全文获取类型
收费全文 | 125257篇 |
免费 | 11030篇 |
国内免费 | 5896篇 |
专业分类
电工技术 | 7685篇 |
技术理论 | 14篇 |
综合类 | 8753篇 |
化学工业 | 20755篇 |
金属工艺 | 6796篇 |
机械仪表 | 7739篇 |
建筑科学 | 9697篇 |
矿业工程 | 3049篇 |
能源动力 | 3554篇 |
轻工业 | 9419篇 |
水利工程 | 2443篇 |
石油天然气 | 6107篇 |
武器工业 | 1001篇 |
无线电 | 15519篇 |
一般工业技术 | 15821篇 |
冶金工业 | 5529篇 |
原子能技术 | 1456篇 |
自动化技术 | 16846篇 |
出版年
2024年 | 410篇 |
2023年 | 1901篇 |
2022年 | 3408篇 |
2021年 | 5052篇 |
2020年 | 3774篇 |
2019年 | 3154篇 |
2018年 | 3488篇 |
2017年 | 3781篇 |
2016年 | 3766篇 |
2015年 | 4974篇 |
2014年 | 6174篇 |
2013年 | 7376篇 |
2012年 | 8076篇 |
2011年 | 8894篇 |
2010年 | 7676篇 |
2009年 | 7156篇 |
2008年 | 7178篇 |
2007年 | 6674篇 |
2006年 | 6474篇 |
2005年 | 5623篇 |
2004年 | 4189篇 |
2003年 | 3846篇 |
2002年 | 3964篇 |
2001年 | 3407篇 |
2000年 | 3168篇 |
1999年 | 3278篇 |
1998年 | 2722篇 |
1997年 | 2241篇 |
1996年 | 2142篇 |
1995年 | 1808篇 |
1994年 | 1561篇 |
1993年 | 1122篇 |
1992年 | 852篇 |
1991年 | 639篇 |
1990年 | 520篇 |
1989年 | 447篇 |
1988年 | 341篇 |
1987年 | 214篇 |
1986年 | 158篇 |
1985年 | 116篇 |
1984年 | 84篇 |
1983年 | 56篇 |
1982年 | 70篇 |
1981年 | 50篇 |
1980年 | 46篇 |
1979年 | 21篇 |
1976年 | 21篇 |
1975年 | 9篇 |
1974年 | 12篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Lu Xu Baijun Liu Mingyao Zhang Yang Bai Jinming Zhang Jiayin Song 《Polymer Engineering and Science》2020,60(6):1194-1201
A series of methacrylate-acrylonitrile-butadiene-styrene (MABS) resins was prepared using bulk polymerization. The polarity of the continuous phase and the compatibility of two phases were changed by adjusting the methyl methacrylate (MMA) content, choosing values that were close to styrene-butadiene rubber solubility value. The possibility of controlling the microstructure of the MABS resin by changing the polarity of the components and the compatibility of two phases was assessed. The dynamic mechanical analysis shows that the compatibility of two phases varies with the MMA content. The morphological analysis shows that increasing MMA contents results in a gradual decrease in the sub-inclusion structure with a network skeleton of rubber particles, and that all the particles become solid rubber when the MMA content reaches 75%. The sub-inclusion structure reappears but does not have a network skeleton when the MMA content is 90%. The impact strength and morphological analysis indicate that the solid rubber particles and the sub-inclusion structure with a network skeleton provide excellent toughness, while the sub-inclusion structure without a network skeleton does not. In contrast, the transmittance of the ABS resin first increased and then decreased with increasing MMA content. 相似文献
32.
In vivo Kinetic Biodistribution of Nano‐Sized Outer Membrane Vesicles Derived from Bacteria 下载免费PDF全文
Su Chul Jang Sae Rom Kim Yae Jin Yoon Kyong‐Su Park Ji Hyun Kim Jaewook Lee Oh Youn Kim Eun‐Jeong Choi Dae‐Kyum Kim Dong‐Sic Choi Yoon‐Keun Kim Jaesung Park Dolores Di Vizio Yong Song Gho 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(4):456-461
Evaluation of kinetic distribution and behaviors of nanoparticles in vivo provides crucial clues into their roles in living organisms. Extracellular vesicles are evolutionary conserved nanoparticles, known to play important biological functions in intercellular, inter‐species, and inter‐kingdom communication. In this study, the first kinetic analysis of the biodistribution of outer membrane vesicles (OMVs)—bacterial extracellular vesicles—with immune‐modulatory functions is performed. OMVs, injected intraperitoneally, spread to the whole mouse body and accumulate in the liver, lung, spleen, and kidney within 3 h of administration. As an early systemic inflammation response, increased levels of TNF‐α and IL‐6 are observed in serum and bronchoalveolar lavage fluid. In addition, the number of leukocytes and platelets in the blood is decreased. OMVs and cytokine concentrations, as well as body temperature are gradually decreased 6 h after OMV injection, in concomitance with the formation of eye exudates, and of an increase in ICAM‐1 levels in the lung. Following OMV elimination, most of the inflammatory signs are reverted, 12 h post‐injection. However, leukocytes in bronchoalveolar lavage fluid are increased as a late reaction. Taken together, these results suggest that OMVs are effective mediators of long distance communication in vivo. 相似文献
33.
