全文获取类型
收费全文 | 2239篇 |
免费 | 205篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 33篇 |
综合类 | 1篇 |
化学工业 | 519篇 |
金属工艺 | 99篇 |
机械仪表 | 144篇 |
建筑科学 | 24篇 |
能源动力 | 81篇 |
轻工业 | 257篇 |
水利工程 | 6篇 |
石油天然气 | 2篇 |
无线电 | 434篇 |
一般工业技术 | 461篇 |
冶金工业 | 108篇 |
原子能技术 | 18篇 |
自动化技术 | 264篇 |
出版年
2024年 | 2篇 |
2023年 | 26篇 |
2022年 | 33篇 |
2021年 | 68篇 |
2020年 | 61篇 |
2019年 | 79篇 |
2018年 | 92篇 |
2017年 | 99篇 |
2016年 | 98篇 |
2015年 | 66篇 |
2014年 | 131篇 |
2013年 | 192篇 |
2012年 | 190篇 |
2011年 | 187篇 |
2010年 | 135篇 |
2009年 | 146篇 |
2008年 | 136篇 |
2007年 | 107篇 |
2006年 | 85篇 |
2005年 | 74篇 |
2004年 | 57篇 |
2003年 | 70篇 |
2002年 | 46篇 |
2001年 | 40篇 |
2000年 | 48篇 |
1999年 | 43篇 |
1998年 | 30篇 |
1997年 | 18篇 |
1996年 | 12篇 |
1995年 | 11篇 |
1994年 | 12篇 |
1993年 | 14篇 |
1992年 | 8篇 |
1991年 | 1篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1976年 | 3篇 |
排序方式: 共有2451条查询结果,搜索用时 0 毫秒
61.
62.
Gaseous Nanocarving‐Mediated Carbon Framework with Spontaneous Metal Assembly for Structure‐Tunable Metal/Carbon Nanofibers 下载免费PDF全文
Dae‐Hyun Nam Sungwoo Lee Young‐Joo Lee Jun‐Hyun Jo Euijoon Yoon Kyung‐Woo Yi Gun‐Do Lee Young‐Chang Joo 《Advanced materials (Deerfield Beach, Fla.)》2017,29(38)
Vapor phase carbon (C)‐reduction‐based syntheses of C nanotubes and graphene, which are highly functional solid C nanomaterials, have received extensive attention in the field of materials science. This study suggests a revolutionary method for precisely controlling the C structures by oxidizing solid C nanomaterials into gaseous products in the opposite manner of the conventional approach. This gaseous nanocarving enables the modulation of inherent metal assembly in metal/C hybrid nanomaterials because of the promoted C oxidation at the metal/C interface, which produces inner pores inside C nanomaterials. This phenomenon is revealed by investigating the aspects of structure formation with selective C oxidation in the metal/C nanofibers, and density functional theory calculation. Interestingly, the tendency of C oxidation and calculated oxygen binding energy at the metal surface plane is coincident with the order Co > Ni > Cu > Pt. The customizable control of the structural factors of metal/C nanomaterials through thermodynamic‐calculation‐derived processing parameters is reported for the first time in this work. This approach can open a new class of gas–solid reaction‐based synthetic routes that dramatically broaden the structure‐design range of metal/C hybrid nanomaterials. It represents an advancement toward overcoming the limitations of intrinsic activities in various applications. 相似文献
63.
Woosung Kwon Gyeongjin Lee Sungan Do Taiha Joo Shi‐Woo Rhee 《Small (Weinheim an der Bergstrasse, Germany)》2014,10(3):506-513
Size‐controlled soft‐template synthesis of carbon nanodots (CNDs) as novel photoactive materials is reported. The size of the CNDs can be controlled by regulating the amount of an emulsifier. As the size increases, the CNDs exhibit blue‐shifted photoluminescence (PL) or so‐called an inverse PL shift. Using time‐correlated single photon counting, ultraviolet photoelectron spectroscopy, and low‐temperature PL measurements, it is revealed that the CNDs are composed of sp2 clusters with certain energy gaps and their oleylamine ligands act as auxochromes to reduce the energy gaps. This insight can provide a plausible explanation on the origin of the inverse PL shift which has been debatable over a past decade. To explore the potential of the CNDs as photoactive materials, several prototypes of CND‐based optoelectronic devices, including multicolored light‐emitting diodes and air‐stable organic solar cells, are demonstrated. This study could shed light on future applications of the CNDs and further expedite the development of other related fields. 相似文献
64.
65.
Jin Kyung Song Duwoon Kim Jong-Bang Eun Byeong-Dae Choi Myung Joo Oh Sung Ju Jung 《Food science and biotechnology》2012,21(5):1405-1411
The edible ascidian, sea squirt Halocynthia roretzi (Drasche) is marine invertebrate that is a valuable source of foods and bioactive compounds. A severe disease of the sea squirt characterized by degeneration of tunic fibers formed of bundled cellulose microfibrils has occurred. We hypothesized that bacteria lyse the cellulose fibril structure, cellulase activity may be a causative agent of the disease. Among the bacteria isolated from diseased sea squirt, Pseudoalteromonas sp. NO3 had cellulase activity based on a Congo red overlay assay and starch-reducing activity. Sea squirts exhibited 40–100% cumulative mortality after injection with Pseudoalteromonas sp. NO3 using doses of 2×106?2×108 colony forming unit (CFU)/individual. Dead sea squirts possess thinner and ruptured tunics, which were similar to natural outbreaks. These results suggest that Pseudoalteromonas sp. NO3 possessing cellulase activity is one of the causes of tunic softness syndrome in sea squirt. 相似文献
66.
67.
Abstract: Hydrocarbons, gas compounds, and off‐odor volatiles were determined for irradiated (0 or 5 kGy) commercial sausages with different fat contents (16% and 29%) during a 60‐d storage period at 4 °C. Total of 4 hydrocarbons (C14:1, C15:0, C16:2, and C17:1) were detected only in irradiated sausages: the amount of C16:2 was the highest, followed by C17:1, C14:1, and C15:0. The concentrations of hydrocarbons decreased significantly (P < 0.05) with storage, but were still detectable at the end of 60‐d storage. Irradiated sausages produced significantly higher amounts of CO than the nonirradiated ones. CH4 was detected only in irradiated sausages. Dimethyl disulfide was detected only in irradiated sausages and its concentration decreased significantly (P < 0.05) with storage. Fat content of sausages showed a significant effect on the production and retention of hydrocarbons, gas compounds, and sulfur volatiles in irradiated sausages during storage. Some hydrocarbons (C16:2, C17:1, C14:1, and C15:0), CH4, and dimethyl disulfide were only found in irradiated sausages indicating that these compounds can be used as potential markers for irradiated sausages. 相似文献
68.
69.
Multimedia Tools and Applications - To catch up with the recent expansions of wireless platforms, the performance of quality management systems for wireless communication network services needs to... 相似文献