全文获取类型
收费全文 | 234篇 |
免费 | 14篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 4篇 |
2021年 | 8篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 12篇 |
2016年 | 11篇 |
2015年 | 12篇 |
2014年 | 10篇 |
2013年 | 22篇 |
2012年 | 20篇 |
2011年 | 18篇 |
2010年 | 6篇 |
2009年 | 13篇 |
2008年 | 15篇 |
2007年 | 14篇 |
2006年 | 13篇 |
2005年 | 9篇 |
2004年 | 6篇 |
2003年 | 8篇 |
2002年 | 9篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1985年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有248条查询结果,搜索用时 46 毫秒
11.
Hacer Tugba Degirmencioglu Etil Guzelmeric Parla Isil Yuksel Hasan Krmzbekmez Inci Deniz Erdem Yesilada 《化学与生物多样性》2019,16(12)
This study was undertaken to analyze the phenolic profiles of 19 propolis samples from Turkey by using a high‐performance thin‐layer chromatographic (HPTLC) method in order to identify their plant origins. Furthermore, their antioxidant and antimicrobial activity profiles were comparatively evaluated. For the appraisal of antioxidant potential, total phenolic (TPC) and total flavonoid contents (TFC) of propolis samples were firstly determined and then their effects on free radicals were evaluated by FRAP, ABTS.+, CUPRAC, DPPH. and HPTLC‐DPPH. methods. Antimicrobial activity of propolis samples against Staphylococcus aureus (ATCC 6538), Pseudomonas aeruginosa (ATCC 15442), Escherichia coli (ATCC 11229) and Candida albicans ATCC 10231 were determined by disc diffusion and broth dilution methods. HPTLC fingerprinting analyses revealed that O‐type (botanical origin from Populus nigra L.) was the primarily available propolis type in Turkey. Moreover, 3‐O‐methylquercetin (3MQ) rich propolis was identified as a new propolis type for the first time. Principal component analysis (PCA) indicated that 3MQ‐type propolis differs from the O‐type. Antioxidant activity studies showed that O‐type of propolis possesses higher antioxidant effect than the other tested propolis types. Quercetin, caffeic acid, caffeic acid phenethyl ester (CAPE) and galangin were determined to contribute significantly to the antioxidant potential of O‐type propolis among others. Propolis extracts exerted moderate antimicrobial activity against the tested microorganisms with MIC values between the ranges of 128–512 μg/mL. 相似文献
12.
Hacer Esen Saadet Alpdağtaş Mehmet Mervan Çakar 《Preparative biochemistry & biotechnology》2019,49(5):529-534
AbstractSeveral protein expression systems can be used to get enzymes in required quantities and study their functions. Incorporating a polyhistidine tag is a beneficial way of getting various enzymes such as FDHs for industrial applications. The NAD+ dependent formate dehydrogenase from Chaetomium thermophilum (CtFDH) can be utilized for interconversion of formate to carbon dioxide coupled with the conversion of NAD+ to NADH. In this study, N-terminal His tagged CtFDH (N-CtFDH) and C-terminal His tagged CtFDH (C-CtFDH) was constructed to learn the effect of His tag location on the activity and kinetic parameters of the enzyme. The solubility of proteins was not affected by tag position, however, an interference on the N-terminal region caused a deterioration in specific activity and the kinetic ability of enzyme. The obtained results indicated that the C-terminus of the enzyme is an appropriate region for tag engineering. The C-CtFDH has an approximately three-fold larger specific activity and two-fold higher catalytic efficiency than N-CtFDH. The results suggest that insertion of a His-tag at the N-terminal or C-terminal end of CtFDH has different effects on the protein and the N-terminal fragment of the protein is crucial for the function of CtFDH. 相似文献
13.
