全文获取类型
收费全文 | 141篇 |
免费 | 11篇 |
出版年
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 4篇 |
2012年 | 8篇 |
2011年 | 5篇 |
2010年 | 1篇 |
2009年 | 5篇 |
2008年 | 5篇 |
2007年 | 6篇 |
2006年 | 4篇 |
2005年 | 3篇 |
2004年 | 3篇 |
2003年 | 1篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 10篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 2篇 |
排序方式: 共有152条查询结果,搜索用时 93 毫秒
41.
From 1981 through 1986, plasma or serum samples were obtained from 322 wild turkeys (Meleagris gallopavo) from Georgia (n = 111), Kentucky (n = 21), Louisiana (n = 22), North Carolina (n = 118), Tennessee (n = 19), Missouri (n = 24) and Iowa (n = 7). These samples were tested for antibodies to Mycoplasma gallisepticum (MG) and in most instances, M. synoviae (MS), M. meleagridis (MM), and avian influenza (AI) virus. All 322 turkeys were seronegative for MG by the rapid plate agglutination (RPA) test. All of a subsample (n = 147) also were negative (titer less than or equal to 1:40) for MG by the hemagglutination inhibition (HI) test. Five of 253 turkeys (2%) were seropositive (+4 reaction) for MS by the RPA test; however, HI tests for MS on these five turkeys were negative as were attempts to isolate MS from trachea and homogenized lung tissue. Three of 253 turkeys (1%) were seropositive (+1 to +3 reactions) for MM by the RPA test. None of 210 turkeys had antibodies to AI by the agar gel precipitation test. These data suggest that populations of native eastern wild turkeys are not important in the epizootiology of MG, MS, MM, or AI. 相似文献
42.
In situ gelation of injectable polypeptide-based materials is attractive for minimally invasive in vivo implantation of biomaterials and tissue engineering scaffolds. We demonstrate that chemically cross-linked elastin-like polypeptide (ELP) hydrogels can be rapidly formed in aqueous solution by reacting lysine-containing ELPs with an organophosphorous cross-linker, beta-[tris(hydroxymethyl)phosphino]propionic acid (THPP) under physiological conditions. The mechanical properties of the cross-linked ELP hydrogels were largely modulated by the molar concentration of lysine residues in the ELP and the pH at which the cross-linking reaction was carried out. Fibroblasts embedded in ELP hydrogels survived the cross-linking process and were viable after in vitro culture for 3 days. DNA quantification of ELP hydrogels with encapsulated fibroblasts indicated that there was no significant difference in DNA content between day 0 and day 3 when ELP hydrogels were formed with an equimolar ratio of THPP and lysine residues of the ELPs. These results suggest that THPP cross-linking may be a biocompatible strategy for the in situ formation of cross-linked hydrogels. 相似文献
43.
Sylvie Ducki Grant Mackenzie Ben Greedy Simon Armitage Jérémie Fournier Dit Chabert Elizabeth Bennett Jim Nettles James P. Snyder Nicholas J. Lawrence 《Bioorganic & medicinal chemistry》2009,17(22):7711-7722
Tubulin is an important molecular target in cancer chemotherapy. Antimitotic agents able to bind to the protein are currently under study, commonly used in the clinic to treat a variety of cancers and/or exploited as probes to investigate the protein’s structure and function. Here we report the binding modes for a series of colchicinoids, combretastatin A4 and chalcones established from docking studies carried out on the structure of tubulin in complex with colchicine. The proposed models, in agreement with published biochemical data, show that combretastatin A4 binds to the colchicine site of β-tubulin and that chalcones assume an orientation similar to that of podophyllotoxin. The models can be used to design a new class of podophyllotoxin mimics, the α-aryl chalcones, capable of binding to the colchicine-binding site of β-tubulin with higher affinity. 相似文献
44.
C Adam Middleton Upendra Nongthomba Katherine Parry Sean T Sweeney John C Sparrow Christopher JH Elliott 《BMC biology》2006,4(1):17-14
Background
The processes by which eggs develop in the insect ovary are well characterized. Despite a large number of Drosophila mutants that cannot lay eggs, the way that the egg is moved along the reproductive tract from ovary to uterus is less well understood. We remedy this with an integrative study on the reproductive tract muscles (anatomy, innervation, contractions, aminergic modulation) in female flies. 相似文献45.
