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排序方式: 共有356条查询结果,搜索用时 15 毫秒
291.
Odile Bertaux P. Puigdomenech Christine Mederic J. D. Rouzeau J. Palau R. Valencia 《Protoplasma》1985,128(2-3):190-200
Summary A novel method for isolatingEuglena gracilis Z. nuclei, based on pretreatment of cells in concentrated glycerol buffer before homogenization, is described. Such a treatment weakens the tough cell pellicle facilitating cell disruption, and avoids nuclear damage induced by detergents and by freezing and thawing the cells in aqueous media. Nuclei, purified by centrifugation in dense sucrose, are obtained with a 30% yield, and only small amounts of cell wall fragments contaminate the nuclear pellets. The purified nuclei retain their ultrastructural characteristics. High molecular weight DNA, as well as undegraded RNA species and histones, can be extracted from these nuclei. Nuclease digestions and spread preparations show an unaltered nucleosomal structure of chromatin. This method has been applied to cell samples at any stage of the cell cycle, including mitosis, since inEuglena the nuclear envelope persists during cell division. 相似文献
292.
293.
1. The histones of trout liver were examined and four main fractions (f1, f2b, f2a and f3) were isolated and characterized. 2. The amino acid analyses, N-terminal group analyses and starch-gel electrophoresis patterns are remarkably similar to the corresponding fractions of calf thymus. 3. The group f2a was also separated into two subfractions, f2al and f2a2, which are similar to those of calf thymus. 相似文献
294.
酵母酸性磷酸酯酶转录调控因子PHO2的功能域分析 总被引:5,自引:5,他引:0
利用定点诱变,氨基酸插入或缺失的方法对PHO2进行结构改造,观察对其功能的影响。PHO2蛋白的同源域中有α-螺旋2-β-转我-α螺旋3的结构,是转录因子结构DNA的功能域。定点诱变α-螺旋3上的Ile123为Pro123或者在α-螺旋2中插入PDPD4个氨基酸,破坏α-螺旋的结构,可导致PHO2功能的丧失。氨基酸片段的缺失分析表明,N端Gin丰富区大部缺失,对PHO2功能没有影响;而包含酸性氨基酸 相似文献
295.
Inmaculada Ponte Pedro Guillén Rosa M Debón Manuel Reina Anna Aragay Enric Espel Natale Di Fonzo Jaume Palau 《Plant molecular biology》1994,26(6):1893-1906
Nuclear extracts from maize endosperm were used to investigate protein-DNA interactions in the 5-upstream region of the Zc1 and Zc2 genes. These genes encode for zeins of apparent molecular mass (MWapp) 16 and 28 kDa, respectively, which accumulate in the endosperm during seed maturation. Binding assays revealed specific binding of a nuclear protein to three A/T-rich elements, 0.9–1.0 kbp upstream from the initiation codon. One of these elements (41 bp, 88% A/T), present in Zc1, contained a 13 nucleotide duplication. The other two (28 bp, 86% A/T; 42 bp alternating A-T) are consecutive elements in Zc2. Competition experiments strongly suggest that the three elements bind to the same protein. Protein-DNA interaction was detected in endosperm nuclear extracts of 8 to 21 days after pollination (DAP), as well as in 25 DAP embryos and in different tissues from plantlets. The protein factor has an MWapp of ca. 30 kDa. This factor has properties suggesting it is an HMG-like protein. These results are consistent with a growing accumulation of data for a number of genes indicating that A/T-rich elements, located at distal and proximal zones of the 5-flanking sequences, interact with HMG-like proteins. 相似文献
296.
O. Bartsch U. König M. B. Petersen H. Poulsen M. Mikkelsen F. Palau F. Prieto E. Schwinger 《Human genetics》1993,92(2):127-132
A Spanish family has previously been described with two siblings with dup(21q) Down syndrome. The father has a normal karyotype. The mother has a microchromosome. Cytogenetic, fluorescence in situ hybridization and DNA studies have now been carried out on the family. Findings include that the mother has three different chromosome anomalies, viz. (1) a chromosome 22 with an unusual pericentromeric region that contains alphoid DNA from chromosomes 21/13 and chromosome 22, (2) an isochromosome 21p in the frequent cell line and (3) an isochromosome 21q in a rare second cell line. A possible explanation is that the mother developed from a zygote with trisomy 21 and that mitotic error in early development resulted in the formation of two cell lines with karyotypes of 47,XX,+i(21p) and 47,XX,+i(21q), respectively. The unusual chromosome 22 represents a hitherto undescribed chromosome anomaly and one possible explanation is a translocation of the short arms between chromosomes 21/13 and 22 in the ancestry of the family. The relationship between the unusual chromosome 22 and the isochromosome formation in the mother is not known. However, all three chromosome anomalies involve the alphoid DNA of chromosome 21/13, indicating that this is not a chance finding. 相似文献
297.
