全文获取类型
收费全文 | 385篇 |
免费 | 52篇 |
国内免费 | 4篇 |
出版年
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 15篇 |
2017年 | 3篇 |
2016年 | 12篇 |
2015年 | 26篇 |
2014年 | 20篇 |
2013年 | 16篇 |
2012年 | 14篇 |
2011年 | 19篇 |
2010年 | 9篇 |
2009年 | 12篇 |
2008年 | 17篇 |
2007年 | 13篇 |
2006年 | 14篇 |
2005年 | 8篇 |
2004年 | 16篇 |
2003年 | 10篇 |
2002年 | 13篇 |
2001年 | 8篇 |
2000年 | 11篇 |
1999年 | 9篇 |
1998年 | 10篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1994年 | 5篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1989年 | 4篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1983年 | 8篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 10篇 |
1975年 | 6篇 |
1974年 | 11篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1971年 | 8篇 |
1970年 | 3篇 |
1969年 | 4篇 |
1967年 | 5篇 |
1966年 | 4篇 |
1955年 | 3篇 |
排序方式: 共有441条查询结果,搜索用时 140 毫秒
1.
H Wodlinger H Kunov H L Atwood 《Canadian journal of physiology and pharmacology》1982,60(12):1541-1544
The measurement of the sodium reversal potential (Erev), as that potential where the early current reverses during voltage clamp, was found to exceed the true Erev by 4.1 +/- 2.4 mV (mean +/- SD) in squid giant axon. This error was found in both intact and internally perfused axons and is due to interference from the displacement current. This was shown by subtraction of the current records obtained before and after treatment with tetrodotoxin (TTX). The error in Erev is proportional to (Td/gNA)12 where Td is the time constant of the displacement current. 相似文献
2.
C N Fong H L Atwood K N Jeejeebhoy M P Charlton 《Canadian journal of physiology and pharmacology》1987,65(11):2188-2190
The effects of malnutrition on intracellular K+ activity, (alpha K)i, and membrane potential, Em, were measured by means of double-barrelled K+-selective microlectrodes in the soleus and gastrocnemius muscles of the rat. (alpha K)i and Em were measured in vivo in normal anaesthetized animals and in rats subjected to one of two diet restrictions: a 2-day fast or a long-term hypocaloric diet. In the soleus muscle, (alpha K)i fell by similar amounts in both 2-day fasted and long-term hypocalorically fed rats, while Em depolarized significantly only in hypocalorically fed rats. In the gastrocnemius muscle, neither the 2-day fast nor the hypocaloric diet affected (alpha K)i or Em. It is suggested that the selective loss of K+ from the soleus muscle may be related to its activity pattern. 相似文献
3.
B J Keats A A Todorov L D Atwood M Z Pelias J F Hejtmancik W J Kimberling M Leppert R A Lewis R J Smith 《Genomics》1992,14(3):707-714
Usher Syndrome Type 1 is an autosomal recessive disease characterized by profound congenital hearing impairement and vestibular dysfunction followed by the onset of retinitis pigmentosa in childhood or early adolescence. Members of the Usher Syndrome Consortium, whose objective is to locate and isolate the genes for Usher syndrome, have pooled linkage data from 36 families with 111 affected individuals. We report the analysis of 206 blood group, protein, and DNA marker polymorphisms. No evidence of linkage heterogeneity among families was found for any of the markers studied; the negative lod scores exclude the locus for this disease from about 39% of the genome. Our results indicate the regions of the genome to which our continuing efforts should be directed. 相似文献
4.
An experiment is described that provides evidence for an exchange mechanism to explain the increase in ribosomal gene number that occurs during bobbed magnification. We show that bobbed and bobbed-lethal alleles do not magnify in closed X chromosomes, but that a spontaneous ring opening restores normal magnification. The results provide strong evidence that the elementary magnifying event is unequal sister chromatid exchange, and can be interpreted in the framework of an inducible rDNA-specific recombination system as the basis of ribosomal gene magnification.
Correspondence to: S.A. Endow at the above address 相似文献
5.
Nielsen J; Peixoto AA; Piccin A; Costa R; Kyriacou CP; Chalmers D 《Molecular biology and evolution》1994,11(6):839-853
The region of the clock gene period (per) that encodes a repetitive tract
of threonine-glycine (Thr-Gly) pairs has been compared between Dipteran
species both within and outside the Drosophilidae. All the non-
Drosophilidae sequences in this region are short and present a remarkably
stable picture compared to the Drosophilidae, in which the region is much
larger and extremely variable, both in size and composition. The
accelerated evolution in the repetitive region of the Drosophilidae appears
to be mainly due to an expansion of two ancestral repeats, one encoding a
Thr-Gly dipeptide and the other a pentapeptide rich in serine, glycine, and
asparagine or threonine. In some drosophilids the expansion involves a
duplication of the pentapeptide sequence, but in Drosophila pseudoobscura
both the dipeptide and the pentapeptide repeats are present in larger
numbers. In the nondrosophilids, however, the pentapeptide sequence is
represented by one copy and the dipeptide by two copies. These observations
fulfill some of the predictions of recent theoretical models that have
simulated the evolution of repetitive sequences.
