全文获取类型
收费全文 | 400篇 |
免费 | 20篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 20篇 |
2020年 | 14篇 |
2019年 | 9篇 |
2018年 | 11篇 |
2017年 | 10篇 |
2016年 | 14篇 |
2015年 | 27篇 |
2014年 | 31篇 |
2013年 | 27篇 |
2012年 | 36篇 |
2011年 | 21篇 |
2010年 | 18篇 |
2009年 | 6篇 |
2008年 | 16篇 |
2007年 | 12篇 |
2006年 | 5篇 |
2005年 | 15篇 |
2004年 | 6篇 |
2003年 | 5篇 |
2002年 | 7篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 2篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1974年 | 2篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1950年 | 1篇 |
1933年 | 1篇 |
排序方式: 共有420条查询结果,搜索用时 78 毫秒
151.
Makio Shibano Ayaka Misaka Kayoko Sugiyama Masahiko Taniguchi Kimiye Baba 《Phytochemistry letters》2012,5(2):304-308
Two new steroid glycosides, stauntosaponins A (1) and B (2), were isolated from Cynanchum stauntonii (Decne.) Schltr.ex Levl. (Asclepiadaceae) together with five known compounds, anhydrohirundigenin monothevetoside, glaucogenin C mono-d-thevetoside, hirundoside A, cynatratoside A, and glaucogenin C. Stauntosaponins A and B were formulated as 3-O-β-d-oleandropyranosyl-14, 16: 15, 20: 18, 20-triepoxy-14, 15-secopregn-4, 6, 8(14)-triene (1) and 3-O-β-d-thevetopyranosyl-14, 16: 15, 20: 18, 20-triepoxy-14, 15-secopregn-4, 6, 8(14)-triene (2). Compounds 1 and 2 showed moderate inhibitory activities against Na+/K+-ATPase with IC50 values of 21 and 29 μM, respectively, whereas ouabain as a positive control displayed an IC50 value of 3.5 μM. 相似文献
152.
Murakami S Horimoto T Mai le Q Nidom CA Chen H Muramoto Y Yamada S Iwasa A Iwatsuki-Horimoto K Shimojima M Iwata A Kawaoka Y 《Journal of virology》2008,82(21):10502-10509
H5N1 influenza A viruses are exacting a growing human toll, with more than 240 fatal cases to date. In the event of an influenza pandemic caused by these viruses, embryonated chicken eggs, which are the approved substrate for human inactivated-vaccine production, will likely be in short supply because chickens will be killed by these viruses or culled to limit the worldwide spread of the infection. The Madin-Darby canine kidney (MDCK) cell line is a promising alternative candidate substrate because it supports efficient growth of influenza viruses compared to other cell lines. Here, we addressed the molecular determinants for growth of an H5N1 vaccine seed virus in MDCK cells, revealing the critical responsibility of the Tyr residue at position 360 of PB2, the considerable requirement for functional balance between hemagglutinin (HA) and neuraminidase (NA), and the partial responsibility of the Glu residue at position 55 of NS1. Based on these findings, we produced a PR8/H5N1 reassortant, optimized for this cell line, that derives all of its genes for its internal proteins from the PR8(UW) strain except for the NS gene, which derives from the PR8(Cambridge) strain; its N1 NA gene, which has a long stalk and derives from an early H5N1 strain; and its HA gene, which has an avirulent-type cleavage site sequence and is derived from a circulating H5N1 virus. Our findings demonstrate the importance and feasibility of a cell culture-based approach to producing seed viruses for inactivated H5N1 vaccines that grow robustly and in a timely, cost-efficient manner as an alternative to egg-based vaccine production. 相似文献
153.
