全文获取类型
收费全文 | 41130篇 |
免费 | 3287篇 |
国内免费 | 1665篇 |
专业分类
电工技术 | 2265篇 |
技术理论 | 2篇 |
综合类 | 2411篇 |
化学工业 | 6943篇 |
金属工艺 | 2362篇 |
机械仪表 | 2536篇 |
建筑科学 | 3162篇 |
矿业工程 | 1077篇 |
能源动力 | 987篇 |
轻工业 | 2497篇 |
水利工程 | 620篇 |
石油天然气 | 2827篇 |
武器工业 | 243篇 |
无线电 | 5007篇 |
一般工业技术 | 5157篇 |
冶金工业 | 2226篇 |
原子能技术 | 429篇 |
自动化技术 | 5331篇 |
出版年
2024年 | 174篇 |
2023年 | 720篇 |
2022年 | 1117篇 |
2021年 | 1640篇 |
2020年 | 1240篇 |
2019年 | 994篇 |
2018年 | 1131篇 |
2017年 | 1294篇 |
2016年 | 1185篇 |
2015年 | 1569篇 |
2014年 | 1947篇 |
2013年 | 2429篇 |
2012年 | 2434篇 |
2011年 | 2714篇 |
2010年 | 2418篇 |
2009年 | 2240篇 |
2008年 | 2207篇 |
2007年 | 2187篇 |
2006年 | 2189篇 |
2005年 | 1912篇 |
2004年 | 1294篇 |
2003年 | 1107篇 |
2002年 | 1067篇 |
2001年 | 905篇 |
2000年 | 938篇 |
1999年 | 1144篇 |
1998年 | 973篇 |
1997年 | 869篇 |
1996年 | 842篇 |
1995年 | 652篇 |
1994年 | 562篇 |
1993年 | 389篇 |
1992年 | 346篇 |
1991年 | 259篇 |
1990年 | 200篇 |
1989年 | 173篇 |
1988年 | 144篇 |
1987年 | 107篇 |
1986年 | 78篇 |
1985年 | 58篇 |
1984年 | 58篇 |
1983年 | 30篇 |
1982年 | 39篇 |
1981年 | 24篇 |
1980年 | 19篇 |
1979年 | 11篇 |
1977年 | 7篇 |
1976年 | 7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 31 毫秒
21.
Priyadarshi Chakraborty Yiming Tang Tomoya Yamamoto Yifei Yao Tom Guterman Shai Zilberzwige-Tal Nofar Adadi Wei Ji Tal Dvir Ayyalusamy Ramamoorthy Guanghong Wei Ehud Gazit 《Advanced materials (Deerfield Beach, Fla.)》2020,32(9):1906043
Self-assembled peptide hydrogels represent the realization of peptide nanotechnology into biomedical products. There is a continuous quest to identify the simplest building blocks and optimize their critical gelation concentration (CGC). Herein, a minimalistic, de novo dipeptide, Fmoc-Lys(Fmoc)-Asp, as an hydrogelator with the lowest CGC ever reported, almost fourfold lower as compared to that of a large hexadecapeptide previously described, is reported. The dipeptide self-assembles through an unusual and unprecedented two-step process as elucidated by solid-state NMR and molecular dynamics simulation. The hydrogel is cytocompatible and supports 2D/3D cell growth. Conductive composite gels composed of Fmoc-Lys(Fmoc)-Asp and a conductive polymer exhibit excellent DNA binding. Fmoc-Lys(Fmoc)-Asp exhibits the lowest CGC and highest mechanical properties when compared to a library of dipeptide analogues, thus validating the uniqueness of the molecular design which confers useful properties for various potential applications. 相似文献
22.
23.
24.
25.
Multimedia Tools and Applications - We present three stages of a novel backgrounds subtraction method in this paper: a new pixel-block based randomized arrangement is utilized to preprocess all the... 相似文献
26.
