全文获取类型
收费全文 | 528篇 |
免费 | 51篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 8篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 9篇 |
2016年 | 21篇 |
2015年 | 30篇 |
2014年 | 32篇 |
2013年 | 32篇 |
2012年 | 35篇 |
2011年 | 38篇 |
2010年 | 39篇 |
2009年 | 18篇 |
2008年 | 25篇 |
2007年 | 21篇 |
2006年 | 36篇 |
2005年 | 17篇 |
2004年 | 25篇 |
2003年 | 27篇 |
2002年 | 21篇 |
2001年 | 7篇 |
2000年 | 15篇 |
1999年 | 9篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1979年 | 2篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1971年 | 2篇 |
1969年 | 2篇 |
1965年 | 2篇 |
1964年 | 2篇 |
1960年 | 2篇 |
1926年 | 1篇 |
排序方式: 共有579条查询结果,搜索用时 187 毫秒
461.
Wessel van der Loo Christianne E. Bouton Maria Sanchez Florence Mougel Enrique Castién Raymond Hamers Monique Monnerot 《Immunogenetics》1995,42(5):333-341
The b6w2 allotype of the constant region of the rabbit immunoglobulin kappa 1 (k1) light chain (b locus) was discovered in wild populations from northern Spain. At the serological level, the b6w2 allotype is characterized by the presentation of all b6-specific epitopes, while an allotypic determinant which is shared between the nominal b5 and b6 allotypes is lacking. The DNA fragment encoding the b6w2 allotype was amplified by means of the polymerase chain reaction, and sequenced directly by dideoxy-DNA-sequencing. When compared with the sequence of the nominal b6 allele, the b6w2 sequence differs at eleven nucleotide positions (96.5% similarity). This variation corresponds to amino acid replacements at 1) the three positions C-terminal to the peptidyl junction with the variable region (amino acid positions 109–111);2) the four positions N-terminal to the interdomain disulfide bond (167–170); and 3) two positions in the vicinity of the interchain disulfide bond (190 and 210). The nature and distribution of the observed nucleotide substitutions strongly suggest a possible role of the extra interdomain disulfide bond in the unusual evolutionary dynamics of the rabbit K1 light chain.The nucleotide sequence data reported in this paper have been submitted to the EMBL nucleotide sequence database and have been assigned the accession number Z48308 相似文献
462.
463.
Jeong Won Jahng Thomas C. Wessel Thomas A. Houpt Jin H. Son Tong H. Joh 《Journal of neurochemistry》1996,66(1):14-19
Abstract: Aromatic l -amino acid decarboxylase (AADC) is found in both neuronal cells and nonneuronal cells, and a single gene encodes rat AADC in both neuronal and nonneuronal tissues. However, two cDNAs for this enzyme have been identified: one from the liver and the other from pheochromocytoma. Exons 1a and 1b are found in the liver cDNA and the pheochromocytoma cDNA, respectively. In the third exon (exon 2), there are two alternatively utilized splicing acceptors specific to these exons, 1a and 1b. Structural analysis of the rat AADC gene showed that both alternative promoter usage and alternative splicing are operative for the differential expression of this gene. To demonstrate whether alternative promoter usage and splicing are tissue specific and whether the exons 1a and 1b are differentially and specifically transcribed in nonneuronal and neuronal cells, respectively, in situ hybridization histochemistry for the rat brain, adrenal gland, liver, and kidney was carried out using these two exon probes. The exon 1a probe specifically identified AADC mRNA only in nonneuronal cells, including the liver and kidney, and the exon 1b probe localized AADC mRNA to monoaminergic neurons in the CNS and the adrenal medulla. Thus, both alternative promoter usage and differential splicing are in fact operative for the tissue-specific expression of the rat AADC gene. 相似文献
464.
A computer-aided procedure is presented providing subjects with analogous visual feedback of respiratory resistance, which is continuously measured using the forced oscillation method. Simultaneous pneumotachographical control of the breathing volume curve makes it possible to prevent reinforcement for decreases of respiratory resistance which are due to increases of functional residual capacity (FRC). Lung hyperinflation is an unsuitable way to reduce respiratory resistance; if it occurs, feedback is interrupted until the subject decreases his FRC to its initial level. Analysis of the data of 15 adult asthmatic subjects which underwent a 12-sessions feedback training showed that no substantial changes of FRC appeared within feedback trials. Advantages of this new biofeedback technique compared to other procedures are discussed with regard to volume control and feedback signal. 相似文献
465.
