全文获取类型
收费全文 | 106篇 |
免费 | 6篇 |
专业分类
112篇 |
出版年
2022年 | 3篇 |
2021年 | 1篇 |
2016年 | 6篇 |
2015年 | 6篇 |
2014年 | 4篇 |
2013年 | 16篇 |
2012年 | 2篇 |
2011年 | 4篇 |
2010年 | 4篇 |
2009年 | 5篇 |
2008年 | 7篇 |
2007年 | 4篇 |
2006年 | 4篇 |
2005年 | 1篇 |
2004年 | 3篇 |
2003年 | 6篇 |
2002年 | 3篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 6篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1977年 | 2篇 |
排序方式: 共有112条查询结果,搜索用时 0 毫秒
41.
The conjugative transfer of F-like plasmids is repressed by FinO, an RNA binding protein. FinO interacts with the F-plasmid encoded traJ mRNA and its antisense RNA, FinP, stabilizing FinP against endonucleolytic degradation and facilitating sense-antisense RNA recognition. Here we present the 2.0 A resolution X-ray crystal structure of FinO, lacking its flexible N-terminal extension. FinO adopts a novel, elongated, largely helical conformation. An N-terminal region, previously shown to contact RNA, forms a positively charged alpha-helix (helix 1) that protrudes 45 A from the central core of FinO. A C-terminal region of FinO that is implicated in RNA interactions also extends out from the central body of the protein, adopting a helical conformation and packing against the base of the N-terminal helix. A highly positively charged patch on the surface of the FinO core may present another RNA binding surface. The results of an in vitro RNA duplexing assay demonstrate that the flexible N-terminal region of FinO plays a key role in FinP-traJ RNA recognition, and supports our proposal that this region and the N-terminus of helix 1 interact with and stabilize paired, complementary RNA loops in a kissing complex. 相似文献
42.
Rohinton Edalji Tami J. Pilot-Matias Steven D. Pratt David A. Egan Jean M. Severin Earl G. Gubbins Andrew M. Petros Stephen W. Fesik Neal S. Burres Thomas F. Holzman 《Journal of Protein Chemistry》1992,11(3):213-223
The human peptidyl-prolyl isomerase FK-binding protein (FKBP) was cloned as a fusion partner with CMP-KDO synthetase (CKS), and the resultant construct was characterized as an improved high-expression source for FKBP. The CKS-FKBP fusion was expressed as a soluble protein at levels approaching 1 gm/L inEscherichia coli fermentations. The fusion protein was purified to near homogeneity by a one-step ammonium sulfate fractionation of whole cell lysate. After selective cleavage, the fusion precursor produced yields approaching 300 mg of purified FKBP per liter of harvested culture, a 30 to 60-fold increase over that observed for a nonfusion construct. Selective cleavage of the fusion partners was accomplished using either hydroxylamine or specific, limited proteolysis. Once separated from the CKS fusion partner, the FKBP was isolated in a single step by either reversed-phase HPLC or chromatography on Q-Sepharose. For comparison of physical and chemical properties, a nonfusion construct of recombinant human FKBP was expressed inE. coli and isolated. The purified FKBPs exhibited expected SDS-PAGE molecular weights and N-terminal sequences. The proteins had similar proton NMR spectra and binding to [3H]FK-506. The fusion construct, CKS-FKBP, was also found to bind [3H]FK-506. These data indicate that FKBP fused to the C-terminus of CKS folds independently of the fusion partner and suggests the fused FKBP adopts a conformation resembling that of the native protein. 相似文献
43.
Molecular evidence places the swallow bug genus Oeciacus Stål within the bat and bed bug genus Cimex Linnaeus (Heteroptera: Cimicidae) 下载免费PDF全文
The genera Cimex Linnaeus and Oeciacus Stål (Heteroptera: Cimicidae) are common haematophagous ectoparasites of bats or birds in the Holarctic region. Both their phylogenetic relationship and the systematics of the entire family previously were based on data from morphology and host relationships. Relationships among nine species of the genus Cimex and three species of the genus Oeciacus were analysed here using two mitochondrial and three nuclear genes. Cimex was shown to be paraphyletic with respect to Oeciacus. Oeciacus is thus proposed as a synonym of Cimex. The characteristic phenotype of Oeciacus results from the specific host association with different species of swallows (Hirundinidae). The morphological characters that have been used as diagnostic for the genera were shown to be valid and can be further used for determination at species level. The present analyses recovered the four traditional morphologically defined species groups of the genus Cimex. However, their relationships were poorly resolved – only the C. hemipterus group showed a well‐supported relationship to the C. pipistrelli group. The molecular differentiation within the Palaearctic C. pipistrelli and the Nearctic C. pilosellus species groups correlates with their karyotype differentiation. Furthermore, the analyses suggest poly‐ or paraphyly of the former genus Oeciacus. Either way this indicates there is a large amount of host‐associated phenotypic convergence in either bat‐ or bird‐associated groups of species. The probability of host choice and subsequent switch in Cimicidae are discussed and possible scenarios of the evolution of host association in species of Cimex are suggested. 相似文献
44.
