全文获取类型
收费全文 | 197544篇 |
免费 | 15246篇 |
国内免费 | 8132篇 |
专业分类
电工技术 | 11355篇 |
技术理论 | 13篇 |
综合类 | 12218篇 |
化学工业 | 31939篇 |
金属工艺 | 10466篇 |
机械仪表 | 11681篇 |
建筑科学 | 15123篇 |
矿业工程 | 4875篇 |
能源动力 | 5564篇 |
轻工业 | 13336篇 |
水利工程 | 3477篇 |
石油天然气 | 9873篇 |
武器工业 | 1353篇 |
无线电 | 25210篇 |
一般工业技术 | 24901篇 |
冶金工业 | 10310篇 |
原子能技术 | 2209篇 |
自动化技术 | 27019篇 |
出版年
2024年 | 776篇 |
2023年 | 2991篇 |
2022年 | 5236篇 |
2021年 | 7321篇 |
2020年 | 5383篇 |
2019年 | 4506篇 |
2018年 | 5151篇 |
2017年 | 5959篇 |
2016年 | 5221篇 |
2015年 | 7056篇 |
2014年 | 9079篇 |
2013年 | 11621篇 |
2012年 | 12268篇 |
2011年 | 13578篇 |
2010年 | 11824篇 |
2009年 | 11546篇 |
2008年 | 11481篇 |
2007年 | 10855篇 |
2006年 | 10931篇 |
2005年 | 9387篇 |
2004年 | 6413篇 |
2003年 | 5439篇 |
2002年 | 5141篇 |
2001年 | 4703篇 |
2000年 | 4700篇 |
1999年 | 5221篇 |
1998年 | 4640篇 |
1997年 | 4040篇 |
1996年 | 3630篇 |
1995年 | 3052篇 |
1994年 | 2426篇 |
1993年 | 1921篇 |
1992年 | 1543篇 |
1991年 | 1174篇 |
1990年 | 967篇 |
1989年 | 783篇 |
1988年 | 635篇 |
1987年 | 472篇 |
1986年 | 354篇 |
1985年 | 307篇 |
1984年 | 202篇 |
1983年 | 156篇 |
1982年 | 151篇 |
1981年 | 113篇 |
1980年 | 96篇 |
1979年 | 67篇 |
1978年 | 57篇 |
1977年 | 56篇 |
1976年 | 94篇 |
1973年 | 32篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Computer-aided software engineering (CASE) tools are currently being used by IS professionals rather than by users. No matter how effective these tools may be, however, they will not be able to assist in the reduction of application backlogs without supporting user-driven applications. This article examines characteristics of a CASE environment from the various perspectives of decision support, identifies the advantages and limitations of end-user computing in this environment, and suggests how IS managers can realize the potentials of CASE for user applications. 相似文献
62.
In this work, a quantitative analysis is applied to resolve the newly reported polarity-dependent charge-to-breakdown (Q/sub BD/) data from thick oxides of 6.8 nm down to ultrathin oxides of 1.9 nm. Three independent sets of Q/sub BD/ data, i.e., n/sup +/poly/NFET stressed under inversion and accumulation, and p/sup +/ poly/PFET under accumulation are carefully investigated. The Q/sub BD/ degradation observed for p-type anodes, either poly-Si or Si-substrate, can be nicely understood with the framework of maximum energy released by injected electrons. Thus, this work provides a universal and quantitative account for a variety of experimental observations in the time-to-breakdown (T/sub BD/) and Q/sub BD/ polarity-dependence of oxide breakdown. 相似文献
63.
Chih-Wea Wang Chi-Feng Wu Jin-Fu Li Cheng-Wen Wu Tony Teng Kevin Chiu Hsiao-Ping Lin 《Journal of Electronic Testing》2002,18(6):637-647
In this paper we propose a novel built-in self-test (BIST) design for embedded SRAM cores. Our contribution includes a compact and efficient BIST circuit with diagnosis support and an automatic diagnostic system. The diagnosis module of our BIST circuit can capture the error syndromes as well as fault locations for the purposes of repair and fault/failure analysis. In addition, our design provides programmability for custom March algorithms with lower hardware cost. The combination of the on-line programming mode and diagnostic system dramatically reduces the effort in design debugging and yield enhancement. We have designed and implemented test chips with our BIST design. Experimental results show that the area overhead of the proposed BIST design is only 2.4% for a 128 KB SRAM, and 0.65% for a 2 MB one. 相似文献
64.
65.
66.
67.
Interfacial segregation of Ti in the brazing of diamond grits onto a steel substrate using a Cu-Sn-Ti brazing alloy 总被引:1,自引:0,他引:1
Wen-Chung Li Shun-Tian Lin Cheng Liang 《Metallurgical and Materials Transactions A》2002,33(7):2163-2172
Diamond grits were brazed onto a steel substrate using a prealloyed Cu-10Sn-15Ti (wt pct) brazing alloy at 925 °C and 1050
°C. Due to the relatively high concentration of Ti in the brazing alloy, the braze matrix exhibited a composite structure,
composed of β-(Cu,Sn), a Cu-based solid solution, and various intermetallic compounds with different morphologies. The reaction of Ti with
diamond yielded a continuous TiC layer on the surfaces of the diamond grits. On top of the TiC growth front, an intermetallic
compound, composed of Sn and Ti, nucleated and grew into a randomly interwoven fine lacey structure. An interfacial structure
developed as the interwoven fine lacey phase was semicoherently bonded to the TiC layer, with the Cu-based braze matrix filling
its interstices. The thickness of such a composite layer was increased linearly with the square root of isothermal holding
time at 925 °C, complying with the law of a diffusion-controlled process. However, at 1050 °C, the segregation behavior of
Ti and Sn to the interfaces between the TiC layer and the braze matrix diminished, due to the increased solubility of Ti in
the Cu-based liquid phase. The enhanced dissolution of Ti in the Cu-based liquid phase at 1050 °C also caused the precipitation
of rod-like CuTi with an average diameter of about 0.2 μm during cooling. SnTi3 was the predominant intermetallic compound and existed in three different forms in the braze matrix. It existed as interconnected
grains of large size which either floated to the surface of the braze matrix or grew into faceted grains. It also exhibited
a nail-like structure with a mean diameter of about 1 μm for the rod section and a lamellar structure arising from a eutectic reaction during cooling. 相似文献
68.
林苗 《电气电子教学学报》2002,24(1):43-45
阐述了我校使用“面向21世纪”电工学课程系列教材的实践与探索过程,以及对我校电工学教学所产生的转折性影响和积极的导向作用,最后对教材提出了几点建议。 相似文献
69.
70.
本文是对市场上几款高级便携式打印机主要性能特点的比较考察报告,包括:佳能生产的CanonBJC-70型便携式彩色喷墨打印机,惠普生产的HPDeskJet340型便携式彩色喷墨打印机和Pentax生产的Pentax PocketJet便携式打印机,后者必须使用热敏纸。 相似文献