全文获取类型
收费全文 | 46990篇 |
免费 | 4153篇 |
国内免费 | 2069篇 |
专业分类
电工技术 | 2615篇 |
技术理论 | 2篇 |
综合类 | 2993篇 |
化学工业 | 7828篇 |
金属工艺 | 2570篇 |
机械仪表 | 2805篇 |
建筑科学 | 3815篇 |
矿业工程 | 1193篇 |
能源动力 | 1156篇 |
轻工业 | 3312篇 |
水利工程 | 778篇 |
石油天然气 | 2958篇 |
武器工业 | 307篇 |
无线电 | 5680篇 |
一般工业技术 | 5803篇 |
冶金工业 | 2409篇 |
原子能技术 | 510篇 |
自动化技术 | 6478篇 |
出版年
2024年 | 240篇 |
2023年 | 882篇 |
2022年 | 1435篇 |
2021年 | 2049篇 |
2020年 | 1505篇 |
2019年 | 1275篇 |
2018年 | 1371篇 |
2017年 | 1555篇 |
2016年 | 1418篇 |
2015年 | 1861篇 |
2014年 | 2359篇 |
2013年 | 2828篇 |
2012年 | 2825篇 |
2011年 | 3189篇 |
2010年 | 2860篇 |
2009年 | 2640篇 |
2008年 | 2570篇 |
2007年 | 2483篇 |
2006年 | 2468篇 |
2005年 | 2099篇 |
2004年 | 1471篇 |
2003年 | 1247篇 |
2002年 | 1224篇 |
2001年 | 1064篇 |
2000年 | 998篇 |
1999年 | 1222篇 |
1998年 | 1014篇 |
1997年 | 895篇 |
1996年 | 882篇 |
1995年 | 670篇 |
1994年 | 561篇 |
1993年 | 401篇 |
1992年 | 354篇 |
1991年 | 264篇 |
1990年 | 207篇 |
1989年 | 175篇 |
1988年 | 148篇 |
1987年 | 107篇 |
1986年 | 84篇 |
1985年 | 61篇 |
1984年 | 59篇 |
1983年 | 33篇 |
1982年 | 41篇 |
1981年 | 26篇 |
1980年 | 21篇 |
1979年 | 13篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1973年 | 5篇 |
1970年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
D. Golberg P.S. Dorozhkin Y. Bando M. Mitome C.C. Tang 《Diamond and Related Materials》2005,14(11-12):1857
Various multi-walled nanotubes in the B–C–N system are thoroughly investigated using a JEOL-3100FEF high-resolution field emission transmission electron microscope operating at 300 kV and equipped with an in-column built Omega filter. Spatially-resolved B, C and N elemental maps of the nanotubes are constructed. It is realized that a wide variety of tubular arrays composed of B, C and N atoms may exist in the system. Sandwich-like BN-rich and C-rich alternating tubular shells, graphitic C layers inside and outside of pure BN shells induced either by surface contamination, or electron beam irradiation, separation of C-rich and BN-rich tubes and/or BN particles within tubular bunches may take place. One should carefully take these effects into account while analyzing nanotube physical properties, e.g., electrical or optical, rather than simply rely on electron energy loss spectra typically collected from B, C and N containing nanostructures as a whole. Striking dependence of an individual nanotube electrical conductivity on tubular shell chemistry is demonstrated using I–V curve recording in an atomic force microscope. 相似文献
94.
95.
96.
稀土元素在陶瓷中的应用 总被引:1,自引:1,他引:0
从稀土元素的原子结构和化学特性出发,介绍了稀土元素的应用领域,阐述了稀土元素在陶瓷色釉料、各种氧化物陶瓷和非氧化物陶瓷中的应用. 相似文献
97.
A high‐melt‐strength polypropylene (HMSPP) was prepared using a twin‐screw reactive extruder from a commercial isotactic polypropylene through two stages, first, maleic anhydride is grafted to polypropylene to obtain a maleic anhydride‐grafted polypropylene (PP‐g‐MA), and then the grafted polymer is reacted with epoxy to extend the branched chain. Fourier transformed infrared spectroscopy indicated that maleic anhydride was grafted on polypropylene and reacted with epoxy. Melt flow rate and sag resistance test showed that the melt strength of the HMSPP improved considerably. Differential scanning calorimetry test showed that the long chain branches (LCBs) act as a nucleating agent in the crystallization of the HMSPP, which leads to a high crystallization temperature and crystallinity. Furthermore, the LCB efficiency of the HMSPP can also be calculated by analyzing its rheological property. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers 相似文献
98.
99.
Protein Extraction from Heat-stabilized Defatted Rice Bran: II. The Role of Amylase, Celluclast, and Viscozyme 总被引:1,自引:0,他引:1
ABSTRACT: The effectiveness of 3 carbohydrases for protein extraction from heat-stabilized defatted rice bran (HDRB) was evaluated. Amylase, viscozyme and celluclast extracted a maximum of 45.4, 12.1, and 28.5% protein, respectively. Further study showed that extracted protein ranged from 9.5 to 58.4% under conditions of water to bran ratio (5:1 to 20:1), α-amylase (0 to 110000 units/10 g rice bran), temperature (35 to 55 °C), and time (1 to 8 h). The maximum protein extracted was 58.4% with a water to bran ratio of 17:1, 87637 units amylase, and 50.9 °C. These results suggest that impure food-grade amylase containing protease is more effective than celluclast and viscozyme in protein extraction from HDRB. 相似文献
100.