全文获取类型
收费全文 | 72785篇 |
免费 | 7909篇 |
国内免费 | 3948篇 |
专业分类
电工技术 | 5964篇 |
技术理论 | 9篇 |
综合类 | 5442篇 |
化学工业 | 10893篇 |
金属工艺 | 4472篇 |
机械仪表 | 4600篇 |
建筑科学 | 5878篇 |
矿业工程 | 2489篇 |
能源动力 | 2215篇 |
轻工业 | 5066篇 |
水利工程 | 1724篇 |
石油天然气 | 3870篇 |
武器工业 | 835篇 |
无线电 | 8368篇 |
一般工业技术 | 8065篇 |
冶金工业 | 3050篇 |
原子能技术 | 983篇 |
自动化技术 | 10719篇 |
出版年
2024年 | 415篇 |
2023年 | 1452篇 |
2022年 | 3022篇 |
2021年 | 3968篇 |
2020年 | 2957篇 |
2019年 | 2247篇 |
2018年 | 2616篇 |
2017年 | 2822篇 |
2016年 | 2590篇 |
2015年 | 3608篇 |
2014年 | 4321篇 |
2013年 | 5043篇 |
2012年 | 5607篇 |
2011年 | 5978篇 |
2010年 | 5132篇 |
2009年 | 4776篇 |
2008年 | 4575篇 |
2007年 | 4113篇 |
2006年 | 3924篇 |
2005年 | 3172篇 |
2004年 | 2181篇 |
2003年 | 1577篇 |
2002年 | 1427篇 |
2001年 | 1154篇 |
2000年 | 1093篇 |
1999年 | 1022篇 |
1998年 | 749篇 |
1997年 | 612篇 |
1996年 | 614篇 |
1995年 | 429篇 |
1994年 | 352篇 |
1993年 | 257篇 |
1992年 | 217篇 |
1991年 | 130篇 |
1990年 | 111篇 |
1989年 | 83篇 |
1988年 | 76篇 |
1987年 | 44篇 |
1986年 | 36篇 |
1985年 | 29篇 |
1984年 | 14篇 |
1983年 | 12篇 |
1982年 | 15篇 |
1981年 | 11篇 |
1980年 | 13篇 |
1979年 | 7篇 |
1976年 | 9篇 |
1975年 | 3篇 |
1959年 | 9篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
101.
Jian‐Peng Cui Feng Zhou Chengqun Song Quan‐Min Zhong Qiong‐Hua Wang 《Journal of the Society for Information Display》2012,20(6):347-350
Abstract— A low‐voltage (~10 Vrms) and high‐transmittance (~90%) polymer‐stabilized blue‐phase liquid‐crystal (BPLC) device with a slanted‐electrodes structure is proposed. Unlike the vertical‐field‐switching (VFS) mode in which oblique incident light and a vertical field are employed, the proposed device utilizes normal incident light and an oblique field. The slanted electrodes generate a strong and uniform oblique electric field, which contributes in obtaining low voltage and high transmittance. Moreover, no couple films or prism sheets are needed, which helps to enhance the optical efficiency and simplify of the device structure. This device has great potential application for emerging BPLC displays and photonic devices. 相似文献
102.
Non-homogeneity detector (NHD) is known for improving the detection performance of space time adaptive processing (STAP) in heterogeneous environment. To mitigate the finite sample effect in the generalized inner product (GIP) based NHD, a new type of GIP detector based on diagonal loading (LGIP) is proposed in this paper. We derive the theoretical mean value of LGIP detector based on random matrix theory. Moreover, an approximation of the theoretical mean value is provided for practical considerations. We then apply the derived theoretical mean value of LGIP to the detection of heterogeneous samples. Finally, by theoretical analysis and numerical simulations, we show the effectiveness of the proposed detector. 相似文献
103.
