全文获取类型
收费全文 | 1820篇 |
免费 | 88篇 |
专业分类
1908篇 |
出版年
2022年 | 11篇 |
2021年 | 33篇 |
2020年 | 10篇 |
2019年 | 26篇 |
2018年 | 38篇 |
2017年 | 24篇 |
2016年 | 45篇 |
2015年 | 52篇 |
2014年 | 72篇 |
2013年 | 94篇 |
2012年 | 137篇 |
2011年 | 137篇 |
2010年 | 80篇 |
2009年 | 69篇 |
2008年 | 123篇 |
2007年 | 115篇 |
2006年 | 110篇 |
2005年 | 88篇 |
2004年 | 95篇 |
2003年 | 85篇 |
2002年 | 73篇 |
2001年 | 29篇 |
2000年 | 20篇 |
1999年 | 24篇 |
1998年 | 18篇 |
1997年 | 27篇 |
1996年 | 20篇 |
1995年 | 14篇 |
1994年 | 16篇 |
1993年 | 9篇 |
1992年 | 26篇 |
1991年 | 23篇 |
1990年 | 21篇 |
1989年 | 15篇 |
1988年 | 15篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 13篇 |
1984年 | 11篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1980年 | 3篇 |
1979年 | 7篇 |
1977年 | 4篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1970年 | 4篇 |
1969年 | 4篇 |
1968年 | 4篇 |
排序方式: 共有1908条查询结果,搜索用时 0 毫秒
91.
Two 6-hydroxypelargonidin glycosides were isolated from the orange-red flowers of Alstroemeria cultivars, and determined to be 6-hydroxypelargonidin 3-O-(beta-D-glucopyranoside) and 3-O-[6-O-(alpha-L-rhamnopyranosyl)-beta-D-glucopyranoside], respectively, by chemical and spectroscopic methods. In addition, five known anthocyanidin glycosides, 6-hydroxycyanidin 3-malonylglucoside, 6-hydroxycyanidin 3-rutinoside, cyanidin 3-malonylglucoside, cyanidin 3-rutinoside and pelargonidin 3-rutinoside were identified in the flowers. 相似文献
92.
93.
Nakano K Ohsawa I Yamagata K Nakayama T Sasaki K Tarashima M Saito K Osawa M Ohta S 《Mitochondrion》2003,3(1):21-27
We isolated stable cell lines, designated as mitochondrial cells, from cybrids obtained by fusing mitochondria-less HeLa cells with platelets from patients with Leigh syndrome, a subtype of mitochondrial encephalomyopathy. The cells contain a pathogenic point mutation, T9176C, in the mitochondrial DNA. Hematoxylin-eosin staining, confocal fluorescent microscopy and flow cytometry in fixed or living cells showed that the majority of these mitochondrial cells lack nuclear DNA and nuclei, but contain active mitochondria. Despite the absence of nuclear DNA, these cells can be continuously generated in culture. Therefore, it is likely that they arise from the minority of cells which possess a nucleus. 相似文献
94.
Possibility of cytoplasmic pre-tRNA splicing: the yeast tRNA splicing endonuclease mainly localizes on the mitochondria 下载免费PDF全文
Yoshihisa T Yunoki-Esaki K Ohshima C Tanaka N Endo T 《Molecular biology of the cell》2003,14(8):3266-3279
Pre-tRNA splicing has been believed to occur in the nucleus. In yeast, the tRNA splicing endonuclease that cleaves the exon-intron junctions of pre-tRNAs consists of Sen54p, Sen2p, Sen34p, and Sen15p and was thought to be an integral membrane protein of the inner nuclear envelope. Here we show that the majority of Sen2p, Sen54p, and the endonuclease activity are not localized in the nucleus, but on the mitochondrial surface. The endonuclease is peripherally associated with the cytosolic surface of the outer mitochondrial membrane. A Sen54p derivative artificially fixed on the mitochondria as an integral membrane protein can functionally replace the authentic Sen54p, whereas mutant proteins defective in mitochondrial localization are not fully active. sen2 mutant cells accumulate unspliced pre-tRNAs in the cytosol under the restrictive conditions, and this export of the pre-tRNAs partly depends on Los1p, yeast exportin-t. It is difficult to explain these results from the view of tRNA splicing in the nucleus. We rather propose a new possibility that tRNA splicing occurs on the mitochondrial surface in yeast. 相似文献
95.
