全文获取类型
收费全文 | 169篇 |
免费 | 12篇 |
专业分类
181篇 |
出版年
2023年 | 3篇 |
2022年 | 9篇 |
2021年 | 5篇 |
2020年 | 4篇 |
2019年 | 8篇 |
2018年 | 6篇 |
2017年 | 3篇 |
2016年 | 9篇 |
2015年 | 9篇 |
2014年 | 3篇 |
2013年 | 20篇 |
2012年 | 9篇 |
2011年 | 7篇 |
2010年 | 5篇 |
2009年 | 6篇 |
2008年 | 9篇 |
2007年 | 5篇 |
2006年 | 2篇 |
2005年 | 9篇 |
2003年 | 1篇 |
2002年 | 6篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 5篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1967年 | 1篇 |
1966年 | 2篇 |
1965年 | 1篇 |
排序方式: 共有181条查询结果,搜索用时 15 毫秒
151.
Neuroblastoma is a tumor of postganglionic sympathetic origin, and nerve growth factor (NGF) is normally required for the survival and differentiation of sympathetic neuroblasts. Since the biological activity of NGF is mediated by the NGF receptor (NGFR), we hypothesized that defects in the NGF/NGFR pathway may play a role in maintenance of the undifferentiated state of neuroblastomas. To test this hypothesis, we examined the structure of the NGFR at the DNA, RNA, and protein levels in a panel of 10 neuroblastoma cell lines. In addition, we examined the function of the NGFR in these lines by analysis of NGF binding kinetics, as well as by the ability of NGF to induce c-fos expression and neurite outgrowth. Southern blot analysis showed that all 10 cell lines possess apparently normal NGFR genes. Northern blot and ligand binding/immunoprecipitation assays revealed four receptor-positive cell lines (NGP, NLF, SK-N-SH, and LA-N-6), with NGFR mRNA and protein of expected sizes (3.8 kilobases and Mr approximately 75,000, respectively). NGF binding assays and Scatchard analyses were performed on the four NGFR-positive lines. The NGP line possesses only low-affinity receptor (Kd approximately 3.5 x 10(-9)), whereas the other three lines express both low- and high-affinity forms (Kd approximately 10(-9) and Kd approximately 10(-11), respectively). However, none of the 10 lines exhibited a response to NGF treatment as assayed by c-fos mRNA induction and neurite extension.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
152.
In cell suspension of Desulfovibrio desulfuricans B-1388, oxidation of CO as the only energy source is associated with reduction of SO42-. After a 2-h incubation of cells in 8% CO, 81% of the gas is converted. Oxidation of 1 mole CO results in formation of 0.23 mole H2S. Intracellular ATP content increases from 2.5 (control) to 8.3 nmoles/mg (during CO conversion). Dinitrophenol inhibits sulfate reduction and CO oxidation. CO dehydrogenase was detected in cytoplasmic and membrane cell fractions (59 and 34%, respectively). 相似文献
153.
154.
Neostatin-7, with an anti-angiogenic potential, is generated from the proteolytic action of matrix metalloproteinase-7 on collagen XVIII. We previously reported that neostatin-7 inhibited angiogenesis in vitro and in vivo. Here we demonstrate that neostatin-7/collagen XVIII may possess anti-lymphangiogenic activities by: (1) corneal micropellet implantation of neostatin-7 reduced bFGF-induced corneal lymphangiogenesis; (2) neostatin-7 bound to VEGF receptor-3 in vitro; and (3) enhanced corneal lymphangiogenesis and VEGF-C expression in collagen XVIII knockout mice in a corneal wounding model. Understanding the mechanism of neostatin-7/collagen XVIII on corneal lymphangiogenesis may provide therapeutic interventions to treat lymphangiogenesis-related disorders, such as lymphedema, transplantation rejection and cancers. 相似文献
155.
We describe a proteomic approach to investigate the differential protein expression patterns and identify the physiologically relevant angiogenic and antiangiogenic factors involved in the hyaloid vascular system regression. Differentially expressed proteins were identified using two-dimensional gel electrophoresis followed by nanoflow chromatography coupled with tandem mass spectrometry. These proteins are expected to provide insight as to their function in the early maintenance and eventual regression of the hyaloid vascular system. 相似文献
156.
Chattopadhyay MB Mukherjee S Kulkarni I Vijayan V Doloi M Kanjilal N Chatterjee M 《Cancer cell international》2005,5(1):16
Combined effect of vanadium and beta-carotene on rat liver DNA-chain break and Proton induced X-ray emission (PIXE) analysis
was studied during a necrogenic dose (200 mg/kg of body weight) of Diethyl Nitrosamine (DENA) induced rat liver carcinogenesis.
Morphological and histopathological changes were observed as an end point biomarker. Supplementation of vanadium (0.5 ppm
ad libitum) in drinking water and beta-carotene in the basal diet (120 mg/Kg of body weight) were performed four weeks before DENA treatment
and continued till the end of the experiment (16 weeks). PIXE analysis revealed the restoration of near normal value of zinc,
copper, and iron, which were substantially altered when compared to carcinogen treated groups. Supplementation of both vanadium
and beta-carotene four weeks before DENA injection was found to offer significant (64.73%, P < 0.001) protection against generation
of single-strand breaks when compared with the carcinogen control counter parts. A significant stabilization of hepatic architecture
of the cells was observed as compared to carcinogen control in vanadium plus beta-carotene treated group. This study thus
suggests that vanadium, a prooxidant but potential therapeutic agent yield safe and effective pharmacological formulation
with beta-carotene, an antioxidant, in the inhibition of experimental rat hepatocarcinogenesis. 相似文献
157.
