全文获取类型
收费全文 | 8185篇 |
免费 | 291篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 62篇 |
综合类 | 7篇 |
化学工业 | 1643篇 |
金属工艺 | 208篇 |
机械仪表 | 184篇 |
建筑科学 | 287篇 |
矿业工程 | 52篇 |
能源动力 | 133篇 |
轻工业 | 798篇 |
水利工程 | 130篇 |
石油天然气 | 232篇 |
无线电 | 507篇 |
一般工业技术 | 1416篇 |
冶金工业 | 1599篇 |
原子能技术 | 61篇 |
自动化技术 | 1171篇 |
出版年
2023年 | 52篇 |
2022年 | 82篇 |
2021年 | 150篇 |
2020年 | 119篇 |
2019年 | 100篇 |
2018年 | 204篇 |
2017年 | 204篇 |
2016年 | 252篇 |
2015年 | 189篇 |
2014年 | 214篇 |
2013年 | 582篇 |
2012年 | 450篇 |
2011年 | 481篇 |
2010年 | 351篇 |
2009年 | 298篇 |
2008年 | 379篇 |
2007年 | 288篇 |
2006年 | 264篇 |
2005年 | 203篇 |
2004年 | 168篇 |
2003年 | 160篇 |
2002年 | 148篇 |
2001年 | 110篇 |
2000年 | 119篇 |
1999年 | 114篇 |
1998年 | 521篇 |
1997年 | 313篇 |
1996年 | 194篇 |
1995年 | 111篇 |
1994年 | 112篇 |
1993年 | 125篇 |
1992年 | 47篇 |
1991年 | 72篇 |
1990年 | 48篇 |
1989年 | 61篇 |
1988年 | 57篇 |
1987年 | 49篇 |
1985年 | 58篇 |
1984年 | 60篇 |
1982年 | 47篇 |
1981年 | 60篇 |
1980年 | 53篇 |
1979年 | 51篇 |
1978年 | 64篇 |
1977年 | 83篇 |
1976年 | 75篇 |
1975年 | 62篇 |
1974年 | 54篇 |
1973年 | 49篇 |
1970年 | 37篇 |
排序方式: 共有8490条查询结果,搜索用时 15 毫秒
1.
Nitrous oxide (N2O) effects were evaluated, as a behavioural model of inert gas narcosis, in rats performing a vigilance task in which they were required to respond to a slight luminous increment of the house-light. A dose-related decrease of correct responses was produced by the tested range of concentrations of N2O (from 30 to 70% N2O), with a parallel increase of anticipatory responses up to 60% N2O and a dramatic increase of omissions at 70% N2O. The influence of preparatory period duration on hits delays suggested a 'conditional probability effect' conserved under N2O. Pretreatment of animals with flumazenil (a central benzodiazepine receptor antagonist) did not improve performance under 40% N2O. Naltrexone, an opiate receptor antagonist, however, increased the N2O-induced deficits. These results suggest that benzodiazepine receptors are not involved in N2O-induced impairments in this attentional task, but opiate mechanisms may be implicated. 相似文献
2.
F. J. Carrière H. Sekiguchi N. N. Surin V. A. Kotelnikov Ya. S. Vygodskii 《Polymer Bulletin》1995,35(4):441-448
Summary Polyimides (PI) having different molecular weights were prepared by condensation of oxydiphthalic anhydride with 9,9-bis-(4-aminophenyl)fluorene in nitrobenzene solution at 180°C. These polyimides carried two amino chain ends which allowed us to fix polycaprolactam chains (PA6) to obtain PA6-PI-PA6 type copolymers. The elemental analysis and infrared spectroscopic determination gave the proportion of PA6 (or PI) in the copolymers. The studies of thermal properties-DSC and TGA-allowed us to characterize the copolymers. 相似文献
3.
The article established the regularities of change of the physicomechanical characteristics and strength of glass textolites in single and repeated thermal loading. It shows that under multiple loading the intense loss of strength of the investigated materials is due to increased porosity on account of the large number of microcracks appearing in the structure. A correlation is obtained between the elastic and strength characteristics and porosity in dependence on the temperature of multiple heating which in the first approximation is described by a polynomial of second degree with respect to temperature, multiplied by the reciprocal of porosity.Translated from Problemy Prochnosti, No. 6, pp. 53–58, June, 1991. 相似文献
4.
Ér. V. Kal’yanov 《Technical Physics Letters》2007,33(6):451-453
A new simple model of a system with chaotic dynamics, based on the equations of bistable systems, is considered. The possibility of converting harmonic signals into chaotic oscillations, which represent intermittent irregular and switching quasi-regular motions, is demonstrated by numerical methods. The mechanism of chaotization is analyzed using the results of numerical calculations. 相似文献
5.
6.
7.
8.
9.
10.