全文获取类型
收费全文 | 7684篇 |
免费 | 1225篇 |
国内免费 | 599篇 |
专业分类
电工技术 | 349篇 |
综合类 | 804篇 |
化学工业 | 572篇 |
金属工艺 | 173篇 |
机械仪表 | 463篇 |
建筑科学 | 489篇 |
矿业工程 | 181篇 |
能源动力 | 87篇 |
轻工业 | 1099篇 |
水利工程 | 205篇 |
石油天然气 | 204篇 |
武器工业 | 96篇 |
无线电 | 1450篇 |
一般工业技术 | 548篇 |
冶金工业 | 796篇 |
原子能技术 | 174篇 |
自动化技术 | 1818篇 |
出版年
2024年 | 28篇 |
2023年 | 173篇 |
2022年 | 284篇 |
2021年 | 373篇 |
2020年 | 350篇 |
2019年 | 330篇 |
2018年 | 261篇 |
2017年 | 323篇 |
2016年 | 290篇 |
2015年 | 367篇 |
2014年 | 486篇 |
2013年 | 514篇 |
2012年 | 615篇 |
2011年 | 592篇 |
2010年 | 497篇 |
2009年 | 486篇 |
2008年 | 472篇 |
2007年 | 568篇 |
2006年 | 425篇 |
2005年 | 352篇 |
2004年 | 304篇 |
2003年 | 271篇 |
2002年 | 211篇 |
2001年 | 159篇 |
2000年 | 112篇 |
1999年 | 107篇 |
1998年 | 62篇 |
1997年 | 82篇 |
1996年 | 77篇 |
1995年 | 62篇 |
1994年 | 55篇 |
1993年 | 28篇 |
1992年 | 25篇 |
1991年 | 21篇 |
1990年 | 27篇 |
1989年 | 16篇 |
1988年 | 19篇 |
1987年 | 14篇 |
1986年 | 11篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1966年 | 2篇 |
1963年 | 2篇 |
1956年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有9508条查询结果,搜索用时 15 毫秒
41.
测试性是装备通用质量特性之一,其设计水平直接影响了装备保障效能的发挥,如何更加真实的评估装备的测试性水平是当前研究的热点。在研制阶段装备实物测试性试验数据数量少、获取难、费用高,可认为是“小子样”数据,为了更加全面客观地评价装备的测试性水平,需要充分利用测试性仿真试验获取仿真数据进行融合评估。进行测试性仿真试验时,研究电子装备的仿真模型、故障模型、仿真故障注入方法,获取测试性仿真数据;在此基础上,将仿真试验数据作为验前信息并进行的处理,结合“小子样”装备实物试验数据,采用贝叶斯方法进行测试性试验数据的融合来评估装备的测试性水平,提高评估结果的客观性和可信度。通过案例分析,验证了测试性融合评估方法的有效性。 相似文献
42.
脑电波是一种复杂的生物电信号,可反应出大脑内部的活动及注意力等精神状态。基于此,论文设计了注意力相关的脑电实验,并完成了受试者脑电数据的采集,对所采集的脑电数据分别从以下两种角度进行研究:从时频分析的角度,采用db4小波基对原始脑电信号进行7层小波包分解,提取了β波/θ波能量占比作为特征量;从非线性动力学的角度,提取脑电信号的样本熵作为特征,并分别对各受试者进行注意力的分级研究。通过对比分析,结果表明两者都能从一定程度上表征注意力水平的状况,但样本熵对于多级注意力的区分度更好。 相似文献
43.
