全文获取类型
收费全文 | 33733篇 |
免费 | 1516篇 |
国内免费 | 1533篇 |
出版年
2024年 | 39篇 |
2023年 | 356篇 |
2022年 | 489篇 |
2021年 | 662篇 |
2020年 | 701篇 |
2019年 | 881篇 |
2018年 | 797篇 |
2017年 | 734篇 |
2016年 | 829篇 |
2015年 | 1115篇 |
2014年 | 1884篇 |
2013年 | 2769篇 |
2012年 | 1459篇 |
2011年 | 1506篇 |
2010年 | 1301篇 |
2009年 | 1485篇 |
2008年 | 1540篇 |
2007年 | 1537篇 |
2006年 | 1445篇 |
2005年 | 1363篇 |
2004年 | 1207篇 |
2003年 | 1168篇 |
2002年 | 1056篇 |
2001年 | 787篇 |
2000年 | 767篇 |
1999年 | 729篇 |
1998年 | 729篇 |
1997年 | 648篇 |
1996年 | 585篇 |
1995年 | 620篇 |
1994年 | 605篇 |
1993年 | 477篇 |
1992年 | 494篇 |
1991年 | 387篇 |
1990年 | 395篇 |
1989年 | 297篇 |
1988年 | 347篇 |
1987年 | 272篇 |
1986年 | 238篇 |
1985年 | 356篇 |
1984年 | 416篇 |
1983年 | 271篇 |
1982年 | 305篇 |
1981年 | 153篇 |
1980年 | 133篇 |
1979年 | 133篇 |
1978年 | 83篇 |
1977年 | 55篇 |
1976年 | 55篇 |
1973年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Toshifumi Nakao Ichiro Yamato Yasuhiro Anraku 《Molecular & general genetics : MGG》1987,208(1-2):70-75
102.
Summary In an attempt to identify proteins involved in the initiation of DNA replication, we have isolated a series of Saccharomyces cerevisiae mutants in which the function of putative replication origins is affected. The phenotype of these Rar- (regulation of autonomous replication) mutants is to increase the mitotic stability of plasmids whose replication is dependent on weak ARS elements. These mutations are generally recessive and complementation analysis shows that mutations in several genes may improve the ability of weak ARS elements to function. One mutation (rar1-1) also confers temperature-sensitive growth, and thus an essential gene is affected. We have determined the DNA sequence of the RAR1 gene, which reveals an open reading frame for a 48.5 kDa protein. The RAR1 gene is linked to rna1 on chromosome XIII. 相似文献
103.
Nicolas Mermod Juan L. Ramos Amos Bairoch Kenneth N. Timmis 《Molecular & general genetics : MGG》1987,207(2-3):349-354
104.
Sequence of the mglB gene from Escherichia coli K12: comparison of wild-type and mutant galactose chemoreceptors 总被引:1,自引:0,他引:1
Annette Scholle Jörg Vreemann Volker Blank Annette Nold Winfried Boos Michael D. Manson 《Molecular & general genetics : MGG》1987,208(1-2):247-253
Summary The mglB gene of Escherichia coli codes for a galactose-binding protein (GBP) that serves both as the galactose chemoreceptor and as the recognition component of the -methylgalactoside transport system. The mglB551 mutation eliminates the chemotactic function of GBP without altering its transport or substrate-binding properties. To investigate the interaction between GBP and Trg, the chemotactic signal transducer for galactose, we sequenced the mglB genes from wild-type and mglB551 mutant strains. The mutation causes the replacement of Gly74 of GBP by Asp. This residue is located in alpha-Helix III at the tip of the P domain in the GBP tertiary structure farthest removed from the substrate-binding cleft between the P and Q domains. We conclude that Helix III must be part of, or at least adjacent to, the recognition site for Trg. Our sequence also included part of the mglA gene, which is immediately distal to mglB. The amino acid sequence deduced for the beginning of the MglA protein showed homology with a family of polypeptides that contain an ATP-binding site and are components of binding-protein-dependent transport systems. 相似文献
105.
Restriction pattern analysis of deoxyribonucleic acid isolated from callus and cell suspension of actinorhizal and non-actinorhizal Betulaceae 总被引:1,自引:0,他引:1
Using cell suspensions, a method was elaborated to isolate high-molecular-weight genomic deoxyribonucleic acid (DNA; 65 MDa or more) from members of the Betulaceae: Alnus incana (L.) Moench, Alnus glutinosa (L.) Gaertn. and Betula papyrifera Marsh. The method was also effective for isolation of DNA from callus cells. Based on the chemical lysis of protoplasts, this procedure yielded 130 μg (callus) to 250 μg (cell suspension) of DNA (g fresh cells)−1 , with a ratio A200 /A28 of 1.7–2.0. The purified DNA obtained, formed distinct bands when restricted fragments were electrophoresed. Among the 10 endonucleases used for restriction analysis of Alnus glutinosa, Alnus incana and Betula papyrifera genomes, PvuI1 (EC 3.1.23.33) was unique in giving identical patterns for the two Ainus species. An unusual pattern occurred when Al-2 DNA was restricted with Ava II (EC 3.1.23.4). It formed a ladder with a repeating fragment unit of 181 base pairs long. With the enzymes tested, no differences in restriction patterns were observed among clones of Alnus incana (AI-2 vs AI-2), Betula papyrifera (BP-4 vs BP-8) and subclones of Ainus glutinosa AG-1 (PLFJ709 vs LF1709), suggesting genetic stability of the Betulaceae cultures. 相似文献
106.
