全文获取类型
收费全文 | 2223篇 |
免费 | 83篇 |
国内免费 | 15篇 |
专业分类
化学 | 1399篇 |
晶体学 | 21篇 |
力学 | 111篇 |
数学 | 205篇 |
物理学 | 585篇 |
出版年
2023年 | 17篇 |
2022年 | 24篇 |
2021年 | 33篇 |
2020年 | 29篇 |
2019年 | 26篇 |
2018年 | 33篇 |
2017年 | 28篇 |
2016年 | 53篇 |
2015年 | 64篇 |
2014年 | 89篇 |
2013年 | 101篇 |
2012年 | 170篇 |
2011年 | 196篇 |
2010年 | 123篇 |
2009年 | 125篇 |
2008年 | 132篇 |
2007年 | 125篇 |
2006年 | 122篇 |
2005年 | 102篇 |
2004年 | 74篇 |
2003年 | 77篇 |
2002年 | 48篇 |
2001年 | 47篇 |
2000年 | 45篇 |
1999年 | 28篇 |
1998年 | 25篇 |
1997年 | 22篇 |
1996年 | 29篇 |
1995年 | 31篇 |
1994年 | 16篇 |
1993年 | 26篇 |
1992年 | 29篇 |
1991年 | 24篇 |
1990年 | 15篇 |
1989年 | 23篇 |
1988年 | 23篇 |
1987年 | 11篇 |
1986年 | 8篇 |
1985年 | 13篇 |
1984年 | 10篇 |
1983年 | 13篇 |
1982年 | 8篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 10篇 |
1976年 | 8篇 |
1975年 | 10篇 |
1974年 | 11篇 |
1973年 | 10篇 |
排序方式: 共有2321条查询结果,搜索用时 15 毫秒
101.
Cheng-Cheng Tsai Zhi-Yao Tsai Ming-Yu Tseng Wei-Ping Hu 《International journal of quantum chemistry》2020,120(14):e26238
We have developed a new database of structures and bond energies of 59 noble-gas-containing molecules. The structures were calculated by CCSD(T)/aug-cc-pVTZ methods and the bond energies were obtained using the CCSD(T)/complete basis set method. Many wavefunction-based and density functional theory methods have been benchmarked against the 59 accurate bond energies. Our results show that the MPW1B95, B2GP-PLYP, and DSD-BLYP functionals with the aug-cc-pVTZ basis set excel in predicting the bond energies of noble-gas molecules with mean unsigned errors (MUEs) of 2.0 to 2.1 kcal/mol. When combinations of Dunning's basis sets are used, the MPW1B95, B2GP-PLYP, DSD-BLYP, and BMK functionals give significantly lower MUEs of 1.6 to 1.9 kcal/mol. Doubly hybrid methods using B2GP-PLYP and DSD-BLYP functionals and MP2 calculation also provide satisfactory accuracy with MUEs of 1.4 to 1.5 kcal/mol. If the Ng bond energies and the total atomization energies of a group of 109 main-group molecules are considered at the same time, the MPW1B95/aug-cc-pVTZ single-level method (MUE = 2.7 kcal/mol) and the B2GP-PLYP and DSD-PLYP functionals with combinations of basis sets or using the doubly hybrid method (MUEs = 1.9-2.2 kcal/mol) give the overall best result. 相似文献
102.
Jen-Hwan Tsai 《Journal of luminescence》2010,130(10):1680-1686
In this paper, a shift in the photoluminescence (PL) peak from blue to near-infrared region was observed in the Si+-implanted 400-nm-thick SiO2 films with the rapid thermal annealing (RTA) method only. As the Si+-fluence was 1×1016 ions/cm2, a blue band was observed in the films after RTA at 1050 °C for 5 s in dry-N2 atmosphere; then, the band shifted from blue to orange upon increasing the holding temperature of RTA to 1250 °C in the films after the isochronal RTA in dry N2. Furthermore, while the fluence was increased to 3×11016 ions/cm2 and the holding temperature was at the same range between 1050 and 1250 °C, the PL peak occurred between red and near-infrared regions. Although the RTA and conventional thermal annealing (CTA) methods produce a similar mechanism, the CTA method needs a much longer annealing-time and a higher Si+-implanted dose than the RTA method for producing the same shift and intensity of PL peak from the as-implanted sample. Therefore, the RTA method can produce the mechanism in the Si+-implanted sample with the PL energy between blue and near-infrared band in place of the CTA method. 相似文献
103.
This research proposes a newly developed stray light filter in order to eliminate stray light, which otherwise might severely reduce the performance of the con-focal microscopy presented in this research. First, an optical design for con-focal microscopy with a digital micro-mirror device (DMD) is illustrated; second, a newly developed stray light filter is presented, which functions to eliminate possible stray light and ghost images without any sacrifice of luminance. It indicates that not only can the optical system be much simplified but also that its resolution could be one step higher, because the system employs neither a pinhole nor a CCD camera lens. Experimental results are shown in the paper, demonstrating an increase in contrast of up to 60%. 相似文献
104.
