全文获取类型
收费全文 | 9827篇 |
免费 | 2377篇 |
国内免费 | 1138篇 |
专业分类
化学 | 5943篇 |
晶体学 | 194篇 |
力学 | 340篇 |
综合类 | 67篇 |
数学 | 222篇 |
物理学 | 6576篇 |
出版年
2024年 | 14篇 |
2023年 | 103篇 |
2022年 | 247篇 |
2021年 | 327篇 |
2020年 | 468篇 |
2019年 | 431篇 |
2018年 | 411篇 |
2017年 | 437篇 |
2016年 | 517篇 |
2015年 | 431篇 |
2014年 | 528篇 |
2013年 | 852篇 |
2012年 | 763篇 |
2011年 | 791篇 |
2010年 | 667篇 |
2009年 | 653篇 |
2008年 | 618篇 |
2007年 | 608篇 |
2006年 | 586篇 |
2005年 | 508篇 |
2004年 | 479篇 |
2003年 | 413篇 |
2002年 | 471篇 |
2001年 | 342篇 |
2000年 | 309篇 |
1999年 | 221篇 |
1998年 | 189篇 |
1997年 | 132篇 |
1996年 | 124篇 |
1995年 | 112篇 |
1994年 | 94篇 |
1993年 | 60篇 |
1992年 | 71篇 |
1991年 | 47篇 |
1990年 | 40篇 |
1989年 | 35篇 |
1988年 | 35篇 |
1987年 | 21篇 |
1986年 | 28篇 |
1985年 | 33篇 |
1984年 | 27篇 |
1983年 | 13篇 |
1982年 | 22篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1978年 | 14篇 |
1976年 | 7篇 |
1973年 | 5篇 |
1970年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
41.
42.
A simple model has been developed to describe the Zeeman patterns of far-infrared laser magnetic resonance spectra of the monobromomethyl radical CH2Br observed at 447.3 and 671.1μm. A satisfactory agreement between the experimental spectra of the radical and their simulation with this simple model has been achieved. This approach can be used to gain further information about the structure and the spectrum of this interesting radical. 相似文献
44.
Based on the effective-field theory with self-spin correlations and the differential operator technique,physical properties of the spin-2 system with biaxial crystal field on the simple cubic, body-centered cubic, as well as faced-centered lattice have been studied. The influences of the external longitudinal magnetic field on the magnetization,internal energy, specific heat, and susceptibility have been discussed in detail. The phenomenon that the magnetization in the ground state shows quantum effects produced by the biaxial transverse crystal field has been found. 相似文献
45.
Longlan Cui Hong Xu Ping He Keiko Sumitomo Yoshinori Yamaguchi Hongchen Gu 《Journal of polymer science. Part A, Polymer chemistry》2007,45(22):5285-5295
A hybrid emulsion polymerization was formulated for synthesizing Fe3O4/polystyrene composite latex. This system, containing binary droplets that are magnetic (Mag)‐droplets with a diameter of 100–200 nm and styrene (St)‐droplets with a diameter of 3–4 μm, was obtained by mixing Mag‐miniemulsion and St‐macroemulsion. With extremely low surfactants concentration (?critical micelle concentration, CMC), the nucleated loci are selectively controlled in the Mag‐droplets, as the result of smaller droplet size and larger surface ratio. Both water‐soluble potassium persulfate (KPS) and oil‐soluble 2,2′‐azobis(2‐isobutyronitrile) was adopted to initiate the polymerization. In the presence of KPS, magnetic polystyrene latices with particles size of 60–200 nm, narrow size distribution, and high magnetite content (86 wt % measured by TGA) were attained successfully. The synthesized magnetic Fe3O4/polystyrene latices assembled into well‐ordered hexagonal structure in the surface of a carbon supported copper grid. The influence of various parameters on various aspects of the as‐synthesized Fe3O4/polystyrene was investigated in detail: type of initiator on composite morphology, feed ratio of Mag‐miniemulsion and St‐macroemulsion on magnetite content, and hydrophobic agent or amount of surfactant on size and size distribution. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5285–5295, 2007 相似文献
46.
Richard Becker Mladen Prester Ping Hui Lin Mats Johnsson Ivica Zivkovic 《Journal of solid state chemistry》2007,180(3):1051-1059
Two new isostructural cobalt selenite halides Co5(SeO3)4Cl2 and Co5(SeO3)4Br2 have been synthesized. They crystallize in the triclinic system space group P−1 with the following lattice parameters for Co5(SeO3)4Cl2: a=6.4935(8) Å, b=7.7288(8) Å, c=7.7443(10) Å, α=66.051(11)°, β=73.610(11)°, γ=81.268(9)°, and Z=1. The crystal structures were solved from single-crystal X-ray data, R1=3.73 and 4.03 for Co5(SeO3)4Cl2 and Co5(SeO3)4Br2, respectively. The new compounds are isostructural to Ni5(SeO3)4Br2.Magnetic susceptibility measurements on oriented single-crystalline samples show anisotropic response in a broad temperature range. The anisotropic susceptibility is quantitatively interpreted within the zero-field splitting schemes for Co2+ and Ni2+ ions. Sharp low-temperature susceptibility features, at TN=18 and 20 K for Co5(SeO3)4Cl2 and Co5(SeO3)4Br2, respectively, are ascribed to antiferromagnetic ordering in a minority magnetic subsystem. In isostructural Ni5(SeO3)4Br2 magnetically ordered subsystem represents a majority fraction (TN=46 K). Nevertheless, anisotropic susceptibility of Ni5(SeO3)4Br2 is dominated at low temperatures by a minority fraction, subject to single-ion anisotropy effects and increasing population of Sz=0 (singlet) ground state of octahedrally coordinated Ni2+. 相似文献
47.
48.
D.A. Garanin E.M. Chudnovsky 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(1):3-7
We compute the width and shape of the EPR and tunneling resonances due to dislocations in Mn12 acetate crystals. Uncorrelated dislocations produce the Gaussian shape of resonances while dislocations bound in pairs produce
the Lorentzian shape. We stress that the uniaxial spin Hamiltonian together with crystal defects can explain the totality
of experimental data on Mn12.
Received 2 August 2001 / Received in final form 15 March 2002 Published online 17 September 2002 相似文献
49.
The peak effect (PE) in the critical current density in both low and high temperature superconductors has been the subject
of a large amount of experimental and theoretical work in the last few/several years. In the case of YBCO, crucial discussions
describing a dynamic or a static picture are not settled. In that region of field and temperature the mobility of the vortex
lattice (VL) is found to be dependent on the dynamical history. Recently we reported evidence that the VL reorganizes and
accesses to robust VL configurations (VLCs) with different effective pinning potential wells arising in response to different
system histories. One of the keys to understand the nature of the PE is to investigate the VL behavior in the vicinity of
the various VLCs in the region of the PE. The stability of these VLCs was investigated and it was found that they have distinct
characteristic relaxation times, which may be related to elastic or plastic creep processes. In this paper we review some
of these results and propose a scenario to describe the PE in YBCO crystals. 相似文献
50.
Arup Baksi Bidyut Kumar Roy Rasajit Kumar Bera 《Mathematical and Computer Modelling》2006,44(11-12):1069-1079
The fundamental equations of the problems of generalized thermoelasticity with one relaxation parameter including heat sources in infinite rotating magneto-thermo-viscoelastic media have been derived in the form of a vector matrix differential equation in the Laplace transform domain for a one dimensional problem. These equations have been solved by the eigenvalue approach to determine deformations, stress, and temperature. The results have been compared to those available in the existing literature. The graphs have been drawn to show the effect of rotation in the medium. 相似文献