全文获取类型
收费全文 | 417篇 |
免费 | 32篇 |
国内免费 | 1篇 |
出版年
2022年 | 5篇 |
2021年 | 7篇 |
2020年 | 4篇 |
2019年 | 7篇 |
2018年 | 10篇 |
2017年 | 4篇 |
2016年 | 9篇 |
2015年 | 12篇 |
2014年 | 15篇 |
2013年 | 17篇 |
2012年 | 16篇 |
2011年 | 18篇 |
2010年 | 13篇 |
2009年 | 14篇 |
2008年 | 16篇 |
2007年 | 14篇 |
2006年 | 13篇 |
2005年 | 10篇 |
2004年 | 13篇 |
2003年 | 16篇 |
2002年 | 8篇 |
2001年 | 11篇 |
2000年 | 7篇 |
1999年 | 13篇 |
1998年 | 13篇 |
1997年 | 6篇 |
1995年 | 4篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1989年 | 4篇 |
1988年 | 7篇 |
1987年 | 3篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1978年 | 4篇 |
1974年 | 6篇 |
1973年 | 3篇 |
1970年 | 5篇 |
1969年 | 5篇 |
1966年 | 7篇 |
1963年 | 3篇 |
1960年 | 4篇 |
1955年 | 3篇 |
1949年 | 4篇 |
1948年 | 3篇 |
1946年 | 4篇 |
1940年 | 3篇 |
1939年 | 3篇 |
1936年 | 4篇 |
1935年 | 3篇 |
排序方式: 共有450条查询结果,搜索用时 531 毫秒
1.
W. Melville Arnott 《BMJ (Clinical research ed.)》1953,1(4821):1219-1220
2.
Stanley Melville 《BMJ (Clinical research ed.)》1932,2(3736):283-284
3.
4.
Structural aspects of Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] tuberculate ectomycorrhizae
H. B. Massicotte L. H. Melville C. Y. Li R. L. Peterson 《Trees - Structure and Function》1992,6(3):137-146
Summary Tubercles of Pseudotsuga menziesii consisted of clusters of ectomycorrhizae surrounded by a peridiumlike rind. Energy dispersive spectroscopy demonstrated that crystals found in the zone of loose hyphae extending from the inner rind to the mantle of each root probably contain calcium oxalate. Inner mantle and Hartig net hyphae showed a labyrinthine branching pattern and stored carbohydrates and protein. The Hartig net formed up to inner cortical cells which had thickened, darkly stained walls. Bacteria were located either along with hyphae within the rind or as colonies on the surface of the tubercle. 相似文献
5.
Regulation of carbon flow in Selenomonas ruminantium grown in glucose-limited continuous culture. 总被引:5,自引:3,他引:2
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We have applied a model that permits the estimation of the sensitivity of flux through branch point enzymes (D. C. LaPorte, K. Walsh, and D. E. Koshland, J. Biol. Chem. 259:14068-14075, 1984) in order to analyze the control of flux through the lactate-acetate branch point of Selenomonas ruminantium grown in glucose-limited continuous culture. At this branch point, pyruvate is the substrate of both the NAD-dependent L-(+)-lactate dehydrogenase (LDH) and the pyruvate:ferredoxin oxidoreductase (PFOR). The LDH was purified, and it exhibited positive cooperativity for the binding of pyruvate. The LDH had an [S].5 for pyruvate of 0.43 mM, a Hill coefficient of 2.4, and a K' equal to 0.13 mM. The PFOR, assayed in cell extracts, exhibited Michaelis-Menten kinetics for pyruvate, with a Km of 0.49 mM. Carbon flux through the LDH and the PFOR increased 80-fold and 3-fold, respectively, as the dilution rate was increased from 0.07 to 0.52 h-1 in glucose-limited continuous culture. There was nearly a twofold increase, from 6.5 to 11.2 mumol min-1 mg of protein-1 in the specific activity (i.e., maximum velocity) of the LDH at dilution rates of 0.11 and 0.52 h-1, respectively. A flux equation was used to calculate the intracellular concentration of pyruvate; a fourfold increase in pyruvate, from 0.023 to 0.093 mM, was thereby predicted as the dilution rate was increased from 0.07 to 0.52 h-1. When these calculated values of intracellular pyruvate concentration were inserted into the flux equation, the predicted values of flux through the LDH and the PFOR were found to match closely the flux actually measured in the chemostat-grown cells. Thus, the 80-fold increase in flux through the LDH was due to a twofold increase in the maximum velocity of the LDH and a fourfold increase in the intracellular pyruvate concentration. In addition, the flux through the LDH exhibited ultrasensitivity to changes in both the maximum velocity of the LDH and the intracellular concentration of pyruvate. The flux through the PFOR exhibited ultrasensitivity to changes in the maximum velocity of the LDH and hyperbolic sensitivity to changes in the intracellular concentration of pyruvate. 相似文献
6.
