全文获取类型
收费全文 | 257篇 |
免费 | 16篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 5篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 2篇 |
2017年 | 6篇 |
2016年 | 5篇 |
2015年 | 6篇 |
2014年 | 6篇 |
2013年 | 9篇 |
2012年 | 11篇 |
2011年 | 8篇 |
2010年 | 2篇 |
2009年 | 9篇 |
2008年 | 12篇 |
2007年 | 8篇 |
2006年 | 10篇 |
2005年 | 11篇 |
2004年 | 12篇 |
2003年 | 19篇 |
2002年 | 9篇 |
2001年 | 8篇 |
2000年 | 10篇 |
1999年 | 12篇 |
1998年 | 13篇 |
1997年 | 5篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1970年 | 2篇 |
1968年 | 1篇 |
排序方式: 共有273条查询结果,搜索用时 15 毫秒
1.
P. Pellerin B. Gruson G. Prensier G. Albagnac P. Debeire 《Archives of microbiology》1987,146(4):377-381
An intracellular glycogen was purified and characterized from the acetoclastic bacteria Methanothrix str. FE, its average chain length was about 13 glucose residues. Acetyl-CoA was shown to be synthesized by the action of acetate thiokinase; in addition pyruvate synthase, phosphoenolpyruvate synthetase and enzymes of gluconeogenesis were detected in cell extracts. For glycogen synthase activity, both adenosine diphosphate glucose and uridine diphosphate glucose were used as glycosyl donors, apparent K
m were, respectively, 8 M for ADPGlc and 625 M for UDPGLe, at the opposite the V
m were the same for both precursors. This was in accordance with competition experiments and strongly suggested that only one glucosyl transferase was involved and that ADPGlc was the physiological glycosyl donor in Methanothrix str. FE. In addition branching enzyme activity (1-4-glucan-6-glucosyl transferase) was detected in cell extracts.Abbreviations ADPGlc
adenosine diphosphate glucose
- UDPGlc
uridine diphosphate glucose 相似文献
2.
Pellerin Sylvain 《Plant and Soil》1993,148(2):155-161
The timing of root production is one of the parameters required for modelling the root system architecture. The objectives of this study are (1) to describe the rate of appearance of adventitious root primordia of maize and their rate of emergence out of the stem; (2) to test equations for the prediction of the rank of the phytomer on which root emergence occurs, in a wide range of field situations.Maize, cultivar Dea, was grown in controlled conditions and in the field in 1987, 1988, 1989 and 1991. Plants were regularly sampled and the following data were recorded: foliar stage, number of root primordia and number of emerged roots per phytomer. Root primordia were counted in transverse thin sections in the stem.At a single plant level, root primordia differentiation occurred sequentially on the successive phytomers, with no overlapping between two phytomers. The same was true for root emergence. Roots belonging to the same phytomer emerged at approximately the same time.At a plant population level, there was a linear relationship between the rank of the phytomer on which root primordia were differentiated and cumulated degree-days after sowing. A linear relationship was also observed between the rank of the phytomer on which roots were emerging and cumulated degree-days or foliar stage. In the range of field situations tested (several years, sowing dates and planting densities), both equations gave an accurate prediction of the timing of root emergence during the plant cycle. 相似文献
3.
4.
Litman GW; Rast JP; Shamblott MJ; Haire RN; Hulst M; Roess W; Litman RT; Hinds- Frey KR; Zilch A; Amemiya CT 《Molecular biology and evolution》1993,10(1):60-72
Immunoglobulins are encoded by a large multigene system that undergoes
somatic rearrangement and additional genetic change during the development
of immunoglobulin-producing cells. Inducible antibody and antibody-like
responses are found in all vertebrates. However, immunoglobulin possessing
disulfide-bonded heavy and light chains and domain-type organization has
been described only in representatives of the jawed vertebrates. High
degrees of nucleotide and predicted amino acid sequence identity are
evident when the segmental elements that constitute the immunoglobulin gene
loci in phylogenetically divergent vertebrates are compared. However, the
organization of gene loci and the manner in which the independent elements
recombine (and diversify) vary markedly among different taxa. One striking
pattern of gene organization is the "cluster type" that appears to be
restricted to the chondrichthyes (cartilaginous fishes) and limits
segmental rearrangement to closely linked elements. This type of gene
organization is associated with both heavy- and light-chain gene loci. In
some cases, the clusters are "joined" or "partially joined" in the germ
line, in effect predetermining or partially predetermining, respectively,
the encoded specificities (the assumption being that these are expressed)
of the individual loci. By relating the sequences of transcribed gene
products to their respective germ-line genes, it is evident that, in some
cases, joined-type genes are expressed. This raises a question about the
existence and/or nature of allelic exclusion in these species. The
extensive variation in gene organization found throughout the vertebrate
species may relate directly to the role of intersegmental
(V<==>D<==>J) distances in the commitment of the individual
antibody-producing cell to a particular genetic specificity. Thus, the
evolution of this locus, perhaps more so than that of others, may reflect
the interrelationships between genetic organization and function.
