全文获取类型
收费全文 | 307篇 |
免费 | 25篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 7篇 |
2020年 | 9篇 |
2019年 | 9篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 15篇 |
2015年 | 17篇 |
2014年 | 23篇 |
2013年 | 21篇 |
2012年 | 20篇 |
2011年 | 21篇 |
2010年 | 8篇 |
2009年 | 13篇 |
2008年 | 14篇 |
2007年 | 11篇 |
2006年 | 17篇 |
2005年 | 10篇 |
2004年 | 18篇 |
2003年 | 17篇 |
2002年 | 12篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1995年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有332条查询结果,搜索用时 15 毫秒
121.
In this study we propose a novel bacterial vaccine strategy where non-pathogenic bacteria are complemented with traits desirable for the induction of protective immunity. To illustrate the proof of principle of this novel vaccination strategy, we use the model organism of intracellular immunity Listeria. We introduced a, low copy number BAC-plasmid harbouring the virulence gene cluster (vgc) of L. monocytogenes (Lm) into the non-pathogenic L. innocua (L.inn) strain and examined for its ability to induce protective cellular immunity. The resulting strain (L.inn::vgc) was attenuated for virulence in vivo and showed a strongly reduced host detrimental inflammatory response compared to Lm. Like Lm, L.inn::vgc induced the production of Type I Interferon's and protection was mediated by Listeria-specific CD8(+) T cells. Rational vaccine design whereby avirulent strains are equipped with the capabilities to induce protection but lack detrimental inflammatory effects offer great promise towards future studies using non-pathogenic bacteria as vectors for vaccination. 相似文献
122.
Hu M Ayub Q Guerra-Assunção JA Long Q Ning Z Huang N Romero IG Mamanova L Akan P Liu X Coffey AJ Turner DJ Swerdlow H Burton J Quail MA Conrad DF Enright AJ Tyler-Smith C Xue Y 《Human genetics》2012,131(5):665-674
We have investigated whether regions of the genome showing signs of positive selection in scans based on haplotype structure
also show evidence of positive selection when sequence-based tests are applied, whether the target of selection can be localized
more precisely, and whether such extra evidence can lead to increased biological insights. We used two tools: simulations
under neutrality or selection, and experimental investigation of two regions identified by the HapMap2 project as putatively
selected in human populations. Simulations suggested that neutral and selected regions should be readily distinguished and
that it should be possible to localize the selected variant to within 40 kb at least half of the time. Re-sequencing of two
~300 kb regions (chr4:158Mb and chr10:22Mb) lacking known targets of selection in HapMap CHB individuals provided strong evidence
for positive selection within each and suggested the micro-RNA gene hsa-miR-548c as the best candidate target in one region,
and changes in regulation of the sperm protein gene SPAG6 in the other. 相似文献
123.
In this work is described the isolation of a new proteases-producing strain of Bacillus subtilis, screened from aerobic tannery sludge, to be applied in leather production. The optimization of culture conditions to enhance the proteolytic activity was carried out using central composite design. The enzymatic extract was characterized and the hide unhairing and the inter-fibrillary removal capabilities of the enzymatic extract were evaluated by scanning electron microscopy and by the determination of proteoglycans and glycosaminoglycans. The leather quality obtained with this enzymatic preparation was assessed for possible damages to hide collagen by measuring the amount of hydroxyproline released into the reaction medium. Temperature was the most significant factor for culture conditions optimization. The crude enzymatic extract showed the best values for proteolytic activities at pH 9 and 10, temperature between 37 and 55?°C, and showed good thermal stability up to 45?°C. The treated hides presented few remaining hairs; for the enzymatic process, the removal of inter-fibrillary proteins was approximately fourfold for glycosaminoglycans and sixfold for proteoglycans, when compared with the conventional unhairing process. The enzyme application was successful for hide treatment, suggesting that this enzymatic preparation can be used in an environment-friendly leather production to replace the conventional chemical process. 相似文献
124.
