全文获取类型
收费全文 | 1123篇 |
免费 | 70篇 |
出版年
2022年 | 2篇 |
2021年 | 11篇 |
2020年 | 9篇 |
2019年 | 5篇 |
2018年 | 14篇 |
2017年 | 6篇 |
2016年 | 15篇 |
2015年 | 27篇 |
2014年 | 45篇 |
2013年 | 62篇 |
2012年 | 68篇 |
2011年 | 72篇 |
2010年 | 44篇 |
2009年 | 42篇 |
2008年 | 63篇 |
2007年 | 95篇 |
2006年 | 74篇 |
2005年 | 82篇 |
2004年 | 107篇 |
2003年 | 73篇 |
2002年 | 62篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 8篇 |
1998年 | 18篇 |
1997年 | 14篇 |
1996年 | 12篇 |
1995年 | 13篇 |
1994年 | 10篇 |
1993年 | 7篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 9篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1982年 | 12篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1972年 | 3篇 |
排序方式: 共有1193条查询结果,搜索用时 31 毫秒
71.
Watanabe H Adachi R Hirayama A Kasahara T Suzuki K 《Biochemical and biophysical research communications》2003,306(1):26-31
Triphenyltin (TPT) is an environmental endocrine disruptor and toxic substance, but little information is available on its immunological effects. To assess the effect of TPT on leukocyte differentiation, we investigated its effect on the neutrophilic differentiation of HL-60 cells induced by dimethyl sulfoxide and granulocyte colony-stimulating factor (G-CSF) for 6 days. At a low concentration, 10(-7)M, TPT increased superoxide production by differentiated HL-60 cells stimulated with opsonized zymosan (OZ) by about 45% and increased expression of CD18, a component of the OZ-receptor, by about 90%. Real-time PCR analysis revealed that TPT augmented the expression not only of CD18 but also of components of superoxide-generating NADPH-oxidase, p47phox, 2.7-fold, and p67phox, 2.0-fold, and of granulocyte colony-stimulating factor receptor (G-CSFR), 3.0-fold, whereas various other endocrine disruptors, including parathion, vinclozolin, and bisphenol A, had no such enhancing effects. The results of a DNA macroarray analysis showed that TPT enhanced the expression of G-CSFR and certain other neutrophil functional proteins, including CD14 and myeloid leukemia cell differentiation protein (MCL-1), and that TPT induced a decrease in expression of LC-PTP, leukocyte protein-tyrosine phosphatase, to about half the control level. The TPT-dependent suppression of LC-PTP was confirmed by real-time PCR analysis, and the results of immunoblotting indicated that TPT enhances the expression of myeloid specific tyrosine kinase hck by about 30% at the protein level, and this together with the reduction of LC-PTP may enhance tyrosine phosphorylation, in turn resulting in enhancement of superoxide production. These findings suggest that TPT may have an enhancing effect on the neutrophilic maturation of leukocytes. 相似文献
72.
During the ATP hydrolysis cycle of the Dictyostelium myosin II motor domain, two conserved alpha-helices, the SH1/SH2 helix and the relay helix, rotate in a coordinated way to induce the swing motion of the converter domain. A network of hydrophobic and ionic interactions in these two helices and the converter may ensure that the motions of these helices are effectively transmitted to the converter. To examine the roles of these interactions in the ATPase-dependent converter swing, we disrupted two conserved hydrophobic linkages among them by means of a point mutation (I499A or F692A). The resulting mutations induced only limited changes in the kinetic parameters of ATP hydrolysis, except for a marked increase of basal MgATPase activity. However, the mutant myosins completely lost their in vitro and in vivo motor functions. Measurements of the intrinsic tryptophan fluorescence and the GFP-based FRET revealed that the converter domain of these mutants did not swing during steady-state ATP hydrolysis or in the presence of tightly trapped Mg.ADP.V(i), which shows that the point mutations induced the uncoupling of the converter swing and ATP hydrolysis cycle. These results highlight the importance of these hydrophobic linkages for transmitting the coordinated twist motions of the helices to the converter as well as the requirement of this converter swing for force generation. 相似文献
73.
Bach1 functions as a hypoxia-inducible repressor for the heme oxygenase-1 gene in human cells 总被引:4,自引:0,他引:4
74.
