全文获取类型
收费全文 | 4290篇 |
免费 | 227篇 |
国内免费 | 89篇 |
专业分类
电工技术 | 126篇 |
技术理论 | 3篇 |
综合类 | 376篇 |
化学工业 | 841篇 |
金属工艺 | 83篇 |
机械仪表 | 225篇 |
建筑科学 | 468篇 |
矿业工程 | 146篇 |
能源动力 | 197篇 |
轻工业 | 319篇 |
水利工程 | 55篇 |
石油天然气 | 102篇 |
武器工业 | 14篇 |
无线电 | 199篇 |
一般工业技术 | 380篇 |
冶金工业 | 434篇 |
原子能技术 | 27篇 |
自动化技术 | 611篇 |
出版年
2024年 | 7篇 |
2023年 | 62篇 |
2022年 | 80篇 |
2021年 | 132篇 |
2020年 | 162篇 |
2019年 | 79篇 |
2018年 | 79篇 |
2017年 | 81篇 |
2016年 | 118篇 |
2015年 | 115篇 |
2014年 | 244篇 |
2013年 | 246篇 |
2012年 | 235篇 |
2011年 | 303篇 |
2010年 | 239篇 |
2009年 | 242篇 |
2008年 | 198篇 |
2007年 | 240篇 |
2006年 | 260篇 |
2005年 | 213篇 |
2004年 | 191篇 |
2003年 | 163篇 |
2002年 | 156篇 |
2001年 | 114篇 |
2000年 | 83篇 |
1999年 | 78篇 |
1998年 | 70篇 |
1997年 | 61篇 |
1996年 | 47篇 |
1995年 | 40篇 |
1994年 | 41篇 |
1993年 | 24篇 |
1992年 | 15篇 |
1991年 | 13篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1988年 | 11篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 15篇 |
1983年 | 14篇 |
1982年 | 8篇 |
1966年 | 6篇 |
1965年 | 8篇 |
1964年 | 12篇 |
1961年 | 8篇 |
1959年 | 6篇 |
1958年 | 6篇 |
1957年 | 8篇 |
1955年 | 8篇 |
排序方式: 共有4606条查询结果,搜索用时 15 毫秒
101.
102.
Learning often occurs through comparing. In classification learning, in order to compare data groups, most existing methods compare either raw instances or learned classification rules against each other. This paper takes a different approach, namely conceptual equivalence, that is, groups are equivalent if their underlying concepts are equivalent while their instance spaces do not necessarily overlap and their rule sets do not necessarily present the same appearance. A new methodology of comparing is proposed that learns a representation of each group’s underlying concept and respectively cross-exams one group’s instances by the other group’s concept representation. The innovation is fivefold. First, it is able to quantify the degree of conceptual equivalence between two groups. Second, it is able to retrace the source of discrepancy at two levels: an abstract level of underlying concepts and a specific level of instances. Third, it applies to numeric data as well as categorical data. Fourth, it circumvents direct comparisons between (possibly a large number of) rules that demand substantial effort. Fifth, it reduces dependency on the accuracy of employed classification algorithms. Empirical evidence suggests that this new methodology is effective and yet simple to use in scenarios such as noise cleansing and concept-change learning. 相似文献
103.
华铨平 《数字社区&智能家居》2009,(2)
根据家纺产品分销的业务范围和操作流程,结合基于组件的多层应用开发技术,提出了适合家纺产品分销管理的系统解决方案,较好地实现了家纺产品分销中的一些业务流程。该文详细阐述了家纺分销管理系统的设计与实现。 相似文献
104.
针对知识在非正式团体中的传播特征,结合复杂网络理论,为了企业知识不断创新,提出了一种非正式团体知识交互网络模型.通过仿真得出,在小世界网络模型下知识的传播速度和平均知识水平比其他网络模型有明显优势,进而在非正式团体知识交互网络的描述与分析中提出利用"小世界"的平均路径长度和聚类系数来表征IFG知识交互网络中的交互频繁度和交互聚集度的思想,为进一步研究IFG组织及管理与其内部知识创新的内在联系提供了数量分析基础. 相似文献
105.
随着Web信息的急剧增长使搜索引擎专用化成为发展趋势.根据当前的需求提出了实现建筑业信息搜索引擎设计方法.重点论述主题搜索引擎的信息采集策略,并给出了一种比较理想的建筑业信息搜索引擎设计方案. 相似文献
106.
