全文获取类型
收费全文 | 757篇 |
免费 | 59篇 |
专业分类
816篇 |
出版年
2023年 | 7篇 |
2022年 | 12篇 |
2021年 | 15篇 |
2020年 | 8篇 |
2019年 | 11篇 |
2018年 | 13篇 |
2017年 | 15篇 |
2016年 | 25篇 |
2015年 | 43篇 |
2014年 | 31篇 |
2013年 | 43篇 |
2012年 | 56篇 |
2011年 | 52篇 |
2010年 | 27篇 |
2009年 | 35篇 |
2008年 | 51篇 |
2007年 | 57篇 |
2006年 | 42篇 |
2005年 | 46篇 |
2004年 | 46篇 |
2003年 | 31篇 |
2002年 | 26篇 |
2001年 | 11篇 |
2000年 | 14篇 |
1999年 | 10篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1969年 | 1篇 |
1937年 | 1篇 |
1932年 | 1篇 |
排序方式: 共有816条查询结果,搜索用时 15 毫秒
1.
Tomohiro Hamasaki Takahiro Matsumoto Naoya Sakamoto Akiko Shimahara Shiori Kato Ayumi Yoshitake Ayumi Utsunomiya Hisayoshi Yurimoto Esteban C. Gabazza Tadaaki Ohgi 《Nucleic acids research》2013,41(12):e126
Radioisotopes and fluorescent compounds are frequently used for RNA labeling but are unsuitable for clinical studies of RNA drugs because of the risk from radiation exposure or the nonequivalence arising from covalently attached fluorophores. Here, we report a practical phosphoramidite solid-phase synthesis of 18O-labeled RNA that avoids these disadvantages, and we demonstrate its application to quantification and imaging. The synthesis involves the introduction of a nonbridging 18O atom into the phosphate group during the oxidation step of the synthetic cycle by using 18O water as the oxygen donor. The 18O label in the RNA was stable at pH 3–8.5, while the physicochemical and biological properties of labeled and unlabeled short interfering RNA were indistinguishable by circular dichroism, melting temperature and RNA-interference activity. The 18O/16O ratio as measured by isotope ratio mass spectrometry increased linearly with the concentration of 18O-labeled RNA, and this technique was used to determine the blood concentration of 18O-labeled RNA after administration to mice. 18O-labeled RNA transfected into human A549 cells was visualized by isotope microscopy. The RNA was observed in foci in the cytoplasm around the nucleus, presumably corresponding to endosomes. These methodologies may be useful for kinetic and cellular-localization studies of RNA in basic and pharmaceutical studies. 相似文献
2.
Separation of toxic activity and ADP-ribosylation activity of botulinum neurotoxin D 总被引:1,自引:0,他引:1
Neurotoxin from Clostridium botulinum type D strain South African (neurotoxin D) has shown ADP-ribosylation activity as well as toxic activity (Matsuoka, I., Sakuma, H., Syuto, B., Moriishi, K., Kubo, S., and Kurihara, K. (1989) J. Biol. Chem. 264, 706-712). Separation of these activities from each other was attempted by means of gel filtration, hydroxylapatite column chromatography, or immunoaffinity chromatography. Approximately 90% of toxic activity was recovered in each chromatography. Although ADP-ribosylation activity was incompletely separated from neurotoxin D by gel filtration, it was separated by hydroxylapatite column chromatography. In immunoaffinity chromatography with a column of Sepharose 4B coupling antibodies against botulinum ADP-ribosyltransferase, no ADP-ribosylation activity was detected by autoradiography in the unabsorbed toxic fraction. These results indicate that neurotoxin D does not have ADP-ribosylation activity. 相似文献
3.