Magne D Palmer G Barton JL Mézin F Talabot-Ayer D Bas S Duffy T Noger M Guerne PA Nicklin MJ Gabay C 《Arthritis research & therapy》2006,8(3):R80-11
Six novel members of the IL-1 family of cytokines were recently identified, primarily through the use of DNA database searches for IL-1 homologues, and were named IL-1F5 to IL-1F10. In the present study, we investigated the effect of IL-1F8 on primary human joint cells, and examined the expression of the new IL-1 family members in human and mouse joints. Human synovial fibroblasts (hSFs) and human articular chondrocytes (hACs) expressed the IL-1F8 receptor (IL-1Rrp2) and produced pro-inflammatory mediators in response to recombinant IL-1F8. IL-1F8 mRNA expression was increased in hSFs upon stimulation with proinflammatory cytokines, whereas in hACs IL-1F8 mRNA expression was constitutive. However, IL-1F8 protein was undetectable in hSF and hAC culture supernatants. Furthermore, although IL-1beta protein levels were increased in inflamed human and mouse joint tissue, IL-1F8 protein levels were not. IL-1F8 levels in synovial fluids were similar to or lower than those in matched serum samples, suggesting that the joint itself is not a major source of IL-1F8. Serum levels of IL-1F8 were similar in healthy donors, and patients with rheumatoid arthritis, osteoarthritis and septic shock, and did not correlate with inflammatory status. Interestingly however, we observed high IL-1F8 levels in several serum samples in all groups. In conclusion, IL-1F8 exerts proinflammatory effects in primary human joint cells. Joint and serum IL-1F8 protein levels did not correlate with inflammation, but they were high in some human serum samples tested, including samples from patients with rheumatoid arthritis. It remains to be determined whether circulating IL-1F8 can contribute to joint inflammation in rheumatoid arthritis. 相似文献
46.
Photo-crosslinkable dendritic macromolecules are attractive materials for the preparation of cartilage tissue engineering scaffolds that may be optimized for in situ formation of hydrated, mechanically stable, and well-integrated hydrogel scaffolds supporting chondrocytes and chondrogenesis. We designed and synthesized a novel hydrogel scaffold for cartilage repair, based on a multivalent and water-soluble tri-block copolymer consisting of a poly(ethylene glycol) core and methacrylated poly(glycerol succinic acid) dendrimer terminal blocks. The terminal methacrylates allow mild and biocompatible photo-crosslinking with a visible light, facilitating in vivo filling of irregularly shaped defects with the dendrimer-based scaffold. The multivalent dendrimer constituents allow high crosslink densities that inhibit swelling after crosslinking while simultaneously introducing biodegradation sites. The mechanical properties and water content of the hydrogel can easily be tuned by changing the biodendrimer concentration. In vitro chondrocyte encapsulation studies demonstrate significant synthesis of neocartilaginous material, containing proteoglycans and type II collagen. 相似文献
47.
Bradley RD; Adkins RM; Honeycutt RL; McDonald JH 《Molecular biology and evolution》1998,15(6):709-717
Using the strictly neutral model as a null hypothesis, we tested for
deviations from expected levels of nucleotide polymorphism at the alcohol
dehydrogenase locus (Adh-1) within and among four species of pocket gophers
(Geomys bursarius major, G. knoxjonesi, G. texensis llanensis, and G.
attwateri). The complete protein-encoding region was examined, and 10
unique alleles, representing both electromorphic and cryptic alleles, were
used to test hypotheses (e.g., the neutral model) concerning the
maintenance of genetic variation. Nineteen variable sites were identified
among the 10 alleles examined, including 9 segregating sites occurring in
synonymous positions and 10 that were nonsynonymous. Several statistical
methods, including those that test for within-species variation as well as
those that examine variation within and among species, failed to reject the
null hypothesis that variation (both within and between species of Geomys)
at the Adh locus is consistent with the neutral theory. However, there was
significant heterogeneity in the ratio of polymorphism to divergence across
the gene, with polymorphisms clustered in the first half of the coding
region and fixed differences clustered in the second half of the gene. Two
alternative hypotheses are discussed as possible explanations for this
heterogeneity: an old balanced polymorphism in the first half of the gene
or a recent selective sweep in the second half of the gene.
相似文献
48.
