全文获取类型
收费全文 | 5659篇 |
免费 | 719篇 |
国内免费 | 269篇 |
专业分类
电工技术 | 2793篇 |
综合类 | 566篇 |
化学工业 | 332篇 |
金属工艺 | 177篇 |
机械仪表 | 193篇 |
建筑科学 | 175篇 |
矿业工程 | 165篇 |
能源动力 | 96篇 |
轻工业 | 509篇 |
水利工程 | 70篇 |
石油天然气 | 61篇 |
武器工业 | 21篇 |
无线电 | 501篇 |
一般工业技术 | 209篇 |
冶金工业 | 186篇 |
原子能技术 | 97篇 |
自动化技术 | 496篇 |
出版年
2024年 | 9篇 |
2023年 | 44篇 |
2022年 | 108篇 |
2021年 | 129篇 |
2020年 | 141篇 |
2019年 | 128篇 |
2018年 | 125篇 |
2017年 | 199篇 |
2016年 | 213篇 |
2015年 | 233篇 |
2014年 | 343篇 |
2013年 | 322篇 |
2012年 | 472篇 |
2011年 | 527篇 |
2010年 | 372篇 |
2009年 | 406篇 |
2008年 | 406篇 |
2007年 | 444篇 |
2006年 | 468篇 |
2005年 | 317篇 |
2004年 | 247篇 |
2003年 | 207篇 |
2002年 | 185篇 |
2001年 | 114篇 |
2000年 | 91篇 |
1999年 | 72篇 |
1998年 | 55篇 |
1997年 | 30篇 |
1996年 | 55篇 |
1995年 | 44篇 |
1994年 | 26篇 |
1993年 | 23篇 |
1992年 | 20篇 |
1991年 | 13篇 |
1990年 | 11篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 8篇 |
1986年 | 2篇 |
1984年 | 6篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1964年 | 1篇 |
1962年 | 2篇 |
1961年 | 1篇 |
1958年 | 1篇 |
1957年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有6647条查询结果,搜索用时 15 毫秒
1.
为了解汉江上游干支流沉积物细菌多样性以及确定性过程和随机性过程在沉积物细菌群落构建过程中的相对重要性,基于Illumina高通量测序技术,分析了环境因子对细菌群落组成的影响,采用非度量多维尺度(NMDS)排序探究了季节之间沉积物细菌群落的差异,并结合中性群落模型和标准化随机率量化了确定性过程和随机过程对群落构建的影响。结果表明:汉江上游及其支流细菌群落主要由变形菌门(Proteobacteria)、拟杆菌门(Bacteroidetes)、蓝藻门(Cyanophyta)、浮霉菌门(Planctomycetes)和酸杆菌门(Acidobacteria)等组成;细菌群落在不同季节有显著差异;地理距离和环境因子对细菌群落结构影响较小,确定性过程并未在细菌群落组成中起到主导作用;随机过程很大程度上影响了群落在秋季和春季的组成,是沉积物细菌群落构建的主导因素。 相似文献
2.
采用直流磁控溅射和后退火氧化工艺在p型GaAs单晶衬底上成功制备了n-VO_2/pGaAs异质结,研究了不同退火温度和退火时间对VO_2/GaAs异质结性能的影响,并分析其结晶取向、化学组分、膜层质量以及光电特性。结果表明,在退火时间2 h和退火温度693 K下能得到相变性能最佳的VO_2薄膜,相变前后电阻变化约2个数量级。VO_2/GaAs异质结在308 K、318 K和328 K温度下具有较好的整流特性,对应温度下的阈值跳变电压分别为6.9 V、6.6 V和6.2 V,该结果为基于VO_2相变特性的异质结光电器件的设计与应用提供了可行性。 相似文献
3.
4.
摘要:为了研究300M超高强钢在中性盐雾环境中的腐蚀行为及腐蚀机制,采用失重法,宏观、微观腐蚀形貌分析,三维表面轮廓分析及电化学分析的研究方法,来表征腐蚀实验现象并进行分析。结果表明:300M超高强钢在中性盐雾环境中的腐蚀产物为FeOOH、Fe2O3、Fe(OH)3和Fe3O4;腐蚀速率随着腐蚀时间逐渐降低,腐蚀后期(72h)腐蚀速率降低50%;腐蚀初期以点蚀为主,点蚀坑通过横向扩展,逐渐发展为后期的均匀腐蚀,腐蚀表面形貌呈沟壑状;外腐蚀层对基体的保护能力很弱,Cr元素在锈层靠近基体的一侧偏聚使内腐蚀层具有一定的抗腐蚀性。 相似文献
5.
