首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   237篇
  免费   11篇
  2023年   1篇
  2022年   1篇
  2021年   3篇
  2020年   2篇
  2019年   2篇
  2018年   2篇
  2016年   4篇
  2015年   2篇
  2014年   6篇
  2013年   5篇
  2012年   11篇
  2011年   6篇
  2010年   3篇
  2009年   10篇
  2008年   14篇
  2007年   18篇
  2006年   15篇
  2005年   19篇
  2004年   16篇
  2003年   14篇
  2002年   10篇
  2001年   8篇
  2000年   9篇
  1999年   11篇
  1998年   6篇
  1997年   3篇
  1996年   4篇
  1995年   3篇
  1994年   4篇
  1993年   2篇
  1992年   6篇
  1991年   3篇
  1990年   1篇
  1989年   1篇
  1988年   4篇
  1987年   2篇
  1986年   2篇
  1985年   2篇
  1984年   1篇
  1983年   4篇
  1982年   5篇
  1981年   1篇
  1975年   2篇
排序方式: 共有248条查询结果,搜索用时 15 毫秒
1.
We describe a patient with adult T cell Leukemia to whom alpha-interferon therapy was highly effective. Although a combination chemotherapy (ACVP) first introduced was effective in reducing total leukocyte counts, the percentage of leukemic cells relative to total leukocyte counts was decreased first after the institution of alpha-interferon therapy. The patient is now under complete remission for four years. It was noted in this patient that circulating alpha-interferon, measured by a sensitive radioimmunoassay, was consistently low as compared with the value found in the age-, sex-matched healthy control (p less than 0.001). Since adult T cell leukemia is pathogenetically related to the retrovirus infection, low levels of circulating alpha-interferon of the patient may be important from both pathogenetic and therapeutic standpoints. Alpha-interferon therapy may be an useful additive for the chemotherapy of adult T cell leukemia.  相似文献   
2.
Summary In a cooperative randomized control study of immunotherapy with bestatin in combination with chemotherapy in adults with acute nonlymphocytic leukemia (ANLL), 101 patients (48 in the bestatin group and 53 in the control group) out of 115 patients registered were evaluated as eligible. The bestatin group achieved a statistically significant prolongation of survival compared with the control group in overall ANLL and acute myelogenous leukemia. In the analysis of patient age, the bestatin group achieved a statistically significant prolongation of both the remission duration and survival in patients aged 50 to 65 years, while the differences were not significant in the 15 to 49 age group. The bestatin group tended to achieve a higher rate of reinduction of remission in patients who had recurrence of leukemia. Side effects developed in only 5 (9.6%) of 52 patients treated with bestatin. None of these side effects were particularly serious in nature. It is concluded that bestatin is useful for prolongation of survival of adult patients with ANLL, making for a longer remission duration especially in elderly patients and with few side effects.  相似文献   
3.
Abstract: The effects of various protein kinase inhibitors on acetylcholine release from the rat hippocampus induced by the local application of NS-3 (montirelin hydrate, CG-3703), a thyrotropin-releasing hormone analogue, into the medial septum-diagonal band were examined using in vivo microdialysis. Perfusion of NS-3 (1 µ M ) into the medial septum-diagonal band for 20 min produced a pronounced and prolonged increase in the hippocampal acetylcholine efflux. Pretreatment of the medial septum-diagonal band with either K-252a, a nonselective protein kinase inhibitor, or selective protein kinase A inhibitor H-89 almost completely blocked the acetylcholine efflux evoked by NS-3, and selective protein kinase C inhibitor calphostin C inhibited the action of NS-3. On the other hand, NS-3 (0.1–10 µ M ) or TRH (1–100 µ M ) increased the cyclic AMP efflux from the medial septum-diagonal band in a concentration-dependent manner, as measured by microdialysis. These findings suggest that protein kinases A and C in the neurons of the medial septum-diagonal band are involved in the mechanism of the prolonged stimulation of acetylcholine release from the hippocampus induced by thyrotropin-releasing hormone and its analogue, NS-3.  相似文献   
4.
