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   163篇
  免费   10篇
  173篇
  2022年   2篇
  2021年   5篇
  2019年   3篇
  2018年   2篇
  2016年   2篇
  2015年   3篇
  2013年   6篇
  2012年   8篇
  2011年   15篇
  2010年   5篇
  2009年   5篇
  2008年   7篇
  2007年   5篇
  2006年   2篇
  2005年   3篇
  2004年   3篇
  2003年   5篇
  2002年   9篇
  2001年   4篇
  2000年   2篇
  1999年   2篇
  1998年   1篇
  1996年   1篇
  1995年   1篇
  1994年   3篇
  1993年   4篇
  1992年   1篇
  1991年   2篇
  1990年   4篇
  1989年   3篇
  1987年   4篇
  1986年   4篇
  1985年   2篇
  1984年   8篇
  1983年   2篇
  1982年   2篇
  1981年   1篇
  1980年   3篇
  1979年   1篇
  1978年   2篇
  1974年   4篇
  1973年   4篇
  1971年   1篇
  1970年   3篇
  1969年   2篇
  1968年   4篇
  1965年   1篇
  1964年   2篇
  1934年   1篇
  1932年   1篇
排序方式: 共有173条查询结果,搜索用时 0 毫秒
81.
82.
The main strategy of family planning program in many over populated countries like India, China etc. is to bring down fertility by propagating various family planning devices like Tubectomy, IUD, Vasectomy, conventional contraceptives etc. Data was collected on various socio-economic and demographic characteristics of the users of these devices. Based on it we have developed a discriminant function for these devices using the methodology given by Kumar (1983).  相似文献   
83.
84.
The execution phase of apoptosis is characterized by marked changes in cell morphology that include contraction and membrane blebbing. The actin-myosin system has been proposed to be the source of contractile force that drives bleb formation, although the biochemical pathway that promotes actin-myosin contractility during apoptosis has not been identified. Here we show that the Rho effector protein ROCK I, which contributes to phosphorylation of myosin light-chains, myosin ATPase activity and coupling of actin-myosin filaments to the plasma membrane, is cleaved during apoptosis to generate a truncated active form. The activity of ROCK proteins is both necessary and sufficient for formation of membrane blebs and for re-localization of fragmented DNA into blebs and apoptotic bodies.  相似文献   
85.
The molecular mechanism(s) by which high glucose induces fibronectin expression via G-protein activation in the kidney are largely unknown. This investigation describes the effect of high glucose (HG) on a small GTP-binding protein, Rap1b, expression and activation, and the relevance of protein kinase C (PKC) and Raf pathways in fibronectin synthesis in cultured renal glomerular mesangial cells (MCs). In vivo experiments revealed a dose-dependent increase in Rap1b expression in glomeruli of diabetic rat kidneys. Similarly, in vitro exposure of MCs to HG led to an up-regulation of Rap1b with concomitant increase in fibronectin (FN) mRNA and protein expression. The up-regulation of Rap1b mRNA was mitigated by the PKC inhibitors, calphostin C, and bisindolymaleimide, while also reducing HG- induced FN expression in non-transfected MCs. Overexpression of Rap1b by transfection with pcDNA 3.1/Rap1b in MCs resulted in the stimulation of FN synthesis; however, the PKC inhibitors had no significant effect in reducing FN expression in Rap1b-transfected MCs. Transfection of Rap1b mutants S17N (Ser --> Asn) or T61R (Thr --> Arg) in MCs inhibited the HG-induced increased FN synthesis. B-Raf and Raf-1 expression was investigated to assess whether Rap1b effects are mediated via the Raf pathway. B-Raf, and not Raf-1, expression was increased in MCs transfected with Rap1b. HG also caused activation of Rap1b, which was largely unaffected by anti-platelet-derived growth factor (PDGF) antibodies. HG-induced activation of Rap1b was specific, since Rap2b activation and expression of Rap2a and Rap2b were unaffected by HG. These findings indicate that hyperglycemia and HG cause an activation and up-regulation of Rap1b in renal glomeruli and in cultured MCs, which then stimulates FN synthesis. This effect appears to be PKC-dependent and PDGF-independent, but involves B-Raf, suggesting a novel PKC-Rap1b-B-Raf pathway responsible for HG-induced increased mesangial matrix synthesis, a hallmark of diabetic nephropathy.  相似文献   
86.
