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   81152篇
  免费   999篇
  国内免费   891篇
化学   26331篇
晶体学   848篇
力学   6955篇
综合类   23篇
数学   32449篇
物理学   16436篇
  2023年   88篇
  2022年   80篇
  2021年   133篇
  2020年   182篇
  2019年   143篇
  2018年   10560篇
  2017年   10388篇
  2016年   6212篇
  2015年   1011篇
  2014年   500篇
  2013年   579篇
  2012年   4079篇
  2011年   10800篇
  2010年   5830篇
  2009年   6270篇
  2008年   6813篇
  2007年   8923篇
  2006年   452篇
  2005年   1460篇
  2004年   1627篇
  2003年   2054篇
  2002年   1098篇
  2001年   325篇
  2000年   355篇
  1999年   225篇
  1998年   255篇
  1997年   193篇
  1996年   253篇
  1995年   151篇
  1994年   113篇
  1993年   122篇
  1992年   78篇
  1991年   92篇
  1990年   72篇
  1989年   70篇
  1988年   67篇
  1987年   70篇
  1986年   64篇
  1985年   51篇
  1984年   44篇
  1983年   42篇
  1982年   45篇
  1981年   43篇
  1980年   49篇
  1979年   44篇
  1914年   45篇
  1913年   40篇
  1912年   41篇
  1909年   41篇
  1908年   40篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
In the paper, the authors establish several integral representations for the generating functions of the large and little Schröder numbers and for the large and little Schröder numbers.  相似文献   
2.
Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant.  相似文献   
3.
4.
We prove that the group of diffeomorphisms of the interval [0, 1] contains surface groups whose action on (0, 1) has no global fix point and such that only countably many points of the interval (0, 1) have non-trivial stabiliser.  相似文献   
5.
6.
The research progress of a novel traffic solution,a submerged floating tunnel(SFT),is reviewed in terms of a study approach and loading scenario.Among existing publications,the buoyancy-weight ratio(BWR) is usually predefined.However,BWR is a critical structural parameter that tremendously affects the dynamic behaviour of not only the tunnel tube itself but also the cable system.In the context of a SFT prototype(SFTP) project in Qiandao Lake(Zhejiang Province,China),the importance of BWR is illustrated by finite element analysis and subsequently,an optimized BWR is proposed within a reasonable range in the present study.In the numerical model,structural damping is identified to be of importance.Rayleigh damping and the corresponding Rayleigh coefficients are attained through a sensitivity study,which shows that the adopted damping ratios are fairly suitable for SFTP.Lastly,the human sense of security is considered by quantifying the comfort index,which helps further optimize BWR in the SFTP structural parameter design.  相似文献   
7.
8.
9.
10.
The structure and properties of 12Cr1MoV steel irradiated with a zirconium ion beam were studied by optical microscopy, scanning electron microscopy, and micro- and nanoindentation. It is shown that the modification covers the entire cross-section of the irradiated specimens to a depth of 1 mm. The data on irradiation-induced structural changes are used to interpret the changes in mechanical properties of the irradiated specimens under static and cyclic loading. Particular attention is given to analysis of strain estimation by the digital image correlation method.  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