全文获取类型
收费全文 | 550878篇 |
免费 | 38951篇 |
国内免费 | 21274篇 |
专业分类
电工技术 | 29842篇 |
技术理论 | 34篇 |
综合类 | 32475篇 |
化学工业 | 87235篇 |
金属工艺 | 31093篇 |
机械仪表 | 32278篇 |
建筑科学 | 39911篇 |
矿业工程 | 15292篇 |
能源动力 | 14463篇 |
轻工业 | 34579篇 |
水利工程 | 10394篇 |
石油天然气 | 27651篇 |
武器工业 | 4122篇 |
无线电 | 60142篇 |
一般工业技术 | 68753篇 |
冶金工业 | 30197篇 |
原子能技术 | 5076篇 |
自动化技术 | 87566篇 |
出版年
2024年 | 1982篇 |
2023年 | 7119篇 |
2022年 | 13206篇 |
2021年 | 18624篇 |
2020年 | 13921篇 |
2019年 | 11508篇 |
2018年 | 25616篇 |
2017年 | 26562篇 |
2016年 | 21884篇 |
2015年 | 19095篇 |
2014年 | 23553篇 |
2013年 | 29099篇 |
2012年 | 34073篇 |
2011年 | 42363篇 |
2010年 | 37508篇 |
2009年 | 33341篇 |
2008年 | 34189篇 |
2007年 | 34279篇 |
2006年 | 26971篇 |
2005年 | 23909篇 |
2004年 | 16343篇 |
2003年 | 14406篇 |
2002年 | 13044篇 |
2001年 | 10999篇 |
2000年 | 10693篇 |
1999年 | 11362篇 |
1998年 | 8833篇 |
1997年 | 7524篇 |
1996年 | 7102篇 |
1995年 | 5984篇 |
1994年 | 5026篇 |
1993年 | 3591篇 |
1992年 | 3006篇 |
1991年 | 2182篇 |
1990年 | 1805篇 |
1989年 | 1502篇 |
1988年 | 1220篇 |
1987年 | 964篇 |
1986年 | 770篇 |
1985年 | 718篇 |
1984年 | 633篇 |
1983年 | 460篇 |
1982年 | 453篇 |
1981年 | 407篇 |
1980年 | 374篇 |
1979年 | 319篇 |
1978年 | 258篇 |
1977年 | 234篇 |
1976年 | 216篇 |
1975年 | 202篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Xu Baowen Zhang Weifeng 《电子科学学刊(英文版)》2002,19(4)
The users' interest can be mined from the web cache and can be used widely. The interest can be specialized by the two-tuple (term, weight) in the simple interest model, in which the association relations are not mined, and then the interest cannot be associated in expressing the users' interest. Based on analyzing the WWW cache model, this letter brings forward a two-dimensional interest model and gives the interrelated methods on how to store the two-dimensional interest model effectively. 相似文献
82.
游梁式抽油机二次平衡分析 总被引:1,自引:0,他引:1
为解决游梁式抽油机能耗大、效率低的问题,设计了二次平衡装置。这种装置通过是挂在抽油机后端的平衡重的平衡作用,降低一次平衡曲柄轴净扭矩的两个峰值,达到减少能耗提高效率的目的。对抽油机的二次平衡作了较详尽的理论分析,给出了实行二次平衡后曲柄轴净扭矩的计算公式和安装二次平衡装置前后曲柄轴净扭矩曲线图。在大庆油田两口井上进行的现场试验结果表明,安装二次平衡装置后,两口井年节约电费分别为0.25万元和1.17万元,经济效益明显。 相似文献
83.
Simultaneous determination of six ephedrines in urine sample has been achieved by high performance liquid chromatography on a Lichrospher RP-18 column, using methylamphetamine as internal standard. The 6 ephedrines are well separated in 25 minutes with resolution better than 1.8. This method has high recovery, selectivity and reproducibility, and the linearity is satisfactory from 1.5 micrograms/ml to 25 micrograms/ml with correlation coefficients better than 0.999. 相似文献
84.
85.
86.
14 medicated hypertensive, 15 nonmedicated mild hypertensive, 39 normotensive, and 13 hypotensive adults participated in a 1–2 hr laboratory experiment that assessed each S's symptoms, moods, and estimates of systolic blood pressure (SBP) relative to actual SBP levels. Several self-reports and autonomic measures were collected during and after each of 22 tasks. Within-S correlations indicated that all Ss could estimate SBP at levels greater than chance. Further, 68% of the Ss evidenced at least 1 significant symptom–SBP correlation. Although medicated hypertensives believed they could estimate their BP more accurately than other groups, they were actually no more accurate than the other Ss. They also evidenced far fewer empirically derived symptom–SBP and emotion–SBP correlations than any other group. Overall, blood pressure (BP) beliefs were largely inaccurate. If these erroneous beliefs can be eliminated, Ss may be able to estimate BP fluctuations more accurately. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
87.
Lewis Gloria J.; Greenburg Sharon L.; Hatch David B. 《Canadian Metallurgical Quarterly》1988,19(1):81
We report the results of the first national survey of psychologists in private practice regarding their participation in peer consultation groups. The sample (71% return) was drawn from 800 randomly selected psychologists listed in the National Register of Health Service Providers in Psychology. We found that 23% of the sample currently belonged to peer consultation groups, and 24% had belonged in the past. Of those not currently in groups, 61% expressed the desire to belong if one were available. There were virtually no significant demographic differences between current members and nonmembers. We examined the following group characteristics: formation, length of existence, size, membership, leadership, theoretical orientation, range of experience, time and place, content, and group process. Groups tended to be small, informal, and leaderless; however, we found great variation among groups on all dimensions. Findings also showed a high degree of satisfaction with membership. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
88.
89.
90.
国际上许多标准化组织都在对自动交换光网络的相关技术和标准规范进行研究。本文介绍了ITU-T、IETF和OIF等几个主要的标准化组织在自动交换光网络标准方面的进展情况。 相似文献