Jenett-Siems K Weigl R Böhm A Mann P Tofern-Reblin B Ott SC Ghomian A Kaloga M Siems K Witte L Hilker M Müller F Eich E 《Phytochemistry》2005,66(12):1448-1464
The occurrence and distribution of tropane and biogenetically related pyrrolidine alkaloids in 18 Merremia species of paleo-, neo-, and pantropical occurrence have been studied. The extensive GC-MS study included members of almost all sections of the genus and has been carried out with epigeal vegetative parts as well as with roots. It comprises altogether 74 tropanes and 13 pyrrolidines including nicotine. Along with datumetine known already from a solanaceous species, the study led to the isolation (from M. dissecta and M. guerichii, respectively) and structure elucidation (spectral data) of four novel 3alpha-acyloxytropanes, merresectines A-D: 3alpha-(4-methoxybenzoyloxy)nortropane (A), 3alpha-kurameroyloxytropane (B), 3alpha-nervogenoyloxytropane (C), 3alpha-[4-(beta-D-glucopyranosyloxy)-3-methoxy-5-(3-methyl-2-butenyl)benzoyloxy]tropane (beta-d-glucoside of D). Moreover, the novel 3alpha,6beta-di-(4-methoxybenzoyloxy)tropane (merredissine) has been isolated from M. dissecta and structurally elucidated. In addition the structures of datumetine and merresectine A could be confirmed by synthesis. Spectral data for two known 3alpha-acyloxytropanes (merresectine E beta-D-glucoside, 4'-dihydroconsabatine) and one known 3beta-acyloxytropane (concneorine) are documented for the first time. The structures of three further merresectines (F-H) have been determined by mass spectrometry. Furthermore, the linkage (2',3- and 2',4-, respectively) of two position isomer N-methylpyrrolidinylhygrines was proven by synthesis. The results of the study contribute to the solution of infrageneric taxonomic problems. Whereas all species yield pyrrolidine alkaloids without suitably differentiating results the diverging occurrence of tropane alkaloids leads to three groups of sections: (1) taxa free of tropanes, (2) taxa with simple tropanes, and (3) taxa with merresectines in addition to simple tropanes. 相似文献
158.
Paris I Dagnino-Subiabre A Marcelain K Bennett LB Caviedes P Caviedes R Azar CO Segura-Aguilar J 《Journal of neurochemistry》2001,77(2):519-529
The mechanism of copper (Cu) neurotoxicity was studied in the RCSN-3 neuronal dopaminergic cell line, derived from substantia nigra of an adult rat. The formation of a Cu-dopamine complex was accompanied by oxidation of dopamine to aminochrome. We found that the Cu-dopamine complex mediates the uptake of (64)CuSO(4) into the Raúl Caviedes substantia nigra-clone 3 (RCSN3) cells, and it is inhibited by the addition of excess dopamine (2 m M) (63%, p < 0.001) and nomifensine (2 microM) (77%, p < 0.001). Copper sulfate (1 m M) alone was not toxic to RCSN-3 cells, but was when combined with dopamine or with dicoumarol (95% toxicity; p < 0.001) which inhibits DPNH and TPNH (DT)-diaphorase. Electron spin resonance (ESR) spectrum of the 5,5-dimethylpyrroline-N-oxide (DMPO) spin trap adducts showed the presence of a C-centered radical when incubating cells with dopamine, CuSO(4) and dicoumarol. A decrease in the expression of CuZn-superoxide dismutase and glutathione peroxidase mRNA was observed when RCSN-3 cells were treated with CuSO(4), dopamine, or CuSO(4) and dopamine. However, the mRNA expression of glutathione peroxidase remained at control levels when the cells were treated with CuSO(4), dopamine and dicoumarol. The regulation of catalase was different since all the treatments with CuSO(4) increased the expression of catalase mRNA. Our results suggest that copper neurotoxicity is dependent on: (i) the formation of Cu-dopamine complexes with concomitant dopamine oxidation to aminochrome; (ii) dopamine-dependent Cu uptake; and (iii) one-electron reduction of aminochrome. 相似文献
159.
Mohsen Nikpour Hamid Sadeghian Mohammad Reza Saberi Reza Shafiee Nick Seyed Mohammad Seyedi Azar Hosseini Heydar Parsaee Alireza Taghian Dasht Bozorg 《Bioorganic & medicinal chemistry》2010,18(2):855-862
Selective PDE3 (phosphodiesterase 3) inhibitors improve cardiac contractility and may be used in congestive heart failure. However, their proarrhythmic potential is the most important side effect. In this work ten new synthetic compounds (3-[(4-methyl-2-oxo-1,2-dihydro-6-quinolinyl)oxy]methylbenzamide analogs: 4a–j) were designed, synthesized and tested for the inhibitory activity against human PDE3A and PDE3B. The strategy of the design was based on the structure of vesnarinone (a selective PDE3 inhibitor) and its docking analysis results. The synthetic compounds showed better PDE3 inhibitory activity in comparison with vesnarinone. Using docking analysis, a common binding model of each compound toward PDE3 was suggested. In the next step the potential cardiotonic activity of the best PDE3A inhibitors (4b, IC50 = 0.43 ± 0.04 μM) was evaluated by using the spontaneously beating atria model. In the experiment, atrium of reserpine-treated rat was isolated and the contractile and chronotropic effects of the synthetic compound were assessed. That was carried out in comparison with vesnarinone. The best pharmacological profile was obtained for the compound 4b, which displayed selectivity for increasing the force of contraction (46 ± 3% change over the control) rather than the frequency rate (16 ± 4% change over the control) at 100 μM. 相似文献
160.
Hunter NB Moseley 《BMC bioinformatics》2010,11(1):139