全文获取类型
收费全文 | 201684篇 |
免费 | 151614篇 |
国内免费 | 37960篇 |
出版年
2022年 | 3243篇 |
2021年 | 7382篇 |
2020年 | 5622篇 |
2019年 | 8423篇 |
2018年 | 7858篇 |
2017年 | 6024篇 |
2016年 | 7837篇 |
2015年 | 10704篇 |
2014年 | 12349篇 |
2013年 | 12868篇 |
2012年 | 15434篇 |
2011年 | 14672篇 |
2010年 | 11513篇 |
2009年 | 15389篇 |
2008年 | 10957篇 |
2007年 | 10305篇 |
2006年 | 8521篇 |
2005年 | 7435篇 |
2004年 | 6655篇 |
2003年 | 5795篇 |
2002年 | 5940篇 |
2001年 | 6607篇 |
2000年 | 4170篇 |
1999年 | 8712篇 |
1998年 | 9959篇 |
1997年 | 10037篇 |
1996年 | 9328篇 |
1995年 | 9515篇 |
1994年 | 8868篇 |
1993年 | 8398篇 |
1992年 | 8600篇 |
1991年 | 8390篇 |
1990年 | 9107篇 |
1989年 | 8316篇 |
1988年 | 7494篇 |
1987年 | 6579篇 |
1986年 | 6029篇 |
1985年 | 5442篇 |
1984年 | 4166篇 |
1983年 | 3392篇 |
1982年 | 3650篇 |
1981年 | 3278篇 |
1980年 | 3191篇 |
1979年 | 3314篇 |
1978年 | 3004篇 |
1977年 | 2947篇 |
1976年 | 2758篇 |
1973年 | 2512篇 |
1972年 | 2858篇 |
1971年 | 2608篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Tohru Marunouchi Yoh-ichi Matsumoto Hiromi Hosoya Ken Okabayashi 《Molecular & general genetics : MGG》1987,206(1):60-65
Summary Autonomously replicating sequences (ARSs) were cloned from nuclear and mitochondrial DNA of D. melanogaster using YIp5, which is composed of pBR322 and the yeast ura3 gene, as the cloning vector and YNN27, a Ura- yeast strain as the recipient. The nucleotide sequences of six ARSs, two from nuclear bulk, two from the nuclear 1.688 satellite, and two from mitochondorial DNA, were determined. The relationship between the transformation frequency and the inclusion of the ARS core, 5
T
A
TT-TAT
A
G
TTT
T
A
3, of these fragments was analysed. All the ARSs contained an ARS core or a single base change of it. However, not all the fragments that contained a single base change of the ARS core were able to transform the recipient cells, suggesting that certain bases in the ARS core were not exchangeable. It is suggested by transformation experiments with subfragments that in addition to an ARS core, an ARS box which is located within 25 bp upstream of the ARS core and whose sequence is composed of 5TNT
G
A
AA 3, is necessary for autonomous replication. 相似文献
962.
Toshifumi Nakao Ichiro Yamato Yasuhiro Anraku 《Molecular & general genetics : MGG》1987,208(1-2):70-75
963.
OmpR and EnvZ are pleiotropic regulatory proteins: positive regulation of the tripeptide permease (tppB) of Salmonella typhimurium 总被引:9,自引:0,他引:9
M. M. Gibson E. M. Ellis K. A. Graeme-Cook C. F. Higgins 《Molecular & general genetics : MGG》1987,207(1):120-129
Summary The tppB locus of Salmonella typhimurium encodes the anaerobically-induced tripeptide permease. We have demonstrated that expression of tppB requires the function of the ompR and envZ gene products, originally identified as positive regulatory proteins required for the osmotic regulation of porin expression. Significantly, tppB expression is not osmotically regulated. We have also identified three additional genes whose expression depends on OmpR. Thus OmpR and EnvZ serve a more general regulatory role than has previously been supposed. This study provides the first detailed genetic analysis of the ompB locus of S. typhimurium. 相似文献
964.
