全文获取类型
收费全文 | 150篇 |
免费 | 13篇 |
国内免费 | 2篇 |
出版年
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 5篇 |
2014年 | 3篇 |
2013年 | 11篇 |
2012年 | 15篇 |
2011年 | 11篇 |
2010年 | 4篇 |
2009年 | 6篇 |
2008年 | 6篇 |
2007年 | 4篇 |
2006年 | 5篇 |
2005年 | 6篇 |
2004年 | 8篇 |
2003年 | 14篇 |
2002年 | 6篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1966年 | 1篇 |
1964年 | 1篇 |
1962年 | 2篇 |
1961年 | 1篇 |
1958年 | 1篇 |
1957年 | 1篇 |
1937年 | 1篇 |
1935年 | 5篇 |
1931年 | 1篇 |
排序方式: 共有165条查询结果,搜索用时 31 毫秒
61.
Joost Lücker Mazen K El Tamer Wilfried Schwab Francel W A Verstappen Linus H W van der Plas Harro J Bouwmeester Harrie A Verhoeven 《European journal of biochemistry》2002,269(13):3160-3171
Citrus limon possesses a high content and large variety of monoterpenoids, especially in the glands of the fruit flavedo. The genes responsible for the production of these monoterpenes have never been isolated. By applying a random sequencing approach to a cDNA library from mRNA isolated from the peel of young developing fruit, four monoterpene synthase cDNAs were isolated that appear to be new members of the previously reported tpsb family. Based on sequence homology and phylogenetic analysis, these sequences cluster in two separate groups. All four cDNAs could be functionally expressed in Escherichia coli after removal of their plastid targeting signals. The main products of the enzymes in assays with geranyl diphosphate as substrate were (+)-limonene (two cDNAs) (-)-beta-pinene and gamma-terpinene. All enzymes exhibited a pH optimum around 7; addition of Mn(2+) as bivalent metal ion cofactor resulted in higher activity than Mg(2+), with an optimum concentration of 0.6 mm. K(m) values ranged from 0.7 to 3.1 microm. The four enzymes account for the production of 10 out of the 17 monoterpene skeletons commonly observed in lemon peel oil, corresponding to more than 90% of the main components present. 相似文献
62.
Specificity of deoxyribonucleic acid transmethylase induced by bacteriophage T2. I. Nucleotide sequences isolated from tmicrococcus luteus DNA methylated in vitro. 总被引:5,自引:2,他引:3 下载免费PDF全文
(Deoxyribonucleic acid from Micrococcus luteus was methylated in vitro in the presence of S-adenosyl-(14C methyl)methionine with a DNA methyltransferase purified from extracts of te. coli infected with bacteriophage T2. The labelled DNA was degraded by enzymatic and specific chemical methods and the resulting short oligonucleotides were separated and characterized. tthe analytical data permit the conclusion that the tdna transmethylase reacts specifically with N-G-A-T-C-N sequences in which it converts adenine to a 6-methyl-aminopurine residue. 相似文献
63.
The energetics of early platelet responses. Energy consumption during shape change and aggregation with special reference to protein phosphorylation and the polyphosphoinositide cycle. 总被引:3,自引:3,他引:0 下载免费PDF全文
Among the different platelet responses, secretion requires the greatest amount of metabolic energy. The velocities of dense, alpha- and acid hydrolase granule secretion vary in parallel with the increase in energy consumption seen in thrombin-stimulated cells. This covariance is preceded by a phase in which energy consumption is increased without the extracellular appearance of secretion markers. By treating the platelets with thrombin and hirudin we have stimulated the platelets for short intervals and succeeded in separating shape change, single platelet disappearance and secretion to a great extent. In this report we show that the early increase in energy consumption reflects the energy requirement of aggregation but not of shape change. The cost of 100% of single platelet disappearance is 2.8 mumol of ATPeq. X (10(11) platelets)-1. Concurrent analysis of phosphorylation of Mr 20 000 and 47 000 proteins and of 32P-labelled phosphatidylinositol metabolites led to the following observations. Firstly, shape change is neither accompanied by an increase in protein phosphorylation nor by changes in the steady state levels of 32P-labelled phosphatidylinositol metabolites. Secondly, when aggregation occurs both proteins are phosphorylated, but the phosphatidylinositol metabolites do not change. Thirdly, when secretion follows, more phosphorylation of the Mr 47 000 protein occurs and initially only phosphatidic acid accumulates. At a later stage of the secretion responses, more protein phosphorylation and phosphatidic acid accumulation become evident, and are now accompanied by alterations in the steady state levels of 32P-labelled (poly)phosphoinositides. Hence, the early increase in energy consumption coincides with protein phosphorylation and, at a later stage, with alterations in (poly)phosphoinositides metabolites. This demonstrates that metabolic energy is directly involved in stimulus-response coupling in aggregating platelets. 相似文献
64.
65.
Influence of Mg2 总被引:1,自引:0,他引:1
66.
67.
