全文获取类型
收费全文 | 9360篇 |
免费 | 767篇 |
国内免费 | 625篇 |
专业分类
电工技术 | 233篇 |
技术理论 | 13篇 |
综合类 | 1270篇 |
化学工业 | 239篇 |
金属工艺 | 47篇 |
机械仪表 | 144篇 |
建筑科学 | 1343篇 |
矿业工程 | 153篇 |
能源动力 | 66篇 |
轻工业 | 457篇 |
水利工程 | 208篇 |
石油天然气 | 49篇 |
武器工业 | 11篇 |
无线电 | 751篇 |
一般工业技术 | 625篇 |
冶金工业 | 2918篇 |
原子能技术 | 16篇 |
自动化技术 | 2209篇 |
出版年
2023年 | 141篇 |
2022年 | 199篇 |
2021年 | 339篇 |
2020年 | 367篇 |
2019年 | 334篇 |
2018年 | 320篇 |
2017年 | 365篇 |
2016年 | 390篇 |
2015年 | 446篇 |
2014年 | 593篇 |
2013年 | 682篇 |
2012年 | 546篇 |
2011年 | 664篇 |
2010年 | 558篇 |
2009年 | 557篇 |
2008年 | 531篇 |
2007年 | 493篇 |
2006年 | 480篇 |
2005年 | 435篇 |
2004年 | 366篇 |
2003年 | 327篇 |
2002年 | 296篇 |
2001年 | 248篇 |
2000年 | 96篇 |
1999年 | 70篇 |
1998年 | 38篇 |
1997年 | 36篇 |
1995年 | 21篇 |
1994年 | 28篇 |
1993年 | 23篇 |
1992年 | 27篇 |
1990年 | 31篇 |
1989年 | 19篇 |
1988年 | 25篇 |
1987年 | 20篇 |
1986年 | 20篇 |
1984年 | 18篇 |
1966年 | 26篇 |
1965年 | 28篇 |
1964年 | 56篇 |
1963年 | 46篇 |
1962年 | 18篇 |
1961年 | 43篇 |
1960年 | 22篇 |
1959年 | 30篇 |
1958年 | 22篇 |
1957年 | 33篇 |
1956年 | 24篇 |
1955年 | 45篇 |
1954年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 20 毫秒
1.
《The Electricity Journal》2019,32(5):35-37
With the increase in stakeholders in the regulatory process, it has become more difficult for regulators to protect utility-customer interests. Requiring utilities to expand their role in serving society has caused regulators to consider other objectives other than setting just and reasonable rates and assuring reliable utility service. 相似文献
2.
3.
Lorenzo Zallocco Laura Giusti Maurizio Ronci Andrea Mussini Marco Trerotola Maria Rosa Mazzoni Antonio Lucacchini Laura Sebastiani 《International journal of molecular sciences》2021,22(9)
The autonomic nervous system (ANS) plays a crucial role both in acute and chronic psychological stress eliciting changes in many local and systemic physiological and biochemical processes. Salivary secretion is also regulated by ANS. In this study, we explored salivary proteome changes produced in thirty-eight University students by a test stress, which simulated an oral exam. Students underwent a relaxation phase followed by the stress test during which an electrocardiogram was recorded. To evaluate the effect of an olfactory stimulus, half of the students were exposed to a pleasant odor diffused in the room throughout the whole session. Saliva samples were collected after the relaxation phase (T0) and the stress test (T1). State anxiety was also evaluated at T0 and T1. Salivary proteins were separated by two-dimensional electrophoresis, and patterns at different times were compared. Spots differentially expressed were trypsin digested and identified by mass spectrometry. Western blot analysis was used to validate proteomic results. Anxiety scores and heart rate changes indicated that the fake exam induced anxiety. Significant changes of α-amylase, polymeric immunoglobulin receptor (PIGR), and immunoglobulin α chain (IGHA) secretion were observed after the stress test was performed in the two conditions. Moreover, the presence of pleasant odor reduced the acute social stress affecting salivary proteome changes. Therefore, saliva proteomic analysis was a useful approach to evaluate the rapid responses associated to an acute stress test also highlighting known biomarkers. 相似文献
4.