Ayumi Ohsaki Yoshihisa Kasetani Yukihiro Asaka Kozo Shibata Takashi Tokoroyama Takashi Kubota 《Phytochemistry》1991,30(12):4075-4077
Three trans-clerodane diterpenoids, pilosanol A, B and C, the last compound being a glucoside, have been isolated from the roots of Portulaca pilosa. They show a marked contrast in skeletal type with the constituents of aerial part. Evolutionary changes in the biosynthetic abilities of Portulaca species is discussed. 相似文献
4.
Y Tsukada K Ohkawa N Hibi K Tsuzuki K Oguma H Satoh 《Cancer biochemistry biophysics》1989,10(3):247-256
A monoclonal mouse antibody (MoHG) was produced using in vitro cultured AH66R tumor cells treated with cholesteryl hemisuccinate as an immunogen. The antibody identified a 90 kd membrane glycoprotein (HG-90) which is expressed on in vitro cultured hepatoma cell lines AH66 and AH66R. A monoclonal antibody was prepared to the anthracycline drug daunomycin, and it also reacted with adriamycin. A fusion was made of the hybridoma HG-90 with the hybridoma which recognized daunomycin/adriamycin. This bispecific hybridoma A8C recognized both determinants. We studied the therapeutic effect of the A8C bispecific antibody with adriamycin treatment and compared it to the effect of the bispecific antibody to which adriamycin had been conjugated via an albumin (Alb) bridge. The therapy model used was the tumor AH66R in Donryu rats. Tumor bearing rats had their subcutaneous tumors resected on day 10, a time when distant metastases were present. After the surgical resection of the tumor the rats were injected intravenously for two cycles with the bispecific antibodies, followed by the administration of adriamycin (ADR) or MoHG.Alb.ADR conjugates. A slight therapeutic effect occurred with either MoHG or ADR alone but treatment with the bispecific antibody followed by the administration of ADR or with the MoHG.Alb.ADR conjugates significantly prolonged survival, with 60% of the treated animals being "tumor free" when sacrificed on day 80. Lower serum concentrations of alphafetoprotein were observed with the bispecific antibody and drug treatment. This suggests that the bispecific antibody/drug treatment is potentially more beneficial in the suppression of distant metastases than the MoHG.Alb.ADR conjugate. This may be due to an increase in the local drug concentration of unmodified adriamycin. 相似文献
5.
Tetsuya Oguma Asahi Matsuyama Mamoru Kikuchi Eiichi Nakano 《Applied microbiology and biotechnology》1993,39(2):197-203
The gene for cyclomaltodextrinase (CDase; EC 3.2.1.54) from Bacillus sphaericus E-244 was cloned in the recombinant plasmid pCD629. Sequencing a portion of pCD629 revealed a unique open reading frame of 1,773 nucleotides coding for a 591-amino-acid polypeptide. The deduced polypeptide sequence showed about 50% homology with that of a neopullulanase, and was slightly homologous to those of the cyclodextrin glucanotransferases and the -amylases. The optimum pH, specific activity and K
m value for -cyclodextrin of the CDase that has been produced in Escherichia coli cells were 8.0, 16.4 units/mg protein, and 0.41 mm, respectively. These values were almost identical to those from B. sphaericus E-244.
Correspondence to: T. Oguma 相似文献
6.
Sakaba Tomoka Soejima Akiko Fujii Shinji Ikeda Hajime Iwasaki Takaya Saito Hiroaki Suyama Yoshihisa Matsuo Ayumi Kozhevnikov Andrey E. Kozhevnikova Zoya V. Wang Hongfeng Wang Siqi Pak Jae-Hong Fujii Noriyuki 《Journal of plant research》2023,136(4):437-452
Journal of Plant Research - A group of temperate grassland plant species termed the “Mansen elements” occurs in Japan and is widely distributed in the grasslands of continental East... 相似文献
7.
8.
