全文获取类型
收费全文 | 1246篇 |
免费 | 68篇 |
国内免费 | 137篇 |
专业分类
化学 | 778篇 |
晶体学 | 7篇 |
力学 | 48篇 |
综合类 | 10篇 |
数学 | 237篇 |
物理学 | 371篇 |
出版年
2025年 | 3篇 |
2024年 | 21篇 |
2023年 | 71篇 |
2022年 | 57篇 |
2021年 | 81篇 |
2020年 | 104篇 |
2019年 | 57篇 |
2018年 | 50篇 |
2017年 | 66篇 |
2016年 | 48篇 |
2015年 | 89篇 |
2014年 | 109篇 |
2013年 | 116篇 |
2012年 | 118篇 |
2011年 | 54篇 |
2010年 | 42篇 |
2009年 | 42篇 |
2008年 | 24篇 |
2007年 | 18篇 |
2006年 | 21篇 |
2005年 | 15篇 |
2003年 | 11篇 |
2002年 | 7篇 |
2001年 | 19篇 |
2000年 | 6篇 |
1999年 | 23篇 |
1998年 | 11篇 |
1997年 | 6篇 |
1991年 | 3篇 |
1989年 | 3篇 |
1988年 | 13篇 |
1987年 | 31篇 |
1986年 | 18篇 |
1984年 | 5篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1972年 | 4篇 |
1971年 | 8篇 |
1970年 | 2篇 |
1969年 | 3篇 |
1968年 | 3篇 |
1967年 | 7篇 |
1966年 | 6篇 |
1965年 | 4篇 |
1964年 | 4篇 |
1963年 | 5篇 |
1962年 | 6篇 |
排序方式: 共有1451条查询结果,搜索用时 0 毫秒
1.
Numerical Algorithms - Iterative algorithms based on thresholding, feedback, and null space tuning (NST+HT+FB) for sparse signal recovery are exceedingly effective and efficient, particularly for... 相似文献
2.
S. Kataria Satyaprakash Sahoo S.A. Barve S. Dash D.S. Patil A.K. Tyagi A.K. Arora 《Solid State Communications》2009,149(43-44):1881-1883
Diamond-like carbon films are deposited on silicon substrates at different substrate bias using ECR-CVD technique. Raman spectroscopic studies show the presence of broad G and D peaks. In contrast to the position of D peak, the G peak shows a systematic red-shift with increase in the bias voltage. From the analysis it is found that an increase in bias voltage decreases the sp2 cluster diameter. Furthermore, two additional Raman peaks at around 690 and 880 cm?1 are also observed. These peaks, forbidden in the first order Raman scattering, arise due to the breakdown of phonon selection rule in graphitic nanoclusters. 相似文献
3.
J. Chee 《Annals of Physics》2012,327(11):2853-2864
For the Landau problem with a rotating magnetic field and a confining potential in the (changing) direction of the field, we derive a general factorization of the time evolution operator that includes the adiabatic factorization as a special case. The confining potential is assumed to be of a general form and it can correspond to nonlinear Heisenberg equations of motion. The rotation operator associated with the solid angle Berry phase is used to transform the problem to a rotating reference frame. In the rotating reference frame, we derive a natural factorization of the time evolution operator by recognizing the crucial role played by a gauge transformation. The major complexity of the problem arises from the coupling between motion in the direction of the magnetic field and motion perpendicular to the field. In the factorization, this complexity is consolidated into a single operator which approaches the identity operator when the potential confines the particle sufficiently close to a rotating plane perpendicular to the magnetic field. The structure of this operator is clarified by deriving an expression for its generating Hamiltonian. The adiabatic limit and non-adiabatic effects follow as consequences of the general factorization which are clarified using the magnetic translation concept. 相似文献
4.
5.
Ba0.5Sr0.5Ti0.99Co0.01O3 (BSTC) thin films have been fabricated with pulsed laser deposition on Nb-doped SrTiO3 (STN) substrate. In Pt/BSTC/STN capacitor, we systematically investigated the capacitance, leakage current and polarization versus bias voltage characteristics, and found that curves of capacitance versus voltage and leakage current versus voltage were not symmetric, and polarization hysteresis loop exhibited large relaxation of the remnant polarization at negatively poled state. A detailed analysis of capacitance data demonstrated a difference of the built-in voltage between top Pt/BSTC interface (Vb,t=2.5 V) and bottom BSTC/STN interface (Vb,b=1.1 V). Such different built-in voltages lead to the presence of an internal electric field, which results in asymmetric electric characteristics in Pt/BSTC/STN capacitor. 相似文献
6.
