全文获取类型
收费全文 | 216514篇 |
免费 | 3535篇 |
国内免费 | 736篇 |
专业分类
电工技术 | 3767篇 |
综合类 | 177篇 |
化学工业 | 32652篇 |
金属工艺 | 8574篇 |
机械仪表 | 6651篇 |
建筑科学 | 5160篇 |
矿业工程 | 1347篇 |
能源动力 | 6396篇 |
轻工业 | 18196篇 |
水利工程 | 2432篇 |
石油天然气 | 4121篇 |
武器工业 | 9篇 |
无线电 | 25232篇 |
一般工业技术 | 43880篇 |
冶金工业 | 38524篇 |
原子能技术 | 5240篇 |
自动化技术 | 18427篇 |
出版年
2022年 | 1717篇 |
2021年 | 2695篇 |
2020年 | 2038篇 |
2019年 | 2470篇 |
2018年 | 3727篇 |
2017年 | 3547篇 |
2016年 | 3637篇 |
2015年 | 2369篇 |
2014年 | 3859篇 |
2013年 | 10328篇 |
2012年 | 5863篇 |
2011年 | 8000篇 |
2010年 | 6360篇 |
2009年 | 7089篇 |
2008年 | 7078篇 |
2007年 | 7028篇 |
2006年 | 5994篇 |
2005年 | 5544篇 |
2004年 | 5241篇 |
2003年 | 5091篇 |
2002年 | 4689篇 |
2001年 | 4810篇 |
2000年 | 4732篇 |
1999年 | 4871篇 |
1998年 | 11631篇 |
1997年 | 8333篇 |
1996年 | 6604篇 |
1995年 | 4821篇 |
1994年 | 4407篇 |
1993年 | 4209篇 |
1992年 | 3306篇 |
1991年 | 3195篇 |
1990年 | 2955篇 |
1989年 | 3030篇 |
1988年 | 2893篇 |
1987年 | 2481篇 |
1986年 | 2374篇 |
1985年 | 2791篇 |
1984年 | 2567篇 |
1983年 | 2407篇 |
1982年 | 2143篇 |
1981年 | 2263篇 |
1980年 | 2073篇 |
1979年 | 2154篇 |
1978年 | 2142篇 |
1977年 | 2391篇 |
1976年 | 3217篇 |
1975年 | 1843篇 |
1974年 | 1768篇 |
1973年 | 1781篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
72.
73.
74.
Potential mGAT4 inhibitors derived from the lead substance (S)-SNAP-5114 have been synthesized and characterized for their inhibitory potency. Variations from the parent compound included the substitution of one of its aromatic 4-methoxy and 4-methoxyphenyl groups, respectively, with a more polar moiety, including a carboxylic acid, alcohol, nitrile, carboxamide, sulfonamide, aldehyde or ketone function, or amino acid partial structures. Furthermore, it was investigated how the substitution of more than one of the aromatic 4-methoxy groups affects the potency and selectivity of the resulting compounds. Among the synthesized test substances (S)-1-{2-[(4-formylphenyl)bis(4-methoxyphenyl)-methoxy]ethyl}piperidine-3-carboxylic acid, that features a carbaldehyde function in place of one of the aromatic 4-methoxy moieties of (S)-SNAP-5114, was found to have a pIC50 value of 5.89±0.07, hence constituting a slightly more potent mGAT4 inhibitor than the parent substance while showing comparable subtype selectivity. 相似文献
75.
76.
77.
Kalai Selvan Ramalingam Karmegam Karuppiah Shiamala Devi Ramaiya Vivien How Enoch Kumar Perimal Hassan Sadeghi Naeini Sivasankar Sambasivam Kulanthayan KC Mani 《人机工程学与制造业中的人性因素》2019,29(5):426-434
Many occupations require workers to stand for long periods of time without proper interventions, which causes discomfort in the back and lower limbs. Therefore, this study aims to assess the effectiveness in alleviating body muscle discomfort during prolonged standing through the use of a calf massager. This study was conducted among male workers at a manufacturer with production line workers and the list was obtained from the HR Department and simple random sampling was done by number categorization. A total of 100 respondents (50 respondents for both the control and the experimental groups) participated in this study. The experiment took place in a room with a similar setup for the production line. Each respondent was requested to perform the simulated task for 2 hr. For the experimental group, the calf massager was turned on every 15 min. At every 15‐min interval after turning on the calf massager, respondents from both groups were required to evaluate their discomfort level on a Borg's scale CR‐10 questionnaire. The results showed that the level of body discomfort among respondents in the experimental group reduced (20–30%) compared with that of the control group. Multivariate analysis results revealed that the discomfort rating for the lower back, knees, thighs, calves, and feet was significantly lower (p < .05) among the experimental group compared with the control group. For lower body parts, the lower back region was statistically significant (p < .05) at the 90th, 105th, and 120th min; the thigh region was statistically significant (p < .05) at the 120th min; the knee region was statistically significant (p < .05) at the 105th and 120th min; the calf region was statistically significant (p < .05) at all minute intervals except the 15th and 45th min, while the feet region, was statistically significant at the 105th and 120th min. Therefore, this study indicates that calf massage treatment is capable of reducing body muscle discomfort during prolonged standing and highlights the significance of calf massage. 相似文献
78.
79.
A conceptualization of intended learning outcomes supporting self‐regulated learners in indicating learning paths
下载免费PDF全文
![点击此处可从《Journal of Computer Assisted Learning》网站下载免费的PDF全文](/ch/ext_images/free.gif)
P. Tangworakitthaworn L. Gilbert G.B. Wills 《Journal of Computer Assisted Learning》2015,31(5):393-404
Intended learning outcomes (ILOs) indicate what learners will be able to achieve after they are taught. Traditionally, ILOs are expressed as plain text or unstructured documents. What if all ILOs of a specific course of study can be conceptualized through a structured diagrammatic technique? It was hypothesized that learners can benefit from this conceptualization in learning, especially in self‐regulated learning. The aim of this study was to investigate whether the ILOs represented in unstructured or structured formats can facilitate learners to identify learning paths. The results revealed that the mean ratings of all learning paths were statistically significantly higher with structured ILOs. 相似文献
80.