Under the influence of maturation-inducing hormone (MIH) secreted from follicle cells, oocyte maturation is finally triggered by maturation-promoting factor (MPF), which consists of a homolog of the cdc2+ gene product of fission yeast (p34cdc2) and cyclin B. Two species of cyclin B clones were isolated from a cDNA library constructed from mature goldfish oocytes. Sequence comparisons revealed that these two clones are highly homologous (95%) and were found to be similar to Xenopus cyclin B1. Using monoclonal antibodies against Escherichia coli-produced goldfish cyclin B and the PSTAIR sequence of p34cdc2, we examined the levels of cyclin B and p34cdc2 proteins during goldfish oocyte maturation induced in vitro by 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (17 alpha, 20 beta-DP), a natural MIH in fish. Protein p34cdc2 was found in immature oocyte extracts and did not remarkably change during oocyte maturation. Cyclin B was not detected in immature oocyte extracts and appeared when oocytes underwent germinal vesicle breakdown. Cyclin B that appeared during oocyte maturation was labelled with [35S]methionine, indicating its de novo synthesis. Introduction of E. coli-produced cyclin B into immature oocyte extracts induced p34cdc2 (MPF) activation. Although the possibility that immature goldfish oocytes contain an insoluble cyclin B is not completely excluded, these results strongly suggest that 17 alpha, 20 beta-DP induces oocytes to synthesize cyclin B, which in turn activates preexisting p34cdc2, forming active MPF.  相似文献   
5.
Maturation-promoting factor and a homolog of fission yeast cdc2+ gene product (p34cdc2) were investigated during the final 24 hr of maturation of quail oocytes. Kinase activity of p34cdc2 in the oocyte germinal disk (GD) increased 15 times at maturation. Two bands, at 32 and 34 kDa, were detected in immature oocytes by immunoblotting of SDS-PAGE with anti-p34cdc2 monoclonal antibody. A new band, which is close to the 32-kDa band but with a slightly faster mobility, appeared during maturation. No p34cdc2 could be detected outside the GD. Microinjection of GD extract from mature oocytes caused maturation of Xenopus oocytes.  相似文献   
6.
BL191, a newly developed phosphodiesterase inhibitor, markedly potentiated a differentiation of neuroblastoma cell clones (Neuro2a, NS-20Y, and N1E115) induced by dibutyryl cyclic adensoine 3′:5′-monophosphate(dibutyryl cAMP) and prostaglandin E1 (PGE1). BL191 (1 mM) inhibited DNA synthesis more strongly when used together with PGE1 (0.5 μg/ml) and dibutyryl cAMP (0.5 mM) than papaverine (1.6 μg/ml) alone did. The inhibition rates of DNA synthesis were 72.5% for N1E-115, 75.3% for Neuro2a, and 82.5% for NS-20Y. After the treatment with BL191. PGE1, and dibutyryl cAMP for 48 h all of three cell lines became enlarged and flattened, and extended long processes. The specific activities of choline acetyl transferase (EC 2.3.1.9) of NS-20Y and dopamine β-hydroxylase (EC 1.14.17.1) of N1E-115 increased about 3-fold as compared to the controls. The tumorigenicities of Neuro2a and N1E-115 cells were decreased, but not of NS-20Y. These data suggest the heterogenous responsiveness in neuroblastoma cells to drug treatment.  相似文献   
7.
The blend miscibility of cellulose propionate (CP) with poly(N-vinyl pyrrolidone-co-methyl methacrylate) (P(VP-co-MMA)) was investigated. The degree of substitution (DS) of CP used ranged from 1.6 to >2.9, and samples for the vinyl polymer component were prepared in a full range of VP:MMA compositions. Through DSC analysis and solid-state 13C NMR and FT-IR measurements, we revealed that CPs of DS < 2.7 were miscible with P(VP-co-MMA)s of VP ≥ ∼10 mol% on a scale within a few nanometers, in virtue of hydrogen-bonding interactions between CP-hydroxyls and VP-carbonyls. When the DS of CP exceeded 2.7, the miscibility was restricted to the polymer pairs using P(VP-co-MMA)s of VP = ca. 10–40 mol%; the scale of mixing in the blends concerned was somewhat larger (ca. 5–20 nm), however. The appearance of such a “miscibility window” was interpretable as an effect of intramolecular repulsion in the copolymer component. Results of DMA and birefringence measurements indicated that the miscible blending of CP with the vinyl polymer invited synergistic improvements in thermomechanical and optical properties of the respective constituent polymers. Additionally, it was found that the VP:MMA composition range corresponding to the miscibility window was expanded by modification of the CP component into cellulose acetate propionate.  相似文献   
8.