In this paper, we develop a framework of Question Answering Pages (referred to as QA pages) recommendation. Our proposed framework consists of the two modules: the off-line module to determine the importance of QA pages and the on-line module for on-line QA page recommendation. In the off-line module, we claim that the importance of QA pages could be discovered from user click streams. If the QA pages are of higher importance, many users will click and spend their time on these QA pages. Moreover, the relevant relationships among QA pages are captured by the browsing behavior on these QA pages. As such, we exploit user click streams to model the browsing behavior among QA pages as QA browsing graph structures. The importance of QA pages is derived from our proposed QA browsing graph structures. However, we observe that the QA browsing graph is sparse and that most of the QA pages do not link to other QA pages. This is referred to as a sparsity problem. To overcome this problem, we utilize the latent browsing relations among QA pages to build a QA Latent Browsing Graph. In light of QA latent browsing graph, the importance score of QA pages (referred to as Latent Browsing Rank) and the relevance score of QA pages (referred to as Latent Browsing Recommendation Rank) are proposed. These scores demonstrate the use of a QA latent browsing graph not only to determine the importance of QA pages but also to recommend QA pages. We conducted extensive empirical experiments on Yahoo! Asia Knowledge Plus to evaluate our proposed framework. 相似文献
104.
Seaport container terminals are essential nodes in sea cargo transportation networks. As such, the operational efficiency of container terminals in handling containers passing through them plays a critical role in a globalized world economy. Many models and algorithms have been developed to address various decision problems in container terminals to help improve operational efficiency. These decision support tools are usually used separately for specific purposes. However, the problems they are trying to tackle are often interrelated. Therefore, in this regard, an evaluation tool which can capture as many operational conditions as possible for different decision problems is necessary. This paper introduces a general simulation platform, named MicroPort, which aims to provide an integrated and flexible modeling system for evaluating the operational capability and efficiency of different designs of seaport container terminals. The software structure of MicroPort comprises three programming layers: (1) the Functions layer; (2) the Applications layer; and (3) the Extensions layer. Different layers are bound by Application Programming Interfaces (APIs). Basic functions built in the Functions layer support the Applications layer in which major operation processes can be modeled by an agent-based method. External modules and decision support tools in the Extensions layer then use APIs to adjust the system to produce suitable simulation models for specific purposes. 相似文献
105.
Robust Redundancy Scheme for the Repair Process: Hierarchical Codes in the Bandwidth-Limited Systems
High performance computing can be well supported by the Grid or cloud computing systems. However, these systems have to overcome the failure risks, where data is stored in the “unreliable” storage nodes that can leave the system at any moment and the nodes’ network bandwidth is limited. In this case, the basic way to assure data reliability is to add redundancy using either replication or erasure codes. As compared to replication, erasure codes are more space efficient. Erasure codes break data into blocks, encode these blocks and distribute them into different storage nodes. When storage nodes permanently or temporarily abandon the system, new redundant blocks must be created to guarantee the data reliability, which is referred to as repair. Later when the churn nodes rejoin the system, the blocks stored in these nodes can reintegrate the data group to enhance the data reliability. For “classical” erasure codes, generating a new block requires to transmit a number of k blocks over the network, which brings lots of repair traffic, high computation complexity and high failure probability for the repair process. Then a near-optimal erasure code named Hierarchical Codes, has been proposed that can significantly reduce the repair traffic by reducing the number of nodes participating in the repair process, which is referred to as the repair degree d. To overcome the complexity of reintegration and provide an adaptive reliability for Hierarchical Codes, we refine two concepts called location and relocation, and then propose an integrated maintenance scheme for the repair process. Our experiments show that Hierarchical Code is the most robust redundancy scheme for the repair process as compared to other famous coding schemes. 相似文献
106.
107.
研究中医正骨复位手法,建立虚拟信息系统,但是由于手法的使用形式繁多,实施操作方法经验性强,对操作的技巧性和力度大小要求非常高等原因,使得正骨技术在临床中的应用不易推广,影响着中医正骨复位手法的的继承和发扬。针对上述原因,提出构建虚拟正骨手法复位信息采集系统,通过LabVIEW软件、角度传感器,信息采集卡等硬件设施有机的结合,把抽象的中医骨伤手法复位操作技术用角度、位移参数值具体、直观的表示出来,并以波形图表的形式显示。为初学者认识和学习正骨手法提供了生动形象的教材,改进了传统的教学模式、教学手段和教学方法,进一步促进虚拟技术在中医正骨中的应用。 相似文献
108.
109.
了解认知隧道内的流体力学的特点对于隧道火灾的研究和隧道安全建设有着非常大的意义。为了对隧道火灾的特点进行研究,我们使用商用CFD程序STAR-CD对速度场和压力分布进行了数值模拟。模拟过程中在同一入口位置的情况下改变四个出口位置,出口位置与模具高度的数值对别分别为L/H=0,0.375,0.75,1.125。同时还介绍了对于火灾救援和人员疏散的有效措施。 相似文献
110.