Evidence for contractile protein translocation in macrophage spreading, phagocytosis, and phagolysosome formation 总被引:5,自引:4,他引:1
下载免费PDF全文
![点击此处可从《The Journal of cell biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Macrophage pseudopodia that surround objects during phagocytosis contain a meshwork of actin filaments and exclude organelles. Between these pseudopodia at the base of developing phagosomes, the organelle exclusion ceases, and lysosomes enter the cell periphery to fuse with the phagosomes. Macrophages also extend hyaline pseudopodia on the surface of nylon wool fibers and secrete lysosomal enzymes into the extracellular medium instead of into phagosomes. To analyze biochemically these concurrent alterations in cytoplasmic architecture, we allowed rabbit lung macrophages to spread on nylon wool fibers and then subjected the adherent cells to shear. This procedure caused the selective release of β-glucoronidase into the extracellular medium and yielded two fractions, cell bodies and isolated pseudopod blebs resembling podosomes, which are plasma-lemma-bounded sacs of cortical cytoplasm. Cytoplasmic extracts of the cell bodies eluted from nylon fibers contained two-thirds less actin-binding protein and myosin, and approximately 20 percent less actin and two-thirds of the other two proteins were accounted for in podosomes. The alterations in protein composition correlated with assays of myosin-associated EDTA-activated adenosine triphosphatase activity, and with a diminution in the capacity of extracts of nylon wool fiber-treated cell bodies to gel, a property dependent on the interaction between actin-binding protein and F-actin. However, the capacity of the remaining actin in cell bodies to polymerize did not change. We propose that actin-binding protein and myosin are concentrated in the cell cortex and particularly in pseudopodia where prominent gelation and syneresis of actin occur. Actin in the regions from which actin-binding protein and myosin are displaced disaggregates without depolymerizing, permitting lysosomes to gain access to the plasmalemma. Translocation of contractile proteins could therefore account for the concomitant differences in organelle exclusion that characterize phagocytosis. 相似文献
49.
Ruis MA de Groot J te Brake JH Dinand Ekkel E van de Burgwal JA Erkens JH Engel B Buist WG Blokhuis HJ Koolhaas JM 《Applied animal behaviour science》2001,70(3):201-225
Endocrine, behavioural and immunologic processes, together with body growth, were evaluated in gilts that were defeated at 10 weeks of age in resident-intruder tests. Immediately after defeat, gilts were either separated from or reunited with a familiar conspecific (litter-mate; always a barrow). Gilts were assigned to one of four treatments: (a) DI: defeat, followed by isolation (separation from original litter-mate; n=8); (b) I: no defeat, isolation (control group; n=9); (c) DP; defeat, followed by pair-housing (reunion with original litter-mate; n=8); and (d) P: no defeat, pair-housing (control group; n=8). The following general conclusions were derived: (1) social defeat caused pronounced short-term elevations in hypothalamic-pituitary-adrenal (HPA) and sympathetic-adrenal medullary activities, and of prolactin levels. Moreover, as soon as 1h after defeat, percentages of blood lymphocytes and neutrophilic granulocytes were, respectively, decreased and increased; (2) social defeat had some long-lasting influence on behaviour and physiology, but isolation predominantly determined responses in the longer term. Defeat, as well as isolation, resulted in increased cardiovascular activities compared to P controls, as observed in a novel object test (NOT: +7 days) and an aversion test (AVT: +14 days). Moreover, defeated as well as isolated gilts did not habituate to a repeated novel environment test (NET: -7, +2 and +7 days) in terms of frequencies of vocalising, whereas P controls did. Isolation, through the separation from any other pig, was responsible for the other observed long-term characteristics, which developed progressively. Isolated gilts showed high mobilities and high cortisol responses in the repeated NET (+7 days), not being habituated. This contrasted the reactions of pair-housed gilts, which were much reduced. In addition to their high cardiovascular activities in the NOT and the AVT, isolated gilts also displayed higher heart rates in the repeated NET and during human presence following the NOT, compared to pair-housed gilts. Finally, isolated gilts were more inhibited to approach a novel object (in the NOT) than pair-housed pigs; and (3) stress responses of defeated gilts were modulated by the subsequent social environment. Stimulation of the HPA-axis (plasma- and salivary cortisol) was prolonged in those defeated gilts which were isolated (observed in the first hour). Changes in leucocyte subsets were still observed after 3 days in DI, but were 'normalised' within 1 day in DP gilts. Two days after defeat, habituation to the repeated NET in terms of mobility and salivary cortisol responses occurred in control and DP gilts, but not in DI gilts. We argue that these effects of the social environment shortly after defeat were related to a stress-reducing effect of a stable social relationship, i.e. social support. 相似文献
50.