全文获取类型
收费全文 | 18507篇 |
免费 | 3658篇 |
国内免费 | 2747篇 |
专业分类
化学 | 7863篇 |
晶体学 | 182篇 |
力学 | 1495篇 |
综合类 | 149篇 |
数学 | 1001篇 |
物理学 | 9140篇 |
无线电 | 5082篇 |
出版年
2024年 | 44篇 |
2023年 | 222篇 |
2022年 | 542篇 |
2021年 | 644篇 |
2020年 | 687篇 |
2019年 | 618篇 |
2018年 | 554篇 |
2017年 | 747篇 |
2016年 | 849篇 |
2015年 | 751篇 |
2014年 | 1122篇 |
2013年 | 1505篇 |
2012年 | 1245篇 |
2011年 | 1297篇 |
2010年 | 1100篇 |
2009年 | 1177篇 |
2008年 | 1256篇 |
2007年 | 1175篇 |
2006年 | 1193篇 |
2005年 | 950篇 |
2004年 | 932篇 |
2003年 | 815篇 |
2002年 | 711篇 |
2001年 | 643篇 |
2000年 | 574篇 |
1999年 | 435篇 |
1998年 | 455篇 |
1997年 | 369篇 |
1996年 | 363篇 |
1995年 | 282篇 |
1994年 | 264篇 |
1993年 | 233篇 |
1992年 | 221篇 |
1991年 | 187篇 |
1990年 | 137篇 |
1989年 | 112篇 |
1988年 | 124篇 |
1987年 | 74篇 |
1986年 | 50篇 |
1985年 | 40篇 |
1984年 | 47篇 |
1983年 | 17篇 |
1982年 | 34篇 |
1981年 | 21篇 |
1980年 | 14篇 |
1979年 | 13篇 |
1978年 | 19篇 |
1977年 | 10篇 |
1975年 | 6篇 |
1973年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
221.
Jos Vargas Carlos Ramos Roberto D. Zysler Hctor Romero 《Physica B: Condensed Matter》2002,320(1-4):178-180
Chemically prepared (CoxNi1−x)1−yBy (x=0.5, 0.75, 1; y≈0.4) amorphous fine particles were characterized by X-ray diffraction, DTA and TGA, and in situ magnetic measurement as a function of annealing temperature in an inert atmosphere. Magnetic measurement performed in as-prepared and 150°C annealed samples shows an increase of the saturation magnetization and magnetic moment after thermal treatment. Room temperature magnetization increases by factors of 3.5, 1.8, and 1.5, for x=0.5, 0.75, and 1, respectively. These measurements may indicate a local re-ordering of the amorphous phase at temperatures much lower than the full crystallization temperature. 相似文献
222.
223.
Vlase T. Vlase G. Chiriac A. Doca N. 《Journal of Thermal Analysis and Calorimetry》2003,72(3):839-845
The thermal decomposition in non-isothermal conditions of formates, acetates, propionates and butyrates of Mn, Co, Zn, Cd,
Eu, Sm and Ni was studied. The observed compensation effect allows us to calculate the isokinetic temperature. A selective
activation mechanism was suggested. This leads to a good agreement between kinetic and spectroscopic data.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
224.
225.
Polycrystalline perovskite La0.67Ca0.33MnO3 was synthesized by a sol–gel method. Its adiabatic temperature change ΔTad induced by a magnetic field change was measured directly. At 268 K, near its Curie temperature TC, ΔTad of La0.67Ca0.33MnO3 induced by a magnetic field change of 2.02 T reaches 2.4 K. The latent heat Q and magnetic entropy change −ΔSM induced by a magnetic field change were calculated from the temperature dependence of ΔTad and zero-field heat capacity Cp. The maximum values of Q and −ΔSM in La0.67Ca0.33MnO3 induced by a magnetic field change of 2.02 T are 1.85 J g−1 and 6.9 J kg−1 K−1, respectively. The former is larger than the phase transition latent heat of heating or cooling, which is about 1.70 J g−1. 相似文献
226.
227.
A series of molecular dynamics simulations have been performed to study the supramolecular structure of self‐assembled complexes formed by N‐dodecyltrimethylammonium cations and the synthetic polypeptide poly(α,L ‐glutamate). The influence of the type of solvent has been investigated, considering explicit environments of chloroform, water, and methanol on a stoichiometric complex containing 15 residues. In chloroform, the complex stabilizes in a regular structure: the polypeptide adopts an α‐helix conformation that is regularly surrounded by surfactant molecules to form electrostatic interactions through a multiple interaction pattern. However, this structure destabilizes in methanol and water: (a) the α‐helix unfolds in the two solvents and (b) the electrostatic links between the surfactant molecules and the polyanion are disrupted in aqueous solution, although these interactions are still preserved in methanol. The role of the solvent environment in stabilizing or destabilizing the polypeptide secondary structure, the organization of the surfactant molecules, and predominantly the surfactant–polypeptide supramolecular organization is discussed in detail. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1122–1133, 2006 相似文献
228.
Degradation of 4-chlorophenol in aqueous solution by γ-radiation and ozone oxidation 总被引:5,自引:2,他引:3
HU Jun WANG Jianlong & CHEN Rong . Laboratory of Environmental Technology Institute of Nuclear Energy Technology Tsinghua University Beijing China . State Key Joint Laboratory of Environmental Simulation Pollution Control Tsinghua University Beijing China Correspondence should be addressed to Wang Jianlong 《中国科学B辑(英文版)》2006,(2)
The application of radiation technology in the en-vironmental protection was listed as one of the mostimportant research fields by the International AtomicEnergy Agency (IAEA) for the peaceful use of nuclearenergy. It has great research value and potential appli-cation. Because of their broad-spectrum antimicrobialproperties, Cholophenols (CPs) have been used aspreservative agents for wood, paints, vegetable fibersand leather and as disinfectants. In addition, they havebeen widely employed… 相似文献
229.
Josephson effects have been observed in bulk samples of Y-Ba-Cu-O. The magnitude of the zero-voltage current is found to change
systematically with externally applied small magnetic fields of a few mG. It is also found to vary when samples are irradiated
with microwaves. These observations suggest the presence of inter-grain Josephson junctions. 相似文献
230.
We have carried out some photon interaction measurements using 59.54 keV γ-rays from a 241Am source. These include γ attenuation studies as well as photoelectric absorption studies in various samples. The attenuation
studies have been made using leaf and wood samples, samples like sand, sugar etc., which contain particles of varying sizes
as well as pellets and aqueous solutions of rare earth compounds. In the case of the leaf and wood samples, we have used the
γ-ray attenuation technique for the determination of the water content in fresh and dried samples. The variation of the attenuation
coefficient with particle size has been investigated for sand and sugar samples. The attenuation studies as well as the photoelectric
studies in the case of rare earth elements have been carried out on samples containing such elements whose K-absorption edge
energies lie below and close to the γ-energy used. Suitable compounds of the rare earth elements have been chosen as mixture
absorbers in these investigations. A narrow beam good geometry set-up was used for the attenuation measurements. A well-shielded
scattering geometry was used for the photoelectric measurements. The mixture rule was invoked to extract the values of the
mass attenuation coefficients for the elements from those of the corresponding compounds. The results are consistent with
theoretical values derived from the XCOM package. 相似文献