965.
A. Tyagi J. Hermans J. Steppuhn Ch. Jansson F. Vater R. G. Herrmann 《Molecular & general genetics : MGG》1987,207(2-3):288-293
Summary Several cDNA clones encoding the 33 kDa protein associated with the photosynthetic water oxidation activity of spinach were sequenced. A 1208 bp insert of one of the clones encodes the entire 331 amino acid residues of the precursor protein including 84 amino acids (8.5 kDa) of the amino-terminal transit peptide, 49 bp of the 5 and 111 bp of the 3 untranslated segment of the mRNA. The 3 poly(A) tail starts 19 bp downstream from a putative polyadenylation signal, TATAAA. The hydrophilic mature protein consists of 247 amino acid residues corresponding to an Mr of 26.5 kDa, which is 6.5 kDa smaller than the value determined by SDS-polyacrylamide gel electrophoresis (33–34 kDa), and shows a certain degree of conservation with the putative Mn-complexing active sites of bacterial Mn-dependent superoxide dismutases. The anatomy of the unusually long transit sequence is discussed with regard to current concepts of protein import into and protein routein within the organelle. 相似文献
966.
967.
968.
969.
Karel Wernars Theo Goosen Bert M. J. Wennekes Klaas Swart Cees A. M. J. J. van den Hondel Henk W. J. van den Broek 《Molecular & general genetics : MGG》1987,209(1):71-77
Summary When a non-selected DNA sequence was added during the transformation of amdS320 deletion strains of Aspergillus nidulans with a vector containing the wild-type amdS gene the AmdS+ transformants were cotransformed at a high frequency. Cotransformation of an amdS320, trpC801 double mutant strain showed that both the molar ratio of the two vectors and the concentration of the cotransforming vector affected the cotransformation frequency. The maximum frequency obtained was defined by the gene chosen as selection marker for transformation. Cotransformation was used to induce a gene replacement in A. nidulans. An amdS320 strain was transformed to AmdS+ and cotransformed with a DNA fragment containing a fusion between a non-functional A. nidulans trpC gene and the Escherichia coli lacZ gene. Ten AmdS+, LacZ+ transformants with a Trp– mutant phenotype were selected. All of these strains could be transformed with a functional copy of the A. nidulans trpC gene, but only two strains yielded TrpC+ transformants which, with a low frequency, had a LacZ– phenotype. These latter transformants had also lost the AmdS+ phenotype. Southern blotting analysis of DNA from these transformants confirmed the inactivation of the wild-type trpC gene, but revealed that amdS vector sequences were also involved in the gene replacement events. 相似文献
970.
Amornrat Jearnpipatkul Hiroyuki Araki Yasuji Oshima 《Molecular & general genetics : MGG》1987,206(1):88-94
Summary A 2 m DNA-like plasmid, pSR1, isolated from a strain of Zygosaccharomyces rouxii has three coding frames, P, S and R. Insertional inactivation of R completely abolished the intramolecular recombination, and the defect was complemented by an intact R frame on a coexistent plasmid molecule. The P and S regions were also transactive and important, but not essential, for the stable maintenance of the plasmid molecules. Insertional disruption of the P frame suggested that it produces a protein factor. Similar insertional disruption of the S frame affected the plasmid stability in Z. rouxii and Saccharomyces cerevisiae hosts differently, depending on whether the inserted DNA fragment was a short 8 bp SalI linker or a long (2.2 kb) DNA fragment. Results strongly suggested that the S region encodes two factors, one RNA and the other a protein, and that the S protein is compatible with a sprecific hostfactor in Z. rouxii, but not in S. cerevisiae. In addition, a cis-acting locus, Z, was found at a site in the plasmid molecule where no distinct open reading frames were located. No long direct repeats or inverted repeats were observed in the Z region, such as are found in the REP3 locus of 2 m DNA. 相似文献