全文获取类型
收费全文 | 4433篇 |
免费 | 127篇 |
国内免费 | 19篇 |
专业分类
电工技术 | 154篇 |
综合类 | 4篇 |
化学工业 | 611篇 |
金属工艺 | 123篇 |
机械仪表 | 77篇 |
建筑科学 | 205篇 |
矿业工程 | 22篇 |
能源动力 | 128篇 |
轻工业 | 346篇 |
水利工程 | 41篇 |
石油天然气 | 14篇 |
武器工业 | 1篇 |
无线电 | 449篇 |
一般工业技术 | 565篇 |
冶金工业 | 865篇 |
原子能技术 | 29篇 |
自动化技术 | 945篇 |
出版年
2022年 | 30篇 |
2021年 | 54篇 |
2020年 | 39篇 |
2019年 | 51篇 |
2018年 | 108篇 |
2017年 | 69篇 |
2016年 | 80篇 |
2015年 | 58篇 |
2014年 | 114篇 |
2013年 | 272篇 |
2012年 | 208篇 |
2011年 | 195篇 |
2010年 | 223篇 |
2009年 | 220篇 |
2008年 | 283篇 |
2007年 | 183篇 |
2006年 | 209篇 |
2005年 | 188篇 |
2004年 | 122篇 |
2003年 | 138篇 |
2002年 | 124篇 |
2001年 | 74篇 |
2000年 | 77篇 |
1999年 | 91篇 |
1998年 | 131篇 |
1997年 | 114篇 |
1996年 | 95篇 |
1995年 | 74篇 |
1994年 | 64篇 |
1993年 | 73篇 |
1992年 | 53篇 |
1991年 | 37篇 |
1990年 | 49篇 |
1989年 | 48篇 |
1988年 | 32篇 |
1987年 | 35篇 |
1986年 | 43篇 |
1985年 | 46篇 |
1984年 | 49篇 |
1983年 | 42篇 |
1982年 | 36篇 |
1981年 | 38篇 |
1980年 | 37篇 |
1979年 | 23篇 |
1978年 | 26篇 |
1977年 | 30篇 |
1976年 | 35篇 |
1975年 | 14篇 |
1974年 | 29篇 |
1972年 | 14篇 |
排序方式: 共有4579条查询结果,搜索用时 156 毫秒
1.
2.
3.
4.
Warren Webb 《电子设计技术》2006,13(11):58-60,62,65
随着嵌入设备渗透进社会,并承担起更加重要的角色,安全失效会带来潜在的灾难性的后果。嵌入设备以无人干预方式运行在很多领域的数千种关键任务或安全相关系统中,如制造、健康保健、运输、金融和军事等。虽然我们不假思索地依赖于这些嵌入系统,但任何一种嵌入系统都可能成为临时黑客、犯罪团伙、恐怖分子,甚至敌对政府分子的潜在目标。阻止这些攻击的重任就落在了系统设计者的肩上,他不仅要保证通过或保存在嵌入设备中的数据的安全,而且还要保护产品本身的知识产权。 相似文献
5.
Steve Woolgar 《电信纪事》2002,57(3-4):159-179
The importance of rigorous research into the actual impact of the new Information and Communication Technologies (icts) on society in general cannot be overemphasised. The answer to questions concerning the precise effect ofiCTs on interpersonal relations, communication, social inclusion and exclusion, trust and identity are now central to discussion in both commercial and business fora. This paper examines the concept of the “virtual society“ in the light of the findings of the ESRC (Economic and Social Research Council) Virtual Society? Programme (1997–2002). The paper describes the need to rethink the actual approaches used in researching this area of social science at the same time as performing the analyses themselves. The author also highlights the requirement for future research to examine actual on the ground experiences. How are new technologies actually used and by whom? In addition, the author utilises his overview of this large body of research to put forward a useful guide for predicting the use of ICTs in practice. These “5 rules of virtuality” serve as pointers to the experiences that may be encountered in the development and implementation of new technologies. 相似文献
6.
7.
Steve Brightman 《今日电子》2008,(12)
采用WiMedia UWB标准的越来越多
WiMedia通用无线电平台是实现传输速率高达480Mb/s(更高的传输速率正在开发中)无线个人局域网(WPAN)的基础。这个平台并不局限于某一类应用,而是允许同时存在不同的协议适配层,如图1所示。WiMedia规范既规定了一些如无线USB之间相互通信的应用,也规定其他不相互通信的接口同时存在的应用。 相似文献
8.
The short contact time dissolution of vitrinite and inertinite concentrates of an Australian bituminous coal was studied under isothermal conditions with tetralin as solvent. The reactivity of the two maceral types and the yields and nature of the products were determined for a range of reaction temperatures (400, 420 and 440 °C) and reaction times (2–20 min). The dissolution of vitrinite proceeded at a significantly greater rate than for inertinite and was associated with greater selectivity to soluble non-gaseous products. At very short reaction times (2 min), the vitrinite underwent solubilizing reactions to yield products of higher molecular weight and greater oxygen functionality than was the case for inertinite, for which changes in the chemical nature of the products were negligible over the range of conditions studied. At longer reaction times (5 min), the composition of the vitrinite-derived products was similar to that of the inertinite-derived products. 相似文献
9.
The draft Long-Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) contains Cryptosporidium log-inactivation CT tables (ozone-in-water concentration [residual], “C” times contact time, T). Depending on water temperature, Cryptosporidium CT values that are listed are 15 to 25 times greater than CT values for equivalent Giardia log-inactivation credit. The elevated operating dose required for Cryptosporidium log-inactivation credit has the potential to increase disinfection by-product (DBP) formation (e.g., bromate). Calculating CT value accurately will minimize ozone dose, which will decrease operating cost and lower DBP formation, and at the same time maintain disinfection protection through implementation of scientifically based safety factors. Various methods are available for calculating CT value. The method chosen depends largely on the available information concerning ozone residual characteristics and hydrodynamic features of the ozone contactor, plus local regulatory requirements. Four methods are discussed in this paper. Each method can be used to calculate Giardia, virus, and Cryptosporidium log-inactivation credit. 相似文献
10.