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排序方式: 共有149条查询结果,搜索用时 31 毫秒
91.
Ranjita Biswas Vikram Sahai Saroj Mishra Virendra Swarup Bisaria 《Biotechnology and Bioprocess Engineering》2010,15(5):800-809
The wild type filamentous fungus, Melanocarpus albomyces, produces many commercially valuable enzymes, including Xylanases and Xylan-debranching enzymes with low activity. In this
paper, we report for the first time the development of M. albomyces mutants from vegetative spores. Profuse sporulation of M. albomyces was induced on Potato Carrot Agar medium. These spores, when subjected to chemical mutation, led to the isolation of the
hyper-xylanase producing mutant, viz, M. albomyces IITD3A. Various parameters including number of spores, nitrogen source and C/N ratio of the medium were optimized for production
of xylanase by the mutant in a shake flask culture. Under controlled pH at 7.8, the mutant produced highly active xylanase
with 415 IU/mL after 36 h of growth on soluble alkaline lignocellulosic extract in a 14-L fermentor. The overall productivity
of xylanase was 8-fold higher than the wild type culture with11, 530 IU/L/h. The enzyme can be easily stored at 37°C for 50
days by addition of a small amount of the preservative — thiomersal. Also, for long term storage, a lyophilized powder form
of the enzyme can be used which retained 100% of its activity for > 50 days. When assayed at pH 7.5 and temperature 55°C,
the xylanase retained 100% of its original activity, and also at pH 9.0, it retained > 50% of its activity for 2 h, which
is promising for its application in the pulp and paper industry. 相似文献
92.
The present study was conducted to investigate the possible interaction between low doses of nicotine and pentylenetetrazole
(PTZ) in vivo and also to evaluate the influence of nicotine on the antiseizure efficacy of topiramate and sodium valproate
in the PTZ-induced seizure model in mice. Graded dose–response study with nicotine showed the CD50 value for nicotine at 6.76 mg/kg.
i.p. Subtheshold dose of nicotine (4 mg/kg, i.p.) pretreatment significantly decreased the CD50 value for PTZ from 47.86 mg/kg,
i.p. (of PTZ per se) to 31.62 mg/kg, i.p. Sodium valproate but not topiramate, significantly inhibited PTZ-induced seizures
in mice with an ED50 value of 177.83 mg/kg, i.p. Nonconvulsive dose of nicotine (1 mg/kg, i.p.) significantly antagonized
the protective efficacy of sodium valproate against PTZ-induced seizures and increased the ED50 value to 338.84 mg/kg, i.p.
PTZ-induced seizures significantly increased the mouse brain levels of MDA and reduced the level of GSH while sodium valproate
reversed such changes. Nicotine pretreatment reversed the anti-lipid peroxidative action of sodium valproate in the PTZ-induced
seizure model in mice. The study highlighted the convulsant as well as proconvulsant role of nicotine and established dose
discrimination for nicotine as a proconvulsant agent and an anti-antiseizure agent. The study bears significant clinical relevance
particularly amongst epileptic smokers who may show failure of efficacy of antiepileptic agents and present with breakthrough
seizure attacks on exposure to nicotine. 相似文献
93.
Fine needle aspiration cytology of minor salivary gland tumours of the palate This retrospective study was carried out to review aspirates from minor salivary gland tumours of the palate and to assess the problems encountered in their diagnosis, especially the cytological diagnosis of newer entities such as polymorphous low grade adenocarcinoma (PLGA). Fifty-five cases of palatal salivary gland tumours aspirated over a period of 16 years were reviewed. Histology was available in 26 cases. Pleomorphic adenoma (27 cases) was the most common benign cytodiagnosis. Eleven aspirates were malignant tumours of which eight cases were adenoid cystic carcinoma and three cases were mucoepidermoid carcinoma. Seven cases were diagnosed on fine needle aspiration as suggestive of PLGA. However histological confirmation was available in only one of these cases. Concordance between the initial and revised typings of the tumours was seen in only 28 cases (54%) in the present study. Initially 18 of the 51 tumours (35.3%) could not be typed; and after review, only three could not be typed. Three cases of oncocytoma could be diagnosed on review only. Palatal salivary gland tumours, although relatively uncommon, are difficult to diagnose cytologically. This is more so in cases of newer entities such as PLGA, as their cytological diagnosis is still not well characterized. 相似文献
94.
In three-dimensional matrices cancer cells move with a rounded, amoeboid morphology that is controlled by ROCK-dependent contraction of acto-myosin. In this study, we show that PDK1 is required for phosphorylation of myosin light chain and cell motility, both on deformable gels and in vivo. Depletion of PDK1 alters the localization of ROCK1 and reduces its ability to drive cortical acto-myosin contraction. This form of ROCK1 regulation does not require PDK1 kinase activity, but instead involves direct binding of PDK1 to ROCK1 at the plasma membrane; PDK1 competes directly with RhoE for binding to ROCK1. In the absence of PDK1, negative regulation by RhoE predominates, causing reduced acto-myosin contractility and motility. This work uncovers a novel non-catalytic role for PDK1 in regulating cortical acto-myosin and cell motility. 相似文献
95.
