全文获取类型
收费全文 | 921篇 |
免费 | 59篇 |
专业分类
980篇 |
出版年
2022年 | 6篇 |
2021年 | 10篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 10篇 |
2017年 | 9篇 |
2016年 | 11篇 |
2015年 | 22篇 |
2014年 | 28篇 |
2013年 | 81篇 |
2012年 | 45篇 |
2011年 | 56篇 |
2010年 | 39篇 |
2009年 | 42篇 |
2008年 | 66篇 |
2007年 | 68篇 |
2006年 | 58篇 |
2005年 | 55篇 |
2004年 | 68篇 |
2003年 | 66篇 |
2002年 | 54篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 17篇 |
1997年 | 8篇 |
1996年 | 4篇 |
1995年 | 8篇 |
1994年 | 3篇 |
1993年 | 8篇 |
1992年 | 11篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1977年 | 3篇 |
1976年 | 6篇 |
1975年 | 7篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1968年 | 2篇 |
排序方式: 共有980条查询结果,搜索用时 0 毫秒
61.
Kagawa W Kagawa A Saito K Ikawa S Shibata T Kurumizaka H Yokoyama S 《The Journal of biological chemistry》2008,283(35):24264-24273
Rad52 plays essential roles in homology-dependent double-strand break repair. Various studies have established the functions of Rad52 in Rad51-dependent and Rad51-independent repair processes. However, the precise molecular mechanisms of Rad52 in these processes remain unknown. In the present study we have identified a novel DNA binding site within Rad52 by a structure-based alanine scan mutagenesis. This site is closely aligned with the putative single-stranded DNA binding site determined previously. Mutations in this site impaired the ability of the Rad52-single-stranded DNA complex to form a ternary complex with double-stranded DNA and subsequently catalyze the formation of D-loops. We found that Rad52 introduces positive supercoils into double-stranded DNA and that the second DNA binding site is essential for this activity. Our findings suggest that Rad52 aligns two recombining DNA molecules within the first and second DNA binding sites to stimulate the homology search and strand invasion processes. 相似文献
62.
Two stereoisomers of a castasterone/ponasterone A hybrid compound, the (20R,22R) and (20R,22S)-isomers of 2alpha,3alpha,20,22-tetrahydroxy-5alpha-cholestan-6-one, were synthesized stereoselectively and their binding activity to the ecdysteroid receptor was determined. From the concentration-response curve for the inhibition of the incorporation of tritiated ponasterone A into ecdysteroid receptor containing insect cells, the concentration (IC50) required to inhibit 50% of the incorporation of radioactivity into cells was evaluated. The IC50 values of the (22R)- and (22S)-isomers were determined to be 0.30 and 38.9 microM against Kc cells, respectively, indicating that the (22R)-isomer is about 100 times more potent than the corresponding (22S)-isomer. IC50 values of these compounds against lepidopteran Sf-9 cells were determined to be 0.36 and 12.9 microM, respectively. The molting hormonal effect was examined in a Chilo suppressalis integument system and the 50% effective concentration for the stimulation of N-acetylglucosamine incorporation into the cultured integument was determined to be 2.7 microM for the (22R)-isomer, while the (22S)-isomer was inactive. On the other hand, both isomers did not show brassinolide-like activity in the rice lamina inclination assay. 相似文献
63.
Yamamoto K Okamoto M Yoko-o T Jigami Y 《Bioscience, biotechnology, and biochemistry》2003,67(4):927-929
64.
Nakano Ryohei Morita Taiki Okamoto Yuta Fujiwara Ayaka Yamanaka Takehiko Adachi-Hagimori Tetsuya 《BioControl》2021,66(3):407-418
BioControl - Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) is a zoophytophagous predator that feeds on plants as well as prey. Several non-crop host plant species have been used to maintain... 相似文献
65.
66.
Takehiko Yamamoto Junichi Kumada Teruo Sawai 《Bioscience, biotechnology, and biochemistry》2013,77(3):185-191
The purification of yeast invertase was attempted by application of the chromatographic method using Duolite C-10, a sulfonic acid cation exchange resin. This method was found to be extremely simple in process and significantly effective for the improvement of purity of the enzyme, compared with those other methods reported, hitherto. In the present paper, the procedure of the purification and some properties of the enzyme obtained thereby, are described, and some discussion of the implications is presented. 相似文献
67.