Küpeli E Aslan M Gürbüz I Yesilada E 《Zeitschrift für Naturforschung. C, Journal of biosciences》2004,59(11-12):787-790
Anti-nociceptive, anti-inflammatory and gastroprotective activities of the known C-glycosyl flavonoid, isoorientin, were studied in rats and mice. For the anti-nociceptive activity assessment the p-benzoquinone-induced writing test, for the anti-inflammatory activity the carrageenan-induced hind paw edema model in mice, and for the gastroprotective activity the EtOH-induced ulcerogenesis model in rats were used. Isoorientin was shown to possess significant anti-nociceptive and anti-inflammatory activities at 15 mg/kg and 30 mg/kg doses, without inducing any apparent acute toxicity as well as gastric damage. However, the compound did not possess any significant gastroprotective activity against EtOH-induced ulcerogenesis. 相似文献
14.
B7-1 costimulatory molecule is critical for the development of experimental autoimmune myasthenia gravis 总被引:4,自引:0,他引:4
Poussin MA Tüzün E Goluszko E Scott BG Yang H Franco JU Christadoss P 《Journal of immunology (Baltimore, Md. : 1950)》2003,170(8):4389-4396
Following immunization with acetylcholine receptor (AChR), MHC class II-restricted, AChR-specific CD4 cell activation is critical for the development of experimental autoimmune myasthenia gravis (EAMG) in C57BL/6 mice. To study the contributions of B7-1 and B7-2 costimulatory molecules in EAMG, B7-1, B7-2, and B7-1/B7-2 gene knockout (KO) mice were immunized with Torpedo AChR in CFA. Compared with wild-type C57BL6 mice, B7-1 and B7-1/2 KO mice were resistant to EAMG development. B7-1 KO mice had reduced anti-AChR Ab compared with C57BL/6 mice. However, neither B7-1 nor B7-2 gene disruption impaired AChR-induced or dominant alpha(146-162) peptide-induced in vitro lymphoproliferative responses. Blocking of the B7-1 or B7-2 molecule by specific mAbs in vivo led to a reduction in the AChR-specific lymphocyte response, and the reduction was more pronounced in mice treated with anti-B7-2 Ab. The findings implicate B7-1 molecules as having a critical role in the induction of EAMG, and the resistance of B7-1 KO mice is associated with suppressed humoral, rather than suppressed AChR-specific, T cell responses. The data also point to B7-2 molecules as being the dominant costimulatory molecules required for AChR-induced lymphocyte proliferation. 相似文献
15.
Genetic evidence for involvement of classical complement pathway in induction of experimental autoimmune myasthenia gravis 总被引:16,自引:0,他引:16
Tüzün E Scott BG Goluszko E Higgs S Christadoss P 《Journal of immunology (Baltimore, Md. : 1950)》2003,171(7):3847-3854
Abs to acetylcholine receptor (AChR) and complement are the major constituents of pathogenic events causing neuromuscular junction destruction in both myasthenia gravis (MG) and experimental autoimmune MG (EAMG). To analyze the differential roles of the classical vs alternative complement pathways in EAMG induction, we immunized C3(-/-), C4(-/-), C3(+/-), and C4(+/-) mice and their control littermates (C3(+/+) and C4(+/+) mice) with AChR in CFA. C3(-/-) and C4(-/-) mice were resistant to disease, whereas mice heterozygous for C3 or C4 displayed intermediate susceptibility. Although C3(-/-) and C4(-/-) mice had anti-AChR Abs in their sera, anti-AChR IgG production by C3(-/-) mice was significantly suppressed. Both C3(-/-) and C4(-/-) mice had reduced levels of B cells and increased expression of apoptotis inducers (Fas ligand, CD69) and apoptotic cells in lymph nodes. Immunofluorescence studies showed that the neuromuscular junction of C3(-/-) and C4(-/-) mice lacked C3 or membrane attack complex deposits, despite having IgG deposits, thus providing in vivo evidence for the incapacity of anti-AChR IgGs to induce full-blown EAMG without the aid of complements. The data provide the first direct genetic evidence for the classical complement pathway in the induction of EAMG induced by AChR immunization. Accordingly, severe MG and other Ab- and complement-mediated diseases could be effectively treated by inhibiting C4, thus leaving the alternative complement pathway intact. 相似文献
16.
