全文获取类型
收费全文 | 2059篇 |
免费 | 34篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 10篇 |
综合类 | 9篇 |
化学工业 | 95篇 |
金属工艺 | 15篇 |
机械仪表 | 13篇 |
建筑科学 | 27篇 |
矿业工程 | 2篇 |
能源动力 | 14篇 |
轻工业 | 66篇 |
水利工程 | 7篇 |
石油天然气 | 13篇 |
武器工业 | 1篇 |
无线电 | 34篇 |
一般工业技术 | 70篇 |
冶金工业 | 1617篇 |
原子能技术 | 10篇 |
自动化技术 | 98篇 |
出版年
2023年 | 3篇 |
2022年 | 11篇 |
2021年 | 7篇 |
2020年 | 5篇 |
2019年 | 9篇 |
2018年 | 6篇 |
2017年 | 15篇 |
2016年 | 15篇 |
2015年 | 15篇 |
2014年 | 16篇 |
2013年 | 25篇 |
2012年 | 17篇 |
2011年 | 33篇 |
2010年 | 29篇 |
2009年 | 22篇 |
2008年 | 23篇 |
2007年 | 38篇 |
2006年 | 17篇 |
2005年 | 52篇 |
2004年 | 10篇 |
2003年 | 18篇 |
2002年 | 14篇 |
2001年 | 18篇 |
2000年 | 9篇 |
1999年 | 50篇 |
1998年 | 442篇 |
1997年 | 272篇 |
1996年 | 184篇 |
1995年 | 95篇 |
1994年 | 90篇 |
1993年 | 94篇 |
1992年 | 16篇 |
1991年 | 21篇 |
1990年 | 20篇 |
1989年 | 31篇 |
1988年 | 33篇 |
1987年 | 29篇 |
1986年 | 28篇 |
1985年 | 35篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 11篇 |
1981年 | 13篇 |
1980年 | 20篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 40篇 |
1976年 | 99篇 |
1975年 | 8篇 |
1974年 | 4篇 |
排序方式: 共有2101条查询结果,搜索用时 15 毫秒
991.
992.
993.
The effects of 3-acetylpyridine (3-AP) intoxication on the inferior olivary complex and cerebellar cortex of the rat were examined at both the light and electron microscopic level. Following intraperitoneal injection of 65 mg of 3-AP per kg body weight, the inferior olivary neurons were observed to undergo a rapid form of electron dense degeneration. A complete bilateral involvement of the nuclear complex was well advanced as early as 12 hours following injection. Marked astrocytic proliferation also occurred by 12 hours and appeared essential for neuronal fragmentation and disintegration. Microglial activity was prominent in the later stages, from 60 hours onwards, and participated in the phagocytic removal of degenerating neuronal fragments. By the end of the second week, all cytoplasmic and nuclear debri was removed. Concurrently, degenerative changes in the cerebellar cortex were evident from 12 hours onwards. All climbing fiber varicosities were observed to be degenerative as early as 24 hours following treatment. Electron microscopic observations revealed that these electron dense fragments were largely phagocytized and cleared by Bergmann glial cells around 7 days. The sensitivity of the olivocerebellar system to 3-AP thus provides a convenient and selective means of eliminating all of the inferior olivary neurons and their axons, the climbing fibers of the cerebellar cortex. In contrast to the more conventionally used electrolytic methods, 3-AP causes a complete bilateral ablation of all olivary neurons while avoiding the problems inherent to electrolytic procedures, such as incomplete destruction of the nucleus and involvement of fibers of passage. 相似文献
994.
A newly described partial trisomy of the short arm of chromosome number 7 is reported in a familial translocation between 7 and 22. The unbalanced translocation was found in one family member, the propositus, and the balanced form in 5 other members. The possibility of this translocation being a rare telomeric attachment previously undescribed in humans is discussed. Prominent clinical features include general mental and motor retardation, microbrachycephaly, and cardiac and oral abnormalities. 相似文献
995.
996.
997.
998.
