全文获取类型
收费全文 | 104145篇 |
免费 | 11408篇 |
国内免费 | 15418篇 |
专业分类
化学 | 73002篇 |
晶体学 | 2795篇 |
力学 | 3792篇 |
综合类 | 1428篇 |
数学 | 13816篇 |
物理学 | 36138篇 |
出版年
2023年 | 1294篇 |
2022年 | 1737篇 |
2021年 | 3317篇 |
2020年 | 3165篇 |
2019年 | 3037篇 |
2018年 | 2594篇 |
2017年 | 3296篇 |
2016年 | 3657篇 |
2015年 | 3271篇 |
2014年 | 4393篇 |
2013年 | 8647篇 |
2012年 | 6028篇 |
2011年 | 6575篇 |
2010年 | 5686篇 |
2009年 | 7135篇 |
2008年 | 7022篇 |
2007年 | 7388篇 |
2006年 | 6558篇 |
2005年 | 5237篇 |
2004年 | 5002篇 |
2003年 | 4396篇 |
2002年 | 3804篇 |
2001年 | 3253篇 |
2000年 | 2799篇 |
1999年 | 2283篇 |
1998年 | 2042篇 |
1997年 | 1674篇 |
1996年 | 1547篇 |
1995年 | 1548篇 |
1994年 | 1428篇 |
1993年 | 1265篇 |
1992年 | 1247篇 |
1991年 | 896篇 |
1990年 | 700篇 |
1989年 | 572篇 |
1988年 | 598篇 |
1987年 | 450篇 |
1986年 | 404篇 |
1985年 | 498篇 |
1984年 | 378篇 |
1983年 | 210篇 |
1982年 | 418篇 |
1981年 | 612篇 |
1980年 | 548篇 |
1979年 | 573篇 |
1978年 | 468篇 |
1977年 | 358篇 |
1976年 | 309篇 |
1974年 | 106篇 |
1973年 | 206篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
Herein, we report the controlled and direct fabrication of Cu2O/CuO thin film on the conductive nickel foam using electrodeposition route for the electrochemical reduction of carbon dioxide (CO2) to methanol. The electrocatalytic reduction was performed in CO2 saturated aqueous solution consisting of KHCO3, pyridine and HCl at room temperature. CO2 reduction was carried out at a constant potential of −1.3 V for 120 min to study the electrochemical performance of the prepared electrocatalysts. Cu2O/CuO shows better electrocatalytic activity with highest current density of 46 mA/cm2. The prepared catalyst can be an efficient and selective electrode for the production of methanol. 相似文献
992.
Hanen Khadhraoui Abdelhak Othmani Abdessalem Kouki Mouldi Zouaoui 《Electroanalysis》2021,33(1):152-159
In this work we report an easy and efficient way to fabricate nanostructured cobalt oxide (Co3O4) thin films as a non-enzymatic sensor for H2O2 detection. Co3O4 thin films were grown on ITO glass substrates via the sol-gel method and characterized with several techniques including X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and optical absorbance. The Co3O4 thin films’ performance regarding hydrogen peroxide detection was studied in a 0.1 M NaOH solution using two techniques, cyclic voltammetry (CV) and amperometry. The films exhibited a high sensitivity of 1450 μA.mM−1.cm−2, a wide linear range from 0.05 μM to 1.1 mM, and a very low detection limit of 18 nM. Likewise, the Co3O4 thin films produced showed an exceptional stability and a high selectivity. 相似文献
993.
In this paper, a novel improvement in the catalytic Fenton reaction system named MHACF-NH2-MIL-101(Cr) was constructed based on H2 and Pd/NH2-MIL-101(Cr). The improved system would result in an accelerated reduction in FeIII, and provide a continuous and fast degradation efficiency of the 10 mg L-1 4-chlorophenol which was the model contaminant by using only trace level FeII. The activity of Pd/NH2-MIL-101(Cr) decreased from 100% to about 35% gradually during the six consecutive reaction cycles of 18 h. That could be attributed to the irreversible structural damage of NH2-MIL-101(Cr). 相似文献
994.