Tezel E Guerrerosantos J Trabanino C 《Plastic and reconstructive surgery》2002,110(6):1603-4; author reply 1604
17.
A laboratory experiment was performed for an incubation period of 120 days in order to evaluate the changes in chemical properties of an acid soil amended with 0, 15, 30, 60 and 120 t ha-' of brewery sludge (BS). Increasing BS rates and incubation time reduced pH of the soil by 0.3-0.5 unit with respect to the control while soluble salts increased from 0.11 to 0.80 dS m(-1). Organic C, exchangeable cations, soluble cations and anions, NH4+-N and NO3--N contents of the amended soil increased as BS rates increased. In addition, BS application caused a slight increase in cation exchange capacity (CEC) and a slight decrease in exchangeable acidity. 相似文献
18.
NADPH-diaphorase-containing neurons (it is supposed that this enzyme is a form of NO-synthase, NOS) were histochemically identified
in the spinal cord of rats. In another set of the experiments, we identified neurons -sources of spinothalamic and spinomesencephalic
pathways - by their retrograde labelling with Fluoro-Gold (FG) injected into the thalamus and periaqueductal gray substance.
It was shown that NOS-containing spinal cells are, as a rule, propriospinal intersegmental or intrasegmental interneurons.
We discuss the possible involvement of these cells in the “inhibition-of-inhibition” processes and in potentiation of the
synaptic transmission in spinal neurons under conditions of the development of tonic or chronic pain. In rats, the number
of NOS-containing neurons, which are also retrogradely labelled with FG after dye injection into the thalamus and midbrain,
Is rather limited. 相似文献
19.
Angela J. Gruber Aysen L. Erdem Grzegorz Sabat Kiyonobu Karata Malgorzata M. Jaszczur Dan D. Vo Tayla M. Olsen Roger Woodgate Myron F. Goodman Michael M. Cox 《PLoS genetics》2015,11(3)
DNA polymerase V (pol V) of Escherichia coli is a translesion DNA polymerase responsible for most of the mutagenesis observed during the SOS response. Pol V is activated by transfer of a RecA subunit from the 3''-proximal end of a RecA nucleoprotein filament to form a functional complex called DNA polymerase V Mutasome (pol V Mut). We identify a RecA surface, defined by residues 112-117, that either directly interacts with or is in very close proximity to amino acid residues on two distinct surfaces of the UmuC subunit of pol V. One of these surfaces is uniquely prominent in the active pol V Mut. Several conformational states are populated in the inactive and active complexes of RecA with pol V. The RecA D112R and RecA D112R N113R double mutant proteins exhibit successively reduced capacity for pol V activation. The double mutant RecA is specifically defective in the ATP binding step of the activation pathway. Unlike the classic non-mutable RecA S117F (recA1730), the RecA D112R N113R variant exhibits no defect in filament formation on DNA and promotes all other RecA activities efficiently. An important pol V activation surface of RecA protein is thus centered in a region encompassing amino acid residues 112, 113, and 117, a surface exposed at the 3''-proximal end of a RecA filament. The same RecA surface is not utilized in the RecA activation of the homologous and highly mutagenic RumA''2B polymerase encoded by the integrating-conjugative element (ICE) R391, indicating a lack of structural conservation between the two systems. The RecA D112R N113R protein represents a new separation of function mutant, proficient in all RecA functions except SOS mutagenesis. 相似文献
20.
S. Rasoul V. van Ommen J. Vainer M. Ilhan L. Veenstra R. Erdem L.A.W. Ruiters R. Theunissen J.C.A. Hoorntje 《Netherlands heart journal》2015,23(4):224-231