全文获取类型
收费全文 | 755篇 |
免费 | 150篇 |
出版年
2022年 | 3篇 |
2021年 | 3篇 |
2020年 | 9篇 |
2019年 | 12篇 |
2018年 | 12篇 |
2017年 | 15篇 |
2016年 | 14篇 |
2015年 | 36篇 |
2014年 | 29篇 |
2013年 | 25篇 |
2012年 | 50篇 |
2011年 | 47篇 |
2010年 | 31篇 |
2009年 | 33篇 |
2008年 | 30篇 |
2007年 | 43篇 |
2006年 | 45篇 |
2005年 | 24篇 |
2004年 | 48篇 |
2003年 | 33篇 |
2002年 | 28篇 |
2001年 | 32篇 |
2000年 | 33篇 |
1999年 | 27篇 |
1998年 | 18篇 |
1997年 | 8篇 |
1996年 | 13篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 18篇 |
1991年 | 15篇 |
1990年 | 9篇 |
1989年 | 16篇 |
1988年 | 9篇 |
1987年 | 16篇 |
1986年 | 13篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1972年 | 5篇 |
1971年 | 3篇 |
1968年 | 4篇 |
1965年 | 3篇 |
排序方式: 共有905条查询结果,搜索用时 15 毫秒
1.
Y. Salas A. Márquez J. Canelón Y. Perazzo V. Colmenárez J. A. López 《Mycopathologia》2012,174(5-6):511-517
Pythium insidiosum is a pathogenic oomycete known since 1890 that causes pythiosis in mammals. In this report, seven P. insidiosum isolates were recovered from Venezuelan horses and were characterized. The strains were recovered from biopsied tissues and kunkers collected from granulomatous masses located on the hind limb and from a nodular lesion in the left upper eyelid, which decrease the ability of the horses to be used for working purposes. The methods used to identify P. insidiosum isolates were based on the production of sporangia and zoospores, histopathology and PCR assay. To further characterize these strains, portions of the 18S rRNA genes of the seven isolates were sequenced. The sequences showed high homology to previously described P. insidiosum DNA sequences available in GenBank. Similar studies based on the morphological, histological and molecular data identified the etiological agent in samples of granulomatous lesions in these equines as P. insidiosum. In America, the infection has been diagnosed more frequently in equines of Brazil, Colombia, Costa Rica and the United States of America. 相似文献
2.
Pedro J. I. Salas Dora E. Vega-Salas Enrique Rodriguez-Boulan 《The Journal of membrane biology》1987,98(3):223-236
Summary Madin-Darby canine kidney (MDCK) cells kept in suspension culture for 12–15 hr displayed high-affinity binding sites for125I-lathyritic (soluble) collagen (120,000/cell,K
D
=30nm) and preferred collagens types I and IV over laminin or fibronectin as substrates during the first hour of attachment. On the other hand, after 4 hr, attachment to all four substrates was equally efficient. Upon challenge with a collagen substrate, the high-affinity sites were rapidly recruited on it (T1/2=6 min). Their occupancy by soluble collagen triggered the exocytosis of a second large population of low-affinity collagen binding sites that included laminin and seems to be involved in a second cell-attachment mechanism. These results are compatible with a twostep model of MDCK cell attachment to the substrate: first, via high-affinity collagen binding sites, and second, via laminin of cellular origin. 相似文献
3.
4.
5.
C E Salas W G Ohlsson O Z Sellinger 《Biochemical and biophysical research communications》1977,76(4):1107-1115
The administration of a single convulsant dose or of multiple subconvulsant doses of L-methionine-dl-sulfoximine (MSO) to 18-day old rats results in a significant elevation of the specific activity of cerebral tRNA methyltransferases, as determined in an assay, using heterologous or species-homologous tRNAs as substrates. The increase was detectable as early as 90 min after MSO and persisted throughout the entire 5–6 h preconvulsant period. The 14[C]-methyl tRNA was purified, and hydrolyzed to its constituent bases and their distribution was quantitated by high performance liquid chromatography. A marked increase in the formation of 14[C]-N2-methyl- and 14[C]-N22-dimethyl guanine was noted in the MSO-treated animals, demonstrating a specific stimulation by MSO of the cerebral N2-methyl and/or N22-dimethyl guanine-specific tRNA methyltransferases. 相似文献
6.
