全文获取类型
收费全文 | 161531篇 |
免费 | 21949篇 |
国内免费 | 14018篇 |
专业分类
电工技术 | 19757篇 |
技术理论 | 24篇 |
综合类 | 18904篇 |
化学工业 | 13723篇 |
金属工艺 | 3262篇 |
机械仪表 | 8058篇 |
建筑科学 | 8628篇 |
矿业工程 | 3777篇 |
能源动力 | 6920篇 |
轻工业 | 2946篇 |
水利工程 | 3584篇 |
石油天然气 | 3178篇 |
武器工业 | 2028篇 |
无线电 | 27609篇 |
一般工业技术 | 9637篇 |
冶金工业 | 3920篇 |
原子能技术 | 1096篇 |
自动化技术 | 60447篇 |
出版年
2024年 | 746篇 |
2023年 | 2931篇 |
2022年 | 5407篇 |
2021年 | 6228篇 |
2020年 | 6391篇 |
2019年 | 4818篇 |
2018年 | 4153篇 |
2017年 | 4968篇 |
2016年 | 5459篇 |
2015年 | 6230篇 |
2014年 | 10625篇 |
2013年 | 10114篇 |
2012年 | 12134篇 |
2011年 | 12750篇 |
2010年 | 9817篇 |
2009年 | 10355篇 |
2008年 | 10773篇 |
2007年 | 11999篇 |
2006年 | 10423篇 |
2005年 | 9384篇 |
2004年 | 7828篇 |
2003年 | 7030篇 |
2002年 | 5366篇 |
2001年 | 4497篇 |
2000年 | 3639篇 |
1999年 | 2821篇 |
1998年 | 2145篇 |
1997年 | 1763篇 |
1996年 | 1452篇 |
1995年 | 1159篇 |
1994年 | 899篇 |
1993年 | 677篇 |
1992年 | 519篇 |
1991年 | 357篇 |
1990年 | 298篇 |
1989年 | 274篇 |
1988年 | 193篇 |
1987年 | 121篇 |
1986年 | 112篇 |
1985年 | 107篇 |
1984年 | 116篇 |
1983年 | 87篇 |
1982年 | 67篇 |
1981年 | 31篇 |
1980年 | 29篇 |
1979年 | 27篇 |
1966年 | 13篇 |
1964年 | 13篇 |
1959年 | 21篇 |
1951年 | 33篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
铁路在交通运输行业有着举足轻重的地位,一旦列车发生故障将会导致严重的生命财产损失。由于列车发生故障的概率相对较低,因此难以捕获列车的故障样本。针对上述问题,提出了一种无监督学习的列车故障识别方法,通过检测列车音频信号来识别列车故障。该方法基于深度信念网络(DBN),利用小波包分解提取检测信号的特征向量并将其作为DBN的输入,待网络充分训练后,由训练好的DBN识别当前列车的运行状况。现场监测实验结果表明,该方法能够在无监督的条件下有效识别列车故障,保障了列车的运行安全。 相似文献
52.
结合结构支撑理论,探究节点网络结构支持力的一些性质,提出了社交网络结构中的全网支持力和被支持力的总量一致性,并进一步提出计算节点支持力的方法。谣言作为特殊信息,在支持力不同节点之间的传播特性有所不同,借鉴随机游走模型中的PageRank计算方法,对不同节点支持力的谣言传播以及传播后的辟谣状况进行了仿真模拟,结果表明支持力不同的节点对于谣言传播和辟谣影响明显。 相似文献
53.
In this paper, novel computing approach using three different models of feed-forward artificial neural networks (ANNs) are presented for the solution of initial value problem (IVP) based on first Painlevé equation. These mathematical models of ANNs are developed in an unsupervised manner with capability to satisfy the initial conditions exactly using log-sigmoid, radial basis and tan-sigmoid transfer functions in hidden layers to approximate the solution of the problem. The training of design parameters in each model is performed with sequential quadratic programming technique. The accuracy, convergence and effectiveness of the proposed schemes are evaluated on the basis of the results of statistical analyses through sufficient large number of independent runs with different number of neurons in each model as well. The comparisons of these results of proposed schemes with standard numerical and analytical solutions validate the correctness of the design models. 相似文献
54.
