全文获取类型
收费全文 | 332篇 |
免费 | 14篇 |
国内免费 | 22篇 |
专业分类
化学 | 255篇 |
晶体学 | 6篇 |
力学 | 5篇 |
物理学 | 102篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 10篇 |
2019年 | 9篇 |
2018年 | 4篇 |
2017年 | 9篇 |
2016年 | 13篇 |
2015年 | 9篇 |
2014年 | 9篇 |
2013年 | 33篇 |
2012年 | 18篇 |
2011年 | 25篇 |
2010年 | 18篇 |
2009年 | 14篇 |
2008年 | 21篇 |
2007年 | 10篇 |
2006年 | 20篇 |
2005年 | 15篇 |
2004年 | 22篇 |
2003年 | 6篇 |
2002年 | 14篇 |
2001年 | 8篇 |
2000年 | 8篇 |
1999年 | 8篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1996年 | 5篇 |
1995年 | 6篇 |
1994年 | 2篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
排序方式: 共有368条查询结果,搜索用时 31 毫秒
1.
The effect of Re addition on the microstructure and hardening behaviour of the dual two-phase Ni3Al (L12) and Ni3V (D022) intermetallic alloy was investigated by scanning electron microscopy, transmission electron microscopy and Vickers hardness test. The two-phase eutectoid microstructure accompanying the Re-rich precipitates were observed in the channel region of the alloys in which Re substituted for Ni but not in those in which Re substituted for Al and V. The concomitant addition of Nb (or Ta) with Re more stabilized the two-phase eutectoid microstructure and consequently more induced the fine precipitates in the channel region. The annealing at temperatures below the eutectoid temperature was necessary to induce the fine precipitates in the channel region and thereby result in the precipitation hardening. The fine precipitation in the channel region and related hardening was attributed to the alloying feature so that Re is soluble in the A1 (fcc) phase at high temperatures and becomes less soluble in the two intermetallic phases decomposed from the A1 phase at low temperatures. 相似文献
2.
Keka Chakraborty S K Paranjpe V Siruguri O D Jayakumar S K Kulshreshtha 《Pramana》1997,48(6):1115-1122
Neutron diffraction and M?ssbauer measurements have been carried out on the cubic Laves phase intermetallic TbMnFe. The magnetic
moment on the transition metal atom is found to be low, 0.2μ
B, at room temperature. This moment is temperature independent down to 10 K. Magnetic moment on the rare earth atom varies
from 2.5μ
B at 296 K to 7.27μ
B at 10 K. M?ssbauer spectra recorded at 298 K and 78 K have magnetic character but there is a large distribution of hyperfine
field values. Both these features arise due to magnetic frustration created in the sample due to the competing ferro and antiferromagnetic
interactions between the transition metal atoms. 相似文献
3.
4.
Svilen Bobev Paul H. Tobash Joe D. Thompson John L. Sarrao 《Journal of solid state chemistry》2005,178(6):2091-2103
A number of rare-earth alumo-silicides (R-Al-Si) have been synthesized from the corresponding elements by high-temperature reactions, carried out in excess of aluminum to serve as a flux. Under these experimental conditions, large single crystals of all R-Al-Si ternary phases were readily produced. The crystal structures these ternaries adopt were studied by means of powder and single-crystal X-ray diffraction and were classified as follows: (1) the early rare-earths (R=La, Ce, Pr, Nd, Sm, Gd) yield RAlxSi2−x, x∼1, non-stoichiometric ternary derivatives of the body-centered α-ThSi2-type; (2) the late rare-earths (R=Tb, Dy, Ho, Er, Tm) form stoichiometric R2Al3Si2 compounds that crystallize in the C-centered monoclinic Y2Al3Si2-type; (3) the divalent Eu and Yb produce EuAl2Si2 and YbAl2Si2 with the trigonal CaAl2Si2-type, whereas the last lanthanide element, Lu, forms LuAlSi with C-centered orthorhombic YAlGe-type. These structural trends are reviewed, and the evolution of the basic physical properties such as magnetism, heat capacity and electrical resistivity when moving across the series is described in detail. 相似文献
5.
