全文获取类型
收费全文 | 5991篇 |
免费 | 476篇 |
国内免费 | 118篇 |
专业分类
电工技术 | 288篇 |
综合类 | 202篇 |
化学工业 | 1033篇 |
金属工艺 | 205篇 |
机械仪表 | 188篇 |
建筑科学 | 363篇 |
矿业工程 | 50篇 |
能源动力 | 327篇 |
轻工业 | 473篇 |
水利工程 | 103篇 |
石油天然气 | 185篇 |
武器工业 | 4篇 |
无线电 | 697篇 |
一般工业技术 | 913篇 |
冶金工业 | 375篇 |
原子能技术 | 29篇 |
自动化技术 | 1150篇 |
出版年
2023年 | 106篇 |
2022年 | 154篇 |
2021年 | 233篇 |
2020年 | 192篇 |
2019年 | 182篇 |
2018年 | 236篇 |
2017年 | 211篇 |
2016年 | 262篇 |
2015年 | 236篇 |
2014年 | 252篇 |
2013年 | 483篇 |
2012年 | 356篇 |
2011年 | 449篇 |
2010年 | 368篇 |
2009年 | 362篇 |
2008年 | 314篇 |
2007年 | 250篇 |
2006年 | 253篇 |
2005年 | 199篇 |
2004年 | 134篇 |
2003年 | 155篇 |
2002年 | 198篇 |
2001年 | 144篇 |
2000年 | 101篇 |
1999年 | 61篇 |
1998年 | 92篇 |
1997年 | 72篇 |
1996年 | 62篇 |
1995年 | 62篇 |
1994年 | 56篇 |
1993年 | 40篇 |
1992年 | 30篇 |
1991年 | 13篇 |
1990年 | 20篇 |
1989年 | 16篇 |
1988年 | 20篇 |
1987年 | 16篇 |
1986年 | 16篇 |
1985年 | 10篇 |
1984年 | 27篇 |
1983年 | 11篇 |
1982年 | 16篇 |
1981年 | 12篇 |
1980年 | 7篇 |
1979年 | 10篇 |
1978年 | 12篇 |
1977年 | 10篇 |
1976年 | 15篇 |
1975年 | 11篇 |
1973年 | 6篇 |
排序方式: 共有6585条查询结果,搜索用时 31 毫秒
101.
Syrine Neffati Khaoula Ben Abdellafou Ines Jaffel Okba Taouali Kais Bouzrara 《International journal of imaging systems and technology》2019,29(2):121-131
Alzheimer's disease (AD), a neurodegenerative disorder, is a very serious illness that cannot be cured, but the early diagnosis allows precautionary measures to be taken. The current used methods to detect Alzheimer's disease are based on tests of cognitive impairment, which does not provide an exact diagnosis before the patient passes a moderate stage of AD. In this article, a novel classifier of brain magnetic resonance images (MRI) based on the new downsized kernel principal component analysis (DKPCA) and multiclass support vector machine (SVM) is proposed. The suggested scheme classifies AD MRIs. First, a multiobjective optimization technique is used to determine the optimal parameter of the kernel function in order to ensure good classification results and to minimize the number of retained principle components simultaneously. The optimal parameter is used to build the optimized DKPCA model. Second, DKPCA is applied to normalized features. Downsized features are then fed to the classifier to output the prediction. To validate the effectiveness of the proposed method, DKPCA was tested using synthetic data to demonstrate its efficiency on dimensionality reduction, then the DKPCA based technique was tested on the OASIS MRI database and the results were satisfactory compared to conventional approaches. 相似文献
102.
在4G网络建设末期,网络资源投入逐渐减少的情况下,4G网络流量增长趋势依然保持不减且有增长态势。在有限的资源情况下,如何既能够释放被压抑的流量,最大化投资收益,又能够兼顾用户感知,减少业务流失,这是运营商当前面临的主要问题。本文从业务出发,基于用户感知,充分考虑各项负荷指标,建立了一套系统的扩容评估的思路和方法。 相似文献
103.
Mariame Amine Abdellatif Kobbane Jalel Ben‐Othman Abdellaziz Walid 《International Journal of Communication Systems》2020,33(8)
Recently, academic and industrial research communities are paying more explicit attention to the 5G multiple radio access technology ultra‐dense networks (5G multi‐RAT UDNs) for boosting network capacity, especially in UD urban zones. To this aim, in this paper, we intend to tackle the user association problem in 5G multi‐RAT UDNs. By considering the decoupled uplink/downlink access (DUDA), we divide our user association problem into two distinct subproblems representing, respectively, the uplink and the downlink channels. Next, we formulated each one as a nonlinear optimization problem with binary variables. Then, to solve them, we were restricted by the hard complexity, as well as the hard feasibility of centralized user association schemes. Thus, to resolve our user association problem in a reasonable time and distributed manner, we formulated each subproblem as a many‐to‐one matching game based on matching theory. Next, we provide two fully distributed association algorithms to compute the uplink and downlink stable matching among user equipments (UEs) and base stations (BSs). Simulation results corroborate our theoretical model and show the effectiveness and improvement of our achieved results in terms of the overall network performance, quality of service (QoS), and energy efficiency (EE) of UEs. 相似文献
104.
Ivan G. Clayson Daniel Hewitt Martin Hutereau Tom Pope Ben Slater 《Advanced materials (Deerfield Beach, Fla.)》2020,32(44):2002780
Porous materials are widely employed in a large range of applications, in particular, for storage, separation, and catalysis of fine chemicals. Synthesis, characterization, and pre- and post-synthetic computer simulations are mostly carried out in a piecemeal and ad hoc manner. Whilst high throughput approaches have been used for more than 30 years in the porous material fields, routine integration of experimental and computational processes is only now becoming more established. Herein, important developments are highlighted and emerging challenges for the community identified, including the need to work toward more integrated workflows. 相似文献
105.
106.
107.
108.
109.
110.
Scientometrics - This research letter discusses whether Arab Spring explains the changes in research productivity and impact of Arab countries by identifying non-sociopolitical factors that can be... 相似文献