全文获取类型
收费全文 | 14606篇 |
免费 | 828篇 |
国内免费 | 740篇 |
出版年
2023年 | 243篇 |
2022年 | 401篇 |
2021年 | 543篇 |
2020年 | 479篇 |
2019年 | 701篇 |
2018年 | 539篇 |
2017年 | 341篇 |
2016年 | 374篇 |
2015年 | 513篇 |
2014年 | 1049篇 |
2013年 | 1123篇 |
2012年 | 775篇 |
2011年 | 932篇 |
2010年 | 790篇 |
2009年 | 644篇 |
2008年 | 802篇 |
2007年 | 734篇 |
2006年 | 580篇 |
2005年 | 550篇 |
2004年 | 489篇 |
2003年 | 396篇 |
2002年 | 355篇 |
2001年 | 190篇 |
2000年 | 182篇 |
1999年 | 192篇 |
1998年 | 182篇 |
1997年 | 146篇 |
1996年 | 162篇 |
1995年 | 172篇 |
1994年 | 162篇 |
1993年 | 106篇 |
1992年 | 134篇 |
1991年 | 93篇 |
1990年 | 101篇 |
1989年 | 85篇 |
1988年 | 59篇 |
1987年 | 59篇 |
1986年 | 60篇 |
1985年 | 81篇 |
1984年 | 101篇 |
1983年 | 91篇 |
1982年 | 95篇 |
1981年 | 53篇 |
1980年 | 65篇 |
1979年 | 55篇 |
1978年 | 38篇 |
1977年 | 36篇 |
1976年 | 24篇 |
1974年 | 21篇 |
1973年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
911.
Use of epitope tags for routine analysis of transgene expression 总被引:1,自引:0,他引:1
Peptide and RNA epitope tags as tools for routine analysis of transgene expression and protein accumulation in transformed plant cell cultures was evaluated using three genes that encode very structurally and functionally different proteins. A T7 peptide was introduced at the amino- and carboxyl-termini of phosphinothricin-N-acetyl transferase and avidin and at the carboxyl-terminus of galactose oxidase. An RNA sequence that forms a higher order structure that is recognized by antibodies raised against the FLAG peptide was separately introduced into the 3 nontranslated region of these genes. Constructs were introduced into maize cell cultures using particle bombardment and transgene expression, protein accumulation, protein function and presence of the tags in RNA and/or protein as appropriate were evaluated in up to approximately 25 culture lines per construct. Results indicate that, while there will likely always be a need for some empirical evaluation of any tag-protein combination, introduction of the peptide tag at the amino-terminus was generally more successful than was incorporation at the carboxyl-terminus. RNA tags show promise for this purpose, but routine application will require development of a very sensitive immunoassay.Both of these authors contributed equally to this work and should be recognized as first authors. 相似文献
912.
Novel ribozymes produced by in vitro selection techniques provide insights into the possible mechanisms of protein synthesis evolution. The availability of such ribozymes also paves the way for experiments to explore the evolution of RNA–protein enzymes. 相似文献
913.
914.
915.
916.
917.
Fausti S La Penna G Paoletti J Genest D Lancelot G Perico A 《Journal of biomolecular NMR》2001,20(4):333-349
The cross-peaks of 1H-NOESY spectra at different time delays are compared to a mode-coupling diffusion (MCD) calculation, including the evaluation of the full 1H relaxation matrix, in the case of a 23 nucleotide fragment of the stem-loop SL1 domain of HIV-1Lai genomic RNA mutated in a single position. The MCD theory gives significant agreement with 1H relaxation experiments enabling a thorough understanding of the differential local dynamics along the sequence and particularly of the dynamics of nucleotides in the stem and in the loop. The differential dynamics of this hairpin structure is important in directing the dimerization of the retroviral genome, a fundamental step in the infectious process. The demonstration of a reliable use of time dependent NOE cross-peaks, largely available from NMR solution structure determination, coupled to MCD analysis, to probe the local dynamics of biological macromolecules, is a result of general interest of this paper. 相似文献
918.
Multiple-quantum 2D and 3D bi-directional HCNCH experiments are presented for the correlation of base and ribose protons/carbons in 13C/15N labeled HIV-1 TAR RNA. In both 2D and 3D experiments, the magnetization of H1 is transferred to H6/H8 and H1 through H1-C1-N1/9-C6/8-H6/8 and H1-C1-N1/9-C1-H1 pathways, and the magnetization of H6/8 is transferred to H1 and H6/8 through H6/8-C6/8-N1/9-C1-H1 and H6/8-C6/8-N1/9-C6/8-H6/8 pathways. Chemical shifts of four different nuclei (H1, C1, C6/8 and H6/8) are sampled in the 2D experiment. The correlation of base and ribose protons/carbons is established by the rectangular arrangement of crossover and out-and-back peaks in the proton/carbon correlated spectrum. The rectangular connections can be further resolved using the nitrogen dimension in a 1H/13C/15N 3D experiment. Furthermore, by taking advantage of the well separated chemical shifts of N1 (pyrimidine) and N9 (purine), the 2D spectrum can be simplified into two sub-spectra based on their base type. Both experiments were tested on a 13C/15N labeled 27-mer HIV-1 TAR RNA containing a UUCG hairpin loop. 相似文献
919.
920.