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   1812篇
  免费   113篇
  国内免费   4篇
化学   1094篇
晶体学   11篇
力学   70篇
数学   242篇
物理学   396篇
无线电   116篇
  2024年   3篇
  2023年   13篇
  2022年   32篇
  2021年   46篇
  2020年   58篇
  2019年   37篇
  2018年   37篇
  2017年   42篇
  2016年   81篇
  2015年   87篇
  2014年   88篇
  2013年   108篇
  2012年   165篇
  2011年   197篇
  2010年   111篇
  2009年   68篇
  2008年   156篇
  2007年   126篇
  2006年   107篇
  2005年   81篇
  2004年   59篇
  2003年   42篇
  2002年   26篇
  2001年   10篇
  2000年   12篇
  1999年   11篇
  1998年   13篇
  1997年   7篇
  1996年   13篇
  1995年   5篇
  1994年   8篇
  1993年   7篇
  1992年   8篇
  1991年   6篇
  1990年   7篇
  1989年   5篇
  1988年   4篇
  1985年   5篇
  1984年   3篇
  1983年   2篇
  1982年   2篇
  1981年   2篇
  1980年   3篇
  1974年   2篇
  1964年   2篇
  1958年   2篇
  1954年   3篇
  1948年   2篇
  1947年   2篇
  1946年   2篇
排序方式: 共有1929条查询结果,搜索用时 15 毫秒
51.
52.
53.
We give a necessary and sufficient condition for the precompactness of all optimizing sequences for the Stein–Tomas inequality. In particular, if a well-known conjecture about the optimal constant in the Strichartz inequality is true, we obtain the existence of an optimizer in the Stein–Tomas inequality. Our result is valid in any dimension.  相似文献   
54.
Muscle models are useful in bio-inspired robotic, because they allow to reproduce accurately natural motion. When they are used for robotic issue, they need to be compact and embeddable. The non-integer model order has the advantage to ensure a parametrical parsimony that permits to implant it easily on an embedded system. Thus, a fractional multi-model of muscle was identified and presented in later paper. This model is able to predict the response of a motor unit to an electrical stimulation, considering isometric contractions (that is to say, muscle length is constant). There are three different physiological types of motor unit (FR, FF, and S). The aim of this work is to study muscle length impact on the multi-model and the limitations of the linear multi-model. Previous paper was published using FR type motor unit. In this paper, the results of the study using S type motor unit are presented.  相似文献   
55.
Triangle centers such as the center of gravity, the circumcenter, the orthocenter are well studied by geometers. Recently, under the guidance of Clark Kimberling, an electronic encyclopedia of triangle centers (ETC) has been developed, it contains more than 7000 centers and many properties of these points. In this paper, we describe how we created a certified version of ETC such that some of the properties described come along with a computer checked proof of its validity.  相似文献   
56.
This article deals with the Kumada Catalyst Transfer Polycondensation (KCTP) of 4,7‐dioctylbenzo[2,1‐b:3,4‐b']dithiophene ( BDP‐Oct ) using Ni(II) catalyst or In/cat combination. A combination of MALDI MS, GPC, and 31P NMR spectroscopy is used to reveal the failure of the KCTP of this particular monomer. Intermolecular transfer reactions to monomer appeared to prevent the formation of polymer. This result is remarkable, since isomeric benzo[1,2‐b:4,5‐b']dithiophene polymerizes in a controlled way. The presence of a “non‐aromatic double bond” in annulated monomers is discussed. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1706–1712  相似文献   
57.
58.
We study the properties of the ergosurface of the Pomeransky–Senkov black rings, and show that it splits into an “inner” and an “outer” region. As for the singular set, the topology of the “outer ergosurface” depends upon the value of parameters.  相似文献   
59.
Journal of Solid State Electrochemistry - Activated carbon from tree bark (ACB) has been synthesized by a facile and environmentally friendly activation and carbonization process at different...  相似文献   
60.
A novel methodology for the design of optimal uncoupled laminated plates under membrane only or bending only loading is introduced. This approach is supported by the polar representation of anisotropy. First, topology optimization, aimed at maximizing global stiffness of the structure, allows to find an optimal distribution of polar components. Then, based on the latter structural results, a matching feasible lamination sequence is determined.  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