Endonuclease activity of Escherichia coli DNA helicase I directed against the transfer origin of the F factor. 总被引:8,自引:0,他引:8 下载免费PDF全文
DNA helicase I, the traI gene product of the Escherichia coli F factor, was shown to be associated with endonuclease activity specific for the transfer origin of the F plasmid, oriT. In the presence of Mg2+, the purified enzyme forms a complex, stable in the presence of sodium dodecylsulfate (SDS) with a negatively superhelical chimeric plasmid containing oriT. The enzyme nicks and, after this, apparently binds to the 5' nick terminus when this complex is heated in the presence of SDS and/or EDTA or treated with proteinase K. Dideoxy sequencing locates the nick site in the F DNA strand transferred during bacterial conjugation after nucleotide 138 clockwise of the mid-point of the BglII site at 66.7 kb of the F genetic map. A sequencing stop after nucleotide 137 of this strand (where oriT-nicking seems to occur in vivo) is possibly an artefact caused by helicase I protein attached to the 5' terminal nucleotide. Deletion in the amino-terminal part of the traI polypeptide abolishes the oriT-nicking activity while leaving the strand-separating activity intact. These results confirm the prediction from genetic studies that helicase I is bifunctional with site-specific endonuclease and strand-separating activities. 相似文献
466.
Cortical granule-specific components are present within oocytes and accessory cells during sea urchin oogenesis 总被引:1,自引:0,他引:1
G M Wessel 《The journal of histochemistry and cytochemistry》1989,37(9):1409-1420
The coordinate expression of cortical granule-specific components in sea urchin oogenesis was studied using antibody probes. The components used to generate the organelle-specific antibodies included the whole cortical granule exudate, fertilization envelopes, hyalin, beta, 1-3,glucanase, and Ig8. Using immunolocalization techniques at both the light and electron microscopic levels, these molecules were found to be specific to cortical granules in three distinct cell types: developing oocytes, eggs, and accessory cells. In early oocytes, each of the cortical granule components are coordinately accumulated in the developing cortical granules dispersed throughout the cytoplasm. No other organelle within the developing oocytes or eggs contained detectable levels of any of these epitopes. In the somatic interstitial tissue of the ovary, cortical granule components also were accumulated specifically within cortical granule structures. Found only in select accessory cells, these cortical granules were indistinguishable in morphology and epitope composition from eggs and were contained within cytoplasmic aggregates termed mosaic globules. The mechanism of cortical granule concentration into mosaic globules is unknown, but this demonstration of common organelle constituents between oocytes and accessory cells may provide insight for such an understanding. 相似文献
467.
N Topley J Floege K Wessel R Hass H H Radeke V Kaever K Resch 《Journal of immunology (Baltimore, Md. : 1950)》1989,143(6):1989-1995
Both IL-1 alpha and IL-1 beta and TNF-alpha induced a time- and dose-dependent release of authentic PGE2 from cultured human glomerular mesangial cells (HMC). This release became significant only after a 4- to 6-h lag phase, and was abolished by inhibition of protein synthesis, and was not related to cell proliferation. Combinations of IL-1 and TNF-alpha when added simultaneously to HMC resulted in a dose-dependent synergistic increase in PGE2 production. These stimulatory effects were specifically inhibited by anticytokine antibodies and the synergistic effect required the simultaneous presence of both IL-1 and TNF-alpha. Arachidonic acid (AA) release experiments and measurement of cyclooxygenase activity, revealed that while both were increased by IL-1 beta and TNF-alpha alone (IL-1 beta greater than TNF-alpha), combinations of IL-1 beta and TNF-alpha resulted in only additive increases in AA release and cyclooxygenase activity. Taken together, these data suggest that stimulation of PGE2 in HMC, by combinations of these cytokines, is not rate limited by AA release or cyclooxygenase activation, but may be related to the induction of the distal enzymes controlling specific PG synthesis. 相似文献
468.
Sequence independent duplex DNA opening reaction catalysed by SV40 large tumor antigen. 总被引:11,自引:0,他引:11
Simian virus 40 (SV40) large tumor antigen (T antigen) is mainly localized in the nucleus where it exhibits two biochemical properties: DNA binding and helicase activity. Both activities are necessary for viral DNA replication and may also enable T antigen to modulate cellular growth. Here we present biochemical and electron microscopic evidence that the helicase activity can start at internal sites of fully double-stranded DNA molecules not containing the SV40 origin or replication. Using T antigen specific monoclonal antibodies, this unwinding reaction can be biochemically divided in an initiation (duplex opening) and a propagation step. The duplex opening reaction (as well as the propagation step) does not depend on a specific DNA sequence or secondary structure. In addition, we have found that T antigen forms an ATP dependent nucleoprotein complex at double-stranded DNA, which may be an essential step for the sequence independent duplex DNA opening reaction. 相似文献
469.
We have determined the chromosomal localization of the gene for the regulatory subunit RIIα of cAMP-dependent protein kinase (locus PRKAR2A) to human chromosome 3 using polymerase chain reaction (PCR) and Southern blot analysis of two different somatic cell hybrid mapping panels. Furthermore, PCR analysis of a chromosome 3 mapping panel revealed the presence of a human RIIα-specific amplification product only in cell lines containing the region 3p21.3–p21.2. The localization of PRKAR2A was confirmed by PCR mapping using the Stanford G3 Radiation Hybrid Panel as template. The results from this analysis demonstrated that PRKAR2A is most closely linked to D3S3334 (lod score 12.5) and flanked by D3S1322E and D3S1581. 相似文献
470.