RNP, Sm and SS-B nuclear antigens from calf thymus were studied with respect to the size distribution on sucrose gradients as well as to the molecular integrity and related structural changes when they were subjected to enzymatic digestions under different conditions. Making a difference with RNP particles, the Sm size distribution is concentration dependent, a property in accordance with the complexity of the Sm particles in comparison with the RNPs. The use of combined effects of temperature, endogenous proteases and RNase A, allowed us to gain insight into the limits of stability of the three antigenic particles. Following treatments in the absence of RNAse A, the degradation products (32-38 Kd molecular weight) of the 70 Kd RNP polypeptide remain stable and associated with other molecules within the RNP particle. It was also found that the phosphate groups of the SS-B protein moiety are only accessible to alkaline phosphatase if the RNA of the SS-B particle is degraded by the action of RNAse A. 相似文献
298.
J S Salas Valien M T Ribas Ari?o M T Palau Benavides M A González Morán 《Histology and histopathology》1991,6(4):439-442
We report a case about a neonate who died of severe subaortic stenosis due to a giant vascular dilation of the left ventricular outflow tract. We emphasize the fatal result of this benign lesion and make differential diagnosis with haemangiomas and valvular blood cysts. 相似文献
299.
We studied a human protein paralog cluster formed by 38 nonredundant
sequences taken from the Swiss-Prot database and its supplement, TrEMBL.
These sequences include nuclear receptors, nuclear-receptor factors and
nuclear-receptor-like orphans. Working separately with both the central
cysteine-rich DNA-binding domain and the carboxy-terminal ligand-binding
domain, we performed multialignment analyses that included drawings of
paralog trees. Our results show that the cluster is highly multibranched,
with considerable differences in the amino acid sequence in the
ligand-binding domain (LBD), and 17 proximal subbranches which are
identifiable and fully coincident when independent trees from both domains
are compared. We identified the six recently proposed subfamilies as groups
of neighboring clusters in the LBD paralog tree. We found similarities of
80%-100% for the N-terminal transactivation domain among mammalian ortholog
receptors, as well as some paralog resemblances within diverse subbranches.
Our studies suggest that during the evolutionary process, the three domains
were assembled in a modular fashion with a nonshuffled modular fusion of
the LBD. We used the EMBL server PredictProtein to make secondary-structure
predictions for all 38 LBD subsequences. Amino acid residues in the
multialigned homologous domains--taking the beginning of helix H3 of the
human retinoic acid receptor-gamma as the initial point of reference--were
substituted with H or E, which identify residues predicted to be helical or
extended, respectively. The result was a secondary structure multialignment
with the surprising feature that the prediction follows a canonical pattern
of alignable alpha-helices with some short extended elements in between,
despite the fact that a number of subsequences resemble each other by less
than 25% in terms of the similarity index. We also identified the presence
of a binary patterning in all of the predicted helices that were conserved
throughout the 38-sequence sample. Our results fit well with a recently
proposed evolutionary model that combines protein secondary structure and
amino acid replacement. We propose a new hypothesis for molecular
evolution, in which chaperones--acting as an endogenous cellular device for
selection--play a crucial role in preserving protein secondary structure.
相似文献
300.
酵母PHO2与PHO4蛋白的激活活性的分析及两者的相互作用 总被引:3,自引:3,他引:0
PHO2与PHO4是酵母PHO5基因的两个正调控因子,本文发现,PHO2与酵母转录因子GAL4的DNA结合功能域融合后就能激活报道基因lacZ的表达,其激活力受高低磷影响,表明PHO2蛋白上存在酸性转录激活区。PHO2蛋白上酸性氨基酸丰富的287-326肽段并非PHO2的激活区。在PHO2蛋白上230位Ser处于磷酸化状态2PHO2才有激活作用,表明了这一磷酸化位点可能与PHO2的转录激活能力有关 相似文献