相似文献
6.
Evolutionary origin of human and primate malarias: evidence from the circumsporozoite protein gene 总被引:8,自引:1,他引:7
We have analyzed the conserved regions of the gene coding for the
circumsporozoite protein (CSP) in 12 species of Plasmodium, the malaria
parasite. The closest evolutionary relative of P. falciparum, the agent of
malignant human malaria, is P. reichenowi, a chimpanzee parasite. This is
consistent with the hypothesis that P. falciparum is an ancient human
parasite, associated with humans since the divergence of the hominids from
their closest hominoid relatives. Three other human Plasmodium species are
each genetically indistinguishable from species parasitic to nonhuman
primates; that is, for the DNA sequences included in our analysis, the
differences between species are not greater than the differences between
strains of the human species. The human P. malariae is indistinguishable
from P. brasilianum, and P. vivax is indistinguishable from P. simium; P.
brasilianum and P. simium are parasitic to New World monkeys. The human P.
vivax-like is indistinguishable from P. simiovale, a parasite of Old World
macaques. We conjecture that P. malariae, P. vivax, and P. vivax-like are
evolutionarily recent human parasites, the first two at least acquired only
within the last several thousand years, and perhaps within the last few
hundred years, after the expansion of human populations in South America
following the European colonizations. We estimate the rate of evolution of
the conserved regions of the CSP gene as 2.46 x 10(-9) per site per year.
The divergence between the P. falciparum and P. reichenowi lineages is
accordingly dated 8.9 Myr ago. The divergence between the three lineages
leading to the human parasites is very ancient, about 100 Myr old between
P. malariae and P. vivax (and P. vivax-like) and about 165 Myr old between
P. falciparum and the other two.
相似文献
7.
Photosynthetic enhancement studies performed at 619 nm (excitation of Systems I and II) and at 446 nm (mainly excitation of System I) revealed an 18% photosynthetic enhancement simultaneously with a 31% reduction in glycolate excretion. This observation supports the hypothesis that some glycolate may be consumed in an oxidation process associated with System I when System II is poorly excited and the supply of electrons from the water splitting process of photosynthesis is low. 相似文献
8.
9.
Hybridization in situ was used to identify rDNA in chromosomes of the pygmy chimpanzee, mountain gorilla, and siamang gibbon. In contrast to other Pongids, and man, the gorilla has only two pairs of rDNA-containing chromosomes. The single pair in the siamang bears no resemblance to the nucleolar chromosome of the closely related lar gibbon. Pan paniscus and P. troglodytes have the same rDNA distribution, and similar karyotypes except in the structure of chromosome 23p. Grain counts over unbanded preparations show that the human, orangutan, and both chimpanzees have about the same total rDNA multiplicity. 相似文献
10.
Nerve terminal regions in walking leg opener muscles of several crayfish of different ages (0 to 245 days after hatching) were examined by means of electron microscopy. This muscle is innervated by two axons (excitatory and inhibitory) and at maturity contains three classes of synapse: excitatory and inhibitory neuromuscular synapses, and inhibitory axo-axonal synapses. The muscle itself is initially a syncytium, which gradually becomes subdivided into distinct “muscle fibers” as the animal matures. Innervation was not found in the opener muscle just before or just after hatching, but was present in restricted locations on the inner side of the muscle within a few days of hatching. As the muscle enlarged and became subdivided, innervation appeared in various other locations. Synaptic contacts were located in young stages soon after hatching, and in later stages. Morphological differences characteristic of excitatory and inhibitory nerve terminals could be found even at the earliest stages of innervation. Both excitatory and inhibitory synapses, but particularly the former, showed evidence of progressive enlargement to a final size within the first two months, and no evidence for further enlargement of existing synapses thereafter. Synaptic maturation also involved the appearance of presynaptic “dense bodies” thought to be regions at which transmitter substance is preferentially released. Nerve terminals at different levels of maturation were observed in opener muscles of young crayfish. Clear evidence for differential maturation of the three types of synapse present in this muscle was obtained. The inhibitory neuromuscular synapses attained their final average size and developed their dense bodies sooner than the excitatory neuromuscular synapses. The inhibitory axo-axonal synapses were the last to appear and to mature. 相似文献