全文获取类型
| 收费全文 | 283篇 |
| 免费 | 2篇 |
| 国内免费 | 1篇 |
专业分类
| 化学 | 95篇 |
| 晶体学 | 2篇 |
| 力学 | 13篇 |
| 数学 | 98篇 |
| 物理学 | 78篇 |
出版年
| 2024年 | 8篇 |
| 2023年 | 28篇 |
| 2022年 | 9篇 |
| 2021年 | 7篇 |
| 2020年 | 46篇 |
| 2019年 | 2篇 |
| 2018年 | 5篇 |
| 2017年 | 14篇 |
| 2016年 | 10篇 |
| 2014年 | 6篇 |
| 2013年 | 8篇 |
| 2012年 | 14篇 |
| 2011年 | 3篇 |
| 2010年 | 2篇 |
| 2009年 | 8篇 |
| 2008年 | 7篇 |
| 2007年 | 5篇 |
| 2006年 | 9篇 |
| 2005年 | 7篇 |
| 2004年 | 3篇 |
| 2001年 | 4篇 |
| 2000年 | 2篇 |
| 1999年 | 4篇 |
| 1998年 | 3篇 |
| 1996年 | 3篇 |
| 1992年 | 1篇 |
| 1991年 | 1篇 |
| 1989年 | 1篇 |
| 1988年 | 3篇 |
| 1987年 | 4篇 |
| 1986年 | 6篇 |
| 1985年 | 3篇 |
| 1981年 | 2篇 |
| 1980年 | 1篇 |
| 1978年 | 1篇 |
| 1975年 | 2篇 |
| 1974年 | 1篇 |
| 1973年 | 2篇 |
| 1972年 | 3篇 |
| 1971年 | 3篇 |
| 1970年 | 2篇 |
| 1968年 | 8篇 |
| 1967年 | 8篇 |
| 1966年 | 2篇 |
| 1965年 | 3篇 |
| 1964年 | 2篇 |
| 1962年 | 2篇 |
| 1960年 | 1篇 |
| 1959年 | 1篇 |
| 1951年 | 1篇 |
排序方式： 共有286条查询结果，搜索用时 15 毫秒
1.
D. R. K. Reddy R. L. Naidu V. U. M. Rao 《International Journal of Theoretical Physics》2008,47(6):1594-1599
It is shown that the axially symmetric thick domain walls and cosmic strings do not survive in the frame work of bimetric
theory of gravitation proposed by Rosen (Gen. Relativ. Gravit. 4:435, 1973). Hence vacuum models are presented and studied. 相似文献
2.
First-principles study of nanotubes within the tetragonal,hexagonal and dodecagonal cycle structures
A systematic study has been done on the structural and electronic properties of carbon, boron nitride and aluminum nitride nanotubes with structure consisting of periodically distributed tetragonal (T ≡A2X2), hexagonal (H ≡A3X3) and dodecagonal (D ≡A6X6) (AX=C2, BN, AlN) cycles. The method has been performed using first-principles calculations based on density functional theory (DFT). The optimized lattice parameters, density of state (DOS) curves and band structure of THD-NTs are obtained for (3, 0) and (0, 2) types. Our calculation results indicate that carbon nanotubes of these types (THD-CNTs) behave as a metallic, but the boron nitride nanotubes (THD-BNNTs) (with a band gap of around 4 eV) as well as aluminum nitride nanotubes (THD-AlNNTs) (with a band gap of around 2.6 eV) behave as an semiconductor. The inequality in number of atoms in different directions is affected on structures and diameters of nanotubes and their walls curvature. 相似文献
3.
4.
《印度化学会志》2023,100(6):101014
In this study, renewable, non-toxic, sulphur free bio-lubricants are synthesized as alternative for fossil fuels. We utilized a bio-derived 10-undecylenic acid (UDA) and pentaerythritol (PE) as raw materials to synthesize bio-lubricants by two-step chemical processes like esterification and followed by epoxidation reactions. And achieved a UDA-PE epoxide yielded 73.4%. The formation of UDA-PE ester and UDA-PE epoxide was confirmed by spectral analysis such as NMR (1H and 13C), FTIR and mass spectra, Physico-chemical and basic lubricant properties by standard American Society for Testing and Materials methods (ASTM). The results showed that the products of UDA-PE ester and UDA-PE epoxide had high viscosity index (262 and 200), good pour points (−29 °C to −15 °C), high flash points (296 °C and 301 °C) respectively and these met the ISO VG (International Organization for Standardization-Viscosity grade) 22 and 220 standard values. In general, both synthesized products are plausible to be employed as bio-lubricant in industrial application. 相似文献
5.