Balamurugan A Lewis MJ Kitchen CM Robertson MN Shiver JW Daar ES Pitt J Ali A Ng HL Currier JS Yang OO 《Journal of virology》2008,82(6):2784-2791
Vaccination for human immunodeficiency virus type 1 (HIV-1) remains an elusive goal. Whether an unsuccessful vaccine might not only fail to provoke detectable immune responses but also could actually interfere with subsequent natural immunity upon HIV-1 infection is unknown. We performed detailed assessment of an HIV-1 gag DNA vaccine recipient (subject 00015) who was previously uninfected but sustained HIV-1 infection before completing a vaccination trial and another contemporaneously acutely infected individual (subject 00016) with the same strain of HIV-1. Subject 00015 received the vaccine at weeks 0, 4, and 8 and was found to have been acutely HIV-1 infected around the time of the third vaccination. Subject 00016 was a previously HIV-1-seronegative sexual contact who had symptoms of acute HIV-1 infection approximately 2 weeks earlier than subject 00015 and demonstrated subsequent seroconversion. Both individuals reached an unusually low level of chronic viremia (<1,000 copies/ml) without treatment. Subject 00015 had no detectable HIV-1-specific cytotoxic T-lymphocyte (CTL) responses until a borderline response was noted at the time of the third vaccination. The magnitude and breadth of Gag-specific CTL responses in subject 00015 were similar to those of subject 00016 during early chronic infection. Viral sequences from gag, pol, and nef confirmed the common source of HIV-1 between these individuals. The diversity and divergence of sequences in subjects 00015 and 00016 were similar, indicating similar immune pressure on these proteins (including Gag). As a whole, the data suggested that while the gag DNA vaccine did not prime detectable early CTL responses in subject 00015, vaccination did not appreciably impair his ability to contain viremia at levels similar to those in subject 00016. 相似文献
125.
GA3 can be beneficial to improve the flowering yield in Lagenaria siceraria (Mol.) Standl. and Luffa cylindrica L. (Roem) treated with HgCl2 and . This paper reviews the literature on the possible involvement of gibberellins in flower development and suggests that plants under the stress of heavy metals can be treated with GA3 to improve growth parameters, to avoid delay in flowering and likewise quality of fruit can be improved. Applied GA3 (400 mg/l) caused precocious flowering, increasing the number of flowers in the treated plants. All data was compared with control plants grown under similar conditions. Both heavy metals caused significant delay in flowering, consequently leading to reduction in the number of flowers. However, when GA3 was applied with HgCl2 and , there was less decrease in staminate and pistillate flowers, revealing the dominant effect of GA3. Current work reveals that inhibitory effects of heavy metals on flowering can be partially restored with GA3 application. 相似文献
126.
Bruna da Silva Menezes Daniele Misturini Rossi Marco Antônio Záchia Ayub 《World journal of microbiology & biotechnology》2017,33(3):58
We investigated the enzymatic complex produced by selected fungi strains isolated from the environment using the agro-industrial residues rice husk, soybean hull, and spent malt as substrates. Microbial growth was carried out in solid-state cultivation (SSC) and in submerged cultivations (SC) and the enzymatic activities of xylanase, cellulase, β-xylosidase, and β-glucosidase were determined. All substrates were effective in inducing enzymatic activities, with one strain of Aspergillus brasiliensis BLf1 showing maximum activities for all enzymes, except for cellulases. Using this fungus, the enzymatic activities of xylanase, cellulase, and β-glucosidase were generally higher in SSC compared to SC, producing maxima activities of 120.5, 25.3 and 47.4 U g?1 of dry substrate, respectively. β-xylosidase activity of 28.1 U g?1 of dry substrate was highest in SC. Experimental design was carried out to optimize xylanase activity by A. brasiliensis BLf1 in SSC using rice husk as substrate, producing maximum xylanase activity 183.5 U g?1 dry substrate, and xylooligosaccharides were produced and characterized. These results suggest A. brasiliensis BLf1 can be used to produce important lytic enzymes to be applied in the preparation of xylooligosaccharides. 相似文献
127.
