全文获取类型
收费全文 | 14835篇 |
免费 | 2574篇 |
国内免费 | 1123篇 |
专业分类
化学 | 3626篇 |
晶体学 | 135篇 |
力学 | 629篇 |
综合类 | 46篇 |
数学 | 867篇 |
物理学 | 9105篇 |
无线电 | 4124篇 |
出版年
2024年 | 24篇 |
2023年 | 109篇 |
2022年 | 185篇 |
2021年 | 249篇 |
2020年 | 287篇 |
2019年 | 284篇 |
2018年 | 326篇 |
2017年 | 417篇 |
2016年 | 511篇 |
2015年 | 537篇 |
2014年 | 736篇 |
2013年 | 1110篇 |
2012年 | 900篇 |
2011年 | 1096篇 |
2010年 | 794篇 |
2009年 | 1002篇 |
2008年 | 1050篇 |
2007年 | 1132篇 |
2006年 | 979篇 |
2005年 | 836篇 |
2004年 | 757篇 |
2003年 | 627篇 |
2002年 | 671篇 |
2001年 | 574篇 |
2000年 | 548篇 |
1999年 | 424篇 |
1998年 | 372篇 |
1997年 | 264篇 |
1996年 | 297篇 |
1995年 | 244篇 |
1994年 | 174篇 |
1993年 | 168篇 |
1992年 | 156篇 |
1991年 | 118篇 |
1990年 | 91篇 |
1989年 | 88篇 |
1988年 | 74篇 |
1987年 | 48篇 |
1986年 | 30篇 |
1985年 | 43篇 |
1984年 | 38篇 |
1983年 | 17篇 |
1982年 | 34篇 |
1981年 | 31篇 |
1980年 | 10篇 |
1979年 | 11篇 |
1978年 | 12篇 |
1977年 | 7篇 |
1976年 | 9篇 |
1973年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
新的光散射体系测定蛋白质的研究 总被引:1,自引:1,他引:0
以1,6-己二胺二吖啶为荧光探针,建立了一种新的蛋白质共振散射检测体系。实验考察了该吖啶荧光探针的共振散射特征光谱、散射反应稳定性,研究了缓冲介质pH、探针浓度等参数对测定蛋白质的影响。结果表明,当pH 8.9时,1,6-己二胺二吖啶染料的散射波长为470 nm;加入BSA,反应约9 min后,体系光散射强度达到最大并维持稳定,2 h内无明显变化。当1,6-己二胺二吖啶探针(浓度1.00×10-4mol·L-1)用量为3.00 mL时,蛋白质与1,6-己二胺二吖啶的光散射增强作用显著,共振散射强度随着BSA的增加而明显增强,光散射强度与蛋白质浓度成良好线性关系,线性浓度范围为1.00~5.00 μg·mL-1,检测限(3σ/K)为0.085 μg·mL-1。测定了血清样品,浓度为2.00~4.00 μg·mL-1,回收率为98.0%~101.7%,测定偏差小于1.7%。 相似文献
82.
O. Budriga V. Florescu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):205-210
We study Compton scattering on the ground state of the hydrogen atom in the presence of an intense low-frequency electric
field (the laser) of arbitrary polarization, for incident and scattered photons of energies around 15 keV. The adopted formalism
is the nonrelativistic one developed by Voitkiv et al. [J. Phys. B: At. Mol. Opt. Phys. 36, 1907 (2003)] and applied by them for a circularly polarized laser. We explore the spectrum and the electron energy distribution
in their dependence on the incident photon energy or electric field intensity, for different polarizations. 相似文献
83.
Izabela Bobowska Aleksandra Wypych-Puszkarz Agnieszka Opasinska Waldemar Maniukiewicz Piotr Wojciechowski 《Phase Transitions》2017,90(1):44-53
ABSTRACTEffects of the elevated temperature on the structure evolution of the ZnO nanorod array (ZNA) and their hybrid nanocomposite with layered (tetramethyl)ammonium titanate (LTMAT) prepared by the liquid phase deposition were investigated. The vertically oriented ZnO nanorods were deposited on a quartz plate by a chemical bath deposition method and then they were penetrated by the LTMAT using the dip-coating method from the water solution. As a result of such an experimental procedure, an assembly composed of the ZNA with LTMAT was obtained and called hybrid nanocomposite. Since the LTMAT converts to TiO2 upon subsequent sintering at 350 °C, it can be regarded as TiO2 precursor for the thermal treatment experiments. The experiments with ZNA and their hybrid nanocomposite at the elevated temperature revealed coalescence of the deposited ZnO nanorods and crystallization of zinc titanate with Zn2TiO4 stoichiometry. 相似文献
84.