《印度化学会志》2023,100(8):101040
This work describes the degradation of synthetic water containing an elevated NAP concentration using the ultrasound and commercial Laccase enzyme (LT-100) by optimizing the system's parameters, such as ultrasound power, % duty cycle, enzyme concentration, and thermal environment. The established optimum condition obtained at a temperature of 40 °C, enzyme concentration 0.15% (w/v), ultrasound power 50 W, and 50% duty cycle of 10 min resulted in extreme NAP degradation of 96% in a time of 150 min. A noticeable improvement (67%) in the degradation of NAP was observed with enzyme and ultrasound than in the ultrasound only. An ultrasound-assisted enzymatic reaction showed a significant synergy effect under US irradiation, as evidenced by synergetic index values ranging from 0.873 to 1.841 for NAP. Radical scavenging experiments and LC/MS analysis revealed that hydroxylation, demethylation, and decarboxylation are the main chemical mechanisms involved in the degradation of NAP. The kinetic study showed that the degradation of NAP follows Michaelis Menten's kinetics having Vmax and Km as 3.3 μM/min and 18.3 μM, respectively. Low Km finding indicates there is much more enzyme compatibility towards the substrate. Furthermore, a toxicity study conducted on Naproxen revealed that the solutions obtained after the process exhibited approximately 80–85% less toxicity compared to the initial naproxen solutions. 相似文献
7.
翠绿料瓶罐玻璃颜色的深浅是由多种微量元素铁、铬、钴的浓度所决定的.在原子吸收光谱法测定这些微量元素时,要考虑基体产生的多种干扰.本法通过改进标准溶液的配制,克服了基体干扰,加快了样品的测定速度. 相似文献
9.
Effect of induced magnetic field is critical as a result of much controlled and focused on liquid flow is wanted in numerous modern and clinical procedures for example electromagnetic casting, drug delivery and cooling of nuclear reactors. Hence this investigation explains the behaviour of hybrid carbon nanotubes (CNTs) flow through slipped surface with induced magnetic field. Accumulation of SWCNTs (single wall) and MWCNTs (multi wall) nanomaterial with water base liquid is considered. Thermal performance is analyzed with regular heat source/sink effect. Chemical reaction and activation energy impacts are incorporated in mass equation. Solution of the similarity equations are obtained by adopting RKF45 method. Influence of flow variables are illustrated through graphs and computational values of drag force, Nusselt number and Sherwood number are presented in tables. It is noted that activation energy enhance the concentration field whereas opposite behaviour for reaction rate. Also induce magnetic field boosted with the larger values of magnetic Prandtl number. Furthermore it is observed that hybrid CNTs nanomaterial having higher rate of heating/cooling compare to singular CNTs nanomaterial. 相似文献
10.
This paper investigates microtubule thermodynamic properties dependence on gaussian thermal fluctuations using the Landau-Ginzburg-Wilson model. After solving the self-consistent equation for thermal fluctuations, we observed its increasing behavior as a function of temperature for different dimensionality 1, 2 and 3. Thermodynamic properties such as Shannon entropy, thermodynamic entropy, heat capacity and chemical potential have been computed. We found out that under thermal fluctuations, heat capacity and chemical potential exhibit negative values that can refer to the coexistence of first and second order phase transitions during MT dynamic instability. We also found that thermodynamic properties are highly affected at low temperatures. Moreover, thermodynamic entropy locally displays the conversion of the heat into work through the negentropy. We analyzed the behavior of the polarization according to fluctuations and found that thermal fluctuations modulate the polarization and depolarization of tubulin dimers which is very important in information processing in microtubules. 相似文献