7.
Abstract In the present study we compared the intracellular level of free calcium ([Ca2+ ]i ) and monomeric (G)/total (G + F) actin ratio in HeLa cells infected with diffuse (DAEC) and localised adherent Escherichia coli (LAEC). The level of [Ca2+ ]i was increased in both DAEC- and LAEC-infected HeLa cells. However, studies with EGTA- and dantrolene-treated cells and also suspension of cells in Ca2+ -free buffer suggested that the rise of [Ca2+ ]i in DAEC-infected cells was due to the influx of Ca2+ from extracellular medium, whereas Ca2+ mobilisation from the intracellular stores was responsible for the enhancement of [Ca2+ ]i in LAEC-infected cells. It was also evident that the infection of HeLa cells with DAEC and LAEC caused alteration of G / G + F actin ratio as compared to that of control cells. The ratio was much lower in LAEC-infected cells than that of DAEC-infected ones. Moreover, cytochalasin B inhibited both DAEC and LAEC invasion to HeLa cells, suggesting further the role of microfilaments in the invasion process. 相似文献
8.
Dora E. Vega-Salas Julio A. San Martino Pedro J.I. Salas Alberto Baldi 《Differentiation; research in biological diversity》1993,54(3):131-141
Abstract. We have previously shown that an integral plasma membrane glycoprotein (AP2) is highly polarized to the apical domain in confluent Madin-Darby canine kidney (MDCK) epithelial cells. However, when the monolayers are prevented from forming intercellular contacts, approximately 60% of the AP2 cellular content is stored in the intracellular vacuolar apical compartment (VAC). In the current work we found that AP2 was present in the non-tumorigenic human mammary epithelial cell line MCF-10A. in the breast carcinoma cell lines MCF-7 and T47D, and in breast ductal carcinomas in vivo. By radioimmunoassay, an intracellular Compartment of AP2 was identified in the mammary cell lines in culture. In MCF-10A, this compartment behaved as in MDCK cells; namely it was observed only when the cells cannot form cell-cell contacts. However, in the carcinoma cell lines MCF-7 and T47D, a significant AP2 intracellular compartment was observed also under conditions permissive for the formation of intercellular contacts. These results were confirmed by immunofluorescence and immunoelectron microscopy experiments that showed VACs in MCF-7 and T47D, even in cells with extensive intercellular contacts. In MCF-7 cells, the addition of serum caused a partial decrease of the AP2 intracellular compartment. The exocytosis of VACs occurred towards the center of multi-cellular groups, forming intercellular lumens, similar to those transiently observed in MDCK cells and to structures described by others during embryo development. Altogether, these results suggest that VAC exocytosis is controlled by cell-cell contact signalling, which may be defective in carcinoma cells. 相似文献
9.
10.
The phi 29 DNA polymerase, an alpha-like DNA polymerase, shows an inorganic pyrophosphate-dependent degradative activity with similar requirements to the corresponding one of Escherichia coli DNA polymerase I: (a) it requires a high concentration of inorganic pyrophosphate and is reversed by polymerization; (b) like DNA polymerization, it needs a duplex DNA with protruding 5' single-strand; (c) it acts in the 3' to 5' direction releasing free dNTPs, thus, it can be considered as the reversal of polymerization; (d) although a correctly base-paired 3' primer terminus is the preferred substrate, the pyrophosphorolytic activity is able to remove mismatched 3' ends. In agreement with the structural and functional model previously proposed for the phi 29 DNA polymerase, the analysis of point mutations has revealed that the pyrophosphorolytic activity, like the polymerization activity, is located at the C-terminal portion of the molecule, involving the amino acid motif YCDTD, highly conserved in alpha-like DNA polymerases. Furthermore, the analysis of phi 29 DNA polymerase mutants indicates that pyrophosphorolysis, like DNA polymerization, also requires an efficient translocation of the enzyme along the template. 相似文献