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   36篇
  免费   3篇
  国内免费   57篇
化学   86篇
晶体学   6篇
物理学   4篇
  2022年   1篇
  2021年   1篇
  2020年   2篇
  2019年   3篇
  2018年   2篇
  2017年   1篇
  2016年   4篇
  2015年   1篇
  2014年   1篇
  2013年   18篇
  2012年   4篇
  2011年   9篇
  2010年   14篇
  2009年   13篇
  2008年   6篇
  2007年   6篇
  2006年   4篇
  2005年   1篇
  2003年   1篇
  2000年   2篇
  1999年   1篇
  1988年   1篇
排序方式: 共有96条查询结果,搜索用时 15 毫秒
11.
曾广湘  薛郁 《物理学报》2011,60(1):14502-014502
单向行人交通在瓶颈处极易发生堵塞,设置障碍会阻碍行人通行,却能保证瓶颈处通畅.本文将准滑模控制引入LWR模型中,理论推导控制变量.在三车道宏观交通流模型基础上,模拟瓶颈处的障碍对行人流的影响,解释设置障碍的作用.研究表明准滑模控制变量的设置与阈值有关,当阈值对应基本图的流量最大点时,行人流量能保持最大值,达到提高单向行人交通瓶颈处的行人流通过效率. 关键词: 交通瓶颈 准滑模控制 LWR模型  相似文献   
12.
合成得到了2个新的有机-无机杂化化合物{(4-CH3-Bz-4-Ph-Py)[PbI3]}n1)(其中4-CH3-Bz-4-Ph-Py是4-甲基苄基-4-苯基吡啶阳离子)和{(4-CF3-Bz-4-Ph-Py)[PbI3]}n2)(其中4-CF3-Bz-4-Ph-Py是4-三氟甲基苄基-4-苯基吡啶阳离子)。对化合物12进行了元素分析、粉末X射线衍射等表征,并利用X射线单晶衍射测定了它们的单晶结构。化合物1属于正交晶系,P21212空间群;化合物21同构。结构研究表明,化合物12中,铅碘八面体通过共边连接方式,形成[Pb3I9]n三链,有机阳离子填充在无机碘化铅链空隙中。  相似文献   
13.
A nonmagnetic compound, [NO2BzPy][Cu(mnt)2] (mnt2? = maleonitriledithiolate; NO2BzPy+ = 1-(4′-nitrobenzyl)pyridinium), is isostructural with [NO2BzPy][Ni(mnt)2], which is a quasi-1D spin system and exhibits a spin-Peierls-like transition with J = 192 K in the gapless state and spin energy gap = 738 K in the dimerization state, respectively. Further, five nonmagnetic impurity doped compounds [NO2BzPy][CuxNi1?x(mnt)2] (x = 0.04–0.74) were prepared, and their crystal structures as well as magnetic properties were investigated. The nonmagnetic doping causes the suppression of the spin transition with an average rate of 139(13) K/percentage of dopant concentration, and the transition collapse is estimated at around x > 0.5.  相似文献   
14.
以Zn(NO_3)_2·6H_2O和4,4′-(1-咪唑基亚甲基)二苯甲酸(H_2IMB)为原料,在不同溶剂热条件下反应,得到2个结构不同的配合物[Zn(HIMB)_2]_n(1)和{[Zn(IMB)]·1.5H_2O}_n(2),对它们进行了X射线单晶衍射分析、元素分析、红外光谱分析、热重分析和粉末衍射。配合物1属于正交晶系,C222_1空间群,a=0.935 2(3) nm,b=2.583 3(8) nm,c=1.396 4(4) nm,V=3.373 6(18) nm~3,Z=4,M_r=707.98,D_c=1.394 g·cm~(-3),μ=0.786,F(000)=1 456,R_1=0.048 6,wR_2=0.120 1(I2σ(I))。配合物2属于四方晶系,I4_1/acd空间群,a=1.853 5(2) nm,b=1.853 5(2) nm,c=4.309 7(5) nm,V=14.806 (4) nm~3,Z=32,M_r=412.69,D_c=1.481 g·cm~(-3),μ=1.360,F(000)=6 752,R_1=0.043 7,wR_2=0.117 1(I2σ(I))。单晶结构分析显示,配合物1拥有二维二重贯穿聚索烃格子状层状结构,而配合物2具有三维二重贯穿(3,6)-连接(6~(11).8~4)(6~3)_2网状结构。结果说明了溶剂在配合物组装过程中起着非常重要的作用。此外,还研究了2个配合物的荧光性质。  相似文献   
15.