Detecting latitudinal and altitudinal expansion of invasive bamboo Phyllostachys edulis and Phyllostachys bambusoides (Poaceae) in Japan to project potential habitats under 1.5°C–4.0°C global warming
下载免费PDF全文
![点击此处可从《Ecology and evolution》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Kohei Takenaka Takano Kenshi Hibino Ayaka Numata Michio Oguro Masahiro Aiba Hideo Shiogama Izuru Takayabu Tohru Nakashizuka 《Ecology and evolution》2017,7(23):9848-9859
Rapid expansion of exotic bamboos has lowered species diversity in Japan's ecosystems by hampering native plant growth. The invasive potential of bamboo, facilitated by global warming, may also affect other countries with developing bamboo industries. We examined past (1975–1980) and recent (2012) distributions of major exotic bamboos (Phyllostachys edulis and P. bambusoides) in areas adjacent to 145 weather stations in central and northern Japan. Bamboo stands have been established at 17 sites along the latitudinal and altitudinal distributional limit during the last three decades. Ecological niche modeling indicated that temperature had a strong influence on bamboo distribution. Using mean annual temperature and sun radiation data, we reproduced bamboo distribution (accuracy = 0.93 and AUC (area under the receiver operating characteristic curve) = 0.92). These results infer that exotic bamboo distribution has shifted northward and upslope, in association with recent climate warming. Then, we simulated future climate data and projected the climate change impact on the potential habitat distribution of invasive bamboos under different temperature increases (i.e., 1.5°C, 2.0°C, 3.0°C, and 4.0°C) relative to the preindustrial period. Potential habitats in central and northern Japan were estimated to increase from 35% under the current climate (1980–2000) to 46%–48%, 51%–54%, 61%–67%, and 77%–83% under 1.5°C, 2.0°C, 3.0°C, and 4.0°C warming levels, respectively. These infer that the risk areas can increase by 1.3 times even under a 1.5°C scenario and expand by 2.3 times under a 4.0°C scenario. For sustainable ecosystem management, both mitigation and adaptation are necessary: bamboo planting must be carefully monitored in predicted potential habitats, which covers most of Japan. 相似文献
154.
155.
Ishimaru Masanori Yoshizawa-Kumagaye Kumiko Kubo Shigeru Kitani Tetsuya Chino Naoyoshi- Kangawa Kenji Kimura Terutoshi 《International journal of peptide research and therapeutics》2003,10(1):41-50
Summary Rat ghrelin, a 28-amino acid residue peptide with an octanoyl group at the side chain of Ser3, was synthesized chemically
by applying Fmoc/
t
Bu strategy. An ester linkage between octanoic acid and the hydroxyl function of Ser3 was found to be maintained without serious
damage during the final deprotection with trifluoroacetic acid (TFA). The most notable finding was the counter-ion-dependent
stability change of the octanoyl moiety in the molecule. After consolidation of the counter-ion to TFA (TFA form), the octanoyl
group persisted stably upon dissolution in water, whereas in the case of the acetate-form peptide, both de-octanoylation and
dehydration (formation of the dehydro-Ala residue) occurred in aqueous solution at the same Ser3 residue. The amounts of these
degraded products varied with factors such as solvent, temperature and times of lyophilization. These experimental findings
lay the basis for performing the bioassay of ghrelin, which has an octanoyl moiety involved in its numerous biological activities
thus far revealed. 相似文献
156.
Euki Yazaki Akinori Yabuki Ayaka Imaizumi Keitaro Kume Tetsuo Hashimoto Yuji Inagaki 《Open biology》2022,12(4)
By clarifying the phylogenetic positions of ‘orphan’ protists (unicellular micro-eukaryotes with no affinity to extant lineages), we may uncover the novel affiliation between two (or more) major lineages in eukaryotes. Microheliella maris was an orphan protist, which failed to be placed within the previously described lineages by pioneering phylogenetic analyses. In this study, we analysed a 319-gene alignment and demonstrated that M. maris represents a basal lineage of one of the major eukaryotic lineages, Cryptista. We here propose a new clade name ‘Pancryptista’ for Cryptista plus M. maris. The 319-gene analyses also indicated that M. maris is a key taxon to recover the monophyly of Archaeplastida and the sister relationship between Archaeplastida and Pancryptista, which is collectively called ‘CAM clade’ here. Significantly, Cryptophyceae tend to be attracted to Rhodophyta depending on the taxon sampling (ex., in the absence of M. maris and Rhodelphidia) and the particular phylogenetic ‘signal’ most likely hindered the stable recovery of the monophyly of Archaeplastida in previous studies. 相似文献
157.