J.S. Yadav B.V. Subba Reddy K.V. Raghavendra Rao G.G.K.S. Narayana Kumar 《Tetrahedron letters》2007,48(31):5573-5576
Indoles undergo smooth alkylation with propargylic alcohols in the presence of 10 mol % of scandium triflate under mild conditions to produce 3-propargylated indoles in excellent yields with high selectivity. 相似文献
6.
The effects of M3O3 (M = Al, Sc etc.) in Cu-ZnO-M2O3 catalysts on methanol synthesis at low pressure were studied with ESR, XPS and TPR spectroscopy. The results of ESR showed that the generation of monovalent cationic defects was because the valence state and electronic charge on the ZnO lattice lost their balance as M3+ doped into ZnO. The induced effect by Sc3+ is stronger than that by Al3+. The results of XPS and TPR indicated that the amount and stabilization of Cu+ on the surface of reduced copper-based catalyst and its catalytic activity were affected by the monovalent cationic defects on the surface of ZnO. 相似文献
7.
钪—镧—对氟偶氮氯膦体系共显色效应的研究及应用 总被引:3,自引:0,他引:3
本文研究了钪-镧-对氟偶氮氯膦体系共显色效应的光度特性及测定钪的最佳条件,建立了光度法测定痕量钪的新方法。该法的表观摩尔吸光系数为8.57×10^4L·mol^-1·cm^-1,Sc(Ⅲ)浓度在0.0-5.0μg/25ml范围符合比尔定律。将本法用于镁基,铁基合成试样中痕量钪的测定,结果满意。 相似文献
8.
A novel quaternary scandium borocarbosilicide Sc3.67−xB41.4−y−zC0.67+zSi0.33−w was found. Single crystallites were obtained as an intergrowth phase in the float-zoned single crystal of Sc0.83−xB10.0−yC0.17+ySi0.083−z that has a face-centered cubic crystal structure. Single crystal structure analysis revealed that the compound has a hexagonal structure with lattice constants a = b = 1.43055(8) nm and c = 2.37477(13) nm and space group (No. 187). The crystal composition calculated from the structure analysis for the crystal with x = 0.52, y = 1.42, z = 1.17, and w = 0.02 was ScB12.3C0.58Si0.10 and that agreed rather well with the composition of ScB11.5C0.61Si0.04 measured by EPMA. In the crystal structure that is a new structure type of boron-rich borides, there are 79 structurally independent atomic sites, 69 boron and/or carbon sites, two silicon sites and eight scandium sites. Boron and carbon form seven structurally independent B12 icosahedra, one B9 polyhedron, one B10 polyhedron, one irregularly shaped B16 polyhedron in which only 10.7 boron atoms are available because of partial occupancies and 10 bridging sites. All polyhedron units and bridging site atoms interconnect each other forming a three-dimensional boron framework structure. Sc atoms reside in the open spaces in the boron framework structure. 相似文献
9.
钪—铋—三溴偶氮胂混合多核络合物显色反应及其在钪光度分析中应用研究 总被引:3,自引:0,他引:3
本文研究了钪-铋-三溴偶氮胂络合物的共显色反应。实验表明,共显色反应是由于形成混合多核络合物所致。钪络合物最大吸收峰在635nm,表观摩尔吸光系数为7.1×10~4L·mol~(-1)·cm~(-1)。钪在0~5μg/25ml遵守比尔定律。 相似文献
10.
Summary The condensation of 2,6-diacetylpyridine andm-phenylenediamine in the presence of scandium(III) perchlorate as a template agent affords a new 20-membered macrocyclic complex of formula ScL(ClO4)3·4H2O, whereL is Me4
bzo
2
pyo
2[20]octaene-N6.
Scandium(III) als Matrix für die Synthese eines makrocyclischen Hexaazaliganden
Zusammenfassung Die Kondensation von 2,6-Diacetylpyridin undm-Phenylendiamin in Gegenwart von Scandium(III)perchlorat als Matrix liefert einen neuen makrocyclischen Komplex der Zusammensetzung ScL(ClO4)3·4H2O (L=Me4 bzo 2 pyo 2[20]octaen-N6).相似文献