全文获取类型
收费全文 | 5926篇 |
免费 | 198篇 |
国内免费 | 53篇 |
专业分类
化学 | 4420篇 |
晶体学 | 42篇 |
力学 | 219篇 |
综合类 | 2篇 |
数学 | 817篇 |
物理学 | 677篇 |
出版年
2024年 | 11篇 |
2023年 | 62篇 |
2022年 | 309篇 |
2021年 | 310篇 |
2020年 | 210篇 |
2019年 | 234篇 |
2018年 | 221篇 |
2017年 | 172篇 |
2016年 | 301篇 |
2015年 | 203篇 |
2014年 | 215篇 |
2013年 | 535篇 |
2012年 | 366篇 |
2011年 | 390篇 |
2010年 | 242篇 |
2009年 | 207篇 |
2008年 | 263篇 |
2007年 | 265篇 |
2006年 | 214篇 |
2005年 | 185篇 |
2004年 | 168篇 |
2003年 | 144篇 |
2002年 | 146篇 |
2001年 | 56篇 |
2000年 | 64篇 |
1999年 | 47篇 |
1998年 | 32篇 |
1997年 | 44篇 |
1996年 | 40篇 |
1995年 | 33篇 |
1994年 | 39篇 |
1993年 | 32篇 |
1992年 | 36篇 |
1991年 | 31篇 |
1990年 | 44篇 |
1989年 | 26篇 |
1988年 | 22篇 |
1987年 | 26篇 |
1986年 | 27篇 |
1985年 | 32篇 |
1984年 | 19篇 |
1983年 | 17篇 |
1982年 | 25篇 |
1981年 | 20篇 |
1980年 | 14篇 |
1979年 | 16篇 |
1978年 | 11篇 |
1977年 | 12篇 |
1976年 | 10篇 |
1975年 | 6篇 |
排序方式: 共有6177条查询结果,搜索用时 73 毫秒
131.
Ghommem Mehdi Najar Fehmi Arabi Mohamed Abdel-Rahman Eihab Yavuz Mustafa 《Nonlinear dynamics》2020,101(1):271-291
Nonlinear Dynamics - We present a unified model of electrostatic sensors comprising cantilever microbeam resonators in fluid media. The model couples Euler–Bernoulli beam equation to the... 相似文献
132.
133.
Zaki Nadia G. Mahmoud Walaa H. El Kerdawy Ahmed M. Abdallah Abanoub Mosaad Mohamed Gehad G. 《Research on Chemical Intermediates》2020,46(6):3193-3216
Research on Chemical Intermediates - Reaction of cocaine (Cn) with Ln(III) chloride salts [where Ln?=?La(III), Er(III), and Yb(III)] afforded complexes of the [Ln(Cn)Cl(OH2)3].2Cl type... 相似文献
134.
Elhelw Mohamed El-Maghlany Wael M. 《Journal of Thermal Analysis and Calorimetry》2020,140(5):2563-2573
Journal of Thermal Analysis and Calorimetry - An evaluation of using a thermal storage system utilized with air conditioning cycle in Egypt is the main aim of this paper. This study includes the... 相似文献
135.
Journal of Solid State Electrochemistry - Remarkable selective analysis of biomolecules i.e., glucose and ascorbic acid on copper oxide facets was reported for the first time. The copper oxide... 相似文献
136.
Chaabane Ikram Guermazi Radhouane Hammami Mohamed 《Advances in Data Analysis and Classification》2020,14(3):677-745
Advances in Data Analysis and Classification - Several machine learning techniques assume that the number of objects in considered classes is approximately similar. Nevertheless, in real-world... 相似文献
137.
