全文获取类型
收费全文 | 1724篇 |
免费 | 94篇 |
出版年
2023年 | 6篇 |
2022年 | 22篇 |
2021年 | 38篇 |
2020年 | 18篇 |
2019年 | 29篇 |
2018年 | 46篇 |
2017年 | 36篇 |
2016年 | 52篇 |
2015年 | 67篇 |
2014年 | 85篇 |
2013年 | 135篇 |
2012年 | 133篇 |
2011年 | 135篇 |
2010年 | 83篇 |
2009年 | 64篇 |
2008年 | 130篇 |
2007年 | 126篇 |
2006年 | 105篇 |
2005年 | 102篇 |
2004年 | 90篇 |
2003年 | 81篇 |
2002年 | 76篇 |
2001年 | 11篇 |
2000年 | 6篇 |
1999年 | 9篇 |
1998年 | 22篇 |
1997年 | 7篇 |
1996年 | 15篇 |
1995年 | 14篇 |
1994年 | 10篇 |
1993年 | 9篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 10篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 8篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1963年 | 1篇 |
1959年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有1818条查询结果,搜索用时 31 毫秒
81.
Tomikura Y Hisatome I Tsuboi M Yamawaki M Shimoyama M Yamamoto Y Sasaki N Ogino K Igawa O Shigemasa C Ishiguro S Ohgi S Nanba E Shiota G Morisaki H Morisaki T Kitakaze M 《Biochemical and biophysical research communications》2003,302(2):372-376
Despite the heteroplasmic lower population of mitochondrial (mt) DNA deletion, mtDNA deletion is significantly related to the loss of atrial adenine nucleotides. To elucidate its mechanism, we examined the frequency of a 7.4-kb mtDNA deletion, the concentration of adenine nucleotides, and the activity of AMP catabolic enzymes in 10 human right atria obtained from cardiac surgery, using quantitative PCR, HPLC, and immunoprecipitations. The atrial concentrations of ATP, ADP, AMP, and the total adenine nucleotides were significantly lower in patients with deletion than those in patients without deletion, despite the lower frequency of their deletion. The activities of total AMP deaminase (AMPD), liver-type (AMPD 2), and heart-type isoform (AMPD 3) were significantly higher in patients with deletion than in patients without deletion, although there was no significant difference in the cytosolic 5(')-nucleotidase among them. In conclusion, mtDNA deletion coordinately induces AMP deaminase to contribute to the loss of atrial adenine nucleotides through degrading AMP excessively. 相似文献
82.
Upregulation of cAMP is a new functional signal pathway of Klotho in endothelial cells 总被引:3,自引:0,他引:3
Yang J Matsukawa N Rakugi H Imai M Kida I Nagai M Ohta J Fukuo K Nabeshima Y Ogihara T 《Biochemical and biophysical research communications》2003,301(2):424-429
We measured angiotensin I-converting enzyme (ACE) activity in a human endothelial cell to characterize the intracellular signal pathways of Klotho. COS-1 cells transfected with naked mouse membrane-form klotho plasmid DNA (pCAGGS-klotho) translated proper Klotho protein. This translated Klotho protein was secreted into the culture medium. Furthermore, ACE activity in human umbilical vein endothelial cells (HUVEC) was upregulated when HUVEC were co-cultured with COS-1 cells that were pre-transfected with pCAGGS-klotho. The conditioned medium from COS-1 cells pre-transfected with pCAGGS-klotho also dose-dependently upregulated ACE in HUVEC. In addition, the conditioned medium induced time- and dose-dependent enhancement of cAMP production in HUVEC. Rp-cAMP, an inhibitor of cAMP-dependent protein kinase A (PKA), inhibited the upregulation of ACE by Klotho protein. Our results suggest that mouse membrane-form Klotho protein acts as a humoral factor to increase ACE activity in HUVEC via a cAMP-PKA-dependent pathway. These findings may provide a new insight into the mechanism of Klotho protein. 相似文献
83.
