全文获取类型
收费全文 | 283篇 |
免费 | 12篇 |
出版年
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 7篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2015年 | 7篇 |
2014年 | 12篇 |
2013年 | 22篇 |
2012年 | 7篇 |
2011年 | 7篇 |
2009年 | 6篇 |
2008年 | 11篇 |
2007年 | 4篇 |
2006年 | 6篇 |
2005年 | 3篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 7篇 |
2001年 | 6篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1992年 | 3篇 |
1989年 | 4篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1968年 | 4篇 |
1967年 | 4篇 |
1960年 | 4篇 |
1957年 | 3篇 |
1953年 | 3篇 |
1940年 | 2篇 |
1938年 | 4篇 |
1937年 | 2篇 |
1936年 | 9篇 |
1935年 | 5篇 |
1934年 | 2篇 |
1933年 | 8篇 |
1932年 | 9篇 |
1931年 | 9篇 |
1930年 | 2篇 |
1929年 | 7篇 |
1924年 | 2篇 |
1923年 | 3篇 |
1920年 | 2篇 |
1918年 | 3篇 |
1910年 | 2篇 |
1898年 | 2篇 |
排序方式: 共有295条查询结果,搜索用时 171 毫秒
111.
112.
113.
114.
115.
Ascorbate synthesis and ascorbate peroxidase activity during the early stage of wheat germination 总被引:8,自引:0,他引:8
Embryos from dry caryopses of wheat ( Triticum durum L. cv. Norba) are completely devoid of ascorbate (ASC) but contain a low amount of dehydroascorbate (DHA). The de novo biosynthesis of ASC starts in the wheat embryos after 8–10 h of germination but before the ASC biosynthetic pathway is completely restored the embryos can provide themselves with ASC by the reduction of the stored DHA. Three different proteins having DHA-reducing capability are present in the embryos during the early stages of germination. However, when the de novo ASC biosynthesis from sugar is completely restored, the DHA reduction capability largely drops and only one DHA-reducing protein remains active. The presence of three proteins having DHA-reducing capability and their behaviour during germination is discussed.
Dry embryos are also devoid of ASC peroxidase (EC 1.11.1.11); this hydrogen peroxide scavenger enzyme appears after the same lag as ASC and increases during germination in parallel with the rise in ASC. When ASC biosynthesis is experimentally induced, the ASC peroxidase also appears earlier; moreover the affinities for ASC of the three ASC peroxidase isoenzymes that progressively appear during germination depend on the ASC available in the embryos: highest in the first isoenzyme, that appears when the ASC content is very low, lowest in the isoenzyme that is expressed last, when the ASC content is 10–11 times higher. 相似文献
Dry embryos are also devoid of ASC peroxidase (EC 1.11.1.11); this hydrogen peroxide scavenger enzyme appears after the same lag as ASC and increases during germination in parallel with the rise in ASC. When ASC biosynthesis is experimentally induced, the ASC peroxidase also appears earlier; moreover the affinities for ASC of the three ASC peroxidase isoenzymes that progressively appear during germination depend on the ASC available in the embryos: highest in the first isoenzyme, that appears when the ASC content is very low, lowest in the isoenzyme that is expressed last, when the ASC content is 10–11 times higher. 相似文献
116.
The cDNA cloning and molecular evolution of reptile and pigeon lactate dehydrogenase isozymes 总被引:1,自引:0,他引:1
The cDNAs encoding lactate dehydrogenase isozymes LDH-A (muscle) and LDH-B
(heart) from alligator and turtle and LDH-A, LDH-B, and LDH-C (testis) from
pigeon were cloned and sequenced. The evolutionary relationships among
vertebrate LDH isozymes were analyzed. Contrary to the traditional belief
that the turtle lineage branched off before the divergence between the
lizard/alligator and bird lineages, the turtle lineage was found to be
clustered with either the alligator lineage or the alligator-bird clade,
while the lizard lineage was found to have branched off before the
divergence between the alligator/turtle and bird lineages. The pigeon
testicular LDH-C isozyme was evidently duplicated from LDH-B (heart), so it
is not orthologous to the mammalian testicular LDH-C isozymes.
相似文献
117.
