全文获取类型
收费全文 | 99020篇 |
免费 | 16328篇 |
国内免费 | 11105篇 |
专业分类
电工技术 | 7155篇 |
技术理论 | 3篇 |
综合类 | 10516篇 |
化学工业 | 3632篇 |
金属工艺 | 2374篇 |
机械仪表 | 5940篇 |
建筑科学 | 6968篇 |
矿业工程 | 3034篇 |
能源动力 | 1311篇 |
轻工业 | 2075篇 |
水利工程 | 1620篇 |
石油天然气 | 3202篇 |
武器工业 | 730篇 |
无线电 | 15330篇 |
一般工业技术 | 6743篇 |
冶金工业 | 5192篇 |
原子能技术 | 438篇 |
自动化技术 | 50190篇 |
出版年
2024年 | 460篇 |
2023年 | 3279篇 |
2022年 | 5353篇 |
2021年 | 5553篇 |
2020年 | 5186篇 |
2019年 | 3921篇 |
2018年 | 3114篇 |
2017年 | 3373篇 |
2016年 | 4052篇 |
2015年 | 4384篇 |
2014年 | 6399篇 |
2013年 | 5881篇 |
2012年 | 6848篇 |
2011年 | 7669篇 |
2010年 | 6391篇 |
2009年 | 6291篇 |
2008年 | 6308篇 |
2007年 | 6783篇 |
2006年 | 6004篇 |
2005年 | 5364篇 |
2004年 | 4152篇 |
2003年 | 3546篇 |
2002年 | 2894篇 |
2001年 | 2297篇 |
2000年 | 1948篇 |
1999年 | 1521篇 |
1998年 | 1335篇 |
1997年 | 995篇 |
1996年 | 818篇 |
1995年 | 713篇 |
1994年 | 596篇 |
1993年 | 450篇 |
1992年 | 400篇 |
1991年 | 312篇 |
1990年 | 271篇 |
1989年 | 217篇 |
1988年 | 162篇 |
1987年 | 110篇 |
1986年 | 150篇 |
1985年 | 147篇 |
1984年 | 107篇 |
1983年 | 97篇 |
1982年 | 67篇 |
1981年 | 48篇 |
1980年 | 55篇 |
1979年 | 47篇 |
1965年 | 27篇 |
1964年 | 29篇 |
1959年 | 26篇 |
1955年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Recently, a number of classification techniques have been introduced. However, processing large dataset in a reasonable time has become a major challenge. This made classification task more complex and expensive in calculation. Thus, the need for solutions to overcome these constraints such as field programmable gate arrays (FPGAs). In this paper, we give an overview of the various classification techniques. Then, we present the existing FPGA based implementation of these classification methods. After that, we investigate the confronted challenges and the optimizations strategies. Finally, we highlight the hardware accelerator architectures and tools for hardware design suggested to improve the FPGA implementation of classification methods. 相似文献
2.
Smartphones are being used and relied on by people more than ever before. The open connectivity brings with it great convenience and leads to a variety of risks that cannot be overlooked. Smartphone vendors, security policy designers, and security application providers have put a variety of practical efforts to secure smartphones, and researchers have conducted extensive research on threat sources, security techniques, and user security behaviors. Regrettably, smartphone users do not pay enough attention to mobile security, making many efforts futile. This study identifies this gap between technology affordance and user requirements, and attempts to investigate the asymmetric perceptions toward security features between developers and users, between users and users, as well as between different security features. These asymmetric perceptions include perceptions of quality, perceptions of importance, and perceptions of satisfaction. After scoping the range of smartphone security features, this study conducts an improved Kano-based method and exhaustively analyzes the 245 collected samples using correspondence analysis and importance satisfaction analysis. The 14 security features of the smartphone are divided into four Kano quality types and the perceived quality differences between developers and users are compared. Correspondence analysis is utilized to capture the relationship between the perceived importance of security features across different groups of respondents, and results of importance-satisfaction analysis provide the basis for the developmental path and resource reallocation strategy of security features. This article offers new insights for researchers as well as practitioners of smartphone security. 相似文献
3.
Tracking-by-detection (TBD) is a significant framework for visual object tracking. However, current trackers are usually updated online based on random sampling with a probability distribution. The performance of the learning-based TBD trackers is limited by the lack of discriminative features, especially when the background is full of semantic distractors. We propose an attention-driven data augmentation method, in which a residual attention mechanism is integrated into the TBD tracking network as supplementary references to identify discriminative image features. A mask generating network is used to simulate changes in target appearances to obtain positive samples, where attention information and image features are combined to identify discriminative features. In addition, we propose a method for mining hard negative samples, which searches for semantic distractors with the response of the attention module. The experiments on the OTB2015, UAV123, and LaSOT benchmarks show that this method achieves competitive performance in terms of accuracy and robustness. 相似文献
4.
Corey Andrews Yiting Xu Michael Kirberger Jenny J. Yang 《International journal of molecular sciences》2021,22(1)
Calmodulin (CaM) is an important intracellular protein that binds Ca2+ and functions as a critical second messenger involved in numerous biological activities through extensive interactions with proteins and peptides. CaM’s ability to adapt to binding targets with different structures is related to the flexible central helix separating the N- and C-terminal lobes, which allows for conformational changes between extended and collapsed forms of the protein. CaM-binding targets are most often identified using prediction algorithms that utilize sequence and structural data to predict regions of peptides and proteins that can interact with CaM. In this review, we provide an overview of different CaM-binding proteins, the motifs through which they interact with CaM, and shared properties that make them good binding partners for CaM. Additionally, we discuss the historical and current methods for predicting CaM binding, and the similarities and differences between these methods and their relative success at prediction. As new CaM-binding proteins are identified and classified, we will gain a broader understanding of the biological processes regulated through changes in Ca2+ concentration through interactions with CaM. 相似文献
5.
