全文获取类型
收费全文 | 3375篇 |
免费 | 196篇 |
国内免费 | 4篇 |
出版年
2024年 | 9篇 |
2023年 | 11篇 |
2022年 | 49篇 |
2021年 | 66篇 |
2020年 | 46篇 |
2019年 | 69篇 |
2018年 | 114篇 |
2017年 | 72篇 |
2016年 | 137篇 |
2015年 | 194篇 |
2014年 | 221篇 |
2013年 | 245篇 |
2012年 | 309篇 |
2011年 | 274篇 |
2010年 | 190篇 |
2009年 | 183篇 |
2008年 | 219篇 |
2007年 | 191篇 |
2006年 | 138篇 |
2005年 | 142篇 |
2004年 | 113篇 |
2003年 | 112篇 |
2002年 | 83篇 |
2001年 | 72篇 |
2000年 | 82篇 |
1999年 | 53篇 |
1998年 | 17篇 |
1997年 | 17篇 |
1996年 | 11篇 |
1995年 | 12篇 |
1994年 | 5篇 |
1993年 | 9篇 |
1992年 | 13篇 |
1991年 | 15篇 |
1990年 | 16篇 |
1989年 | 14篇 |
1988年 | 7篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 8篇 |
1984年 | 2篇 |
1983年 | 7篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1978年 | 3篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1972年 | 2篇 |
1970年 | 1篇 |
1969年 | 3篇 |
排序方式: 共有3575条查询结果,搜索用时 15 毫秒
181.
182.
Metabolic acids produced by oral pathogens demineralize tooth surfaces, leading to dental caries. Glucosyltransferases are the key factor in this process. We synthesized various modified oligosaccharides and tested them for their inhibitory effects on glucosyltransferase activity. Oligosaccharides were produced using a mixed-culture fermentation of Lipomyces starkeyi and Leuconostoc mesenteroides and then further modified as iron- and sulfate-oligosaccharides. Iron- and sulfate-oligosaccharides reduced glucosyltransferase activity of Streptococci from 17% to 43% and prevented the formation of insoluble biomass on the surface of glass vials or stainless steel wires in the presence of sucrose. They also reduced the growth and acid productions of oral pathogens including S. mutans, S. sobrinus, Eikenella corrodens, Prevotella intermedia, and Actinobacillus actinomycetemcmitans. 相似文献
183.
Cloning and functional expression of the dps gene encoding decaprenyl diphosphate synthase from Agrobacterium tumefaciens 总被引:1,自引:0,他引:1
A newly isolated gene from Agrobacterium tumefaciens (A. tumefaciens), which encoded a decaprenyl diphosphate synthase, was cloned in Escherichia coli (E. coli), and its nucleotide sequence was determined. DNA sequence analysis revealed an open reading frame of 1077 bp capable of encoding a 358-amino-acid protein with a calculated isoelectric point of pH 5.16 and a molecular mass of 38 960 Da. The primary structure of the enzyme shared significant homology with prenyl diphosphate synthases from various sources. The deduced amino acid sequence included oligopeptide DDxxD aspartate-rich domains conserved in the majority of prenyl diphosphate synthases. High levels of the active enzyme were expressed in the soluble fraction and were readily purified to homogeneity by Ni-NTA chromatography. E. coli JM109 harboring the dps gene produced ubiquinone-10 in addition to endogenous ubiquinone-8, while E. coli JM109 harboring the dps gene mutated on the DDxxD domain lost the ability to produce ubiquinone-10, which suggests that the A. tumefaciens dps gene is functionally expressed in E. coli and that it encodes a decaprenyl diphosphate synthase. 相似文献
184.
