全文获取类型
收费全文 | 593篇 |
免费 | 45篇 |
专业分类
638篇 |
出版年
2023年 | 1篇 |
2022年 | 6篇 |
2021年 | 3篇 |
2020年 | 1篇 |
2019年 | 3篇 |
2018年 | 6篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 17篇 |
2014年 | 23篇 |
2013年 | 43篇 |
2012年 | 54篇 |
2011年 | 40篇 |
2010年 | 24篇 |
2009年 | 25篇 |
2008年 | 36篇 |
2007年 | 38篇 |
2006年 | 40篇 |
2005年 | 49篇 |
2004年 | 42篇 |
2003年 | 37篇 |
2002年 | 35篇 |
2001年 | 6篇 |
2000年 | 8篇 |
1999年 | 5篇 |
1998年 | 11篇 |
1997年 | 8篇 |
1996年 | 4篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有638条查询结果,搜索用时 0 毫秒
1.
The universal genetic code is determined by the aminoacylation of tRNAs. In spite of the universality of the code, there are barriers to aminoacylation across taxonomic domains. These barriers are thought to correlate with the co-segregation of sequences of synthetases and tRNAs into distinct taxonomic domains. By contrast, we show here examples of eukaryote-like synthetases that are found in certain prokaryotes. The associated tRNAs have retained their prokaryote-like character in each instance. Thus, co-segregation of domain-specific synthetases and tRNAs does not always occur. Instead, synthetases make adaptations of tRNA-protein contacts to cross taxonomic domains. 相似文献
2.
Megumi Fujisue Masao Sakai Kiyotaka Yamanat 《Development, growth & differentiation》1991,33(4):341-351
The specification of the dorsoventral axis in naturally polyspermic eggs of the Japanese newt, Cynops pyrrhogaster , was first examined by studies on the spatial relationship between the dorsal midline of the future body plan and the sperm entrance points (SEPs 1 ). On local insemination, the dorsal blastopore lip was usually found to be formed opposite the SEPs, as in anuran monospermic eggs. Next the movements of the subcortical layer and the cortex were analyzed. "Subcortical rotation" was observed, similar to that of Xenopus laevis eggs with respect to its timing and extent, and its direction was shown to predict the embryonic axis of the eggs. Thus, the dorsoventral axis was concluded to be determined by essentially the same mechanism in the newt as in Xenopus .
Owing to their large size and long first cell cycle, newt eggs appear to be suitable material for study of subcortical rotation, but their behavior is unique in that subcortical rotation occurs in only the vegetal hemisphere so that the subcortical layer stretches in the future dorsal side. Studies on the movement of Nile blue spots suggested that the cytoplasm under the cortex in newt eggs consists of two layers. 相似文献
Owing to their large size and long first cell cycle, newt eggs appear to be suitable material for study of subcortical rotation, but their behavior is unique in that subcortical rotation occurs in only the vegetal hemisphere so that the subcortical layer stretches in the future dorsal side. Studies on the movement of Nile blue spots suggested that the cytoplasm under the cortex in newt eggs consists of two layers. 相似文献
3.
Precise centromere mapping using a combination of repeat junction markers and chromatin immunoprecipitation-polymerase chain reaction 下载免费PDF全文
Luce AC Sharma A Mollere OS Wolfgruber TK Nagaki K Jiang J Presting GG Dawe RK 《Genetics》2006,174(2):1057-1061
Centromeres are difficult to map even in species where genetic resolution is excellent. Here we show that junctions between repeats provide reliable single-copy markers for recombinant inbred mapping within centromeres and pericentromeric heterochromatin. Repeat junction mapping was combined with anti-CENH3-mediated ChIP to provide a definitive map position for maize centromere 8. 相似文献
4.
Nucleotide sequences recognized by the AGAMOUS MADS domain of Arabidopsis thaliana in vitro 总被引:14,自引:2,他引:14
Hideaki Shiraishi Kiyotaka Okada Yoshiro Shimura 《The Plant journal : for cell and molecular biology》1993,4(2):385-398
The AGAMOUS gene of Arabidopsis thaliana is a homeotic gene involved in the development of stamens and carpels. This gene encodes a putative DNA-binding protein sharing a homologous region with the DNA-binding domains, MADS boxes, of yeast MCM1 and mammalian SRF. To examine the DNA-binding activity of the AGAMOUS protein, double-stranded oligonucleotides with random sequences of 40 bp in the central region were synthesized and mixed with the AGAMOUS MADS domain overproduced in Escherichia coli . Oligonucleotides which bound to the MADS domain were recovered by repeated immunoprecipitation with an antibody which recognizes the overproduced protein. From a comparison of the recovered DNA sequences, the consensus sequence of the high-affinity binding-sites for the AGAMOUS MADS domain was determined to be 5'-TT(A/T/G) CC(A/T)6 GG(A/T/C)AA-3'. DNase I footprinting and methylation interference experiments showed that the MADS domain binds to this motif. Comparisons with the binding-site sequences of other MADS-box proteins revealed that the MCM1 binding-sites in a-mating type-specific promoters of Saccharomyces cerevisiae show similarities with the binding-site sequence of the AGAMOUS MADS domain. A synthetic MCM1 binding-site in the upstream region of the STE2 gene is recognized by the AGAMOUS MADS domain. 相似文献
5.
