首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   238篇
  免费   13篇
  2023年   1篇
  2022年   3篇
  2021年   22篇
  2020年   10篇
  2019年   4篇
  2018年   5篇
  2017年   4篇
  2016年   6篇
  2015年   16篇
  2014年   18篇
  2013年   13篇
  2012年   16篇
  2011年   17篇
  2010年   10篇
  2009年   8篇
  2008年   6篇
  2007年   6篇
  2006年   11篇
  2005年   8篇
  2004年   8篇
  2003年   1篇
  2002年   4篇
  2001年   5篇
  2000年   2篇
  1999年   3篇
  1996年   1篇
  1995年   2篇
  1994年   1篇
  1992年   2篇
  1991年   1篇
  1989年   2篇
  1988年   3篇
  1987年   2篇
  1986年   6篇
  1985年   3篇
  1984年   4篇
  1983年   10篇
  1982年   3篇
  1980年   1篇
  1976年   1篇
  1974年   1篇
  1972年   1篇
排序方式: 共有251条查询结果,搜索用时 15 毫秒
81.
Here we report for the first time the isolation of butyl 2,3‐dihydroxybenzoate (B2,3DB) from the novel antagonistic bacterium Paenibacillus elgii HOA73 and its activity against Fusarium oxysporum f.sp. lycopersici (FOL). In this study, the bacterial strain P. elgii HOA73 was isolated from soil and identified via 16S rRNA gene sequence analysis. The isolate demonstrated significant antagonism towards several plant pathogens including FOL. Our results showed the bacterial culture filtrate of P. elgii HOA73 to be highly active, inhibiting 86.1% of the growth of FOL at 50% concentration. Similarly, the bacterial crude extract of P. elgii HOA73 at 2 mg significantly inhibited FOL growth by 72.5%. An antifungal compound was purified from the bacterial crude extract of P. elgii HOA73 through different chromatographic techniques and was identif‐ied as butyl 2,3‐dihydroxybenzoate (B2,3DB) based on nuclear magnetic resonance and liquid chromatography‐mass spectrometry analyses. B2,3DB displayed potent antifungal properties, inhibiting FOL growth by 83.2% when used at 0.6 mg. The minimum inhibitory concentration of B2,3DB to inhibit any visible mycelial growth of FOL was 32 μg ml?1. All FOL conidia displayed an absence of germination or degradation when treated with 32 μg ml?1 B2,3DB after 8 or 24 h, respectively. Therefore, our results clearly demonstrated B2,3DB, as well as P. elgii HOA73, as potential biological control agents for the management of FOL.  相似文献   
82.
83.
84.
85.
Bumblebee, Bombus terrestris queens undergo winter diapause and show a great difference in diapause duration in natural conditions. Queens emerged from diapause initiate colonies by producing a batch of diploid (fertilised) eggs that develop into workers. In this study we investigated the effects of both the duration of queen diapause (2, 3, 4, or 5 months) and colony size (artificially limited to 50, 100, 150, and 200 workers) on the number of sexuals (males or new queens — gynes) produced, when gynes are produced and the longevity of both the foundress queen and the colony. Both worker population and diapause duration showed significant effect on sexual gyne production, foundress queen longevity and colony longevity but their interaction effect was insignificant. The worker number and diapause duration, respectively showed significant effect on sexual male production and gyne emergence period, but their interaction effects were insignificant.  相似文献   
86.
Aung K  Hu J 《The Plant cell》2011,23(12):4446-4461
Peroxisomes and mitochondria are multifunctional eukaryotic organelles that are not only interconnected metabolically but also share proteins in division. Two evolutionarily conserved division factors, dynamin-related protein (DRP) and its organelle anchor FISSION1 (FIS1), mediate the fission of both peroxisomes and mitochondria. Here, we identified and characterized a plant-specific protein shared by these two types of organelles. The Arabidopsis thaliana PEROXISOMAL and MITOCHONDRIAL DIVISION FACTOR1 (PMD1) is a coiled-coil protein tethered to the membranes of peroxisomes and mitochondria by its C terminus. Null mutants of PMD1 contain enlarged peroxisomes and elongated mitochondria, and plants overexpressing PMD1 have an increased number of these organelles that are smaller in size and often aggregated. PMD1 lacks physical interaction with the known division proteins DRP3 and FIS1; it is also not required for DRP3's organelle targeting. Affinity purifications pulled down PMD1's homolog, PMD2, which exclusively targets to mitochondria and plays a specific role in mitochondrial morphogenesis. PMD1 and PMD2 can form homo- and heterocomplexes. Organelle targeting signals reside in the C termini of these proteins. Our results suggest that PMD1 facilitates peroxisomal and mitochondrial proliferation in a FIS1/DRP3-independent manner and that the homologous proteins PMD1 and PMD2 perform nonredundant functions in organelle morphogenesis.  相似文献   
87.
For over a century, a Neogene fossil mammal fauna has been known in the Irrawaddy Formation in central Myanmar. Unfortunately, the lack of accurately located fossiliferous sites and the absence of hominoid fossils have impeded paleontological studies. Here we describe the first hominoid found in Myanmar together with a Hipparion (s.l.) associated mammal fauna from Irrawaddy Formation deposits dated between 10.4 and 8.8 Ma by biochronology and magnetostratigraphy. This hominoid documents a new species of Khoratpithecus, increasing thereby the Miocene diversity of southern Asian hominoids. The composition of the associated fauna as well as stable isotope data on Hipparion (s.l.) indicate that it inhabited an evergreen forest in a C3-plant environment. Our results enlighten that late Miocene hominoids were more regionally diversified than other large mammals, pointing towards regionally-bounded evolution of the representatives of this group in Southeast Asia. The Irrawaddy Formation, with its extensive outcrops and long temporal range, has a great potential for improving our knowledge of hominoid evolution in Asia.  相似文献   
88.
In a continuing search for bioactive constituents from Dioscoreaceae medicinal plants, two new cyclic diarylheptanoids, diosniponol A (1) and B (2), together with 10 known compounds (312) were isolated from the rhizomes of Dioscorea nipponica. The structures of these new compounds were determined by spectroscopic analyses, including extensive two-dimensional nuclear magnetic resonance, high-resolution mass spectrometry, and optical rotation. All isolated compounds 112 were evaluated for their effects on nitric oxide (NO) production in murine microglia cell line BV-2. Compounds 8 and 11 showed potent inhibitory activities on NO production (IC50 13.36 and 14.36 μM, respectively) without cell toxicity in lipopolysaccharide-activated BV-2 cells.  相似文献   
89.
90.
The rhizome of Dioscorea japonica is a food and medicinal source known as ‘San Yak’ in Korea. Two new furostanol saponins, coreajaponins A (1) and B (2), together with 10 known compounds (3-12) were isolated from the rhizomes of D. japonica. Their structures were determined by spectroscopic methods, including 1D and 2D NMR techniques, HRMS, and chemical methods. Nerve growth factor (NGF), a crucial factor for neuronal survival and differentiation, can potentially improve neurodegenerative diseases and diabetic polyneuropathy. We evaluated the effects of isolates (1-12) on NGF induction in a C6 rat glioma cell line. Coreajaponin B (2) upregulated NGF content without significant cell toxicity, as did 6, 8, 9, and 11.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号