Clive Bell 《Papers in Regional Science》2022,101(2):373-397
The effects of a rural roads programme depend on labour mobility, how the programme is financed, and agglomeration economies. If financed by a rural poll tax and cross-price effects and agglomeration economies are sufficiently small, the wage will rise, with some return migration. Taxes on trade act as countervailing distortions, yielding urban households some relief. Rural-urban commuting promotes the exploitation of agglomeration economies; taxes on international trade are then inferior to a poll tax. The change in the value, at producer prices, of the rural sector's net supply vector can be a poor measure of the programme's social profitability. 相似文献
5.
6.
基于位置社交网络的兴趣点推荐越来越受到工业界和学术界的关注。由于用户签到数据集的稀疏性以及签到地理位置的聚集性,使得目前的推荐算法效率普遍不高,特别是当用户外出到新的地点时,推荐效果更是急剧下降。因此本文提出了一种基于用户-区域-内容主题的多特征联合推荐算法(UCRTM),以隐主题模型为基础,在统一的框架下利用隐含因子关联性融合了用户的偏好、兴趣点的内容以及兴趣点所属地理区域主题等信息来进行推荐,使得用户无论身处何地,都能获得理想的推荐服务。本文在两种真实的数据集上进行了实验,结果表明该方法不仅能够克服数据的稀疏性以及弱语义性等问题,而且与其他方法相比具有更高的推荐准确率。 相似文献
7.
8.
卡那霉素是一种氨基糖苷类抗生素,具有广谱抗菌性,在动物医疗中应用广泛,从而导致了其在动物源性食品中广泛残留,因此检测食品中卡那霉素的残留很有必要。作者以多壁碳纳米管(Multiwalled Carbon Nanotubes,MWCNTs)作为载体,通过EDC/NHS方法偶联抗体与信号分子辣根过氧化物酶(Horseradish Peroxidase,HRP),合成多酶复合颗粒MWCNTs-Abs-HRP;建立基于MWCNTs-Abs-HRP多酶复合颗粒的检测方法,相比于已建立的传统竞争ELISA,灵敏度提高约5倍;并成功将此方法应用于牛奶样本中卡那霉素的检测。 相似文献
9.
Debadyuti Das 《国际生产研究杂志》2018,56(17):5776-5794
The present work is an attempt to investigate the adoption of sustainable supply chain management (SSCM) practices amongst manufacturing and process based organisations in India and its impact on organisational performance encompassing all three dimensions of sustainability. SSCM practices conceived in the present study include environmental management practices (EMP), socially inclusive practices for employees (SPE), socially inclusive practices for community (SPC), operations practices (OP) and supply chain integration (SCI) which were treated as exogenous variables. Organisational performance considered in this study includes five dimensions, namely environmental performance (EPR), employee-centred social performance (ESP), community-centred social performance (CSP), operations performance (OPR) and competitiveness, which were regarded as endogenous variables. The analysis was carried out with the help of structural equation modelling considering natural logarithm of manpower as a control variable. Few major findings are mentioned. EMP does not have any significant association with OPR, nor does it result in competitiveness. However, when jointly mediated through both EPR and OPR, EMP leads to competitiveness. SPC has significant negative association with competitiveness, when only direct relationship is considered. However, indirect relationship between SPC and competitiveness shows significant positive association when mediated through CSP. The resultant total effect between SPC and competitiveness turns out to be insignificant. Further, OPR fully mediates the relationship between OP and competitiveness. Managerial implications of the findings are discussed. 相似文献
10.
Yuting Shang Jiadi Sun Yongli Ye Jumei Zhang Yinzhi Zhang 《Critical reviews in food science and nutrition》2020,60(2):201-224
AbstractDue to the significant growth of food production, the potential likelihood of food contamination is increasing. Foodborne illness caused by bacterial pathogens has considerably increased over the past decades, while at the same time, the species of harmful microorganisms also varied. Conventional bacterial culturing methods have been unable to satisfy the growing requirement for food safety inspections and food quality assurance. Therefore, rapid and simple detection methods are urgently needed. The loop-mediated isothermal amplification (LAMP) technology is a highly promising approach for the rapid and sensitive detection of pathogens, which allows nucleic acid amplification under isothermal conditions. The integration of the LAMP assay onto a microfluidic chip is highly compatible with point-of-care or resource-limited settings, as it offers the capability to perform experiments in combination with high screening efficiency. Here, we provide an overview of recent advances in LAMP-based microfluidic chip technology for detecting pathogens, based on real-time or endpoint determination mechanisms. We also discuss the promoting aspects of using the LAMP technique in a microfluidic platform, to supply a guideline for further molecular diagnosis and genetic analysis. 相似文献