Chiba H Gotoh T Kojima T Satohisa S Kikuchi K Osanai M Sawada N 《Experimental cell research》2003,286(2):288-297
F9 murine embryonal carcinoma cells provide an attractive system for facilitating molecular mechanisms for epithelial morphogenesis, since they have the capability of differentiating into polarized epithelial cells bearing an apical junctional complexes. We previously showed that a specific retinoid X receptor-retinoic acid receptor heterodimer transduced retinoid signals for biogenesis of functional tight junctions in F9 cells (Exp. Cell Res. 263, (2001) 163). In the present study we generated F9 cells expressing doxycycline-inducible hepatocyte nuclear factor (HNF)-4alpha, a nuclear receptor. We herein show that induction of HNF-4alpha initiates differentiation of F9 cells to polarized epithelial cells, in which tight-junction proteins occludin, claudin-6, claudin-7, and ZO-1 are concentrated at the apical-most regions of lateral membranes. Expression of occludin, claudin-6, and claudin-7 was induced in the cells by doxycycline treatment in a dose- and time-dependent manner, in terms of the amount of HNF-4alpha. In contrast, expression levels of ZO-1, ZO-2, E-cadherin, and beta-catenin were not altered by HNF-4alpha. We also demonstrate, by analysis of diffusion of labeled sphingomyelin, that the fence function of tight junctions is achieved by induction of HNF-4alpha. These findings indicate that HNF-4alpha triggers de novo formation of functional tight junctions and establishment of epithelial cell polarity. 相似文献
84.
Hashiguchi S Nakashima T Nitani A Yoshihara T Yoshinaga K Ito Y Maeda Y Sugimura K 《Journal of biochemistry》2003,133(1):43-49
The alpha-chain of Fc epsilon RI (Fc epsilon RIalpha) plays a critical role in the binding of IgE to Fc epsilon RI. A fully human antibody interfering with this interaction may be useful for the prevention of IgE-mediated allergic diseases. Here, we describe the successful isolation of a human single-chain Fv antibody specific to human Fc epsilon RIalpha using human antibody phage display libraries. Using the non-immune phage antibody libraries constructed from peripheral blood lymphocyte cDNA from 20 healthy subjects, we isolated three phage clones (designated as FcR epsilon 27, FcR epsilon 51, and FcR epsilon 70) through two rounds of biopanning selection. The purified soluble scFv, FcR epsilon 51, inhibited the binding of IgE to recombinant Fc epsilon RIalpha, although both FcR epsilon 27 and FcR epsilon 70 showed fine binding specificity to Fc epsilon RIalpha. Since FcR epsilon 51 was determined to be a monomer by HPLC, BIAcore analysis was performed. The dissociation constant of FcR epsilon 51 to Fc epsilon RIalpha was estimated to be 20 nM, i.e., fortyfold lower than that of IgE binding to Fc epsilon RIalpha (K(d) = 0.5 nM). With these characteristics, FcR epsilon 51 exhibited inhibitory activity on the release of histamine from passively sensitized human peripheral blood mononuclear cells. 相似文献
85.
A member of Forkhead transcription factor FKHRL1 is a downstream effector of STI571-induced cell cycle arrest in BCR-ABL-expressing cells 总被引:6,自引:0,他引:6
Komatsu N Watanabe T Uchida M Mori M Kirito K Kikuchi S Liu Q Tauchi T Miyazawa K Endo H Nagai T Ozawa K 《The Journal of biological chemistry》2003,278(8):6411-6419
86.
87.
Construction of a human immunodeficiency virus type 1 (HIV-1) library containing random combinations of amino acid substitutions in the HIV-1 protease due to resistance by protease inhibitors 下载免费PDF全文
Human immunodeficiency virus type 1 (HIV-1) heterogeneity contributes to the emergence of drug-resistant virus, escape from host defense systems, and/or conversion of the cellular tropism. To establish an in vitro system to address a heterogeneous virus population, we constructed a library of HIV-1 molecular clones containing a set of random combinations of zero to 11 amino acid substitutions associated with resistance to protease inhibitors by the HIV-1 protease. The complexity (2.1 x 10(5)) of the HIV-1 library pNG-PRL was large enough to cover all of the possible combinations of zero to 11 amino acid substitutions (a total of 4,096 substitutions possible). The T-cell line MT-2 was infected with the HIV-1 library, and resistant viruses were selected after treatment by the protease inhibitor ritonavir (0.03 to 0.30 microM). The viruses that contained three to eight amino acid substitutions could be selected within 2 weeks. These results demonstrate that this HIV-1 library could serve as an alternative in vitro system to analyze the emergence of drug resistance and to evaluate the antiviral activity of novel compounds against multidrug-resistant viruses. 相似文献
88.
