全文获取类型
收费全文 | 685篇 |
免费 | 9篇 |
专业分类
电工技术 | 25篇 |
综合类 | 1篇 |
化学工业 | 115篇 |
金属工艺 | 12篇 |
机械仪表 | 7篇 |
建筑科学 | 37篇 |
矿业工程 | 3篇 |
能源动力 | 53篇 |
轻工业 | 42篇 |
水利工程 | 4篇 |
石油天然气 | 2篇 |
无线电 | 41篇 |
一般工业技术 | 67篇 |
冶金工业 | 204篇 |
原子能技术 | 6篇 |
自动化技术 | 75篇 |
出版年
2022年 | 3篇 |
2021年 | 9篇 |
2019年 | 5篇 |
2018年 | 13篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 9篇 |
2014年 | 5篇 |
2013年 | 40篇 |
2012年 | 23篇 |
2011年 | 18篇 |
2010年 | 22篇 |
2009年 | 15篇 |
2008年 | 19篇 |
2007年 | 26篇 |
2006年 | 20篇 |
2005年 | 5篇 |
2004年 | 14篇 |
2003年 | 16篇 |
2002年 | 15篇 |
2001年 | 22篇 |
2000年 | 11篇 |
1999年 | 8篇 |
1998年 | 42篇 |
1997年 | 20篇 |
1996年 | 28篇 |
1995年 | 21篇 |
1994年 | 16篇 |
1993年 | 20篇 |
1992年 | 16篇 |
1991年 | 12篇 |
1990年 | 13篇 |
1989年 | 14篇 |
1988年 | 17篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 20篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1982年 | 13篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 10篇 |
1975年 | 3篇 |
1973年 | 10篇 |
1972年 | 3篇 |
1971年 | 4篇 |
排序方式: 共有694条查询结果,搜索用时 15 毫秒
11.
12.
13.
14.
Gel permeation chromatography (GPC) was used to investigate the course of the sodium hydroxide catalysed methylolation of phenol in dilute aqueous solution. At low concentrations, the initial rate of methylolation was directly proportional to the concentrations of sodium hydroxide and of formaldehyde. By computer integration of the rate equations for the methylolation of phenol, of 2-methylol phenol and of 4-methylol phenol, the experimental rate curves were simulated and optimal values for the rate constants of all the methylolation steps were obtained. 相似文献
15.
When bituminous coal is heated in an inert atmosphere (He) containing small amounts of oxygen at 393–455 °C, pyrite (FeS2) in coal is partially converted to magnetite (Fe304). The maximum amount of Fe304 formed during the time of heating corresponds to 5–20% of the total pyrite present, depending on the coal sample. The magnetite forms as an outer crust on the pyrite grains. The fact that the magnetic properties of the pyrite grains are substantially increased by the magnetite crust suggests that pyrite can be separated from coal by use of a low magnetic field. In a laboratory test, 75% removal is obtained by means of a 500 Oe magnet on three samples, and 60% on a fourth sample. 相似文献
16.
17.
A study of part‐time student experience of university courses delivered using a range of technologies found that information and communication technology enabled students to move between study and work experience to the benefit of their learning in both contexts. Technology‐based study activities enabled students to participate in learning both as a student and as a member of a practice or work context. Given the increasingly pressured lives of all students in higher education and their aspirations for employment after graduation, this suggests that we would benefit from taking their relationship to work and professional practice into account more directly, in deciding how to integrate technology into their study experience. Teacher conceptions of technology as a tool primarily for information delivery and discussion need to expand to recognize that it can be used to construct learning experiences situated in roles, skills and interactive environments that enhance students' ability to make transitions across the boundaries between contexts of study and work. 相似文献
18.
Vehicle Teleoperation Interfaces 总被引:1,自引:1,他引:0
Despite advances in autonomy, there will always be a need for human involvement in vehicle teleoperation. In particular, tasks such as exploration, reconnaissance and surveillance will continue to require human supervision, if not guidance and direct control. Thus, it is critical that the operator interface be as efficient and as capable as possible. In this paper, we provide an overview of vehicle teleoperation and present a summary of interfaces currently in use. 相似文献
19.
20.
Douglas A Stow Allen Hope David Verbyla Fred Huemmrich Charles Racine Kenneth Tape Kenji Yoshikawa Brian Noyle David Douglas Gensuo Jia Donald Walker Aaron Petersen Ranga Myneni 《Remote sensing of environment》2004,89(3):281-308
The objective of this paper is to review research conducted over the past decade on the application of multi-temporal remote sensing for monitoring changes of Arctic tundra lands. Emphasis is placed on results from the National Science Foundation Land-Air-Ice Interactions (LAII) program and on optical remote sensing techniques. Case studies demonstrate that ground-level sensors on stationary or moving track platforms and wide-swath imaging sensors on polar orbiting satellites are particularly useful for capturing optical remote sensing data at sufficient frequency to study tundra vegetation dynamics and changes for the cloud prone Arctic. Less frequent imaging with high spatial resolution instruments on aircraft and lower orbiting satellites enable more detailed analyses of land cover change and calibration/validation of coarser resolution observations.The strongest signals of ecosystem change detected thus far appear to correspond to expansion of tundra shrubs and changes in the amount and extent of thaw lakes and ponds. Changes in shrub cover and extent have been documented by modern repeat imaging that matches archived historical aerial photography. NOAA Advanced Very High Resolution Radiometer (AVHRR) time series provide a 20-year record for determining changes in greenness that relates to photosynthetic activity, net primary production, and growing season length. The strong contrast between land materials and surface waters enables changes in lake and pond extent to be readily measured and monitored. 相似文献