Two experiments were performed with the aim of clarifying the genetic basis of variation in the number of primary spermatocytes per cyst in the B12 strain of Drosophila virilis and identifying the chromosome responsible for the variation. First, crosses between B12, showing a mean cell number of 11.81, and strain TK with a mean of 7.91, were performed. From the results obtained, it was considered that there were two factors, i.e., a recessive gene and certain modifiers, which shifted the cell number toward a higher value in B12. Second, chromosomal analysis with a marker strain and the B12 strain revealed that the third chromosome of B12 was responsible for the major effect of changing the primary spermatocyte number, although this chromosome did not exert a sufficient effect alone, and furthermore that at least one of the modifiers located on the second chromosome. 相似文献
9.
Production of a Doubly Chiral Compound, (4R,6R)-4-Hydroxy-2,2,6-Trimethylcyclohexanone, by Two-Step Enzymatic Asymmetric Reduction 总被引:1,自引:0,他引:1 下载免费PDF全文
Masaru Wada Ayumi Yoshizumi Yumiko Noda Michihiko Kataoka Sakayu Shimizu Hiroshi Takagi Shigeru Nakamori 《Applied microbiology》2003,69(2):933-937
A practical enzymatic synthesis of a doubly chiral key compound, (4R,6R)-4-hydroxy-2,2,6-trimethylcyclohexanone, starting from the readily available 2,6,6-trimethyl-2-cyclohexen-1,4-dione is described. Chirality is first introduced at the C-6 position by a stereoselective enzymatic hydrogenation of the double bond using old yellow enzyme 2 of Saccharomyces cerevisiae, expressed in Escherichia coli, as a biocatalyst. Thereafter, the carbonyl group at the C-4 position is reduced selectively and stereospecifically by levodione reductase of Corynebacterium aquaticum M-13, expressed in E. coli, to the corresponding alcohol. Commercially available glucose dehydrogenase was also used for cofactor regeneration in both steps. Using this two-step enzymatic asymmetric reduction system, 9.5 mg of (4R,6R)-4-hydroxy-2,2,6-trimethylcyclohexanone/ml was produced almost stoichiometrically, with 94% enantiomeric excess in the presence of glucose, NAD+, and glucose dehydrogenase. To our knowledge, this is the first report of the application of S. cerevisiae old yellow enzyme for the production of a useful compound. 相似文献
10.
Shotaro Hirase Ayumi Tezuka Atsushi J. Nagano Mana Sato Sho Hosoya Kiyoshi Kikuchi Wataru Iwasaki 《Evolution; international journal of organic evolution》2021,75(1):176-194
Hybridization between divergent lineages generates new allelic combinations. One mechanism that can hinder the formation of hybrid populations is mitonuclear incompatibility, that is, dysfunctional interactions between proteins encoded in the nuclear and mitochondrial genomes (mitogenomes) of diverged lineages. Theoretically, selective pressure due to mitonuclear incompatibility can affect genotypes in a hybrid population in which nuclear genomes and mitogenomes from divergent lineages admix. To directly and thoroughly observe this key process, we de novo sequenced the 747‐Mb genome of the coastal goby, Chaenogobius annularis, and investigated its integrative genomic phylogeographics using RNA‐sequencing, RAD‐sequencing, genome resequencing, whole mitogenome sequencing, amplicon sequencing, and small RNA‐sequencing. Chaenogobius annularis populations have been geographically separated into Pacific Ocean (PO) and Sea of Japan (SJ) lineages by past isolation events around the Japanese archipelago. Despite the divergence history and potential mitonuclear incompatibility between these lineages, the mitogenomes of the PO and SJ lineages have coexisted for generations in a hybrid population on the Sanriku Coast. Our analyses revealed accumulation of nonsynonymous substitutions in the PO‐lineage mitogenomes, including two convergent substitutions, as well as signals of mitochondrial lineage‐specific selection on mitochondria‐related nuclear genes. Finally, our data implied that a microRNA gene was involved in resolving mitonuclear incompatibility. Our integrative genomic phylogeographic approach revealed that mitonuclear incompatibility can affect genome evolution in a natural hybrid population. 相似文献