Massive Open Online Courses (MOOCs) are becoming an essential source of information for both students and teachers. Noticeably, MOOCs have to adapt to the fast development of new technologies; they also have to satisfy the current generation of online students. The current MOOCs’ Management Systems, such as Coursera, Udacity, edX, etc., use content management platforms where content are organized in a hierarchical structure. We envision a new generation of MOOCs that support interpretability with formal semantics by using the SemanticWeb and the online social networks. Semantic technologies support more flexible information management than that offered by the current MOOCs’ platforms. Annotated information about courses, video lectures, assignments, students, teachers, etc., can be composed from heterogeneous sources, including contributions from the communities in the forum space. These annotations, combined with legacy data, build foundations for more efficient information discovery in MOOCs’ platforms. In this article we review various Collaborative Semantic Filtering technologies for building Semantic MOOCs’ management system, then, we present a prototype of a semantic middle-sized platform implemented at Western Kentucky University that answers these aforementioned requirements. 相似文献
55.
56.
The heat transfer and flow characteristics of MWCNT-R141b nanorefrigerant with different mass fractions have been studied through experiments. Experimental results were compared with existing correlations. A two-step method was used to prepare the nanorefrigerants. Span-80 was used as surfactant with an average particle diameter of 20 nm. Transmittance method was used to evaluate the stability of nanorefrigerants. Results showed that the stability of MWCNT-R141b nanorefrigerant, which is the added dispersant, was good during the experiments. The 0.3 wt% MWCNT-R141b nanorefrigerants had optimal heat transfer enhancement effects compared with pure refrigerants. The maximum Nusselt number increased by 40%. The specific pressure drop of nanorefrigerant increased as the Reynolds number (Re) increased, and the specific pressure drop of the pure refrigerant was minimum, which is similar to R141b. 相似文献
57.
58.
Although greedy algorithms possess high efficiency, they often receive suboptimal solutions of the ensemble pruning problem, since their exploration areas are limited in large extent. And another marked defect of almost all the currently existing ensemble pruning algorithms, including greedy ones, consists in: they simply abandon all of the classifiers which fail in the competition of ensemble selection, causing a considerable waste of useful resources and information. Inspired by these observations, an interesting greedy Reverse Reduce-Error (RRE) pruning algorithm incorporated with the operation of subtraction is proposed in this work. The RRE algorithm makes the best of the defeated candidate networks in a way that, the Worst Single Model (WSM) is chosen, and then, its votes are subtracted from the votes made by those selected components within the pruned ensemble. The reason is because, for most cases, the WSM might make mistakes in its estimation for the test samples. And, different from the classical RE, the near-optimal solution is produced based on the pruned error of all the available sequential subensembles. Besides, the backfitting step of RE algorithm is replaced with the selection step of a WSM in RRE. Moreover, the problem of ties might be solved more naturally with RRE. Finally, soft voting approach is employed in the testing to RRE algorithm. The performances of RE and RRE algorithms, and two baseline methods, i.e., the method which selects the Best Single Model (BSM) in the initial ensemble, and the method which retains all member networks of the initial ensemble (ALL), are evaluated on seven benchmark classification tasks under different initial ensemble setups. The results of the empirical investigation show the superiority of RRE over the other three ensemble pruning algorithms. 相似文献
59.
Fundamental Evaluation of Power Supply and Rectifiers for Wireless Power Transfer Using Magnetic Resonant Coupling 下载免费PDF全文
This paper provides a fundamental analysis of a power supply and rectifiers for wireless power transfer using magnetic resonant coupling (MRC). MRC enables efficient wireless power transfer over middle‐range transfer distances. MRC for wireless power transfer should operate at a high frequency in the industry science medical band, such as 13.56 MHz, because the size of the transfer device decreases at higher transfer frequencies. Therefore, the output frequency of the power supply on the transmitting side should be 13.56 MHz. In addition, the rectifier on the receiving side is operated at a high frequency. This paper focuses on the reflected power in the power supply and rectifiers. Thus, the parametric design method is clarified for the power supply, including a low‐pass filter to match the output, the impedance of the power supply with the characteristic impedance of the transmission line. In addition, the effects on the rectifiers of silicon carbide and gallium nitride diodes are confirmed by performing an experiment and a loss analysis. 相似文献
60.
An integrated approach to measure the cost efficiency of the postal network of Universal Service Provider is proposed. An integrated approach enables the measurement of cost efficiency for delivery and non-delivery postal network units. The proposed approach is verified and tested on the postal network of the selected provider and the results were derived by using Data Envelopment Analysis (DEA). The results show that the main sources of inefficiency are inadequate allocation of resources relative to the network units. In addition, the study indicates that economies of scale have a positive impact on the efficiency of postal network units. 相似文献