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   196篇
  免费   51篇
  国内免费   33篇
化学   136篇
晶体学   2篇
力学   7篇
综合类   11篇
数学   17篇
物理学   107篇
  2023年   6篇
  2021年   4篇
  2020年   1篇
  2019年   4篇
  2018年   1篇
  2017年   2篇
  2016年   5篇
  2015年   3篇
  2014年   3篇
  2013年   5篇
  2011年   10篇
  2010年   2篇
  2009年   7篇
  2008年   6篇
  2007年   4篇
  2006年   8篇
  2005年   4篇
  2004年   7篇
  2003年   35篇
  2002年   45篇
  2001年   47篇
  2000年   26篇
  1999年   20篇
  1998年   2篇
  1997年   3篇
  1995年   2篇
  1994年   1篇
  1992年   1篇
  1991年   1篇
  1990年   1篇
  1989年   1篇
  1988年   4篇
  1985年   1篇
  1979年   1篇
  1917年   5篇
  1916年   1篇
  1902年   1篇
排序方式: 共有280条查询结果,搜索用时 171 毫秒
11.
采用基于密度泛函理论的总体能量平面波超软赝势方法,对贵金属(Cu、Ag、Au)掺杂ZnO进行了几何结构优化,并计算了相应的能带结构、受主能级、形成能、电子态密度和光学性质. 结果表明:贵金属掺杂后带隙增加且体系费米能级附近电子态密度主要来源于Cu3d、Ag4d和Au5d态电子的贡献. 与未掺杂ZnO相比,介电函数虚部、反射峰强度和吸收系数在可见光和紫外区域增强. 能量损失谱计算表明,贵金属(Cu、Ag、Au)掺杂后ZnO的等离子体共振频率峰发生蓝移.  相似文献   
12.
设c0,c1,…,cn均为实的常数,F(x)是个从R到R的C^m映射。本文讨论了非齐次线性差分方程∑i=1ncif(x i)=F(x)的C^m(m≥0)的存在性和唯一性。  相似文献   
13.
基态和激发态氧振动光谱的量子力学计算   总被引:3,自引:0,他引:3       下载免费PDF全文
利用分子势能函数的Murrell-Sorbie和PG函数形式,将时域有限差分法应用基态和激发态氧分子的振动能级的量子力学计算,计算结果令人满意.  相似文献   
14.
TiO2薄膜的结构和光学性质的研究   总被引:9,自引:0,他引:9  
以金属钛为靶材,用反应射频溅射法制备了TiO2薄膜,并在600-900℃下进行了热处理,经XRD测量,在600-800℃下TiO2薄膜为锐钛矿和金红石两种结构的混合态,在900℃下TiO2薄膜为纯金红石结构,研究TiO2薄膜的SEM照片和UV-vis透射光谱发现,不同的热处理温度会影响TiO2薄膜中锐矿和金红石两种结构的比例,从而导致TiO2薄膜的微观形貌,折射率,禁带宽度等性质的变化。  相似文献   
15.
A convenient synthetic approach for the preparation of uniform metallopolymer‐containing hollow spheres based on 2‐(methacryloyloxy)ethyl ferrocenecarboxylate (FcMA) as monomer by sequential starved feed emulsion polymerization is described. Core/shell particles consisting of a noncrosslinked poly(methyl methacrylate) core and a slightly crosslinked ferrocene‐containing shell allows for the simple dissolution of core material and, thus, monodisperse metallopolymer hollow spheres are obtained. Since PFcMA is incorporated in the particle shell, herein investigated hollow spheres can be addressed by external triggers, i.e., solvent variation and redox chemistry in order to change the particle swelling capability. PFcMA‐containing core/shell particles and hollow spheres are characterized by transmission electron microscope (TEM), scanning electron microscopy, cryogenic TEM, thermogravimetric analysis, and dynamic light scattering in terms of size, size distribution, hollow sphere character, redox‐responsiveness, and composition. Moreover, the general suitability of prepared stimulus‐responsive nanocapsules for the use in catch‐release systems is demonstrated by loading the nanocapsules with malachite green as model payload followed by release studies.

  相似文献   

16.
We demonstrate, for the first time, the synthesis of model poly(benzyl methacrylate) [P(BnMA)] brushes of very high thickness (>300 nm) on silicon wafer. P(BnMA) brush is also synthesized from the surface of silica nanoparticles, from a covalently anchored initiator monolayer, using ambient temperature ATRP. The kinetic studies and block copolymerization from the surface anchored P(BnMA)-Br macroinitiator showed that the polymerization was controlled in nature. AFM, ellipsometry, and water contact angle were used for the characterization of the polymer brush. The grafting density of the P(BnMA) brush, formed by immersion in a dilute monomer solution, was relatively less (~11% less) in comparison to that obtained by immersion in neat monomer under similar conditions. The P(BnMA)-Br macroinitiator brushes were used to synthesize P(BnMA-b-S) diblock copolymer brushes by the ATRP of styrene at 95 °C. The P(BnMA-b-S) brushes showed stimulus response to a selective solvent and various nanopatterns were observed according to the composition of the block copolymer.  相似文献   
17.
For the miniaturization of biological assays, especially for the fabrication of microarrays, immobilization of biomolecules at the surfaces of the chips is the decisive factor. Accordingly, a variety of binding techniques have been developed over the years to immobilize DNA or proteins onto such substrates. Most of them require rather complex fabrication processes and sophisticated surface chemistry. Here, a comparatively simple immobilization technique is presented, which is based on the local generation of small spots of surface attached polymer networks. Immobilization is achieved in a one-step procedure: probe molecules are mixed with a photoactive copolymer in aqueous buffer, spotted onto a solid support, and cross-linked as well as bound to the substrate during brief flood exposure to UV light. The described procedure permits spatially confined surface functionalization and allows reliable binding of biological species to conventional substrates such as glass microscope slides as well as various types of plastic substrates with comparable performance. The latter also permits immobilization on structured, thermoformed substrates resulting in an all-plastic biochip platform, which is simple and cheap and seems to be promising for a variety of microdiagnostic applications.  相似文献   
18.
The rapid atom transfer radical polymerization (ATRP) of benzyl methacrylate (BnMA) at ambient temperature was used to synthesize block copolymers with styrene as the second monomer. Various block copolymers such as AB diblock, BAB symmetric and asymmetric triblock, and ABABA pentablock copolymers were synthesized in which the polymerization of one of the blocks namely BnMA was performed at ambient temperature. It is demonstrated that the block copolymerization can be performed in a controlled manner, regardless of the sequence of monomer addition via halogen exchange technique. Using this reaction condition, the composition (ratio) of one block (here BnMA) can be varied from 1 to 100. It is further demonstrated that in the multiblock copolymer syntheses involving styrene and benzyl methacrylate, it is better to start from the PS macroinitiator compared with PBnMA macroinitiator. The polymers synthesized are relatively narrow dispersed (<1.5). It is identified that the ATRP of BnMA is limited to certain molecular weights of the PS macroinitiator. Additionally, a preliminary report about the synthesis of the block copolymer of BnMA‐methyl methacrylate (MMA), both at ambient temperature, is demonstrated. Subsequent deprotection of the benzyl group using Pd/C? H2 results in methacrylic acid (MAA)–methyl methacrylate (MAA–MMA) amphiphilic block copolymer. GPC, IR, and NMR are used to characterize the synthesized polymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2848–2861, 2006  相似文献   
19.
20.
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