Norbert Kuhn Klaus Madlener Friedrich Otto 《Applicable Algebra in Engineering, Communication and Computing》1994,5(5):287-316
Algorithms for solving uniform decision problems for algebraic structures crucially depend on the chosen finite presentations for the structures under consideration. Rewriting techniques have been used very successfully to solve uniform decision problems, when the presentations considered involve finite, noetherian, and ()-confluent rewriting systems. Whenever the class of algebraic structures considered is closed under the operation of taking finitely generated substructures, then the algorithms for solving the uniform decision problems can be applied to the substructures as well. However, since these algorithms depend on the form of the presentations, this involves the task of constructing a presentation of a certain form for a substructure given a presentation of this form for the structure itself and a finite set of generating elements for the substructure.This problem, which has received a lot of attention in algebra, is here investigated from an algorithmic point of view. The structures considered are the following two classes of groups, which have been studied extensively before: the polycyclic groups and the context-free groups.Finitely generated context-free groups can be presented by finite, monadic, and -confluent string-rewriting systems. Due to their nice algorithmic properties these systems provide a way to effectively solve many decision problems for context-free groups. Since finitely generated subgroups of context-free groups are again contextfree, they can be presented in the same way. Here we describe a process that, from a finite, monadic, and -confluent string-rewriting system presenting a context-free groupG and a finite subsetU ofG, determines a presentation of this form for the subgroup U ofG that is generated byU. For finitely presented polycyclic groups we obtain an analogous result, when we use finite confluent PCP2-presentations to describe these groups.This work was performed while this author was visiting at the Fachbereich Informatik, Universität Kaiserslautern, during his sabbatical 1991/92 相似文献
107.
108.
Akram Tavakoli Ali Akbar Babaluo Khadijeh Safaee 《Fullerenes, Nanotubes and Carbon Nanostructures》2017,25(5):312-317
In this work, multi-wall carbon nanotube (MWCNT) was successfully modified using aqueous solution of Oxone as a new oxidant. The effect of oxidation temperature on various characteristics of the treated MWCNTs was also investigated. FTIR and titration analysis proved the formation of carboxyl, carbonyl and epoxide groups at the surface of MWCNTs. The concentration of the functional groups increased as the modification temperature increased. The presence of such oxygen containing groups at the surface of MWCNTs justified the long time stability of the treated MWCNTs suspensions in water and methanol. The modified MWCNTs showed higher entanglement compared to row MWCNT due to the cross-links adjacent effect of pendant functional groups. Finally, it was concluded that Oxone oxidation process destroys the structure of the MWCNTs, but not severe enough to unzip the MWCNTs. 相似文献
109.
A Phase‐Separation Route to Synthesize Porous CNTs with Excellent Stability for Na+ Storage
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)
Zhi Chen Taihong Wang Ming Zhang Guozhong Cao 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(22)
Porous carbon nanotubes (CNTs) are obtained by removing MoO2 nanoparticles from MoO2@C core@shell nanofibers which are synthesized by phase‐segregation via a single‐needle electrospinning method. The specific surface area of porous CNTs is 502.9 m2 g?1, and many oxygen‐containing functional groups (C? OH, C?O) are present. As anodes for sodium‐ion batteries, the porous CNT electrode displays excellent rate performance and cycling stability (110 mA h g?1 after 1200 cycles at 5 A g?1). Those high properties can be attributed to the porous structure and surface modification to steadily store Na+ with high capacity. The work provides a facile and broadly applicable way to fabricate the porous CNTs and their composites for batteries, catalysts, and fuel cells. 相似文献
110.
Khalid A. Alissa Mohammed Maray Areej A. Malibari Sana Alazwari Hamed Alqahtani Mohamed K. Nour Marwa Obbaya Mohamed A. Shamseldin Mesfer Al Duhayyim 《计算机、材料和连续体(英文)》2023,74(3):5349-5367
Emerging technologies such as edge computing, Internet of Things (IoT), 5G networks, big data, Artificial Intelligence (AI), and Unmanned Aerial Vehicles (UAVs) empower, Industry 4.0, with a progressive production methodology that shows attention to the interaction between machine and human beings. In the literature, various authors have focused on resolving security problems in UAV communication to provide safety for vital applications. The current research article presents a Circle Search Optimization with Deep Learning Enabled Secure UAV Classification (CSODL-SUAVC) model for Industry 4.0 environment. The suggested CSODL-SUAVC methodology is aimed at accomplishing two core objectives such as secure communication via image steganography and image classification. Primarily, the proposed CSODL-SUAVC method involves the following methods such as Multi-Level Discrete Wavelet Transformation (ML-DWT), CSO-related Optimal Pixel Selection (CSO-OPS), and signcryption-based encryption. The proposed model deploys the CSO-OPS technique to select the optimal pixel points in cover images. The secret images, encrypted by signcryption technique, are embedded into cover images. Besides, the image classification process includes three components namely, Super-Resolution using Convolution Neural Network (SRCNN), Adam optimizer, and softmax classifier. The integration of the CSO-OPS algorithm and Adam optimizer helps in achieving the maximum performance upon UAV communication. The proposed CSODL-SUAVC model was experimentally validated using benchmark datasets and the outcomes were evaluated under distinct aspects. The simulation outcomes established the supreme better performance of the CSODL-SUAVC model over recent approaches. 相似文献