Gustafsson BI Westbroek I Waarsing JH Waldum H Solligård E Brunsvik A Dimmen S van Leeuwen JP Weinans H Syversen U 《Journal of cellular biochemistry》2006,97(6):1283-1291
New evidence suggests a control of bone mass by the central nervous system. We have previously shown that functional serotonin receptors are present in bone cells and that serotonin stimulates proliferation of osteoblast precursor cells in vitro. In the present study we investigated the effects of serotonin on bone tissue in vivo. Ten, 2-month-old female Sprague-Dawley rats were injected with serotonin subcutaneously (s.c.) (5 mg/kg) once daily for 3 months, controls received saline. Using microdialysis and HPLC, free circulating serotonin levels were measured. DXA scans were made after 3 months of serotonin administration. Bone architecture and mechanical properties were investigated by micro-computed tomography (microCT), histomorphometry, and mechanical testing. A long-lasting hyperserotoninemia with a >10-fold increase in serotonin appeared. Total body BMD was significantly higher (0.1976+/-0.0015 vs. 0.1913+/-0.0012 g/cm2) in rats receiving serotonin. Cortical thickness (Ct.Th) measured by microCT analysis was also higher, whereas trabecular bone volume (BV) was lower. Interestingly, the perimeter and cross-sectional moment of inertia (MOI), a proxy for geometrical bone strength, were the same in both groups. These data suggest that serotonin reduces resorption or/and increases apposition of endosteal bone. Mechanical testing showed that femoral stiffness was higher in serotonin-dosed animals. The energy absorption also seemed slightly, but not significantly higher. In conclusion, hyperserotoninemia led to a higher BMD, altered bone architecture and higher femural bone stiffness in growing rats, demonstrating that serotonin may have important effects on bone in vivo. 相似文献
68.
Carola Krause Olexandr Korchynskyi Karien de Rooij Stella E. Weidauer David J. J. de Gorter Rutger L. van Bezooijen Sarah Hatsell Aris N. Economides Thomas D. Mueller Clemens W. G. M. L?wik Peter ten Dijke 《The Journal of biological chemistry》2010,285(53):41614-41626
Sclerostin is expressed by osteocytes and has catabolic effects on bone. It has been shown to antagonize bone morphogenetic protein (BMP) and/or Wnt activity, although at present the underlying mechanisms are unclear. Consistent with previous findings, Sclerostin opposed direct Wnt3a-induced but not direct BMP7-induced responses when both ligand and antagonist were provided exogenously to cells. However, we found that when both proteins are expressed in the same cell, sclerostin can antagonize BMP signaling directly by inhibiting BMP7 secretion. Sclerostin interacts with both the BMP7 mature domain and pro-domain, leading to intracellular retention and proteasomal degradation of BMP7. Analysis of sclerostin knock-out mice revealed an inhibitory action of sclerostin on Wnt signaling in both osteoblasts and osteocytes in cortical and cancellous bones. BMP7 signaling was predominantly inhibited by sclerostin in osteocytes of the calcaneus and the cortical bone of the tibia. Our results suggest that sclerostin exerts its potent bone catabolic effects by antagonizing Wnt signaling in a paracrine and autocrine manner and antagonizing BMP signaling selectively in the osteocytes that synthesize simultaneously both sclerostin and BMP7 proteins. 相似文献
69.
Harjeevan Kaur Lihong Wang Natalia Stawniak Raymond Sloan Harrie van Erp Peter Eastmond Ian Bancroft 《Plant biotechnology journal》2020,18(4):983-991
Oilseed rape (Brassica napus) is the third largest source of vegetable oil globally. In addition to food uses, there are industrial applications that exploit the ability of the species to accumulate the very‐long‐chain fatty acid (VLCFA) erucic acid in its seed oil, controlled by orthologues of FATTY ACID ELONGASE 1 (Bna.FAE1.A8 and Bna.FAE1.C3). The proportion of polyunsaturated fatty acids (PUFAs) in rapeseed oil is predicted to affect its thermal stability and is controlled by orthologues of FATTY ACID DESATURASE 2, particularly Bna.FAD2.C5. Our aim was to develop rapeseed lines combining high erucic and low PUFA characters and to assess the impact on thermal stability of the oil they produce. The new type of rapeseed oil (high erucic low polyunsaturate; HELP) contained a substantially greater proportion of erucic acid (54%) compared with high erucic rapeseed oil (46%). Although the total VLCFA content was greater in oil from HELP lines (64%) than from high erucic rapeseed (57%), analysis of triacylglycerol composition showed negligible incorporation of VLCFAs into the sn‐2 position. Rancimat analysis showed that the thermal stability of rapeseed oil was improved greatly as a consequence of reduction of PUFA content, from 3.8 and 4.2 h in conventional low erucic and high erucic rapeseed oils, respectively, to 11.3 and 16.4 h in high oleic low PUFA (HOLP) and HELP oils, respectively. Our results demonstrate that engineering of the lipid biosynthetic pathway of rapeseed, using traditional approaches, enables the production of renewable industrial oils with novel composition and properties. 相似文献
70.
C. den Engelsen K.J. Gorter P.L. Salomé G.E. Rutten 《Obesity (Silver Spring, Md.)》2013,21(5):1025-1030