The Miao nationality is the sixth largest ethnic group in China which has a history of thousands of years. It has created a unique material culture and spiritual culture in its development process and the Miao costume is a highly condensed collection of the material and spiritual culture of the Miao nationality. As one of the unique symbols of Miao culture the Miao costume has profound cultural heritage and cultural connotations. The patterns of the Miao costume are particularly eye-catching as they not only symbolize the wisdom of the Miao people in thousands of years of production and life but also symbolize the pursuit of the good spirit of the Miao people. However under the impact of modern pop culture and foreign culture these cultural symbols are gradually disappearing. In order to protect and inherit them the Miao costume pattern segmentation has become the most important work. However the Miao costume pattern segmentation is quite difficult. At present there are few studies on the extraction classification identification and preservation of the features of Miao costume pattern segmentation. With the excellent segmentation performance of the U-Net model and the advantages of easy deployment the paper improves the basic structure of the U-Net model and proposes a Miao costume pattern segmentation algorithm based on the RSKP-UNet Residual Selective-Kernel Parallel U-Net model. The algorithm adds Residual modules in the encoder part of the U-Net model to improve the feature extraction capability of the model and embeds the SKNet modules and ParNet modules in the decoder part to enhance the feature expression capability of the model. The paper uses evaluation metrics to measure the segmentation performance of the model and compares it with four segmentation models based on deep learning. The paper not only combines the current research focus-deep learning and attention mechanism but also introduces the Lovász-hinge loss function to effectively solve the problem of class imbalance in the Miao costume patterns. The RSKP-UNet model is better than other models in various segmentation indicators. Compared with the benchmark model U-Net the Dice coefficient IoU precision recall and accuracy are improved by 6. 98% 11. 07% 2. 89% 6. 75% and 3. 92% . The segmentation algorithm proposed in this paper realizes the extraction of the element content of the Miao costume patterns through image segmentation of Miao costume patterns which can be used to build the Miao costume pattern database in this way thus helping designers relevant researchers and organizations to provide research foundation and completing the protection and inheritance of the Miao costume culture. The paper also provides some reference for the segmentation research of other minority costume patterns. © 2022 Authors. All rights reserved. 相似文献
44.
Scientists and engineers’ social background, cultural upbringing, educational training, and world outlook influence how they perform the work and interact with their colleagues. We conducted a study on Indian immigrant scientists and engineers employed in the US industrial sector. We interviewed 40 Indian immigrant scientists and engineers, some of whom came for higher studies and found employment after graduation, while others came directly from India to work. Findings show that the overwhelming majority of interviewees (n = 35) noted significant cultural differences with their colleagues in the workplace; only a small number of interviewees (n = 5), believed that their foundation in professionalism eliminated significant impacts from cultural dissimilarities. Interviewees identified cultural differences in the areas of social interactions, work-related practices, intercultural communication, and management. When immigrant scientists and engineers from developing countries join industrial organizations, they do not leave their cultural practices at home. A conversation with Indian immigrant scientists and engineers shows how Indian culture manifests itself in the workplace. 相似文献
45.
利用物理复合的方法制备聚丙烯酰胺(PAM)-聚硅酸锌(PSZ)复合絮凝剂。结果表明,聚丙烯酰胺-聚硅酸锌絮凝剂在复配比例为V (PAM): V (PSZ)=1.0、投加量为0.10 mL、模拟水样pH为8左右时,对高岭土模拟废水絮凝效果最好,脱色率达91.2%,均高于聚丙烯酰胺和聚硅酸锌单独使用的效果(最高脱色率分别达87.66%和89.78%);而且,在中性和碱性范围内,这种复合絮凝剂受pH影响较小。三种絮凝剂应用于四种工业废水的脱色处理结果表明,聚丙烯酰胺-聚硅酸锌复合絮凝剂的脱色率也均比单一絮凝剂要高。 相似文献
46.
47.
48.
M. George 《Construction Management & Economics》2019,37(8):419-432
There is a widely accepted assumption in the construction literature that the industry is highly masculinised. However, there has been a surprising lack of empirical evidence around workers’ own attitudes towards masculinity in the sector. Addressing this lack of research, a survey to measure construction site operatives’ attitudes towards traditional masculinity ideology was undertaken in Australia using the Male Role Norms Inventory Scale-Short Form (MRNI-SF). It is found that the focus of attitudes towards masculinity in the construction industry may be shifting to reflect trends in the wider population and may be more inclusive and less hegemonic than has been previously argued. It is also found that the focus of masculinity in the construction industry is closely related to the physical and high-risk nature of work and that sexuality and humour may also be an important source of masculine identity. These results are important since they contribute a more nuanced understanding of the dimensions and exact nature of attitudes towards masculinity in the construction industry. It is concluded that future research into the impact of masculinity in areas such as gender diversity, safety and mental health would benefit from a more inclusive theoretical lens which recognises the dynamic nature of masculinity and which highlights the institutional legacies of past hegemonies that have to be challenged to move the industry forward. 相似文献
49.
