全文获取类型
收费全文 | 4273篇 |
免费 | 265篇 |
国内免费 | 260篇 |
出版年
2024年 | 2篇 |
2023年 | 59篇 |
2022年 | 57篇 |
2021年 | 114篇 |
2020年 | 81篇 |
2019年 | 103篇 |
2018年 | 106篇 |
2017年 | 83篇 |
2016年 | 124篇 |
2015年 | 127篇 |
2014年 | 166篇 |
2013年 | 218篇 |
2012年 | 127篇 |
2011年 | 137篇 |
2010年 | 101篇 |
2009年 | 180篇 |
2008年 | 187篇 |
2007年 | 210篇 |
2006年 | 233篇 |
2005年 | 194篇 |
2004年 | 160篇 |
2003年 | 171篇 |
2002年 | 165篇 |
2001年 | 165篇 |
2000年 | 136篇 |
1999年 | 143篇 |
1998年 | 150篇 |
1997年 | 160篇 |
1996年 | 118篇 |
1995年 | 103篇 |
1994年 | 102篇 |
1993年 | 86篇 |
1992年 | 77篇 |
1991年 | 60篇 |
1990年 | 51篇 |
1989年 | 34篇 |
1988年 | 44篇 |
1987年 | 37篇 |
1986年 | 33篇 |
1985年 | 35篇 |
1984年 | 40篇 |
1983年 | 19篇 |
1982年 | 41篇 |
1981年 | 18篇 |
1980年 | 13篇 |
1979年 | 12篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 8篇 |
1974年 | 1篇 |
排序方式: 共有4798条查询结果,搜索用时 15 毫秒
81.
乙肝前S2(HBVPreS2)肽段由55个氨基酸组成,其N端肽段含Th和B细胞抗原决定簇。我们将化学合成的PreS2epitope(120-145)基因与HBcAg基因不同位点进行融合,融合基因在大肠杆菌中获得表达,并对融合蛋白进行了纯化。经ELISA和Western-blot实验表明,融合蛋白具有PreS2和HBcAg两者的抗原性。此外,研究还表明,强启动子能使表达水平有一定提高。 相似文献
82.
本文给出了方程dx/dt=f(x(t-1))出现4/(2n 1),4/(2n-1),4/(2n-3),…,4/7,4/5,4/3,4一周期解并蕴含浑沌的一个条件。 相似文献
83.
伪狂犬病毒闽A株基因文库的构建及物理图谱分析 总被引:6,自引:0,他引:6
本文报道以质粒pBR322作载体,用鸟枪法克隆出了PRV闽A株除BamHI-1,2外的所有酶切片段,构建了PRV闽A株基因文库,并以克隆出的BamHI片段用光生物素标记作探针,应用分子杂交法确定了PRV闽A株绝大部分限制性内切酶位点的位置。 相似文献
84.
以聚丙烯酰胺凝胶电泳方法测定了331例辽宁满族新生儿脐带血血红蛋白F中Gγ/Aγ比值。结果显示:高Gγ(>80%)者4例,占1.21%,其基因频率(f)为0.00604,低Gγ(30-48%)者6例,占1.81%,其基因频率为0.00906,其余正常,Gγ平均值为65.23±6.38%。未发现AγT链。对其中八例异常者(4例高Gγ值,4例低Gγ值)的染色体DNA进行了基因图谱分析,确定4例高Gγ值者基因型有两种:Gγ-Gγ/Gγ-Aγ二例,Gγ-AGγ-Aγ/Gγ-Aγ二例;4例低Gγ值者基因型有二种,分别为:Aγ-Aγ/Gγ-Aγ二例和-GAγ/Gγ-Aγ二例。其中Aγ-Aγ基因型在中国人群中未见报道过。 相似文献
85.
The present study disclosed the cross-reactivity between Bermuda grass pollen (BGP) and other grass pollens using monoclonal antibodies (MAbs) and polyclonal antiserum. MAb 9–13, directed against a group of minor allergens of BGP (Cyn d Bd68K, 48K, 38K) was found to cross-react with extracts of ten other grass pollens. Immunoblotting assays illustrated that MAb 9–13 cross-reacted with multiple components of most of these pollens, and the major cross-reactive components had molecular weights of 29–36 kD. The cross-reactivity between BGP andLol pI, the group I allergen of rye grass pollen, was further evaluated;Lol pI was recognized by MAb 9–13, but not by our MAbs/polyclonal antiserum againstCyn dI, the major allergen of BGP. These results suggest that the epitope recognized by MAb 9–13 is a common (C) epitope shared byLol pI andCyn d Bd68K, 48K, 38K, andCyn dI does not share significant antigenicity withLol pI. In a modified radio-allergosorbent test, IgE antibodies in the serum of BGP-allergic patients reacted mildly with C-epitope-bearing components of both BGP and rye grass pollens, and this binding could be blocked specifically by MAb 9–13. This suggests that in addition to an antigenic cross-reaction, the C epitope can also lead to an allergenic cross-reaction. 相似文献
86.
