首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   53276篇
  免费   5654篇
  国内免费   3110篇
电工技术   5560篇
技术理论   4篇
综合类   6374篇
化学工业   2691篇
金属工艺   1484篇
机械仪表   3884篇
建筑科学   5250篇
矿业工程   2653篇
能源动力   1349篇
轻工业   4410篇
水利工程   2632篇
石油天然气   4699篇
武器工业   1347篇
无线电   4175篇
一般工业技术   3049篇
冶金工业   2112篇
原子能技术   354篇
自动化技术   10013篇
  2024年   203篇
  2023年   685篇
  2022年   1371篇
  2021年   1701篇
  2020年   1882篇
  2019年   1343篇
  2018年   1343篇
  2017年   1545篇
  2016年   1916篇
  2015年   2134篇
  2014年   3809篇
  2013年   3131篇
  2012年   4464篇
  2011年   4501篇
  2010年   3320篇
  2009年   3272篇
  2008年   3029篇
  2007年   3712篇
  2006年   3266篇
  2005年   2937篇
  2004年   2326篇
  2003年   2006篇
  2002年   1520篇
  2001年   1359篇
  2000年   1030篇
  1999年   845篇
  1998年   607篇
  1997年   562篇
  1996年   457篇
  1995年   365篇
  1994年   298篇
  1993年   212篇
  1992年   156篇
  1991年   140篇
  1990年   83篇
  1989年   109篇
  1988年   60篇
  1987年   43篇
  1986年   41篇
  1985年   29篇
  1984年   34篇
  1983年   35篇
  1982年   20篇
  1981年   14篇
  1979年   11篇
  1978年   9篇
  1977年   9篇
  1975年   10篇
  1959年   7篇
  1956年   7篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Sweet pickled mango named Ma-Muang Bao Chae-Im is a traditional preserved mango from Hat Yai, Thailand. This study investigated (I) volatile and non-volatile compound profiles of commercial Ma-Muang Bao Chae-Im and (II) their relationship to consumer preference. Untargeted metabolomics profiling was performed by gas chromatography-mass quadrupole-time of flight analysis. There were 117 volatile and 44 non-volatile compounds annotated in six commercial brands of Ma-Muang Bao Chae-Im. Furthermore, 46 volatile and 19 non-volatile compounds’ discriminant markers were found by Partial least square discriminant analysis. Among those markers, sorbic and benzoic acid were observed in several brands; moreover, the combination of both compounds altered the volatile profile, especially the ester group. Partial least square regression revealed that overall consumer liking is correlated to 1-heptanol; 1-octanol; acetoin; acetic acid, 2-phenylethyl ester; D-manitol; terpenes and terpenoids, while firmness to sucrose and L-(-)-sorbofuranose. On the other hand, most ester compounds were not related to consumer preference.  相似文献   
2.
In the Internet of Things (IoT), a huge amount of valuable data is generated by various IoT applications. As the IoT technologies become more complex, the attack methods are more diversified and can cause serious damages. Thus, establishing a secure IoT network based on user trust evaluation to defend against security threats and ensure the reliability of data source of collected data have become urgent issues, in this paper, a Data Fusion and transfer learning empowered granular Trust Evaluation mechanism (DFTE) is proposed to address the above challenges. Specifically, to meet the granularity demands of trust evaluation, time–space empowered fine/coarse grained trust evaluation models are built utilizing deep transfer learning algorithms based on data fusion. Moreover, to prevent privacy leakage and task sabotage, a dynamic reward and punishment mechanism is developed to encourage honest users by dynamically adjusting the scale of reward or punishment and accurately evaluating users’ trusts. The extensive experiments show that: (i) the proposed DFTE achieves high accuracy of trust evaluation under different granular demands through efficient data fusion; (ii) DFTE performs excellently in participation rate and data reliability.  相似文献   
3.
To investigate the effect of cooking temperature (55, 65, 75, 85 and 95 °C) on texture and flavour binding of braised sauce porcine skin (BSPS), sensory acceptance, microstructure and flavour-binding capacity were investigated during the processing of BSPS. Samples cooked at 85 and 95 °C showed better texture and aroma scores. Hardness and chewiness of BSPS were obviously improved at 85 and 95 °C than control group. Collagen structure was significantly destroyed over 85 °C. The porcine skin collagen heated at 85 and 95 °C showed relatively higher flavour-binding capacity than other samples. The improvement of texture of BSPS was mainly attributed to the degradation of collagen. Higher aroma scores of BSPS were related to intense binding abilities with aroma compounds at 85 and 95 °C. Cooking at 85 or 95 °C could be an optimal cooking temperature for BSPS.  相似文献   
4.
为缓解我国水、能源和粮食资源紧张问题,促进资源可持续利用,构建水-能源-粮食系统,利用耦合协调度模型对我国的30个省(自治区、直辖市)进行测算,并利用空间杜宾模型分析主要影响因素。结果表明:2003—2017年,我国能源、粮食评价[JP]指数高于水资源评价指数,系统综合评价指数逐年递增;大部分省份耦合协调度处于初级协调水平且呈现逐年上升的态势,个别省份耦合协调度濒临失调;耦合协调度空间自相关性较强,虽有明显波动,但是呈现逐年加强的态势;影响耦合协调度的主要因素有从业人口数、固定资产投资额、人均生产总值、人口总数、[JP]文盲人口占比、工业污染排放、城镇化。  相似文献   
5.
