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   1428201篇
  免费   29813篇
  国内免费   7742篇
化学   721359篇
晶体学   16030篇
力学   77223篇
综合类   115篇
数学   250613篇
物理学   400416篇
  2021年   13502篇
  2020年   15982篇
  2019年   16100篇
  2018年   17033篇
  2017年   15826篇
  2016年   29899篇
  2015年   21267篇
  2014年   30561篇
  2013年   74602篇
  2012年   43619篇
  2011年   45712篇
  2010年   41388篇
  2009年   42930篇
  2008年   43245篇
  2007年   40664篇
  2006年   41214篇
  2005年   36766篇
  2004年   35773篇
  2003年   32549篇
  2002年   32530篇
  2001年   32926篇
  2000年   27409篇
  1999年   23743篇
  1998年   21572篇
  1997年   21437篇
  1996年   21359篇
  1995年   19319篇
  1994年   18824篇
  1993年   17769篇
  1992年   18183篇
  1991年   18385篇
  1990年   17595篇
  1989年   17622篇
  1988年   17265篇
  1987年   17194篇
  1986年   16131篇
  1985年   22604篇
  1984年   23771篇
  1983年   19818篇
  1982年   21398篇
  1981年   20606篇
  1980年   19917篇
  1979年   20437篇
  1978年   21623篇
  1977年   21326篇
  1976年   21076篇
  1975年   19774篇
  1974年   19444篇
  1973年   19961篇
  1972年   14418篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
181.
Aequationes mathematicae - For $$p\in (1,\infty )$$ , we establish several criteria of one-sided invertibility on spaces $$l^p=l^p(\mathbb {Z})$$ for discrete band-dominated operators being either...  相似文献   
182.
183.
Journal of Mathematical Chemistry - The analytical solutions of an asymmetric double well potential $$V(x)=a\, x^2-b\, x^3+c\, x^4$$ are found to be a triconfluent Heun function $$H_{T}(\alpha ,...  相似文献   
184.
Russian Physics Journal - The paper shows that the values of zero-point energy and vibrations of atoms in a crystal determined by the uncertainty principle, depend on the dynamic response of atoms....  相似文献   
185.
Journal of Applied and Industrial Mathematics - We study the problem of optimal location of the ambulance fleet at the base stations. The objective is to minimize the average waiting time for...  相似文献   
186.
187.
188.
A liquid dewetting method for the determination of the viscoelastic properties of ultrathin polymer films has been extended to study thickness effects on the properties of ultrathin polycarbonate (PC) films. PC films with film thicknesses ranging from 4 to 299 nm were placed on glycerol at temperatures from below the macroscopic glass transition temperature (Tg) to above it with the dewetting responses being monitored. It is found that the isothermal creep results for films of the same thickness, but dewetted at different temperatures can be superposed into one master curve, which is consistent with the fact of PC being a thermorheologically simple material. Furthermore, the results show that the Tg of PC thin films is thickness dependent, but the dependence is weaker than the results for freely standing films and similar to literature data for PC films supported on rigid substrates. It was also found that the rubbery plateau region for the PC films stiffens dramatically, but still less than what has been observed for freely standing polycarbonate films. The rubbery stiffening is discussed in terms of a recently reported model that relates macroscopic segmental dynamics with the stiffening. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1559–1566  相似文献   
189.
190.
Given their superior penetration depths, photosensitizers with longer absorption wavelengths present broader application prospects in photodynamic therapy (PDT). Herein, Ag2S quantum dots were discovered, for the first time, to be capable of killing tumor cells through the photodynamic route by near-infrared light irradiation, which means relatively less excitation of the probe compared with traditional photosensitizers absorbing short wavelengths. On modification with polydopamine (PDA), PDA-Ag2S was obtained, which showed outstanding capacity for inducing reactive oxygen species (increased by 1.69 times). With the addition of PDA, Ag2S had more opportunities to react with surrounding O2, which was demonstrated by typical triplet electron spin resonance (ESR) analysis. Furthermore, the PDT effects of Ag2S and PDA-Ag2S achieved at longer wavelengths were almost identical to the effects produced at 660 nm, which was proved by studies in vitro. PDA-Ag2S showed distinctly better therapeutic effects than Ag2S in experiments in vivo, which further validated the enhanced regulatory effect of PDA. Altogether, a new photosensitizer with longer absorption wavelength was developed by using the hitherto-unexplored photodynamic function of Ag2S quantum dots, which extended and enhanced the regulatory effect originating from PDA.  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