Summary The last decade has witnessed successful applications of plant tissue culture techniques in several crops. During that same
period, studies in plant molecular genetics have also grown exponentially. Molecular markers (isozymes, RFLPs, and PCR-based
markers such as RAPDs) are now used to study many of the current limitations of tissue culture. They have been used to investigate
mechanisms that underlie somaclonal variation in the nuclear, mitochondrial, and chloroplast genomes. One recurrent problem
with several tissue culture systems has been the difficulty of determining the origin of regenerants. Molecular markers represent
powerful tools to determine precisely the origin of plants derived from microspore or anther culture, protoplast fusion, and
other tissue culture studies where this information is important. With improvements in tissue culture techniques, populations
of doubled haploid lines have been produced in several major crop species. Doubled haploid populations have proven useful
in the production of molecular maps and in tagging important agronomic traits. This review describes the use of molecular
markers to address fundamental and practical questions of plant tissue culture, and discusses the potential of improvements
in molecular techniques and new molecular markers such as SCAR and STS along with high-resolution mapping strategies. 相似文献
87.
Corine Vernet Joëlle Boretto Marie-Geneviève Mattéi Masahide Takahashi Lucinda J. W. Jack Ian H. Mather Sylvie Rouquier Pierre Pontarotti 《Journal of molecular evolution》1993,37(6):600-612
Summary During a search for novel coding sequences within the human MHC class I region (chromosome 6p21.3), we found an exon (named B30-2) coding for a 166-amino-acid peptide which is very similar to the C-terminal domain of several coding sequences: human 52-kD Sjögren's syndrome nuclear antigen A/Ro (SS-A/Ro) and ret finger protein (RFP), Xenopus nuclear factor 7 (XNF7), and bovine butyrophilin. The first three of these proteins share similarities over the whole length of the molecule whereas butyrophilin is similar in the C-terminal domain. The N-terminal domain of butyrophilin is similar to rat myelin/oligodendrocyte glycoprotein (MOG) and chicken B blood group system (B-G) protein. These domains are components of a new subfamily of the immunoglobulin superfamily (IgSF). Butyrophilin is thus a mosaic protein composed of the MOG/B-G Ig-like domain and the C-terminal domain of 52-kD SS-A/Ro, RFP, and XNF7 (1330-2-like domain). Moreover, in situ hybridization shows that RFP, butyrophilin, and MOG map to the human chromosome 6p2l.3-6p22 region and are thus close to the MHC class I genes. It is therefore possible that the butyrophilin gene is the product of an exon shuffling event which occurred between ancestors of the RFP and MOG genes. To our knowledge, this is the first example of the colocalization of a chimeric gene and its putative progenitors. Finally, regulatory protein T-lymphocyte 1 (Rpt-1) shares similarities with the N-terminal halves of RFP, 52-kD SS-A/Ro, and XNF7, but not with the B30-2-like domain. We show that the ancestral Rpt-l gene evolved by overprinting.
Correspondence to: P. Pontarotti 相似文献
88.
Mapping of genes controlling seed storage-proteins and cytological markers on chromosome 1R of rye 总被引:1,自引:0,他引:1
J. Orellana B. Fernández-Calvín J. F. Vázquez J. M. Carrillo 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1993,85(5):639-643
Summary Rye secalins, telomeric C-bands, and telocentric chromosomes were used as markers in the progeny of a test-cross in order to determine the position of seed storage-protein genes Glu-R1 and Gli-R1 with respect to the centromere and both telomeres of chromosome 1 R in rye. These genes were linked to the centromere (32.35±3.28% and 36.27±3.37% recombination, respectively). Glu-R1 was loosely linked to the telomere of the long arm (43.63±3.47% recombination), while Gli-R1 was closely linked to the telomere of the short arm (9.80±2.08% recombination). This finding supports the possibility that rye - and -secalin genes may be located on the satellites, as has been described in wheat for genes that code similar proteins. The importance of metaphase-I pairing failure and its consequences for the estimation of the recombination fraction are also discussed. 相似文献
89.
D. A. Laurie N. Pratchett K. M. Devos I. J. Leitch M. D. Gale 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1993,87(1-2):177-183
The 5S rDNA locus on the long arm of barley chromosome 2(2H) was genetically mapped in two crosses in relation to 30 other RFLP loci. Comparison of the genetic maps with the previously published physical position of the 5S rDNA, determined by in-situ hybridization, showed that there was a marked discrepancy between physical and genetic distance in both crosses, with recombination being less frequent in the proximal part of the arm. Pooled information from the present study and other published genetic maps showed that at least 26 of the 44 (59%) RFLPs that have been mapped on 2(2H)L lie distal to the 5S rDNA locus even though this region is only 27% of the physical length of the arm. The distribution of RFLP markers is significantly different from expected (P < 0.01), implying that the low-copy sequences used for RFLP analysis occur more frequently in distal regions of the arm and, or, that sequences in distal regions are more polymorphic. 相似文献
90.
Linkage relationships between prolamin genes on chromosomes 1A and 1B of durum wheat 总被引:5,自引:0,他引:5
M. Ruiz J. M. Carrillo 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1993,87(3):353-360
Gliadin and glutenin electrophoresis of F2 progeny from four crosses of durum wheat was used to analyse the linkage relationships between prolamin genes on chromosomes 1A and 1B. The results showed that these genes are located at the homoeoallelic lociGlu-1,Gli-3,Glu-3 andGli-1. The genetic distances between these loci were calculated more precisely than had been done previously for chromosome 1B, and the genetic distances betweenGli-A3,Glu-A3 andGli-A1 on chromosome 1A were also determined. Genes atGli-B3 were found to control some-gliadins and one B-LMW glutenin, indicating that it could be a complex locus. 相似文献