Kyriaki Giorgakoudi Simon Gubbins John Ward Nicholas Juleff Zhidong Zhang David Schley 《PloS one》2015,10(10)
Foot-and-mouth disease (FMD) is a highly contagious disease of cloven-hoofed animals. FMD virus (FMDV) shows a strong tropism for epithelial cells, and FMD is characterised by cell lysis and the development of vesicular lesions in certain epithelial tissues (for example, the tongue). By contrast, other epithelial tissues do not develop lesions, despite being sites of viral replication (for example, the dorsal soft palate). The reasons for this difference are poorly understood, but hypotheses are difficult to test experimentally. In order to identify the factors which drive cell lysis, and consequently determine the development of lesions, we developed a partial differential equation model of FMDV infection in bovine epithelial tissues and used it to explore a range of hypotheses about epithelium structure which could be driving differences in lytic behaviour observed in different tissues. Our results demonstrate that, based on current parameter estimates, epithelial tissue thickness and cell layer structure are unlikely to be determinants of FMDV-induced cell lysis. However, differences in receptor distribution or viral replication amongst cell layers could influence the development of lesions, but only if viral replication rates are much lower than current estimates. 相似文献
45.
46.
47.
S. Gubbins C. A. Gilligan 《Proceedings. Biological sciences / The Royal Society》1997,264(1379):227-232
Persistence is a central issue in population ecology with important implications for population management. Most theoretical studies have focused on continually interacting populations, even though many systems are subject to ecological disturbances which confound analysis of persistence. In this paper, we use a combination of a simple parasite–hyperparasite model with disturbances and field data to investigate the factors contributing to the observed persistence of the parasite population. The field data are taken from a two-year experiment (including five growing seasons) investigating the use of the mycoparasite Sporidesmium sclerotivorum as a persistent biological control agent of Sclerotinia minor, an economically important fungal parasite of lettuce. We show that the standard assumption of homogeneous mixing fails to predict the observed persistence of the parasite population. We demonstrate that allowing for heterogeneous mixing prevents the fade-out predicted in the homogeneous mixing case. The implications of the results for broad classes of host–parasite systems are discussed. 相似文献
48.
NETTA DORCHIN JOHN H. HOFFMANN WENDY A. STIRK ONDŘEJ NOVÁK MIROSLAV STRNAD JOHANNES VAN STADEN 《Physiological Entomology》2009,34(4):359-369
Sexually dimorphic galls are rare among gall‐inducing insects and the reason for their occurrence is unknown. The pteromalid wasp Trichilogaster acaciaelongifoliae, which induces galls on Acacia longifolia, is one such species. In the present study, the anatomical and physiological attributes of male and female galls of T. acaciaelongifoliae are examined and compared. Histological preparations are used to characterize anatomical differences between male and female gall chambers. Bioassays, high‐performance liquid chromatography‐mass spectrometry and an enzyme immunoassay are used to measure concentrations of auxin and cytokinin in normal buds, galled tissues, and larvae of both sexes. Female chambers are found to be 3.3‐fold larger, and are associated with 1.5‐fold more storage tissue and 3.5‐fold more vascular tissues than male chambers. Tissues from female chambers induce stronger cytokinin‐like bioactivity than tissues from male chambers. Female larvae have considerably higher concentrations of cytokinin free bases, ribosides, glucosides and monophosphates than male larvae; higher auxin‐like bioactivity than in normal or galled plant tissues; and almost twice the concentration of auxin than male larvae. Both male and female larvae contain much higher auxin concentrations than either galled or normal plant tissues. These findings suggest that differing levels of phytohormones are involved in the development of sexual dimorphism of gall structures in this species. 相似文献
49.
In this article, we review how pressure effects in pores affect both the physics of the confined fluid and the properties of the host porous material. Molecular simulations in which high-pressure effects were observed are first discussed; we will see how the strong dependence on bulk phase pressure of the freezing temperature of a fluid confined in nanopores can be explained by important variations of the pressure within the pore. We then discuss recent works in which direct calculations of the pressure tensor of fluids confined in pores provide evidence for large pressure enhancements. Finally, practical applications of these pressure effects in which gas adsorption in microporous solids (pore size < 2 nm) was found to enhance their mechanical properties by increasing the elastic modulus by a factor 4 are discussed. 相似文献
50.
Camille Szmaragd Anthony J. Wilson Simon Carpenter James L. N. Wood Philip S. Mellor Simon Gubbins 《PloS one》2010,5(2)