全文获取类型
收费全文 | 222篇 |
免费 | 17篇 |
专业分类
化学 | 76篇 |
数学 | 18篇 |
物理学 | 145篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 2篇 |
2020年 | 5篇 |
2019年 | 9篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 7篇 |
2015年 | 5篇 |
2014年 | 15篇 |
2013年 | 20篇 |
2012年 | 28篇 |
2011年 | 30篇 |
2010年 | 26篇 |
2009年 | 12篇 |
2008年 | 16篇 |
2007年 | 10篇 |
2006年 | 5篇 |
2005年 | 5篇 |
2004年 | 5篇 |
2003年 | 5篇 |
2001年 | 1篇 |
1998年 | 1篇 |
1995年 | 2篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1984年 | 1篇 |
1981年 | 2篇 |
1978年 | 2篇 |
1976年 | 2篇 |
排序方式: 共有239条查询结果,搜索用时 15 毫秒
1.
Harun Muhammad Arif Bin Gunnasegaran Prem A./L. Sidik Nor Azwadi Che Beriache M’hamed Ghaderian Javad 《Journal of Thermal Analysis and Calorimetry》2021,144(4):1435-1449
Journal of Thermal Analysis and Calorimetry - High heat generation from electronic devices needs to cool down properly to prevent overheating. Loop heat pipe (LHP) is one of the excellent cooling... 相似文献
2.
The booming development of organometal halide perovskites in recent years has prompted the exploration of morphology‐control strategies to improve their performance in photovoltaic, photonic, and optoelectronic applications. However, the preparation of organometal halide perovskites with high hierarchical architecture is still highly challenging and a general morphology‐control method for various organometal halide perovskites has not been achieved. A mild and scalable method to prepare organometal halide perovskites in inverse opal morphology is presented that uses a polystyrene‐based artificial opal as hard template. Our method is flexible and compatible with different halides and organic ammonium compositions. Thus, the perovskite inverse opal maintains the advantage of straightforward structure and band gap engineering. Furthermore, optoelectronic investigations reveal that morphology exerted influence on the conducting nature of organometal halide perovskites. 相似文献
3.
4.
We demonstrate a switchable Q-switched and mode-locked erbium-doped fiber laser (EDFL) operating in the L-band region using the nonlinear polarization rotation effect. The switching operation is achieved by controlling intensity-dependent loss using a polarization controller. In Q-switching mode, the EDFL produces a pulse train with a repetition rate of 21.1 kHz, pulse width of 7.7 #s, and pulse energy of 13.6 nJ. The EDFL also generates a multi-wavelength comb with a very narrow and constant wavelength spacing of 0.045 nm and optical signal-to-noise ratio of at least l0 dB. During mode locking, the EDFL produces stretched pulses with 3-dB bandwidth of 26.2 nm, pulse width of 350 fs, repetition rate of 2.38 MHz, and pulse energy of 48.56 pJ. 相似文献
5.
Ratiometric fluorescent chemosensors based on the position of ring annulation of the naphthol–thiazole moiety for quantification of zinc ions in aqueous ethanol were synthesized and investigated. It was found that sensor 3 exhibited a remarkably large red shift of 140 nm in emission upon complexation with Zn2+. A TD-B3LYP/6-31G (d,p) calculation was performed to characterize the nature of the fluorescence behavior of sensor 3 upon Zn2+ complexation. The combination of experimental and computational analyses provides a more complete understanding of the molecular level origin of these unique photophysical properties of this type of chemosensor. 相似文献
6.
An efficient gain-flattened C-band optical amplifier is demonstrated using a hybrid configuration with a Zirconia-based Erbium-doped
fibre (Zr-EDF) and a semiconductor optical amplifier (SOA). The amplifier utilizes a two-stage structure with a midway isolator
to improve flat gain characteristic and reduce noise figure. At input signal power of −30 dBm, a flat gain of 28 dB is obtained
from wavelength region of 1530 to 1560 nm with gain variation of less than 4 dB. The noise figure is maintained below 11 dB
at the flat-gain region. This amplifier has the potential to be used in the high channel count dense wavelength division multiplexing
system due to its simplicity and compact design. 相似文献
7.