相似文献
5.
Abstract: The excitatory amino acid glutamate was previously shown to stimulate aerobic glycolysis in astrocytes by a mechanism involving its uptake through an Na+ -dependent transporter. Evidence had been provided that Na+ ,K+ -ATPase might be involved in this process. We have now measured the activity of Na+ ,K+ -ATPase in cultured astrocytes, using ouabain-sensitive 86 Rb uptake as an index. l -Glutamate increases glial Na+ ,K+ -ATPase activity in a concentration-dependent manner with an EC50 = 67 µ M . Both l - and d -aspartate, but not d -glutamate, produce a similar response, an observation that is consistent with an uptake-related effect rather than a receptor-mediated one. Under basal conditions, concentration-dependent inhibition of Na+ ,K+ -ATPase activity in astrocytes by ouabain indicates the presence of a single catalytic site with a low affinity for ouabain ( K 0.5 = 113 µ M ), compatible with the presence of an α1 isozyme. On stimulation with glutamate, however, most of the increased activity is inhibited by low concentrations of ouabain ( K 0.5 = 20 n M ), thus revealing a high-affinity site akin to the α2 isozyme. These results suggest that astrocytes possess a glutamate-sensitive isoform of Na+ ,K+ -ATPase that can be mobilized in response to increased neuronal activity. 相似文献
6.
7.
The effect of mutual shading on the root/shoot ratio and on the number of nodal roots of maize was studied. Plants of two varieties (Dea and LG2281) were grown in individual pots of 9 L, at three plant densities: 7.5, 11 and 15 plants m–2. A control experiment was carried out in order to study if root growth was affected by the small size of the pots. Maize plants (cv Dea) were grown at a low plant density (7.5 plants m–2) in pots of two different volumes (9 and 25 L respectively). In both experiments plants were watered every two hours with a nutrient solution. Some plants were sampled at five dates in the main experiment and the following data were recorded: foliar stage; root, stem and leaf dry weight; number of root primordia and number of emerged roots per phytomer. The final sampling date occurred at silking.Results of the control experiment showed that the root biomass was lower in small pots but the number of nodal roots per phytomer was not affected.Results of the main experiment showed that the total plant biomass and the root/shoot ratio were lower at high plant density. The number of emerged roots was strongly reduced on the upper phytomer (P8). This reduction was mainly due to a lower percentage of root primordia which elongated. A proposed interpretation is that the number of roots which emerge on upper phytomers is controlled by carbohydrate availability. 相似文献
8.
Olivier Véron Jean-Philippe Blondeau Michał Grabiec Aleksandra Wolak Krzystof Dzierżęga Nadège Ollier François Goutaland Mohamed Chérif Sow Stéphane Pellerin Nadia Pellerin 《Plasmonics (Norwell, Mass.)》2013,8(1):93-103
Silver-exchanged silicate glass has been irradiated by 532-nm pulsed Nd:YAG laser in order to locally form metallic nanoparticles. The particular interest of this process is to locally control the silver nanoparticles (NPs) growth. Silver ions are exchanged with sodium ions near the glass surface after dumping of a silicate glass few minutes in silver and sodium nitrates molten salt. A low-energy density laser exposure (0.239 J/cm2) chosen at the ablation threshold allows to observe the kinetics of the silver NPs growth according to the increasing shots number. An on-line optical measurement is carried out after each shot to identify the most important steps during the irradiation process. According to this measurement, we have determined four steps highlighted by UV/Visible spectrophotometry and we have identified the influence of located surface plasmon resonance. Three combined material analysis methods were used to understand the glass/laser interaction mechanism: we outlined the material volume variations by profilometric method, the element distribution by scanning electron microscopy and finally the structural distribution of the irradiated region by a local infrared investigation. The trend for NPs formation revealed by the UV/Visible spectrophotometry is thus explained by the formation of a ring expelled from a central hole. We highlight that the on-line extinction measurement can be used to data process the NPs evolution. 相似文献
9.