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51.
William G. A. Brown Karina Needham Bryony A. Nayagam Paul R. Stoddart 《Journal of visualized experiments : JoVE》2013,(77)
It has been demonstrated in recent years that pulsed, infrared laser light can be used to elicit electrical responses in neural tissue, independent of any further modification of the target tissue. Infrared neural stimulation has been reported in a variety of peripheral and sensory neural tissue in vivo, with particular interest shown in stimulation of neurons in the auditory nerve. However, while INS has been shown to work in these settings, the mechanism (or mechanisms) by which infrared light causes neural excitation is currently not well understood. The protocol presented here describes a whole cell patch clamp method designed to facilitate the investigation of infrared neural stimulation in cultured primary auditory neurons. By thoroughly characterizing the response of these cells to infrared laser illumination in vitro under controlled conditions, it may be possible to gain an improved understanding of the fundamental physical and biochemical processes underlying infrared neural stimulation. 相似文献
52.
Observations were made of a wild population of sugar gliders ( Petaurus breviceps ) by live-trapping and on four captive colonies to establish the relationship between blood concentration of testosterone, body weight, social dominance and the timing of births. In both the wild and in captivity one male exhibits a testosterone concentration far higher than his fellows, during the breeding season. This male is also the heaviest. In captivity this male is observed to be socially the most dominant and undertakes almost all of the scent-marking. At least three-quarters of each breeding season's births occur during the first month of the three- to four-month season (July-September/October), a passage of time during which the body weight of the most dominant male falls more than that of the subordinates. It is suggested that this species is highly polygynous, with the ecological and evolutionary benefits of high social status being immense. 相似文献
53.
54.
The sequences of the 5' long-terminal repeat (LTR) and adjacent leader
regions of 27 full-length copia elements isolated from natural populations
of Drosophila melanogaster, D. simulans, and D. mauritiana are presented.
Phylogenetic analyses indicate that although D. melanogaster copia elements
are distinct from those of D. simulans and D. mauritiana, the elements of
these latter two species are not distinguishable from one another. LTRs and
adjacent 5' leader regions of elements isolated from D. simulans and D.
mauritiana are structurally similar to one another and carry substantial
deletional variation mapping to regions previously identified as being of
potential importance for copia expression.
相似文献
55.
Cultured chondrocytes derived from the caudal and cephalic ends of embryonic chick sterna have been compared with each other
and with whole sternum, by using a panel of 21 lectins to probe the distribution of oligosaccharides in glycoconjugates of
cells and matrix at various times of culture or development. On culture in collagen gels, the cells changed their morphology
with time, degrading glycan in the surrounding culture medium and depositing new matrix, the glycan content of which reflected
the site of origin of the cells, indicating that the glycan phenotype of both cells and matrix (‘glycotype’) was predetermined
and persistent. Sterna of embryonic chicks showed unexpected complexity in their distribution pattern of glycan, containing
at least six distinct regions. Major regional temporal differences were evident among saccharides terminating in α-N-acetyl
galactosamine and β-galactose, while changes in glycans terminating in fucose, sialic acid and α-mannose were somewhat less
marked. Subsets of complex N-glycans changed little.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
56.
South Asians with ulcerative colitis exhibit altered lectin binding compared with matched European cases 总被引:2,自引:0,他引:2
R. F. T. Mcmahon B. F. Warren C. J. P. Jones J. F. Mayberry C. S. J. Probert A. P. Corfield R. W. Stoddart 《Journal of molecular histology》1997,29(6):469-477
Ulcerative colitis is associated with abnormalities of mucin synthesis and secretion, features that may also be associated
with malignant change. It has been shown that South Asians in Britain have a high incidence of ulcerative colitis but a low
incidence of colorectal carcinoma compared with their European counterparts. Previous studies have demonstrated changes in
colonic mucin sialylation and sulphation in both South Asian and European cases with ulcerative colitis. This was related
to disease severity, but changes were also found in quiescent disease. The aim of the present study was to determine glycoconjugate
expression in the colon from South Asian cases and to compare results with those from a group of affected Europeans. Glycans
were identified in formalin-fixed, paraffin-embedded tissue from 17 South Asian patients with ulcerative colitis and from
11 European patients with a similar degree of colitis, by the application of 10 biotinylated lectins. These were directed
against a range of sialyl, fucosyl and 2-deoxy, 2-acetamido-galactosyl sequences, using an avidin--peroxidase revealing system
and semiquantitative assessment. The South Asian group showed a reduction in the binding of agglutinins from Sambucus nigra
in the apical-membranous region of enterocytes, and a decrease in apical Maackia amurensis agglutinin binding. These results
suggest that South Asians with ulcerative colitis show a different distribution of terminal N-acetyl neuraminyl residues,
either in their α-2,6 or α-2,3 linkage, compared with their European counterparts. The changes in sialylation observed in
European cases compared with normal disease-free control subjects were present in quiescent disease, but were also related
to disease activity. Their absence in Asians with ulcerative colitis may imply an inherent, genetically determined variation
in this group, which may also play a part in their reduced risk of subsequent malignancy 相似文献
57.
