全文获取类型
收费全文 | 1447篇 |
免费 | 77篇 |
出版年
2021年 | 12篇 |
2020年 | 6篇 |
2019年 | 10篇 |
2018年 | 16篇 |
2017年 | 16篇 |
2016年 | 22篇 |
2015年 | 38篇 |
2014年 | 41篇 |
2013年 | 109篇 |
2012年 | 90篇 |
2011年 | 103篇 |
2010年 | 65篇 |
2009年 | 62篇 |
2008年 | 113篇 |
2007年 | 100篇 |
2006年 | 90篇 |
2005年 | 77篇 |
2004年 | 109篇 |
2003年 | 100篇 |
2002年 | 92篇 |
2001年 | 9篇 |
2000年 | 15篇 |
1999年 | 19篇 |
1998年 | 17篇 |
1997年 | 19篇 |
1996年 | 20篇 |
1995年 | 18篇 |
1994年 | 10篇 |
1993年 | 9篇 |
1992年 | 11篇 |
1991年 | 11篇 |
1990年 | 10篇 |
1989年 | 3篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1980年 | 11篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1972年 | 2篇 |
1963年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有1524条查询结果,搜索用时 15 毫秒
1.
Compression wood (CW) contains higher quantities of β-1-4-galactan than does normal wood (NW). However, the physiological
roles and ultrastructural distribution of β-1-4-galactan during CW formation are still not well understood. The present work
investigated deposition of β-1-4-galactan in differentiating tracheids of Cryptomeria japonica during CW formation using an immunological probe (LM5) combined with immunomicroscopy. Our immunolabeling studies clearly
showed that differences in the distribution of β-1-4-galactan between NW (and opposite wood, OW) and CW are initiated during
the formation of the S1 layer. At this stage, CW was strongly labeled in the S1 layer, whereas no label was observed in the S1 layer of NW and OW. Immunogold labeling showed that β-1-4-galactan in the S1 layer of CW tracheids significantly decreased during the formation of the S2 layer. Most β-1-4-galactan labeling was present in the outer S2 region in mature CW tracheids, and was absent in the inner S2 layer that contained helical cavities in the cell wall. In addition, delignified CW tracheids showed significantly more labeling
of β-1-4-galactan in the secondary cell wall, suggesting that lignin is likely to mask β-1-4-galactan epitopes. The study
clearly showed that β-1-4-galactan in CW was mainly deposited in the outer portion of the secondary cell wall, indicating
that its distribution may be spatially consistent with lignin distribution in CW tracheids of Cryptomeria japonica. 相似文献
2.
3.
Bacteriophages (or phages) play major roles in the evolution of bacterial pathogens via horizontal gene transfer. Multiple phages are often integrated in a host chromosome as prophages, not only carrying various novel virulence-related genetic determinants into host bacteria but also providing various possibilities for prophage-prophage interactions in bacterial cells. In particular, Escherichia coli strains such as Shiga toxin (Stx)-producing E. coli (STEC) and enteropathogenic E. coli (EPEC) strains have acquired more than 10 prophages (up to 21 prophages), many of which encode type III secretion system (T3SS) effector gene clusters. In these strains, some prophages are present at a single locus in tandem, which is usually interpreted as the integration of phages that use the same attachment (att) sequence. Here, we present phages integrating into T3SS effector gene cluster-associated loci in prophages, which are widely distributed in STEC and EPEC. Some of the phages integrated into prophages are Stx-encoding phages (Stx phages) and have induced the duplication of Stx phages in a single cell. The identified attB sequences in prophage genomes are apparently derived from host chromosomes. In addition, two or three different attB sequences are present in some prophages, which results in the generation of prophage clusters in various complex configurations. These phages integrating into prophages represent a medically and biologically important type of inter-phage interaction that promotes the accumulation of T3SS effector genes in STEC and EPEC, the duplication of Stx phages in STEC, and the conversion of EPEC to STEC and that may be distributed in other types of E. coli strains as well as other prophage-rich bacterial species. 相似文献
4.
Keiji Harashima Nobuo Tsuchida Teruo Tanaka Junsaku Nagatsu 《Bioscience, biotechnology, and biochemistry》2013,77(4):481-489
A water-insoluble red antibiotic pigment was isolated from mycelia of a strain of Streptomyces. It was found that the pigment is a new C25-prodigiosin-analogue and the authors propose to designate it prodigiosin-25 C. The chemical structure (XI) has been deduced from visible absorption spectra, NMR spectra, mass spectra and analysis of degradation products of the pigment. 相似文献
5.
Takano Hiroyuki; Umeda Keiji; Tahara Sanae; Takahashi Nobutaka 《Plant & cell physiology》1976,17(2):239-245
The availability of brewery pale malt as a substrate for gibberellinbioassay was investigated. GA3 at the concentration of 0.001to 1 µg/ml caused an increase in a-amylase activity inpale malt under aerobic incubation, while no increase was observedunder anaerobic conditions. Pale malt heated at 130°C for2 hr showed no increase in a-amylase activity in the presenceof GA3. Although the mechanism for the enhancement of a-amylaseactivity in pale malt by GA3 is not clear, it is evident thatthis phenomena can be used in bioassay of gibberellins. Experimentalconditions for the bioassay using pale malt are described. Withthis method, the enhancement of a-amylase activity by differentgibberellins was: GA3>GA4>GA20 (inactive). (Received October 16, 1975; ) 相似文献
6.