The chromosomes of Japanese flounder, Paralichthys olivaceus, were examined by conventional differential staining methods including G-, Q-, C-, silver (Ag)-, fluorochrome, and replication R-bandings and by fluorescence in situ hybridization (FISH) with 5S and 18S rDNAs and telomeric DNA as probes. Replication R-banding substantially made it possible to identify 24 homologous pairs by their RBG-banding pattern and relative length. Both rDNA loci were mapped to chromosome 1, where 5S and 18S rDNA loci were located at the centromeric region and secondary constriction, respectively. C-banding revealed that both rDNA loci were heterochromatic, and 18S rDNA loci were positive for chromomycin A3 but negative for 4′,6-diamidino-2-phenylindole (DAPI) staining. Telomeric FISH signals were observed at all chromosome ends and at the interstitial region of some chromosomes. The observed results were discussed in relation to the karyotype evolution in the order Pleuronectiformes.  相似文献   
9.
The potential of quantitative proteomic analysis to predict carcinogenicity of chemical compounds was investigated. Using 2D-DIGE, we analyzed the effects of 63 chemical compounds on protein expression in the rat liver after 28 daily doses. Types of carcinogens were categorized depending on the species and organ specificity. The carcinogen characteristic proteins for each classification were identified by Welch's t value. For evaluation of the predictive concordance we used support vector machines. The rat hepatic carcinogen-specific classification gave higher concordance than the other classification. The generalization performance was measured by leave-one-out cross-validation. For genotoxic and non-genotoxic compounds, a concordance of 79.3 and 76.5%, respectively, was obtained by the top 30 ranked proteins with Welch's t value. Furthermore, we found that the increase of the expression level of the stress response proteins as the common feature of poorly predicted chemical compounds in the leave-20%-out cross-validation. Quantitative proteomics could be promising technique for developing biomarker panels that can be used for carcinogenicity prediction. The list of proteins identified in this study and the zoomed gel images of the top ranked proteins in statistic analysis are provided in Supplementary Data.  相似文献   
10.
5-Formyluracil (fU) is a major oxidative thymine lesion generated by ionizing radiation and reactive oxygen species. In the present study, we have assessed the influence of fU on DNA replication to elucidate its genotoxic potential. Oligonucleotide templates containing fU at defined sites were replicated in vitro by Escherichia coli DNA polymerase I Klenow fragment deficient in 3'-5'-exonuclease. Gel electrophoretic analysis of the reaction products showed that fU constituted very weak replication blocks to DNA synthesis, suggesting a weak to negligible cytotoxic effect of this lesion. However, primer extension assays with a single dNTP revealed that fU directed incorporation of not only correct dAMP but also incorrect dGMP, although much less efficiently. No incorporation of dCMP and dTMP was observed. When fU was substituted for T in templates, the incorporation efficiency of dAMP (f(A) = V(max)/K(m)) decreased to (1/4) to (1/2), depending on the nearest neighbor base pair, and that of dGMP (f(G)) increased 1.1-5.6-fold. Thus, the increase in the replication error frequency (f(G)/f(A) for fU versus T) was 3.1-14.3-fold. The misincorporation rate of dGMP opposite fU (pK(a) = 8.6) but not T (pK(a) = 10.0) increased with pH (7.2-8.6) of the reaction mixture, indicating the participation of the ionized (or enolate) form of fU in the mispairing with G. The resulting mismatched fU:G primer terminus was more efficiently extended than the T:G terminus (8.2-11.3-fold). These results show that when T is oxidized to fU in DNA, fU promotes both misincorporation of dGMP at this site and subsequent elongation of the mismatched primer, hence potentially mutagenic.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号