Masaya Sakamoto Rimei Nishimura Taiga Irako Daisuke Tsujino Kiyotaka Ando Kazunori Utsunomiya 《Cardiovascular diabetology》2012,11(1):1-7
Background
The role of Lipoprotein (a) cholesterol {Lp(a)-C}as an additional and/or independent risk factor for cardiovascular disease (CVD) is not clear. We evaluated the associations between Lp(a)-C and other CVD risk factors including plasma lipoprotein concentrations and body fatness in overweight and obese African American children.Methods
A cross-sectional analysis was carried out using data from a sample of 121 African American children aged 9-11 years with Body Mass Index (BMI)'s greater than the 85th percentile. Body height, weight and waist circumference (WC) were measured. Fasting plasma concentrations of Lp(a)-C, Total cholesterol (TC), High density lipoprotein cholesterol (HDL-C), Very low density lipoprotein cholesterol (VLDL-C), Intermediate density lipoprotein cholesterol (IDL-C), Low density lipoprotein cholesterol (LDL-C), and Triacylglycerides (TAG) were analyzed using the vertical auto profile (VAP) cholesterol method.Results
After adjusting for child age, gender, and pubertal status, Lp(a)-C was positively associated with both HDL-C and TC, and negatively associated with VLDL-C and TAG. Including BMIz and WC as additional covariates did not alter the direction of the relationships between Lp(a)-C and the other lipoproteins. Finally, after adjusting for the other plasma lipoproteins, Lp(a)-C remained strongly associated with HDL-C, whereas the associations of Lp(a)-C with the other lipoproteins were not significant when HDL-C was simultaneously included in the regression models.Conclusions
Lp(a)-C was positively associated with HDL-C and this association is not influenced by other lipoprotein subclasses or by the degree of obesity. We conclude that Lp(a) cholesterol is not an independent risk factor for CVD in African American children. 相似文献6.
Yamaguchi T Yamazaki T Inoue M Mashida C Kawagoe K Ogawa M Shiga S Nakagawa Y Kishimoto T Kurane I Ouchi K Ohzeki T 《FEMS immunology and medical microbiology》2005,43(1):21-27
Simkania negevensis has been associated with bronchiolitis in infants and community-acquired pneumonia in adults. Reports of exposure to this microorganism are only available from Israel, North America and Western Europe. Currently, no standard method for diagnosis of S. negevensis infection has been established nor have prevalence rates been shown in Japan. For the first time we demonstrated the ability of the microimmunofluorescence (MIF) test to detect S. negevensis-specific immunoglobulin G and exposure to S. negevensis in Japan. The positive rate in healthy volunteers was 4.3% (25/588), with rates increasing with age. Results indicate the usefulness of the MIF test as a serological method for detecting S. negevensis-specific antibodies. A standard serological test for infection with S. negevensis is needed. 相似文献
7.
Synergistic induction of antigen-specific CTL by fusions of TLR-stimulated dendritic cells and heat-stressed tumor cells 总被引:1,自引:0,他引:1
Koido S Hara E Homma S Mitsunaga M Takahara A Nagasaki E Kawahara H Watanabe M Toyama Y Yanagisawa S Kobayashi S Yanaga K Fujise K Gong J Tajiri H 《Journal of immunology (Baltimore, Md. : 1950)》2007,179(7):4874-4883
Dendritic cell (DC)/tumor cell fusion cells (FCs) can induce potent CTL responses. The therapeutic efficacy of a vaccine requires the improved immunogenicity of both DCs and tumor cells. The DCs stimulated with the TLR agonist penicillin-killed Streptococcus pyogenes (OK-432; OK-DCs) showed higher expression levels of MHC class I and II, CD80, CD86, CD83, IL-12, and heat shock proteins (HSPs) than did immature DCs. Moreover, heat-treated autologous tumor cells displayed a characteristic phenotype with increased expression of HSPs, carcinoembryonic Ag (CEA), MUC1, and MHC class I (HLA-A2 and/or A24). In this study, we have created four types of FC preparation by alternating fusion cell partners: 1) immature DCs fused with unheated tumor cells; 2) immature DCs fused with heat-treated tumor cells; 3) OK-DCs fused with unheated tumor cells; and 4) OK-DCs fused with heat-treated tumor cells. Although OK-DCs fused with unheated tumor cells efficiently enhanced CTL induction, OK-DCs fused with heat-treated tumor cells were most active, as demonstrated by: 1) up-regulation of multiple HSPs, MHC class I and II, CEA, CD80, CD86, CD83, and IL-12; 2) activation of CD4+ and CD8+ T cells able to produce IFN- gamma at higher levels; 3) efficient induction of CTL activity specific for CEA or MUC1 or both against autologous tumor; and 4) superior abilities to induce CD107+ IFN-gamma+ CD8+ T cells and CD154+ IFN-gamma+ CD4+ T cells. These results strongly suggest that synergism between OK-DCs and heat-treated tumor cells enhances the immunogenicity of FCs and provides a promising means of inducing therapeutic antitumor immunity. 相似文献
8.
