全文获取类型
收费全文 | 4023篇 |
免费 | 490篇 |
国内免费 | 432篇 |
专业分类
化学 | 262篇 |
晶体学 | 18篇 |
力学 | 171篇 |
综合类 | 55篇 |
数学 | 2783篇 |
物理学 | 1656篇 |
出版年
2024年 | 10篇 |
2023年 | 61篇 |
2022年 | 80篇 |
2021年 | 90篇 |
2020年 | 131篇 |
2019年 | 110篇 |
2018年 | 127篇 |
2017年 | 116篇 |
2016年 | 121篇 |
2015年 | 104篇 |
2014年 | 179篇 |
2013年 | 409篇 |
2012年 | 168篇 |
2011年 | 253篇 |
2010年 | 241篇 |
2009年 | 261篇 |
2008年 | 279篇 |
2007年 | 258篇 |
2006年 | 262篇 |
2005年 | 186篇 |
2004年 | 146篇 |
2003年 | 189篇 |
2002年 | 185篇 |
2001年 | 141篇 |
2000年 | 131篇 |
1999年 | 113篇 |
1998年 | 101篇 |
1997年 | 89篇 |
1996年 | 62篇 |
1995年 | 59篇 |
1994年 | 44篇 |
1993年 | 27篇 |
1992年 | 26篇 |
1991年 | 31篇 |
1990年 | 16篇 |
1989年 | 17篇 |
1988年 | 13篇 |
1987年 | 18篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1984年 | 12篇 |
1983年 | 4篇 |
1982年 | 16篇 |
1981年 | 6篇 |
1980年 | 11篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1973年 | 5篇 |
排序方式: 共有4945条查询结果,搜索用时 15 毫秒
111.
The cathodoluminescence (CL) from indented Fe doped MgO single crystals has been studied with the scanning electron microscope and the results have been compared with the CL from undoped crystals. As in the undoped crystals, the iron doped crystals show in the deformed regions an enhanced luminescence emission but it has been found that iron acts as a quencher of luminescence. The results indicate that in the blue emission of the deformed crystals there is not a noticeable contribution of iron. From the evolution of CL with the irradiation time in the electron microscope it is concluded that the total Fe content influences the CL emission more than the Fe3+ content. 相似文献
112.
A. Bande 《Molecular physics》2019,117(15-16):2014-2028
ABSTRACTRecently, highly accurate multi-configuration time-dependent Hartree electron dynamics calculations demonstrated the efficient long-range energy transfer inter-Coulombic decay (ICD) process to happen in charged semiconductor quantum dot (QD) pairs. ICD is initiated by intraband photoexcitation of one of the QDs and leads to electron emission from the other within a duration of about 150 ps. On the same time scale electronically excited states are reported to relax due to the coupling of electrons to acoustic phonons. Likewise, phonons promote ionisation. Here, the QDs' acoustic breathing mode is implemented in a frozen-phonon approach. A detailed comparison of the phonon effects on electron relaxation and emission as well as on the full ICD process is presented, which supports the previous empirical finding of ICD being the dominant decay channel in paired QDs. In addition the relative importance of phonon–phonon, phonon–electron and electron–electron interaction is analysed. 相似文献
113.
Composite material consisting of highly luminescent Zn(Cd)O:Ga powder embedded in the silica matrix was prepared. It was found out that ZnO:Ga with less developed crystals (i.e. annealed at lower temperatures) is more prone to interact with the SiO2 matrix and form zinc silicates, which in turn resulted in the decrease in the excitonic emission. Pre-annealing of the powders at temperatures above 600 °C prevented the interaction with the SiO2 matrix. ZnO:Ga with well-developed crystals at such a high temperatures was not affected by the matrix and retained its properties, i.e. high radioluminescence intensity and ultrafast sub nanosecond photoluminescence decay. Introducing Cd into the ZnO lattice caused observable red shift in the excitonic luminescence, without negatively affecting the total intensity or the decay. 相似文献
114.
Yuichi Mori Kosei Nakaya Xianqing Piao Kazuhiro Yamamoto Akira Otomo Shiyoshi Yokoyama 《Journal of polymer science. Part A, Polymer chemistry》2012,50(7):1254-1260
A methacrylate‐based crosslinking hyperbranced polymers have been synthesized through initiator‐fragment incorporation radical polymerization and used for the temperature stable electro‐optic (EO) polymer application. This polymer consists of methyl methacrylate, 2‐metacryloxyethyl isocyanate, and ethylene glycol dimethacrylate (EGDMA) monomers. The use of EGDMA as a bifunctional unit resulted in the solvent‐soluble crosslinking hyperbranched chain, so that the EO polymer enhanced glass transition temperatures. A phenyl vinylene thiophene vinylene bridge nonlinear optical chromophore was attached to the polymer backbone as the side‐chain by a post‐functionalization reaction. The loading concentration of the chromophore was varied between 30 and 50 wt % by simply changing the mixing ratio of the precursor polymer to the chromophore. The synthesized EO polymers produced optical quality films with a light propagation loss of 0.61 dB/cm in a slab waveguide at 1.31 μm. The electrically poled film had an EO coefficient (r33) of 139 pm/V at 1.31 μm. The EO crosslinking hyperbranced polymer had a high‐glass transition temperature of 170 °C, and exhibited excellent temporal stability of the EO activity at 85 °C for 500 h. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
115.
We prove an invariant Harnack’s inequality for operators in non-divergence form structured on Heisenberg vector fields when the coe?cient matrix is uniformly positive definite, continuous, and symplectic. The method consists in constructing appropriate barriers to obtain pointwise-to-measure estimates for supersolutions in small balls, and then invoking the axiomatic approach developed by Di Fazio, Gutiérrez, and Lanconelli to obtain Harnack’s inequality. 相似文献
116.
117.
After our article, Physica A 391 (2012) 107–112, had been published online, T. Hillen told us about a theorem by Osaki, relevant for our numerical simulations. 相似文献
118.
We study “large” nonnegative solutions for a class of quasilinear equations model of which is We give a sufficient condition on the exponents and for the removability of isolated singularities. 相似文献
119.
Explicit and partly sharp estimates are given of integrals over the square of Bessel functions with an integrable weight which can be singular at the origin. They are uniform with respect to the order of the Bessel functions and provide explicit bounds for some smoothing estimates as well as for the L2 restrictions of Fourier transforms onto spheres in which are independent of the radius of the sphere. For more special weights these restrictions are shown to be Hölder continuous with a Hölder constant having this independence as well. To illustrate the use of these results a uniform resolvent estimate of the free Dirac operator with mass in dimensions is derived. 相似文献
120.
《Stochastic Processes and their Applications》2019,129(6):2086-2129
Many properties of Brownian motion on spaces with varying dimension (BMVD in abbreviation) have been explored in Chen and Lou (2018). In this paper, we study Brownian motion with drift on spaces with varying dimension (BMVD with drift in abbreviation). Such a process can be conveniently defined by a regular Dirichlet form that is not necessarily symmetric. Through the method of Duhamel’s principle, it is established in this paper that the transition density of BMVD with drift has the same type of two-sided Gaussian bounds as that for BMVD (without drift). As a corollary, we derive Green function estimate for BMVD with drift. 相似文献