全文获取类型
收费全文 | 3514篇 |
免费 | 190篇 |
国内免费 | 19篇 |
专业分类
化学 | 2659篇 |
晶体学 | 36篇 |
力学 | 51篇 |
数学 | 267篇 |
物理学 | 710篇 |
出版年
2023年 | 14篇 |
2022年 | 68篇 |
2021年 | 81篇 |
2020年 | 66篇 |
2019年 | 73篇 |
2018年 | 50篇 |
2017年 | 49篇 |
2016年 | 142篇 |
2015年 | 107篇 |
2014年 | 154篇 |
2013年 | 222篇 |
2012年 | 285篇 |
2011年 | 303篇 |
2010年 | 180篇 |
2009年 | 166篇 |
2008年 | 224篇 |
2007年 | 220篇 |
2006年 | 179篇 |
2005年 | 168篇 |
2004年 | 186篇 |
2003年 | 126篇 |
2002年 | 140篇 |
2001年 | 62篇 |
2000年 | 81篇 |
1999年 | 40篇 |
1998年 | 21篇 |
1997年 | 17篇 |
1996年 | 28篇 |
1995年 | 27篇 |
1994年 | 17篇 |
1993年 | 20篇 |
1992年 | 38篇 |
1991年 | 20篇 |
1990年 | 6篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 17篇 |
1984年 | 7篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 10篇 |
1976年 | 5篇 |
1975年 | 7篇 |
1974年 | 11篇 |
1973年 | 4篇 |
排序方式: 共有3723条查询结果,搜索用时 31 毫秒
31.
The filling behavior of a room temperature solvent, perfluoromethylcyclohexane, in approximately 20 nm nanoporous alumina membranes was investigated in situ with small angle x-ray scattering. Adsorption in the pores was controlled reversibly by varying the chemical potential between the sample and a liquid reservoir via a thermal offset, DeltaT. The system exhibited a pronounced hysteretic capillary filling transition as liquid was condensed into the nanopores. These results are compared with Kelvin-Cohan theory, with a modified Derjaguin approximation, as well as with predictions by Cole and Saam. 相似文献
32.
Kab-Jin Kim Jae-Chul Lee Kyung-Ho Shin Hyun-Woo Lee Sug-Bong Choe 《Current Applied Physics》2013,13(1):228-236
Magnetic domain-wall (DW), interface between different magnetic domains, has received great attention due to its opportunities toward memory and logic devices as well as its abundant physical properties as a driven interface. Since recent advances of fabrication techniques allow us to scale down the devices, we are facing lower dimensional properties that should be elucidated undoubtedly. Here, we review recent progresses on DW dynamics in ferromagnetic nanowires and our recent experimental observation on the dimensionality transition of the DW dynamics driven by magnetic field and/or current. Our results show that the DW dynamics shows a transition from two to one dimensional behavior as the wire width decreases. In addition, we also demonstrate that the magnetic-field- and electric-current-driven DW dynamics in metallic ferromagnetic nanowires belong to the same universal class. 相似文献
33.
We investigated the film-thickness and ambient oxygen-pressure dependence of the electric field, EF, required to initiate unipolar resistance switching (URS) in Ta2O5?x thin films. We measured the dependence of EF by applying a triangular-waveform voltage signal to the film over a wide sweep-rate range (v = 20 mV s?1 to 5 MV s?1). Our results showed that the URS-EF was not influenced by the Ta2O5?x film thickness nor ambient oxygen-pressure. This suggested that the URS-forming process in Ta2O5?x thin films should be governed by thermally assisted dielectric breakdown in our measurement range. 相似文献
34.
Seung Wook Shin In Young Kim K.V. Gurav Chae Hwan Jeong Jae Ho Yun P.S. Patil Jeong Yong Lee Jin Hyeok Kim 《Current Applied Physics》2013,13(8):1837-1843
Cu2ZnSn(SxS1?x)4 (CZTSSe) thin films were prepared by annealing a stacked precursor prepared on Mo coated glass substrates by the sputtering technique. The stacked precursor thin films were prepared from Cu, SnS2, and ZnS targets at room temperature with stacking orders of Cu/SnS2/ZnS. The stacked precursor thin films were annealed using a tubular two zone furnace system under a mixed N2 (95%) + H2S (5%) + Se vaporization atmosphere at 580 °C for 2 h. The effects of different Se vaporization temperature from 250 °C to 500 °C on the structural, morphological, chemical, and optical properties of the CZTSSe thin films were investigated. X-ray diffraction patterns, Raman spectroscopy, and X-ray photoelectron spectroscopy results showed that the annealed thin films had a single kesterite crystal structure without a secondary phase. The 2θ angle position for the peaks from the (112) plane in the annealed thin films decreased with increasing Se vaporization temperature. Energy dispersive X-ray results showed that the presence of Se in annealed thin films increased from 0 at% to 42.7 at% with increasing Se vaporization temperatures. UV–VIS spectroscopy results showed that the absorption coefficient of all the annealed thin films was over 104 cm?1 and that the optical band gap energy decreased from 1.5 eV to 1.05 eV with increasing Se vaporization temperature. 相似文献
35.
