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   121篇
  免费   17篇
  2018年   2篇
  2016年   2篇
  2015年   4篇
  2014年   2篇
  2013年   6篇
  2012年   7篇
  2010年   3篇
  2009年   8篇
  2008年   7篇
  2006年   4篇
  2005年   6篇
  2004年   2篇
  2003年   6篇
  2002年   2篇
  2000年   5篇
  1999年   2篇
  1998年   3篇
  1996年   2篇
  1994年   2篇
  1993年   1篇
  1992年   3篇
  1991年   2篇
  1990年   1篇
  1989年   2篇
  1988年   1篇
  1987年   1篇
  1986年   3篇
  1985年   5篇
  1983年   2篇
  1982年   1篇
  1978年   1篇
  1975年   1篇
  1974年   1篇
  1972年   1篇
  1971年   4篇
  1969年   3篇
  1968年   3篇
  1925年   2篇
  1924年   1篇
  1920年   2篇
  1918年   1篇
  1916年   1篇
  1915年   1篇
  1914年   2篇
  1913年   2篇
  1912年   3篇
  1910年   1篇
  1908年   3篇
  1906年   1篇
  1905年   2篇
排序方式: 共有138条查询结果,搜索用时 46 毫秒
81.
82.
83.
Microflora of raw cacao beans   总被引:1,自引:0,他引:1  
Whole non-moldy cacao beans from 14 sources cultured on Czapek's agar with six percent NaCl yielded species ofAspergillus glaucus group,Mucor pusillus and unidentified yeast and bacteria. The average number of bacterial colonies from the 14 sources of non-moldy cacao beans was 32.7 million per gram. The average number of colonies of filamentous fungi in dilution cultures was 57,000 colonies per gram. Yeast colonies were present in the amount of 15.8 million colonies per gram. The moldy beans analyzed contained fungi and bacterial counts in the billions; also, yeast was not isolated from the moldy samples.Paper Number 3170 of the Journal Series of the North Carolina State University Agricultural Experiment Station, Raleigh, North Carolina 27607.  相似文献   
84.
A study of the origin and development of the bony complex ("dentaire" s.l.) later forming the anterior part of the mandible of Salmo fario leads to the following conclusions: (1) various modes of ossifications occur in the ontogeny of this bony complex, (2) the main component is the dermal (dento-splénial) whereas the enchondral one (mentomeckelien) is much reduced, (3) the proposed term "dento-splénio-mentomeckelien" focuses attention, at the same time, on the order of appearance and relative importance of the two components.  相似文献   
85.
86.
The regulation of carbon allocation between photosynthetic source leaves and sink tissues in response to stress is an important factor controlling plant yield. Ascorbate oxidase is an apoplastic enzyme, which controls the redox state of the apoplastic ascorbate pool. RNA interference was used to decrease ascorbate oxidase activity in tomato (Solanum lycopersicum L.). Fruit yield was increased in these lines under three conditions where assimilate became limiting for wild‐type plants: when fruit trusses were left unpruned, when leaves were removed or when water supply was limited. Several alterations in the transgenic lines could contribute to the improved yield and favour transport of assimilate from leaves to fruits in the ascorbate oxidase lines. Ascorbate oxidase plants showed increases in stomatal conductance and leaf and fruit sugar content, as well as an altered apoplastic hexose : sucrose ratio. Modifications in gene expression, enzyme activity and the fruit metabolome were coherent with the notion of the ascorbate oxidase RNAi lines showing altered sink strength. Ascorbate oxidase may therefore be a target for strategies aimed at improving water productivity in crop species.  相似文献   
87.
Large wood in streams can play an extraordinarily important role in influencing the physical structure of streams and in providing habitat for aquatic organisms. Since wood is continually lost from streams, predicting the future input of wood to streams from riparian forests is crucial to assessing or managing stream ecosystems. Unfortunately, regional monitoring protocols have no established capacity to provide this information. The goal of this research is to propose one or more methods that could meet this need. This goal is pursued by using stream wood delivery models to aid in the design of a monitoring method. Two questions are asked. First, does simpler data change model predictions of future contributions of wood from riparian ecosystems to the stream? The answers to this first question enable monitoring design to be tailored to details affecting estimates of future stream condition. These answers are important, because more detailed data is typically more costly. Second, which metrics, if any, correlate well with model predictions? If such metrics can be identified, then these measures can serve as effective indicators of ecosystem function directly, without using ecosystem models.These questions were addressed by collecting highly detailed field observations of riparian forests from 109 forested riparian sites in the Coast Range, Willamette Valley, and western Cascades of northwestern Oregon. Detailed and simplified versions of these data were used in models that forecast the potential of riparian forests to provide wood to the stream. Model predictions with less detailed data typically provided answers different than did predictions made with more detailed data. Thus, ecosystem assessments requiring these types of model predictions would benefit from more detailed data. In contrast, riparian metrics easily observed in the field (e.g. number of basal area of trees) or derived from remotely sensed imagery (e.g. number or height of canopy trees) were well correlated with model predictions of potential stream wood recruitment. When direct model predictions or model scenario analyses are not required, these metrics can serve as effective indicators of the potential of riparian forests to provide wood to the future stream network.  相似文献   
88.
The identity of a group of 13.5–20 kDa polypeptides whoseabundance decreases during the greening of intermittent-lightgrown barley seedlings was investigated. During greening therelative abundance of the 13.5–20 kDa polypeptides wasinversely related to that of LHC II, which had led others tosuggest a role of these polypeptides in the assembly of theLHC II and/or chloroplast development. The smallest 13.5 kDapolypeptide was identified as histone H4 by N-terminal sequencingof an internal peptide fragment produced by CNBr cleavage. Theentire group of 13.5–20 kDa polypeptides was thereafterverified to be nuclear histones by their similar mobility onSDS-PAGE to that of barley histones and immunoreactivity toyeast histone anti bodies. Their presence results from contaminationof plastid preparations by nucleosomes. Our results unequivocallysubstantiate earlier suggestions of others that polypeptidesoften found to contaminate immature plastids were of nuclearorigin. Methods to reduce or remove the histone contaminationwithout reduction in yield of thylakoids were developed so thattrue changes in the polypeptide content of thylakoids can bestudied during plastid development. (Received December 19, 1991; Accepted August 15, 1992)  相似文献   
89.
90.
Many research-funding agencies now require open access to the results of research they have funded, and some also require that researchers make available the raw data generated from that research. Similarly, the journal Trials aims to address inadequate reporting in randomised controlled trials, and in order to fulfil this objective, the journal is working with the scientific and publishing communities to try to establish best practice for publishing raw data from clinical trials in peer-reviewed biomedical journals. Common issues encountered when considering raw data for publication include patient privacy – unless explicit consent for publication is obtained – and ownership, but agreed-upon policies for tackling these concerns do not appear to be addressed in the guidance or mandates currently established. Potential next steps for journal editors and publishers, ethics committees, research-funding agencies, and researchers are proposed, and alternatives to journal publication, such as restricted access repositories, are outlined.  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