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   641篇
  免费   11篇
  国内免费   1篇
化学   349篇
晶体学   2篇
力学   54篇
数学   75篇
物理学   173篇
  2022年   8篇
  2021年   7篇
  2020年   8篇
  2019年   11篇
  2018年   10篇
  2017年   14篇
  2016年   18篇
  2015年   11篇
  2014年   15篇
  2013年   46篇
  2012年   24篇
  2011年   40篇
  2010年   25篇
  2009年   13篇
  2008年   33篇
  2007年   29篇
  2006年   29篇
  2005年   18篇
  2004年   23篇
  2003年   13篇
  2002年   10篇
  2001年   14篇
  2000年   7篇
  1999年   7篇
  1998年   5篇
  1997年   8篇
  1995年   6篇
  1994年   7篇
  1993年   9篇
  1992年   6篇
  1991年   8篇
  1990年   5篇
  1989年   6篇
  1987年   9篇
  1986年   7篇
  1985年   9篇
  1984年   9篇
  1983年   5篇
  1982年   9篇
  1981年   11篇
  1980年   12篇
  1979年   8篇
  1978年   13篇
  1977年   6篇
  1976年   4篇
  1973年   8篇
  1971年   4篇
  1968年   5篇
  1965年   4篇
  1962年   5篇
排序方式: 共有653条查询结果,搜索用时 15 毫秒
31.
32.
33.
The reaction of substituted arylboronic acids with 5-bromo-2-methoxytropone catalyzed by palladium(0) complex furnished 5-arylated tropone derivatives in good yield.  相似文献   
34.
JPC – Journal of Planar Chromatography – Modern TLC - The present research work was aimed to determine the stability of cefprozil monohydrate (CEFZ) as per various stress degradation...  相似文献   
35.
In this paper, we propose a new methodology for numerically solving elliptic and parabolic equations with discontinuous coefficients and singular source terms. This new scheme is obtained by clubbing a recently developed higher‐order compact methodology with special interface treatment for the points just next to the points of discontinuity. The overall order of accuracy of the scheme is at least second. We first formulate the scheme for one‐dimensional (1D) problems, and then extend it directly to two‐dimensional (2D) problems in polar coordinates. In the process, we also perform convergence and related analysis for both the cases. Finally, we show a new direction of implementing the methodology to 2D problems in cartesian coordinates. We then conduct numerous numerical studies on a number of problems, both for 1D and 2D cases, including the flow past circular cylinder governed by the incompressible Navier–Stokes equations. We compare our results with existing numerical and experimental results. In all the cases, our formulation is found to produce better results on coarser grids. For the circular cylinder problem, the scheme used is seen to capture all the flow characteristics including the famous von Kármán vortex street. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
36.
37.
38.
39.
Three related compounds of aripiprazole were identified during the synthesis. These related compounds were synthesized and characterized by their respective spectral data.  相似文献   
40.
In this article, thermal degradation behavior of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB)-based plastic-bonded explosives (PBXs) bonded with a different fluoropolymer matrices namely indigenous poly(vinylidene fluoride-chlorotrifluoroethylene) (FKM), FK 800, fluoroplastic F-32L and fluororubber SKF 32 was investigated through non-isothermal thermogravimetric analysis (TG) technique under nitrogen atmosphere. It was observed that the mass loss of PBXs containing FKM and FK 800 matrices occurred in three steps. The mass loss of PBXs containing fluoroplastic F-32L and fluororubber SKF 32 occurred in two steps. Kinetics were investigated through non-isothermal TG at different heating rates for the first step of degradation by means of model-free Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) methods. The activation energies calculated by applying FWO method are in good agreement and very close to those obtained by KAS method. The results revealed that the effect of the polymer matrices on the thermal degradation reaction of TATB was significantly observed especially different outcomes of kinetic parameters. The reaction models for degradation were also studied by Criado method. The reaction models are probably best described by the power law and diffusion models.  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