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   446篇
  免费   17篇
  国内免费   18篇
化学   297篇
晶体学   1篇
力学   40篇
数学   46篇
物理学   97篇
  2023年   6篇
  2022年   9篇
  2021年   14篇
  2020年   22篇
  2019年   26篇
  2018年   36篇
  2017年   20篇
  2016年   49篇
  2015年   30篇
  2014年   34篇
  2013年   48篇
  2012年   30篇
  2011年   27篇
  2010年   21篇
  2009年   19篇
  2008年   18篇
  2007年   17篇
  2006年   17篇
  2005年   13篇
  2004年   6篇
  2003年   3篇
  2002年   7篇
  2001年   2篇
  1999年   1篇
  1995年   1篇
  1994年   1篇
  1993年   1篇
  1990年   1篇
  1989年   1篇
  1985年   1篇
排序方式: 共有481条查询结果,搜索用时 0 毫秒
41.
Wound healing, one of the most complex processes of the body involving the cooperation of several important biomolecules and pathways, is one of the major therapeutic and economic issues in regenerative medicine. The present study aimed to introduce a novel electrospun curcumin (Cur)‐incorporated chitosan/polyvinyl alcohol/carbopol/polycaprolactone nanofibrous composite for concurrent delivery of the buccal fat pad‐derived mesenchymal stem cells (BFP‐MSCs) and Cur to a full‐thickness wound on the mouse model. Scaffolds were characterized structurally using scanning electron microscopy (SEM), fluorescence microscopy imaging and Fourier‐transform infrared spectroscopy, and toxicity of the scaffolds was also evaluated after BFP‐MSC seeding by SEM imaging and 3‐(4,5 dimethyiazol‐2‐1)‐2‐5‐diphenyl tetrazolium bromide (MTT) assay. Then, its influence on the wound‐healing process was investigated as a wound dressing for a full‐thickness skin defect in mouse model. Results demonstrated that the designed composite scaffolds have the capability for cell seeding and support their growth and proliferation. Macroscopic and histopathological characteristics were evaluated at the end of the 7 and 14 days after surgery, and their results showed that our designed scaffold groups accelerated the wound‐healing process compared with the control group. Among those, scaffold/Cur, scaffold/Cur/BFP‐MSC and scaffold/BFP‐MSC groups demonstrated more wound repair efficacy. These results indicated that the combined grafts can be used to improve the wound‐healing process, and therefore, the electrospun nanofibers presented in this study, Cur and BFP‐MSC together, were demonstrated to have promising potential for wound‐dressing applications.  相似文献   
42.
43.
Vortex shedding in the wake of two-dimensional bluff bodies is usually accompanied by three dimensional instabilities. These instabilities result in streamwise and vertical vorticity components which occur at a certain spanwise wavelength. The spanwise wavelength of the instabilities (λZ) depends on several parameters, including profile geometry and Reynolds number. The objective of the present work is to study the three dimensional wake instabilities for a blunt trailing edge profiled body, comprised of an elliptical leading edge and a rectangular trailing edge, and to manipulate these instabilities to control the aerodynamic forces. Results of numerical simulations of flow around the body at Re(d) = 400, 600, and 1000, as well as planar Laser Induced Fluorescence (LIF) flow visualizations at Re(d) = 600 and 1000 are analyzed to determine the wake vorticity structure and λZ. Based on the findings of these analyses, an active flow control mechanism for attenuation of the fluctuating aerodynamic forces on the body is proposed. The flow control mechanism is comprised of a series of trailing edge injection ports distributed across the span, with a spacing equal to λZ. Injection of a secondary flow leads to amplification of the three dimensional instabilities and disorganization of the von Kármán vortex street. Numerical simulations indicate that the flow control mechanism can attenuate the fluctuating aerodynamic forces at lower Reynolds numbers (Re(d) = 400 and 600) where λZ is constant in time. However, the control mechanism loses its effectiveness at Re(d) = 1000, due to the temporal variations of λZ.  相似文献   
44.
Babai A  Mudring AV 《Inorganic chemistry》2005,44(23):8168-8169
Crystals of [SEt3]3[LnI6] (Ln = Nd, Sm) were obtained by the reaction of LnI2 with the ionic liquid [SEt3][Tf2N] [Tf2N = bis(trifluoromethanesulfonyl)imide]. The compounds are characterized by octahedral [LnI6]3- units that are surrounded by a distorted cube of triethylsulfonium cations.  相似文献   
45.
This paper presents theoretical aspects of a unified generalization for the abstract theory of coherent state/voice transforms over homogeneous spaces of compact groups using operator theory. Let G be a compact group and H be a closed subgroup of G. Let G/H be the left coset space of H in G and \(\mu \) be the normalized G-invariant measure on G/H associated to the Weil’s formula with respect to the probability measures of G, H. Let \((\pi ,\mathcal {H}_\pi )\) be a continuous unitary representation of G with non-zero mean over H. In this article, we introduce the generalized notion of coherent state/voice transform associated to \(\pi \) on the Hilbert function \(L^2(G/H,\mu )\). We then study basic analytic properties of these transforms.  相似文献   
46.
47.
48.
2,3,3‐Trimethylindolenine and 5‐chloro‐2,3,3‐trimethylindolenine were converted into β‐diformyl compounds by the action of the Vilsmeier reagent at 50°C. The dialdehydes reacted with various arylhydrazines and 2‐pyridylhydrazine to produce mono‐hydrazones as mixtures of cis and trans isomers. Heating the hydrazones in refluxing ethanol produced 3,3‐dimethyl‐2‐(1‐aryl‐1H‐pyrazol‐4‐yl)‐3H‐indoles in excellent yields. Reaction of the β‐diformyl compounds with hydrazine itself led directly to 3,3‐dimethyl‐2‐(pyrazol‐4‐yl)‐3H‐indoles.  相似文献   
49.
A wide range of aliphatic or aromatic sulfides are selectively oxidized to the corresponding sulfoxides using ammonium cerium (IV) nitrate (CAN) and a catalytic amount of KBr or NaBr in the presence of wet SiO2 in CH2Cl2 under heterogeneous conditions in moderate to high yields. Correspondence: Mohammad Ali Zolfigol, Faculty of Chemistry, Bu-Ali Sina University, P.O. Box 6517838683, Hamadan, Iran; Kamal Amani, Department of Chemistry, Faculty of Science, University of Kurdistan, P.O. Box 6617715175, Sanandaj, Iran.  相似文献   
50.
Polyfunctional quinolines were synthesized using Friedlander method catalyzed by molecular iodine in high yields at 60 °C under solvent‐free conditions.  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