Erik Rokkones Sigurd H. Fromm B. Najma Kareem Helge Klungland Ole K. Olstad Anders Hgset Jan Iversen Kristian Bjro Kaare M. Gautvik 《Journal of cellular biochemistry》1995,59(2):168-176
In a transgenic mouse model we have targeted the expression of recombinant human parathyroid hormone (hPTH) to the mammary gland yielding hPTH as a secretory, soluble peptide in milk. A 2.5 kb upstream regulatory sequence of the murine whey acidic protein (WAP) directed the expression of the hPTH cDNA in a fusion gene construct (WAPPTHSV2) containing the SV40 small t-antigen intron and polyadenylation site in the 3′ end. Established lines of transgenic mice secreted hPTH to milk in concentrations up to 415 ng/ml. Recombinant hPTH recovered from the milk was purified by HPLC and shown to be identical to hPTH standard as analyzed by SDS-PAGE followed by immunoblotting. Expression of the WAPPTHSV2 was limited to the mammary gland as analyzed by polymerase chain reaction (PCR) and Southern blot of reversed transcribed mRNA from different tissues. hPTH is an important bone anabolic hormone and may be a potentially important pharmaceutical for treatment of demineralization disorders such as osteoporosis. We present the transgenic animal as a possible production system for hPTH. © 1995 Wiley-Liss, Inc. 相似文献
128.
Internalin B is essential for adhesion and mediates the invasion of Listeria monocytogenes into human endothelial cells 总被引:8,自引:2,他引:6
Shreemanta K. Parida Eugen Domann Manfred Rohde Simone Müller Ayub Darji Torsten Hain Jürgen Wehland & Trinad Chakraborty 《Molecular microbiology》1998,28(1):81-93
Listeria monocytogenes causes rhombencephalitis in humans and animals and also affects the fetus in utero , causing disseminated sepsis. In both instances, the infection occurs by the crossing of endothelial cells lining a physiological barrier, the blood–brain barrier or the transplacental barrier. In this study, the ability of L. monocytogenes wild-type EGD to invade human umbilical vein endothelial cells (HUVECs) was evaluated using wild-type bacteria and isogenic Listeria mutants. Here, we show that invasion of HUVECs by L. monocytogenes is dependent on the expression of the internalin B gene product. This was demonstrated in several ways. First, L. monocytogenes strains lacking the inl B gene did not invade HUVECs. Secondly, avid invasion was obtained when a strain deleted for inl AB was complemented with a plasmid harbouring inl B only, whereas strains expressing inl A did not enter HUVECs. Thirdly, entry of wild-type EGD could be blocked effectively with antibodies to InlB. Fourthly, cell binding assays and flow cytometry with HUVECs showed binding of purified InlB, but not InlA, suggesting a tropism of InlB for this cell type. Finally, physical association of purified native InlB with the surface of non-invasive mutants dramatically increased their ability to invade HUVECs. In laser-scanning confocal microscopy, binding of InlB was observed as focal and localized patches on the cell surface of HUVECs. Qualitative examination of the entry process by scanning electron microscopy revealed that both wild-type EGD and a recombinant strain overexpressing only InlB enter HUVECs in a similar fashion. The entry process was polarized, involved single bacteria and occurred over the entire surface of endothelial cells. 相似文献
129.
Changes in the subcellular distribution of hexokinase activity from three brain regions and heart were studied during alloxan
induced diabetes. There was an overall decrease in the particulate hexokinase with an increase in the soluble form, after
different time intervals of the onset of diabetes. Administration of insulin to the diabetic rats showed a partial counteraction
of the enzyme changes. A possible regulation of brain hexokinase by metabolite changes is proposed 相似文献
130.
Pseudomonas sp. 14-3, a strain that accumulates large quantities of polyhydroxybutyrate (PHB) when grown on octanoate, was isolated from Antarctic environments. This isolate was characterized on the basis of phenotypic features and partial sequencing of its 16S ribosomal RNA gene. Pseudomonas sp. 14-3 showed increased tolerance to both thermal and oxidative stress compared with three other Pseudomonas species. Stress tolerance of Pseudomonas sp. 14-3 was analyzed in polyhydroxyalkanoate accumulating and non-accumulating conditions, and increased levels of stress resistance were observed when PHB was produced. Pseudomonas sp. 14-3 was isolated from Antarctic regions, a habitat normally exposed to extreme conditions. An association between high PHB accumulation and high stress resistance in bacteria adapted to extreme environments is suggested. 相似文献