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   716篇
  免费   31篇
  国内免费   1篇
化学   557篇
晶体学   5篇
力学   6篇
数学   50篇
物理学   130篇
  2023年   6篇
  2022年   3篇
  2021年   12篇
  2020年   18篇
  2019年   17篇
  2018年   15篇
  2017年   10篇
  2016年   18篇
  2015年   15篇
  2014年   27篇
  2013年   39篇
  2012年   39篇
  2011年   46篇
  2010年   24篇
  2009年   19篇
  2008年   47篇
  2007年   41篇
  2006年   42篇
  2005年   39篇
  2004年   35篇
  2003年   29篇
  2002年   29篇
  2001年   9篇
  2000年   10篇
  1999年   7篇
  1998年   6篇
  1997年   13篇
  1996年   14篇
  1995年   6篇
  1994年   4篇
  1993年   7篇
  1992年   7篇
  1991年   5篇
  1989年   2篇
  1988年   7篇
  1987年   3篇
  1986年   11篇
  1985年   7篇
  1984年   10篇
  1983年   5篇
  1982年   7篇
  1981年   8篇
  1980年   3篇
  1979年   6篇
  1978年   4篇
  1977年   4篇
  1968年   3篇
  1967年   3篇
  1966年   1篇
  1964年   1篇
排序方式: 共有748条查询结果,搜索用时 62 毫秒
31.
In the present communication we would like to describe a novel method for the preparation of p-chloromethylstyrene and some reactions of this compound.  相似文献   
32.
Abstract

A memory type PDLC has been prepared by sandwiching a mixture of two-frequency-addressing liquid crystals and acrylate monomers with a hydoroxy group between two glass substrates with ITO electrodes followed by UV irradiation. This PDLC can be electrically switched between a transparent state and a light scattering state, which are maintained over several months without electric fields.  相似文献   
33.
34.
35.
Applicatims a Mo- and W-based heteropoly acids (HPA) as a catalyst in the oxidation of olefins have extensively been investigated1. However, a patent work is only attempted concerning the evoxidatim of olefins with H202 by HPA2) since the oxirane ring is cleaved because of a strong acidity of HPA itself. Herein, an effective epoxidatim of some allylic alcohols with H202 by a new Mo-species (MPCP), which was prepared from 12-molybdatophosphoric acid (H3PMo12040) and cetylpyridinium chloride (C5H5N (CH2), 15CH3- C1-) under two-phase conditions using chloroform as an organic solvent, is described.  相似文献   
36.
37.
Arylpyrrolyldiketone boron complexes as anion‐responsive π‐electronic molecules were synthesized by Claisen condensations of acetylpyrrole and corresponding aryl esters. The synthesized π‐electronic molecules exhibited anion‐binding behavior with various binding modes including pyrrole‐inverted and non‐inverted [1+1]‐type anion complexes as well as [2+1]‐type complexes owing to the presence of only a single pyrrole ring. Furthermore, solid‐state ion‐pairing assemblies, comprising receptor–anion complexes and countercations, were constructed based on fairly planar [2+1]‐type complexes.  相似文献   
38.
The statistical behaviour of the variances, covariance and gradients of the reaction progress variable (c), and the mixture fraction (ξ) have been analysed in a pulverised coal jet flame using a three-dimensional carrier phase direct numerical simulation (DNS) dataset. It has been observed that the Favre-probability density functions (PDFs) of c and ξ can be parametrised by the standard β function. Furthermore, the log-normal distribution has been found to accurately represent |?c| and |?ξ|. It is also found that ?c and ?ξ remain aligned throughout the flame brush. Finally the joint PDF of |?c| and |?ξ| has been compared with the product of the PDF of |?c| and PDF of |?ξ| extracted from carrier phase DNS, and it has been found that |?c| and |?ξ| are not statistically independent in the case investigated.The bivariate log-normal distributions with and without correlation have also been considered, and the former is found to be in better agreement with the carrier phase DNS data.  相似文献   
39.
40.
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