Dr. Yitao Dai Dr. Corentin Poidevin Dr. Cristina Ochoa-Hernández Prof. Dr. Alexander A. Auer Priv.-Doz. Dr. Harun Tüysüz 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(14):5837-5845
Direct selective oxidation of hydrocarbons to oxygenates by O2 is challenging. Catalysts are limited by the low activity and narrow application scope, and the main focus is on active C−H bonds at benzylic positions. In this work, stable, lead-free, Cs3Bi2Br9 halide perovskites are integrated within the pore channels of mesoporous SBA-15 silica and demonstrate their photocatalytic potentials for C−H bond activation. The composite photocatalysts can effectively oxidize hydrocarbons (C5 to C16 including aromatic and aliphatic alkanes) with a conversion rate up to 32900 μmol gcat−1 h−1 and excellent selectivity (>99 %) towards aldehydes and ketones under visible-light irradiation. Isotopic labeling, in situ spectroscopic studies, and DFT calculations reveal that well-dispersed small perovskite nanoparticles (2–5 nm) possess enhanced electron–hole separation and a close contact with hydrocarbons that facilitates C(sp3)−H bond activation by photoinduced charges. 相似文献
8.
A. A. Latif H. Ahmad N. A. Awang M. Z. Zulkifli C. H. Pua Z. A. Ghani S. W. Harun 《Laser Physics》2011,21(4):712-717
In this paper, a design of a High Power Tunable Fiber Laser (HP-TFL) in C-band region from 1536.7 to 1548.6 nm is set forth
with Erbium Doped Fibers (EDFs) being used as a seeding signal and a booster amplifier. With a 1 × 16 channels Arrayed Waveguide
Grating (AWG), this setup is capable of generating 16 different wavelengths with an average output power of 20.7 dBm. 相似文献
9.
Complex permittivity, complex permeability and microwave absorption properties of ferrite-paraffin polymer composites 总被引:1,自引:0,他引:1
Harun Bayrakdar 《Journal of magnetism and magnetic materials》2011,323(14):1882-1885
We have investigated the electromagnetic (EM) characteristics of CoxMn1−xFe2O4 spinel ferrite (where x=0.0, 0.5 and 1.0) nanoparticles (NPs)/paraffin nanocomposite material at 8-20 GHz. CoxMn1−xFe2O4 NPs have been synthesized by cetyltrimethylammonium assisted hydrothermal route using NaOH. A variation in complex dielectric permittivity and magnetic permeability at room temperature with frequency in the range 8-20 GHz has been studied. Particles showed phase purity and crystallinity in powder X-ray diffraction (XRD) analysis. At the same time, CoxMn1−xFe2O4 NPs demonstrated a spinel cubic structure from XRD results. A reflection loss of −46.60 dB was found at 10.5 GHz for an absorber thickness of 2 mm. CoxMn1−xFe2O4 may be attractive candidates for EM wave absorption materials. 相似文献
10.
Tobias Grewe Xiaohui Deng Dr. Harun Tüysüz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(25):7692-7697
A systematic study on the growth of Cr2O3 in three‐dimensional cubic ordered mesoporous silica (KIT‐6) and its replication through nanocasting is reported. By changing the loading time and amount of precursor, the size and shape of the obtained replica could be controlled to some extent. More interestingly, in contrast to previously published studies, when KIT‐6 with an aging temperature of 100 °C, which has a high degree of interconnectivity, was used as a hard template, a cubic ordered mesoporous Cr2O3 replica with an open uncoupled subframework structure and reduced symmetry was obtained. Formation of a replica with different symmetry and uncoupled subframework structure is not only related to the degree of interconnectivity of the parent, but also strongly depends on the type of metal oxide and its growth mechanism in the silica template. Nanocasting of Cr2O3 with a low loading results in a replica with monomodal pore size distribution that has same symmetry as the hard template, whereas increasing the loading amount alters the symmetry of the replica and yields a replica with bimodal distribution. 相似文献