全文获取类型
收费全文 | 1651篇 |
免费 | 158篇 |
国内免费 | 1篇 |
出版年
2023年 | 17篇 |
2022年 | 37篇 |
2021年 | 89篇 |
2020年 | 46篇 |
2019年 | 48篇 |
2018年 | 69篇 |
2017年 | 50篇 |
2016年 | 84篇 |
2015年 | 118篇 |
2014年 | 123篇 |
2013年 | 114篇 |
2012年 | 167篇 |
2011年 | 140篇 |
2010年 | 73篇 |
2009年 | 61篇 |
2008年 | 81篇 |
2007年 | 52篇 |
2006年 | 52篇 |
2005年 | 42篇 |
2004年 | 47篇 |
2003年 | 32篇 |
2002年 | 29篇 |
2001年 | 13篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1981年 | 4篇 |
1977年 | 4篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1971年 | 4篇 |
1970年 | 5篇 |
1969年 | 5篇 |
1968年 | 12篇 |
1966年 | 8篇 |
1964年 | 7篇 |
1963年 | 7篇 |
1960年 | 7篇 |
1959年 | 7篇 |
1958年 | 7篇 |
1957年 | 5篇 |
1955年 | 4篇 |
1953年 | 5篇 |
1951年 | 5篇 |
1950年 | 4篇 |
1949年 | 4篇 |
排序方式: 共有1810条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Internalization and degradation of peptides of the bombesin family in Swiss 3T3 cells occurs without ligand-induced receptor down-regulation. 总被引:3,自引:1,他引:2 下载免费PDF全文
The binding of [125I]gastrin releasing peptide ([125I]GRP) to Swiss 3T3 cells at 37 degrees C increases rapidly, reaching a maximum after 30 min and decreasing afterwards. The decrease in cell-associated radioactivity at this temperature is accompanied by extensive degradation of the labelled peptide. At 4 degrees C equilibrium binding is achieved after 6 h and [125I]GRP degradation is markedly inhibited. Extraction of surface-bound ligand at low pH demonstrates that the iodinated peptide is internalized within minutes after addition to 3T3 cells at 37 degrees C. The rate of internalization is strikingly temperature-dependent and is virtually abolished at 4 degrees C. In addition, lysomotropic agents including chloroquine increase the cell-associated radioactivity in cells incubated with [125I]GRP. The binding of [125I]GRP to Swiss 3T3 cells was not affected by pretreatment for up to 24 h with either GRP or bombesin at mitogenic concentrations. Furthermore, pretreatment with GRP did not reduce the affinity labelling of a Mr 75,000-85,000 surface protein recently identified as a putative receptor for bombesin-like peptides. These results demonstrate that while peptides of the bombesin family are rapidly internalized and degraded by Swiss 3T3 cells, the cell surface receptors for these molecules are not down-regulated. 相似文献
5.
Characterization of a bombesin receptor on Swiss mouse 3T3 cells by affinity cross-linking 总被引:3,自引:0,他引:3
We have previously identified by chemical cross-linking a cell surface protein in Swiss 3T3 cells of apparent Mr 75,000-85,000, which may represent a major component of the receptor for peptides of the bombesin family in these cells. Because bombesin-like peptides may interact with other cell surface molecules, it was important to establish the correlation between receptor binding and functions of this complex and further characterize the Mr 75,000-85,000 cross-linked protein. Detailed time courses carried out at different temperatures demonstrated that the Mr 75,000-85,000 affinity-labelled band was the earliest cross-linked complex detected in Swiss 3T3 cells incubated with 125I-labelled gastrin-releasing peptide (125I-GRP). Furthermore, the ability of various nonradioactive bombesin agonists and antagonists to block the formation of the Mr 75,000-85,000 cross-linked complex correlated extremely well (r = 0.994) with the relative capacity of these peptides to inhibit 125I-GRP specific binding. Pretreatment with unlabelled GRP for up to 6 h caused only a slight decrease in both specific 125I-GRP binding and the affinity labelling of the Mr 75,000-85,000 protein. We also show that the cross-linked complex is a glycoprotein. First, solubilized affinity labelled Mr 75,000-85,000 complex applied to wheat germ lectin-sepharose columns was eluted by addition of 0.3 M N-acetyl-D-glucosamine. Second, treatment with endo-beta-N-acetylglucosaminidase F reduced the apparent molecular weight of the affinity-labelled band from 75,000-85,000 to 43,000, indicating the presence of N-linked oligosaccharide groups. 相似文献
6.
7.
The mitotic and biosynthetic activities of the marginal and plate meristems were studied during the entire course of leaf development of Xanthium pennsylvanicum. In contrast to statements in the literature, marginal meristem activity is long in duration, as assayed by the mitotic counts and H3-thymidine incorporation. This me istem is active 23 days. The plate meristem is active for an additional 3 days after cessation of cell division in the marginal meristem, but the total duration of its mitotic activity is also approximately 23 days. Numerous periclinal cell divisions of the plate meristem form additional cell layers and contribute to the growth of the lamina in thickness. Incorporation of H3-thymidine increased during the course of leaf development. Cells between plastochronic ages 0 and 2.0 incorporated more of the radioisotopic precursor than those of younger leaf primordia. The uptake and incorporation of H3-thymidine into nuclear DNA was more sluggish during the early stages of development than in the more expanded leaves. No DNA synthesis was demonstrated after cessation of cell division in the leaf lamina. Metabolic or endomitotic DNA synthesis after leaf plastochron index (LPI) 3.0 seems improbable. No significant differences in the incorporation of H3-thymidine could be demonstrated between the marginal and plate meristems. This would indicate no distinct biosynthetic differences between the two meristems. The definitions of the marginal and plate meristems of Xanthium leaves were formulated in view of the above findings. 相似文献
8.
Characteristics of a slime-producing bacterium isolated from living and dead gypsy moth larvae were determined. The bacterium was found to be a motile, gram-negative rod, which fermented glucose, but not lactose. It was oxidase-negative, hydrolyzed urea, deaminated phenylalanine and produced H2S. These characteristics are common to several members of the genusProteus. In addition to the unique feature of slime production, a biochemical comparison with other members of the genus showed that it differed markedly from described species ofProteus; thus the new speciesProteus myxofaciens was proposed. 相似文献
9.
L L Cherup L S Zachary L J Gottlieb C A Petti 《Plastic and reconstructive surgery》1990,85(6):898-902
The radial forearm flap has become a versatile flap for upper extremity reconstruction. The use of the forearm flap for hand reconstruction in the patient with previously burned forearms has not been widely appreciated. In those patients whose forearms have been previously split-thickness skin-grafted on fascia, we have employed the reverse radial forearm flap as a skin graft-fascial flap for hand reconstruction and have obtained excellent functional results. Three patients at various intervals postburn are presented to demonstrate use of this flap for wrist contracture release, coverage of arthroplasties, first web space contracture release, and acute salvage of phalanges and tendons. Assessment of the hand's vascular anatomy and careful treatment of the donor area have contributed to no added morbidity and an excellent aesthetic result at the donor site. 相似文献
10.