The polymeric cobalt(II) porphyrin complexes were prepared from cobalt(II) protoporphyrin IX dimethyl ester(Co(II)P) and copolymers of 4-vinylpyridine and styrene(PSP), and their binding ability of molecular oxygen was studied in toluene solution. The five- and six-coordinate structure of CoP-PSP complexes were confirmed by esr spectra. The esr parameters for the CoP-PSP complexes were not affected by the molecular weight and the vinylpyridine-unit content of PSP-ligand. The 1:1 dioxygen-Co complex was reversibly formed when the solution of CoP-PSP was exposed to oxygen atmosphere at low temperature. While the visible spectra and esr parameters for the dioxygen complexes of CoP-PSP were the same as those of the CoP-pyridine complex, the equilibrium constant for the oxygen binding increased with the vinylpyridine-unit content of the PSP-ligand. The larger entropy change was observed for the oxygenation in the CoP-PSP system especially, of which the vinylpyridine-unit content was large. 相似文献
7.
Satoshi Shuto Hiromichi Ito Takumi Obara Keiji Nakagami Masao Yaso Satoshi Yaginuma 《Nucleosides, nucleotides & nucleic acids》2013,32(2-4):437-446
Abstract A novel series of neplanocin analogues, 6′-(3-sn-phosphatidyl)neplanocin As bearing a variety of fatty acyl or alkyl residues in the glyceride moiety (2b-2h), were synthesized by means of phospholipase D-catalyzed transphosphatidylation. Among them, 2b, 2c, and 2e each exhibited significant antitumor effect against P388 leukemia in mice, which evidently surpassed that of parent compound neplanocin A. 相似文献
8.
The inactivation of papain brought about by low concentration of urea or guanidine hydrochloride was found to be a non-competitive type and that of cyanate ion to be a mixed type. The results are presented as Lineweaver-Burk plots.These inactivations are not due to a change in the secondary structure of papain molecule as a result of the measurements of optical rotatory dispersion, circular dichroism, and UV-difference spectra. 相似文献
9.
Masato Ohtsuka Hiromi Miura Keiji Mochida Michiko Hirose Ayumi Hasegawa Atsuo Ogura Ryuta Mizutani Minoru Kimura Ayako Isotani Masahito Ikawa Masahiro Sato Channabasavaiah B Gurumurthy 《BMC genomics》2015,16(1)
Background
The pronuclear injection (PI) is the simplest and widely used method to generate transgenic (Tg) mice. Unfortunately, PI-based Tg mice show uncertain transgene expression due to random transgene insertion in the genome, usually with multiple copies. Thus, typically at least three or more Tg lines are produced by injecting over 200 zygotes and the best line/s among them are selected through laborious screening steps. Recently, we developed technologies using Cre-loxP system that allow targeted insertion of single-copy transgene into a predetermined locus through PI. We termed the method as PI-based Targeted Transgenesis (PITT). A similar method using PhiC31-attP/B system was reported subsequently.Results
Here, we developed an improved-PITT (i-PITT) method by combining Cre-loxP, PhiC31-attP/B and FLP-FRT systems directly under C57BL/6N inbred strain, unlike the mixed strain used in previous reports. The targeted Tg efficiency in the i-PITT typically ranged from 10 to 30%, with 47 and 62% in two of the sessions, which is by-far the best Tg rate reported. Furthermore, the system could generate multiple Tg mice simultaneously. We demonstrate that injection of up to three different Tg cassettes in a single injection session into as less as 181 zygotes resulted in production of all three separate Tg DNA containing targeted Tg mice.Conclusions
The i-PITT system offers several advantages compared to previous methods: multiplexing capability (i-PITT is the only targeted-transgenic method that is proven to generate multiple different transgenic lines simultaneously), very high efficiency of targeted-transgenesis (up to 62%), significantly reduces animal numbers in mouse-transgenesis and the system is developed under C57BL/6N strain, the most commonly used pure genetic background. Further, the i-PITT system is freely accessible to scientific community.Electronic supplementary material
The online version of this article (doi:10.1186/s12864-015-1432-5) contains supplementary material, which is available to authorized users. 相似文献10.
Munetaka Ozeki Adeeb Salah Wulamujiang Aini Keiji Tamaki Hironori Haga Aya Miyagawa-Hayashino 《PloS one》2015,10(8)
The biological significance of STK17A, a serine/threonine kinase, in the liver is not known. We analyzed STK17A expression in HepG2 cells and human liver tissue. Accordingly, we investigated whether STK17A could help in identifying earlier changes during the evolution of chronic rejection (CR) after liver transplantation. RT-PCR and immunofluorescence were used to analyze STK17A expression in HepG2 cells. Antibody microarray was performed using human liver samples from CR and healthy donors. Immunohistochemistry was used to verify the clinical utility of STK17A on sequential biopsies for the subsequent development of CR. A novel short isoform of STK17A was found in HepG2 cells. STK17A was localized in the nuclei and bile canaliculi in HepG2 cells and human livers. Microarray of STK17A revealed its decrease in failed liver allografts by CR. During the evolution of CR, the staining pattern of bile canalicular STK17A gradually changed from diffuse linear to focal intermittent. The focal intermittent staining pattern was observed before the definite diagnosis of CR. In conclusion, the present study was the first to find localization of STK17A in normal bile canaliculi. Abnormal expression and localization of STK17A were associated with CR of liver allografts since the early stage of the rejection process. 相似文献