全文获取类型
收费全文 | 53230篇 |
免费 | 8501篇 |
国内免费 | 5659篇 |
专业分类
化学 | 37355篇 |
晶体学 | 641篇 |
力学 | 3075篇 |
综合类 | 328篇 |
数学 | 5955篇 |
物理学 | 20036篇 |
出版年
2024年 | 182篇 |
2023年 | 1120篇 |
2022年 | 2078篇 |
2021年 | 2197篇 |
2020年 | 2272篇 |
2019年 | 2141篇 |
2018年 | 1829篇 |
2017年 | 1776篇 |
2016年 | 2607篇 |
2015年 | 2639篇 |
2014年 | 3099篇 |
2013年 | 3954篇 |
2012年 | 4848篇 |
2011年 | 4785篇 |
2010年 | 3322篇 |
2009年 | 3112篇 |
2008年 | 3337篇 |
2007年 | 2955篇 |
2006年 | 2651篇 |
2005年 | 2276篇 |
2004年 | 1739篇 |
2003年 | 1388篇 |
2002年 | 1275篇 |
2001年 | 1018篇 |
2000年 | 895篇 |
1999年 | 1045篇 |
1998年 | 856篇 |
1997年 | 807篇 |
1996年 | 794篇 |
1995年 | 726篇 |
1994年 | 612篇 |
1993年 | 519篇 |
1992年 | 430篇 |
1991年 | 392篇 |
1990年 | 331篇 |
1989年 | 240篇 |
1988年 | 178篇 |
1987年 | 163篇 |
1986年 | 159篇 |
1985年 | 139篇 |
1984年 | 87篇 |
1983年 | 93篇 |
1982年 | 55篇 |
1981年 | 39篇 |
1980年 | 29篇 |
1979年 | 18篇 |
1977年 | 18篇 |
1976年 | 20篇 |
1975年 | 21篇 |
1972年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Xin Yang Qingbiao Li Huixuan Wang Jiale Huang Liqin Lin Wenta Wang Daohua Sun Yuanbo Su James Berya Opiyo Luwei Hong Yuanpeng Wang Ning He Lishan Jia 《Journal of nanoparticle research》2010,12(5):1589-1598
The development of dependable, environmentally benign processes for the synthesis of nanoscale materials is an important aspect of nanotechnology. In the present study, we report one-pot biogenic fabrication of palladium nanoparticles by a simple procedure using broth of Cinnamomum camphora leaf without extra surfactant, capping agent, and/or template. The mean size of palladium nanoparticles, ranging from 3.2 to 6.0 nm, could be facilely controlled by merely varying the initial concentration of the palladium ions. The polyols components and the heterocyclic components were believed to be responsible for the reduction of palladium ions and the stabilization of palladium nanoparticles, respectively. 相似文献
962.
Abstract
This article describes a facile green strategy for preparing the Ni(OH)2 microsphere assembled by nanoribbons by the template of the squama inner coat of onion at mild condition. The method is simple and effective. The results of SEM show the products are Ni(OH)2 microspheres with diameters in the range of 500–2,500 nm. The results of TEM show the microsphere is assembly by nanoribbons, with thickness in the range of 30–50 nm. The products were characterized by powder X-ray diffraction, IR, and thermogravimetric analysis. A possible formation mechanism was also proposed. 相似文献963.
Yuming Yang Hua Lai Haitao Xu Chunyan Tao Hua Yang 《Journal of nanoparticle research》2010,12(1):217-225
In order to investigate the correlations of morphologies and optical properties, different morphologies of Eu-doped ZnO were
synthesized by different methods. Specifically, the structure of SiO2/ZnO:Eu nanoflower was synthesized for the first time and has not been reported previously. One percent was chosen as the
Eu doping concentration. The relations of the morphology, diameter, and uniformity with the PL intensity were examined. The
PL intensity of ZOE samples has a close relationship with the morphology. The PL intensity order of the different morphologies
of ZnO:Eu is as follows: nanorod arrays > thin film > nanospheres > nanoparticles > nanoflowers > nanorods. The PL intensity
of nanomaterials is larger, if the diameter of the nanomaterials is larger. However, the size of diameter is not the most
important reason. It was found that the sample uniformity plays a key role on ZnO:Eu PL intensity. ZnO:Eu with small particle
diameters may have strong photoluminescence intensity, if the nanoparticles are uniform. 相似文献
964.
965.
J.-B. Laloë T. Yang T. Kimura Y. Otani 《Journal of magnetism and magnetic materials》2009,321(22):3829-3832
We investigate the injection of a pure spin current into a non-magnetic Cu wire in a lateral spin valve. We detect the spin accumulation occurring at the interfaces between the magnetic nanopillars and the non-magnetic wire in the non-local geometry. We confirm that the accumulated spins diffuse equally in the Cu wire irrespective of the presence of a charge current. The inversion of the injector and detector magnetic nanopillars does not affect the spin signal, in agreement with analytical predictions for this system. 相似文献
966.
In this paper, we investigate the positive solutions of a second-order system with impulse effects. By using critical point theory the existence result of positive solutions is obtained. 相似文献
967.
Using the method proposed by Banerjee and Majhi, we researched fermion tunneling from cylindrical symmetric black hole, and
obtained the correctional entropy. In our work, we first prove that the ratios of the wave function’s components are constants
near the horizon, so the reasonable action form of the Dirac equation can then be gotten. From the method beyond semiclassical
approximation, we finally calculate the Hawking temperature and correctional entropy. 相似文献
968.
Bioactive membranes for guided tissue regeneration would be of value for periodontal therapy. Chitosan-multiwall carbon nanotube (CS-MWNT) composites were treated to deposit nanoscopic apatite for MWNT proportions of 0-4 mass%. Fourier-transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray analysis, and X-ray diffraction were used for characterization. Apatite was formed on the CS-MWNT composites at low MWNT concentrations, but the dispersion of the MWNT affects the crystallite size and the Ca/P molar ratio of the composite. The smallest crystallite size was 9 nm at 1 mass% MWNT. 相似文献
969.
Yang?LiuEmail author Yanwei?Du Hong?Li Jinfeng?Wang 《Journal of Applied Mathematics and Computing》2015,47(1-2):103-117
In this article, an \(H^1\)-Galerkin mixed finite element (MFE) method for solving time fractional reaction–diffusion equation is presented. The optimal time convergence order \(O(\varDelta t^{2-\alpha })\) and the optimal spatial rate of convergence in \(H^1\) and \(L^2\)-norms for variable \(u\) and its gradient \(\sigma \) are derived. Moreover, some numerical results are shown to support our theoretical analysis. 相似文献
970.