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   537892篇
  免费   6315篇
  国内免费   1677篇
化学   290662篇
晶体学   7886篇
力学   23541篇
综合类   16篇
数学   64265篇
物理学   159514篇
  2020年   3941篇
  2019年   4095篇
  2018年   4907篇
  2017年   4783篇
  2016年   7940篇
  2015年   5616篇
  2014年   8281篇
  2013年   23073篇
  2012年   17472篇
  2011年   21571篇
  2010年   14311篇
  2009年   14171篇
  2008年   20010篇
  2007年   20400篇
  2006年   19519篇
  2005年   17727篇
  2004年   16058篇
  2003年   14354篇
  2002年   14123篇
  2001年   15610篇
  2000年   12111篇
  1999年   9508篇
  1998年   8042篇
  1997年   7810篇
  1996年   7738篇
  1995年   7080篇
  1994年   7022篇
  1993年   6631篇
  1992年   7420篇
  1991年   7287篇
  1990年   6992篇
  1989年   6686篇
  1988年   7032篇
  1987年   6681篇
  1986年   6379篇
  1985年   8887篇
  1984年   9153篇
  1983年   7560篇
  1982年   8052篇
  1981年   7992篇
  1980年   7745篇
  1979年   7836篇
  1978年   8149篇
  1977年   8050篇
  1976年   8092篇
  1975年   7695篇
  1974年   7601篇
  1973年   7907篇
  1972年   5085篇
  1971年   4002篇
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
51.
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   
52.
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   
53.
54.
55.
56.
57.
58.
59.
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   
60.
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