全文获取类型
收费全文 | 375篇 |
免费 | 30篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 10篇 |
综合类 | 2篇 |
化学工业 | 87篇 |
金属工艺 | 9篇 |
机械仪表 | 25篇 |
建筑科学 | 26篇 |
矿业工程 | 1篇 |
能源动力 | 22篇 |
轻工业 | 32篇 |
水利工程 | 5篇 |
石油天然气 | 3篇 |
武器工业 | 2篇 |
无线电 | 42篇 |
一般工业技术 | 83篇 |
冶金工业 | 13篇 |
原子能技术 | 2篇 |
自动化技术 | 52篇 |
出版年
2024年 | 4篇 |
2023年 | 12篇 |
2022年 | 17篇 |
2021年 | 31篇 |
2020年 | 12篇 |
2019年 | 25篇 |
2018年 | 22篇 |
2017年 | 12篇 |
2016年 | 23篇 |
2015年 | 14篇 |
2014年 | 20篇 |
2013年 | 38篇 |
2012年 | 28篇 |
2011年 | 21篇 |
2010年 | 23篇 |
2009年 | 18篇 |
2008年 | 19篇 |
2007年 | 20篇 |
2006年 | 15篇 |
2005年 | 8篇 |
2004年 | 4篇 |
2003年 | 3篇 |
2002年 | 7篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1995年 | 2篇 |
1993年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1986年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有416条查询结果,搜索用时 0 毫秒
51.
Qing Zhang Sinan Deng Jinlin Liu Xiaoxia Zhong Jie He Xianfeng Chen Bowen Feng Yanfei Chen Kostya Ostrikov 《Advanced functional materials》2019,29(5)
Folic acid, due to its high affinity toward folate receptors (FR), is recognized as one of the most promising cancer targeting vectors. However, the inherent defects of low water solubility (1.6 µg mL?1), high sensitivity toward photo‐bleaching, low fluorescent quantum yields (QYs, <0.5%) seriously limit its practical application. Herein, ultrastable, highly luminescent graphene quantum dots (GQDs) that selectively target diverse cancer cells are prepared and tested. The new GQDs present step changes compared to common folic acid through an ≈6250 times increase in water solubility (to ≈10 mg mL?1), more than 150 times in QYs (up to ≈77%), while maintaining luminescence stability up to 98% when subjected to UV, visible light, and heating over 360 min. It is shown that the suppression of nonradiative transitions by amino groups pyrolyzed from pterin plays a key role in the mechanism of high QYs and excellent stability. The functional groups that are likely responsible for the selective targeting of cancer cells with different levels of folate receptor expression on the surface are identified. Collectively with these promising properties, the new functional graphene quantum dots may open a new avenue for cancer diagnosis, drug delivery, and therapies. 相似文献
52.
Yaseen Mohammed Ali Abass A. K. Abdulsatar Sinan M. 《Wireless Personal Communications》2021,116(1):381-381
Wireless Personal Communications - The names of the second and third authors in the initial online publication were not correctly typeset. The original article has been corrected. 相似文献
53.
Xiaoping Pang Jin Chen Sinan H. Hussain 《Journal of Mechanical Science and Technology》2013,27(12):3693-3701
This paper is focused on using GA genetic algorithm to find the optimal performance with respect to shape optimization in three dimensions for the hydrodynamic journal bearing. The mathematical model for film thickness was drawn using Fourier series function and axial waviness value ( $\bar \Delta $ ) D to represent the journal bearing in circumferential and axial direction, respectively. The objective was then to determine the Fourier coefficients and axial waviness value ( $\bar \Delta $ ) D that maximized the load capacity subjected to a given set of constraint. Optimized results show that the presence of cos wave in axial direction, with a positive dimensionless amplitude (+A) and waviness number m = 0.633, improves the load capacity by (8–10) % over the cylindrical plain bearing with the same arbitrary shape and size; in general, the increasing order of Fourier series (n), an axial dimensionless amplitude and L/D ratio cause the change in load capacity to become more evident. 相似文献
54.
Esra Feyzioğlu Demir Meryem Koruyucu Gökhan Kök Yeşim Salman Sinan Akgöl 《分离科学与技术》2018,53(15):2365-2375
The aim of this work is to synthesize the original, new polymeric nanoparticles for concanavalin A (Con A) purification. Nanoparticles were synthesized by surfactant free emulsion polymerization. In the polymerization prosedure, 1-O-(2′-hydroxy-3′-acryloyloxypropyl)-2,3:5,6-di-O-isopropylidene-α-D-mannofuranose (Man-OPA) was used as co-monomer and 2-hydroxyethylmethacrylate (HEMA) was used as a monomer. Man-OPA was characterized by Fourier Transform Infrared Spectroscopy (FTIR), nuclear magnetic resonance and elemental analysis techniques. Poly(HEMA-Man-OPA) nanoparticles were characterized by scanning electron microscopy, FTIR and Zeta Sizer. In adsorption?desorption experiments, maximum Con A adsorption capacity of poly(HEMA-Man-OPA) nanoparticles was found 630.6 mg/g nanoparticle (pH 7.5, 1.0 mg/mL). Adsorption?desorption experiments were repeated in four times. According to results, these nanoparticles could be used several times without significant decrease in Con A adsorption capacity. 相似文献
55.
