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   149篇
  免费   13篇
  2023年   2篇
  2021年   5篇
  2020年   2篇
  2019年   1篇
  2018年   4篇
  2017年   4篇
  2016年   8篇
  2015年   8篇
  2014年   5篇
  2013年   7篇
  2012年   15篇
  2011年   15篇
  2010年   9篇
  2009年   9篇
  2008年   9篇
  2007年   10篇
  2006年   10篇
  2005年   11篇
  2004年   1篇
  2003年   5篇
  2002年   1篇
  2001年   1篇
  1997年   1篇
  1996年   1篇
  1995年   1篇
  1994年   2篇
  1989年   1篇
  1981年   1篇
  1976年   1篇
  1974年   2篇
  1973年   2篇
  1972年   2篇
  1971年   5篇
  1951年   1篇
排序方式: 共有162条查询结果,搜索用时 46 毫秒
141.
142.
Tissue samples obtained from the lateral wall of the maxillary sinuses of five patients were examined by light microscopical, histochemical, and ultrastructural techniques. Submucosal glands were tubulo-alveolar mixed glands. The acini consisted of either all serous or all mucous cells, or a mixture of both. Serous granules were stained by toluidine blue, or by hematoxylin and eosin (H and E), but showed little or no reaction with periodic acid-Schiff (PAS) or Alcian blue. Mucous granules were pale in toluidine blue or H and E preparations, and consisted primarily of acid mucosubstances, as demonstrated by their staining reaction with PAS and Alcian blue. At the electron microscope level, the serous granules were either homogeneously dense, or showed a substructure consisting of at least two layers of distinctly different electron-opacity. Typical mucous droplets consisted of a fibrillar network dispersed in a translucent matrix. A second secretory product was present in the mucous cells in the form of elongated, membrane-bounded structures containing numerous parallel filaments, which measured about 55 Å in diameter. The mucous droplets and the filamentous bodies appear to arise from the opposite faces of the Golgi complex in the mucous cells. The filamentous bodies showed a pronounced tendency to fuse with the mucous droplets. All acini were surrounded by a well-defined myoepithelial layer and contained intercellular nerve terminals.  相似文献   
143.
144.

Background  

The potential of transgenic plants for cost-effective production of pharmaceutical molecules is now becoming apparent. Plants have the advantage over established fermentation systems (bacterial, yeast or animal cell cultures) to circumvent the risk of pathogen contamination, to be amenable to large scaling up and to necessitate only established farming procedures. Chloroplasts have proven a useful cellular compartment for protein accumulation owing to their large size and number, as well as the possibility for organellar transformation. They therefore represent the targeting destination of choice for recombinant proteins in leaf crops such as tobacco. Extraction and purification of recombinant proteins from leaf material contribute to a large extent to the production costs. Developing new strategies facilitating these processes is therefore necessary.  相似文献   
145.
146.
147.
148.
The simulation modelling of shore- and sea-side port operations constitutes a fundamental prerequisite for effective project planning in port development, as the influence of numerous often interactive parameters has to be addressed at an early stage to account for the optimum supply of port facilities and services to current and future demand. This paper presents a detailed review of the available research literature on the application of simulation models in port development, through extensive reference to published journal papers from the onset of the relevant simulation modelling and through the course of the past 54 years (1961–2015). With focus on container terminals, this review aims at analysing the use of port related simulation models and ultimately at assessing their contribution into building the research knowledge necessary to promote sustainable ship-port interfaces and freight transport chains. It was found that over the past 50 years the use of simulation models has been increasingly favoured and instrumental in the development of ports and more specifically of container terminals. Most of the research literature addresses operational issues, accounting for its highest concentration and coherence in the research field of operations research, although the need to utilise the wide-ranging capabilities of simulation modelling in order to offer integrated solutions is recently promoting the dissemination of the relevant literature through sector-specific (i.e. transport and maritime) research fields. Finally, the observed tendency to employ simulation tools which offer the most realistic results reflects the research effort to ensure that simulation modelling offers tangible solutions to the maritime and transport industry.  相似文献   
149.
150.

Dispersal is a key process for the maintenance of intraspecific genetic diversity by ensuring gene flow within and between populations. Despite the ongoing expansion of large carnivores in Europe, lynx populations remain fragmented, isolated, and threatened by inbreeding and loss of genetic diversity. In the course of large carnivore monitoring in the Czech Republic, several biological samples of Eurasian lynx were collected outside the permanent occurrence of this species. Using microsatellite genotyping we identified these as four dispersing lynx males and applied multiple methods (Bayesian clustering in STRUCTURE, Principal Component Analysis (PCA), frequency-based method in GENECLASS2, and machine-learning framework in assignPOP) to assign them to possible source populations. For this we used genotypes from five European lynx populations: the Bohemian-Bavarian-Austrian (N?=?36), Carpathian (N?=?43), Scandinavian (N?=?20), Baltic (N?=?15), and Harz (N?=?23) population. All four dispersers were successfully assigned to different source populations within Europe and each was recorded at a distance of more than 98 km from the edge of the distribution of the source population identified. Such movements are among the longest described for lynx in Central Europe to this point. The findings indicate the ability of lynx males to disperse in human-dominated landscape thus facilitation of these movements via creation and/or protection of potential migratory corridors together with protection of dispersing individuals should be of high importance in conservation of this iconic predator in Central Europe.

  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