By encapsulating a pH-sensitive dye, phenol red, in multilamellar liposomes of DMPC, DPPC and DMPC/DPPC mixtures, the permeability of these phospholipid bilayers to dye as a function of temperature has been studied. For both DMPC and DPPC liposomes, dye release begins well below the main gel-to-liquid-crystalline phase transition (24°C and 42°C, respectively) at temperatures corresponding to the onset of the pretransition (about 14°C and 36°C, respectively) with DPPC liposomes exhibiting a permeability anomaly at the main phase transition (42°C). The perturbation occurring in the bilayer structure that allows the release of encapsulated phenol red (approx. 5 Å diameter) is not sufficient to permit the release of encapsulated haemoglobin (approx. 20 Å diameter, negatively charged). In liposomes composed of a range of DMPC/DPPC mixtures, dye release commences at the onset of the pretransition range (determined by optical absorbance measurements) and increases with increasing temperature until the first appearance of liquid crystalline phase after which no further dye release occurs. Interestingly, the dye retaining properties of DMPC and DPPC liposomes well below their respective pretransition temperature regions are very different: DMPC liposomes release much encapsulated dye at incubation temperatures of 5°C whilst DPPC liposomes do not. 相似文献
7.
8.
9.
Direct sequencing of the mitochondrial displacement loop (D-loop) of shrews
(genus Sorex) for the region between the tRNA(Pro) and the conserved
sequence block-F revealed variable numbers of 79-bp tandem repeats. These
repeats were found in all 19 individuals sequenced, representing three
subspecies and one closely related species of the masked shrew group (Sorex
cinereus cinereus, S. c. miscix, S. c. acadicus, and S. haydeni) and an
outgroup, the pygmy shrew (S. hoyi). Each specimen also possessed an
adjacent 76-bp imperfect copy of the tandem repeats. One individual was
heteroplasmic for length variants consisting of five and seven copies of
the 79-bp tandem repeat. The sequence of the repeats is conducive to the
formation of secondary structure. A termination-associated sequence is
present in each of the repeats and in a unique sequence region 5' to the
tandem array as well. Mean genetic distance between the masked shrew taxa
and the pygmy shrew was calculated separately for the unique sequence
region, one of the tandem repeats, the imperfect repeat, and these three
regions combined. The unique sequence region evolved more rapidly than the
tandem repeats or the imperfect repeat. The small genetic distance between
pairs of tandem repeats within an individual is consistent with a model of
concerted evolution. Repeats are apparently duplicated and lost at a high
rate, which tends to homogenize the tandem array. The rate of D- loop
sequence divergence between the masked and pygmy shrews is estimated to be
15%-20%/Myr, the highest rate observed in D-loops of mammals. Rapid
sequence evolution in shrews may be due either to their high metabolic rate
and short generation time or to the presence of variable numbers of tandem
repeats.
相似文献
10.