全文获取类型
收费全文 | 2955篇 |
免费 | 102篇 |
国内免费 | 23篇 |
专业分类
化学 | 2141篇 |
晶体学 | 37篇 |
力学 | 90篇 |
综合类 | 3篇 |
数学 | 221篇 |
物理学 | 588篇 |
出版年
2024年 | 23篇 |
2023年 | 41篇 |
2022年 | 151篇 |
2021年 | 156篇 |
2020年 | 75篇 |
2019年 | 103篇 |
2018年 | 84篇 |
2017年 | 74篇 |
2016年 | 147篇 |
2015年 | 99篇 |
2014年 | 116篇 |
2013年 | 206篇 |
2012年 | 226篇 |
2011年 | 224篇 |
2010年 | 120篇 |
2009年 | 113篇 |
2008年 | 135篇 |
2007年 | 126篇 |
2006年 | 127篇 |
2005年 | 119篇 |
2004年 | 89篇 |
2003年 | 84篇 |
2002年 | 52篇 |
2001年 | 27篇 |
2000年 | 22篇 |
1999年 | 20篇 |
1998年 | 15篇 |
1997年 | 16篇 |
1996年 | 16篇 |
1995年 | 9篇 |
1994年 | 18篇 |
1993年 | 15篇 |
1992年 | 16篇 |
1991年 | 13篇 |
1990年 | 13篇 |
1989年 | 11篇 |
1988年 | 11篇 |
1987年 | 12篇 |
1986年 | 13篇 |
1985年 | 14篇 |
1984年 | 15篇 |
1983年 | 12篇 |
1982年 | 16篇 |
1981年 | 20篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1977年 | 10篇 |
1976年 | 7篇 |
1962年 | 3篇 |
排序方式: 共有3080条查询结果,搜索用时 0 毫秒
81.
Riju Khandaker M. Kamruzzaman M. Afrose R. Rahman M. Khan M. K. R. Liton M. N. H. Helal M. A. Anam T. K. Rahman M. M. 《Crystallography Reports》2020,65(6):968-979
Crystallography Reports - Transition metals doped FeS2 thin films are promising materials for optoelectronics, energy saving and storage applications. This is a first time report on the... 相似文献
82.
83.
Md Khairul Islam Ivan Lozada Lawag Tomislav Sostaric Edie Ulrich Danny Ulrich Terrence Dewar Lee Yong Lim Cornelia Locher 《Molecules (Basel, Switzerland)》2022,27(7)
Despite its cultural and nutritional importance for local Aboriginal people, the unusual insect honey produced by Western Australian honeypot ant (Camponotus inflatus) has to date been rarely investigated. This study reports on the honey’s physicochemical properties, its total phenolic, major sugars and 5-hydroxymethylfurfural contents, and its antioxidant activities. The honey’s color value is 467.63 mAU/63.39 mm Pfund, it has a pH of 3.85, and its electric conductivity is 449.71 µSiemens/cm. Its Brix value is 67.00, corresponding to a 33% moisture content. The total phenolics content is 19.62 mg gallic acid equivalent/100 g honey. Its antioxidant activity measured using the DPPH* (2,2-diphenyl-1-picrylhydrazyl) and FRAP (ferric reducing–antioxidant power) assays is 1367.67 µmol Trolox/kg and 3.52 mmol Fe+2/kg honey, respectively. Major sugars in the honey are glucose and fructose, with a fructose-to-glucose ratio of 0.85. Additionally, unidentified sugar was found in minor quantities. 相似文献
84.
M. Sahedur Rahman 《Mikrochimica acta》2001,137(3-4):203-207
A sensitive and fairly selective quenchofluorimetric method for the determination of mercury ultra-trace with murexide (ammonium
purpurate) has been developed. The method is based on the instantaneous quenching action of the metal-ion upon the native
fluorescence of murexide [λex(max) = 360 nm; λem(max) = 445 nm] in the optimum pH range of 5.8 to 6.6 at room temperature (25±0.5) °C. The fluorescence quenching is collinear
in the range of 5 μg/L to 100 μg/L mercury. The developed method is very precise and accurate (RSD = 2.2% for 11 determination
of 50 μg/L Hg(II). Large excesses of more than 50 cations, anions and complexing agents were found to have no interference.
The developed method was successfully tested over synthetic mixtures of various compositions, certified reference materials
and factory effluents.
Received November 16, 1999. Revision March 30, 2001. 相似文献
85.
