全文获取类型
收费全文 | 272篇 |
免费 | 19篇 |
国内免费 | 21篇 |
出版年
2023年 | 1篇 |
2021年 | 9篇 |
2020年 | 7篇 |
2019年 | 4篇 |
2018年 | 9篇 |
2017年 | 5篇 |
2016年 | 12篇 |
2015年 | 9篇 |
2014年 | 24篇 |
2013年 | 30篇 |
2012年 | 21篇 |
2011年 | 18篇 |
2010年 | 19篇 |
2009年 | 16篇 |
2008年 | 12篇 |
2007年 | 9篇 |
2006年 | 10篇 |
2005年 | 13篇 |
2004年 | 7篇 |
2003年 | 8篇 |
2002年 | 6篇 |
2001年 | 3篇 |
2000年 | 8篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1973年 | 5篇 |
1972年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有312条查询结果,搜索用时 25 毫秒
251.
252.
The maleylpyruvate isomerase NagL from Ralstonia sp. strain U2, which has been structurally characterized previously, catalyzes the isomerization of maleylpyruvate to fumarylpyruvate. It belongs to the class zeta glutathione S-transferases (GSTZs), part of the cytosolic GST family (cGSTs). In this study, site-directed mutagenesis was conducted to probe the functions of 13 putative active site residues. Steady-state kinetic information for mutants in the reduced glutathione (GSH) binding site, suggested that (a) Gln64 and Asp102 interact directly with the glutamyl moiety of glutathione, (b) Gln49 and Gln64 are involved in a potential electron-sharing network that influences the ionization of the GSH thiol. The information also suggests that (c) His38, Asn108 and Arg109 interact with the GSH glycine moiety, (d) His104 has a role in the ionization of the GSH sulfur and the stabilization of the maleyl terminal carboxyl group in the reaction intermediate and (e) Arg110 influences the electron distribution in the active site and therefore the ionization of the GSH thiolate. Kinetic data for mutants altered in the substrate-binding site imply that (a) Arg8 and Arg176 are critical for maleylpyruvate orientation and enolization, and (b) Arg109 (exclusive to NagL) participates in kcat regulation. Surprisingly, the T11A mutant had a decreased GSH Km value, whereas little impact on maleylpyruvate kinetics was observed, suggesting that this residue plays an important role in GSH binding. An evolutionary trend in this residue appears to have developed not only in prokaryotic and eukaryotic GSTZs, but also among the wider class of cGSTs. 相似文献
253.
Although many cancer vaccines have been developed against type?I MAGE (melanoma antigen) genes owing to their shared tumour-specific expression properties, studies about their expression and functions are relatively limited. In the present study, we first identify a non-testis-specific type?I MAGE gene, Mageb18 (melanoma antigen family B 18). Mouse Mageb18 is also expressed in digestion- and immune-related tissues as well as testis, and its expression in testis is age-dependent. Mageb18 is expressed in many mouse-derived cell lines, and DNA demethylation and histone acetylation mediate the reactivation of Mageb18 in Mageb18-negtive H22 and C6 cells. We also show that mouse Mageb18 encodes a 46?kDa protein which is predominantly localized in the cytoplasm. In testis, the endogenous MAGEB18 protein is mainly expressed in proliferative spermatogonia and primary and secondary spermatocytes, but less so in spermatids. Finally, we demonstrate that knockdown of MAGEB18 inhibits the growth of B16-F0 cells and induces apoptosis, which correlates with increased levels of TP53 (tumour protein 53), p21, Bax and caspase 3. The results of the present study thus uncover an important phenomenon that the expression of certain type?I MAGE genes, at least for Mageb18, is non-testis-specific. Although they can regulate various malignant phenotypes of cancer cells, it is necessary to study further their expression pattern in normal tissues before using them to develop more effective and safer cancer vaccines. 相似文献
254.