Molecular cloning of the cDNA encoding a murine sialic acid-specific 9-O-acetylesterase and RNA expression in cells of hematopoietic and non-hematopoietic origin. 总被引:2,自引:0,他引:2 下载免费PDF全文
We describe the isolation of a cDNA encoding a murine sialic acid-specific 9-O-acetylesterase as well as its expression pattern in cells of both hematopoietic and non-hematopoietic origin. This enzyme catalyzes the removal of O-acetyl ester groups from position 9 of the parent sialic acid N-acetylneuraminic acid. The cDNA is 2105 nt in length and encodes a protein of 541 amino acids with a predicted molecular weight of 61 kDa, not including oligosaccharides linked to eight potential N-glycosylation sites. The cDNA encoding the acetylesterase displays a widespread distribution in various cell lines and tissues. Expression studies of B lineage cell lines and primary fetal liver cells revealed a developmentally regulated expression pattern in cells of hematopoietic origin. Given the importance of 9-O-acetylation of sialic acids, the cloning of the cDNA encoding a sialic acid-specific 9-O-acetylesterase will be helpful in understanding further the regulation of this post-translational modification and the biological consequences thereof. 相似文献
58.
Comparisons of the molecular evolutionary process at rbcL and ndhF in the grass family (Poaceae) 总被引:2,自引:1,他引:1
We examine rate heterogeneity among evolutionary lineages of the grass
family at two plasmid loci, ndhF and rbcL, and we introduce a method to
determine whether patterns of rate heterogeneity are correlated between
loci. We show both that rates of synonymous evolution are heterogeneous
among grass lineages and that are heterogeneity is correlated between loci
at synonymous sites. At nonsynonymous sites, the pattern of rate
heterogeneity is not correlated between loci, primarily due to an aberrant
pattern of rate heterogeneity at nonsynonymous sites of rbcL. We compare
patterns of synonymous rate heterogeneity to predictors based on the
generation time effect and the speciation rate hypotheses. Although there
is some evidence for generation time effects, neither generation time
effects nor speciation rates appear to be sufficient to explain patterns of
rate heterogeneity in the grass plastid sequences.
相似文献
59.
60.
C. D. Woodroffe D. R. Stoddart T. Spencer T. P. Scoffin A. W. Tudhope 《Coral reefs (Online)》1990,9(1):31-39
There is evidence of Holocene emergence on several of the Cook Islands. On Suwarrow Atoll there are extensive outcrops of emergent, but truncated, reef on the northern atoll rim, radiocarbon-dated 4680–4310 years B. P., overlain by younger cemented boulder conglomerates. On the northeast of the atoll there are fossil algal ridges indicating up to 1 m of emergence; the landwardmost has been dated 4220 years B. P., the intermediate one 3420 years B. P. and the present one 1250 years B. P. On Mitiaro, a makatea island in the Southern Cooks, there are emergent reefal deposits in the centre of the reef flat dated 5140–3620 years B. P. Similar thought poorly preserved deposits occur on Mauke, and an erosional bench and notch occurs on Atiu. Emergence on all islands appears synchronous with that reported on Mangaia, where a relative fall of sea level of at least 1.7 m in the last 3400 years has been reported. The evidence for emergence is broadly similar to that described from French Polynesia, though timing of emergence appears to differ. 相似文献