全文获取类型
收费全文 | 270篇 |
免费 | 2篇 |
国内免费 | 52篇 |
专业分类
化学 | 163篇 |
晶体学 | 3篇 |
力学 | 24篇 |
数学 | 35篇 |
物理学 | 99篇 |
出版年
2023年 | 11篇 |
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 7篇 |
2019年 | 3篇 |
2018年 | 1篇 |
2017年 | 9篇 |
2016年 | 15篇 |
2015年 | 11篇 |
2014年 | 8篇 |
2013年 | 16篇 |
2012年 | 14篇 |
2011年 | 22篇 |
2010年 | 13篇 |
2009年 | 22篇 |
2008年 | 14篇 |
2007年 | 12篇 |
2006年 | 31篇 |
2005年 | 10篇 |
2004年 | 11篇 |
2003年 | 12篇 |
2002年 | 4篇 |
2001年 | 12篇 |
2000年 | 7篇 |
1999年 | 11篇 |
1998年 | 4篇 |
1997年 | 8篇 |
1996年 | 2篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有324条查询结果,搜索用时 31 毫秒
141.
LI Xiao-ling ZHAO Bing WU Yu-qing XU Wei-qing LI Guo-wen WU Ying BAI Fang CUI Shu-wen 《高等学校化学研究》1998,14(4):395-398
IntroductionInrecentyears,Langmuir-Blodget(LB)filmshaveatractedmuchatentionbecauseoftheirposibilitiesasfunctionalmoleculardev... 相似文献
142.
The quasiclassical trajectory method is used to study the vector correlations of the reactions Ca+RBr (R=CH3, C2H5 and n-C3H7Br) and the rotational alignment of product CaBr. The product rotational alignment parameters at di?erent collision energies and the vector correlations between the reagent and product are numerically calculated. The vector correlations are described by using the angle distribution functions P(θr),P(φr), P(θr, φr) and the polarization-dependent differential cross sections (PDDCSs). The peak values of P(θr) of the product CaBr from Ca+CH3Br are larger than those from Ca+C2H5Br and Ca+n-C3H7Br. The peak of P(θr) atφr = 3π/2 is apparently stronger than that at φr= π/2 for the three reactions Ca+RBr. The calculation results show that the rotational angular momentum of the product CaBr is not only aligned, but also oriented along the direction which is perpendicular to the scattering plane.The product CaBr molecules are strongly scattered forward. The orientation and alignment of the product angular momentum will affect the scattering direction of the product molecules to varying degrees. 相似文献
143.
本文结合分子动力学、密度泛函理论和蒙特卡洛方法,研究了光学损耗低的氟化聚合物单体分子甲基丙烯酸三氟乙酯(TFMA)及其分子链在[Zn2(BDC)2TED]n和[Zn2(BPDC)2TED]n两种结构有序的金属有机框架(MOFs)材料中的吸附特性,得到相应的吸附数量和取向程度,以探索提高聚合物材料双折射性的有效途径。通过分析结果得出影响TFMA单体分子在这两种MOF孔道中吸附及取向特性的三个因素:a)由于MOF孔道壁是由金属离子和有机配体组成的极性表面,MOF孔壁与极性分子TFMA之间的静电相互作用对TFMA单体分子在孔道内的吸附和取向有促进作用;b)在受限空间中的聚合物单体分子之间的静电相互作用使其分子间隙更加紧密,同样也对其分子取向有促进作用;c)在这个两种孔洞与聚合物单体分子相对大小不同的MOF中,单体分子和分子链的取向度基本一致,但单体分子在孔径较大的MOF中吸附数量更多。这三个因素的重要影响,为聚合物单体或MOF的选取、对聚合物链取向及双折射性的控制提供理论预测方法。 相似文献
144.
Hai Guo Xudong Yang Teng Xiao Weiping Zhang Liren Lou Jacques Mugnier 《Applied Surface Science》2004,230(1-4):215-221
Pure and rare earth doped gadolinium oxide (Gd2O3) waveguide films were prepared by a simple sol–gel process and dip-coating method. Gd2O3 was successfully synthesized by hydrolysis of gadolinium acetate. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were used to study the thermal chemistry properties of dried gel. Structure of Gd2O3 films annealed at different temperature ranging from 400 to 750 °C were investigated by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that Gd2O3 starts crystallizing at about 400 °C and the crystallite size increases with annealing temperature. Oriented growth of (4 0 0) face of Gd2O3 has been observed when the films were deposited on (1 0 0) Si substrate and annealed at 750 °C. The laser beam (λ=632.8 nm) was coupled into the film by a prism coupler and propagation loss of the film measured by scattering-detection method is about 2 dB/cm. Luminescence properties of europium ions doped films were measured and are discussed. 相似文献
145.
腺嘌呤、嘌呤和四并苯的表面增强拉曼光谱随温度的可逆变化 总被引:2,自引:0,他引:2
用硝酸腐蚀法处理得到了具有表面增强拉曼光谱 (SERS)活性的银表面。在表面温度于 - 1 90℃~30℃变化时 (上升和下降 ) ,分别测定了吸附在银表面上的腺嘌呤、嘌呤和四并苯的表面增强拉曼光谱 ,观察到一系列有关拉曼峰频率和强度的可逆变化。结果表明 ,温度降低 ,吸附分子SERS中受电磁增强机制作用的振动的拉曼位移发生蓝移 ,同时峰强度也有变化 ;而受化学增强机制作用的振动的拉曼位移则不受温度的影响。温度的变化导致分子平面可弯曲分子在金属表面的取向发生变化 ,如腺嘌呤和嘌呤在高温下取直立态 ,而平面的对称分子 (如四并苯 )在表面上的取向则不受温度的影响。 相似文献
146.
Orientational isomers of the octaethylporphyrin-dihexylbithiophene-fullerene derivative (OEP-DHBTh-C60) connected with the diacetylene linkage were synthesized. The electronic and electrochemical properties were studied, proving that the orientation of DHBTh affects not only the electronic structures of OEP-DHBTh-C60 but also their molecular motional behaviors evidently. 相似文献
147.
148.
A series of liquid single-crystal elastomers (LSCE) with different crosslinking densities were synthesized. The influence of the crosslinking density on the macroscopic properties (e.g. swelling, thermoelastic behavior and birefringence) and the phase behavior was studied. It is shown that densely crosslinked duromers are available which possess no clearing temperature and exhibit relatively high birefringence at high temperature. 相似文献
149.
Crystal structures of the known (NH4)3AlF6(I) and (NH4)3FeF6(III) and new (NH4)3TiOF5(II) elpasolites were refined by localizing anions (F−, O2−) in four acceptable positions of the cubic system Fm3m (Z=4) with a=8.9401(3), 9.1104(3), 9.110(1) Å, respectively. According to the refinement data and a rather large entropy change due to fluorine (oxygen) octahedra disordering in the above compounds and in (NH4)3WO3F3(IV) elpasolite, it was found that fluorine (oxygen) atoms are randomly distributed in two ways, in general 192l position or in mixed 24e + 96j one. Statistics in fluorine (oxygen) distribution is, probably, the result of domain structure of the crystals. 相似文献
150.
异喹啉吸附在银电极上的表面增强拉曼光谱研究陈建赵文涛,胡继明,徐知三,盛蓉生(中山大学测试中心,广州,510275)(武汉大学分析测试科学系,武汉,430072)关键词异喹啉,SERS,吸附,取向喹啉类和异喹啉类化合物在作为电解冶金、铜精炼和电镀的有... 相似文献