Y Isaka DK Brees K Ikegaya Y Kaneda E Imai NA Noble WA Border 《Canadian Metallurgical Quarterly》1996,2(4):418-423
This experiment was an attempt to use the soybean residue derived from the production of "soy milk". The residue contains about 18% protein, 70% carbohydrates and 7.5% lipid as fish feed for rearing common carp, Cyprinus carpio. There were 4 types of diets: (1) soybean residue, (2) soybean residue digested with Papain, (3) soybean residue (64%) mixed with beef liver (34%) and (4) same mixture as (3) but digested with Papain. The results indicate that the percentage increase in weight and length of fish feeding with beef liver supplemented diets was higher than those feeding with soybean residue alone. This was possibly due to the fact that beef liver was able to supplement the nutrient deficiency in soybean. The two types of feeds (2 and 4) digested with Papain also yielded significantly better fish growth in terms of weight and length gains, than their counterparts without digestion. Furthermore, the water turbidity of the tanks added with digested feeds was significantly less, as Papain was able to hyrolyse the protein substrates suspended in the water, and thus lowered the turbidity. 相似文献
999.
Ling Cen Dymitr Ruta Leigh Powell Benjamin Hirsch Jason Ng 《International Journal of Computer-Supported Collaborative Learning》2016,11(2):187-225
The benefits of collaborative learning, although widely reported, lack the quantitative rigor and detailed insight into the dynamics of interactions within the group, while individual contributions and their impacts on group members and their collaborative work remain hidden behind joint group assessment. To bridge this gap we intend to address three important aspects of collaborative learning focused on quantitative evaluation and prediction of group performance. First, we use machine learning techniques to predict group performance based on the data of member interactions and thereby identify whether, and to what extent, the group’s performance is driven by specific patterns of learning and interaction. Specifically, we explore the application of Extreme Learning Machine and Classification and Regression Trees to assess the predictability of group academic performance from live interaction data. Second, we propose a comparative model to unscramble individual student performances within the group. These performances are then used further in a generative mixture model of group grading as an explicit combination of isolated individual student grade expectations and compared against the actual group performances to define what we coined as collaboration synergy - directly measuring the improvements of collaborative learning. Finally the impact of group composition of gender and skills on learning performance and collaboration synergy is evaluated. The analysis indicates a high level of predictability of group performance based solely on the style and mechanics of collaboration and quantitatively supports the claim that heterogeneous groups with the diversity of skills and genders benefit more from collaborative learning than homogeneous groups. 相似文献
1000.
Leigh W. Frohlich C.J. Hornik S. Purvis R.L. Roberts T.L. 《IEEE transactions on systems, man, and cybernetics. Part A, Systems and humans : a publication of the IEEE Systems, Man, and Cybernetics Society》2008,38(1):93-104
The efficient market hypothesis (EMH) is a cornerstone of financial economics. The EMH asserts that security prices fully reflect all available information and that the stock market prices securities at their fair values. Therefore, investors cannot consistently ldquobeat the marketrdquo because stocks reside in perpetual equilibrium, making research efforts futile. This flies in the face of the conventional nonacademic wisdom that astute analysts can beat the market using technical or fundamental stock analysis. The purpose of this research is to partially assess whether technical analysts, who predict future stock prices by analyzing past stock prices, can consistently achieve a trading return that outperforms the stock market average return. This is tested using knowlege engineering experimentation with one price history pattern - the ldquobull flag stock chartrdquo - which signals technical analysts of a future stock market price increase. A recognizer for the stock chart pattern is built using a template-matching technique from pattern recognition. The recognizer and associated trading rules are then tested by simulating trading on over 35 years of daily closing price data for the New York stock exchange composite index. The experiment is then replicated using the horizontal rotation or mirror image pattern of the ldquobull flagrdquo (or ldquobear flagrdquo stock chart) that signals a future stock market decrease. Results are systematic, statistically significant, and fail to confirm the null hypothesis based on a corollary to the EMH: that profit realized from trading determined by this heuristic method is no better than what would be realized from trading decisions based on random choice. 相似文献