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排序方式: 共有143条查询结果,搜索用时 31 毫秒
31.
运用基于基因组数据库的特定基因同源新基因的克隆策略得到一个人类新基因WDR70 ,该基因编码一个包含 12个WD4 0结构域的蛋白。WDR70的cDNA序列长 2 2 6 6bp ,预测编码蛋白含 6 30个氨基酸 ,理论分子量为 70× 10 3 u ,染色体定位为 17p13.1。以小鼠胚胎为模型进行整体原位杂交 ,结果显示WDR70基因在 8.5d小鼠胚胎中没有表达 ,而在 9.5d和 10 .5d的小鼠胚胎的脑部有特异表达。由此推断该基因对胚胎期脑部的发育有重要的影响。 相似文献
32.
分泌型磷脂酶PLA2G5属于磷脂酶A2超家族的一员,在免疫细胞和非免疫细胞中均有表达.研究表明,PLA2G5参与生物学事件的发生发展,在特定的病理条件下具有诱导作用.本文简要阐述了PLA2G5的来源、结构特征、生物学功能和在疾病中的作用,以及现有或潜在的PLA2G5抑制剂,以期探索基于PLA2G5的治疗新靶标. 相似文献
33.
Insulin, glucagon, and somatostatin secretion by cultured rat islet cell tumor and its clones 总被引:2,自引:0,他引:2
S J Bhathena S Awoke N R Voyles S D Wilkins L Recant H K Oie A F Gazdar 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1984,175(1):35-38
Cells derived from rat islet tumor and grown in culture (parent cells-RIN-m) and two clones obtained from them were used to study the effect of various secretagogues on insulin, glucagon, and somatostatin secretion. Parent cells secreted all three hormones in various quantities, while clone 5F secreted predominantly insulin and clone 14B secreted predominantly somatostatin. The secretory behavior of these cells were compared to each other and to that of normal islets. In general, as in the case of normal islets, insulin secretion was stimulated by calcium, potassium, tolbutamide, theophylline, and glucagon. It was inhibited by somatostatin. Glucagon secretion was stimulated by calcium, arginine, and theophylline. Somatostatin secretion was stimulated in clone 14B by arginine, tolbutamide, theophylline, and insulin. These cells differ from normal islets, in that they do not respond to glucose or arginine with increased insulin secretion. Also somatostatin failed to inhibit glucagon secretion. The similarity in insulin secretory responses of parent cells and clone 5F suggests that local or paracrine islet hormone secretion plays only a negligible role in the control of other hormone secretion in these cells. 相似文献
34.
Molecular evolution of intergenic DNA in higher primates: pattern of DNA changes, molecular clock, and evolution of repetitive sequences 总被引:7,自引:1,他引:6
A 3.1-kb intergenic DNA fragment located between the psi beta-globin and
delta-globin genes in the beta-globin gene cluster was cloned from gorilla,
orangutan, rhesus monkey, and spider monkey, and the nucleotide sequence of
each fragment was determined. The phylogeny of these four sequences,
together with two previously published allelic sequences from humans and
one from chimpanzee, was constructed, and the accumulation of mutations in
the region was analyzed. The sites of base substitutions are not evenly
distributed within the region: two Alu repeats have accumulated 0.21 + 0.02
substitutions/site with 0.15 + 0.008 substitutions/site in the remainder of
the fragment. The occurrence of substitutions at neighboring sites is more
frequent than would be expected if they were independent. The observed
excesses disappear when ancestral -CG- dinucleotide sites are excluded. The
phylogenetic relationships of the sequences indicate that the human
sequence shares a most recent coancestor with the chimpanzee sequence. The
data also show that great apes have accumulated fewer mutations in this
part of the genome than has the rhesus monkey. The relative rates of
accumulation of 12 kinds of nucleotide substitution in the region during
primate evolution are asymmetric in the DNA strands. From these rates of
accumulation, the origin of a simple stretch of sequence near the 3' end of
the 3.1-kb fragment was deduced to be a sequence comprising 50% T and 50% C
on one strand. The two oppositely oriented Alu sequences in the 3.1-kb
region were inserted at their present positions before the divergence of
the New-World monkeys from other lineages. Our analysis shows that the
nucleotide sequences of the two Alu repeats in spider monkey are
unexpectedly similar both to each other and to the deduced ancestral
sequence of Alu repeats. The data suggest that there has been some type of
recombinational event between the spider monkey Alu repeats but that it was
not a simple gene conversion.