Takayuki Murata Satoshi Komoto Satoko Iwahori Jun Sasaki Hironori Nishitsuji Terumitsu Hasebe Kiyotaka Hoshinaga Yukio Yuzawa 《Microbiology and immunology》2021,65(1):10-16
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is causing the global coronavirus disease 2019 (COVID-19) pandemic. Because complete elimination of SARS-CoV-2 appears difficult, decreasing the risk of transmission is important. Treatment with 0.1 and 0.05 ppm ozone gas for 10 and 20 hr, respectively, decreased SARS-CoV-2 infectivity by about 95%. The magnitude of the effect was dependent on humidity. Treatment with 1 and 2 mg/L ozone water for 10 s reduced SARS-CoV-2 infectivity by about 2 and 3 logs, respectively. Our results suggest that low-dose ozone, in the form of gas and water, is effective against SARS-CoV-2. 相似文献
9.
Fumiya Noguchi Masaru Kawato Takao Yoshida Yoshihiro Fujiwara Katsunori Fujikura Kiyotaka Takishita 《The Journal of eukaryotic microbiology》2013,60(2):158-165
It has recently been unveiled that a wide variety of microbial eukaryotes (protists) occur in chemosynthetic ecosystems, such as hydrothermal vents and methane seeps. However, there is little knowledge regarding protists associated with endemic animals inhabiting these environments. In the present study, utilizing PCR techniques, we detected fragments of the small subunit ribosomal RNA gene (SSU rRNA gene) from a particular protist from gill tissues of a significant fraction of the vesicomyid clams Calyptogena soyoae and C. okutanii complex and of the mussel Bathymodiolus platifrons and B. japonicus, all of which harbor chemosynthetic endosymbiont bacteria and dominate methane seeps in Sagami Bay, Japan. Based on the phylogeny of SSU rRNA gene, the organism in question was shown to belong to Alveolata. It is noteworthy that this protist did not affiliate with any known alveolate group, although being deeply branched within the lineage of Syndiniales, for which the monophyly was constantly recovered, but not robustly supported. In addition, the protist detected using PCR followed by sequencing was localized within gill epithelial cells of B. platifrons with whole‐mount fluorescence in situ hybridization. This protist may be an endoparasite or an endocommensal of Calyptogena spp. and Bathymodiolus spp., and possibly have physiological and ecological impacts on these bivalves. 相似文献
10.
Kiyotaka Chinzei 《Historical Biology》2013,25(2):223-231
In spite of their sessile nature, oysters of the genera Crassostrea, Ostrea and their allies are adapted to live on soft muddy bottoms. To provide them with secure attachment and to keep the animal above the surface of the mud, these soft-bottom oysters employ two basic strategies. They tend to be gregarious in their settlement, thereby providing one another with surfaces for attachment, and they form lightweight shells. In addition to these common characteristics, these oysters have followed different morphological pathways to live successfully on soft muddy bottoms. There are at least four types of morphologies: (1) relay-type succession (shells pile up on one another over many generations); (2) konbo-type elongation (both valves grow vertically upwards, the dorsal hinge remaining at the base, near the umbo); (3) cone-type elongation (the attached valve grows upwards and the free valve acts as a lid); and (4) lightweight recliners (bulky shells with lightweight fabrics and cavities within them). Judging from the variety of taxa that have adopted it and the sizes of their populations, the relay-type is the most successful of these strategies. Recliners were particularly common during the Mesozoic. The relay-type appeared in the Late Jurassic, becoming the dominant adaptive strategy during the Cenozoic. 相似文献