全文获取类型
收费全文 | 1270篇 |
免费 | 51篇 |
国内免费 | 2篇 |
专业分类
化学 | 813篇 |
晶体学 | 5篇 |
力学 | 63篇 |
数学 | 127篇 |
物理学 | 315篇 |
出版年
2024年 | 6篇 |
2023年 | 17篇 |
2022年 | 23篇 |
2021年 | 26篇 |
2020年 | 51篇 |
2019年 | 43篇 |
2018年 | 45篇 |
2017年 | 33篇 |
2016年 | 59篇 |
2015年 | 30篇 |
2014年 | 46篇 |
2013年 | 98篇 |
2012年 | 119篇 |
2011年 | 142篇 |
2010年 | 79篇 |
2009年 | 59篇 |
2008年 | 75篇 |
2007年 | 63篇 |
2006年 | 61篇 |
2005年 | 48篇 |
2004年 | 29篇 |
2003年 | 17篇 |
2002年 | 26篇 |
2001年 | 9篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 6篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1989年 | 4篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 8篇 |
1975年 | 3篇 |
1973年 | 5篇 |
1968年 | 2篇 |
1925年 | 2篇 |
排序方式: 共有1323条查询结果,搜索用时 15 毫秒
141.
Using the crystal structure, a comprehensive interpretation of the origin of ferroelectricity in the hydrogen bonded triglycine
family of crystals is given. Our detailed analysis showed that the instability of nitrogen double well potential plays a driving
role in the mechanism of the ferroelectric transitions in these crystals. 相似文献
142.
143.
Critical comparisons are drawn between the basic electrical properties of semiconductor/metal, semiconductor/liquid, and semiconductor/conducting polymer junctions. A theoretical model is developed to describe the basic current-voltage properties of semiconductor contacts, with emphasis on the contrasts between ideal and observed behavior. Using the concepts from this model, the characteristics of a variety of semiconductor contacts are evaluated. The discussion focuses on the following semiconductors: Si, GaAs, InP, and II-VI compounds based on the Cd-(chalcogenide) materials. 相似文献
144.
Subhashis Nag 《Proceedings Mathematical Sciences》1991,101(3):215-218
The Sampson-Wolf model of Teichmüller space (using harmonic mappings) is shown to be exactly the same as the more recent Hitchin
model (utilizing self-dual connections). Indeed, it is noted how the self-duality equations become the harmonicity equations.
An interpretation of the modular group action in this model is mentioned. 相似文献
145.
Transient velocity-field characteristics have been computed for GaAs channels having lengths of 0.1, 0.2, 0.5, 1, and 20 μm for electric fields between 1 and 50 kV/cm at 300 K. The results are compared with earlier calculations and the significant features of the computed results are discussed. It is found that the electron motion for all channel lengths and for all fields is significantly affected by collisions. The threshold field for negative differential mobility increases, and the magnitude of the differential mobility decreases with decrease in the length of the sample. The maximum steady-state velocity increases with decrease in the length and may be as high as 5.4×107 cm/s for 0.1 μm samples. 相似文献
146.
Under hot-electron conditions, noise arises both from fluctuations in the carrier velocity and the carrier collision time. The magnitudes of these two contributions are calculated by the Monte-Carlo method for InSb at 77°K. 相似文献
147.
Amit K. Hui Mark R. McKeever Joel Tellinghuisen 《Journal of Quantitative Spectroscopy & Radiative Transfer》1979,21(5):387-396
The OH A2Σ+ → X2Π system is used as a diagnostic tool for temperature measurements of Tesla discharges in Ar and He seeded with 0.5 torr H2O. From relative intensities of low-N′ lines in the 0-0 band we obtain temperatures which are independent of pressure for the range 100–650 torr and which are only a few degrees higher than the estimated wall temperatures. A check on the theoretical line strengths for OH A → X shows 1% agreement for main-branch transitions but only 5% agreement for satellite lines. Self-absorption problems are encountered and corrected for in the He discharge work; from the ≈10% magnitude of the correction, there are significant amounts (8 mtorr) of ground-state OH produced in the He Tesla discharge. 相似文献
148.
We prove a conjecture of Lauchli and Leonard that every sentence of the theory of linear order which has a model, has a model with a finitely axiomatized theory. 相似文献
149.
The B → X (2870–3100 Å) and D → X (2250–2370 Å) band systems of 136Xe35Cl are photographed and vibrationally analyzed. A simultaneous least-squares fit of 41 band-heads in the B-X system and 35 in D-X yields, in part, the following constants (in cm?1): TeB = 32 405.8, TeD = 42 347.9, ωeB = 194.75, ωeD = 204.34, ωeX = 26.22. The ground state dissociation energy (″e) is estimated to be 281 ± 10 cm?1. Potential curves are derived for all three states through Franck-Condon calculations. From these curves the D-state internuclear distance is 0.09 ± .02 Å smaller than the B-state distance. 相似文献
150.
An iterative calculation of the warm electron coefficient is presented considering polar mode scattering in a parabolic band. Electron-electron collisions are assumed strong enough to establish a Maxwellian distribution function. The results vary considerably from those of the displaced Maxwellian calculation which has been used earlier for the interpretation of experimental results. 相似文献