6.
Dr. Dandan Li Qianqian Guo Liming Ding Wei Zhang Lu Cheng Yanqiu Wang Dr. Zhuobin Xu Dr. Huihui Wang Prof. Lizeng Gao 《Chembiochem : a European journal of chemical biology》2020,21(18):2620-2627
Peroxidase-mimicking nanozymes that can generate toxic hydroxyl radicals (.OH) hold great promise as antibacterial alternatives. However, most of them display optimal performance under strongly acidic conditions (pH 3–4), and are thus not feasible for many medical uses, including burn infections with a wound pH close to neutral. Herein, we report a copper-based nanozyme (CuCo2S4) that exhibits intrinsic peroxidase-like activity and can convert H2O2 into .OH at neutral pH. In particular, bimetallic CuCo2S4 nanoparticles (NPs) exhibited enhanced peroxidase-like activity and antibacterial capacity, superior to that of the corresponding monometallic CuS and CoS NPs. The CuCo2S4 nanozymes possessed excellent ability to kill various bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). Furthermore, this CuCo2S4 nanozymes could effectively disrupt MRSA biofilms in vitro and accelerate MRSA-infected burn healing in vivo. This work provides a new peroxidase mimic to combat bacteria in neutral pH milieu and this CuCo2S4 nanozyme could be a promising antibacterial agent for the treatment of burn infections. 相似文献
7.
8.
《Microelectronics Reliability》2015,55(11):2229-2235
In these decades, integrated circuits for biomedical electronics applications have been designed and implemented in CMOS technologies. In order to be safely used by human, all microelectronic products must meet the reliability specifications. Therefore, electrostatic discharge (ESD) must be taken into consideration. To protect the biomedical integrated circuits in CMOS technologies from ESD damage, a dual-directional silicon-controlled rectifier (DDSCR) device was presented in this work. Experimental results show that the DDSCR has the advantages of high ESD robustness, low leakage, large swing tolerance, and good latchup immunity. The DDSCR was suitable for ESD protection in biomedical integrated circuits. 相似文献
9.
《Food Control》2016
Automated produce washers can be a useful processing aid when treating fresh produce contaminated with pathogens. The use of near neutral pH electrolyzed (NEO) water as a wash or sanitizing solution has been shown to lead to significant reductions of Escherichia coli O157:H7 and Salmonella on fresh produce. To further enhance reported pathogen reductions, the effects of a combined NEO water (155 mg/L free chlorine, pH 6.5) and ultrasound wash protocol on lettuce and tomatoes inoculated with E. coli O157:H7 and S. Typhimurium DT 104 were studied. The effects of the pH of NEO water and washer agitation on pathogen reductions were also assessed. Inoculated tomatoes and lettuce leaves were treated with either chilled deionized water or NEO water, with or without 20 kHz ultrasound (130 W and 210 W). Tomatoes were treated for 1, 3 and 5 min while lettuce was treated for 5, 10 and 15 min. Ultrasound significantly increased the oxidation-reduction potential (ORP) of NEO water (p < 0.05) but did not affect the pH and free chlorine concentration (p > 0.05). Increased washing time and higher ultrasonic power led to significantly greater reductions of both pathogens on produce items (p < 0.05). NEO water combined with 210 W ultrasonication for 15 min led to 4.4 and 4.3 log reductions of E. coli O157:H7 and S. Typhimurium on lettuce, respectively, while 210 W ultrasound for 5 min completely inactivated both pathogens on tomatoes. Both pathogens were completely inactivated in NEO water solutions, suggesting that its use presents little chance of cross-contamination. 相似文献
10.
This paper is concerned with numerical stability of general linear methods (GLMs) for a system of linear neutral delay differential-algebraic equations. A sufficient and necessary condition for asymptotic stability of GLMs solving such system is derived. Based on this main result, we further investigate the asymptotic stability of linear multistep methods, Runge–Kutta methods, and block θ-methods, respectively. Numerical experiments confirm our theoretical result. 相似文献