全文获取类型
收费全文 | 993篇 |
免费 | 78篇 |
国内免费 | 75篇 |
专业分类
化学 | 452篇 |
晶体学 | 21篇 |
力学 | 6篇 |
综合类 | 5篇 |
数学 | 15篇 |
物理学 | 647篇 |
出版年
2023年 | 6篇 |
2022年 | 12篇 |
2021年 | 5篇 |
2020年 | 10篇 |
2019年 | 12篇 |
2018年 | 10篇 |
2017年 | 12篇 |
2016年 | 20篇 |
2015年 | 14篇 |
2014年 | 23篇 |
2013年 | 52篇 |
2012年 | 68篇 |
2011年 | 65篇 |
2010年 | 50篇 |
2009年 | 68篇 |
2008年 | 61篇 |
2007年 | 68篇 |
2006年 | 64篇 |
2005年 | 57篇 |
2004年 | 45篇 |
2003年 | 44篇 |
2002年 | 44篇 |
2001年 | 40篇 |
2000年 | 50篇 |
1999年 | 39篇 |
1998年 | 35篇 |
1997年 | 21篇 |
1996年 | 11篇 |
1995年 | 18篇 |
1994年 | 18篇 |
1993年 | 11篇 |
1992年 | 17篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1976年 | 4篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1970年 | 4篇 |
1969年 | 1篇 |
排序方式: 共有1146条查询结果,搜索用时 390 毫秒
71.
Magnetic susceptibility and heat capacity due to spin-state excitations in LaCoO3 were analyzed with an irregular solution model composed of Co3+ ions in the low-spin ground state and in the high-spin excited state. An energy-levels diagram proposed by Ropka and Radvanskii
[1] was used for the high-spin excited state. This analysis showed that the entropy of mixing is less than that of ideal solutions
and the enthalpy of mixing is negative, indicating that the high-spin Co ions are arranged as far apart as possible. 相似文献
72.
Anisotropy of magnetic susceptibility is used in the present study to reveal thedepositional fabric on the original (windblown) loess and secondary (redeposited) loess. The two kinds of sediments mentioned above can be distinguished in terms of their susceptibility anisotropy, e.g. anisotropy degree, magnetic foliation and lineation parameters. On this basis the magnetic fabric of the Pliocene red soil underlaying the loess is studied, and compared with the results of a typical residue-deposited red clay in South China. Considering its geological features, the red soil in Xifeng is regarded probably as aeolian in origin also. 相似文献
73.
Magnetic susceptibility studies of lead oxyhalide glasses containing high concentrations of transition metal oxides such as
MnO and Fe2O3 have been performed. While they exhibit predominantly antiferromagnetic interactions, the low temperature (<100K) region
is dominated by paramagnetic contributions. The behaviour in these glasses is found to be similar to that of covalent oxide
glasses and is different from that of purely ionic sulphate glasses.
Communication No. 324 from the Solid State and Structural Chemistry Unit. 相似文献
74.
Kaixuan Chen Zhenhua Ning Hengyi Xu Zhi Qi Guo Lu Furen Wang Daole Yin 《中国科学G辑(英文版)》2005,48(1):14-25
The amplitude-dependent ac susceptibility of high-temperature superconductors is shown to obey some empirical scaling relations.
We try to analyze this behavior by extending a dc nonlinear response function of mixed state to the ac cases. The derived
equations for critical current and ac susceptibility ξ(T) agree with the scaling relations of experimental data. 相似文献
75.
J.R.L. de Almeida 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(2):269-273
The linear and non-linear susceptibilities of the two sub-lattices Random Energy Model (REM) allowing antiferromagnetic order
is studied as a function of the external field (h) and temperature (T). Due to the competition between external field and the internal exchange field acting on the spins there is a drastic change
of the system's behavior as the parameters (h,T) are varied. The behavior of the susceptibilities in low and high fields is very different in that the latter may grow as
the temperature decreases. Moreover, the critical region undergoes a substantial enlargement as the external field increases.
Received: 29 May 1998 相似文献
76.
Masuda Y. Seto Y. Wang X. Tuchiya Y. 《Journal of Thermal Analysis and Calorimetry》2001,64(3):1045-1051
The thermal dehydration of La[Co(CN)6]⋅5H2O proceeded through at least three stages from the temperature range of30~230°C, and an abrupt mass loss occurred around 350°C
and the perovskite type oxide,LaCoO3 was obtained at 1000°C.
After dehydration, the color of the anhydride changed from white to pale blue around 230°C and furthermore, the color changed
to blue around 290°C. These color changes were discussed on the basis of the changes of coordination structures around Co
ions.
