全文获取类型
收费全文 | 579篇 |
免费 | 38篇 |
专业分类
电工技术 | 4篇 |
化学工业 | 314篇 |
金属工艺 | 3篇 |
机械仪表 | 11篇 |
建筑科学 | 22篇 |
矿业工程 | 1篇 |
能源动力 | 14篇 |
轻工业 | 84篇 |
水利工程 | 6篇 |
无线电 | 17篇 |
一般工业技术 | 86篇 |
冶金工业 | 7篇 |
原子能技术 | 2篇 |
自动化技术 | 46篇 |
出版年
2024年 | 1篇 |
2023年 | 25篇 |
2022年 | 118篇 |
2021年 | 107篇 |
2020年 | 33篇 |
2019年 | 25篇 |
2018年 | 32篇 |
2017年 | 22篇 |
2016年 | 24篇 |
2015年 | 22篇 |
2014年 | 23篇 |
2013年 | 33篇 |
2012年 | 20篇 |
2011年 | 31篇 |
2010年 | 17篇 |
2009年 | 19篇 |
2008年 | 15篇 |
2007年 | 8篇 |
2006年 | 11篇 |
2005年 | 6篇 |
2004年 | 5篇 |
2003年 | 5篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1984年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有617条查询结果,搜索用时 0 毫秒
101.
102.
Giulia Morettini Claudio Braccesi Filippo Cianetti 《Fatigue & Fracture of Engineering Materials & Structures》2019,42(4):827-837
In the literature there are many experimental results of multiaxial fatigue testing, usually generated by the combination of two or more cyclical loads. The cases in which samples are randomly stressed are rarer. Moreover, to generate particular stress states, the use of specific machinery for fatigue tests is usually required. For these reasons, the authors have created a particular geometry of specimens, which, when solicited by a single input of a random type, guarantees the creation of specific multiaxial stress states without using complex and costly instruments. The experimental tests were finally used for the validation of the multiaxial reduction method developed and currently utilized in the authors' design phase, though potentially used to verify all the other methodologies present in the literature. 相似文献
103.
Correlated basis function (CBF) perturbation theory and the formalism of cluster expansions have been recently employed to obtain an effective interaction from a nuclear Hamiltonian strongly constrained by phenomenology. We report the results of a study of the superfluid gap in pure neutron matter, associated with the formation of Cooper pairs in the \(^1S_0\) channel. The calculations have been carried out using an improved version of the CBF effective interaction, in which three-nucleon forces are taken into account using a microscopic model. Our results show that a non-vanishing superfluid gap develops at densities in the range \(2 \times 10^{-4} \lesssim \rho /\rho _0 \lesssim 0.1\), where \(\rho _0 = 2.8 \times 10^{14}~\mathrm{g~cm}^{-3}\) is the equilibrium density of isospin-symmetric nuclear matter, corresponding mainly to the neutron-star inner crust. 相似文献
104.
Sanghyun Paek Peng Qin Yonghui Lee Kyung Taek Cho Peng Gao Giulia Grancini Emad Oveisi Paul Gratia Kasparas Rakstys Shaheen A. Al‐Muhtaseb Christian Ludwig Jaejung Ko Mohammad Khaja Nazeeruddin 《Advanced materials (Deerfield Beach, Fla.)》2017,29(35)
Molecularly engineered novel dopant‐free hole‐transporting materials for perovskite solar cells (PSCs) combined with mixed‐perovskite (FAPbI3)0.85(MAPbBr3)0.15 (MA: CH3NH3+, FA: NH=CHNH3+) that exhibit an excellent power conversion efficiency of 18.9% under AM 1.5 conditions are investigated. The mobilities of FA‐CN, and TPA‐CN are determined to be 1.2 × 10?4 cm2 V?1 s?1 and 1.1 × 10?4 cm2 V?1 s?1, respectively. Exceptional stability up to 500 h is measured with the PSC based on FA‐CN. Additionally, it is found that the maximum power output collected after 1300 h remained 65% of its initial value. This opens up new avenue for efficient and stable PSCs exploring new materials as alternatives to Spiro‐OMeTAD. 相似文献
105.
