全文获取类型
收费全文 | 167篇 |
免费 | 18篇 |
国内免费 | 41篇 |
专业分类
化学 | 158篇 |
晶体学 | 5篇 |
力学 | 4篇 |
综合类 | 9篇 |
数学 | 19篇 |
物理学 | 31篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 4篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 8篇 |
2015年 | 5篇 |
2014年 | 6篇 |
2013年 | 10篇 |
2012年 | 10篇 |
2011年 | 5篇 |
2010年 | 12篇 |
2009年 | 6篇 |
2008年 | 14篇 |
2007年 | 9篇 |
2006年 | 8篇 |
2005年 | 6篇 |
2004年 | 4篇 |
2003年 | 13篇 |
2002年 | 26篇 |
2001年 | 17篇 |
2000年 | 14篇 |
1999年 | 18篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 4篇 |
排序方式: 共有226条查询结果,搜索用时 15 毫秒
131.
Throughout this paper, we adopt the same notations as in [1,6, 8] such as the Möbius group M(Rn), the Clifford algebraCn1, the Clifford matrix group SL(2, n), the Cliffordnorm of
||A||=(|a|2+|b|2+|c|2+|d|2) (1) and the Clifford metric of SL(2, n) or of the Möbius groupM(Rn) d(A1,A2)=||A1A2||(|a1a2|2+|b1b2|2+|c1c2|2+|d1d2|2)(2) where |·| is the norm of a Clifford number and
represents fi M(), i = 1,2, and so on. In addition, we adopt some notions in [6, 12]:the elementary group, the uniformly bounded torsion, and soon. For example, the definition of the uniformly bounded torsionis as follows. 相似文献
132.
Assembly,Structures, and Properties of a Series of Metal‐Organic Coordination Polymers Derived from a Semi‐rigid Bis‐pyridyl‐bis‐amide Ligand
下载免费PDF全文
![点击此处可从《无机化学与普通化学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Xiu‐Li Wang Xiao‐Ting Sha Guo‐Cheng Liu Nai‐Li Chen Chun‐Hua Gong Yun Qu 《无机化学与普通化学杂志》2015,641(7):1274-1281
Four metal‐organic coordination polymers [Cd(4‐bpcb)1.5Cl2(H2O)] ( 1 ), [Cd(4‐bpcb)0.5(mip)(H2O)2] · 3H2O ( 2 ), [Co(4‐bpcb)(oba)(H2O)2] ( 3 ), and [Ni(4‐bpcb)(oba)(H2O)2] ( 4 ) [4‐bpcb = N,N′‐bis(4‐pyridinecarboxamide)‐1, 4‐benzene, H2mip = 5‐methylisophthalic acid, and H2oba = 4, 4′‐oxybis(benzoic acid)] were synthesized under hydrothermal conditions and characterized by single‐crystal X‐ray diffraction, elemental analyses, IR spectroscopy, powder X‐ray diffraction, and TG analysis. In complex 1 , two Cl– anions serve as bridges to connect two Cd‐(μ1‐4‐bpcb) subunits forming a dinuclear unit, which are further linked by μ2‐bridging 4‐bpcb to generate 1D zigzag chain. Complex 2 shows a 2D 63 network constructed by [Cd‐mip]n zigzag chains and μ2‐bridging 4‐bpcb ligands. Complexes 3 and 4 are isostructural 2D (4, 4) grid networks derived from [M‐oba]n (M = Co, Ni) zigzag chains and [M‐(4‐bpcb)]n linear chains. The 1D chains for 1 and the 2D networks for 2 – 4 are finally extended into 3D supramolecular architectures by hydrogen bonding interactions. The roles of dicarboxylates and central metal ions on the assembly and structures of the target compounds were discussed. Moreover, the thermal stabilities, photoluminescent properties, and photocatalytic activities of complexes 1 – 4 and the electrochemical properties of complexes 3 and 4 were investigated. 相似文献
133.
High Final Energy of Low‐Level Gallium Arsenide Laser Therapy Enhances Skeletal Muscle Recovery without a Positive Effect on Collagen Remodeling
下载免费PDF全文
![点击此处可从《Photochemistry and photobiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Carlos Eduardo Assumpção de Freitas Raquel Santilone Bertaglia Ivan José Vechetti Júnior Edson Assunção Mareco Rondinelle Artur Simões Salomão Tassiana Gutierrez de Paula Gisele Alborghetti Nai Robson Francisco Carvalho Francis Lopes Pacagnelli Maeli Dal‐Pai‐Silva 《Photochemistry and photobiology》2015,91(4):957-965
The aim of this study was to evaluate the effects of a Gallium Arsenide (GaAs) laser, using a high final energy of 4.8 J, during muscle regeneration after cryoinjury. Thirty Wistar rats were divided into three groups: Control (C, n = 10); Injured (I, n = 10) and Injured and laser treated (Injured/LLLT, n = 10). The cryoinjury was induced in the central region of the tibialis anterior muscle (TA). The applications of the laser (904 nm, 50 mW average power) were initiated 24 h after injury, at energy density of 69 J cm?1 for 48 s, for 5 days, to two points of the lesion. Twenty‐four hours after the final application, the TA muscle was removed and frozen in liquid nitrogen to assess the general muscle morphology and the gene expression of TNF‐α, TGF‐β, MyoD, and Myogenin. The Injured/LLLT group presented a higher number of regenerating fibers and fewer degenerating fibers (P < 0.05) without changes in the collagen remodeling. In addition, the Injured/LLLT group presented a significant decrease in the expression of TNF‐α and myogenin compared to the injured group (P < 0.05). The results suggest that the GaAs laser, using a high final energy after cryoinjury, promotes muscle recovery without changing the collagen remodeling in the muscle extracellular matrix. 相似文献
134.