Bekzat ABDIKADYR Alp KILI Onur ALEV Serkan BÜYÜKK
SE Zafer Ziya
ZTÜRK 《Turkish Journal of Chemistry》2021,45(2):295
Pristine and WO3 decorated TiO2 nanorods (NRs) were synthesised to investigate n-n-type heterojunction gas sensing properties. TiO2 NRs were fabricated via hydrothermal method on fluorine-doped tin oxide coated glass (FTO) substrates. Then, tungsten was sputtered on the TiO2 NRs and thermally oxidised to obtain WO3 nanoparticles. The heterostructure was characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy. Fabricated sensor devices were exposed to VOCs such as toluene, xylene, acetone and ethanol, and humidity at different operation temperatures. Experimental results demonstrated that the heterostructure has better sensor response toward ethanol at 200 °C. Enhanced sensing properties are attributed to the heterojunction formation by decorating TiO2 NRs with WO3. 相似文献
995.
《Journal of Saudi Chemical Society》2021,25(9):101318
A novel cellulose acetate-g-poly (2-acrylamido-2-methylpropane sulfonic acid-co- methyl methacrylate) copolymer was prepared via free radical polymerization for the first time. The chemical structure of the graft copolymer was confirmed using FT-IR, 1H NMR and EDX. The TGA and DSC investigated the thermal changes. Factors affecting the grafting process were studied and various grafting characteristic parameters such as grafting efficiency (%), grafting yield (%) and add-on value (%) were determined. Flexible membranes based on different graft copolymer compositions were fabricated by simple solution casting. Physicochemical properties including ion exchange capability (IEC), water uptake (WU) and proton conductivity (σ) were evaluated. These membranes demonstrated higher IEC, WU and conductivity than the pristine CA. The maximum proton conductivity of the CA-g-poly (2-acrylamido-2-methylpropane sulfonic acid-co- methyl methacrylate) copolymer membrane (68%; Add-on %) was found to be 6.44 × 10−3 S/cm compared with 0.035 × 10−3 S/cm of the pristine CA. Thus, the appropriate graft copolymer composition will allow fine-tuning of the physical characteristics and led to several potential applications, such as polyelectrolyte fuel cells membranes or biodiesel production. 相似文献
996.
997.
The structure, size, and main physicochemical characteristics of the SARS-CoV-2 virion with the spike transmembrane protein corona were discussed. Using these data, diffusion coefficients of the virion in aqueous media and in air were calculated. The structure and dimensions of the spike protein derived from molecular dynamic modeling and thorough cryo-electron microscopy measurements were also analyzed. The charge distribution over the molecule was calculated and shown to be largely heterogeneous. Although the stalk part is negatively charged, the top part of the spike molecule, especially the receptor binding domain, remains positively charged for a broad range of pH. It is underlined that such a charge distribution promotes the spike corona stability and enhances the virion attachment to receptors and surfaces, mostly negatively charged. The review is completed by the analysis of experimental data pertinent to the spike protein adsorption at abiotic surfaces comprising nanoparticle carrier particles. It is argued that these theoretical and experimental data can be used for developing quantitative models of virus attachment to surfaces, facilitating adequate analysis of future experimental results. 相似文献
998.
In March 2020, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-based infections were declared ‘COVID-19 pandemic’ by the World Health Organization. Pandemic raised the necessity to design and develop genuine and sensitive tests for precise specific SARS-CoV-2 infections detection. Nanotechnological methods offer new ways to fight COVID-19. Nanomaterials are ideal for unique sensor platforms because of their chemically versatile properties and they are easy to manufacture. In this context, selected examples for integrating nanomaterials and distinct biosensor platforms are given to detect SARS-CoV-2 biological materials and COVID-19 biomarkers, giving researchers and scientists more goals and a better forecast to design more relevant and novel sensor arrays for COVID-19 diagnosis. 相似文献
999.
The COVID-19 pandemic had a major impact on life in 2020 and 2021. One method of transmission occurs when the causative virus, SARS-CoV-2, contaminates solids. Understanding and controlling the interaction with solids is thus potentially important for limiting the spread of the disease. We review work that describes the prevalence of the virus on common objects, the longevity of the virus on solids, and surface coatings that are designed to inactivate the virus. Engineered coatings have already succeeded in producing a large reduction in viral infectivity from surfaces. We also review work describing inactivation on facemasks and clothing and discuss probable mechanisms of inactivation of the virus at surfaces. 相似文献
1000.