全文获取类型
收费全文 | 63239篇 |
免费 | 6119篇 |
国内免费 | 3068篇 |
专业分类
电工技术 | 3955篇 |
技术理论 | 4篇 |
综合类 | 4327篇 |
化学工业 | 10864篇 |
金属工艺 | 3523篇 |
机械仪表 | 4163篇 |
建筑科学 | 4574篇 |
矿业工程 | 1312篇 |
能源动力 | 1857篇 |
轻工业 | 4838篇 |
水利工程 | 1192篇 |
石油天然气 | 2642篇 |
武器工业 | 484篇 |
无线电 | 8282篇 |
一般工业技术 | 8683篇 |
冶金工业 | 2525篇 |
原子能技术 | 797篇 |
自动化技术 | 8404篇 |
出版年
2024年 | 245篇 |
2023年 | 925篇 |
2022年 | 1775篇 |
2021年 | 2509篇 |
2020年 | 1823篇 |
2019年 | 1687篇 |
2018年 | 1766篇 |
2017年 | 2003篇 |
2016年 | 2036篇 |
2015年 | 2663篇 |
2014年 | 3214篇 |
2013年 | 3900篇 |
2012年 | 4180篇 |
2011年 | 4641篇 |
2010年 | 4134篇 |
2009年 | 3751篇 |
2008年 | 3782篇 |
2007年 | 3445篇 |
2006年 | 3408篇 |
2005年 | 2944篇 |
2004年 | 2197篇 |
2003年 | 2092篇 |
2002年 | 2339篇 |
2001年 | 1948篇 |
2000年 | 1572篇 |
1999年 | 1386篇 |
1998年 | 1099篇 |
1997年 | 912篇 |
1996年 | 824篇 |
1995年 | 716篇 |
1994年 | 616篇 |
1993年 | 461篇 |
1992年 | 340篇 |
1991年 | 270篇 |
1990年 | 194篇 |
1989年 | 155篇 |
1988年 | 136篇 |
1987年 | 80篇 |
1986年 | 65篇 |
1985年 | 42篇 |
1984年 | 34篇 |
1983年 | 20篇 |
1982年 | 22篇 |
1981年 | 22篇 |
1980年 | 18篇 |
1979年 | 8篇 |
1976年 | 8篇 |
1975年 | 7篇 |
1959年 | 4篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
In vivo Kinetic Biodistribution of Nano‐Sized Outer Membrane Vesicles Derived from Bacteria
下载免费PDF全文
![点击此处可从《Small (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
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
22.
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
23.
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
24.
25.
26.
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
27.
28.
29.
Xiaopu Lyu Yunxi Huo Jin Yang Dawen Yao Kaimin Li Haoxian Lu Yangzong Zeren Hai Guo 《Indoor air》2021,31(5):1340-1352
Due to the high health risks associated with indoor air pollutants and long-term exposure, indoor air quality has received increasing attention. In this study, we put emphasis on the molecular composition, source emissions, and chemical aging of air pollutants in a residence with designed activities mimicking ordinary Hong Kong homes. More than 150 air pollutants were detected at molecular level, 87 of which were quantified at a time resolution of not less than 1 hour. The indoor-to-outdoor ratios were higher than 1 for most of the primary air pollutants, due to emissions of indoor activities and indoor backgrounds (especially for aldehydes). In contrast, many secondary air pollutants exhibited higher concentrations in outdoor air. Painting ranked first in aldehyde emissions, which also caused great enhancement of aromatics. Incense burning had the highest emissions of particle-phase organics, with vanillic acid and syringic acid as markers. The other noteworthy fingerprints enabled by online measurements included linoleic acid, cholesterol, and oleic acid for cooking, 2,5-dimethylfuran, stigmasterol, iso-/anteiso-alkanes, and fructose isomers for smoking, C28-C34 even n-alkanes for candle burning, and monoterpenes for the use of air freshener, cleaning agents, and camphor oil. We showed clear evidence of chemical aging of cooking emissions, giving a hint of indoor heterogeneous chemistry. This study highlights the value of organic molecules measured at high time resolutions in enhancing our knowledge on indoor air quality. 相似文献
30.
Xi Chen Zhengkun Yu Chen Yang Yao Chen Chao Jin Yuejiao Ding Wenbin Li Zhongmin Wan 《International Journal of Hydrogen Energy》2021,46(19):11127-11139
Flow field structure can largely determine the output performance of Polymer electrolyte membrane fuel cell. Excellent channel configuration accelerates electrochemical reactions in the catalytic layer, effectively avoiding flooding on the cathode side. In present study, a three-dimensional, multi-phase model of PEMFC with a 3D wave flow channel is established. CFD method is applied to optimize the geometry constructions of three-dimensional wave flow channels. The results reveal that 3D wave flow channel is overall better than straight channel in promoting reactant gases transport, removing liquid water accumulated in microporous layer and avoiding thermal stress concentration in the membrane. Moreover, results show the optimal flow channel minimum depth and wave length of the 3D wave flow channel are 0.45 mm and 2 mm, respectively. Due to the periodic geometric characteristics of the wave channel, the convective mass transfer is introduced, improving gas flow rate in through-plane direction. Furthermore, when the cell output voltage is 0.4 V, the current density in the novel channel is 23.8% higher than that of conventional channel. 相似文献