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   241篇
  免费   7篇
化学   149篇
晶体学   5篇
力学   17篇
数学   41篇
物理学   36篇
  2023年   2篇
  2022年   4篇
  2021年   2篇
  2020年   3篇
  2019年   5篇
  2018年   6篇
  2017年   7篇
  2016年   12篇
  2015年   10篇
  2014年   3篇
  2013年   14篇
  2012年   12篇
  2011年   11篇
  2010年   13篇
  2008年   11篇
  2007年   12篇
  2006年   9篇
  2005年   12篇
  2004年   15篇
  2003年   6篇
  2002年   3篇
  2001年   2篇
  2000年   5篇
  1999年   2篇
  1998年   3篇
  1997年   2篇
  1995年   4篇
  1994年   4篇
  1993年   5篇
  1992年   3篇
  1989年   3篇
  1986年   4篇
  1985年   1篇
  1984年   4篇
  1983年   3篇
  1982年   3篇
  1981年   5篇
  1980年   2篇
  1979年   2篇
  1975年   1篇
  1973年   1篇
  1972年   5篇
  1968年   1篇
  1967年   1篇
  1965年   1篇
  1960年   2篇
  1958年   2篇
  1957年   1篇
  1956年   1篇
  1943年   1篇
排序方式: 共有248条查询结果,搜索用时 15 毫秒
241.
Jānis Cīrulis 《Order》2014,31(3):403-419
A quasi-orthomodular poset is defined to be a poset with 0 equipped with an orthogonality relation satisfying certain axioms. The goal of the paper is to compare such posets (also semilattices, nearlattices and lattices) with several other kinds of posets having an appropriate structure and already known in the literature: generalized orthomodular posets and lattices, generalized orthoalgebras, sectionally orthocomplemented, sectionally orthomodular and relatively orthocomplemented posets and meet semilattices, semi-orthomodular lattices, weak BCK-algebras.  相似文献   
242.
A freeoid over a (normally, infinite) set of variables X is defined to be a pair (W, E), where W is a superset of X, and E is a submonoid of W W containing just one extension of every mapping XW. For instance, if W is a relatively free algebra over a set of free generators X, then the pair F(W) := (W, End(W)) is a freeoid. In the paper, the kernel equivalence and the range of the transformation F are characterized. Freeoids form a category; it is shown that the transformation F gives rise to a functor from the category of relatively free algebras to the category of freeoids which yields a concrete equivalence of the first category to a full subcategory of the second one. Also, the concept of a model of a freeoid is introduced; the variety generated by a free algebra W is shown to be concretely equivalent to the category of models of F(W). The sets X, W, and the algebras W may generally be many-sorted.  相似文献   
243.
244.
The use of injectable materials is a simple approach for drug delivery and tissue repair, in, e.g. minimally invasive surgery applications. If these materials are used past their glass transition temperature and have a low viscosity, they will be able to flow while delivered in situ. Whether these materials are to be used as low viscosity drug carriers or further crosslinked for tissue repair, there is a need for a better understanding of their handling properties. In this study, oligo(trimethylene carbonate) (oTMC) and oligo[D,L‐lactide‐co‐(ε‐caprolactone)] (oDLLA‐co‐CL) of various molecular weights within a relevant injectability range were synthesized via ring‐opening polymerization. The materials were comparatively characterized by 1H NMR spectroscopy, differential scanning calorimetry, gel permeation chromatography, and rheological measurements. After comparing the viscosities and molecular weights of the materials, it was concluded that oDLLA‐co‐CLs were, generally, better suited as an injectable in situ crosslinking network, whereas oTMCs were found to be better candidates as injectable drug carriers. This study provides useful data and guidelines on the use of these and other similar oligomers intended for injectable implants. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
245.
We present a new development of digital off-axis (OA) holography for determining the instantaneous solid particle positions in a flow. This holographic imaging method uses a CCD camera for the simultaneous digital recording of two views of digital Fresnel OA holograms on the same support. The reconstruction is obtained numerically. The method provides two orthogonal views of the same flow area of interest at the same instant. It helps to overcome the depth of focus problem existing for the particle image reconstructions and that is inherent to the method. This method has the advantage of being simpler than the methods presently available, and it does not suffer from the flaws of in-line holographic configuration. Furthermore it is completely digital and thus avoids the cumbersome analysis following hologram recording. Digital holograms and digital reconstructions are obtained for solid particles of 200 mum moving into a stirred flow cell of 5 cm(3).  相似文献   
246.
247.
Journal of Solid State Electrochemistry - Solid state ionics is one of the key research topics of the Institute of Solid State Physics, University of Latvia since its establishment. The research...  相似文献   
248.
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