全文获取类型
收费全文 | 870篇 |
免费 | 12篇 |
国内免费 | 48篇 |
专业分类
化学 | 307篇 |
晶体学 | 4篇 |
力学 | 5篇 |
综合类 | 7篇 |
数学 | 56篇 |
物理学 | 551篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 15篇 |
2021年 | 10篇 |
2020年 | 5篇 |
2019年 | 11篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 14篇 |
2015年 | 13篇 |
2014年 | 21篇 |
2013年 | 132篇 |
2012年 | 67篇 |
2011年 | 45篇 |
2010年 | 32篇 |
2009年 | 36篇 |
2008年 | 35篇 |
2007年 | 51篇 |
2006年 | 36篇 |
2005年 | 23篇 |
2004年 | 27篇 |
2003年 | 24篇 |
2002年 | 29篇 |
2001年 | 32篇 |
2000年 | 19篇 |
1999年 | 25篇 |
1998年 | 38篇 |
1997年 | 21篇 |
1996年 | 22篇 |
1995年 | 18篇 |
1994年 | 32篇 |
1993年 | 18篇 |
1992年 | 9篇 |
1991年 | 17篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 1篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1977年 | 3篇 |
排序方式: 共有930条查询结果,搜索用时 0 毫秒
121.
Abbas Heydari 《Linear algebra and its applications》2008,429(7):1744-1757
Let H be a simple graph with n vertices and G be a sequence of n rooted graphs G1,G2,…,Gn. Godsil and McKay [C.D. Godsil, B.D. McKay, A new graph product and its spectrum, Bull. Austral. Math. Soc. 18 (1978) 21-28] defined the rooted product H(G), of H by G by identifying the root vertex of Gi with the ith vertex of H, and determined the characteristic polynomial of H(G). In this paper we prove a general result on the determinants of some special matrices and, as a corollary, determine the characteristic polynomials of adjacency and Laplacian matrices of H(G).Rojo and Soto [O. Rojo, R. Soto, The spectra of the adjacency matrix and Laplacian matrix for some balanced trees, Linear Algebra Appl. 403 (2005) 97-117] computed the characteristic polynomials and the spectrum of adjacency and Laplacian matrices of a class of balanced trees. As an application of our results, we obtain their conclusions by a simple method. 相似文献
122.
Preparation and Characterization of Iodoplatinates MexNH4–xPtI4 (x = 2–4), Mixed Valence Octaiododiplatinates(II,IV) with Pt2I8 Groups Iodoplatinates APtI4 (A = MexNH4–x with x = 2–4) have been prepared by partial oxidation of the correspondent hexaiododiplatinates(II) A2Pt2I6 with I2 in methanolic solutions. X-ray structure analyses of the bronze-coloured needle-shaped crystals of the compounds showed rows of dinuclear anions Pt2I82?, built up by edgesharing planar PtI4 groups with PtII und octahedral PtI6 groups with PtIV. The different space requirement of the cations leads to the formation of three different structures. Within the anion stacks weak intermolecular PtIV? I …? PtII interactions are detectable by Raman spectroscopy. 相似文献
123.
使用四甲氧基硅烷(TMOS)和二甲基二甲氧基硅烷(DiMe-DMOS)为共先驱体,采用溶胶-凝胶的有机掺杂,制备对pH具有宽程响应的敏感膜。详细考察了包埋溴酚蓝和溴酚绿的敏感膜对pH的响应值、响应时间、泄漏和可逆性等响应性能指标,并进行了溴酚蓝和溴酚绿在水相与膜内吸收光谱的研究。 相似文献
124.
对查尔酮类共轭体系的电子光谱,CNDO/2计算及线性关系文献中已作了全面报道。本文用林惠心等在徐光宪改进的HMO法基础上提出的改进HMO法(即MHMO法),对查尔酮类共轭体系进行了计算,结果λ_计和λ_实基本一致,线性关系良好。 相似文献
125.
Bergman空间上Toeplitz算子的局部化 总被引:2,自引:0,他引:2
Bergman空间上Toeplitz算子的局部化@孙善利@卢玉峰... 相似文献
126.
Abstract The Raman spectra of a crystalline powder of InCl3 and of a de-ionized water solution show the presence of four bands at 300.0, 289.2, 115.6 and 87.1 cm?1, thus suggesting that InCl3 is not a perfectly planar molecule. 相似文献
127.
