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   479篇
  免费   24篇
  国内免费   2篇
  2023年   3篇
  2022年   9篇
  2021年   13篇
  2020年   5篇
  2019年   7篇
  2018年   19篇
  2017年   11篇
  2016年   16篇
  2015年   24篇
  2014年   35篇
  2013年   67篇
  2012年   46篇
  2011年   45篇
  2010年   23篇
  2009年   23篇
  2008年   24篇
  2007年   22篇
  2006年   27篇
  2005年   20篇
  2004年   16篇
  2003年   13篇
  2002年   16篇
  2001年   2篇
  1999年   4篇
  1998年   6篇
  1996年   1篇
  1994年   1篇
  1993年   1篇
  1989年   1篇
  1988年   1篇
  1984年   3篇
  1978年   1篇
排序方式: 共有505条查询结果,搜索用时 875 毫秒
11.
A further investigation of the isoflavonoid constituents occurring in roots of the white lupin (Lupinus albus L. cv. Kievskij Mutant) has yielded five new coumaronochromones named lupinalbin A (la), B (2a), C (3), D (4) and E (5). These isoflavonoids were identified by physicochemical methods involving the use of biogenetically related 2′-hydroxyisoflavones as reference compounds. The presence of the rare dihydrofurano-isoflavone, erythrinin C (16), in white lupin roots has also been established.  相似文献   
12.
Cysteine-aldehyde compounds were prepared by the reactions of l-cysteine with formaldehyde, acetaldehyde, n-butyraldehyde, benzaldehyde and furfural in 50% ethanol solutions. Hydrogen sulfide and ammonia liberated from cysteine-aldehyde compounds in heated aqueous solutions (oil bath : 120°C) were determined. Although thiazolidine derivatives were stable generally in boiling aqueous solution, l-cysteine-furfural compound was unstable and a large amount of hydrogen sulfide compared with other compounds was released.  相似文献   
13.
14.
Carboxylic acids found in the cultured broth of Sporobolomyces odorus AHU 3246 which produces γ-lactones as principles of the aromatic flavor, were analyzed. The concentrate of methylated acids was steam-distilled and in the residue, succinic acid, nonanedioic acid (azelaic acid), undecanedioic acid and 2-hydroxy-3-phenylpropionic acid (β-phenyllactic acid) were identified as their methyl esters by GLC and spectroscopic methods. Phthalic acid and its mono-n-butyl ester were also found, but these compounds were thought to arise from di-n-butyl phthalate, one of impurities of deionized water.  相似文献   
15.
Three novel sesquiterpene alcohols, shizuka-acoradienol (2), shizukafuranol (3) and shizukol-idol (4), were isolated from Chloranthus japonicus Sieb. (Japanese name: Hitori-shizuka, Chloranthaceae). Their structures were elucidated on the basis of their physicochemical properties and some chemical reactions. Furanodienone (5), scopoletin (6a) and isoscopoletin (6b) were also isolated from this plant.  相似文献   
16.
17.
The effect of γ-irradiation on the flavor of Onions (Senshu Yellow) associated with sprout-inhibition has been investigated. The relative amounts of propionaldehyde, n-propyl mercaptan and di-n-propyl disulfide in onions stored for 0, 5, 10, 20 and 30 days, respectively, after irradiation were estimated by measurement of peak areas of gas chromatograms. It was observed that the lachrymatory character and the pungent flavor had been decreased by γ-irradiation (remarkably at 70 and 700 Krads). In this connection, the amounts of propionaldehyde and di-n-propyl disulfide were decreased with increasing radiation dose and storage period at room temperature (20 to 25°C) and at low temperature (4°C). Moreover, it was observed that the sweetness had been decreased by γ-irradiation, but the amount of n-propyl mercaptan was increased with radiation dose and storage period. Therefore it seems that there is no correlation between the sweetness of onion and the amount of n-propyl mercaptan.  相似文献   
18.
19.
Macroautophagy (autophagy) is a multistep intracellular degradation system. Autophagosomes form, mature, and ultimately fuse with lysosomes, where their sequestered cargo molecules are digested. In contrast to autophagosome formation, our knowledge of autophagosome-lysosome fusion is limited. In a recent study, we identified a novel regulator of autophagy, INPP5E (inositol polyphosphate-5-phosphatase E), which is essential for autophagosome-lysosome fusion. INPP5E primarily functions in neuronal cells, and knockdown of the corresponding gene causes accumulation of autophagosomes by impairing fusion with lysosomes. Some INPP5E molecules localize at the lysosome, and both lysosomal localization and INPP5E enzymatic activity are crucial for autophagy. In addition, INPP5E decreases PtdIns(3,5)P2 levels on lysosomes, leading to activation of CTTN (cortactin) and stabilization of actin filaments, which are also essential for autophagosome-lysosome fusion. Mutations in INPP5E are causative for Joubert syndrome, a rare brain abnormality, and our results indicate that defects in autophagy play a critical role in pathogenesis.  相似文献   
20.
Bruguiera hainesii (Rhizophoraceae) is one of the two Critically Endangered mangrove species listed in the IUCN Red List of Threatened Species. Although the species is vulnerable to extinction, its genetic diversity and the evolutionary relationships with other Bruguiera species are not well understood. Also, intermediate morphological characters imply that the species might be of hybrid origin. To clarify the genetic relationship between B. hainesii and other Bruguiera species, we conducted molecular analyses including all six Bruguiera species using DNA sequences of two nuclear genes (CesA and UNK) and three chloroplast regions (intergenic spacer regions of trnL-trnF, trnS-trnG and atpB-rbcL). For nuclear DNA markers, all nine B. hainesii samples from five populations were heterozygous at both loci, with one allele was shared with B. cylindrica, and the other with B. gymnorhiza. For chloroplast DNA markers, the two haplotypes found in B. hainesii were shared only by B. cylindrica. These results suggested that B. hainesii is a hybrid between B. cylindrica as the maternal parent and B. gymnorhiza as the paternal one. Furthermore, chloroplast DNA haplotypes found in B. hainesii suggest that hybridization has occurred independently in regions where the distribution ranges of the parental species meet. As the IUCN Red List of Threatened Species currently excludes hybrids (except for apomictic plant hybrids), the conservation status of B. hainesii should be reconsidered.  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