Phagocytes play a central role in the host defense system, and the relationship between the mechanism of their activation and cytoskeletal reorganization has been studied. We have previously reported a possible involvement of cofilin, an actin-binding protein, in phagocyte functions through its phosphorylation/dephosphorylation and translocation to the plasma membrane regions. In this work, we have obtained a new line of evidence showing an important role of cofilin in phagocyte functions using the mouse macrophage cell line J774.1 and an antisense oligonucleotide to cofilin. Upon stimulation with opsonized zymosan (OZ), cofilin was phosphorylated, and it accumulated around phagocytic vesicles. As the antisense oligonucleotide to cofilin, a 20-mer S-oligo corresponding to the sequence including the AUG translational initiation site was found to be effective. In the cells treated with the antisense oligonucleotide, the amount of cofilin was less than 30% of that in the control cells, and the level of F-actin was two or three times higher than that in the control cells before and throughout the cell activation. In the antisense oligonucleotide-treated cells, OZ-triggered superoxide production was three times faster than that in the control cells. Furthermore, phagocytosis of OZ was enhanced by the antisense. These results show that cofilin plays an essential role in the control of phagocyte function through regulation of actin filament dynamics. 相似文献
75.
Sashio H Tamura K Ito R Yamamoto Y Bamba H Kosaka T Fukui S Sawada K Fukuda Y Tamura K Satomi M Shimoyama T Furuyama J 《Immunogenetics》2002,53(12):1020-1027
The importance of tumor necrosis factor (TNF)-alpha and the TNF receptor gene polymorphisms in the etipathogenesis of inflammatory bowel disease (IBD) has not been elucidated. DNA from peripheral blood samples was obtained from 124 patients with Crohn's disease (CD), 106 patients with ulcerative colitis (UC), and 111 unrelated healthy controls. We examined two single nucleotide polymorphisms (SNPs) of the TNF-alpha gene, TNF (-308 G/A and -238 G/A), an SNP of the TNF receptor superfamily member 1A gene, TNFRSF1A(also known as TNFR1), at codon 12 in exon 1 (CCA/CCG), and two SNPs of the 1B gene, TNFRSF1B (also known as TNFR2), (1466 A/G and 1493 C/T). There was a difference in the carrier frequency for haplotype AG (-308 A, -238 G) between UC patients and the controls (OR=4.76, 95% CI=1.53-14.74, P<0.01). We found a significant difference in carrier frequency for haplotype AT (1466 A, 1493 T) of the TNFRSF1B gene between CD patients and the controls (OR=2.13, 95% CI=1.08-4.21, P<0.05). The significance proved to be greater in CD patients with both internal and external fistula (OR=4.8, 95% CI=1.73-13.33, P<0.01), and in those who were poor responders ( n=22) to our treatments, which consisted of nutritional therapy, medical therapy and surgical therapy (OR=9.24, 95% CI=3.37-25.36, P<0.001). This study suggests that one of the genes responsible for UC may be the TNF gene, or an adjacent gene, and that TNFRSF1B gene polymorphisms contribute greatly to the increased onset risk of CD and to the disease behavior. 相似文献
76.
Two blazeispirane derivatives including blazeispirols G and I were isolated from the cultured mycelia of the fungus Agaricus blazei Murill and were established to be (20S, 22S, 23R, 24S)-14 beta,22: 22,25-diepoxy-5-methoxy-des-A-ergosta-5,7,9-triene-11 alpha,23-diol and (20S, 22S, 23R, 24S)-14 beta,22:22,25-diepoxy-5-methoxy-des-A-ergosta-5,7,9,11-tetraene-23,28-diol by comparison of extensive 1D and 2D NMR spectral data with that of blazeispirol A. Furthermore, four blazeispirol derivatives blazeispirols, U, V, V(1) and Z(1) were isolated form the same source described above. Their structures were determined to be (20S, 22S, 23R, 24S)-14 beta,22:22,25-diepoxy-23-hydroxyergosta-4,6,8,11-tetraen-3-one, (20S, 22S, 23R, 24S)-14 beta,22:22,25-diepoxy-6 alpha,7 alpha,23-trihydroxyergosta-4,8,11-trien-3-one, (20S, 22S, 23R, 24S)-14 beta,22:22,25-diepoxy-6 beta,7 alpha,23-trihydroxyergosta-4,8,11-trien-3-one and (20S, 22S, 23R, 24S)-14 beta,22:22,25-diepoxy-23-hydroxy-4,5-seco-ergosta-6,8-diene-3,5-dione by extensive 1 D and 2D NMR spectral data. 相似文献
77.
