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 29 毫秒
101.
Abdessalem Badri María Luisa López Alain Wattiaux 《Journal of solid state chemistry》2011,184(4):937-944
Single crystals of a new phosphate KCuFe(PO4)2 have been prepared by the flux method and its structural and physical properties have been investigated. This compound crystallizes in the monoclinic system with the space group P21/n and its parameters are: a=7.958(3) Å, b=9.931(2) Å, c=9.039(2) Å, β=115.59(3)° and Z=4. Its structure consists of FeO6 octahedra sharing corners with Cu2O8 units of edge-sharing CuO5 polyhedra to form undulating chains extending infinitely along the b-axis. These chains are connected by the phosphate tetrahedra giving rise to a 3D framework with six-sided tunnels parallel to the [101] direction, where the K+ ions are located. The Mössbauer spectroscopy results confirm the exclusive presence of octahedral Fe3+ ions. The magnetic measurements show the compound to be antiferromagnetic with Cm=5.71 emu K/mol and θ=−156.5 K. The derived experimental effective moment μex=6.76μB is somewhat higher than the theoretical one of μth=6.16μB, calculated taking only into account the spin contribution for Fe3+ and Cu2+ cations. Electrical measurements allow us to obtain the activation energy (1.22 eV) and the conductivity measurements suggest that the charge carriers through the structure are the potassium cations. 相似文献
102.
H. Tsuruda M. MitoH. Deguchi S. TakagiA.A. Leitch K. LekinS.M. Winter R.T. Oakley 《Polyhedron》2011,30(18):2997-3000
The hydrostatic pressure response of TC of the bisdiselenazolyl radical ferromagnet 1 up to 5 GPa was investigated by AC magnetic susceptibility measurements using a SQUID magnetometer and a miniature diamond anvil cell. It was found that the ambient pressure value of TC = 17 K could be raised to 21 K at a pressure of 0.9 GPa. The experimental technique is described in detail and the pressure response is compared to that observed in related systems. 相似文献
103.
104.
M.L. Palma 《Molecular physics》2013,111(18):2163-2172
Following our previous study on spin–rotation and shielding constants of the SF6 molecule, the rotational g factor and the magnetic susceptibility are calculated here, using ab initio methods to evaluate the electronic contribution to the nuclear hyperfine constants, and compared with experimental results. It is shown, for the first time, that the electronic component of the rotational g factor is proportional to a constant, which is given by a sum over electronic states. We also evaluate for the SF6 molecule the indirect, or electron-coupled spin–spin interaction, theoretically described by Ramsey, and show that it gives non-negligible corrections to direct coupling constants d 1 and d 2. The contributions of the terms included in this interaction (DSO, PSO, SD and FC) are also analysed. 相似文献
105.
高Verdet常数的Tb3+铝硼硅酸盐玻璃 总被引:1,自引:1,他引:0
本文研究了一种铝硼硅酸盐基质玻璃,通过加大单位体积的稀土离子浓度,并选择P值大的顺磁性Tb3+作为弗尔德常数贡献的主要离子,经反复试验研究,制定合理的熔制工艺,得到性能稳定的透明顺磁旋光玻璃。弗尔德常数V=-0.375/Oe·cm。是目前世界上弗尔德常数较高的磁旋光玻璃。 相似文献
106.
Akito Kobayashi Yoshiaki
no Tamifusa Matsuura Yoshihiro Kuroda 《Physica C: Superconductivity and its Applications》1998,300(3-4):287-300
Dynamical spin susceptibility χs(q,ω) of the d–p model in the over doping region is investigated by using the auxiliary boson technique. It includes higher order terms of the 1/N-expansion within the random phase approximation (RPA) of the local vertex, where frequency dependence of the quasi-particle interaction is taken into account. The incommensurate spin fluctuation is obtained due to the nesting effect in the low energy region (ωω*), whereas the commensurate one in the high energy region (ωω*), the characteristic energy ω* is estimated to be about 30 meV. Both of the spin–lattice relaxation rate 1/T1 and the spin–spin relaxation rate 1/Tg monotonically increase as T decreases, while the spin Knight shift K is almost independent of T. 相似文献
107.
108.
B. Canals D.A. Garanin 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(4):439-447
Thermodynamic quantities and correlation functions (CFs) of the classical antiferromagnet on the checkerboard lattice are
studied for the exactly solvable infinite-component spin-vector model, D↦∞. In contrast to conventional two-dimensional magnets with continuous symmetry showing extended short-range order at distances
smaller than the correlation length, r
ξ
c∝ exp(T
*/T), correlations in the checkerboard-lattice model decay already at the scale of the lattice spacing due to the strong degeneracy
of the ground state characterized by a macroscopic number of strongly fluctuating local degrees of freedom. At low temperatures,
spin CFs decay as <
>∝ 1/r
2 in the range a
0≪r≪ξ
c∝T
-1/2, where a0 is the lattice spacing. Analytical results for the principal thermodynamic quantities in our model are very similar with
MC simulations, exact and analytical results for the classical Heisenberg model (D = 3) on the pyrochlore lattice. This shows that the ground state of the infinite-component spin vector model on the checkerboard
lattice is a classical spin liquid.
Received 16 November 2001 and Received in final form 12 February 2002 相似文献
109.
S. M. Cotes A. F. Cabrera L. C. Damonte R. C. Mercader J. Desimoni 《Physica B: Condensed Matter》2002,320(1-4):274-277
BCC, FCC and HCP phases in Fe–13.7 wt% Mn alloys were studied by Mössbauer spectroscopy and X-ray diffraction, after ball milling. The relative amounts of the HCP and FCC phases increase with milling times up to 9 h and decline afterwards. Preliminary AC susceptibility measurements show that the blocking temperatures change for different milling times. 相似文献
110.
Phosphorus spin-lattice relaxation was studied in aluminophosphate molecular sieves containing various concentrations of either framework or non-framework cobalt. The behaviour of nuclear magnetisation in the presence of these paramagnetic centres was described successfully in the limit of no spin-diffusion. The diffusionless regime was strongly indicated with non-exponential magnetisation recovery and was therefore easy to recognise. According to the model, spin-lattice relaxation rates depend on the square of cobalt concentration. Measured relaxation rates agreed well with calculations if effective cobalt concentration was considered rather than the average one. The latter was obtained by bulk elemental analysis, while the former was extracted from cobalt concentration depth-profiles measured with Auger electron spectroscopy. These measurements indicated that in impregnated samples containing non-framework cobalt there could be much more cobalt near the crystal surface than within the crystal. Because high cobalt concentration can lead to an invisible phosphorus, only nuclei deep within the crystal contribute to the NMR signal. In such a case, the effective concentration is simply the concentration of cobalt far from the crystal surface. In our case, two impregnated samples with different bulk cobalt concentrations exhibited equal relaxation rates. Previously, such a case was misinterpreted as a case, in which nuclear spin-lattice relaxation was independent of cobalt concentration. AES measurements, however, revealed, that although average concentrations of the two samples were different by a factor of two, their effective concentrations were equal and thus in complete agreement with observed relaxation rates. 相似文献