全文获取类型
收费全文 | 2889篇 |
免费 | 45篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 37篇 |
综合类 | 2篇 |
化学工业 | 360篇 |
金属工艺 | 37篇 |
机械仪表 | 68篇 |
建筑科学 | 147篇 |
矿业工程 | 75篇 |
能源动力 | 68篇 |
轻工业 | 217篇 |
水利工程 | 11篇 |
石油天然气 | 9篇 |
武器工业 | 1篇 |
无线电 | 341篇 |
一般工业技术 | 442篇 |
冶金工业 | 680篇 |
原子能技术 | 20篇 |
自动化技术 | 424篇 |
出版年
2022年 | 23篇 |
2021年 | 23篇 |
2020年 | 30篇 |
2019年 | 22篇 |
2018年 | 29篇 |
2017年 | 24篇 |
2016年 | 30篇 |
2015年 | 36篇 |
2014年 | 43篇 |
2013年 | 154篇 |
2012年 | 90篇 |
2011年 | 90篇 |
2010年 | 102篇 |
2009年 | 89篇 |
2008年 | 109篇 |
2007年 | 97篇 |
2006年 | 106篇 |
2005年 | 100篇 |
2004年 | 66篇 |
2003年 | 77篇 |
2002年 | 70篇 |
2001年 | 63篇 |
2000年 | 65篇 |
1999年 | 68篇 |
1998年 | 206篇 |
1997年 | 123篇 |
1996年 | 95篇 |
1995年 | 65篇 |
1994年 | 58篇 |
1993年 | 54篇 |
1992年 | 24篇 |
1991年 | 36篇 |
1990年 | 28篇 |
1989年 | 30篇 |
1988年 | 49篇 |
1987年 | 28篇 |
1986年 | 29篇 |
1985年 | 39篇 |
1984年 | 32篇 |
1983年 | 35篇 |
1982年 | 28篇 |
1981年 | 45篇 |
1980年 | 22篇 |
1979年 | 23篇 |
1978年 | 16篇 |
1977年 | 37篇 |
1976年 | 51篇 |
1973年 | 22篇 |
1972年 | 14篇 |
1966年 | 13篇 |
排序方式: 共有2939条查询结果,搜索用时 156 毫秒
1.
2.
3.
4.
K Giesen T Hummel A Stollewerk S Harrison A Travers C Kl?mbt 《Canadian Metallurgical Quarterly》1997,124(12):2307-2316
Two classes of glial cells are found in the embryonic Drosophila CNS, midline glial cells and lateral glial cells. Midline glial development is triggered by EGF-receptor signalling, whereas lateral glial development is controlled by the gcm gene. Subsequent glial cell differentiation depends partly on the pointed gene. Here we describe a novel component required for all CNS glia development. The tramtrack gene encodes two zinc-finger proteins, one of which, ttkp69, is expressed in all non-neuronal CNS cells. We show that ttkp69 is downstream of gcm and can repress neuronal differentiation. Double mutant analysis and coexpression experiments indicate that glial cell differentiation may depend on a dual process, requiring the activation of glial differentiation by pointed and the concomitant repression of neuronal development by tramtrack. 相似文献
5.
6.
Steroidal glycoalkaloids, found in species of the Solanaceae, elicit bursting activity in galeal and tarsal chemosensilla of adult Colorado potato beetles. The effect has an average latency of 6–12 sec, depending on the sensillum/alkaloid combination. A 20-sec alkaloid treatment is often suffficient to render galeal sensilla unresponsive to gamma-aminobutyric acid, normally an effective stimulant. The alkaloids have similar effects on galeal sensilla of larval Colorado potato beetles and on labellar chemosensilla of the blowfly. It is concluded that these compounds act independently of any specialized chemoreceptor in the Colorado potato beetle, and that association of the Colorado potato beetle with solanaceous plants has not led to evolution of a specific receptor forSolanum glycoalkaloids. 相似文献
7.
Less may not be more,but it still counts: The state of social capital in Yeoville,Johannesburg 总被引:2,自引:2,他引:0
Kirsten Harrison 《Urban Forum》2002,13(1):67-84
8.
Central to all parallel architectures is a switching network which facilitates the communication between a machine's components necessary to support their cooperation. Multistage interconnection networks (MINs) are classified and analytic models are described for both packet-switched and circuit-switched MINs with asynchronous transmission mode. Under strong enough assumptions, packet switching can be modeled by standard queuing methods, hence providing a standard against which to assess approximate models. We describe one such approximate model with much weaker assumptions which is more widely applicable and can be implemented more efficiently. To model circuit switching requires a different approach because of the presence of passive resources, namely multiple links through the MIN which must be held before a message can be transmitted and throughout its transmission. An approximate analysis based upon the recursive structure of a particular MIN topology which yields accurate predictions when compared with simulation is described. 相似文献
9.
A physically based hysteresis theory incorporating a domain size that depends on the Weiss effective field explains the observed ranges of reversible and irreversible magnetization in the initial-magnetization curve and exterior loop of ferromagnetic materials. The theory applies to materials exhibiting both normal and wasp-waisted exterior loops and agrees well with measured data. It also provides close linkages between magnetization at the quantum scale, domain properties at the mesoscopic scale, and measurements at the macroscopic scale. 相似文献