Bharath Natarajan Ajay Krishnamurthy Xin Qin Caglar D. Emiroglu Amanda Forster E. Johan Foster Christoph Weder Douglas M. Fox Sinan Keten Jan Obrzut Jeffrey W. Gilman 《Advanced functional materials》2018,28(26)
Most attempts to emulate the mechanical properties of strong and tough natural composites using helicoidal films of wood‐derived cellulose nanocrystals (w‐CNCs) fall short in mechanical performance due to the limited shear transfer ability between the w‐CNCs. This shortcoming is ascribed to the small w‐CNC‐w‐CNC overlap lengths that lower the shear transfer efficiency. Herein, we present a simple strategy to fabricate superior helicoidal CNC films with mechanical properties that rival those of the best natural materials and are some of the best reported for photonic CNC materials thus far. Assembling the short w‐CNCs with a minority fraction of high aspect ratio CNCs derived from tunicates (t‐CNCs), we report remarkable simultaneous enhancement of all in‐plane mechanical properties and out‐of‐plane flexibility. The important role of t‐CNCs is revealed by coarse grained molecular dynamics simulations where the property enhancement are due to increased interaction lengths and the activation of additional toughening mechanisms. At t‐CNC contents greater than 5% by mass the mixed films also display UV reflecting behaviour. These damage tolerant optically active materials hold great promise for application as protective coatings. More broadly, we expect the strategy of using length‐bidispersity to be adaptable to mechanically enhancing other matrix‐free nanoparticle ensembles. 相似文献
56.
Interfacial adhesion is a major concern with respect to successful performance of thin polymer films in developing new thin-film processes. Micro-indentation was used to induce interfacial delamination of polytetrafluoroethylene (PTFE) films deposited on glass substrates using hot filament chemical vapour deposition (HFCVD). Film thickness (1, 2, 3, 5, 10 µm) and indentation load (0.5, 0.75, 1, 2, 3 N) effects on the delamination diameter were investigated. A three-dimensional finite element model using shear material failure criterion and cohesive zone model (CZM) was developed to simulate the delamination. A normalized load–delamination radius relationship was obtained to evaluate the interfacial fracture toughness. The experimental observations showed that the delamination diameter depends on film thickness and indentation load. The numerical simulation indicates the delamination diameter depends on film thickness, material properties, and indentation force. The predictions of interfacial fracture toughness for 5- and 10-µm PTFE films are much smaller than those values using Rosenfeld et al.’s equation, which excludes the energy spent during the penetration. 相似文献
57.
Atmospheric particulate matter (PM) fractions (PM(10) and PM(2.5)) were sampled concurrently between June 2004 and May 2005 at two sites (urban and suburban) in Izmir, Turkey. The elemental composition of PM (Al, Ba, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sr, V, and Zn) was determined using inductively coupled plasma-optical emission spectrometer. Elemental compositions of several PM sources were also characterized. Positive matrix factorization (PMF) and chemical mass balance modeling (CMB) were applied to determine the PM sources and their contributions to air concentrations. The major contributors to PM were fossil fuel burning, traffic emissions, mineral industries and marine salt according to the PMF results. However, undetermined parts were more than 40%. On the other hand, the contributions to PM could be determined completely by CMB, and the dominant contributor was traffic with >70% at the two sites. Fossil fuel burning, mineral industries, marine salt and natural gas-fired power plant were the minor contributors. 相似文献
58.
In biology, structural design and materials engineering is unified through formation of hierarchical features with atomic
resolution, from nano to macro. Three molecular building blocks are particularly prevalent in all structural protein materials:
alpha helices (AHs), beta-sheets (BSs) and tropocollagen (TC). In this article we present a comparative study of these three
key building blocks by focusing on their mechanical signatures, based on results from full-atomistic simulation studies. We
find that each of the basic structures is associated with a characteristic material behavior: AH protein domains provide resilience
at large deformation through energy dissipation at low force levels, BS protein domains provide great strength under shear
loading, and tropocollagen molecules provide large elasticity for deformation recovery. This suggests that AHs, BSs, and TC
molecules have mutually exclusive mechanical signatures. We correlate each of these basic properties with the molecule’s structure
and the associated fundamental rupture mechanisms. Our study may enable the use of abundant protein building blocks in nanoengineered
materials, and may provide critical insight into basic biological mechanisms for bio-inspired nanotechnologies. The transfer
towards the design of novel nanostructures could lead to new multifunctional and mechanically active, tunable, and changeable
materials. 相似文献
59.
Frictional and durability characteristics of 1-µm-thick polytetrafluoroethylene (PTFE) films deposited by hot filament chemical vapor deposition on aluminum substrates were investigated. A universal microtribotester was used to examine the frictional and durability properties using the ball-on-plate and ball-on-disk configurations, respectively. Effects of normal force (2.5, 5, 10, 15 N), sliding speed (0.1, 1, 5 mm/s), and surface roughness of the aluminum substrate (Ra = 0.01, 0.57, 1.28, 2.34 µm) on the coefficient of friction (COF) and the effects of normal force (2.5, 5 N), sliding speed (0.42, 4.19 mm/s), and surface roughness on the durability were investigated. It was shown that the COF of the PTFE-coated interface increases with increasing surface roughness or sliding speed. The COF depends on the normal force to a lesser extent than the other two parameters. The medium-level, O(0.5 µm), roughness of the substrate provides the longest durability, whereas the smoothest or very rough surface provides shorter durability. Analysis of variance (ANOVA) indicates that the surface roughness has the most significant effect on the COF and durability. In the case of a smooth interface, a relationship between COF, sliding speed, and normal force can be predicted. Results indicate an optimal surface roughness for improving durability. 相似文献
60.