34.
与传统比例-积分-微分(PID)控制方法相比,滑模控制(SMC)方法可以比较容易地将不确定性纳入控制器设计中,从而增强系统的鲁棒性。探索了SMC技术在运载器主动段姿态控制中的工程应用,首先通过分析基于趋近律的SMC系统,提出了降低不连续切换项系数的需求,然后研究了基于干扰上界的SMC方法。三通道小偏差仿真结果验证了两种方法的控制效果,表明第2种控制器的鲁棒性更好,稳态误差小,同时发动机喷管摆角需求较小。 相似文献
35.
本文结合HTH电路的复杂性等特征分析与实际应用现状,研究了HTH电路的具体检测技术方法并对当前热点技术进行对比分析,探讨了HTH电路检测方法的技术发展趋势。 相似文献
36.
In this article, the silver-plated polyamide fabrics (SPPAFs) with high electroconductibility and shielding effectiveness were fabricated by using in situ reduction of polydopamine and chemical silvering. The effects of SPPAFs dopamine (C8H11O2N) and silver nitrate (AgNO3) concentration on surface resistivity and electromagnetic interference shielding effectiveness were studied. The results showed that the surface resistivity of SPPAFs can reach a minimum value of 0.06 ± 0.014 Ω cm−1, when C8H11O2N concentration is 4 g L−1 and the AgNO3 concentration is 120 g L−1. The shielding effectiveness of SPPAFs in the wide frequency range of 10–3000 MHz increases with the increase in the concentration of AgNO3, and increases first and stabilizes afterward with increasing C8H11O2N concentration. When the concentration of C8H11O2N and AgNO3 is 3 and 120 g L−1, respectively, mean shielding effectiveness values in the low-, medium-, and high-frequency bands are 71.3, 73.8, and 76.1 dB, respectively. Moreover, the mean shielding effectiveness values is 83.79 dB in the frequency range of 1.2–2.3 GHz. The dominant shielding mechanism of SPPAFs is the reflected electromagnetic waves and the absorption shielding effectiveness is less than 2 dB. The average electromagnetic shielding values of SPPAFs are above 67 dB after 16 weeks of storage, when C8H11O2N concentration is 4 g L−1 and the AgNO3 concentration is 80 and 100 g L−1. The prepared SPPAFs show promising applications in military textiles and smart wearable clothing. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48227. 相似文献
37.
使用气-质联用仪测定餐饮废油生物柴油(WCME)和-10号柴油(-10PD)的组成,使用冷滤点试验器和运动黏度试验器测定WCME的低温流动性,同时使用调合、添加低温流动性改进剂的方法改进WCME的低温流动性。实验结果表明,WCME主要由饱和脂肪酸甲酯和不饱和脂肪酸甲酯组成,质量分数分别为27.63%和71.81%;WCME冷滤点为0℃,运动黏度(40℃)为4.41mm2/s;WCME与-10PD调合后,冷滤点降低,其中B20的冷滤点最低,为-13℃,运动黏度随着WCME的体积分数的减少,逐渐接近-10PD的运动黏度。通过添加低温流动性改进剂,WCME,B10,B20的冷滤点分别从0,-8,-13℃降至-4,-26,-25℃。 相似文献
38.
39.
40.
本文提出了一种基于分散加载技术实现Boot程序和用户应用程序在同一个工程编写开发的固件更新方法 .通过编写分散加载规范文件在工程中实现代码存储区分区.为了保证固件更新的稳定性和可靠性,在固件下载过程中引入CRC校验、丢包错包重传等容错技术.实验结果 验证了方法的有效性和可靠性. 相似文献