Keitaro Tezuka Yue Jin Shan Kenji Ohoyama 《Journal of Physics and Chemistry of Solids》2007,68(11):2133-2137
Chromium(II) sulfide, Y2CrS4, prepared by a solid-state reaction of Y2S3 and CrS, showed an antiferromagnetic transition at 65 K. The neutron diffraction patterns at 10 and 90 K were both well refined with the space group Pca21. At 90 K, cell parameters were a=12.5518(13) Å, b=7.5245(8) Å, and c=12.4918(13) Å. At 10 K, magnetic peaks were observed, which could be indexed on the same unit cell. Magnetic moments of chromium ions were parallel to the b-axis and antiferromagnetically ordered in each set of the 4a sites. 相似文献
85.
Experimental evidence for surface segregation of Pt at (1 1 1) surfaces of ternary (Pt, Ni)3Al alloys is presented, based upon Auger electron spectroscopy, low energy ion scattering, and angle-resolved X-ray photoelectron spectroscopy. Density functional calculations in the dilute limit confirm that Pt segregation is energetically favored. 相似文献
86.
The directional scattering in photorefractive SBN crystal is reported.The self-pumped phase conjugation has been realized with the feedback of this directional scattering andthe performance parameters are compared with those of cat self-pumped phase conjugator. 相似文献
87.
P. Tils M. Loewenhaupt K. H. J. Buschow R. S. Eccleston 《Journal of magnetism and magnetic materials》2000,210(1-3)
Inelastic neutron scattering (INS) was used to study the magnetic excitations in the compounds Gd1−xYxFe2 and Gd2−xYxFe14B. Three inelastic magnetic lines were observed in the INS spectra of these compounds, the two smaller lines appearing as shoulders to the main line. From the concentration-dependent shift of the dominant magnetic line we have obtained experimental information of the strength of the Gd–Gd interaction in these materials and showed that the Gd–Gd contribution to the total molecular field experienced by the Gd moments is roughly an order of magnitude smaller than the contribution of the Gd–Fe interaction. Our results are compared with several earlier published results, including results of electronic band structure calculations. 相似文献
88.
Agnès Maurel 《Journal of Computational and Applied Mathematics》2010,234(6):1842-1850
The problem of how a wave propagates in an infinite medium filled with scatterers has revealed the notion of an effective medium: the mean wave propagates as in an homogeneous medium with complex index. Is this notion of an effective medium still valid when the scatterers are bounded in space? The problem is treated here for isotropic point scatterers. It is shown that (i) the waves propagate inside the slab with an effective wavenumber K being the same as that in an infinite medium, (ii) the reflection and transmission coefficients of the slab mainly behave as and at leading order, (iii) the reflection and transmission coefficients of a single interface are related to R and T with the usual law of optics and (iv) the boundary conditions to be applied at the interface are the continuity of the field and its first derivative for isotropic scatterers. Finally, numerical experiments in one dimension show satisfactory agreement with the presented theory. 相似文献
89.
90.
Nadia T. Zakharova Michael I. Mishchenko 《Journal of Quantitative Spectroscopy & Radiative Transfer》2001,70(4-6):465-471
We use the T-matrix method to compute the scattering matrix for randomly oriented circular ice cylinders with diameter-to-length ratios 1 and 20 and surface-equivalent-sphere size parameters up to 12. We show that wavelength-sized, sharp-edged ice plates with extreme diameter-to-length ratios possess the same scattering properties as smooth platelike spheroids: their phase functions are similar to those of surface-equivalent compact particles, whereas all other elements of the scattering matrix are typical of Rayleigh scattering. 相似文献