Weiguo Cao Wenjuan Li Liang Zhang Jianfa Chen Shuo Yu Zhuanghong Zhou Yun Zhang Xiaobo Shen Yingxin Tan 《International Journal of Hydrogen Energy》2021,46(52):26693-26707
The explosion venting duct can effectively reduce the hazard degree of a gas explosion and conduct the venting energy to the safe area. To investigate the flame quantitative propagation law of explosion venting with a duct, the effects of hydrogen fraction and explosion venting duct length on jet flame propagation characteristics of premixed H2-air mixtures were analyzed through experiment and simulation. The experiment results under initial conditions of room temperature and 1 atm show that when hydrogen fraction was high enough, part of the unburned hydrogen was mixed with air again to reach an ignitable concentration, resulting in the secondary combustion was easier produced and the duration of the secondary flame increased. With the increase of venting duct length, the flame front distance and propagation velocity increased. Meanwhile, the spatial distribution of pressure field and temperature field, and the propagation process and mechanism of the flame venting with a duct were analyzed using FLUENT software. The variation of the pressure wave and the pressure reflection oscillation law in the explosion venting duct was captured. Therefore, in the industrial explosion venting design with a duct, the hazard caused by the coupling of venting pressure and venting flame under different fractions should be considered comprehensively. 相似文献
27.
Xiaohu Ren Xilou Pu Hongfeng Yin Yun Tang Hudie Yuan Huiqing Fan 《Ceramics International》2021,47(9):12122-12129
Hexagonal barium ferries is a promising and efficient microwave (MW) absorbing material, but the low dielectric loss and poor conductivity have limited their extensive applications. In this work, a simple tactic of coating conductive polymer PANI on hexaferrite BaCo2Fe16O27 is presented, wherein the dielectric properties are customized, and more significantly, the electromagnetic loss is greatly enhanced. As displayed from structural characterizations, PANI were coated equably on the surface of hexaferrite grains by an in-situ polymerization process. The outcomes exhibit the as-prepared PANI@hexaferrite composite has remarkable electromagnetic wave absorption capacity. When the thickness is 6.0 mm, the minimal RL of ?40.4 dB was achieved at 2.9 GHz. The effective absorption bandwidth (RL < ?20 dB) of 0.65 GHz, 0.53 GHz, 0.65 GHz, 0.52 GHz, 0.46 GHz and 0.39 GHz was achieved separately when the thickness ranges from 4 to 9 mm. The highly efficient MW absorbing performance of PANI@hexaferrite composite were the consequence of multiple loss mechanisms and perfect impedance matching. It is demonstrated that the PANI@hexaferrite composite with excellent MW absorption performance is expected to be potential MW absorbers for extensive applications. 相似文献
28.
Chen Tang Tiehu Li Yuhang Bai Junjie Gao Wenbo Yang Shasha Jiao Tingkai Zhao 《Ceramics International》2018,44(10):11812-11819
Recently, ceramic matrix composites reinforced by short carbon fibers (CFs) attracted increasing attentions. To further improve mechanical properties and oxidation resistances, CFs were subjected to oxidation and acidification followed by sol-gel dip-coating to deposit ZrO2 on their surfaces. ZrO2-Cf/SiC composites were fabricated by joint hot compression molding and sintering, compared to Cf/SiC and SiC prepared by the same method. Microstructural analyses indicated that ZrO2 coatings were successfully deposited on CF surfaces, formed strong bonding and interfaces between CF and the matrix. Meanwhile, CFs were found uniformly distributed in SiC matrix with random orientations. Flexural curves of ZrO2-Cf/SiC and Cf/SiC revealed the presence of “false plasticity” regions after sharp drops, which were quite different from brittle flexural behavior of SiC ceramic. Compression strength of the three samples showed step-up growth. ZrO2-Cf/SiC exhibited the highest value, indicating the introduction of CFs and ZrO2 coatings do have great influence on mechanical performances. After heat treatment, ZrO2-Cf/SiC exhibited better oxidation resistance than Cf/SiC, with weight loss ratios estimated to ??3.76% and ??6.43%, respectively. These improved properties indicated that ZrO2-Cf/SiC would be excellent alternatives to other existence materials under ultra-high temperature environments. 相似文献
29.
30.