Four molecular solids consisting of the 7,7,8,8-tetracyanoquinodimethane (TCNQ) radical and benzylpyridinium or benzylquinolinium derivatives with molar ratios of 1:1 (1-3) and 2:1 (4) have been prepared and characterized. In the crystals of 1 and 3, TCNQ monoanions and the corresponding cations form segregated stacks, which are regular in 1 but irregular in 3. Instead of segregated stacks, TCNQ monoanions in 2 form isolated π-dimers. In the crystals of 4, two crystallographic independent TCNQ species possess almost equal fractional negative charge (ca. −0.5). Two types of TCNQ species form a tetrad, these tetrads make a TCNQ stack with the pattern …BAAB…BAAB… along the crystallographic a-b direction. The magnetisms for 1-4 can be simply explained by the formation of singlet spin state. A broken symmetry approach in a density functional theory framework at the ub3lyp/6-31 g level was used to calculate the magnetic exchange constants in 1-4. The results qualitatively demonstrate the observed magnetic properties.  相似文献   
16.
Hydrothermal reaction between 1,4-phenylenediacetic acid (H2PDA) and Zn(NO3)2·6H2O at the presence of the second ligand of 1,2-bis((1H-imidazol-1-yl) methyl)benzene (obix) yields a new 2D metal-organic coordination polymer [Zn(PDA)(obix)] (1), which has been characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy and thermal analysis. Complex 1 presents a two-dimensional (2D) sheet structure and displays strong luminescent emission at room temperature. CCDC: 716984.  相似文献   
17.
A coordination polymer of Zn(IBT)2 (2) (HIBT=5-(4-((1H-imidazol-1-yl)methyl)phenyl)-2H-tetrazole) has been prepared by hydrothermal method and characterized by IR spectroscopy,elemental analysis and single-crystal X-ray diffraction structure analysis. Compound 2 has one-dimensional (1D) hinged chain structure and displays strong photoluminescent emission at room temperature.  相似文献   
18.
基于席夫碱配合物的分子磁体:合成、结构和磁学性质;席夫碱;配位聚合物;晶体结构;磁学性质  相似文献   
19.
通过含2-噁唑啉基三角架配体1,3,5-三(2-噁唑啉基)苯(L)与三氟醋酸银反应合成了配合物[Ag4(L)2(CH3CN)2(CF3CO2)4]n (1), 并利用元素分析、电喷雾质谱、X射线单晶衍射等方法对其进行了表征. 晶体结构解析结果显示配合物1属三斜晶系, 空间群P-1, a=0.83731(6) nm, b=1.22828(9) nm, c=1.33997(10) nm, α=102.9760(10)°, β=107.3050(10)°, γ=93.8600(10)°, Z=1, R=0.0365, wR2=0.0929. 该配合物是由[Ag4(L)2(CF3CO2)2]2+笼状结构单元通过另外两个三氟醋酸根双桥连形成的一维链状结构. 相邻的链间通过C—H…O氢键进一步扩展为二维网状结构. 电喷雾质谱研究结果显示在实验条件下, 溶液中配合物1是以聚合状态存在的.  相似文献   
20.
Solid-state light-emitting electrochemical cells (LECs) have several advantages, such as low-voltage operation, compatibility with inert metal electrodes, large-area flexible substrates, and simple solution-processable device architectures. However, most of the studies on saturated red LECs show low or moderate device efficiencies (external quantum efficiency (EQE) <3.3 %). In this work, we demonstrate a series of five red-emitting cationic iridium complexes ( RED1- - RED5 ) with 2,2′-biquinoline ligands and test their electroluminescence (EL) characteristics in LECs. The Commission Internationale de l′Eclairage (CIE) 1931 coordinates for the LECs based on these complexes are all beyond the National Television System Committee (NTSC) red standard point (0.67, 0.33). The maximal EQE of the neat-film RED1 -based LECs reaches 7.4 %. The reddest complex, RED3 , is doped in the blue-emitting host complex, BG , to fabricate host–guest LECs. The maximal EQE of the host–guest LECs (1 wt % complex RED3 ) reaches 9.4 %, which is among the highest reported for the saturated red LECs.  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