Loredana Vesci Patrizia Tobia Nerina Corsico Edoardo Arrigoni Martelli Arduino Arduini 《Journal of neurochemistry》1995,64(6):2783-2791
Abstract: In the present study, we investigated the existence of a binding site for l -carnitine in the rat brain. In crude synaptic membranes, l -[3H]carnitine bound with relatively high affinity (KD = 281 nM) and in a saturable manner to a finite number (apparent Bmax value = 7.3 pmol/mg of protein) of binding sites. Binding was reversible and dependent on protein concentration, pH, ionic strength, and temperature. Kinetic studies revealed a Koff of 0.018 min?1 and a Kon of 0.187 × 10?3 min?1 nM?1. Binding was highest in spinal cord, followed by medulla oblongata-pons ≥ corpus striatum ≥ cerebellum = cerebral cortex = hippocampus = hypothalamus = olfactory bulb. l -[3H]Carnitine binding was stereoselective for the l -isomers of carnitine, propionylcarnitine, and acetylcarnitine. The most potent inhibitor of l -[3H]carnitine binding was l -carnitine followed by propionyl-l -carnitine. Acetyl-l -carnitine and isobutyryl-l -carnitine showed an affinity ~500-fold lower than that obtained for l -carnitine. The precursor γ-butyrobetaine had negligible activity at 0.1 mM. l -Carnitine binding to rat crude synaptic membrane preparation was not inhibited by neurotransmitters (GABA, glycine, glutamate, aspartate, acetylcholine, dopamine, norepinephrine, epinephrine, 5-hydroxytryptamine, histamine) at a final concentration of 0.1 mM. In addition, the binding of these neuroactive compounds to their receptors was not influenced by the presence of 0.1 mMl -carnitine. Finally, a subcellular fractionation study showed that synaptic vesicles contained the highest density of l -carnitine membrane binding sites whereas l -carnitine palmitoyltransferase activity was undetectable, thus excluding the possibility of the presence of an active site for carnitine palmitoyltransferase. This finding indicated that the localization of the l -[3H]carnitine binding site should be essentially presynaptic. 相似文献
118.
119.
Romano Zerboni Mariangela Manfredi Paolo Campi Pier Virgilio Arrigoni 《Aerobiologia》1986,2(1-2):2-13
Summary The aim of our research work was to evaluate the results from our pollen count (p.c.) carried out at the Allergological Centre
of Nuovo Osp. San Giovanni di Dio in Florence, in the light of orogeographical, phytogeographical and meteorological data.
The highest p.c. was yielded by Graminaceae which appear in small quantities early in the year but increase considereably
starting from April. Oleaceae too showed high pollen concentration but over a shorter lenght of time. The p.c. for Compositae
and Urticaceae was lower. It should be noted that Cupressaceae yielded constantly high p.c. in February–March. Investigations
on the allergenic flora of the surroundings were carried out concentrically in order to find out the closest and the farthest
sources of pollen production. The species investigated come under 7 types of vegetation: xerophilous woods, mesophilous woods,
conifers woods, parks and gardens, rural areas, meadows, border areas-weeds. A phytosociological study of the types of vegetation
has made it possible to evaluate the single species quantitatively. The different sources of pollen production can be spotted
by mapping these types of vegetation. The seasonal characterization of pollen production is better defined by means of periodical
phenological checking of the existing allergenic flora along carefully planned routes through the areas next to the sampling
station.
相似文献
120.
Cultures of 12 South African isolates of an undescribedFusarium species resembling but distinct fromF camptoceras were analysed for the presence of diacetoxyscirpenol (DAS), neosolaniol monoacetate (NMA), and T-2 toxin, by capillary gas chromatography utilizing electron capture detection. No DAS or T-2 toxin could be detected in any of the cultures of the isolates. NMA was, however, detected in 10 of the 12 isolates at levels ranging from 310 to 2060 ng/g. The method used, was primarily developed for the determination of DAS and T-2 toxin in fungal cultures and grain samples but was found to be suitable for the coextraction of NMA at an average recovery of 80.8%, with a detection limit in the order of 100 ng/g. Supportive evidence for the presence of the NMA was obtained by capillary gas chromatography / mass spectrometry. Regarded as a relatively rare trichothecene, NMA has never been reported to occur naturally and has previously been shown to be produced by only a fewFusarium strains. 相似文献