《Ceramics International》2022,48(11):15243-15251
Green combustion was used to prepare a ferrite composition of Mg0.4Zn0.6Fe2O4 using a blend of fresh lemon juice as a natural fuel-reductant. Effect of heat treatment on phase, morphological, dielectric, and humidity sensor properties is discussed. The formation of a cubic spinel ferrite has been established by XRD-diffraction and vibrational spectroscopic studies. The experimental lattice parameter ranges from 8.3721 to 8.3631 Å. The broadening of octahedral band (υ2) in the vibrational spectra is an identification for the existence of ferrite nanoparticles in various sizes. The typical crystallite size ranges from 10.2 to 36.9 nm. Using micrographs obtained from field-effect scanning electron microscopy (FESEM), researchers observed a spherical-shaped microstructure with agglomerated nanoparticles. Dielectric investigations have shown that the current ferrite composition has typical dielectric dispersion. The highest reported value for saturation magnetization (Ms) in the present study is 33 emu/g. Magnetic behaviour is primarily influenced by magnetocrystalline anisotropy, cation distribution, and crystallite size. The existence of void spaces in the sintered samples, as well as their porous nature, rendered them suitable for humidity sensor applications. Sintered samples have good sensing capability at 900 °C. The current findings are integrated in terms of cation distribution and magnetocrystalline anisotropy, assuming fine size effects of ferrite nanoparticles.  相似文献   
6.
Collaboration with artificial intelligence (AI) is a growing trend even in the field of creativity. This paper examines which quantitative metrics can be used to comparatively analyse human-computer co-creativity with children. To study this question, 24 schoolchildren of age 10–11 wrote a poem with three co-creative poetry writing processes: a human-computer, a human-human, and a human-human-computer process. The computational participant in the processes was an AI-based application called the Poetry Machine. The children were asked to evaluate their user experience with a 5-point Likert-type questionnaire after each writing process and a comparative questionnaire after finishing all processes. The metrics used in the evaluation were immediate fun, long-term enjoyment, creativity, self-expression, outcome satisfaction, ease of starting and finishing writing, quality of ideas and support from others, and ownership.

Significant differences were found in fun, long-term enjoyment, quality of ideas, support, and ownership. The high number of statistically relevant results was enabled by exposing all participants to all writing processes, and the comparative questionnaire. The human-human-computer process was evaluated the best in long-term enjoyment and the human-computer process the weakest in support and idea quality. Creativity and ease of finishing writing turned out to be outlining metrics for the co-creative processes.  相似文献   

7.
孙淑光  周琪 《计算机应用》2020,40(5):1522-1528
针对自动飞行控制系统结构复杂、关联部件众多,发生故障时诊断时间长,从而影响飞机运行效率的问题,提出一种基于飞机通信寻址报告系统(ACARS)的远程实时故障诊断方案。首先,分析自动飞行控制系统的故障特点,设计搭建检测滤波器;然后,利用ACARS数据链实时发送的自动飞行控制系统的关键信息进行相关部件的残差计算,并根据残差决策算法进行故障诊断及定位;最后,针对不同故障部件残差间的差异大、决策门限无法统一的缺点,提出基于二次差值的残差决策改进算法,减缓了检测对象的整体变化趋势,降低了随机噪声和干扰的影响,避免了将瞬态故障诊断为系统故障的情况。实验仿真结果表明,基于二次差值的改进残差决策算法避免了多决策门限的复杂性,在采样时间为0.1 s的情况下,故障检测所需时间大约为2 s,故障检测时间大幅降低,有效故障检测率大于90%。  相似文献   
8.
曾靓妮  邓方阁 《红外技术》2020,42(5):501-505
乳腺疾病已严重危害女性身心健康,其中乳腺癌更位居全球范围内女性癌症发病率和死亡率首位,因此乳腺癌的早期发现意义重大。传统结构影像学早期检测疾病具有一定局限性,而红外热成像作为功能成像技术可为乳腺癌的早期筛查提供有效线索。因此本文主要就红外热成像在乳腺疾病的早期检测及预后评估的应用价值进行综述。  相似文献   
9.
为保证航材备件的完好率,解决仓储机载通信电台长期不通电导致的装备性能下降甚至出现故障的问题,综合运用自动测试、虚拟仪器、面向信号设计等技术,以计算机为核心,以PXI仪器、GPIB仪器为依托,以多种总线接口为纽带,构建了一种可靠性高、通用性好、操作简便、可扩展性强的自动化通电老炼平台。通过在航材仓库中使用,证明该电台老炼检测系统降低了仓储通信电台的失效率,提高了仓储电台的完好率。  相似文献   
10.
电网的安全水平主要取决于其使用产品的质量是否过关。如果产品的质量较好,则能建造出优质的电网,电网的安全水平便会随之提高。因此,应加强对产品质量的监督管理,从而提高电网的安全水平。我们可建立质量监督管理系统,及时抽检出质量不过关的产品,从而消除电网运行过程中潜在的安全隐患。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号