Cross-talk between Ras and Rho signalling pathways in transformation favours proliferation and increased motility 总被引:24,自引:0,他引:24
Transformation by oncogenic Ras requires the function of the Rho family GTPases. We find that Ras-transformed cells have elevated levels of RhoA-GTP, which functions to inhibit the expression of the cell cycle inhibitor p21/Waf1. These high levels of Rho-GTP are not a direct consequence of Ras signalling but are selected for in response to sustained ERK-MAP kinase signalling. While the elevated levels of Rho-GTP control the level of p21/Waf, they no longer regulate the formation of actin stress fibres in transformed cells. We show that the sustained ERK-MAP kinase signalling resulting from transformation by oncogenic Ras down-regulates ROCK1 and Rho-kinase, two Rho effectors required for actin stress fibre formation. The repression of Rho- dependent stress fibre formation by ERK-MAP kinase signalling contributes to the increased motility of Ras-transformed fibroblasts. Overexpression of the ROCK target LIM kinase restores actin stress fibres and inhibits the motility of Ras-transformed fibroblasts. We propose a model in which Ras and Rho signalling pathways cross-talk to promote signalling pathways favouring transformation. 相似文献
96.
Fidelity of deoxyribonucleic acid polymerases from normal and leukaemic human cells in polydeoxynucleotide replication (Short Communication) 总被引:1,自引:0,他引:1
B. I. Sahai Srivastava 《The Biochemical journal》1974,141(2):585-587
Although the relative incorporation of incorrect nucleotide (dCTP or dGTP) into poly(dA-dT).poly(dA-dT) by partially purified 3-4S DNA polymerase from normal or leukaemic human cells was four to five times higher than that by the 6-7S DNA polymerase, no significant differences in the infidelity of these polymerases between normal and leukaemic cells were noted. 相似文献
97.
From the anticancer-active CHCl3, extract of the plant Euphorbia maddeni, a polyacylated diterpene of jatrophone type, euphornin, has been isolated and its structure elucidated by physico-chemical methods. 相似文献
98.
Although unmodified poly C and unmodified ribosomal RNA showed little ( < 20%) or no inhibition of 6–7S cytoplasmic, 3–4S cytoplasmic and 3–4S chromatin-associated DNA-directed DNA polymerases and of RNase sensitive endogenous DNA polymerase and DNA-directed DNA polymerase activity associated with a particulate material (p = 1.16 ? 1.18 g/ml) from Burkitt cells the thiolated poly C and thiolated RNA were strongly inhibitory (70–97%). Moreover, the thiolated nucleic acids were more inhibitory to 6–7S enzyme than to 3–4S enzyme. Thiolation of nucleic acids thus appears to be a potentially important procedure for the development of agents which may be selective against certain polymerases. 相似文献
99.
Activation-induced cell death in T cell hybridomas is due to apoptosis. Morphologic aspects and DNA fragmentation. 总被引:5,自引:0,他引:5
Y F Shi M G Szalay L Paskar B M Sahai M Boyer B Singh D R Green 《Journal of immunology (Baltimore, Md. : 1950)》1990,144(9):3326-3333
Some T cell hybridomas, upon activation via the TCR, rapidly undergo cell death. In this paper, we demonstrate that this activation-induced cell death (AICD) is accompanied by morphologic changes seen at the electron and light microscopy levels. The most striking changes are an extensive condensation of the chromatin and formation of membrane blebs. In addition to the morphologic changes, a significant portion of genomic DNA is broken at an interval of approximately 200 bp, producing a ladder of oligonucleosome-sized fragments after gel electrophoresis. Taken together, these observations indicate that AICD proceeds via apoptosis, or programmed cell death. This is additionally supported by the observation that AICD-associated phenomena are at least partially inhibited by cycloheximide or actinomycin D. Curiously, AICD and its associated DNA fragmentation are completely inhibited by aurintricarboxylic acid, a known nuclease inhibitor. The possible relationship between AICD in vitro, and the negative selection process (wherein selection may proceed via AICD of developing, autoreactive thymocytes) is discussed. 相似文献
100.
Smurf1 regulates tumor cell plasticity and motility through degradation of RhoA leading to localized inhibition of contractility
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Rho GTPases participate in various cellular processes, including normal and tumor cell migration. It has been reported that RhoA is targeted for degradation at the leading edge of migrating cells by the E3 ubiquitin ligase Smurf1, and that this is required for the formation of protrusions. We report that Smurf1-dependent RhoA degradation in tumor cells results in the down-regulation of Rho kinase (ROCK) activity and myosin light chain 2 (MLC2) phosphorylation at the cell periphery. The localized inhibition of contractile forces is necessary for the formation of lamellipodia and for tumor cell motility in 2D tissue culture assays. In 3D invasion assays, and in in vivo tumor cell migration, the inhibition of Smurf1 induces a mesenchymal-amoeboid-like transition that is associated with a more invasive phenotype. Our results suggest that Smurf1 is a pivotal regulator of tumor cell movement through its regulation of RhoA signaling. 相似文献