全文获取类型
收费全文 | 14432篇 |
免费 | 1127篇 |
国内免费 | 402篇 |
专业分类
电工技术 | 675篇 |
综合类 | 481篇 |
化学工业 | 2597篇 |
金属工艺 | 557篇 |
机械仪表 | 594篇 |
建筑科学 | 756篇 |
矿业工程 | 154篇 |
能源动力 | 434篇 |
轻工业 | 1332篇 |
水利工程 | 215篇 |
石油天然气 | 266篇 |
武器工业 | 75篇 |
无线电 | 1904篇 |
一般工业技术 | 2072篇 |
冶金工业 | 1577篇 |
原子能技术 | 189篇 |
自动化技术 | 2083篇 |
出版年
2024年 | 65篇 |
2023年 | 226篇 |
2022年 | 453篇 |
2021年 | 668篇 |
2020年 | 477篇 |
2019年 | 412篇 |
2018年 | 476篇 |
2017年 | 460篇 |
2016年 | 473篇 |
2015年 | 510篇 |
2014年 | 673篇 |
2013年 | 856篇 |
2012年 | 888篇 |
2011年 | 1009篇 |
2010年 | 743篇 |
2009年 | 704篇 |
2008年 | 722篇 |
2007年 | 620篇 |
2006年 | 534篇 |
2005年 | 416篇 |
2004年 | 352篇 |
2003年 | 310篇 |
2002年 | 355篇 |
2001年 | 262篇 |
2000年 | 221篇 |
1999年 | 232篇 |
1998年 | 542篇 |
1997年 | 358篇 |
1996年 | 281篇 |
1995年 | 166篇 |
1994年 | 169篇 |
1993年 | 155篇 |
1992年 | 92篇 |
1991年 | 96篇 |
1990年 | 84篇 |
1989年 | 90篇 |
1988年 | 59篇 |
1987年 | 52篇 |
1986年 | 57篇 |
1985年 | 57篇 |
1984年 | 53篇 |
1983年 | 51篇 |
1982年 | 53篇 |
1981年 | 45篇 |
1980年 | 39篇 |
1979年 | 39篇 |
1978年 | 29篇 |
1977年 | 48篇 |
1976年 | 78篇 |
1975年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
141.
142.
异形螺母需要三副模具才能成形。其凸、凹模需要经过多次的加工,对设计和制造的要求较高。本文从制造的角度出发,论述了异形螺母模具的设计,方便了模具的加工,使模具的结构更趋合理。同时,着重讨论了模具关键件的结构设计与线切割加工。 相似文献
143.
利用原位自生法合成的纳米晶粒细化剂,成功的克服了颗粒团聚,有效的抑制了颗粒的沉降。本试验用其对ZL101合金的细化行为进行了研究。试验结果表明:加入量为0.2%(质量分数)时,纳米晶粒细化剂可有效地细化初晶α-Al,改善共晶硅的形貌及尺寸,细化后铸态α-Al枝晶尺寸由44μm减小至23μm;经T6处理的细化后试样其拉伸断口为韧窝断口,且韧窝明显多于未细化试样;加入细化剂后保温30min,与未细化合金相比,抗拉强度提高了28MPa,屈服强度提高了22MPa,延伸率增加了2.6%;同时细化后合金的阻尼性能较未细化合金有了大幅提高,0.5Hz时细化后室温阻尼性能Q-1=13×10-3,较之细化前Q-1提高了5×10-3。 相似文献
144.
Yi-feng HU Wen DENG WEN-bo HAO Li YUE Le HUANG Yu-yang HUANG Liang-yue XIONG 《中国有色金属学会会刊》2006,16(6):1259-1262
1Introduction NiTi alloys are the most successful shape memory alloys as a result of their combination of good functional properties and excellent mechanical strength[1,2].The thermal and mechanical shape memory behavior in these alloys is dependent upon … 相似文献
146.
147.
In quantum key distribution (QKD), the information theoretically secure authentication is necessary to guarantee the integrity and authenticity of the exchanged information over the classical channel. In order to reduce the key consumption, the authentication scheme with key recycling (KR), in which a secret but fixed hash function is used for multiple messages while each tag is encrypted with a one-time pad (OTP), is preferred in QKD. Based on the assumption that the OTP key is perfect, the security of the authentication scheme has be proved. However, the OTP key of authentication in a practical QKD system is not perfect. How the imperfect OTP affects the security of authentication scheme with KR is analyzed thoroughly in this paper. In a practical QKD, the information of the OTP key resulting from QKD is partially leaked to the adversary. Although the information leakage is usually so little to be neglected, it will lead to the increasing degraded security of the authentication scheme as the system runs continuously. Both our theoretical analysis and simulation results demonstrate that the security level of authentication scheme with KR, mainly indicated by its substitution probability, degrades exponentially in the number of rounds and gradually diminishes to zero. 相似文献
148.
行动导向教学法的应用改变了中职电子商务原有的教学思路和模式,电子商务教学的方法和手段得到了极大地丰富。通过自主学习学到的知识能够被学生更好的理解,独立实施而形成的技能能够被学生更好地掌握。行动导向法中常用的方法包括:项目教学法、角色扮演法、案例教学法、头脑风暴法等。教师在上课时应根据教学内容、实训实习条件、学生课堂氛围,针对性选取教学方法,达到加强教学效果的目的。 相似文献
149.
Aurélien Plyer Guy Le Besnerais Frédéric Champagnat 《Journal of Real-Time Image Processing》2016,11(4):713-730
This paper deals with dense optical flow estimation from the perspective of the trade-off between quality of the estimated flow and computational cost which is required by real-world applications. We propose a fast and robust local method, denoted by eFOLKI, and describe its implementation on GPU. It leads to very high performance even on large image formats such as 4 K (3,840 × 2,160) resolution. In order to assess the interest of eFOLKI, we first present a comparative study with currently available GPU codes, including local and global methods, on a large set of data with ground truth. eFOLKI appears significantly faster while providing quite accurate and highly robust estimated flows. We then show, on four real-time video processing applications based on optical flow, that eFOLKI reaches the requirements both in terms of estimated flows quality and of processing rate. 相似文献
150.
Despite the critical role that middleboxes play in introducing new network functionality, management and innovation of them are still severe challenges for network operators, since traditional middleboxes based on hardware lack service flexibility and scalability. Recently, though new networking technologies, such as network function virtualization (NFV) and software-defined networking (SDN), are considered as very promising drivers to design cost-efficient middlebox service architectures, how to guarantee transmission efficiency has drawn little attention under the condition of adding virtual service process for traffic. Therefore, we focus on the service deployment problem to reduce the transport delay in the network with a combination of NFV and SDN. First, a framework is designed for service placement decision, and an integer linear programming model is proposed to resolve the service placement and minimize the network transport delay. Then a heuristic solution is designed based on the improved quantum genetic algorithm. Experimental results show that our proposed method can calculate automatically the optimal placement schemes. Our scheme can achieve lower overall transport delay for a network compared with other schemes and reduce 30% of the average traffic transport delay compared with the random placement scheme. 相似文献