全文获取类型
收费全文 | 180789篇 |
免费 | 18755篇 |
国内免费 | 11519篇 |
专业分类
电工技术 | 15718篇 |
技术理论 | 10篇 |
综合类 | 21403篇 |
化学工业 | 21025篇 |
金属工艺 | 7775篇 |
机械仪表 | 12208篇 |
建筑科学 | 21947篇 |
矿业工程 | 8467篇 |
能源动力 | 7391篇 |
轻工业 | 10134篇 |
水利工程 | 7542篇 |
石油天然气 | 8806篇 |
武器工业 | 2251篇 |
无线电 | 13354篇 |
一般工业技术 | 22754篇 |
冶金工业 | 8149篇 |
原子能技术 | 3282篇 |
自动化技术 | 18847篇 |
出版年
2024年 | 756篇 |
2023年 | 2262篇 |
2022年 | 4546篇 |
2021年 | 5316篇 |
2020年 | 5705篇 |
2019年 | 4877篇 |
2018年 | 4776篇 |
2017年 | 5828篇 |
2016年 | 6528篇 |
2015年 | 6787篇 |
2014年 | 11035篇 |
2013年 | 10729篇 |
2012年 | 13829篇 |
2011年 | 14347篇 |
2010年 | 11025篇 |
2009年 | 11341篇 |
2008年 | 10307篇 |
2007年 | 12578篇 |
2006年 | 11066篇 |
2005年 | 9357篇 |
2004年 | 7707篇 |
2003年 | 6564篇 |
2002年 | 5595篇 |
2001年 | 4648篇 |
2000年 | 4080篇 |
1999年 | 3508篇 |
1998年 | 2726篇 |
1997年 | 2377篇 |
1996年 | 2017篇 |
1995年 | 1789篇 |
1994年 | 1524篇 |
1993年 | 1102篇 |
1992年 | 966篇 |
1991年 | 689篇 |
1990年 | 596篇 |
1989年 | 577篇 |
1988年 | 438篇 |
1987年 | 240篇 |
1986年 | 188篇 |
1985年 | 94篇 |
1984年 | 103篇 |
1983年 | 44篇 |
1982年 | 81篇 |
1981年 | 75篇 |
1980年 | 43篇 |
1979年 | 46篇 |
1978年 | 20篇 |
1975年 | 18篇 |
1964年 | 17篇 |
1959年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Hydrogel-based nanofibers or vice versa are a relatively new class of nanomaterials, in which hydrogels are structured in nanofibrous form. Structure and size of the material directly governs its functionality, therefore, in hydrogel science, the nanofibrous form of hydrogels enables its usage in targeted applications. Hydrogel nanofiber system combines the desirable properties of both hydrogel and nanofiber like flexibility, soft consistency, elasticity, and biocompatibility due to high water content, large surface area to volume ratio, low density, small pore size and interconnected pores, high stiffness, tensile strength, and surface functionality. Swelling behavior is a critical property of hydrogels that is significantly increased in hydrogel nanofibers due to their small size. Electrospinning is the most popular method to fabricate “hydrogel nanofibers,” while other processes like self-assembly, solution blowing and template synthesis also exist. Merging the characteristics of both hydrogels and nanofibers in one system allows applications in drug delivery, tissue engineering, actuation, wound dressing, photoluminescence, light-addressable potentiometric sensor (LAPS), waterproof breathable membranes, and enzymatic immobilization. Treatment of wastewater, detection, and adsorption of metal ions are also emerging applications. In this review paper, we intend to summarize in detail about electrospun “hydrogel nanofiber” in relation to its synthesis, properties, and applications. 相似文献
12.
《International Journal of Hydrogen Energy》2022,47(54):22981-22992
In this study, a three-dimensional model was established using the lattice Boltzmann method (LBM) to study the internal ice melting process of the gas diffusion layer (GDL) of the proton exchange membrane fuel cell (PEMFC). The single-point second-order curved boundary condition was adopted. The effects of GDL carbon fiber number, growth slope of the number of carbon fibers and carbon fiber diameter on ice melting were studied. The results were revealed that the temperature in the middle and lower part of the gradient distribution GDL is significantly higher than that of the no-gradient GDL. With the increase of the growth slope of the number of carbon fiber, the temperature and melting rate gradually increase, and the position of the solid-liquid interface gradually decreases. The decrease in the number of carbon fibers has a similar effect as the increase in the growth slope of the number of carbon fibers. In addition, as the diameter of the carbon fiber increases, the position of the solid-liquid interface gradually decreases first and then increases. 相似文献
13.
14.
