全文获取类型
收费全文 | 3571篇 |
免费 | 156篇 |
国内免费 | 302篇 |
出版年
2024年 | 2篇 |
2023年 | 17篇 |
2022年 | 21篇 |
2021年 | 52篇 |
2020年 | 35篇 |
2019年 | 51篇 |
2018年 | 56篇 |
2017年 | 88篇 |
2016年 | 51篇 |
2015年 | 72篇 |
2014年 | 156篇 |
2013年 | 154篇 |
2012年 | 140篇 |
2011年 | 171篇 |
2010年 | 120篇 |
2009年 | 204篇 |
2008年 | 222篇 |
2007年 | 228篇 |
2006年 | 221篇 |
2005年 | 186篇 |
2004年 | 161篇 |
2003年 | 142篇 |
2002年 | 133篇 |
2001年 | 83篇 |
2000年 | 96篇 |
1999年 | 71篇 |
1998年 | 65篇 |
1997年 | 41篇 |
1996年 | 52篇 |
1995年 | 54篇 |
1994年 | 53篇 |
1993年 | 41篇 |
1992年 | 72篇 |
1991年 | 39篇 |
1990年 | 46篇 |
1989年 | 34篇 |
1988年 | 43篇 |
1987年 | 32篇 |
1986年 | 39篇 |
1985年 | 126篇 |
1984年 | 107篇 |
1983年 | 58篇 |
1982年 | 85篇 |
1981年 | 37篇 |
1980年 | 25篇 |
1979年 | 26篇 |
1978年 | 10篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1973年 | 2篇 |
排序方式: 共有4029条查询结果,搜索用时 625 毫秒
61.
62.
To investigate the role of satellite DNA in eukaryotic genomes, we isolated from an African green monkey (Cercopithecus aethiops) genomic library cloned segments containing the previously described deca-satellite linked to low-copy-number genomic sequences. Three such clones were obtained. The low-copy-number sequences in the three clones do not cross-hybridize suggesting that they derive from different genomic loci. The structure of one of the clones, λAMkA, is described in detail. Subcloned segments containing the low-copy-number sequences from λAMkA anneal to monkey, human and mouse genomic DNA. The subcloned probes were used to select clones containing homologous sequences from a second, independent monkey library as well as from human and mouse genomic libraries. Several of the newly isolated monkey clones hybridized to probes containing the species-specific deca- and -satellites, confirming the genomic association of the low-copy-number sequence in λAMkA with satellite DNA. Moreover, several of the human and mouse clones hybridized to species-specific human and mouse satellite DNAs, respectively. These experiments indicate that the low-copy-number sequence in λMkA and its association with satellite DNA is conserved in primates and rodents. 相似文献
63.
E D Gundelfinger 《FEBS letters》1983,157(1):133-138
The interaction between the three Drosophila DNA-dependent RNA polymerases (EC 2.7.7.6) and the DNA template or the RNA product was investigated by photochemical cross-linking and binding studies, using RNA polymerase subunits immobilized on nitro-cellulose filters. It can be shown that the two largest subunits are responsible for the binding of the enzymes to both template and newly-synthesized RNA. 相似文献
64.
Guinea fowl were inoculated rectally with Histomonas meleagridis to produce histomoniasis. The birds were infected readily by this unnatural route. Severe cecal involvement was frequent and long-lasting but liver lesions and death were rare. Turkeys given the same inoculum had high levels of liver involvement and mortality. Guinea fowl responded much less severely to infection with H. meleagridis when infected by a natural route (ingestion of a vector) rather than by rectal inoculation. Thus, naturally acquired infections with H. meleagridis appear to be of small consequence in the guinea fowl. 相似文献
65.
Charles Illingworth Gregg Larson Goran Hellekant 《Journal of industrial microbiology & biotechnology》1989,4(1):37-42
Summary To produce and direct the export inStreptomyces lividans of the sweet plant protein thaumatin, thaumatin II cDNA was fused in the correct reading frame to the -galactosidase leader peptide, under the control of the -galactosidase promoter and ribosome binding site. The export of the recombinant thaumatin may allow the correct formation of the thaumatin disulfide bonds. The recombinant thaumatin was purified from the medium on an S-Sepharose column and detected with western blots by sheep -thaumatin antibodies. The recombinant thaumatin was the same size as authentic thaumatin and changed position on an acrylamide gel in response to reduction by 2-mercaptoethanol in the same manner. 相似文献
66.
Franco D. Menozzi Catherine Menozzi-Dejaiffe Francis E. Nano 《FEMS microbiology letters》1989,58(1):59-63
In order to develop reagents to study the immune response of guinea pigs to infection by Chlamydia psittaci guinea pig inclusion conjunctivitis strain (GPIC), we constructed a plasmid clone bank with C. psittaci DNA. One of the recombinant clones isolated produced large amounts of a 57-kilodalton (kDa) protein that was immunoreactive with sera from GPIC infected guinea pigs. While investigating this recombinant protein, we discovered that all the Gram-negative bacteria analyzed so far have immunoreactive proteins of similar size. This protein seems to be a 'common antigen' already described in various Gram-negative bacteria. 相似文献
67.
68.
Lisa R. Williamson Gregory V. Piano Herbert H. Winkler Duncan C. Krause David O. Wood 《Gene》1989,80(2):269-278
The Rickettsia prowazekii ATP/ADP translocase (Tlc) gene (tlc), previously cloned in Escherichia coli was localized to a 1.6-kb chromosomal fragment. Nucleotide sequence analysis of this fragment revealed an open reading frame of 1494 bp that could encode a hydrophobic protein of 497 amino acids (aa) with an Mr of 56 668. Analysis of the deduced aa sequence revealed that it contained twelve potential membrane-spanning regions. Comparisons between the deduced aa sequence of the R. prowazekii ATP/ADP Tlc and the sequences of mitochondrial (mt) Tic revealed no detectable homologies between the rickettsial and mt sequences. The major protein synthesized in E. coli minicells containing the rickettsial gene exhibited an Mr of approx. 34000. 相似文献
69.
The construction and use of two novel transposon(Tn)-delivery vectors is described. These vectors carry Inc.W or Inc.N broad-host-range transfer functions cloned next to the narrow-host-range replicon of pBR329. The host specificities of pSLX10 and pSLX23 both complement and extend the host specificities of existing Tn delivery vectors. Plasmids pSLX10 and pSLX23 were shown to transfer at high frequency in intergeneric matings. The lux genes which are present on each vector permit the visual monitoring of transconjugants which have retained a Tn element, but are devoid of plasmid molecules. pSLX10 and pLSX23 were efficiently used to generate a range of auxotrophic mutants in various strains of Pseudomonas as well as to clone genes from Serratia liquefaciens. These vectors may have general applicability to identify and clone genes in a wide range of Gram-negative bacteria. 相似文献
70.