全文获取类型
收费全文 | 265篇 |
免费 | 19篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 1篇 |
综合类 | 5篇 |
化学工业 | 176篇 |
金属工艺 | 10篇 |
机械仪表 | 15篇 |
建筑科学 | 6篇 |
轻工业 | 32篇 |
无线电 | 12篇 |
一般工业技术 | 31篇 |
冶金工业 | 3篇 |
原子能技术 | 4篇 |
自动化技术 | 1篇 |
出版年
2023年 | 5篇 |
2022年 | 54篇 |
2021年 | 59篇 |
2020年 | 12篇 |
2019年 | 9篇 |
2018年 | 7篇 |
2017年 | 8篇 |
2016年 | 8篇 |
2015年 | 10篇 |
2014年 | 12篇 |
2013年 | 15篇 |
2012年 | 10篇 |
2011年 | 7篇 |
2010年 | 7篇 |
2009年 | 6篇 |
2008年 | 10篇 |
2007年 | 3篇 |
2006年 | 10篇 |
2005年 | 8篇 |
2004年 | 9篇 |
2003年 | 2篇 |
2002年 | 8篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1997年 | 2篇 |
1995年 | 2篇 |
1991年 | 2篇 |
1982年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有296条查询结果,搜索用时 15 毫秒
21.
目的在植物毛状根和毕赤酵母中表达人碱性成纤维细胞生长因子(Human basic fibroblast growth factor,hbFGF),并对发酵条件进行优化。方法将hbFGF基因分别克隆至表达载体pCAMBIA1301和pPICZα上,构建重组表达质粒pCAMBIA1301-hbFGF和pPICZα-hbFGF。通过发根农杆菌介导,将pCAMBIA1301-hbFGF质粒转入大豆毛状根;采用电转化法将质粒pPICZα-hbFGF转入毕赤酵母X-33菌株,PCR法筛选阳性转化子,诱导表达。筛选高效稳定表达株,发酵培养并优化发酵条件,SDS-PAGE和Western blot分析表达产物,并进行纯化。结果经酶切及测序证明两个重组表达质粒构建正确;经PCR鉴定证明hbFGF基因已整合入大豆毛状根及毕赤酵母基因组中;筛选出了在两种体系中发酵培养的最佳条件;hbFGF在大豆毛状根和毕赤酵母中的表达量分别占总蛋白的31%和42%,且均具有良好的反应原性;经纯化后,均可见相对分子质量约18000的单一条带。结论 hbFGF能够在大豆毛状根和毕赤酵母中高效表达,为其大规模工业化生产奠定了实验基础。 相似文献
22.
目的:研究抗成纤维细胞生长因子(FGF-2)纳米抗体对碱烧伤诱导的大鼠角膜血管生成的治疗作用。方法:将SD大鼠分为:假手术组(Sham),模型组(Model,直径为3 mm的浸有1 mol/L NaOH溶液圆形滤纸贴于大鼠眼角膜中央处30 s,制备大鼠碱烧伤血管生成模型)和治疗组(Treatment,术后7天至21天用3 mg/mL的抗FGF-2纳米抗体溶液滴眼,每日3次,每次10 μL,共14天)。通过体视显微镜和CD31免疫组织化学染色计算大鼠角膜血管生成情况。实时荧光定量PCR、酶联免疫吸附测定和免疫组织化学染色3种方法检测抗血管内皮生长因子(VEGF)和FGF-2的mRNA和蛋白表达水平。结果:(1)血管:治疗组较模型组的面积显著减少,血管管腔较窄(P<0.05),在药物干预14天后,差异最为显著;(2)FGF-2的mRNA和蛋白表达水平:模型组与治疗组的结果相近(P>0.05);(3)VEGF的mRNA和蛋白表达水平:治疗组显著高于模型组(P<0.05)。此外,假手术组的持续给药也使得VEGF表达显著增加(P<0.05)。 结论:抗FGF-2纳米抗体可抑制由碱烧伤诱导的角膜血管新生,但也使得正常大鼠角膜或病理大鼠角膜的VEGF表达水平代偿性升高。 相似文献
23.