《Ceramics International》2022,48(1):769-775
Brittle materials generally exhibit size effects, and the mechanical properties of these materials degrade significantly with an increase in size. However, the mathematical law governing the attenuation degree of mechanical properties with the increase in size is still unknown. In this study, maximum loads of differently sized ceramic test strips were subjected to three point bending tests under two working conditions of equal spans and span amplifications, respectively. Subsequently, the theoretical maximum loads of materials were calculated using the finite element method (FEM). By calculating the difference between the calculated values and the actual maximum loads, the attenuation of mechanical properties of ceramic samples were observed. The results show that the theoretical mechanical properties and the performance attenuation caused by the size effect tend to increase according to the following equation: y=ax3+bx2+cx+d. Therefore, mechanical properties and performance attenuation of any sample exhibiting a size within the experimental range can be predicted by a mathematical law, which was obtained through mechanical tests results of four samples with different sizes. The obtained mathematical law holds great significance for predicting the mechanical properties of materials under size effects. 相似文献
15.
16.
电路板在我们的日常生活中非常常见,这就使得印刷电路板的缺陷检测显得尤为重要。AOI作为新兴的检测PCB板缺陷的系统,在生产实际中正在被大家熟知并且应用。相较于传统的检测方式,AOI系统比较灵活,无论是在检测时间还是系统运算上,或者是对相关技术人员的要求相较于传统方式都比较有优势,本文就AOI系统在实际中的应用展开讨论,分析并且介绍了在实际应用中的具体细则。 相似文献
17.
Yu-Xuan Li Ping Li Yu-Zhe Wu Zhen-Liang Xu Ming-Ling Huang 《Ceramics International》2021,47(2):2180-2186
A novel TiO2 thin film was prepared on the ceramic hollow fiber by the sol-gel method using poly(vinylpyrrolidone) (PVP) and polyvinyl alcohol (PVA) as additives. SEM images verified the formation of TiO2 layer with various thickness using different composition of titania sols. The effect of the PVP and PVA contents on the TiO2 sol properties, the separation and the antifouling performance of the ultrafiltration membranes were investigated thoroughly. When the contents of PVP and PVA were 1.0 wt% and 0.8 wt%, respectively, the resultant membrane showed a thickness of 0.55 μm with a pure water flux of 255 L m?2 h?1. In addition, the adherent foulant bovine serum albumin was applied to evaluate the antifouling performance. During the three fouling-recovery cycles, the flux recovery ratio and the flux decay ratio maintained about 99% and 30%. The BSA flux and rejection were still 169 L m?2 h?1 and 96.9% after the cycles, indicating a superior antifouling property. 相似文献
18.
Bin Feng Xin Jiang Guisheng Zou Wengan Wang Tianming Sun Heng Yang Guanlei Zhao Mingye Dong Yu Xiao Hongwei Zhu Lei Liu 《Advanced functional materials》2021,31(29):2102359
The realization of liquid metal-based wearable systems will be a milestone toward high-performance, integrated electronic skin. However, despite the revolutionary progress achieved in many other components of electronic skin, liquid metal-based flexible sensors still suffer from poor sensitivity due to the insufficient resistance change of liquid metal to deformation. Herein, a nacre-inspired architecture composed of a biphasic pattern (liquid metal with Cr/Cu underlayer) as “bricks” and strain-sensitive Ag film as “mortar” is developed, which breaks the long-standing sensitivity bottleneck of liquid metal-based electronic skin. With 2 orders of magnitude of sensitivity amplification while maintaining wide (>85%) working range, for the first time, liquid metal-based strain sensors rival the state-of-art counterparts. This liquid metal composite features spatially regulated cracking behavior. On the one hand, hard Cr cells locally modulate the strain distribution, which avoids premature cut-through cracks and prolongs the defect propagation in the adjacent Ag film. On the other hand, the separated liquid metal cells prevent unfavorable continuous liquid-metal paths and create crack-free regions during strain. Demonstrated in diverse scenarios, the proposed design concept may spark more applications of ultrasensitive liquid metal-based electronic skins, and reveals a pathway for sensor development via crack engineering. 相似文献
19.
20.
Indoor surfaces may be adsorptive sinks with the potential to change Indoor Air Quality. To estimate this effect, the sorption parameters of formaldehyde and toluene were assessed on five floorings by an experimental method using solid-phase microextraction in an airtight emission cell. Adsorption rate constants ranged from 0.003 to 0.075 m·h−1, desorption rate constants from 0.019 to 0.51 h−1, and the partition coefficient from 0.005 to 3.9 m, and these parameters vary greatly from one volatile organic compound/material couple to another indicating contrasted sorption behaviors. A rubber was identified as a sink of formaldehyde characterized by a very low desorption constant close to 0. For these sorbent floorings identified, the adsorption rates of formaldehyde are from 2 to 4 times higher than those of toluene. Two models were used to evaluate the sink effects of floorings on indoor pollutant concentrations in one room from different realistic conditions. The scenarios tested came to the conclusion that the formaldehyde sorption on one rubber (identified as a sink) has a maximum contribution from 15% to 21% for the conditions of low air exchange rate. For other floorings, the sorption has a minor contribution less than or equal to 5%, regardless of the air exchange rate. 相似文献