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   760篇
  免费   237篇
  国内免费   95篇
化学   367篇
晶体学   21篇
力学   77篇
综合类   12篇
数学   172篇
物理学   443篇
  2024年   5篇
  2023年   12篇
  2022年   33篇
  2021年   44篇
  2020年   32篇
  2019年   31篇
  2018年   36篇
  2017年   35篇
  2016年   66篇
  2015年   32篇
  2014年   49篇
  2013年   91篇
  2012年   62篇
  2011年   64篇
  2010年   44篇
  2009年   40篇
  2008年   42篇
  2007年   57篇
  2006年   38篇
  2005年   30篇
  2004年   35篇
  2003年   19篇
  2002年   26篇
  2001年   17篇
  2000年   31篇
  1999年   12篇
  1998年   14篇
  1997年   23篇
  1996年   7篇
  1995年   4篇
  1994年   8篇
  1993年   6篇
  1992年   9篇
  1991年   3篇
  1990年   2篇
  1989年   2篇
  1988年   6篇
  1987年   6篇
  1986年   4篇
  1985年   2篇
  1984年   6篇
  1982年   2篇
  1980年   1篇
  1979年   1篇
  1977年   1篇
  1976年   1篇
  1974年   1篇
排序方式: 共有1092条查询结果,搜索用时 8 毫秒
1.
In this paper we discuss an initial-boundary value problem for a stochastic nonlinear equation arising in one-dimensional viscoelasticity. We propose to use a new direct method to obtain a solution. This method is expected to be applicable to a broad class of nonlinear stochastic partial differential equations.

  相似文献   

2.
介绍了几种光纤干涉仪等臂长技术,比较了各自的优缺点和适用范围,对光纤干涉仪的平衡有较大的参考价值。  相似文献   
3.
Two orange phosphorescent iridium complex monomers, 9‐hexyl‐9‐(iridium (III)bis(2‐(4′‐fluorophenyl)‐4‐phenylquinoline‐N,C2′)(tetradecanedionate‐11,13))‐2,7‐dibromofluorene (Br‐PIr) and 9‐hexyl‐9‐(iridium(III)bis(2‐(4′‐fluorophenyl)‐4‐methylquinoline‐N,C2′)(tetradecanedionate‐11,13))‐2,7‐dibromofluorene (Br‐MIr), were successfully synthesized. The Suzuki polycondensation of 2,7‐bis(trimethylene boronate)‐9,9‐dioctylfluorene with 2,7‐dibromo‐9,9‐dioctylfluorene and Br‐PIr or Br‐MIr afforded two series of copolymers, PIrPFs and MIrPFs, in good yields, in which the concentrations of the phosphorescent moieties were kept small (0.5–3 mol % feed ratio) to realize incomplete energy transfer. The photoluminescence (PL) of the copolymers showed blue‐ and orange‐emission peaks. A white‐light‐emitting diode with a configuration of indium tin oxide/poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate)/PIr05PF (0.5 mol % feed ratio of Br‐PIr)/Ca/Al exhibited a luminous efficiency of 4.49 cd/A and a power efficiency of 2.35 lm/W at 6.0 V with Commission Internationale de L'Eclairage (CIE) coordinates of (0.46, 0.33). The CIE coordinates were improved to (0.34, 0.33) when copolymer MIr10PF (1.0 mol % feed ratio of Br‐MIr) was employed as the white‐emissive layer. The strong orange emission in the electroluminescence spectra in comparison with PL for these kinds of polymers was attributed to the additional contribution of charge trapping in the phosphorescent dopants. © 2007 Wiley Periodicals, Inc. JPolym Sci Part A: Polym Chem 45: 1746–1757, 2007  相似文献   
4.
一类广义维里拉普拉斯,把在白噪声分析构架中通常定义的维里拉普拉斯作为特殊情形而包含。  相似文献   
5.
The mechanism of the electrosynthesis of phosphate esters from white phosphorus was investigated. It was shown that the reaction takes place by two paths, i.e., monomeric (with the participation of dissolved phosphorus) and polymeric (with the participation of phosphorus on the surface of an emulsion drop). It was established that in an alcohol solution of tetraethylammonium iodide the main part of the final product is formed through an intermediate polymeric compound. It was noticed that by studying the dynamics of the accumulation of the dissolved product during electrolysis it is possible to trace the mechanism of reaction of the phosphorus at the individual stages of the process.A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan' Scientific Center, Russian Academy of Sciences, 420028 Kazan'. V. I. Ul'yanov-Lenin Kazan' State University, 420028 Kazan'. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1328–1333, June, 1992.  相似文献   
6.
一种新型有机电致微腔结构的双模发射   总被引:4,自引:4,他引:0  
采用结构Glass/DBR/ITO/NPB/NPB:Alq/Alq/Al制作了有机微腔电致发光器件。将空穴传输材料与发光材料以一定比例混合作为发光层,为了便于对比,在不改变有机层的膜厚的情况下同时制作了传统的异质结微腔器件,发现两种器件的发光光谱有很大不同,器件的复合效率与传统的异质结器件相比也得到了很大提高,这是因为将两种有机材料混合能消除界面势垒,提高器件的复合效率,从而提高了器件的发光性能,实现了微腔双模发射,且两个模式的半峰全宽分别为8nm和12nm。通过进一步优化器件结构可以实现微腔白光发射。  相似文献   
7.
负关联噪声驱动下单模激光的定态分析   总被引:2,自引:1,他引:1  
魏学勤  曹力 《光学学报》1996,16(3):78-281
研究了负关联的加法和乘法高斯白噪声驱动下单模激光损失模型的定态情况。文中推导了负关联情况下,定态时的激光场幅的几率分布,光强的平均值,光强的协方差以及光强的偏斜率。并和文献〔1,2〕中正关联时的定态分析作了比较,发现了有意义的新现象。  相似文献   
8.
The monodisperse, porous poly(chloromethylstyrene-co-divinylbenzene) beads of 7.9 microm were prepared by a single-step swelling and polymerization method. The seed particles prepared by dispersion polymerization exhibited good absorption of the monomer phase. Based on this media, a weak cation-exchange (WCX) stationary phase for HPLC was synthesized by a new chemically modified method. The prepared resin has advantages of biopolymer separation, high column efficiency, low column backpressure, high protein mass recovery, and good resolution for proteins. The dynamic protein-loading capacity of the synthesized WCX packings was 18.2 mg/g. Five proteins were separated in 3.0 min using the synthesized WCX stationary phase. The experimental results show that the obtained WCX resin has very weak hydrophobicity. The WCX resin was also used for the rapid separation and purification of lysozyme from egg white in 5.0 min with only one step. The purity and specific bioactivity of the purified lysozyme were found to be more than 93% and 70 245 U/mg, respectively.  相似文献   
9.
The disadvantages of Normally White Twisted Nematic Liquid Crystal Display (NW-TN-LCD) were discussed. The reason that the negative birefringent polyimide thin filmswere used to compensate NW-TN-LCD to decrease off-axis leakage, improve contrast ratiosand enlarge viewing angles was explained in this paper. A certain polyimide thin film wastaken as an example to show compensation effect on NW-TN-LCD.  相似文献   
10.
Three new serratanes were isolated from the nonsaponifiable fraction of western white pine (Pinus monticola Dougl.) bark. The compounds were shown to be 3β-methoxyserrat-14-ene-21α,30-diol (8a), 3β-methoxyserrat-14-ene-21α, 29-diol (9a), and 3β-methoxyserrat-14-ene-21β,30-diol (10a), by a combination of chemical, and spectral methods.  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