全文获取类型
收费全文 | 6715篇 |
免费 | 669篇 |
国内免费 | 406篇 |
专业分类
电工技术 | 530篇 |
综合类 | 353篇 |
化学工业 | 1555篇 |
金属工艺 | 1404篇 |
机械仪表 | 175篇 |
建筑科学 | 336篇 |
矿业工程 | 79篇 |
能源动力 | 93篇 |
轻工业 | 729篇 |
水利工程 | 63篇 |
石油天然气 | 180篇 |
武器工业 | 81篇 |
无线电 | 214篇 |
一般工业技术 | 751篇 |
冶金工业 | 1051篇 |
原子能技术 | 67篇 |
自动化技术 | 129篇 |
出版年
2024年 | 40篇 |
2023年 | 127篇 |
2022年 | 217篇 |
2021年 | 398篇 |
2020年 | 318篇 |
2019年 | 216篇 |
2018年 | 186篇 |
2017年 | 229篇 |
2016年 | 235篇 |
2015年 | 278篇 |
2014年 | 362篇 |
2013年 | 429篇 |
2012年 | 453篇 |
2011年 | 531篇 |
2010年 | 442篇 |
2009年 | 413篇 |
2008年 | 343篇 |
2007年 | 418篇 |
2006年 | 416篇 |
2005年 | 320篇 |
2004年 | 263篇 |
2003年 | 238篇 |
2002年 | 158篇 |
2001年 | 162篇 |
2000年 | 106篇 |
1999年 | 113篇 |
1998年 | 68篇 |
1997年 | 40篇 |
1996年 | 35篇 |
1995年 | 48篇 |
1994年 | 41篇 |
1993年 | 34篇 |
1992年 | 21篇 |
1991年 | 25篇 |
1990年 | 18篇 |
1989年 | 21篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
1958年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有7790条查询结果,搜索用时 15 毫秒
41.
Yoon Carolyn; Feinberg Fred; Hu Ping; Gutchess Angela Hall; Hedden Trey; Chen Hiu-Ying Mary; Jing Qicheng; Cui Yao; Park Denise C. 《Canadian Metallurgical Quarterly》2004,19(3):379
Understanding how aging influences cognition across different cultures has been hindered by a lack of standardized, cross-referenced verbal stimuli. This study introduces a database of such item-level stimuli for both younger and older adults, in China and the United States, and makes 3 distinct contributions. First, the authors specify which item categories generalize across age and/or cultural groups, rigorously quantifying differences among them. Second, they introduce novel, powerful methods to measure between-group differences in freely generated ranked data, the rank-ordered logit model and Hellinger Affinity. Finally, a broad archive of tested, cross-linguistic stimuli is now freely available to researchers: data, similarity measures, and all stimulus materials for 105 categories and 4 culture-by-age groups, comprising over 10,000 fully translated unique item responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
42.
PZT铁电薄膜的制备及电学性能研究 总被引:6,自引:1,他引:5
使用硝酸锆作锆源的溶胶-凝胶方法制备PZT铁电薄膜。他们的电学性能被测试包括电滞回线,电流I(t)特性,漏电流,矫顽场疲劳和老化。测到的PZT薄膜剩余极化8.2μC/cm~2,矫顽场68kV/cm.簿膜的寿命可超过10~(11)周期。 相似文献
43.
Determining contributions of source-monitoring and inhibitory function to age-related forgetting has been an elusive goal for cognitive theorists. Five studies used a verbal working memory paradigm to examine mechanisms accounting for disproportionate retroactive interference (RI) experienced with adult aging. Participants distinguished studied target-word pairs from interfering pairs that were read aloud. Source-monitoring and inhibitory task components varied through manipulations of response requirements. RI effects were primarily due to source-monitoring failures rather than to inhibitory failures. Removing both source and inhibitory components eliminated age differences in RI. When source monitoring was emphasized, RI continued to be observed in all age groups but disproportionately for older adults. Process dissociation analyses of memory found recollection decreases and familiarity increases consistent with source failures. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
44.
45.
Reviews the book, Manuel de gérontologie sociiale 2 by Jean Carette (1992). The Handbook of Social Gerontology 2 constitutes a practical complement of volume 1 which related to the social aspects of ageing and the retirement. Volume 2 relates mainly to the social intervention whose objective is to support the action and the collective mobilization individuals and associations of retirements. Using a 30-year experiment with groups of retirees, either in preparation of retirement, or in the collective action, the author approaches a new ground in gerontology. He proposes a new approach--social gerontology, (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
46.
47.
图 1所示的活塞试件 ,在开型时间为 5 0s~ 5 5s时 ,其表面温度为 (4 90± 5 )℃ ,可满足淬火要求。自然时效时间为 2 4天时 ,其机械性能可达到国标技术要求。这种新工艺有明显的经济效益。 相似文献
48.
探讨了以NdCl_3的磷酸三丁酯(TBP)溶液为主催化剂、烷基铝为助催化剂、MgCl_2为载体组成的Ziegler-Natta型催化体系引发丁二烯(Bd)聚合的某些规律。用AlEt_3作助催化剂,聚合物的顺1,4-结构含量仅为57%,反1,4-结构含量为42%;而以Al(i-Bu)_3作助催化剂,聚合物的顺1,4-结构含量为88%,反1,4-结构含量为11%。各种陈化体系中,以NdCl_3·nTBP/MgCl_2-Al(i-Bu)_3-Ip三元体系的催化活性最高,当Nd/Bd(摩尔比)为7×10~(-5)时,单体转化率达80%。低温聚合可获得高顺式、高分子量聚合物。 相似文献
49.
50.
Junya Kondoh Yoichi Tomii Katsuhiro Kawachi 《Journal of the American Ceramic Society》2003,86(12):2093-2102
Methods of suppressing decreased conductivity in 8 mol% Y2 O3 -stabilized–92 mol% ZrO2 (8YSZ) with aging were investigated. Different amounts of Sc2 O3 were doped into 8YSZ. The electrochemical properties of Sc2 O3 -doped 8YSZ were measured, and the microstructural and local structural changes were characterized. The present results indicate that an appropriate amount of Sc2 O3 doping, 3 or 4 mol%, effectively suppresses decreased conductivity with aging in 8YSZ. 相似文献