针对目前舌诊研究中在舌体信息全面获取方面存在严重不足,将高光谱技术用到舌诊的研究中来,提出了一种基于X-Y振镜扫描式舌诊高光谱采集系统.通过模拟实验,采集与舌体大小相似图片的高光谱信息,验证了该系统可以用于舌体高光谱信息采集,实验结果表明,与现有舌诊客观化研究相比,该系统可以获得更多的舌体信息,为舌诊客观化研究提供了一... 相似文献
7.
Bei Xi Yong-Feng Guo Ya-Jun Shen Jian-Guo Tan Ming Liu 《Chinese Journal of Physics (Taipei)》2017,55(1):1-9
We study the transition problems in a piecewise nonlinear model induced by correlated multiplicative non-Gaussian noise and additive Gaussian white noise. Firstly, applying the path integral approach, the unified colored noise approximation, the analytical expression of the steady-state probability density function (SPD) is derived. Then the change regulation of the SPD is analyzed with the change of the strength and relevance of multiplicative noise and additive noise. From numerical computations we obtain some new nonlinear phenomena: the transition can be induced by the cross-correlation strength between noises, the non-Gaussian noise intensity and the Gaussian noise intensity as well as the non-Gaussian noise deviation parameter. This indicates that the effect of the non-Gaussian noise intensity on SPD is the same as that of the Gaussian noise intensity. Moreover, we also find the correlation time of the non-Gaussian noise can not induce the transition. 相似文献
8.
A facile hydrothermal method to synthesize flower-like Sn-doped ZnO (FLSn-ZnO) nanostructures is described. The obtained hierarchical architectures of FLSn-ZnO are found to be assembled with abundant regular-shaped nanosheets and nanoparticles. A possible formation mechanism is proposed on the base of a series of control experiments. The tests show that FLSn-ZnO architectures exhibit higher photocatalytic activity in the degrading Rhodamine B and tetracycline aqueous solution than pure ZnO under UV-light irradiation. And photocurrent response and photoluminescence of ZnO and FLSn-ZnO demonstrates that in photocatalytic performance, the latter is higher. 相似文献
9.
A robust 4,8-connected Tb-based metal-organic framework (Tb-MOF) with paddle wheel-shaped {Tb2(COO)4} subunits extended by C3-symmetric 3,3',3''-[1,3,5-benzenetriyltris(carbonylimino)]tris-benzoate connector was hydrothermally synthesized, showing highly environmental stability, good dispersion and intense green emission in water system. Resulting critically from the well suppressed absorption towards the excitation energy, the Tb-MOF exhibits rapid and efficient fluorescent response towards nitroimidazole antibiotics with strong quenching constants and low detection limits of 1.59 × 104 m –1 and 2.4 μM for metronidazole as well as 1.62 × 104 m –1 and 2.9 μM for dimetridazole. Moreover, the sensitive and selective identification of the Tb-MOF has strong anti-interference and excellent regeneration ability, which endows the promising applications of the Tb-MOF as fluorescent sensing materials. 相似文献
10.
《中国化学快报》2020,31(9):2309-2313
Conductive MOFs could exhibit full potential as integrated electrode materials for supercapacitors without interference from additional conductive additives. Here we report an anionic Co-MOF cage with zeolite framework, which was balanced by the redox-active guest [Co(H2O)6]2+ and protonated [(CH3)2NH2]2+ ions. Benefit from the unique ion skeleton structure, Co-MOF exhibits a conductivity higher than most of reported MOFs with the value of 1.42 × 10-3 S/cm, which can be directly fabricated as electrode for supercapacitors. A maximum specific capacitance of 236.2 F/g can be achieved at a current density of 1 A/g of Co-MOF. Additionally, the electric performance and morphology of this Co-MOF can be modified by cetyltrimethylammonium bromide (CTAB) and the maximum specific capacitance could increase up to 334 F/g at 1 A/g when the ratio of ligand and CTAB is 1:6 (Co-MOF-6). Furthermore, the specific capacitance can retain at 64.04% and 77.92% of the initial value after 3000 cycles of Co-MOF and Co-CTAB-6, respectively. Obviously, the addition of CTAB further improves both capacitance and cycle stability. 相似文献