Present study reports a high frequency regeneration system for in vitro propagation and conservation of an important and threatened medicinal herb Coleus forskohlii (Briq.). Shoot multiplication has been achieved through axillary bud development and direct adventitious shoot formation in nodal explants on Murashige and Skoog (MS) medium containing 6-benzyladenine (BA) (5 μM). Further shoot multiplication was recorded up to third subculture on MS medium containing BA (5 μM) in combination with 1-naphthleneacetic acid (NAA) (0.1 μM). Excised microshoots on transfer to root induction medium consisting of half-strength MS medium (1/2 MS) alone as well as in combination with various auxins, resulted in varied rooting pattern in terms of number, length, and type of roots. Rooted microshoots were acclimatized successfully in earthen pots containing garden manure, garden soil, and sand (1:2:1) as potting mix with survival rate of 70 %. Acclimatized plantlets were studied for the amount of chlorophyll and carotenoid content as well as the net photosynthetic rate (PN) during subsequent weeks of transfer to ex vitro condition. Histological studies revealed the direct origin and development of shoot buds from basal swollen cut end of nodal explants.  相似文献   
87.
The effect of addition of autoclaved and filter-sterilized culture filtrate of Piriformospora indica (a root endophytic fungus) to the growing Linum album hairy root cultures on growth and lignan production was investigated. The addition resulted in a significant enhancement in lignan production and growth. The podophyllotoxin and 6-methoxypodophyllotoxin (the lignans) concentrations were maximally improved by 3.8 times (233.8 mg/L) and 4.4 times (131.9 mg/L) in comparison to control cultures, respectively, upon addition of 3.0% (v/v) filter-sterilized culture filtrate of P. indica to the hairy root cultures of L. album for exposure time of 48 h. This increase in the lignan content also coincided with the increase in phenylalanine ammonia lyase activity, which was 3.1-fold (371.4 μkat/kg protein) higher compared to control cultures under the same conditions. The maximal increase in hairy root biomass was, however, obtained under different conditions; it was enhanced by 1.4 times (21.8 g/L) in comparison to control cultures, when 2% (v/v) filter-sterilized culture filtrate was in contact with L. album cultures for 96 h.  相似文献   
88.
Studies on Protein Synthesis by Senescing and Kinetin-treated Barley Leaves   总被引:1,自引:0,他引:1  
Using sterile conditions, changes in total protein synthesis were followed. over an 8 day incubation period, in detached first seedling leaves of barley from 8 day old plants during senescence and after kinetin treatment. In senescing leaves, total 14C-alanine incorporation was enhanced by nearly 20% within 6 h of leaf detachment and by about 30 % after 24 h. Kinetin treatment stimulated protein synthesis even more, for total incorporation was promoted ca. 50 % after 6 h and by ca. 60 % after 24 h incubation. The leaf supernatant (30,000 ×g for 30 min) proteins were separated on DEAE-Sephadex (A-50) columns into approximately 14 fractions and changes in 14C labelling of these fractions were studied following leaf detachment and on incubation on water or kinetin for 6 days. In senescing leaves, 14C-incorporation into supernatant proteins was sustained, even as protein levels declined rapidly The varied stabilities of the different leaf proteins was suggested by the characteristically changing specific activities of the different protein fractions. Although kinetin greatly promoted incorporation into all protein fractions, no evidence was surmised of specific effects on individual leaf proteins. Studies of changes in total protein synthesis in attached senescing first seedling leaves taken from plants aged 7 to 27 days revealed a relatively small increase in 14C-incorporation. However, incorporation could be greatly increased in leaves up to 15 days old by detaching and preincubating such leaves for up to 2 days on water, prior to measurement. The promotion of 14C-incorporation into protcins follwing leaf excision could result from early changes in permeability and precursor pool size.  相似文献   
89.
The exponential substrate feeding (open-loop) and automated feedback substrate feeding (closed loop) strategies were developed to obtain high cell densities of fluorescent pseudomonad strains R62 and R81 and enhanced production of antifungal compound 2,4-diacetylphloroglucinol (DAPG) from glycerol as a sole carbon source. The exponential feeding strategy resulted in increased glycerol accumulation during the fed-batch cultivation when the predetermined specific growth rate (μ) was set at 0.10 or 0.20 h?1 (<μm = 0.29 h?1). Automated feeding strategies using dissolved oxygen (DO) or pH as feedback signals resulted in minimal to zero accumulation of glycerol for both the strains. In case of DO-based feeding strategy, biomass productivity of 0.24 g/(L h) and 0.29 g/(L h) was obtained for R62 and R81, respectively. Using pH-based feeding strategy, biomass productivity could be increased to a maximum of 0.51 and 0.54 g/(L h), for the strains R62 and R81, respectively, whereas the DAPG concentration was enhanced to 298 mg/L for R62 and 342 mg/L for R81 strains. These yields of DAPG are thus far the highest reported from GRAS organisms.  相似文献   
90.
Growth and maintenance parameters μmax, Ks, m, and Ym for cellulase biosynthesis on lactose by T. reesei-C5 were estimated and compared with published data on other soluble substrates and mutant strains of T. reesei in continuous culture. Growth was favored at higher feed lactose but cellulase productivities did not increase proportionally, suggesting that a degree of inhibition and/or catabolic repression within the strain is possible. The estimated values of growth kinetics and maintenance parameters varied little but were within a reasonable range of published data on other soluble substrates and mutant strains of T. reesei in continuous cultures.  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