Organic perovskite has potential to replace organic dye as light absorber in solar cell since it possesses better optical absorption in visible region than organic dye. This work is concerned with the investigation of the influence of CH3NH3PbI3 perovskite dipping time on the performance of perovskite-sensitized solar cell (PSSC). The effect of the dipping time on the morphology and photoluminescence of the sample has also been investigated. It was found that the device achieved a power conversion efficiency (PCE) as high as 5.57 ± 0.4% at the optimum dipping time of 4 h. The highest PCE is due to the highest IPCE, lowest Rct and the longest carrier lifetime (τ). 相似文献
86.
The presence of heavy metals in water bodies is linked to the increasing number of industries and populations. This has serious consequences for the quality of human health and the environment. In accordance with this issue, water and wastewater treatment technologies including ion exchange, chemical extraction, and hydrolysis should be conducted as a first water purification stage. However, the sequestration of these toxic substances tends to be expensive, especially for large scale treatment methods that require tedious control and have limited efficiency. Therefore, adsorption methods using adsorbents derived from biomass represent a promising alternative due to their great efficiency and abundance. Algal and seaweed biomass has appeared as a sustainable solution for environmentally friendly adsorbent production. This review further discusses recent developments in the use of algal and seaweed biomass as potential sorbent for heavy metal bioremediation. In addition, relevant aspects like metal toxicity, adsorption mechanism, and parameters affecting the completion of adsorption process are also highlighted. Overall, the critical conclusion drawn is that algae and seaweed biomass can be used to sustainably eliminate heavy metals from wastewater. 相似文献
87.
Md. Mominur Rahman Md. Rezaul Islam Sheikh Shohag Md. Emon Hossain Md. Saidur Rahaman Fahadul Islam Muniruddin Ahmed Saikat Mitra Mayeen Uddin Khandaker Abubakr M. Idris Kumarappan Chidambaram Talha Bin Emran Simona Cavalu 《Molecules (Basel, Switzerland)》2022,27(5)
Obesity and diabetes are the most demanding health problems today, and their prevalence, as well as comorbidities, is on the rise all over the world. As time goes on, both are becoming big issues that have a big impact on people’s lives. Diabetes is a metabolic and endocrine illness set apart by hyperglycemia and glucose narrow-mindedness because of insulin opposition. Heftiness is a typical, complex, and developing overall wellbeing worry that has for quite some time been connected to significant medical issues in individuals, all things considered. Because of the wide variety and low adverse effects, herbal products are an important hotspot for drug development. Synthetic compounds are not structurally diverse and lack drug-likeness properties. Thus, it is basic to keep on exploring herbal products as possible wellsprings of novel drugs. We conducted this review of the literature by searching Scopus, Science Direct, Elsevier, PubMed, and Web of Science databases. From 1990 until October 2021, research reports, review articles, and original research articles in English are presented. It provides top to bottom data and an examination of plant-inferred compounds that might be utilized against heftiness or potentially hostile to diabetes treatments. Our expanded comprehension of the systems of activity of phytogenic compounds, as an extra examination, could prompt the advancement of remedial methodologies for metabolic diseases. In clinical trials, a huge number of these food kinds or restorative plants, as well as their bioactive compounds, have been shown to be beneficial in the treatment of obesity. 相似文献
88.
We investigate transverse electromagnetic waves propagating in a plasma influenced by the gravitational field of the Reissner–Nordström black hole. Applying 3+1 spacetime split we reformulate the relativistic two-fluid equations to take account of gravitational effects due to the event horizon and describe the set of simultaneous linear equations for the perturbations. Using a local approximation we investigate the one-dimensional radial propagation of Alfvén and high frequency electromagnetic waves. We derive the dispersion relation for these waves and solve it for the wave number k numerically. 相似文献
89.
90.
In an erbium-doped fiber amplifier(EDFA), erbium ions act as a three-level system. Therefore, much higher pump energy is required to achieve the population inversion in an erbium-doped fiber(EDF). This higher pump energy requirement complicates the efficient design of an EDFA. However, efficient use of the pump power can improve the EDFA performance. The improved performance of an EDFA can be obtained by reducing the doping radius of the EDF. A smaller doping radius increases pump–dopant interactions and subsequently increases the pump–photon conversion efficiency. Decreasing the doping radius allows a larger proportion of dopant ions,which are concentrated near the core, to interact with the highest pump intensity. However, decreasing the doping radius beyond a certain limit will bring the dopant ions much closer and introduce detrimental ion–ion interaction effects. In this Letter, we show that an optimal doping radius in an EDF can provide the best gain performance. Moreover, we have simulated the well-known numerical aperture effects on EDFA gain performance to support our claim. 相似文献