Ayaka Minoshima Donald M. Walker Shuhei Takemoto Tsuyoshi Hosoya Allison K. Walker Seiju Ishikawa Yuuri Hirooka 《Mycoscience》2019,60(1):31-39
Since 2010, an unknown fungus in the Gnomoniaceae has been found on overwintered leaves and petioles of Styrax obassia (Styracaceae) in Japan. This fungus is characterized by dark brown immersed or partially erumpent ascomata with long necks and fusiform to obovoid asci each with an acute or long tapering stipe. Each ascus bears eight fusiform to filiform ascospores. Our morphological observation and phylogenetic analyses based on the markers LSU, rpb2, and tef-1α indicated that this is a new monotypic genus in the Gnomoniaceae (Diaporthales), and Tenuignomonia styracis gen. et sp. nov. was descried herein. Members of the Gnomoniaceae are commonly isolated as endophytes, saprobes, and plant pathogens from a broad diversity of herbaceous, shade tree, and agriculturally significant plants. We thus carried out a pathogenicity test to determine if T. styracis is the causative agent of leaf blotch on S. obassia. One week after inoculation, this fungus produced small necrotic spots on the leaves and petioles, and all leaves having necrotic spots were abscised in a short time. We thus confirmed that this fungus has weak pathogenicity on S. obassia. This new species may promote early defoliation of S. obassia during the fall. 相似文献
158.
Gen Sakurai Seiichiro Yonemura Ayaka W. Kishimoto-Mo Shohei Murayama Toshiyuki Ohtsuka Masayuki Yokozawa 《PloS one》2015,10(3)
Carbon dioxide (CO2) efflux from the soil surface, which is a major source of CO2 from terrestrial ecosystems, represents the total CO2 production at all soil depths. Although many studies have estimated the vertical profile of the CO2 production rate, one of the difficulties in estimating the vertical profile is measuring diffusion coefficients of CO2 at all soil depths in a nondestructive manner. In this study, we estimated the temporal variation in the vertical profile of the CO2 production rate using a data assimilation method, the particle filtering method, in which the diffusion coefficients of CO2 were simultaneously estimated. The CO2 concentrations at several soil depths and CO2 efflux from the soil surface (only during the snow-free period) were measured at two points in a broadleaf forest in Japan, and the data were assimilated into a simple model including a diffusion equation. We found that there were large variations in the pattern of the vertical profile of the CO2 production rate between experiment sites: the peak CO2 production rate was at soil depths around 10 cm during the snow-free period at one site, but the peak was at the soil surface at the other site. Using this method to estimate the CO2 production rate during snow-cover periods allowed us to estimate CO2 efflux during that period as well. We estimated that the CO2 efflux during the snow-cover period (about half the year) accounted for around 13% of the annual CO2 efflux at this site. Although the method proposed in this study does not ensure the validity of the estimated diffusion coefficients and CO2 production rates, the method enables us to more closely approach the “actual” values by decreasing the variance of the posterior distribution of the values. 相似文献
159.
Changes in the amino acid composition and protein modification in phloem sap of rice 总被引:1,自引:0,他引:1
Pure phloem sap was collected from insects feeding on rice (Oryza sativa L.) leaves by a laser technique similar to the aphid stylet technique. Rapid circulation of nitrogen in the sieve tubes was demonstrated directly using 15N as a tracer. Application to the roots of the metabolic inhibitors of amino acids, aminooxyacetate and methioninesulfoximine, changed the amino acid composition in the sieve tubes. Feeding methionine to leaf tips resulted in its bulk transfer into the sieve tubes.
In vitro experiments confirmed the existence of protein kinases in the pure rice phloem sap. The phosphorylation status of the sieve tube sap proteins was affected by the light regime. The possibility that changes in chemical composition or protein modification such as phosphorylation in the sieve tubes might affect plant growth are discussed.Analysis of pure phloem sap collected from rice plants by insect laser technique has shown dynamic changes in the chemical composition and the quality of proteins in the sap. 相似文献
160.
The in vitro study was performed in order to demonstrate the structural changes of lipophorin induced in vivo by the injection of adipokinetic hormone (AKH) into adult locusts. After many unsuccessful attempts, we have established the reconstructed incubation system in which purified lipophorin and apolipophorin-III (9 mol/mol lipophorin) are incubated with the fat body in the presence of AKH under a supply of excess oxygen. In this system, high density lipophorin (HDLp) originally present in the incubation medium can be transformed entirely into low density lipophorin (LDLp) due to the loading of an increased amount of diacylglycerol from the fat body. The LDLp formed in this incubation system was exactly the same as the LDLp formed in vivo by the injection of AKH, in terms of density, particle size, diacylglycerol content, and the association with apolipophorin-III (apoLp-III). In the absence of apoLp-III, AKH did not exhibit its function to any extent. It was also demonstrated that the transformation of HDLp to LDLp requires calcium ions. Moreover, it appears that, up to a certain limit, the increase of diacylglycerol content of lipophorin and the amount of apoLp-III associated with lipophorin is nearly proportional to the amount of apoLp-III added to the incubation medium. 相似文献