Object detection performed by Autonomous Vehicles (AV)s is a crucial operation that comes ahead of various autonomous driving tasks, such as object tracking, trajectories estimation, and collision avoidance. Dynamic road elements (pedestrians, cyclists, vehicles) impose a greater challenge due to their continuously changing location and behaviour. This paper presents a comprehensive review of the state-of-the-art object detection technologies focusing on both the sensory systems and algorithms used. It begins with a brief introduction on the autonomous driving operations and challenges. Then, different sensory systems employed on existing AVs are elaborated while illustrating their advantages, limitations and applications. Also, sensory systems employed by different research are reviewed. Moreover, due to the significant role Deep Neural Networks (DNN)s are playing in object detection tasks, different DNN-based networks are also highlighted. Afterwards, previous research on dynamic objects detection performed by AVs are reviewed in tabular forms. Finally, a conclusion summarizes the outcomes of the review and suggests future work towards the development of vehicles with higher automation levels. 相似文献
6.
A Quantitative Critical Thinking (QCT) software tool was developed in this study to facilitate students’ learning of quantitative critical thinking via repeated practice by chemical engineering students reading a core module called fluid-solid systems. The software tool generated detailed calculation steps to typical engineering design problems encountered in this module that contained weaknesses, flaws or even errors. Students utilized the software tool to practice identifying these weaknesses, flaws or errors in the design solutions and then present a better or correct design by applying the concepts and knowledge acquired in the module. Since the QCT software tool was built upon an existing design software tool that was able to generate the correct, detailed design calculation steps to design problems, students were able to check their own design calculations against those presented by the software tool during this second learning step, thereby engaging in and learning quantitative critical thinking via a repeated practice approach. The software tool was successful in enhancing the performance of second-year undergraduate students in solving a question that required quantitative critical thinking in the final examination of the module. The average percentage scores achieved by students for the question who reported higher frequencies of usage of the software were generally higher than those who reported lower frequencies of usage or did not utilize the software tool throughout the semester. 相似文献
7.
Elena Vargas-Accarino Carlos Herrera-Montvez Santiago Ramn y Cajal Trond Aasen 《International journal of molecular sciences》2021,22(9)
There is an unmet need for simplified in vitro models of malignancy and metastasis that facilitate fast, affordable and scalable gene and compound analysis. “Adherent” cancer cell lines frequently release “free-floating” cells into suspension that are viable and can reattach. This, in a simplistic way, mimics the metastatic process. We compared the gene expression profiles of naturally co-existing populations of floating and adherent cells in SW620 (colon), C33a (cervix) and HeLa (cervix) cancer cells. We found that 1227, 1367 and 1333 genes were at least 2-fold differentially expressed in the respective cell lines, of which 122 were shared among the three cell lines. As proof of principle, we focused on the anti-metastatic gene NM23-H1, which was downregulated both at the RNA and protein level in the floating cell populations of all three cell lines. Knockdown of NM23-H1 significantly increased the number of floating (and viable) cells, whereas overexpression of NM23-H1 significantly reduced the proportion of floating cells. Other potential regulators of these cellular states were identified through pathway analysis, including hypoxia, mTOR (mechanistic target of rapamycin), cell adhesion and cell polarity signal transduction pathways. Hypoxia, a condition linked to malignancy and metastasis, reduced NM23-H1 expression and significantly increased the number of free-floating cells. Inhibition of mTOR or Rho-associated protein kinase (ROCK) significantly increased cell death specifically in the floating and not the adherent cell population. In conclusion, our study suggests that dynamic subpopulations of free-floating and adherent cells is a useful model to screen and identify genes, drugs and pathways that regulate the process of cancer metastasis, such as cell detachment and anoikis. 相似文献
8.
为推进病历数字化发展,并确保其信息的安全性,将以HIS电子病历系统为基础,采用安信数字签名技术和PKI或PMI系统搭建相信并加以任用的授权服务,经过针对实际的PKC和CA的确认、委托与管控构建整体的数字签名平台,完成电子病历数字签名功能设计,以加强电子文件的完整性、真实性和不可抵赖性。最后以某医院的XML结构化的电子病历系统为基础进行项目实施,完成了医护人员通过HIS的快速身份认证,和准确地数字签名。 相似文献
9.
In the past, thinking of carrying electronic devices inside our bodies was only posed by non-real scenarios. The emergence of insertable devices has changed this. Since this technology is still in its initial development stages, few studies have investigated factors that influence its acceptance. This paper analyzes the predictors of the intention to use non-medical insertable devices in two Latin American contexts. We used partial least squares structural equation modeling to examine whether six constructs predicted intention to use insertable devices. A questionnaire was administered to undergraduate students located in Colombia and Chile (n = 672). We also examined whether these predictors influenced intention differently for both of them. Four common constructs significantly and positively influenced both Chilean and Colombian respondents to use insertable devices (hedonic motivation, habit, performance expectancy, and social influence). Also, the habit has a complementary mediating effect on the relationship between social influence and behavioral intention. By contrast, effort expectations were a positive and significant predictor, but only among Chilean respondents. Findings suggest that when technologies are emerging, well-known predictors of intention (e.g., performance and effort expectations) are less influential than predictors related to self-efficacy (e.g., habit and hedonic motivation). The use of insertable devices has a significant impact on society. Thus, a better understanding of what motivates their use has implications for both academia and industry. 相似文献
10.