Yagmur Akdag Cayli Selma Sahin Francesca Buttini Anna Giulia Balducci Serena Montanari Imran Vural 《Drug development and industrial pharmacy》2017,43(8):1378-1389
Objective: This study aimed to design and characterize an inhalable dry powder of ciprofloxacin or levofloxacin combined with the mucolytics acetylcysteine and dornase alfa for the management of pulmonary infections in patients with cystic fibrosis.Methods: Ball milling, homogenization in isopropyl alcohol and spray drying processes were used to prepare dry powders for inhalation. Physico-chemical characteristics of the dry powders were assessed via thermogravimetric analysis, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry and scanning electron microscopy. The particle size distribution, dissolution rate and permeability across Calu-3 cell monolayers were analyzed. The aerodynamic parameters of dry powders were determined using the Andersen cascade impactor (ACI).Results: After the micronization process, the particle sizes of the raw materials significantly decreased. X-ray and DSC results indicated that although ciprofloxacin showed no changes in its crystal structure, the structure of levofloxacin became amorphous after the micronization process. FT-IR spectra exhibited the characteristic peaks for ciprofloxacin and levofloxacin in all formulations. The dissolution rates of micro-homogenized and spray-dried ciprofloxacin were higher than that of untreated ciprofloxacin. ACI results showed that all formulations had a mass median aerodynamic diameter less than 5?μm; however, levofloxacin microparticles showed higher respirability than ciprofloxacin powders did. The permeability of levofloxacin was higher than those of the ciprofloxacin formulations.Conclusion: Together, our study showed that these methods could suitably characterize antibiotic and mucolytic-containing dry powder inhalers. 相似文献
106.
107.
Vaz Isabela C. F. Macchi Carlos Eugenio Somoza Alberto Rocha Leandro S. R. Longo Elson Cabral Luis da Silva Edison Z. Simões Alexandre Zirpoli Zonta Giulia Malagù Cesare Desimone P. Mariela Ponce Miguel Adolfo Moura Francisco 《Journal of Materials Science: Materials in Electronics》2022,33(15):11632-11649
Journal of Materials Science: Materials in Electronics - This study reports the electrical properties of Nd-doped cerium oxide (CeO2) films synthesized by microwave assisted hydrothermal using a... 相似文献
108.
109.
Nanoporous Si as an efficient thermoelectric material 总被引:1,自引:0,他引:1
Room-temperature thermoelectric properties of n-type crystalline Si with periodically arranged nanometer-sized pores are computed using a combination of classical molecular dynamics for lattice thermal conductivity and ab initio density functional theory for electrical conductivity, Seebeck coefficient, and electronic contribution to the thermal conductivity. The electrical conductivity is found to decrease by a factor of 2-4, depending on doping levels, compared to that of bulk due to confinement. The Seebeck coefficient S yields a 2-fold increase for carrier concentrations less than 2 x 10(19) cm(-3), above which S remains closer to the bulk value. Combining these results with our calculations of lattice thermal conductivity, we predict the figure of merit ZT to increase by 2 orders of magnitude over that of bulk. This enhancement is due to the combination of the nanometer size of pores which greatly reduces the thermal conductivity and the ordered arrangement of pores which allows for only a moderate reduction in the power factor. We find that while alignment of pores is necessary to preserve power factor values comparable to those of bulk Si, a symmetric arrangement is not required. These findings indicate that nanoporous semiconductors with aligned pores may be highly attractive materials for thermoelectric applications. 相似文献
110.
Friddle RW Lemieux MC Cicero G Artyukhin AB Tsukruk VV Grossman JC Galli G Noy A 《Nature nanotechnology》2007,2(11):692-697
Carbon nanotubes display a consummate blend of materials properties that affect applications ranging from nanoelectronic circuits and biosensors to field emitters and membranes. These applications use the non-covalent interactions between the nanotubes and chemical functionalities, often involving a few molecules at a time. Despite their wide use, we still lack a fundamental understanding and molecular-level control of these interactions. We have used chemical force microscopy to measure the strength of the interactions of single chemical functional groups with the sidewalls of vapour-grown individual single-walled carbon nanotubes. Surprisingly, the interaction strength does not follow conventional trends of increasing polarity or hydrophobicity, and instead reflects the complex electronic interactions between the nanotube and the functional group. Ab initio calculations confirm the observed trends and predict binding force distributions for a single molecular contact that match the experimental results. Our analysis also reveals the important role of molecular linkage dynamics in determining interaction strength at the single functional group level. 相似文献