In La[Co(CN)6]⋅5H2O, Co3+ ions lie at the center of the Oh crystal field consisted of six CN– ions. However, in the pale blue specimen, Co3+ ions were situated in the center of D4h crystal field which was distorted the Oh one by lengthening of the trans CN– ions along z-axis. In the blue specimen, Co3+ ions were reduced to Co2+ ions which were situated in the Td crystal field formed by four CN–ions as [Co(CN)4]2–.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
77.
Effects of chemical substitution in CeRu2Si2, a well-studied heavy fermion system and YbPd2Si2 have been investigated through magnetic susceptibility and x-ray diffraction in the systems CeRu
x
Si2, CeRu2−x
Os
x
Si2, CeRu2Si2−x
Ge
x
and YbPd2Si2−x
Ge
x
. Replacing silicon by germanium generates normal chemical pressure effect, namely, Ce and Yb atoms in CeRu2Si2 and YbPd2Si2 became more and less magnetic respectively. With increasing Ge concentration, CeRu2Si2−x
Ge
x
exhibits larger susceptibility at low temperature, goes to an antiferromagnetic state and finally becomes ferromagnetic.
In YbPd2Si2−x
Ge
x
, increasing Ge concentration drives Yb atoms to more divalent state. Electronic effects are more pronounced in CeRu2−x
Os
x
Si2 though CeRu2Si2 and CeOs2Si2 have very nearly the same lattice parameters. It is conjectured that CeRu2Si2−x
Ge
x
may be the first Ce-based heavy fermion having a magnetic ground state.
The authors felicitate Prof. D S Kothari on his eightieth birthday and dedicate this paper to him on this occasion. 相似文献
78.
Preparation of chlorogenic acid surface-imprinted magnetic nanoparticles and their usage in separation of Traditional Chinese Medicine 总被引:1,自引:0,他引:1
The chlorogenic acid (CGA) surface-imprinted magnetic polymer nanoparticles have been prepared via water-in-oil-in-water multiple emulsions suspension polymerization. This kind of molecularly imprinted polymer nanoparticles (MIPs) had the core-shell structure with the size of about 50 nm. Magnetic susceptibility was given by the successful encapsulation of Fe3O4 nanoparticles with a high encapsulation efficiency of 19.3 wt%. MIPs showed an excellent recognition and selection properties for the imprinted molecule CGA. The recognition capacity of MIPs was near three times than that of non-imprinted polymer nanoparticles (NIPs). Compared with the competitive molecule caffeic acid (CFA), the selectivity of MIPs for CGA was 6.06 times as high as that of NIPs. MIPs could be reused and regenerated, and their rebinding amount in the fifth use was up to 78.85% of that in the first use. The MIPs prepared were successfully applied to the separation of CGA from the extract of Traditional Chinese Medicine Honeysuckle. 相似文献
79.
Physical properties of NdPd2Ge2 and NdAg2Ge2, crystallizing with the tetragonal ThCr2Si2-type crystal structure, were investigated by means of magnetic, calorimetric, electrical transport as well as by neutron diffraction measurements. The specific heat studies and neutron diffraction measurements were performed down to 0.30 K and 0.47 K, respectively. Both compounds exhibit antiferromagnetic ordering below TN equal to 1.5 K for NdPd2Ge2 and 1.8 K for NdAg2Ge2. Neutron diffraction data for the latter germanide indicate antiferromagnetic collinear structure described by the propagation vector k=(0.5, 0, 0.5). The Nd magnetic moments equal to 2.24(5) μB at 0.47 K are aligned along the a-axis and have the +− sequence within the crystal unit cell. For NdPd2Ge2 only very small Bragg peaks of magnetic origin were observed in the neutron diffraction patterns measured below TN, thus hampering determination of the magnetic structure. Both compounds exhibit metallic-like electrical conduction. From the specific heat data the crystal electric field (CEF) levels schemes were determined. Difference between the overall CEF splitting in the two compounds is correlated with their structural parameters. 相似文献
80.
The crystal structure of the Zr1−xYxNiSn half-Heusler solid solutions is synthesized and their crystal structure is determined. Electrical resistivity and thermoelectric Seebeck coefficient are measured in the 80-380 K temperature range, whereas magnetic susceptibility is measured at 290 K. It is established that substitution of Zr host atoms by Y in the ZrNiSn intermetallic semiconductor is equivalent to doping by acceptor impurities. Self-consistent ab initio calculations, based on the full potential local orbital (FPLO) minimum basis method, are performed to investigate the electronic and thermoelectric properties of these alloys. Spin polarized within the framework of the coherent potential approximation (CPA) are included. 相似文献