全文获取类型
收费全文 | 710篇 |
免费 | 24篇 |
国内免费 | 1篇 |
专业分类
化学 | 318篇 |
晶体学 | 5篇 |
力学 | 63篇 |
数学 | 49篇 |
物理学 | 225篇 |
无线电 | 75篇 |
出版年
2022年 | 7篇 |
2021年 | 8篇 |
2020年 | 9篇 |
2019年 | 7篇 |
2018年 | 9篇 |
2017年 | 7篇 |
2016年 | 16篇 |
2015年 | 23篇 |
2014年 | 21篇 |
2013年 | 40篇 |
2012年 | 35篇 |
2011年 | 28篇 |
2010年 | 31篇 |
2009年 | 21篇 |
2008年 | 51篇 |
2007年 | 32篇 |
2006年 | 35篇 |
2005年 | 27篇 |
2004年 | 28篇 |
2003年 | 21篇 |
2002年 | 21篇 |
2001年 | 17篇 |
2000年 | 22篇 |
1999年 | 9篇 |
1998年 | 8篇 |
1997年 | 11篇 |
1996年 | 15篇 |
1995年 | 9篇 |
1994年 | 18篇 |
1993年 | 19篇 |
1992年 | 11篇 |
1991年 | 4篇 |
1990年 | 8篇 |
1989年 | 10篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 7篇 |
1973年 | 7篇 |
1972年 | 4篇 |
排序方式: 共有735条查询结果,搜索用时 15 毫秒
21.
The determination by neutron activation of trace quantities of calcium, strontium and barium in single crystals of alkali halides has been studied. The matrix is eliminated before the irradiation by an ion-exchange procedure. Gamma spectroscopy after radiochemical separation is used to determine strontium and barium. Calcium is determined by measuring the β-activity of 49Sc formed by the decay of 49Ca. Long-lived radioactive tracers are used to determine the chemical yields. 相似文献
22.
23.
G. F. Cerofolini A. Giussani F. Carone Fabiani A. Modelli D. Mascolo D. Ruggiero D. Narducci E. Romano 《Surface and interface analysis : SIA》2007,39(10):836-844
A combined analysis, based on angle‐resolved X‐ray photoelectron spectroscopy and multiple‐internal‐reflection infrared spectroscopy, of the (1 0 0) silicon surface after etching in dilute aqueous solution of HF is presented. The analysis shows that the surface is mainly formed by a heterogeneous distribution of SiH, SiH2 and SiH3 terminations, but contains (in addition to sub‐stoichiometric oxidized silicon) a form of reduced silicon, not consistent with the currently accepted picture of the native HFaq‐etched surface. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
24.
25.
Vito Dario Camiola Giovanni Mascali Vittorio Romano 《Continuum Mechanics and Thermodynamics》2012,24(4-6):417-436
A nanoscale double-gate MOSFET is simulated with an energy-transport subband model for semiconductors formulated starting from the moment system derived from the Schr?dinger–Poisson–Boltzmann equations. The system is closed on the basis of the maximum entropy principle and includes scattering of electrons with acoustic and non-polar optical phonons. The proposed expression of the entropy combines quantum effects and semiclassical transport by weighting the contribution of each subband with the square modulus of the envelope functions arising from the Schr?dinger–Poisson subsystem. The simulations show that the model is able to capture the relevant confining and transport features and assess the robustness of the numerical scheme. 相似文献
26.
27.
α-Acetoxy acid methyl esters are prepared in excellent yields by treating aliphatic α-acetoxy dimethyl acetals with trichloroisocyanuric acid in DMF. 相似文献
28.
29.
A convergent synthesis applicable to the preparation of oxidized prenylchalcones is reported that relies on key Claisen–Schmidt, Mitsunobu, and vinyl/benzyl Stille coupling operations. The synthetic strategy was applied towards the preparation of the natural products morachalcone A and isogemichalcones B & C, allowing their preparation in less than 10 steps and 6–8% overall yield. 相似文献
30.