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   623826篇
  免费   7955篇
  国内免费   2075篇
化学   339396篇
晶体学   9079篇
力学   27106篇
综合类   25篇
数学   75720篇
物理学   182530篇
  2020年   4557篇
  2019年   4665篇
  2018年   5538篇
  2017年   5380篇
  2016年   9261篇
  2015年   6577篇
  2014年   9462篇
  2013年   26698篇
  2012年   20099篇
  2011年   24658篇
  2010年   16328篇
  2009年   16019篇
  2008年   22804篇
  2007年   23160篇
  2006年   22234篇
  2005年   20310篇
  2004年   18373篇
  2003年   16428篇
  2002年   16093篇
  2001年   17461篇
  2000年   13627篇
  1999年   10776篇
  1998年   9224篇
  1997年   8965篇
  1996年   8906篇
  1995年   8178篇
  1994年   8058篇
  1993年   7626篇
  1992年   8612篇
  1991年   8334篇
  1990年   8012篇
  1989年   7763篇
  1988年   8003篇
  1987年   7756篇
  1986年   7385篇
  1985年   10276篇
  1984年   10604篇
  1983年   8789篇
  1982年   9484篇
  1981年   9313篇
  1980年   9115篇
  1979年   9156篇
  1978年   9543篇
  1977年   9429篇
  1976年   9461篇
  1975年   9005篇
  1974年   8787篇
  1973年   9222篇
  1972年   5963篇
  1971年   4744篇
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
61.
We summarize the results of our recent work on Bäcklund transformations (BTs), particularly focusing on the relation between BTs and infinitesimal symmetries. We present a BT for an associated Degasperis–Procesi (aDP) equation and its superposition principle and investigate the solutions generated by applying this BT. Following our general methodology, we use the superposition principle of the BT to generate the infinitesimal symmetries of the aDP equation.  相似文献   
62.
G. Peruginelli 《代数通讯》2018,46(11):4724-4738
We classify the maximal subrings of the ring of n×n matrices over a finite field, and show that these subrings may be divided into three types. We also describe all of the maximal subrings of a finite semisimple ring, and categorize them into two classes. As an application of these results, we calculate the covering number of a finite semisimple ring.  相似文献   
63.
64.
65.
66.
67.
68.
69.
Experimental Techniques - The analysis of residual stress in glass is usually carried out by means of photoelastic methods. This article considers the automation of the white light photoelastic...  相似文献   
70.
Profiling engineered data with robust mining methods continues attracting attention in knowledge engineering systems. The purpose of this article is to propose a simple technique that deals with non-linear multi-factorial multi-characteristic screening suitable for knowledge discovery studies. The method is designed to proactively seek and quantify significant information content in engineered mini-datasets. This is achieved by deploying replicated fractional-factorial sampling schemes. Compiled multi-response data are converted to a single master-response effectuated by a series of distribution-free transformations and multi-compressed data fusions. The resulting amalgamated master response is deciphered by non-linear multi-factorial stealth stochastics intended for saturated schemes. The stealth properties of our method target processing datasets which might be overwhelmed by a lack of knowledge about the nature of reference distributions at play. Stealth features are triggered to overcome restrictions regarding the data normality conformance, the effect sparsity assumption and the inherent collapse of the ‘unexplainable error’ connotation in saturated arrays. The technique is showcased by profiling four ordinary controlling factors that influence webpage content performance by collecting data from a commercial browser monitoring service on a large scale web host. The examined effects are: (1) the number of Cascading Style Sheets files, (2) the number of JavaScript files, (3) the number of Image files, and (4) the Domain Name System Aliasing. The webpage performance level was screened against three popular characteristics: (1) the time to first visual, (2) the total loading time, and (3) the customer satisfaction. Our robust multi-response data mining technique is elucidated for a ten-replicate run study dictated by an L9(34) orthogonal array scheme where any uncontrolled noise embedded contribution has not been necessarily excluded.  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