Kawao N Hiramatsu K Inoi N Kuroda R Nishikawa H Sekiguchi F Kawabata A 《Peptides》2003,24(9):1449-1451
Protease-activated receptor-2 (PAR-2) is abundantly expressed in gastric mucosal chief cells, facilitating pepsinogen secretion. In the present study, we investigated whether PAR-1, a thrombin receptor, could modulate pepsinogen secretion in rats. The PAR-1-activating peptide TFLLR-NH(2) as well as the PAR-2-activating peptide SLIGRL-NH(2), administered i.v. repeatedly at 1-h intervals, significantly increased gastric pepsinogen secretion over 2-4 h (after two to four doses). In contrast, the control peptide FTLLR-NH(2), given in the same manner, had no such effect. Thus, PAR-1, like PAR-2, might function to facilitate pepsinogen secretion, suggesting a novel role of the thrombin-PAR-1-pathway in the stomach. 相似文献
96.
The coordinated migration of neurons is a pivotal step for functional architectural formation of the mammalian brain. To elucidate its molecular mechanism, gene transfer by means of in utero electroporation was applied in the developing murine brain, revealing the crucial roles of Rac1, its activators, STEF/Tiam1, and its downstream molecule, c-Jun N-terminal kinase (JNK), in the cerebral cortex. Functional repression of these molecules resulted in inhibition of radial migration of neurons without affecting their proper differentiation. Interestingly, distinct morphological phenotypes were observed; suppression of Rac1 activity caused loss of the leading process, whereas repression of JNK activity did not, suggesting the complexity of the signaling cascade. In cultured neurons from the intermediate zone, activated JNK was detected along microtubules in the processes. Application of a JNK inhibitor caused irregular morphology and increased stable microtubules in processes, and decreased phosphorylation of microtubule associated protein 1B, raising a possibility of the involvement of JNK in controlling tubulin dynamics in migrating neurons. Our data thus provide important clues for understanding the intracellullar signaling machinery for cortical neuronal migration. 相似文献
97.
98.
Microbial metalloproteases and pathogenesis 总被引:7,自引:0,他引:7
Zinc metalloproteases produced by human pathogenic microorganisms show a wide variety of pathological actions. In local infections, the proteases cause necrotic or hemorrhagic tissue damage through digestion of structural components of the ground substance, and also form edematous lesions through generation of inflammatory mediators, while in systemic infections, the proteases act as a synergistic virulence factor through disordered proteolysis of many plasma proteins. Clostridial neurotoxins, Bacteroides fragilis enterotoxin and Bacillus anthracis lethal factor are also zinc metalloproteases. 相似文献
99.
Sulfated sialyl-alpha-(2 --> 3)-neolactotetraose (IV3NeuAcnLcOse4) derivatives at C-6 of GlcNAc (6-O-sulfo), terminal Gal (6'-O-sulfo), and both GlcNAc and Gal (6,6'-di-O-sulfo) residues have systematically been synthesized. (Methyl 5-acetamido-4,7,8,9- tetra-O-acetyl-3,5-dideoxy-D-glycero-alpha-D-galacto-2-nonulopyranosy lonate)-(2 --> 3)-2,4-di-O-benzoyl-6-O-levulinoyl-D-galactopyranosyl trichloroacetimidate was coupled with 2-(trimethylsilyl)ethyl (2-acetamido-2-deoxy- 3-O-benzyl-6-O-p-methoxyphenyl-beta-D-glucopyranosyl)-(1 --> 3)-(2,4,6-tri-O-benzyl-beta-D-galactopyranosyl)-(1 --> 4)-2,3,6-tri-O-benzyl-beta-D-glucopyranoside to give the suitably protected pentasaccharide which, upon selective removal of the p-methoxyphenyl and/or levulinoyl groups at C-6 of the GlcNAc and the terminal Gal residues, successive O-sulfation(s) and deprotection, afforded the desired three sulfated IV3NeuAcnLcOse4 derivatives. Acceptor specificity of the synthetic IV3NeuAcnLcOse4 probes for a human alpha-(1 --> 3)-fucosyltransferase (Fuc-TVII) was examined to study the biosynthetic pathway of L-selectin ligand. Only the 6-sulfated derivative at C-6 of GlcNAc was recognized by Fuc-TVII to give 6-O-sulfo sialyl LeX. 相似文献
100.