Polypropylene(PP) composites containing magnesium oxysulfate whisker(MOSw) or lauric acid(LA) modified MOSw(LAMOSw) were prepared via melt mixing in a torque rheometer. The heterogeneous nucleating effect of LAMOSw was clearly observed in polarized light microscopy(PLM) pictures with the presence of an abundance of small spherulites. MOSw exhibited no nucleation effect and formed a few spherulites with large size. Compared with PP/MOSw composites, PP/LAMOSw exhibited better impact strength, tensile strength and nominal strain at break, ascribing to three possible reasons:(i) more β-crystal PP formed,(ii) better dispersity of LAMOSw in PP matrix and(iii) the plasticizing effect of LA. The results of dynamic mechanical thermal analysis(DMTA) indicated that brittleness of the PP matrix at low temperature was improved by the addition of LAMOSw, while the interfacial interactions between MOSw and PP matrix were actually weakened by LA, as evidenced by the higher tanδ values over the entire range of test temperatures. In terms of the rheological properties of the composites, both the η* and G′ at low frequencies increase with the addition of MOSw or LAMOSw, indicating that the PP matrix was transformed from liquid-like to solid-like. However, a network of whiskers did not form because no plateau was found in the G′ at low frequencies. With low filler content, LAMOSw produced a stronger solid-like behavior than MOSw mainly due to the better dispersion of the LAMOSw in PP matrix. However, for highly-filled composites, the η* of PP/LAMOSw at low frequencies was smaller than that of PP/MOSw composite, since the particleparticle contact effect played a major role. 相似文献
135.
纳米粒子TiO2/Ti膜的表征及其光催化活性 总被引:15,自引:0,他引:15
以钛酸四丁酯为原料,采用溶胶-凝胶法,在600℃焙烧制备了纳米粒子TiO2/Ti膜,并利用TG-DTA,XRD、SEM、XPS、PL、SPS和EFISPS测试技术,对膜样品进行了表征。结果表明,纳米粒子TiO2/Ti膜表面为高密度的均匀碎片结构,TiO2纳米粒子具有与国际P-25TiO2粒子相类似的组成、结构以及微晶尺寸;在纳米粒子TiO2/Ti膜的表面,Ti主要以+4价化学态存在。而O主要以晶格氧、羟基氧和吸附氧3种化学态存在。以纳米粒子TiO2/Ti膜的PL光谱测试中,以260nm为激发波长,观察到了峰位在380nm处的PL光谱,该值与SPS信号的响应阈值是一致的,此PL光谱峰可能与导带低的电子向价带顶的能级跃迁有关,同时说明了TiO2纳米粒子的量子尺寸效应的影响要大于库仑作用能和表面极化能的影响。以310nm为激发波长,分别观察到了与锐钛矿和金红石相关的发光信号;以450nm为激发波长,观察到了与表面态相关的弱的发光信号。此外,在光催化降解苯酚实验中,当涂膜3次时,TiO2粒子膜达到最高的光催化活性。 相似文献
136.
CO在某些过渡金属表面吸附活化的DFT研究 总被引:8,自引:0,他引:8
采用DFT方法对CO在M(100)(M= Cu、Ag、Au、Pd、Pt)表面上的吸附行为进行了系统的比较性研究.结果表明,CO分子在这些过渡金属单晶表面上发生的是非解离性吸附,吸附后C-O键长都变长了,均不同程度地削弱了C-O键,继而活化了CO分子;从表面结合能、重叠集居数、轨道电子数变化等方面分析了成键强弱顺序,发现CO的吸附强度随Pd(100)、Pt (100)、Cu (100)、Ag(100)、Au(100)顺序依次减弱,并且将CO与过渡金属间的结合能(BE)、过渡金属的d电子转移数分别与水煤气变换反应活性数据进行了关联,在定性上比较好地解释了金属铜的催化活性优于其它金属的原因. 相似文献
137.
138.
Mechanism of gold solvent extraction from aurocyanide solution by quaternary amines: models of extracting species based on hydrogen bonding 总被引:6,自引:0,他引:6
The mechanism of gold solvent extraction from KAu(CN)2 solution was investigated by means of FTIR, EXAFS, ICP and radioactive tracer methods. Two extraction systems were studied, namely N263-tributyl phosphate(TBP)-n-dodecane and N263-iso-octanol-n-dodecane. High-resolution FT IR spectroscopy indicated that the CN stretching vibrations of the two extraction systems differred greatly. In order to interpret the significant difference in CN stretching vibrations, two
extracting species models are proposed——supramolecular structures based on the formation of
hydrogen bonds between Au(CN)2- and modifiers such as TBP and iso-octanol. 相似文献
139.
140.
In this paper, we give an equitable presentation for the multiparameter quantum group associated to a symmetrizable Kac–Moody Lie algebra, which can be regarded as a natural generalization of the Terwilliger's equitable presentation for the one-parameter quantum group. 相似文献