The activity of the enzymes 5'-nucleotidase (EC 3.1.3.5), adenosine nucleosidase (EC 3.2.2.7), adenine phosphoribosyl transferase (EC 2.4.2.7) and acid phosphatase (EC 3.1.3.2) was determined in sections of tomato plant ( Lycopersicon esculentum Mill. cv. Bellina). The distribution of the enzymes changed markedly during development and a role for these enzymes in cytokinin metabolism is suggested. 相似文献
107.
Summary Mineral transport across the plasma membrane of plant cells is controlled by an electrochemical gradient of protons. This
gradient is generated by an ATP-consuming enzyme in the membrane known as a proton pump, or H+-ATPase. The protein has a catalytic subunit of Mr=100,000 and is a prominent band when plasma membrane proteins are analyzed
by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.
We generated specific rabbit polyclonal antibody against the Mr=100,000 H+-ATPase and used the antibody to screen λgtll expression vector libraries of plant DNA. Several phage clones producing immunoreactive
protein, and presumably containing DNA sequences for the ATPase structural gene, were isolated and purified from a carrot
cDNA library and a Arabidopsis genomic DNA library. These studies represent our first efforts at cloning the structural gene
for a plant plasma membrane transport protein. Applicability of the technique to other transport protein genes and the potential
for use of recombinant DNA technology in plant mineral transport research are discussed. 相似文献
108.
109.
Summary A method for isolating high quality DNA from wholeEuglena cells is described. The procedure consists in: the weakening of the cell pellicle in glycerol avoiding the mechanical disruption of cells and shearing damage in DNA molecules; the decondensation ofEuglena compact chromatin directly inside the cells; the complete dissociation of cells and nucleoproteins in sarkosyl detergent; the optional digestion of proteins and RNA with DNase-free enzymes and the final purification of DNA by isopycnic banding in CsCl gradients. Degradation of DNA is prevented all along the extraction procedure by glycerol, antioxydants, EDTA and sarkosyl detergent. Using the enzymatic digestion step, DNA containing few single-stranded nicks is obtained with a yield approaching 100%. DNA with no single-stranded nick could be obtained with a 35% yield when the enzymatic digestion step was omitted. In both cases, the double-stranded DNA has an average molecular weight equal or greater than 6×107. It is free of contaminants and could be easily digested with restriction enzymes. After digestion with Eco RI and size-fractionation in agarose gel this DNA has permitted specific hybridization of the rDNA sequences with a radioactive rRNA probe.Abbreviations Kbp
kilobasepairs
- Kb
kilobases 相似文献
110.
D. Aviv E. Galun 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1987,73(6):821-826
Summary We studied the chondriomes (the mitochondrial genomes) of sexual-progeny plants derived from eleven Nicotiana cybrids which resulted from donor-recipient protoplast fusions. The recipients were either N. tabacum or N. sylvestris and the donor (of the cytoplasm) was N. bigelovii. The chondriomes were characterized by the mitochondrial DNA (mtDNA) restriction-patterns. The differences in mtDNA restriction patterns were revealed after Sal I digestions and probing the respective Southern-blots with three mtDNA fragments. The hybridization patterns of mtDNAs from 35 second-generation plants (i.e. the sexual progeny derived from the cybrid plants) indicated only minor variations between plants derived from the same cybrid but pronounced variations among sibs derived from different cybrids. The mtDNA of 32 second-generation plants varied from both original fusion partners but the mtDNA of one (male-sterile) plant was apparently identical with the mtDNA of one of the original donor (N. bigelovii) and the mtDNA of two other (male-fertile) plants was apparently identical to the mtDNA of an original recipient (N. sylvestris). Generally, the mtDNAs of male-fertile, second-generation plants were similar to the mtDNAs of the original recipients while the mtDNAs of the male-sterile second-generation plants were similar to the mtDNA of the donor (N. begelovii). The analyses of mtDNAs from the thirdgeneration plants indicated stabilization of the chondriomes; no variations were detected between the mtDNAs of plants derived from a given second-generation plant. 相似文献