全文获取类型
收费全文 | 1356篇 |
免费 | 57篇 |
国内免费 | 18篇 |
专业分类
化学 | 1030篇 |
晶体学 | 26篇 |
力学 | 48篇 |
数学 | 66篇 |
物理学 | 261篇 |
出版年
2024年 | 9篇 |
2023年 | 13篇 |
2022年 | 126篇 |
2021年 | 131篇 |
2020年 | 51篇 |
2019年 | 54篇 |
2018年 | 76篇 |
2017年 | 52篇 |
2016年 | 79篇 |
2015年 | 65篇 |
2014年 | 70篇 |
2013年 | 79篇 |
2012年 | 130篇 |
2011年 | 129篇 |
2010年 | 85篇 |
2009年 | 52篇 |
2008年 | 40篇 |
2007年 | 33篇 |
2006年 | 25篇 |
2005年 | 21篇 |
2004年 | 12篇 |
2003年 | 10篇 |
2002年 | 10篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 4篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1975年 | 2篇 |
1936年 | 1篇 |
1935年 | 1篇 |
1933年 | 1篇 |
排序方式: 共有1431条查询结果,搜索用时 15 毫秒
31.
Arshad Sadiqa Khan Majid Hussain Iqtadar 《International Journal of Theoretical Physics》2021,60(9):3631-3650
International Journal of Theoretical Physics - The use of digital contents has increased tremendously in this modern era. In fact, people spend more time on internet than ever which urged the... 相似文献
32.
Electrical field analysis of metal‐surface plasmon resonance using a biaxially strained Si substrate
Daisuke Kosemura Siti Norhidayah binti Che Mohd Yusoff Atsushi Ogura 《Journal of Raman spectroscopy : JRS》2014,45(6):414-417
Electrical field components of metal‐surface plasmon resonance were analyzed in detail. Both longitudinal optical (LO) and transverse optical (TO) phonon modes of a biaxially strained Si layer can be excited by surface‐enhanced Raman spectroscopy (SERS). The z to y polarization ratio in SERS measurements was calculated to be 0.78 using the intensity ratio of TO to LO phonon modes. The electrical field components of SERS were also calculated by the finite‐difference time‐domain method. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
33.
In the present work, Vickers microhardness measurements were carried out on different faces i.e. (1 0 0), (0 0 1) and (1 0 1) of ammonium dihydrogen phosphate (ADP) single crystals grown by slow evaporation solution technique at room temperature in the load ranging from 0.2 to 2 N. The obtained results show that the load independent hardness values are 0.8, 0.7 and 0.66 GPa, respectively at different faces of ADP crystal. From the crack length measurements, the fracture toughness values (Kc) was estimated using Evans and Anstis model and the present studies suggest that Evans model is more relevant when compared to Anstis model. The load variation of some mechanical properties viz. brittle index number (Bi) and yield strength (σy) for ADP have also been calculated for the first time. 相似文献
34.
Santos Regis C. Maia José R. da S. Abras Anuar Filgueiras Carlos A. L. 《Hyperfine Interactions》2002,142(3-4):495-501
Several novel tin(IV) adducts of amidines, [SnClPh3L], [SnCl2Ph2L] and [SnBr4L] {L=N,N-diphenylacetamidine (Hdpac) or N,N-diphenylbenzamidine (Hdpba)}, were prepared and investigated by Mössbauer spectroscopy which was an important tool for the elucidation of bonding and structural features. The resulting Mössbauer data also led to the conclusion that the tin(IV) centre for the adduct [SnClPh3L] is pentacoordinated in a trigonal bipyramidal arrangement and hexacoordinated for [SnCl2Ph2L] and [SnBr4L] in a geometric patterns of an octahedral. The amidines act as monodentate ligands to the metal centre for the former and bidentate for the latter. 相似文献
35.
High-performance oxide vertical-cavity surface-emitting (VCSEL) laser is fabricated, and its usefulness is demonstrated as a suitable transmitting light source at 850 nm operating wavelength for Gigabit Ethernet application. Utilization of barrier reduction layers reveals low-threshold current requirement for operation at high modulation bandwidth. The electrical and optical characteristics, measured from the fabricated VCSEL, are simulated for Gigabit Ethernet transmission. Data rates of 1.25 Gbps with a bit error rate of 10−11 are achieved by the use of a specific multimode network simulator. 相似文献
36.
Hassan Jafari Mohd Hasbullah Idris Ali Ourdjini Saeed Farahany Mohammed Rafiq Abdul Kadir 《Particle & Particle Systems Characterization》2012,29(4):263-272
Oxidation and melting behaviors of AZ91D granules throughout the in‐situ melting process using flux were investigated. The granules were heated under unprotected environment at four different temperatures between 650 and 800 °C, for the durations of 30 and 60 min. The products of heating process were characterized macroscopically and the oxides formed on the granules were examined using field emission scanning electron microscope, energy dispersive X‐ray spectroscopy and X‐ray diffraction analysis. Thermal analysis was used to reveal the response of the granules to heating during the in‐situ melting. The results showed that the granules experienced severe oxidation even in the presence of the flux, and significant amount of them changed to a powdered state due to oxidation and combustion, especially at 800 °C. It was discovered that the granules melted during heating; however, oxides formed on their surface encapsulated the molten metal and prevented the liquids from merging. The results also revealed that increasing heating temperature and time enhanced mold‐magnesium reaction resulted in the entrance of mold materials into the oxidation residues. 相似文献
37.
Mohd Jailani Mohd Nor Mohammad Hosseini Fouladi Ahmad Kamal Ariffin 《Applied Acoustics》2008,69(4):343-353
Sound quality is among the main factors that influence customers’ preference for choosing good automobile products. It all started more than 10 years ago and grows up so fast due to high competition in the automotive industries. A-weighted noise levels and sound power are usually utilised to measure the noise but they are not adequate to characterise the impact sound inside a car. The most popular approach to determine sound quality of a product is to define an annoyance or specific index, which involves both subjective and objective evaluations. Subjective and objective tests should be studied concurrently in order to determine the sound quality inside a passenger car. This approach is used in this paper to evaluate vehicle comfort index according to most frequently used sound quality metrics, namely; Zwicker loudness, sharpness, roughness and fluctuation strength. As a result researchers of different fields of automotive acoustics investigations can use this index according to the type of road (international road roughness) without any need to perform time-consuming jury tests. The metrics are correlated with jury test results that show which of them and how much has affected the acoustical comfort of the vehicle. The relation between road roughness and vehicle acoustical comfort index is another point of interest in this research. 相似文献
38.
Naved Azum Malik Abdul Rub Abdullah M. Asiri Mohd. Akram 《Russian Journal of Physical Chemistry B, Focus on Physics》2015,9(6):940-945
Aggregation behavior of cationic gemini (hexanediyl-1,5-bis(dimethylcettylammonium bromide) (16-5-16)) surfactant with conventional single chain surfactants cetyltrimethylammonium bromide (CTAB) and tetradecyltrimethylammonium bromide (TTAB) were studied with the help of fluorescence measurements. Fluorescence probe is a proficient technique for examining the surfactant-surfactant interaction and aggregation. The micelle aggregation number (N agg) was measured using steady-state fluorescence quenching method. The micelle aggregation numbers of binary combinations fall between those of constituent surfactants. The micropolarity (I 1/I 3), binding constant (K sv) and dielectric constant (D exp) of mixed systems were determined from the ratio of peaks intensity in the pyrene fluorescence spectrum. The I 1/I 3 values were found to be more than >1, showing more polar environment around pyrene in the mixed micelle as compared to the pure micelles. 相似文献
39.
40.