本研究以燕麦麸皮为原料,研究了燕麦麸皮中蛋白质在Alcalase酶的作用下的水解,测定了其在不同水解时间下的水解产物的分子量,并对燕麦麸皮水解产物去除羟自由基能力和人皮肤成纤维细胞增殖情况进行了初步测定。结果表明,用Alcalase酶水解燕麦麸皮,水解时间越长,水解产物分子量越小;Alcalase酶解产物具有去除羟自由基的能力以及对人皮肤成纤维细胞的增殖能力。本试验为燕麦麸皮水解产物应用于化妆品提供了一定的理论基础。 相似文献
24.
Lejla Medzikovic Hylja Heese Pieter B. van Loenen Cindy P. A. A. van Roomen Ingeborg B. Hooijkaas Vincent M. Christoffels Esther E. Creemers Carlie J. M. de Vries Vivian de Waard 《International journal of molecular sciences》2021,22(4)
Fibrosis is a hallmark of adverse cardiac remodeling, which promotes heart failure, but it is also an essential repair mechanism to prevent cardiac rupture, signifying the importance of appropriate regulation of this process. In the remodeling heart, cardiac fibroblasts (CFs) differentiate into myofibroblasts (MyoFB), which are the key mediators of the fibrotic response. Additionally, cardiomyocytes are involved by providing pro-fibrotic cues. Nuclear receptor Nur77 is known to reduce cardiac hypertrophy and associated fibrosis; however, the exact function of Nur77 in the fibrotic response is yet unknown. Here, we show that Nur77-deficient mice exhibit severe myocardial wall thinning, rupture and reduced collagen fiber density after myocardial infarction and chronic isoproterenol (ISO) infusion. Upon Nur77 knockdown in cultured rat CFs, expression of MyoFB markers and extracellular matrix proteins is reduced after stimulation with ISO or transforming growth factor–β (TGF-β). Accordingly, Nur77-depleted CFs produce less collagen and exhibit diminished proliferation and wound closure capacity. Interestingly, Nur77 knockdown in neonatal rat cardiomyocytes results in increased paracrine induction of MyoFB differentiation, which was blocked by TGF-β receptor antagonism. Taken together, Nur77-mediated regulation involves CF-intrinsic promotion of CF-to-MyoFB transition and inhibition of cardiomyocyte-driven paracrine TGF-β-mediated MyoFB differentiation. As such, Nur77 provides distinct, cell-specific regulation of cardiac fibrosis. 相似文献
25.
Nadezhda A. Evtushenko Arkadii K. Beilin Erdem B. Dashinimaev Rustam H. Ziganshin Anastasiya V. Kosykh Maxim M. Perfilov Alexandra L. Rippa Elena V. Alpeeva Andrey V. Vasiliev Ekaterina A. Vorotelyak Nadya G. Gurskaya 《International journal of molecular sciences》2021,22(8)
The recessive form of dystrophic epidermolysis bullosa (RDEB) is a crippling disease caused by impairments in the junctions of the dermis and the basement membrane of the epidermis. Using ectopic expression of hTERT/hTERT + BMI-1 in primary cells, we developed expansible cultures of RDEB fibroblasts and keratinocytes. We showed that they display the properties of their founders, including morphology, contraction ability and expression of the respective specific markers including reduced secretion of type VII collagen (C7). The immortalized keratinocytes retained normal stratification in 3D skin equivalents. The comparison of secreted protein patterns from immortalized RDEB and healthy keratinocytes revealed the differences in the contents of the extracellular matrix that were earlier observed specifically for RDEB. We demonstrated the possibility to reverse the genotype of immortalized cells to the state closer to the progenitors by the Cre-dependent hTERT switch off. Increased β-galactosidase activity and reduced proliferation of fibroblasts were shown after splitting out of transgenes. We anticipate our cell lines to be tractable models for studying RDEB from the level of single-cell changes to the evaluation of 3D skin equivalents. Our approach permits the creation of standardized and expandable models of RDEB that can be compared with the models based on primary cell cultures. 相似文献
26.