相似文献
35.
Yu-Rong DU Song-Chang GUO Zhao-Feng WANG Hai-Xing CI Zhen-Yuan CAI Qian ZHANG Jian-Ping SU Jian-Quan LIU 《植物分类学报》2010,48(6)
The Tibetan antelope(chiru,Pantholops hodgsoni),a heavily poached species and symbol of the QinghaiTibetan Plateau(QTP),is noted worldwide for its special calving migration.This species originated in the early Quaternary and it is interesting to know how the following climatic oscillations affected its demographic dynamics in the climate-sensitive QTP.In this study,we analyzed the mitochondrial D-loop region from 312 individuals sampled in all of the six major populations.We found high rates of gene flow and little genetic differentiation between populations,suggesting that the calving migration may have homogenized the genetic pool of this species.Both mismatch distribution analyses and coalescent simulations suggested that this species experienced a demographic expansion approximately 600-200 Kyt following the retreat of the large glaciers developed in the QTP at 800-600 Kyr,rather than at the end of the last glacial age,as previously suggested based on a limited sample size.In addition,we found evidence of a chiru population decrease probably related to the human settings at the QTP during the middle Holocene. 相似文献
36.
目的:探讨广义估计方程在CT显示方法研究中的应用.方法:采用SAS软件的GENMOD过程,应用广义估计方程方法分析CT显示方法研究实例.结果:给出了广义估计方程SAS程序,并对参数估计和两两比较结果进行解释.结论:广义估计方程能有效的分析CT显示方法研究中反应变量为两分类或多分类的非独立数据. 相似文献
37.
We analyze the stochastic structure of postural sway and demonstrate that this structure imposes important constraints on
models of postural control. Linear stochastic models of various orders were fit to the center-of-mass trajectories of subjects
during quiet stance in four sensory conditions: (i) light touch and vision, (ii) light touch, (iii) vision, and (iv) neither
touch nor vision. For each subject and condition, the model of appropriate order was determined, and this model was characterized
by the eigenvalues and coefficients of its autocovariance function. In most cases, postural-sway trajectories were similar
to those produced by a third-order model with eigenvalues corresponding to a slow first-order decay plus a faster-decaying
damped oscillation. The slow-decay fraction, which we define as the slow-decay autocovariance coefficient divided by the total
variance, was usually near 1. We compare the stochastic structure of our data to two linear control-theory models: (i) a proportional–integral–derivative
control model in which the postural system's state is assumed to be known, and (ii) an optimal-control model in which the
system's state is estimated based on noisy multisensory information using a Kalman filter. Under certain assumptions, both
models have eigenvalues consistent with our results. However, the slow-decay fraction predicted by both models is less than
we observe. We show that our results are more consistent with a modification of the optimal-control model in which noise is
added to the computations performed by the state estimator. This modified model has a slow-decay fraction near 1 in a parameter
regime in which sensory information related to the body's velocity is more accurate than sensory information related to position
and acceleration. These findings suggest that: (i) computation noise is responsible for much of the variance observed in postural
sway, and (ii) the postural control system under the conditions tested resides in the regime of accurate velocity information.
Received: 20 March 2001 / Accepted: 17 April 2002
Acknowledgements. We thank Tjeerd Dijkstra for bringing the slow-decay component of postural sway to our attention. Funding for this research
was provided by National Institutes of Health grant R29 N35070–01A2, John J. Jeka, PI.
Correspondence to: T. Kiemel (Tel.: +1-301-4056176, Fax: +1-301-3149358 e-mail: kiemel@glue.umd.edu) 相似文献
38.