Li Zou Rong Zhong Jiao Lou Xuzai Lu Qi Wang Yang Yang Jiahong Xia Juntao Ke Ti Zhang Yu Sun Li Liu Yongping Cui Haibing Xiao Lei Chang Ding Xia Hua Xu 《PloS one》2012,7(9)
Background
A common single nucleotide polymorphism (SNP), rs3802842, located at 11q23, was identified by genome-wide association studies (GWAS) to be significantly associated with the risk of colorectal cancer (CRC); however, the results of following replication studies were not always concordant. Thus, a case-control study and a meta-analysis were performed to clearly discern the effect of this variant in CRC.Method and Findings
We determined the genotypes of rs3802842 in 641 unrelated Chinese patients with CRC and 1037 cancer-free controls. Additionally, a meta-analysis comprising current and previously published studies was conducted. In our case-control study, significant associations between the polymorphism and CRC risk were observed in all genetic models, with an additive OR being 1.45 (95% CI = 1.26–1.67). The meta-analysis of 38534 cases and 39446 controls further confirmed the significant associations in all genetic models but with obvious between-study heterogeneity. Nevertheless, ethnicity, study type and whether subjects affected by Lynch syndrome could synthetically accounted for the heterogeneity. Besides, the cumulative and sensitivity analyses indicated the robust stability of the results.Conclusion
The results from our case-control study and meta-analysis provided convincing evidence that rs3802842 significantly contributed to CRC risk. 相似文献255.
Ding WY Ti Y Wang J Wang ZH Xie GL Shang YY Tang MX Zhang Y Zhang W Zhong M 《The international journal of biochemistry & cell biology》2012,44(6):1031-1039
Accumulation of collagen I and III in the myocardium is a prominent feature of interstitial fibrosis. Prostaglandin F(2α) (PGF(2α)) facilitates fibrosis by increasing collagen synthesis. However, the underlying mechanisms mediating the effect of PGF(2α) on collagen expression in cardiac fibroblasts are not yet fully elucidated. We measured the mRNA and protein levels of collagen I and III by quantitative real-time PCR and ELISA, respectively. Activation of signaling pathways was determined by western blot analysis. In primary rat cardiac fibroblasts, treatment with PGF(2α) stimulated both the mRNA and protein levels of collagen I and III, and pretreatment with the F-prostanoid (FP) receptor antagonist AL-8810, protein kinase C inhibitor LY-333531, and Rho kinase inhibitor Y-27632 significantly inhibited PGF(2α)-induced collagen I and III expression. FP receptor, protein kinase C, and Rho kinase were activated with PGF(2α) treatment. PGF(2α) may be an important regulator in the synthesis of collagen I and III via an FP receptor/protein kinase C/Rho kinase cascade in cardiac fibroblasts, which might be a new therapeutic target for myocardial fibrosis. 相似文献
256.
GUO Xian‐guo GONG Zheng‐da QIAN Ti‐jun FENG Xi‐guan DUAN Xing‐de LI Wei ZHANG Xi‐kun 《Insect Science》2000,7(1):47-52
Abstract Xenopsylla chewpis is the main transmitting vector of plague in the foci of human plague in Yunnan China, where its dominant rat host is Rattus flavipectus Spatial distribution pattern of X. cheopis among the individuals of R fluvipectus is studied. Iwao's linear regression method and a significance test of random deviation for the method were used. in the light of Iwao's method, a regression model was established. The model is M =α+βM = 4.0064 + 2.0153M where both α and β are considerably higher than 0 and 1 respectively, the border values for determining spatial pattern of populations. The calculated F value is 4, 5892 (P<0.05) in the significance test of random deviation. The spatial pattern of X. cheopis among the individuals of its dominant host R flavipectus is of an aggregate distribution. The aggregated distribution pattern means that the flea individuals do not evenly distribute on rat host but gather as different size groups on rat individuals. This uneven distribution further suggests that the transmitting opportunity is not always the same even if the frequency of contacting the same species of infected rat, R flavipectus is the same. 相似文献
257.
