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   197篇
  免费   25篇
  国内免费   31篇
化学   158篇
晶体学   2篇
力学   8篇
综合类   1篇
数学   63篇
物理学   21篇
  2024年   1篇
  2023年   13篇
  2022年   19篇
  2021年   18篇
  2020年   21篇
  2019年   30篇
  2018年   18篇
  2017年   16篇
  2016年   21篇
  2015年   26篇
  2014年   15篇
  2013年   10篇
  2012年   13篇
  2011年   7篇
  2010年   8篇
  2009年   7篇
  2008年   4篇
  2007年   3篇
  2006年   1篇
  2004年   1篇
  2003年   1篇
排序方式: 共有253条查询结果,搜索用时 15 毫秒
141.
142.
The metal‐organic frameworks (MOFs), {[Cd(L)(H2O)] · CH3OH · DMF} ( 1 ) and [Pb(L)(DMF)] ( 2 ) (L = 2,4‐dihydroxybenzaldehyde nicotinoylhydrazone), were synthesized and characterized using microanalyses, IR spectroscopy, and single‐crystal X‐ray diffraction. Single crystal X‐ray analyses revealed that both 1 and 2 exhibit 2D grid networks. The photoluminescence investigation indicates that 1 and 2 could be a prospective candidate for developing luminescencent sensors for the selective sensing of nitrobenzene, which is used as a precursor for explosives. The luminescent properties of 1 and 2 in different solvents were investigated and corroborated by theoretical calculations. Additionally compounds 1 and 2 also show selective sensing ability for Fe3+ as well as for CrO42– ions.  相似文献   
143.
以稻壳基二氧化硅/碳复合材料(SiCB)作为天然橡胶(NR)的补强填料, 采用表面化学改性的方法将天然乳胶(NRL)接枝到SiCB表面, 改善其与NR基体的相容性. 研究了不同处理方法对接枝NRL效率的影响, 以及填料填入NR后对硫化橡胶力学性能的影响. 结果表明, 经过硝酸和γ-(甲基丙烯酰氧)丙基三甲氧基硅烷(γ-MPTMS)预处理, NRL能高效接枝在SiCB表面, 得到的样品SiCBMR10比未处理的SiCBP有更强的补强能力. 硫化胶NR/SiCBMR10的拉伸强度、 300%定伸和撕裂强度较NR/SiCBP分别提高了61.06%, 27.15%和15.90%, 与传统炭黑产品N774填充的硫化胶NR/N774的力学性能相近. 经过NRL接枝改性的SiCBMR10具有替代商业炭黑的应用前景.  相似文献   
144.
中空介孔二氧化硅锚固聚偕胺肟吸附Cr(Ⅵ)   总被引:1,自引:0,他引:1  
以硝酸铈铵为引发剂,在自制的中空介孔二氧化硅(HMS)的空腔和通道内引发丙烯腈自由基聚合,并将其氰基偕胺肟化,用于制备具有吸附Cr(Ⅵ)的廉价有机无机复合吸附材料——中空介孔二氧化硅锚固聚偕胺肟.通过傅里叶变换红外光谱(FTIR)、扫描电子显微镜(SEM)及N_2吸附-脱附比表面分析对中空介孔二氧化硅锚固聚偕胺肟进行表征.结果表明,制备的中空微球直径约为400 nm,其壁上孔径约为11.0 nm,比表面积约为431 m~2/g,锚固聚偕胺肟后中空微球壁上孔道直径约为4.6 nm,比表面积降低为347 m~2/g.HMS锚固的聚偕胺肟对重铬酸钾溶液中铬的吸附量高达0.46 mmol/g,吸附过程中伴随化学反应,符合伪二级动力学模型,可用作废水处理中重金属离子的高效廉价吸附材料.  相似文献   
145.
Du  Miaomiao  Zhao  Dingxuan  Yang  Mengke  Chen  Hao 《Nonlinear dynamics》2020,100(3):2483-2503
Nonlinear Dynamics - This paper proposes a nonlinear extended state observer-based output feedback stabilization controller for a half-car active suspension system, to overcome factors leading to...  相似文献   
146.
Xing  Miaomiao  Song  Xinlin  Yang  Zhuoqin  Chen  Yong 《Nonlinear dynamics》2020,100(3):2687-2698
Nonlinear Dynamics - The neuronal excitability related to the transition between firing and resting states is a basic and important dynamic behavior which has different bifurcation characteristics...  相似文献   
147.
本文通过数值模拟的方法,研究了零重力条件下半浮区液桥内熔体热毛细对流的演化规律。在液桥的高度L和温差ΔT保持不变的情况下,通过改变液桥的半径R来改变液桥的高径比(Ar=L/R)。随着高径比Ar的变化,液桥内的对流表现出不同的流动特征。在Ar=0.5时,热毛细对流处于三维稳态;在Ar=1时,流场和温度场从稳态模式向非稳态周期多频振荡模式转变,它们之间的频率关系满足倍频关系(fn=nf1);在Ar=1.25时,监测点的速度振荡频率增大,表现为较小幅度的振荡模式,且温度振荡消失。  相似文献   
148.
Polythiophenes,with merits of low cost and high scalability of synthesis,have received growing interest in organic solar cells.To date,the best-performing polythiophene:nonfullerene solar cells exhibit typical power conversion efficiencies (PCEs) of 10%–12%,which is much lower than those employing PM6-and D18-type polymers.This inferior performance is mostly limited by the improper miscibility between polythiophene and acceptors.Efforts on engineering the molecular structure to systematically tune the miscibility are required.With the aid of group contribution calculations,the miscibility of polythiophene:nonfullerene blend system was finely tuned by varying the ratios of siloxane-terminated chains and alkyl chains in ester-substituted polythiophenes through random copolymerization.Based on a series of the polythiophene and nonfullerene acceptors,the detailed analysis of blend miscibility and performance reveals a surprising anticorrelation between the Flory-Huggins interaction parameter (χaa) and the optimal time of solvent vapor annealing for device performance across these systems.Primarily due to the slightly higher χaa,the blend of PDCBT-Cl-Si5 and ITIC-Th1 results in a record-high PCE of 12.85%in polythiophene:nonfullerene solar cells.The results not only provide a calculation-guided approach for molecular design but also prove that precise control of the miscibility is an effective way to design high-performance polythiophene:nonfullerene blends and beyond.  相似文献   
149.
平坦半环是一类重要的加法幂等元半环,它在半环簇理论的研究中扮演着重要的角色.主要研究了次直不可约的平坦半环,以及一类平坦半环生成的簇.给出了次直不可约的nil-平坦半环的等价刻画,证明了当n小于4时,平坦半环S(x1x2···xn)均是有限基底的.  相似文献   
150.
Controlling ions transport across the membrane at different pH environments is essential for the physiological process and artificial systems.Many efforts have been devoted to pH-responsive ion gating,while rarely systems can maintain the rectification in pH-changing environments.Here,a composite nanochannel system is fabricated,which shows unidirectional rectification with high performance in a wide pH range.In the system,block copolymer(BCP) and polyethylene te rephthalate(PET) are employed for the amphoteric nanochannels fabrication.Based on the composite system,a model is built for the theoretical simulation.Thereafter,rectification mapping is conducted on the system,which can provide abundant info rmation about the relations between charge distribution and ions transport prope rties.The proposed rectification mapping can definitely help to design new materials with special ion transport properties,such as high-performance membranes used in the salinity gradient power generation field.  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