Chia‐Cheng Tsai 《Numerical Methods for Partial Differential Equations》2010,26(1):206-220
Analytical particular solutions of splines and monomials are obtained for problems of thin plate resting on Pasternak foundation under arbitrary loadings, which are governed by a fourth‐order partial differential equation (PDEs). These analytical particular solutions are valuable when the arbitrary loadings are approximated by augmented polyharmonic splines (APS) constructed by splines and monomials. In our derivations, the real coefficient operator in the governing equation is decomposed into two complex coefficient operators whose particular solutions are known in literature. Then, we use the difference trick to recover the analytical particular solutions of the original operator. In addition, we show that the derived particular solution of spline with its first few directional derivatives are bounded as r → 0. This solution procedure may have the potential in obtaining analytical particular solutions of higher order PDEs constructed by products of Helmholtz‐type operators. Furthermore, we demonstrate the usages of these analytical particular solutions by few numerical cases in which the homogeneous solutions are complementarily solved by the method of fundamental solutions (MFS). © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2010 相似文献
105.
We propose a lumped element Josephson parametric amplifier with vacuum-gap-based capacitor.The capacitor is made of quasi-floating aluminum pad and on-chip ground.We take a fabrication process compatible with air-bridge technology,which makes our design adaptable for future on-chip integrated quantum computing system.Further engineering the input impedance,we obtain a gain above 20 dB over 162-MHz bandwidth,along with a quasi quantum-limit noise performance.This work should facilitate the development of quantum information processing and integrated superconducting circuit design. 相似文献
106.
Chi-Kwong Li Ming-Cheng Tsai Ya-Shu Wang Ngai-Ching Wong 《Journal of Mathematical Analysis and Applications》2022,505(2):125522
Let L be an additive map between (real or complex) matrix algebras sending Hermitian idempotent matrices to Hermitian idempotent matrices. We show that there are nonnegative integers with and an unitary matrix U such that We also extend this result to the (complex) von Neumann algebra setting, and provide a supplement to the Dye-Bunce-Wright Theorem asserting that every additive map of Hermitian idempotents extends to a Jordan ?-homomorphism. 相似文献
107.
Tai-Peng Tsai 《Journal of Differential Equations》2003,192(1):225-282
We consider a nonlinear Schrödinger equation with a bounded localized potential in . The linear Hamiltonian is assumed to have three or more bound states with the eigenvalues satisfying some resonance conditions. Suppose that the initial data is localized and small of order n in H1, and that its ground state component is larger than n3−ε with ε>0 small. We prove that the solution will converge locally to a nonlinear ground state as the time tends to infinity. 相似文献
108.
Recently, Li and Chang proposed an approximate model for assortment problems. Although their model is quite promising to find approximately global solution, too many 0–1 variables are required in their solution process. This paper proposes another way for solving the same problem. The proposed method uses iteratively a technique of piecewise linearization of the quadratic objective function. Numerical examples demonstrate that the proposed method is computationally more efficient than the Li and Chang method. 相似文献
109.
Chia-Lung Tsai Yow-Jon Lin Jia-Hong Chen Hsing-Cheng Chang Ya-Hui Chen Lance Horng Yu-Tai Shih 《Solid State Communications》2012,152(6):488-492
Zn0.8Co0.2O and Zn0.8Mn0.2O films were deposited on substrates by a sol–gel technique. X-ray diffraction, field-emission scanning electron microscopy, photoluminescence, and ferromagnetism measurements were used to characterize these dilute magnetic semiconductors. It is shown that the ferromagnetic properties might be related to the formation of acceptor-like defects in the Zn0.8Co0.2O and Zn0.8Mn0.2O films. It is found that ferromagnetic Zn0.8Mn0.2O has a higher Curie temperature than Zn0.8Co0.2O. In addition, the higher ratio of grain-boundary area to grain volume of Zn0.8Mn0.2O than Zn0.8Co0.2O indicates that grain boundaries and related acceptors are the intrinsic origin for ferromagnetism. 相似文献
110.
S.-K. Wang W.-C. Tsai L.-C. Chou J. Chen Y.-H. Wu T.-M. He K.-S. Feng C.-R. Wen 《Surface science》2012,606(13-14):1062-1070
Continuous-time photoelectron spectroscopy (PES) and continuous-time core-level photon-stimulated desorption (PSD) spectroscopy were used to study the monochromatic soft X-ray-induced reactions of CCl2F2 molecules adsorbed on Si(111)-7 × 7 at 30 K (CCl2F2 dose = 2.0 × 1014 molecules/cm2, ~ 0.75 monolayer) near the Si(2p) core level. Evolution of adsorbed CCl2F2 molecules was monitored by using continuous-time photoelectron spectroscopy at two photon energies of 98 and 120 eV to deduce the photolysis cross section as a function of energy. It was found that the photolysis cross sections for 98 and 120 eV photons are ~1.4 × 10? 18 and ~ 8.0 × 10? 18 cm2, respectively. Sequential F+ PSD spectra obtained by using continuous-time core-level photon-stimulated desorption spectroscopy in the photon energy range of 98–110 eV show the variation of their shapes with photon exposure and depict the formation of surface SiF species. The dissociation of CCl2F2 molecules adsorbed on Si(111)-7 × 7, irradiated by monochromatic soft X-ray in the photon energy range of 98–110 eV, is mainly due to dissociative electron attachment and indirect dipolar dissociation induced by photoelectrons emitted from the silicon surface. 相似文献