全文获取类型
收费全文 | 433936篇 |
免费 | 28618篇 |
国内免费 | 16041篇 |
专业分类
电工技术 | 21607篇 |
技术理论 | 45篇 |
综合类 | 27110篇 |
化学工业 | 70015篇 |
金属工艺 | 25073篇 |
机械仪表 | 25181篇 |
建筑科学 | 29664篇 |
矿业工程 | 12151篇 |
能源动力 | 10699篇 |
轻工业 | 27292篇 |
水利工程 | 7940篇 |
石油天然气 | 23689篇 |
武器工业 | 2795篇 |
无线电 | 47280篇 |
一般工业技术 | 54190篇 |
冶金工业 | 20942篇 |
原子能技术 | 3848篇 |
自动化技术 | 69074篇 |
出版年
2024年 | 1456篇 |
2023年 | 5560篇 |
2022年 | 9856篇 |
2021年 | 13861篇 |
2020年 | 10432篇 |
2019年 | 8550篇 |
2018年 | 22760篇 |
2017年 | 23091篇 |
2016年 | 19154篇 |
2015年 | 14390篇 |
2014年 | 17662篇 |
2013年 | 21069篇 |
2012年 | 25581篇 |
2011年 | 33880篇 |
2010年 | 29855篇 |
2009年 | 26113篇 |
2008年 | 26930篇 |
2007年 | 27046篇 |
2006年 | 20158篇 |
2005年 | 18764篇 |
2004年 | 13012篇 |
2003年 | 11793篇 |
2002年 | 10410篇 |
2001年 | 8901篇 |
2000年 | 8919篇 |
1999年 | 9440篇 |
1998年 | 7225篇 |
1997年 | 6160篇 |
1996年 | 5857篇 |
1995年 | 4795篇 |
1994年 | 3897篇 |
1993年 | 2632篇 |
1992年 | 2083篇 |
1991年 | 1591篇 |
1990年 | 1234篇 |
1989年 | 995篇 |
1988年 | 839篇 |
1987年 | 524篇 |
1986年 | 410篇 |
1985年 | 258篇 |
1984年 | 206篇 |
1983年 | 164篇 |
1982年 | 128篇 |
1981年 | 76篇 |
1980年 | 96篇 |
1968年 | 46篇 |
1966年 | 45篇 |
1965年 | 45篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
一种具有带孔补偿过滤器的γ剂量计的能响补偿计算 总被引:1,自引:0,他引:1
对在低能区有过高响应的γ辐射剂量计可采用带孔补偿过滤器进行能响补偿。本文介绍了对这类补偿过滤器选择最佳补偿参数(材料厚度和孔隙率)的近似求解方法;并对 CaSO:Tm 热释光剂量计用此方法作了实例计算。文中还计算了自制带有鼠笼结构的这类补偿过滤器的 CaSO:,Tm热释光剂量计对照射量的能量响应,与实测结果比较,各能量点响应的最大相差为10%。 相似文献
12.
Introduction
Owing to long-time running, more facilities including stations, pipelines, vessels have become corrosive and aged ,some process has grown old, it has exert more burden for the maintenance and repair.Simultaneously, the fluid production rate, oil production rate and water injection rate has changed greatly so that the inflicts and problems from the established surface systems will become more obvious. Energy cost of production and running has increasing continuously. Capacity has been unbalance in systems and areas.
…… 相似文献
13.
关于粒子加速器人身辐射安全联锁系统设计原则的建议 总被引:2,自引:2,他引:0
本文讨论了在粒子加速器上的联锁系统设计中应遵循的一些原则,其中建立隔离区、“失效导致安全(Fail-safe)”,使用“硬件”、“多重联锁”、设置急停开关等是最重要的。 相似文献
14.
15.
16.
J-M Choe 《欧洲信息系统杂志》2002,11(2):142-158
This study empirically examined the organisational learning effects of the nonfinancial performance information provided by management accounting information systems (MAISs) under advanced manufacturing technology (AMT). In this study, a target costing system and the frequent and quick reporting of information were considered the facilitators of learning. First, we examined the relationships between AMT level and the amount of nonfinancial performance information produced by MAISs. The empirical results showed that there are significant positive relationships between the level of AMT and nonfinancial performance information. With a systems approach, we also proved the impact of the relationships among AMT levels, nonfinancial performance information and learning facilitators on the organisational performance of a firm. The results of our research suggest that under a high level of AMT, for the provision of information to result in an increase of performance through organisational learning, a target costing system must be introduced and a large amount of information should be provided frequently and quickly. The results of this study also showed that although AMT level may be low, fairly well-arranged facilitators and a moderately large amount of information may be necessary for the improvement of performance. In conclusion, effective organisational learning depends on the provision of relevant information as well as efficient learning support mechanisms. 相似文献
17.
18.
Medard M. Lumetta S. Liuyang Li 《Selected Areas in Communications, IEEE Journal on》2002,20(4):822-833
We describe an architecture for an optical local area network (LAN) or metropolitan area network (MAN) access. The architecture allows for bandwidth sharing within a wavelength and is robust to both link and node failures. The architecture can be utilized with an arbitrary, link-redundant mesh network (node-redundancy is necessary only to handle all node failures), and assumes neither the use of a star topology nor the ability to embed such a topology within the physical mesh. Reservation of, bandwidth is performed in a centralized fashion at a (replicated) head end node, simplifying the implementation of complex sharing policies relative to implementation on a distributed set of routers. Unlike a router, however, the head end does not take any action on individual packets and, in particular, does not buffer packets. The architecture thus avoids the difficulties of processing packets in the optical domain while allowing for packetized shared access of wavelengths. We describe the route construction scheme and prove its ability to recover from single link and single node failures, outline a flexible medium access protocol and discuss the implications for implementing specific policies, and propose a simple implementation of the recovery protocol in terms of state machines for per-link devices 相似文献
19.
20.