全文获取类型
收费全文 | 1986篇 |
免费 | 93篇 |
国内免费 | 3篇 |
出版年
2021年 | 8篇 |
2020年 | 17篇 |
2019年 | 18篇 |
2018年 | 16篇 |
2017年 | 16篇 |
2016年 | 27篇 |
2015年 | 30篇 |
2014年 | 49篇 |
2013年 | 143篇 |
2012年 | 101篇 |
2011年 | 99篇 |
2010年 | 49篇 |
2009年 | 69篇 |
2008年 | 112篇 |
2007年 | 116篇 |
2006年 | 115篇 |
2005年 | 96篇 |
2004年 | 108篇 |
2003年 | 115篇 |
2002年 | 118篇 |
2001年 | 49篇 |
2000年 | 45篇 |
1999年 | 46篇 |
1998年 | 43篇 |
1997年 | 27篇 |
1996年 | 24篇 |
1995年 | 20篇 |
1994年 | 18篇 |
1993年 | 17篇 |
1992年 | 34篇 |
1991年 | 37篇 |
1990年 | 21篇 |
1989年 | 22篇 |
1988年 | 25篇 |
1987年 | 19篇 |
1986年 | 17篇 |
1985年 | 23篇 |
1984年 | 14篇 |
1983年 | 14篇 |
1982年 | 17篇 |
1981年 | 19篇 |
1980年 | 22篇 |
1979年 | 12篇 |
1978年 | 13篇 |
1977年 | 10篇 |
1976年 | 8篇 |
1975年 | 10篇 |
1974年 | 7篇 |
1973年 | 5篇 |
1972年 | 4篇 |
排序方式: 共有2082条查询结果,搜索用时 314 毫秒
1.
Staphylococcal gamma-hemolysin and leukocidin are bi-component cytolysins, consisting of LukF (or Hlg1)/Hlg2 and LukF/LukS, respectively. Here, we purified serum inhibitors of gamma-hemolysin and leukocidin from human plasma. Protein sequencing showed that the purified inhibitors of 62, 57, 50 and 38 kDa were the vitronectin fragments with truncation(s) of the C-terminal or both N- and C-terminal regions. The purified vitronectin fragments specifically bound to the Hlg2 component of gamma-hemolysin and the LukS component of leukocidin to form high-molecular-weight complexes with them, leading to inhibition of the toxin-induced lysis of human erythrocytes and human polymorphonuclear leukocytes, respectively. Intact vitronectin also showed inhibitory activity to the toxins. The ability of gamma-hemolysin and leukocidin to bind vitronectin and its fragments is a novel function of the pore-forming cytolysins. 相似文献
2.
Hisao Tsukamoto Yoshihiro Kubo David L. Farrens Mitsumasa Koyanagi Akihisa Terakita Yuji Furutani 《The Journal of biological chemistry》2015,290(45):27176-27187
Melanopsins play a key role in non-visual photoreception in mammals. Their close phylogenetic relationship to the photopigments in invertebrate visual cells suggests they have evolved to acquire molecular characteristics that are more suited for their non-visual functions. Here we set out to identify such characteristics by comparing the molecular properties of mammalian melanopsin to those of invertebrate melanopsin and visual pigment. Our data show that the Schiff base linking the chromophore retinal to the protein is more susceptive to spontaneous cleavage in mammalian melanopsins. We also find this stability is highly diversified between mammalian species, being particularly unstable for human melanopsin. Through mutagenesis analyses, we find that this diversified stability is mainly due to parallel amino acid substitutions in extracellular regions. We propose that the different stability of the retinal attachment in melanopsins may contribute to functional tuning of non-visual photoreception in mammals. 相似文献
3.
4.
Summary An activated carbon column was utilized for the synthesis of disaccharides by use of a reversed hydrolysis activity of an immobilized -galactosidase column in order to shift the equilibrium to the direction of condensation. The yields of lactulose and allo-lactulose from galactose and fructose, and N-acetyl lactosamine and N-acetyl allolactosamine from galactose and N-acetyl glucosamine, were 11.3% and 10.0%, respectively. 相似文献
5.
Katsumi Shinkawa Shigeo Nakajo Kazuyasu Nakaya Yasuharu Nakamura 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》1987,930(3)
We have attempted to purify endogenous substrate proteins for casein kinases I and II from the cytosol of AH-66 hepatoma cells. Utilizing the fact that only a few substrates are concentrated in the fraction eluted from DEAE-cellulose between 0.3 and 0.6 M NaCl, two substrates were purified from this fraction by DEAE-cellulose chromatography, hydroxyapatite chromatography, and HPLC on a DEAE-5PW column. The purified substrate proteins had molecular masses of 30.5 kDa and 31 kDa. The 31-kDa protein substrate was markedly phosphorylated by casein kinase II, but only slightly by casein kinase I. The radioactive phosphate incorporated into 31-kDa substrate by casein kinase II was 0.2 mol/mol of the protein and phosphorylation occurred on both threonine and serine residues. The 30.5 kDa protein was only slightly phosphorylated by casein kinase II, but not at all by casein kinase I. 相似文献
6.
Thymidylate synthetase (EC 2.1.1.45) from rat regenerating liver has been purified over 5000-fold to apparent homogeneity by a procedure involving two affinity methods. Molecular weight of the native enzyme was found to be about 68,000, as determined by gel filtration. Electrophoresis in polyacrylamide gels containing sodium dodecyl sulfate yielded a single band of molecular weight of 35,000, suggesting that thymidylate synthetase is a dimer of very similar or identical subunits. The Michaelis constants for deoxyuridylate (dUMP) and (+/-)L-5,10-methylenetetrahydrofolate are 6.8 microM and 65 microM, respectively. Reaction kinetics and product inhibition studies reveal the enzymatic mechanism to be ordered sequential. 5-Fluoro-dUMP, halogenated analog of the nucleotide substrate is a competitive inhibitor of the enzyme, with an apparent Ki value of 5 nM. Amethopterin, analog of the cofactor is also a competitive inhibitor with an apparent Ki value of 23 microM. 相似文献
7.
8.
9.
10.
The increases in the activities of hepatic thymidylate synthetase and thymidine kinase were significantly suppressed at 24 h after 70% partial hepatectomy in rats which had been administered a microtubule disrupter, colchicine or vincristine. The decrease of these enzymic activities was accompanied by a reduction of DNA content in 24 h regenerating liver. The immunoblotting assay showed that the depression of the thymidylate synthetase activity by the injection of colchicine or vincristine was due to the decrease of the enzyme protein. These results indicate that colchicine and vincristine inhibit the DNA synthesis during liver regeneration by inhibiting the induction of the key enzyme in DNA synthesis. 相似文献