Kimikazu Itaya Juichiro Fukumoto Takehiko Yamamoto 《Bioscience, biotechnology, and biochemistry》2013,77(6):813-821
Some physical and chemical properties of urate oxidase (EC 1.7.3.3) isolated from the cells of Candida utilis were investigated. The molecular weight was estimated to be 1.2 × 105 by the equilibrium sedimentation and gel filtration methods. The isoelectric point was determined as 5.4 by the method of density electrofocusing. The enzyme showed a slight absorption at 410 mμ, and the absorbancy at this wave length was only 3% of that at 280 mμ. Contrary to urate oxidase from swine liver, the enzyme from yeast contained a negligible amount of copper, but it contained iron of nearly one atom per mole of the enzyme protein. The yeast urate oxidase was not inactivated by some chelators. However, it was easily inactivated with certain heavy metal ions such as Hg2+, and the inactivated enzyme was reactivated by the addition of thiols, indicating that the enzyme is a sulfhydryl enzyme. The inactivation of the enzyme with urea, on the other hand, was greatly accelerated by the addition of thiols, and some discussion was added to the results obtained. 相似文献
68.
Nobutake Hamada Takehiko Yamamoto Juichiro Fukumoto 《Bioscience, biotechnology, and biochemistry》2013,77(3):306-313
The nucleic acid metabolism in washed cells of Bacillus subtilis was investigated with special reference to amylase formation of the bacterium. On incubation of the suspension of the washed cells, purines, pyrimidines and their related compounds were observed in the medium. However, in the medium of the cells incubated with a calcium chelater, where no amylase formation occurred, were detected adenosine- and guanosine-monophosphate in addition to those described above. The addition of a calcium chelater was also found to decrease the quantity of the nucleic acids being involved in the lysozyme-sensitive fraction of the bacterial cells, suggesting the possibility that the metabolism of nucleic acids in this fraction is closely related to amylase formation of the cells. 相似文献
69.
Junko Morimoto Kento Hirabayashi Emu Mizumoto Takehiko Katsuno Yukihiro Morimoto 《Landscape and Ecological Engineering》2011,7(2):185-193
To develop an appropriate method of conservation for native Rhododendron sections Brachycalyx and Tsutsusi, the symbol of Satoyama, field experiments were performed in the dry granite region of Japan. When carpet-type landscape
of native rhododendrons was desired, all plants were cut at 20 cm above the ground level of all trees and shrubs, and herbs
and ferns were weeded (once and three times, respectively). When shrubby-type landscape of native rhododendrons was desired,
all plants, excluding native rhododendrons, were cut at 20 cm above the ground level of all trees and shrubs, herbs and ferns
were weeded, and litter was swept. After 3 years of monitoring of the percentage and depth of crowns with flower buds, the
following major results were obtained: Cutting all plants excluding native rhododendrons was effective to maintain the depth
of crowns with flower buds. However, weeding and sweeping of litter on the ground caused desiccation of surface soil, which
induced a transitory decrease in the percentage of crowns with flower buds. One weeding was effective in maintaining the depth
of crowns with flower buds; however, the second and third weedings had no distinct effect. In dry granite regions, considerable
attention to desiccation of surface soil is critical, as opposed to limiting attention to maintenance of sunlight as is common
practice. 相似文献
70.
Concerted evolution describes the unusual evolutionary pattern exhibited by certain repetitive sequences, whereby all the repeats are maintained in the genome with very similar sequences but differ between related species. The pattern of concerted evolution is thought to result from continual turnover of repeats by recombination, a process known as homogenization. Approaches to studying concerted evolution have largely been observational because of difficulties investigating repeat evolution in an experimental setting with large arrays of identical repeats. Here, we establish an experimental evolution approach to look at the rate and dynamics of concerted evolution in the ribosomal DNA (rDNA) repeats. A small targeted mutation was made in the spacer of a single rDNA unit in Saccharomyces cerevisiae so we could monitor the fate of this unit without the need for a selectable marker. The rate of loss of this single unit was determined, and the frequency of duplication was also estimated. The results show that duplication and deletion events occur at similar rates and are very common: An rDNA unit may be gained or lost as frequently as once every cell division. Investigation of the spatial dynamics of rDNA turnover showed that when the tagged repeat unit was duplicated, the copy predominantly, but not exclusively, ended up near to the tagged repeat. This suggests that variants in the rDNA spread in a semiclustered fashion. Surprisingly, large deletions that remove a significant fraction of total rDNA repeats were frequently found. We propose these large deletions are a driving force of concerted evolution, acting to increase homogenization efficiency over-and-above that afforded by turnover of individual rDNA units. Thus, the results presented here enhance our understanding of concerted evolution by offering insights into both the spatial and temporal dynamics of the homogenization process and suggest an important new aspect in our understanding of concerted evolution. 相似文献