全文获取类型
收费全文 | 25074篇 |
免费 | 1045篇 |
国内免费 | 33篇 |
专业分类
电工技术 | 331篇 |
综合类 | 38篇 |
化学工业 | 5661篇 |
金属工艺 | 386篇 |
机械仪表 | 486篇 |
建筑科学 | 1321篇 |
矿业工程 | 100篇 |
能源动力 | 639篇 |
轻工业 | 1919篇 |
水利工程 | 252篇 |
石油天然气 | 72篇 |
无线电 | 1859篇 |
一般工业技术 | 4572篇 |
冶金工业 | 4734篇 |
原子能技术 | 199篇 |
自动化技术 | 3583篇 |
出版年
2023年 | 203篇 |
2022年 | 288篇 |
2021年 | 570篇 |
2020年 | 342篇 |
2019年 | 433篇 |
2018年 | 544篇 |
2017年 | 469篇 |
2016年 | 641篇 |
2015年 | 561篇 |
2014年 | 758篇 |
2013年 | 1469篇 |
2012年 | 1174篇 |
2011年 | 1533篇 |
2010年 | 1083篇 |
2009年 | 1025篇 |
2008年 | 1157篇 |
2007年 | 1112篇 |
2006年 | 956篇 |
2005年 | 764篇 |
2004年 | 754篇 |
2003年 | 671篇 |
2002年 | 571篇 |
2001年 | 433篇 |
2000年 | 371篇 |
1999年 | 411篇 |
1998年 | 800篇 |
1997年 | 583篇 |
1996年 | 466篇 |
1995年 | 420篇 |
1994年 | 393篇 |
1993年 | 380篇 |
1992年 | 275篇 |
1991年 | 199篇 |
1990年 | 270篇 |
1989年 | 266篇 |
1988年 | 221篇 |
1987年 | 229篇 |
1986年 | 235篇 |
1985年 | 275篇 |
1984年 | 231篇 |
1983年 | 239篇 |
1982年 | 213篇 |
1981年 | 208篇 |
1980年 | 175篇 |
1979年 | 197篇 |
1978年 | 167篇 |
1977年 | 188篇 |
1976年 | 240篇 |
1975年 | 162篇 |
1974年 | 126篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
141.
Adrian Thomas Christopher D. Gilson Tanveer Ahmed 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,64(1):73-79
Equipment was developed to measure the time for complete gelling of sodium alginate fibres in calcium chloride solution, taken as the time to achieve maximum tensile strength. The effects of fibre diameter, alginate concentration, alginate composition and calcium chloride concentration on gelling time were investigated. A diffusional model, developed to predict the gelling time, agreed with experimental results except for the effect of calcium ion concentration which was modelled empirically. 相似文献
142.
143.
Erythrocyte ghosts were exposed to various levels of oxyradical shock in order to identify the extent of accumulation of peroxidative intermediates. Malondialdehyde reacting end products were the same in all different models. But, the accumulation of dienyl radical species increased with higher intensity of oxyradical shock. These dienyl radicals may rearrange to create a homogeneous smectic multilamellar microenvironment which may be more fluid in terms of the molecular dynamics. 相似文献
144.
Maxwell G.D. Kashyap R. Sherlock G. Collins J.V. Ainslie B.J. 《Electronics letters》1994,30(18):1486-1487
The authors report the first demonstration of a semiconductor external cavity waveguide laser, modulated at 2.5 Gbit/s over 100 km of standard optical fibre using a UV written grating in a planar silica waveguide as the feedback element 相似文献
145.
Analyzes the literature on 3 aspects of attachment—neurobiological influences, interpersonal and intrapersonal factors, and societal factors—in the psychological development of chronically disabled children. Evidence suggests that neurochemical substances such as cortisol and brain biogenic amine systems reciprocally interact with psychological and psychosocial factors to influence attachment. Interpersonal and intrapersonal factors such as temperamental characteristics of children, severity and type of disability, and family influences interact in the process of attachment. Social perceptions and prejudices about the disabled individual increase parental stress, and diminish parental involvement and resources, which are necessary for attachment. These 3 processes are powerful and interrelated forces in child development, with potential to modify social competence, neurological development, and psychosocial adjustment. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
146.
147.
Thompson Robert J.; Gil Karen M.; Burbach Daniel J.; Keith Barbara R.; Kinney Thomas R. 《Canadian Metallurgical Quarterly》1993,61(3):468
In this study, 64% of children aged 7–12 yrs with sickle cell disease were found to have a parent-reported behavior problem, and 50% met the criteria for a Diagnostic and Statistical Manual of Mental Disorders-III-Revised (DSM-III-R) diagnosis based on a structured clinical interview of the child. Internalizing types of behavior problems and diagnoses were the most frequent. Support was provided for a transactional stress and coping model in delineating the processes associated with child adjustment. In particular, maternal anxiety accounted for 16–33% of the variance in mother-reported internalizing and externalizing behavior problems, respectively, and child pain-coping strategies accounted for 21% of the variance in child-reported adjustment problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
148.
149.
150.