Dragos Horvath Michael Lisurek Bernd Rupp Ronald Kühne Edgar Specker Jens von Kries Didier Rognan C. David Andersson Fredrik Almqvist Mikael Elofsson Per‐Anders Enqvist Anna‐Lena Gustavsson Nikita Remez Jordi Mestres Gilles Marcou Alexander Varnek Marcel Hibert Jordi Quintana Ronald Frank 《ChemMedChem》2014,9(10):2309-2326
This work describes a collaborative effort to define and apply a protocol for the rational selection of a general‐purpose screening library, to be used by the screening platforms affiliated with the EU‐OPENSCREEN initiative. It is designed as a standard source of compounds for primary screening against novel biological targets, at the request of research partners. Given the general nature of the potential applications of this compound collection, the focus of the selection strategy lies on ensuring chemical stability, absence of reactive compounds, screening‐compliant physicochemical properties, loose compliance to drug‐likeness criteria (as drug design is a major, but not exclusive application), and maximal diversity/coverage of chemical space, aimed at providing hits for a wide spectrum of drugable targets. Finally, practical availability/cost issues cannot be avoided. The main goal of this publication is to inform potential future users of this library about its conception, sources, and characteristics. The outline of the selection procedure, notably of the filtering rules designed by a large committee of European medicinal chemists and chemoinformaticians, may be of general methodological interest for the screening/medicinal chemistry community. The selection task of 200K molecules out of a pre‐filtered set of 1.4M candidates was shared by five independent European research groups, each picking a subset of 40K compounds according to their own in‐house methodology and expertise. An in‐depth analysis of chemical space coverage of the library serves not only to characterize the collection, but also to compare the various chemoinformatics‐driven selection procedures of maximal diversity sets. Compound selections contributed by various participating groups were mapped onto general‐purpose self‐organizing maps (SOMs) built on the basis of marketed drugs and bioactive reference molecules. In this way, the occupancy of chemical space by the EU‐OPENSCREEN library could be directly compared with distributions of known bioactives of various classes. This mapping highlights the relevance of the selection and shows how the consensus reached by merging the five different 40K selections contributes to achieve this relevance. The approach also allows one to readily identify subsets of target‐ or target‐class‐oriented compounds from the EU‐OPENSCREEN library to suit the needs of the diverse range of potential users. The final EU‐OPENSCREEN library, assembled by merging five independent selections of 40K compounds from various expert groups, represents an excellent example of a Europe‐wide collaborative effort toward the common objective of building best‐in‐class European open screening platforms. 相似文献
50.
自然圣境(sacred natural sites,简称SNS)是自然保护地体系的重要构成,也是典型的文化景观。它们作为人与自然互动的历史记录,所蕴藏的文化价值是其赖以存在的根基。从单纯的自然保护到融合文化价值的整体性保护,反观国外SNS保护工作的方向性转变,有助于在全球发展主义时代背景下从"术"的层面重新审视中国SNS保护工作中面临的诸多挑战,对于推进中国生态文明建设具有重大意义。从世界遗产角度,在阐述SNS概念的基础上,全面梳理不同国际组织机构参与下的SNS保护实践进展;总结目前在其保护中涉及的景观方法和生物文化多样性方法等主流保护方法;最后指出在国家公园体制背景下,充分开展本土SNS基础调研,完善相关规划并确立保护条例,在遗产地可持续发展的基础上协调SNS中的人际间及人与其他物种的公平关系是中国SNS保护成功的关键。 相似文献