全文获取类型
收费全文 | 570920篇 |
免费 | 4159篇 |
国内免费 | 928篇 |
专业分类
电工技术 | 10591篇 |
综合类 | 509篇 |
化学工业 | 90460篇 |
金属工艺 | 23338篇 |
机械仪表 | 18511篇 |
建筑科学 | 12604篇 |
矿业工程 | 4314篇 |
能源动力 | 14571篇 |
轻工业 | 46012篇 |
水利工程 | 7048篇 |
石油天然气 | 15012篇 |
武器工业 | 39篇 |
无线电 | 60581篇 |
一般工业技术 | 116587篇 |
冶金工业 | 95565篇 |
原子能技术 | 14704篇 |
自动化技术 | 45561篇 |
出版年
2021年 | 5684篇 |
2020年 | 4443篇 |
2019年 | 5772篇 |
2018年 | 9213篇 |
2017年 | 9429篇 |
2016年 | 9952篇 |
2015年 | 6039篇 |
2014年 | 10246篇 |
2013年 | 26103篇 |
2012年 | 15778篇 |
2011年 | 21090篇 |
2010年 | 16974篇 |
2009年 | 18820篇 |
2008年 | 19074篇 |
2007年 | 18771篇 |
2006年 | 16289篇 |
2005年 | 14743篇 |
2004年 | 14012篇 |
2003年 | 13697篇 |
2002年 | 13248篇 |
2001年 | 12852篇 |
2000年 | 12332篇 |
1999年 | 12011篇 |
1998年 | 27652篇 |
1997年 | 20040篇 |
1996年 | 15629篇 |
1995年 | 12006篇 |
1994年 | 10861篇 |
1993年 | 10612篇 |
1992年 | 8333篇 |
1991年 | 8102篇 |
1990年 | 7989篇 |
1989年 | 7763篇 |
1988年 | 7477篇 |
1987年 | 6747篇 |
1986年 | 6533篇 |
1985年 | 7390篇 |
1984年 | 6701篇 |
1983年 | 6440篇 |
1982年 | 5778篇 |
1981年 | 5896篇 |
1980年 | 5633篇 |
1979年 | 5734篇 |
1978年 | 5663篇 |
1977年 | 6179篇 |
1976年 | 7685篇 |
1975年 | 5108篇 |
1974年 | 4904篇 |
1973年 | 4980篇 |
1972年 | 4279篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
221.
222.
In this paper we design an experiment which can be depicted as a simple scenario, a very limited 'world'. In this world, there are an actor that can pursue a project and an observer that is keeping its eyes on the actor. We try to show in the experiment that the observer can to some degree understand the actor based on its knowledge and some metaphors, i.e. understand what the actor is doing and why. As the conclusion of this experiment, we try to show some features of 'understanding'. These are (1) that 'understanding' has to be based on some preliminary knowledge; (2) that 'understanding' is a process of incremental learning; (3) that, as for symbolic systems, some metaphors are necessary for mapping real entities into concepts in mind. 相似文献
223.
224.
Sure System 2000, a fault-tolerant computer that couples multiprocessors to offer low-priced, high-performance systems that deal effectively with faults and failures, is presented. The architecture is based on the local redundancy technique, ensuring that no hardware or software fault can cause a system crash. Software errors can be fixed, and hardware can be replaced, upgraded, or added dynamically. Existing fault-tolerant computers are briefly reviewed, and the logic hardware system configuration of the Sure System 2000 is described. The multiprocessor and I/O architecture are examined. The SXO Sure System 2000 expandable operating system is described 相似文献
225.
226.
Y. Rey-Tauriac J. Badoc B. Reynard R.A. Bianchi D. Lachenal A. Bravaix 《Microelectronics Reliability》2005,45(9-11):1349
This paper presents results of reliability investigation of 20 V N-Drift MOS transistor in 0.13 μm CMOS technology. Due to high performances required for CMOS applications, adding high voltage devices becomes a big challenge to guarantee the reliability criteria. In this context, new reliability approaches are needed. Safe Operating Area are defined for switch, Vds limited and Vgs limited applications in order to improve circuit designs. For Vds limited applications, deep doping dose effects in drift area are investigated in correlation to lifetime evaluations based on device parameter shifts under hot carrier stressing. To further determine the amount and locations of hot carriers injections, accurate 2D technological and electrical simulations are performed and permit to select the best compromise between performance and reliability for N-Drift MOS transistor. 相似文献
227.
228.
A. Alt Dr.‐Ing. H. Mertens U. Arz L. Blessing C. Berger 《Materialwissenschaft und Werkstofftechnik》2007,38(5):402-409
High cycle fatigue of bolted connections Extensive tests regarding the influences on the fatigue of bolt‐nut‐connections of preloading with torsion, of preloading with yielding, of loading with superimposed bending and of the tested lot are processed. These influences are not yet known according to VDI 2230. New testing devices were designed for these tests, which allow a far less expensive operation and may easily be used for bolts of diameters up to M100 and testing frequencies up to 1000 Hz. The validity of fatigue resistance according to VDI 2230 is specified with respect to the test results. The determined influence of the tested lots is unexpectedly high. The manufacturing process of bolts should be improved to minimize this influence. 相似文献
229.
230.