Effects of amino acid alterations on the transglycosylation reaction of endoglucanase I from Trichoderma viride HK-75 总被引:1,自引:0,他引:1
Kwon I Ekino K Oka T Goto M Furukawa K 《Bioscience, biotechnology, and biochemistry》2002,66(1):110-116
Endoglucanase I (EGI) from Trichoderma viride HK-75 catalyzes not only hydrolysis but also transglycosylation reactions of cellooligosaccharides. In order to characterize the important amino acid residues in transglycosylation of EGI, three Tyr, one Leu, and two Glu residues of EGI were replaced by Trp or Asp. The seven resulting EGI, except for L200W, had reduced activities toward carboxymethyl-cellulose compared to that of wild type EGI. The results from the mutations in the catalytic residues of E196 and E201 indicate that the space just around the catalytic residues is not directly related to the transglycosylation reactions of EGI. Analyses of the enzymes with mutations in the substrate-binding residues showed that Y146, Y170, and L200 of EGI are closely involved in the mode of transglycosylation and that several amino acid residues within the active site are involved in the transglycosylation reaction of EGI. 相似文献
89.
FGF10 maintains stem cell compartment in developing mouse incisors 总被引:27,自引:0,他引:27
Harada H Toyono T Toyoshima K Yamasaki M Itoh N Kato S Sekine K Ohuchi H 《Development (Cambridge, England)》2002,129(6):1533-1541
Mouse incisors are regenerative tissues that grow continuously throughout life. The renewal of dental epithelium-producing enamel matrix and/or induction of dentin formation by mesenchymal cells is performed by stem cells that reside in cervical loop of the incisor apex. However, little is known about the mechanisms of stem cell compartment formation. Recently, a mouse incisor was used as a model to show that fibroblast growth factor (FGF) 10 regulates mitogenesis and fate decision of adult stem cells. To further illustrate the role of FGF10 in the formation of the stem cell compartment during tooth organogenesis, we have analyzed incisor development in Fgf10-deficient mice and have examined the effects of neutralizing anti-FGF10 antibody on the developing incisors in organ cultures. The incisor germs of FGF10-null mice proceeded to cap stage normally. However, at a later stage, the cervical loop was not formed. We found that the absence of the cervical loop was due to a divergence in Fgf10 and Fgf3 expression patterns at E16. Furthermore, we estimated the growth of dental epithelium from incisor explants of FGF10-null mice by organ culture. The dental epithelium of FGF10-null mice showed limited growth, although the epithelium of wild-type mice appeared to grow normally. In other experiments, a functional disorder of FGF10, caused by a neutralizing anti-FGF10 antibody, induced apoptosis in the cervical loop of developing mouse incisor cultures. However, recombinant human FGF10 protein rescued the cervical loop from apoptosis. Taken together, these results suggest that FGF10 is a survival factor that maintains the stem cell population in developing incisor germs. 相似文献
90.
Fujita H Koji T Kitagawa N Tsutsumi K Abe K Kaminogo M Shibata S 《Cellular and molecular neurobiology》2002,22(4):393-406
1. For a better understanding of the biological features of astrocytic tumors, we investigated apoptosis and its pathway, especially in the interaction between Fas and Fas ligand (FasL).2. We examined the presence of apoptosis in human astrocytic brain tumors by terminal deoxynucleotidyl transferase (TdT)-mediated d-UTP-biotin nick end labeling (TUNEL) and then apoptotic index (AI) was calculated. We also examined the distribution of Fas and FasL-positive tumor cells immunohistochemically. Labeling index (LI) for Fas and FasL was calculated as Fas-LI and FasL-LI, respectively, and compared to AI.3. Tumor cells expressing both Fas and FasL were TUNEL positive. Such cells were distributed sparsely in low-grade astrocytomas, but focally in glioblastomas. There was a close correlation among AI, Fas-LI, and FasL-LI, and astrocytic tumors with higher AI were associated with a longer survival time than that with lower AI.4. It was concluded that the Fas system may be involved in the apoptosis of astrocytic tumors, and AI can be a useful parameter for assessing prognosis of astrocytic tumors. 相似文献