Ali El-Dissouky Eslam S. Abu-Elsoud Afaf Abdel Razik Mohamed K. Awad Hammed H.A.M. Hassan Amel F. Elhusseiny 《应用有机金属化学》2020,34(11):e5953
A series of nanometer-sized spherical sulfonamide imine ligands HL 1 -HL 5 and their copper and zinc complexes were synthesized and fully characterized based on elemental analyses, spectroscopic (UV/vis, FT-IR, NMR, EPR, SEM) studies, molar conductance and thermal analyses. Furthermore, computational studies of HL 1 -HL 5 were carried out by the DFT/B3LYP method. TD-DFT, HOMO and LUMO energy values, chemical hardness, electronegativity, electrophilic index, softness, and other parameters were calculated. Screening against several pathogenic microorganisms indicated that HL 1 exhibited high activity against the tested Gram-negative bacteria relative to other analogues and the inhibition activity is greater than the standard Gentamicin. Analogously, HL 2 exhibited high potent activity against the tested Gram-positive bacteria. Copper complexes exhibited a higher potent activity than zinc analogues. Noteworthy, inhibition activity of [Cu ( L 3 )(OAc)] complex is higher than that of the standard Ampicillin. [Cu ( L 2 )(OAc)] complex displayed a similar activity of the standard bactericides and fungicides in use. The complexes showed appreciated values of MIC against bacterial strains: B. subtilis (MIC = 0.4 μg / mL), E. coli and S. pneumonia (MIC = 1.95 μg / mL) and P. aeruginosa (MIC = 7.81 μg / mL). in vitro cytotoxic activities study proved that [Cu ( L 3 )(OAc)] complex exhibited appreciable activity versus (HEPG-2); IC50 = 4.8 μg/ml, while [Cu( L 2 )(OAc)] complex showed a high activity against (MCF-7); IC50 = 6.2 μg/ml. These results could be considered as new findings of promising antitumor candidates for experimental chemotherapy. 相似文献
138.
We optimized photocatalytic hydrogen production over TiO2-based photocatalyst by varying the dopant (nickel and copper oxide), thin film active area, nature and concentration of sacrificial agents, and light intensity in a photoelectrochemical (PEC) cell/dye-sensitized solar cell (DSSC). Various characterization techniques have been used to investigate the structural, morphological, optical, and PEC behavior of single and codoped TiO2. The TiO2 decorated with both Cu and Ni oxides with active area of 1 cm2 in a mixture of 5 vol % glycerol and 1 M KOH under light intensity of 100 mWcm?2 produced the maximum hydrogen of 338.4 μmol cm?2 for 2 h. The superior photocatalyst performance of this photocatalyst is attributed to its small crystallite size and large pore size, as confirmed by X-ray diffractometer, Transmission electron microscopy (TEM), and surface area of Brunauer-Emmet-Teller (SBET). The absorption edges of this photocatalyst had the highest red shift compared with single doped and pure TiO2 because of more indirect transitions of the photoexcited electrons, greater charge carrier separation, and lower recombination rate. The photoanode active area of 1 cm2 with better photocatalytic performance correlated with the number of defects and grain boundaries. Glycerol shifted the conduction band of the photocatalyst to more negative flat potential compared with others. Increasing the concentration of glycerol further than 5 vol% saturated the photocatalyst active sites, increased photooxidation intermediates of glycerol, and reduced the hydrogen production. The light intensity had the maximum impact on the hydrogen production and could strongly control the number of charge carriers in both the PEC cell and the DSSC. 相似文献
139.
Impact dampers have gained much research interest over the past decades that resulted in several analytical and experimental studies being conducted in that area. The main emphasis of such research was on developing and enhancing these popular passive control devices with an objective of decreasing the three parameters of contact forces, accelerations, and noise levels. To that end, the authors of this paper have developed a novel impact damper, called the Linear Particle Chain (LPC) impact damper, which mainly consists of a linear chain of spherical balls of varying sizes. The LPC impact damper was designed utilizing the kinetic energy of the primary system through placing, in the chain arrangement, a small-sized ball between each two large-sized balls. The concept of the LPC impact damper revolves around causing the small-sized ball to collide multiple times with the larger ones upon exciting the primary system. This action is believed to lead to the dissipation of part of the kinetic energy at each collision with the large balls. 相似文献
140.
A simple and rapid method for the simultaneous analysis of a ternary mixture containing trimethoprim, sulphamethoxazole and phenazopyridine hydrochloride is reported. The procedure consists of extraction in 0.1 M hydrochloric acid, filteration and measurement of the amplitudes of the third-derivative spectra at 242 and 276 nm and the absorbance at 450 nm for the determination of trimethoprim, sulphamethoxazole and phenazopyridine hydrochloride, respectively. Good linearity, accuracy, precision and selectivity were found, and the method is proposed for routine quality control purposes, even for the uniformity of contents test. 相似文献