Zhenzhen?Zhai Xingliang?Ma Lingling?Yang Jinfeng?Ti Daozhen?Song Shijun?Fu Dapeng?Li Weishan?ChangEmail author Jing?ZhaiEmail author 《Genes & genomics.》2016,38(8):767-777
Few studies have attempted to characterize the pheasant (Phasianus colchicus) immunoglobulin Y (IgY) heavy chain constant region. In the present study, fragments of the pheasant IgY heavy chain constant region were cloned, analyzed, and expressed. The cross-reactivity of IgY or immunoglobulin G (IgG)s with antigens from other vertebrate species was determined using dot-enzyme-linked immunosorbent assay and western blot analysis. Five peptides of the pheasant IgY heavy chain constant region were synthesized to determine its immunoregulatory activity in vitro. The IgY heavy chain constant region from pheasant showed the highest homology with that from chicken (71.2 %) and duck (49.1 %). Phylogenetic analysis for IgY showed that pheasant was closely related to chicken and duck than to any other analyzed vertebrate species. The rabbit anti-chicken IgG showed immunologic cross-reactivity with recombinant proteins of the pheasant IgY heavy chain constant region. Four peptides were able to induce significant up-regulation of interleukin (IL)-1β, IL-4, and interferon-γ in chicken peripheral blood lymphocytes, suggesting a new role of avian IgY in immune regulation. 相似文献
258.
Production of the virus‐like particles of nipah virus matrix protein in Pichia pastoris as diagnostic reagents 下载免费PDF全文
Narcisse MS Joseph Kok Lian Ho Beng Ti Tey Chon Seng Tan Norazizah Shafee Wen Siang Tan 《Biotechnology progress》2016,32(4):1038-1045
The matrix (M) protein of Nipah virus (NiV) is a peripheral protein that plays a vital role in the envelopment of nucleocapsid protein and acts as a bridge between the viral surface and the nucleocapsid proteins. The M protein is also proven to play an important role in production of virus‐like particles (VLPs) and is essential for assembly and budding of NiV particles. The recombinant M protein produced in Escherichia coli assembled into VLPs in the absence of the viral surface proteins. However, the E. coli produced VLPs are smaller than the native virus particles. Therefore, the aims of this study were to produce NiV M protein in Pichia pastoris, to examine the structure of the VLPs formed, and to assess the potential of the VLPs as a diagnostic reagent. The M protein was successfully expressed in P. pastoris and was detected with anti‐myc antibody using Western blotting. The VLPs formed by the recombinant M protein were purified with sucrose density gradient ultracentrifugation, high‐performance liquid chromatography (HPLC), and Immobilized Metal Affinity Chromatography (IMAC). Immunogold staining and transmission electron microscopy confirmed that the M protein assembled into VLPs as large as 200 nm. ELISA revealed that the NiV M protein produced in P. pastoris reacted strongly with positive NiV sera demonstrating its potential as a diagnostic reagent. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1038–1045, 2016 相似文献
259.
Using a large phage antibody library, a protein microarray spotted directly with phage-displayed antibody clones was created to discriminate between recognition profiles of samples from healthy donors and leukemia patients. The protocol for preparing antibody-displaying phage chips was presented. Some conditions such as substrates and blocking buffers were compared and optimized. The major improvements of this microarray are higher throughput and lower cost compared to previous antibody chips. Due to its convenience and sensitivity, it can be extensively used for rapid and high throughput detection of protein profiles of experimental and clinical samples. 相似文献
260.
Chien Wei Ooi Beng Ti Tey Siew Ling Hii Arbakariya Ariff Ho Shing Wu John Chi Wei Lan Ruey Shin Juang Siti Mazlina Mustapa Kamal Tau Chuan Ling 《Biotechnology and Bioprocess Engineering》2009,14(6):811-818
An aqueous two-phase purification process was employed for the recovery of Burkholderia pseudomallei lipase from fermentation broth. The partition behavior of B. pseudomallei lipase was investigated with various parameters such as phase composition, tie-line length (TLL), volume ratio (VR), sample loading, system pH, and addition of neutral salts. Optimum conditions for the purification of lipase were obtained
in polyethylene glycol (PEG) 6000-potassium phosphate system using TLL of 42.2% (w/w), with VR of 2.70, and 1% (w/w) NaCl
addition at pH 7 for 20% (w/w) crude load. Based on this system, the purification factor of lipase was enhanced to 12.42 fold,
with a high yield of 93%. Hence, the simplicity and effectiveness of aqueous two-phase systems (ATPS) in the purification
of lipase were proven in this study. 相似文献