全文获取类型
收费全文 | 18431篇 |
免费 | 1869篇 |
国内免费 | 602篇 |
出版年
2022年 | 151篇 |
2021年 | 322篇 |
2020年 | 228篇 |
2019年 | 310篇 |
2018年 | 395篇 |
2017年 | 334篇 |
2016年 | 554篇 |
2015年 | 867篇 |
2014年 | 960篇 |
2013年 | 1100篇 |
2012年 | 1380篇 |
2011年 | 1336篇 |
2010年 | 908篇 |
2009年 | 760篇 |
2008年 | 1026篇 |
2007年 | 981篇 |
2006年 | 912篇 |
2005年 | 814篇 |
2004年 | 837篇 |
2003年 | 703篇 |
2002年 | 660篇 |
2001年 | 394篇 |
2000年 | 351篇 |
1999年 | 301篇 |
1998年 | 213篇 |
1997年 | 163篇 |
1996年 | 133篇 |
1995年 | 129篇 |
1994年 | 144篇 |
1993年 | 126篇 |
1992年 | 204篇 |
1991年 | 201篇 |
1990年 | 186篇 |
1989年 | 194篇 |
1988年 | 176篇 |
1987年 | 166篇 |
1986年 | 164篇 |
1985年 | 143篇 |
1984年 | 126篇 |
1983年 | 98篇 |
1982年 | 99篇 |
1981年 | 105篇 |
1980年 | 90篇 |
1979年 | 106篇 |
1978年 | 106篇 |
1976年 | 86篇 |
1975年 | 98篇 |
1974年 | 94篇 |
1973年 | 86篇 |
1972年 | 70篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
992.
Identification of two distinct regions of p38 MAPK required for substrate binding and phosphorylation 总被引:3,自引:0,他引:3
The mechanism by which different mitogen activated protein kinases (MAPKs) distinguish between different substrates is poorly understood. For example, p38 and SAPK4 are two closely related p38 MAPKs that both phosphorylate ATF2 and MBP. However, p38 phosphorylates MAPKAPK-2 and -3, whereas SAPK4 does not. In this study, we have used mutagenesis to determine the regions of p38 required for substrate selection. Alanine scanning mutagenesis identified one region of p38 that was required for its ability to phosphorylate MAPKAPK-2 and -3, but that did not significantly affect its binding to these substrates. Chimeras of p38 and SAPK4 identified a second region of p38 that affected the ability of p38 to both bind and phosphorylate MAPKAPK-2 and -3. Hence, we show for the first time that MAPKs contain two distinct regions for recognizing and phosphorylating protein substrates. 相似文献
993.
Young Jun Kang Young Shin Kim Hyangsuk Hur Hee Sun Kim Hyo Jeong Hong 《Biotechnology letters》1999,21(5):375-380
The complete (encoding 55 amino acids, aa) or partial (encoding aa 1–26) preS2 region gene of hepatitis B virus (HBV) was fused to the 3-end of glutathion-S-transferase (GST) gene and expressed under the control of the inducible tac promoter in Escherichia coli at 37 °C. The fusion protein with the complete preS2 region was moderately expressed (8%) while the protein with the N-terminal 26 aa was expressed at a higher level, yielding about 20% of the total cellular proteins. The GST-preS2 (aa 1–26) protein, which contains the immunodominant epitope, was produced form the soluble protein fraction of the recombinant bacteria and purified by affinity chromatography using glutathione-agarose column. The purified preS2 fusion protein showed the antigenicity of preS2, as assessed by indirect and competitive ELISAs. 相似文献
994.
995.
Jim Provan Pat Lawrence George Young Frank Wright Robert Bird GianPaolo Paglia Federica Cattonaro Michele Morgante Wayne Powell 《Plant Systematics and Evolution》1999,218(3-4):245-256
We have used polymorphic chloroplast simple sequence repeats (cpSSRs) to analyse levels of diversity and relationships within the genusZea. Between two and nine alleles were found at 15 polymorphic loci and combining the data from these loci gave 32 haplotypes in the 37 accessions studied. Genetic differentiation between the two sections within the genus was calculated using theST statistic which showed that 70% of the total variation was found to exist between the sections. A phylogenetic analysis based on the
2 distance metric showed a large split between the two sections and suggested multiple origins of modern cultivated maizeZea mays subsp.mays. The agreement of the phylogenetic tree with other molecular, morphological and karyological studies suggests that cpSSRs may have value in phylogenetic studies in plants. 相似文献
996.
997.
998.
999.
1000.
Neurofilament-L (NF-L) is a major element of neuronal cytoskeletons and known to be important for their survival in vivo. Since oxidative stress might play a critical role in the pathogenesis of neurodegenerative diseases, we investigated the role of Cu,Zn-superoxide dismutase (SOD) in the modification of NF-L. When disassembled NF-L was incubated with Cu,Zn-SOD and H2O2, the aggregation of protein was proportional to the concentration of hydrogen peroxide. Cu,Zn-SOD/H2O2-mediated modification of NF-L was significantly inhibited by radical scavenger, spin trap agents and copper chelators. Dityrosine crosslink formation was obtained in Cu,Zn-SOD/H2O2-mediated NF-L aggregates. Antioxidant molecules, carnosine and anserine significantly inhibited the aggregation of NF-L and the formation of dityrosine. This study suggests that copper-mediated NF-L modification may be closely related to oxidative reactions which play a critical role in neurodegenerative diseases. 相似文献