Requirement of human chromosomes 19, 6 and possibly 3 for infection of hamster x human hybrid cells with baboon M7 type C virus. 总被引:5,自引:0,他引:5
The replication pattern of the endogenous baboon type C virus M7 was studied in 29 primary Chinese hamster × human hybrid clones generated with leukemic cells from two different patients with acute lymphoblastic or myeloblastic leukemia. There was no evidence of viral particulate RDDP or M7 antigen before viral infection. M7 virus replicated in human and some hybrid cells but not in Chinese hamster cells, indicating that M7 requires dominantly expressed human gene(s) for replication. Enzyme and cytogenetic analyses show that a gene(s) coded for by human chromosome 19 is necessary for M7 infection of these hybrids. Detailed cytogenetic correlations revealed, however, that the chromosome 19+/M7 + hybrid clones with intact chromosomes also had copies of chromosomes 3 and 6. Previously, Bevi, the putative integration site for M7 virus, has been assigned to human chromosome 6. Many clones with various combinations of chromosomes 3 and 6 lacked chromosome 19, however, and failed to replicate exogenously applied M7 virus, while tests of 27 secondary clones showed that M7 markers co-segregated with chromosome 19 markers. These findings all confirm the need for a chromosome 19-coded function in Chinese hamster × human hybrids. In addition, the yield of viral particulate RDDP produced into the culture fluid was 50–100 fold less per viral antigen-positive cell in the hybrids compared with human cells. Thus some form of regulation of viral components exists in the hybrid cells. When the virus replicating in hybrid cells was transferred back to human cells, this regulation was relaxed and the yield of RDDP per FA(+) cell greatly increased. We conclude that human chromosomes 6 and 19 code for functions involved in M7 virus metabolism, and we cannot exclude a function coded for by chromosome 3. 相似文献
39.
Chromosome binding site of latency-associated nuclear antigen of Kaposi's sarcoma-associated herpesvirus is essential for persistent episome maintenance and is functionally replaced by histone H1
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Shinohara H Fukushi M Higuchi M Oie M Hoshi O Ushiki T Hayashi J Fujii M 《Journal of virology》2002,76(24):12917-12924
Latency-associated nuclear antigen 1 (LANA1) of Kaposi's sarcoma-associated herpesvirus (KSHV; human herpesvirus 8) persistently maintains a plasmid containing the KSHV latent origin of replication (oriP) as a closed circular episome in dividing cells. In this study, we investigated the involvement of chromosome binding activity of LANA1 in persistent episome maintenance. Deletion of the N-terminal 22 amino acids of LANA1 (DeltaN-LANA) inhibited the interaction with mitotic chromosomes in a human cell line, and the mutant concomitantly lost activity for the long-term episome maintenance of a plasmid containing viral oriP in a human B-cell line. However, a chimera of DeltaN-LANA with histone H1, a cellular chromosome component protein, rescued the association with mitotic chromosomes as well as the long-term episome maintenance of the oriP-containing plasmid. Our results suggest that tethering of KSHV episomes to mitotic chromosomes by LANA1 is crucial in mediating the long-term maintenance of viral episomes in dividing cells. 相似文献
40.
巢湖蓝藻与农业废弃物共热解制取生物质油研究 总被引:1,自引:0,他引:1
采用蔗渣、玉米秸秆和棉花秸秆3种废弃物与蓝藻进行混合共热解试验,考察废弃物的加入对蓝藻热解液体产率及组分的影响。结果表明:添加3种废弃物均使共热解液体产率呈下降趋势。当蓝藻与废弃物以1∶1混合共热解时,以蓝藻和玉米秸秆共热解液体产率最高,为61.8%,且除苯酚类以外,液体产物组分与单一蓝藻热解产物组分相近,含氮化合物含量明显降低,相对含量由18.49%降至8.15%。与其它2种废弃物相比,蓝藻与玉米秸秆在适当比例下的共热解有利于改善热解油品质。 相似文献