Olga V. Balberova Evgeny V. Bykov Natalia A. Shnayder Marina M. Petrova Oksana A. Gavrilyuk Daria S. Kaskaeva Irina A. Soloveva Kirill V. Petrov Elena Y. Mozheyko German V. Medvedev Regina F. Nasyrova 《International journal of molecular sciences》2021,22(12)
Regular physical activity in cyclic sports can influence the so-called “angiogenic switch”, which is considered as an imbalance between proangiogenic and anti-angiogenic molecules. Disruption of the synthesis of angiogenic molecules can be caused by local changes in tissues under the influence of excessive physical exertion and its consequences, such as chronic oxidative stress and associated hypoxia, metabolic acidosis, sports injuries, etc. A review of publications on signaling pathways that activate and inhibit angiogenesis in skeletal muscles, myocardium, lung, and nervous tissue under the influence of intense physical activity in cyclic sports. Materials: We searched PubMed, SCOPUS, Web of Science, Google Scholar, Clinical keys, and e-LIBRARY databases for full-text articles published from 2000 to 2020, using keywords and their combinations. Results: An important aspect of adaptation to training loads in cyclic sports is an increase in the number of capillaries in muscle fibers, which improves the metabolism of skeletal muscles and myocardium, as well as nervous and lung tissue. Recent studies have shown that myocardial endothelial cells not only respond to hemodynamic forces and paracrine signals from neighboring cells, but also take an active part in heart remodeling processes, stimulating the growth and contractility of cardiomyocytes or the production of extracellular matrix proteins in myofibroblasts. As myocardial vascularization plays a central role in the transition from adaptive heart hypertrophy to heart failure, further study of the signaling mechanisms involved in the regulation of angiogenesis in the myocardium is important in sports practice. The study of the “angiogenic switch” problem in the cerebrovascular and cardiovascular systems allows us to claim that the formation of new vessels is mediated by a complex interaction of all growth factors. Although the lungs are one of the limiting systems of the body in cyclic sports, their response to high-intensity loads and other environmental stresses is often overlooked. Airway epithelial cells are the predominant source of several growth factors throughout lung organogenesis and appear to be critical for normal alveolarization, rapid alveolar proliferation, and normal vascular development. There are many controversial questions about the role of growth factors in the physiology and pathology of the lungs. The presented review has demonstrated that when doing sports, it is necessary to give a careful consideration to the possible positive and negative effects of growth factors on muscles, myocardium, lung tissue, and brain. Primarily, the “angiogenic switch” is important in aerobic sports (long distance running). Conclusions: Angiogenesis is a physiological process of the formation of new blood capillaries, which play an important role in the functioning of skeletal muscles, myocardium, lung, and nervous tissue in athletes. Violation of the “angiogenic switch” as a balance between proangiogenic and anti-angiogenic molecules can lead to a decrease in the functional resources of the nervous, musculoskeletal, cardiovascular, and respiratory systems in athletes and, as a consequence, to a decrease in sports performance. 相似文献
27.
Ch. LAFFORGUE F. CROUTE J.F. NICOLAS D.J. HARTMANN E. DELAPORTE J. COTTE M.C. MARTINI 《International journal of cosmetic science》1991,13(3):125-136
Antielastase activity of derivatives like 'propionylaminoacid'(C3 prolin, C3 hydroxyprolin, C3 collagen) was examined for pancreatic elastase, and fibroblastic elastase production. Essential metabolic variations of normal dermal fibroblasts were evaluated: adhesion, proliferation capacity, total protein biosynthesis and collagen type I and type III production. Possible other factors such as cellular nutrients were examined by oxygen consumption evaluation.
Propionylaminoacid derivatives have antielastase activities. Pancreatic elastase showed dose related inhibition (20% to 50% inhibition for concentration from 5 to 80 mg ml−1 .
Moreover, fibroblastic elastase production was inhibited, cellular respiration was enhanced. A very good tolerance in vitro was observed for concentration 0–1 mg ml−1 range: adhesion, proliferation capacity and collagen (type I and type III) production were not altered, and oxygen consumption was enhanced. 相似文献
Propionylaminoacid derivatives have antielastase activities. Pancreatic elastase showed dose related inhibition (20% to 50% inhibition for concentration from 5 to 80 mg ml
Moreover, fibroblastic elastase production was inhibited, cellular respiration was enhanced. A very good tolerance in vitro was observed for concentration 0–1 mg ml
28.
试图通过对肿瘤病人皮肤成纤维细胞的离体培养和集落形成实验,检测正常皮肤组织的放射敏感性,为探索正常组织的辐射耐受性提供理论依据。运用组织贴块法体外培养肿瘤病人皮肤成纤维细胞;采用^137Csγ射线,不同剂量照射,以克隆形成法测定细胞的放射敏感性。结果表明,肿瘤病人皮肤成纤维细胞通过体外培养能够增殖传代,不同肿瘤病人皮肤成纤维细胞的放射敏感性存在明显的个体差异。 相似文献
29.