Abstract The blue-green (B2? X2?) and orange (A2? –X2?) systems of yttrium oxide have been shock excited at temperatures of about 4000°K and photographed at high dispersion (~ 1.2Å/mm) in the first order of a 21 ft. grating spectrograph. The high dispersion shock excited spectra were recorded using multiple exposures and latensification of extremely high speed film. Over 50 new bands have been observed and assigned to specific vibrational transitions for the systems. New molecular constants have been derived from the A, B and X states. Provisional calculations have been made of Franck-Condon factors and r-centroids for the systems appropriate to new constants. 相似文献
128.
F. G. Baglin 《光谱学快报》2013,46(6):149-155
Preliminary vibrational analysis of this bicyclic moiety clearly shows the presence of Fermi Resonance phenomena. The alternative to this assignment is shown to be contradictory to both electron diffraction results and to the vibrational data, presented in this paper. Of primary interest is the implications that these spectral results could have for further studies involving classical and non-classical carbonium ion structures. 相似文献
129.
Feng Liu Weiping Zhang Shuiyang He Liujie Wang Xiangrong Liu 《Journal of chemical crystallography》2008,38(10):755-760
Abstract A novel binuclear Smarium (III) complex with N-(2-propionic acid)-salicyloyl hydrazone (C10H10N2O4, H3L) was prepared and characterized. The crystal structure of [Sm2(H2L)2(HL)2(H2O)4] (1) was determined by X-ray single crystal diffractometry. 1 crystallizes in the monoclinic systerm, space group P2(1)/c,
with a = 0.10229(2), c = 31.549(7), b = 0.70599(15) nm, and Z = 4. In the structure, Sm(III) is nine-coordinated by carboxyl O and acyl O atoms and imido N atoms
of two ligands (H2L and HL forms) and O atoms from two water molecules. H2L and HL act as tridentate ligands which form two stable five-numbered chelating rings sharing one edge in the keto form for
each ligand, and the carboxyl groups of two ligands were coordinated via bidentated bridging form. The coordination polyhedron
around Sm (III) was described as a monocapped square antiprism. The inter- and intramolecular hydrogen bonds resulted in a
three-dimensional network and provided extra stability for the structure. The complex was researched the interaction with
calf thymus DNA by electronic absorption titration and emission titration. The results show that the complex is bound to calf
thymus DNA mainly by intercalation .The complex also shows good fluorescence property.
Index Abstract The title compound, [Sm2(H2L)2(HL)2(H2O)4] was synthesized by the treatment of N-(2-propionic acid)-salicyloyl hydrazone (C10H10N2O4, H3L) and Sm(NO3) · 4H2O and its crystal structure determined. Single crystal X-ray diffraction analysis reveals that Sm (III) is nine-coordinated
by carboxyl O and acyl O atoms and imido N atoms of two ligands (H2L and HL forms) and O atoms from two water molecules. The carboxyl groups of two ligands were coordinated via bidentated bridging
form. The coordination polyhedron around Sm (III) was described as a monocapped square antiprism. The inter- and intramolecular
hydrogen bonds resulted in a three-dimensional network and provided extra stability for the structure.
相似文献
130.
闫清华 《分析测试技术与仪器》2018,(3):179-182
采用超高效液相色谱-串联质谱法(UPLC-MS/MS)测定水产品中孔雀石绿的残留量,以GB/T 19857-2005检测方法为基础,将前处理步骤进行优化.称取5 g样品,加入质量浓度为100μg/L的内标标准溶液100μL,混匀,加入20 m L乙腈、5 g酸性氧化铝,震荡、离心,取4 m L溶液氮气吹干,用流动相定容至1 m L,过0.22μm滤膜,上机测试.按照标准方法测定标准曲线相关系数r:孔雀石绿为0.999,隐色孔雀石绿为0.999.孔雀石绿的回收率分别为71.7%、95.2%和89.9%,精密度分别为4.47%、4.26%和8.57%.隐色孔雀石绿的回收率分别为93.3%、98.8%和89.7%,精密度分别为8.73%、6.87%和9.71%.试验结果满足相关标准和体系文件的要求. 相似文献