1997年 | 754篇 |
1996年 | 727篇 |
1995年 | 680篇 |
1994年 | 644篇 |
1993年 | 447篇 |
1992年 | 395篇 |
1991年 | 335篇 |
1990年 | 282篇 |
1989年 | 202篇 |
1988年 | 221篇 |
1987年 | 199篇 |
1986年 | 144篇 |
1985年 | 132篇 |
1984年 | 120篇 |
1983年 | 56篇 |
1982年 | 73篇 |
1981年 | 35篇 |
1980年 | 44篇 |
1979年 | 30篇 |
1978年 | 20篇 |
1977年 | 10篇 |
1976年 | 16篇 |
1950年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 851 毫秒
11.
《Molecular cell》2021,81(20):4271-4286.e4
- Download : Download high-res image (250KB)
- Download : Download full-size image
12.
We re-engineered a classic tool for mutagenesis and gene expression studies in Gram-negative bacteria. Our modified Tn5-based transposon contains multiple features that allow rapid selection for mutants, direct quantification of gene expression and straightforward cloning of the inactivated gene. The promoter-less gfp-km cassette provides selection and reporter assay depending on the activity of the promoter upstream of the transposon insertion site. The cat gene facilitates positive antibiotic selection for mutants, while the narrow R6Kγ replication origin forces transposition in recipient strains lacking the pir gene and enables cloning of the transposon flanked with the disrupted gene from the chromosome. The suicide vector pCKD100, a plasmid that could be delivered into recipient cells through biparental mating or electroporation, harbours the modified transposon. We used the transposon to mutagenize Pectobacterium versatile KD100, Pseudumonas coronafaciens PC27R and Escherichia coli 35150N. The fluorescence intensities of mutants expressing high GFP could be quantified and detected qualitatively. Transformation efficiency from conjugation ranged from 1600 to 1900 CFU per ml. We sequenced the upstream flanking regions, identified the putative truncated genes and demonstrated the restoration of the GFP phenotype through marker exchange. The mini-Tn5 transposon was also utilized to construct mutant a library of P. versatile for forward genetic screens. 相似文献
13.
14.
15.
The psbQ gene encoding a 16-kDa polypeptide of the oxygen-evolving complex of photosystem II has been isolated from Arabidopsis thaliana and characterized. The gene consists of a 28 nucleotide long leader sequence, two introns and three exons encoding a 223-amino-acid precursor polypeptide. The first 75 amino acids act as a transit peptide for the translocation of the polypeptide into the thylakoid lumen. Expression studies show that the gene is light-inducible and expresses only in green tissues with high steady-state mRNA levels in leaves. Using this gene as a probe, restriction fragment length polymorphism between two ecotypes, Columbia and Estland, has also been detected. 相似文献
16.
《Developmental cell》2022,57(11):1383-1399.e7
- Download : Download high-res image (247KB)
- Download : Download full-size image
17.
Cyrtandra (Gesneriaceae) is a genus of flowering plants with over 800 species distributed throughout Southeast Asia and the Pacific Islands. On the Hawaiian Islands, 60 named species and over 89 putative hybrids exist, most of which are identified on the basis of morphology. Despite many previous studies on the Hawaiian Cyrtandra lineage, questions regarding the reconciliation of morphology and genetics remain, many of which can be attributed to the relatively young age and evidence of hybridization between species. We utilized targeted enrichment, high‐throughput sequencing, and modern phylogenomics tools to test 31 Hawaiian Cyrtandra samples (22 species, two putative hybrids, four species with two samples each, one species with four samples) and two outgroups for species relationships and hybridization in the presence of incomplete lineage sorting (ILS). Both concatenated and species‐tree methods were used to reconstruct species relationships, and network analyses were conducted to test for hybridization. We expected to see high levels of ILS and putative hybrids intermediate to their parent species. Phylogenies reconstructed from the concatenated and species‐tree methods were highly incongruent, most likely due to high levels of incomplete lineage sorting. Network analyses inferred gene flow within this lineage, but not always between taxa that we expected. Multiple hybridizations were inferred, but many were on deeper branches of the island lineages suggesting a long history of hybridization. We demonstrated the utility of high‐throughput sequencing and a phylogenomic approach using 569 loci to understanding species relationships and gene flow in the presence of ILS. 相似文献
18.
19.
Robert C. Tait Byron E. Froman Debbie L. Laudencia-Chingcuanco Leslie D. Gottlieb 《Plant molecular biology》1988,11(4):381-388
Nuclear genes that appear to encode both cytosolic and plastid isozymes of phosphoglucose isomerase (PGI), an essential glycolytic enzyme, have been isolated from three diploid species of the annual wild flower genus Clarkia (Onagraceae). The genes do not contain introns and are expressed to varying degrees in Escherichia coli when cloned in either Charon 35 phage or pUC plasmid vectors. The PGI proteins synthesized in E. coli form dimers, are catalytically active, and their electrophoretic mobilities are similar to those of appropriate Clarkia PGIs. The nucleotide sequence of a gene encoding a plastid isozyme of C. unguiculata is described. 相似文献
20.