Jin SY Hong SJ Yang HI Park SD Yoo MC Lee HJ Hong MS Park HJ Yoon SH Kim BS Yim SV Park HK Chung JH 《Arthritis research & therapy》2004,6(5):R415-R421
Estrogen and estrogen receptors (ERs) are known to play important roles in the pathophysiology of osteoarthritis (OA). To investigate ER-alpha gene polymorphisms for its associations with primary knee OA, we conducted a case-control association study in patients with primary knee OA (n = 151) and healthy individuals (n = 397) in the Korean population. Haplotyping analysis was used to determine the relationship between three polymorphisms in the ER-alpha gene (intron 1 T/C, intron 1 A/G and exon 8 G/A) and primary knee OA. Genotypes of the ER-alpha gene polymorphism were determined by PCR followed by restriction enzyme digestion (PvuII for intron 1 T/C, XbaI for intron 1 A/G, and BtgI for exon 8 G/A polymorphism). There was no significant difference between primary knee OA patients and healthy control individuals in the distribution of any of the genotypes evaluated. However, we found that the allele frequency for the exon 8 G/A BtgI polymorphism (codon 594) was significantly different between primary knee OA patients and control individuals (odds ratio = 1.38, 95% confidence interval = 1.01-1.88; P = 0.044). In haplotype frequency estimation analysis, there was a significant difference between primary knee OA patients and control individuals (degrees of freedom = 7, chi2 = 21.48; P = 0.003). Although the number OA patients studied is small, the present study shows that ER-alpha gene haplotype may be associated with primary knee OA, and genetic variations in the ER-alpha gene may be involved in OA. 相似文献
185.
Purification and cDNA cloning of a cecropin-like peptide from the great wax moth, Galleria mellonella 总被引:4,自引:0,他引:4
A cecropin-like antimicrobial peptide, Gm cecropin, was purified from hemolymph of larvae of the wax moth, Galleria mellonella, immunized against E. coli, and its antibacterial activity was examined in a radial diffusion assay. The molecular mass of Gm cecropin was 4,160.69 Da by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry analysis. The full-length cDNA of the Gm cecropin precursor was cloned by a combination of RT-PCR, based on the N-terminal sequence obtained by Edman degradation, and 5'-RACE-PCR. Analysis of the cDNA showed that cecropin is synthesized as a prepropeptide, with a putative 22-residue signal peptide, a 4-residue propeptide and a 39-residue mature peptide with a calculated mass of 4,344.18 Da the difference between the calculated and measured masses suggests that Gm cecropin is a 37-residue peptide generated by removal of the C-terminal residue and amidation. 相似文献
186.
187.
188.
189.
Sato Y Igarashi Y Hakamata Y Murakami T Kaneko T Takahashi M Seo N Kobayashi E 《Biochemical and biophysical research communications》2003,311(2):478-481
Because serum albumin is specifically produced by mature hepatocytes, detection system of albumin producing cells could be a valuable tool to visualize liver regeneration or development. We have developed here an albumin enhancer/promoter-driven Alb-DsRed2 Tg rat that expresses DsRed2, having liver-specific reporter gene expression of red fluorescent protein. To study the transdifferentiation of bone marrow cells (BMCs) into albumin producing cells, BMCs from the Alb-DsRed2 Tg rat were injected into rats having acute liver damage caused by 2-acetylaminofluorene plus carbon tetrachloride and chronic liver damage by repeated administration of CCl(4). DsRed2-positive cells were generated in the recipient liver after BMC injection. The number of transdifferentiated DsRed2-positive cells in chronic liver injury model was increased comparing with that in acute injury model. We propose that the Alb-DsRed2 Tg rat is well suited to studying in vivo liver regeneration. 相似文献
190.
The CD99 signal enhances Fas-mediated apoptosis in the human leukemic cell line, Jurkat 总被引:1,自引:0,他引:1
The CD99 antigen has been implicated in various cellular processes, including apoptosis in T cells. Previously, we reported two monoclonal antibodies that recognize different epitopes of the CD99 molecule, named DN16 and YG32. In this study, we investigated the role of each CD99 epitope in T cell apoptosis. Unlike the DN16 epitope, CD99 ligation via the YG32 epitope failed to induce T cell death. Surprisingly, however, the YG32 signal enhanced Fas-mediated apoptosis in Jurkat T cells. Augmentation of Fas-mediated apoptosis by YG32 ligation was inhibited by treatment with either of the caspase inhibitors z-VAD-fmk or z-IETD-fmk, and YG32 ligation appeared to induce Fas oligomerization. These results suggest that each CD99 epitope plays a distinct role in T cell biology, especially in T cell apoptosis. 相似文献