Fibroblast Growth Factor 21 Response in a Preclinical Alcohol Model of Acute-on-Chronic Liver Injury
Grigorios Christidis Ersin Karatayli Rabea A. Hall Susanne N. Weber Matthias C. Reichert Mathias Hohl Sen Qiao Ulrich Boehm Dieter Lütjohann Frank Lammert Senem Ceren Karatayli 《International journal of molecular sciences》2021,22(15)
Background and Aims: Fibroblast growth factor (FGF) 21 has recently been shown to play a potential role in bile acid metabolism. We aimed to investigate the FGF21 response in an ethanol-induced acute-on-chronic liver injury (ACLI) model in Abcb4−/− mice with deficiency of the hepatobiliary phospholipid transporter. Methods: Total RNA was extracted from wild-type (WT, C57BL/6J) and Abcb4−/− (KO) mice, which were either fed a control diet (WT-Cont and KO-Cont groups; n = 28/group) or ethanol diet, followed by an acute ethanol binge (WT-EtOH and KO-EtOH groups; n = 28/group). A total of 58 human subjects were recruited into the study, including patients with alcohol-associated liver disease (AALD; n = 31) and healthy controls (n = 27). The hepatic and ileal expressions of genes involved in bile acid metabolism, plasma FGF levels, and bile acid and its precursors 7α- and 27-hydroxycholesterol (7α- and 27-OHC) concentrations were determined. Primary mouse hepatocytes were isolated for cell culture experiments. Results: Alcohol feeding significantly induced plasma FGF21 and decreased hepatic Cyp7a1 levels. Hepatic expression levels of Fibroblast growth factor receptor 1 (Fgfr1), Fgfr4, Farnesoid X-activated receptor (Fxr), and Small heterodimer partner (Shp) and plasma FGF15/FGF19 levels did not differ with alcohol challenge. Exogenous FGF21 treatment suppressed Cyp7a1 in a dose-dependent manner in vitro. AALD patients showed markedly higher FGF21 and lower 7α-OHC plasma levels while FGF19 did not differ. Conclusions: The simultaneous upregulation of FGF21 and downregulation of Cyp7a1 expressions upon chronic plus binge alcohol feeding together with the invariant plasma FGF15 and hepatic Shp and Fxr levels suggest the presence of a direct regulatory mechanism of FGF21 on bile acid homeostasis through inhibition of CYP7A1 by an FGF15-independent pathway in this ACLI model. Lay Summary: Alcohol challenge results in the upregulation of FGF21 and repression of Cyp7a1 expressions while circulating FGF15 and hepatic Shp and Fxr levels remain constant both in healthy and pre-injured livers, suggesting the presence of an alternative FGF15-independent regulatory mechanism of FGF21 on bile acid homeostasis through the inhibition of Cyp7a1. 相似文献
30.
Che-Jui Yeh Chiao-Chu Ku Wei-Chen Lin Chiao-Yuan Fan Prof. Dr. Medel Manuel L. Zulueta Dr. Yoshiyuki Manabe Prof. Dr. Koichi Fukase Prof. Dr. Yaw-Kuen Li Prof. Dr. Shang-Cheng Hung 《Chembiochem : a European journal of chemical biology》2019,20(2):237-240
Many circulating cancer-related proteins, such as fibroblast growth factors (FGFs), associate with glycosaminoglycans—particularly heparan sulfate—at the cell surface. Disaccharide analogues of heparan sulfate had previously been identified as the shortest components out of the sugars that bind to FGF-1 and FGF-2. Taking note of the typical pose of l -iduronic acid, we conceived of per-O-sulfonated analogues of such disaccharides, and devised a single-step procedure for per-O-sulfonation of unprotected sugars with concomitant 1,6-anhydro bridge formation to achieve such compounds through direct use of SO3 ⋅ Et3N as sulfonation reagent and dimethylformamide as solvent. The synthesized sugars based on the oligomaltose backbone bound FGF-1 and FGF-2 mostly at the sub-micromolar level, although the tetrasaccharide analogue achieved low-nanomolar binding with FGF-2. 相似文献