Cysteinyl residues in proteins were alkylated with acrylamide during sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) to yield a thioether derivative, cys-S-beta-propionamide (PAM cys). The process was termed in situ alkylation with acrylamide. Using this method, the recovery of PAM-cys peptides from bovine serum albumin (BSA) was 88.6% at 10 picomol in one-dimensional (1-D) SDS-PAGE and 97.1% at 50 picomol in two-dimensional (2-D) SDS-PAGE. The coverage of tryptic peptide of BSA in 1-D and 2-D SDS-PAGE was 83.7% and 81.1%, respectively. The advantages of in situ alkylation with acrylamide were the following: (i) cysteinyl peptides were effectively derived in a single PAM cys and then proteins were precisely identified using databases; (ii) marked reduction of salts compared with post alkylation, e.g., using carboxymethylamide (CAM), resulting in higher signal intensity and wider coverage of cysteinyl peptides from PAM cys, compared with those of CAM derivatives, in mass spectrometry peptide mapping; and (iii) shorter duration by excluding the processes of post alkylation and desalting before peptide mapping. 相似文献
78.
Now that the sequences of many genomes are available, methods are required for the rapid identification of functional genes. We describe here a simple system for the isolation of genes that function in the tumor necrosis factor-alpha (TNF-alpha)-mediated pathway of apoptosis, using RNA helicase-associated ribozyme libraries with randomized substrate-binding arms. Because target-site accessibility considerably limits the effective use of intracellular ribozymes, the effectiveness of a conventional ribozyme library has been low. To overcome this obstacle, we attached to ribozymes an RNA motif (poly(A)-tail) able to interact with endogenous RNA helicase(s) so that the resulting helicase-attached, hybrid ribozymes can more easily attack target sites regardless of their secondary or tertiary structures. When the phenotype of cells changes upon introduction of a ribozyme library, genes responsible for these changes may be identified by sequencing the active ribozyme clones. In the case of TNF-alpha-mediated apoptosis, when a ribozyme library was introduced into MCF-7 cells, surviving clones were completely or partially resistant to TNF-alpha-induced apoptosis. We identified many pro-apoptotic genes and partial sequences of previously uncharacterized genes using this method. Our gene discovery system should be generally applicable to the identification of functional genes in various systems. 相似文献
79.
Role of the Rab GTP-binding protein Ypt3 in the fission yeast exocytic pathway and its connection to calcineurin function
下载免费PDF全文
![点击此处可从《Molecular biology of the cell》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Cheng H Sugiura R Wu W Fujita M Lu Y Sio SO Kawai R Takegawa K Shuntoh H Kuno T 《Molecular biology of the cell》2002,13(8):2963-2976
A genetic screen for mutations synthetically lethal with fission yeast calcineurin deletion led to the identification of Ypt3, a homolog of mammalian Rab11 GTP-binding protein. A mutant with the temperature-sensitive ypt3-i5 allele showed pleiotropic phenotypes such as defects in cytokinesis, cell wall integrity, and vacuole fusion, and these were exacerbated by FK506-treatment, a specific inhibitor of calcineurin. Green fluorescent protein (GFP)-tagged Ypt3 showed cytoplasmic staining that was concentrated at growth sites, and this polarized localization required the actin cytoskeleton. It was also detected as a punctate staining in an actin-independent manner. Electron microscopy revealed that ypt3-i5 mutants accumulated aberrant Golgi-like structures and putative post-Golgi vesicles, which increased remarkably at the restrictive temperature. Consistently, the secretion of GFP fused with the pho1(+) leader peptide (SPL-GFP) was abolished at the restrictive temperature in ypt3-i5 mutants. FK506-treatment accentuated the accumulation of aberrant Golgi-like structures and caused a significant decrease of SPL-GFP secretion at a permissive temperature. These results suggest that Ypt3 is required at multiple steps of the exocytic pathway and its mutation affects diverse cellular processes and that calcineurin is functionally connected to these cellular processes. 相似文献
80.
So Nishikawa Kazuaki Homma Yasunori Komori Mitsuhiro Iwaki Tetsuichi Wazawa Atsuko Hikikoshi Iwane Junya Saito Reiko Ikebe Eisaku Katayama Toshio Yanagida Mitsuo Ikebe 《Biochemical and biophysical research communications》2002,290(1):311-317
Among a superfamily of myosin, class VI myosin moves actin filaments backwards. Here we show that myosin VI moves processively on actin filaments backwards with large ( approximately 36 nm) steps, nevertheless it has an extremely short neck domain. Myosin V also moves processively with large ( approximately 36 nm) steps and it is believed that myosin V strides along the actin helical repeat with its elongated neck domain that is critical for its processive movement with large steps. Myosin VI having a short neck cannot take this scenario. We found by electron microscopy that myosin VI cooperatively binds to an actin filament at approximately 36 nm intervals in the presence of ATP, raising a hypothesis that the binding of myosin VI evokes "hot spots" on actin filaments that attract myosin heads. Myosin VI may step on these "hot spots" on actin filaments in every helical pitch, thus producing processive movement with 36 nm steps. 相似文献