36.
37.
In this study, p–n heterojunctions with La0.5Sr0.5CoO3 (LSCO) and Al-doped ZnO (AZO) thin films were fabricated by the radio frequency (r.f.) magnetron sputtering technique. The LSCO/AZO heterojunction was obtained by stacking the p-type LSCO thin film on the annealed n-type AZO thin film under different Ar: O2 sputter gas ratio atmosphere. The thickness of LSCO and AZO thin films are about 400 nm and 500 nm, respectively. Good crystalline match between LSCO and AZO films was observed from the SEM and XRD analysis. The heterojunction diode clearly demonstrated rectifying behavior in the range of ?8 to +8 V in reverse shape. The turn-on voltage of the diodes is obtained around 1.5 V and is in agreement with the value obtained from the difference in the work functions of LSCO and AZO. The band structure of the heterojunction was proposed based on the results of analysis. 相似文献
38.
We have examined the surface characteristics of Ag‐doped Au nanoparticles (below 5 mol% of Ag) by means of the surface‐enhanced Raman scattering (SERS) of 2,6‐dimethylphenylisocyanide (2,6‐DMPI) and 4‐nitrobenzenethiol (4‐NBT). When Ag was added to Au to form ∼35‐nm‐sized alloy nanoparticles, the surface plasmon resonance band was blue‐shifted linearly from 523 to 517 nm in proportion to the content of Ag up to 5%. In the SERS spectra of 2,6‐DMPI, the N‐C stretching peak also shifted almost linearly from 2184 to 2174 cm−1 when the Ag content was 5 mol% or less; the peak then remained the same as that of the pure Ag film. The potential variation of the SERS spectrum of 2,6‐DMPI in an electrochemical environment, as well as the effect of organic vapor, also showed a similar tendency. From the SERS of 4‐NBT, we confirmed the occurrence of a surface‐induced photoreaction converting 4‐NBT to 4‐aminobenzenethiol, when Ag was added to Au to form alloy nanoparticles. The photoreaction induction ability also increased linearly with the Ag content, reaching a plateau level at 5 mol% of Ag. All these observations suggest that the surface content of Ag should increase almost linearly as a function of the overall mole fraction of Ag and, once the Au/Ag nanoparticles reach 5 mol% of Ag, their surfaces are fully covered with Ag, showing the same surface characteristics of pure Ag nanoparticles. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
39.
Stevenson NR Schubank RB Shin YM Amaudruz P Delheij PP Healey DC Jennings BK Ottewell DF Sheffer G Smith GR Wait GD Brack JT Feltham A Hanna M Johnson RR Rozon FM Sossi V Vetterli D Weber P Grion N Rui R Kohler M Ristinen RA Mathie EL Tacik R Yeomans M Gossett CA Wagner GJ 《Physical review letters》1990,65(16):1987-1990
40.
M. Gutfleisch D.I. Shin T. Dreier P.M. Danehy 《Applied physics. B, Lasers and optics》2000,71(5):673-680
Laser-induced thermal gratings (LITG) were generated in mixtures of ethylene and ammonia in nitrogen using mid-infrared laser
radiation from a grating-tuned, low-pressure, pulsed (5 ms pulse width) CO2 laser, and read out with a continuous wave Nd:YLF laser. The LITG signal intensity was measured as a function of pressure
(0.1–2 MPa) and temperature (300–800 K, at 0.1 and 1 MPa) by tuning the laser to the accidental coincidences of the 10P(14)
and 10R(6) emission lines with molecular absorption transitions of C2H4 and NH3, respectively. Comparisons are made with theoretical predictions for the grating efficiency from a simple thermalization
model. A theoretical comparison of the temporal LITG signal response for three excitation pulse shapes – a delta function,
a realistic pulse, and a square wave is presented. Furthermore, it is shown that for NH3, most of the decrease of the LITG signal intensity with increasing temperature is due to the corresponding decrease in fractional
molecular absorption of the pump beam radiation. The diagnostic capabilities of the mid-infrared LITG experiment is demonstrated
for spatially resolved ethylene measurements with long laser pulses in a premixed stoichiometric CH4–air flame at atmospheric pressure.
Received: 17 March 2000 / Revised version: 23 March 2000 / Published online: 13 September 2000 相似文献