全文获取类型
收费全文 | 36643篇 |
免费 | 4042篇 |
国内免费 | 3025篇 |
专业分类
电工技术 | 1113篇 |
技术理论 | 8篇 |
综合类 | 4067篇 |
化学工业 | 5249篇 |
金属工艺 | 2562篇 |
机械仪表 | 1354篇 |
建筑科学 | 4866篇 |
矿业工程 | 914篇 |
能源动力 | 696篇 |
轻工业 | 1846篇 |
水利工程 | 784篇 |
石油天然气 | 1870篇 |
武器工业 | 262篇 |
无线电 | 2518篇 |
一般工业技术 | 4055篇 |
冶金工业 | 3451篇 |
原子能技术 | 332篇 |
自动化技术 | 7763篇 |
出版年
2024年 | 168篇 |
2023年 | 607篇 |
2022年 | 1108篇 |
2021年 | 1263篇 |
2020年 | 1338篇 |
2019年 | 1182篇 |
2018年 | 1126篇 |
2017年 | 1357篇 |
2016年 | 1378篇 |
2015年 | 1451篇 |
2014年 | 1954篇 |
2013年 | 2093篇 |
2012年 | 2308篇 |
2011年 | 2790篇 |
2010年 | 2206篇 |
2009年 | 2278篇 |
2008年 | 2252篇 |
2007年 | 2553篇 |
2006年 | 2254篇 |
2005年 | 1965篇 |
2004年 | 1707篇 |
2003年 | 1451篇 |
2002年 | 1212篇 |
2001年 | 933篇 |
2000年 | 681篇 |
1999年 | 615篇 |
1998年 | 490篇 |
1997年 | 386篇 |
1996年 | 340篇 |
1995年 | 287篇 |
1994年 | 288篇 |
1993年 | 199篇 |
1992年 | 161篇 |
1991年 | 118篇 |
1990年 | 120篇 |
1989年 | 96篇 |
1988年 | 54篇 |
1987年 | 53篇 |
1986年 | 52篇 |
1985年 | 50篇 |
1984年 | 52篇 |
1982年 | 34篇 |
1981年 | 36篇 |
1980年 | 41篇 |
1979年 | 36篇 |
1964年 | 50篇 |
1963年 | 40篇 |
1959年 | 31篇 |
1958年 | 31篇 |
1955年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
A 320×240 CMOS image sensor is demonstrated,which is implemented by a standard 0.6 μm 2P2M CMOS process.For reducing the chip area,each 2×2-pixel block shares a sample/hold circuit,analog-to-digital converter and 1-b memory.The 2×2 pixel pitch has an area of 40 μm×40 μm and the fill factor is about 16%.While operating at a low frame rate,the sensor dissipates a very low power by power-management circuit making pixel-level comparators in an idle state.A digital correlated double sampling,which eliminates fixed pattern noise,improves SNR of the sensor, and multiple sampling operations make the sensor have a wide dynamic range. 相似文献
72.
[Correction Notice: An erratum for this article was reported in Vol 31(2) of Canadian Psychology Psychologie Canadienne (see record 2007-08913-001). In the October 1989 issue (Vol. 30, No. 4, p. 697), Arnold Rincover's affiliation with the Ontario Institute for Studies in Education was incorrectly given as Associate Professor. He has been an Extramural Instructor at O.I.S.E.] Reviews the book, The parent-child connection by Arnold Rincover (1988). The parent-child connection is a well written book that offers valuable advice to help parents of young children evaluate and understand their children's behaviour. It also offers useful suggestions on managing child behaviour, although these parenting tips are most likely to be useful to those parents who least need them (i.e., those with numerous personal and social resources, whose children are presenting only minor behavioural difficulties). The two general themes of the book, child behaviour as communication and developmental norms as guidelines for deciding if behaviour is problematic, are well-suited to the purposes of a parent reference book. They offer an appropriate framework for discussing specific child behaviours and helping parents to determine if these behaviours are problematic in their children. This book is a welcome addition to the list of available parenting books, and may prove particularly useful for younger parents in need of accurate and understandable information about normal child development and behaviour. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
73.
Some therapists hold that the Bobo and other aggressive toys should be excluded from the playroom as they elicit acting-out behavior that is transferred to the world outside the playroom. However, many therapists view the inclusion of these items as imperative elements that facilitate positive growth and maturation in the child. Interviews with authorities in the field of play therapy support the position that the inclusion of the Bobo is not only useful, but a therapeutic necessity. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
74.
Brown Charlotte; Abe-Kim Jennifer S.; Barrio Concepcion 《Canadian Metallurgical Quarterly》2003,34(1):10
What do health care practitioners need to know about providing adequate care for depressed minority women? This article examined the prevalence of depressive symptoms and clinical depression in ethnic minorities, the extent to which current health service utilization is congruent with needs, and the effectiveness of treatments provided to ethnic minorities in the primary care setting. The impact of ethnic minority women's sociocultural context on symptom expression and help-seeking behavior is also discussed. Finally, the clinical implications for accurate assessment and treatment of ethnic minority women by both medical and mental health practitioners working in the primary care sector are addressed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
75.
The present study explores the relation among 4 personality traits associated with impulsive behavior and alcohol abuse. Personality traits were measured using the 4 subscales of the UPPS Impulsive Behavior Scale (UPPS: S. P. Whiteside & D. R. Lynam. 2001). The UPPS and measures of psychopathology were administered to clinical samples of alcohol abusers high in antisocial personality traits (AAPD), alcohol abusers low in antisocial personality traits (AA), and a control group (total N = 60). Separate analyses of variance indicated that AAPDs had significant elevations on all 4 UPPS scales, whereas the AAs and controls differed only on the Urgency subscale. However, when controlling for psychopathology, group differences on the UPPS scales disappeared. The results suggest that personality traits related to impulsive behavior are not directly related to alcohol abuse but rather are associated with the elevated levels of psychopathology found in a subtype of alcohol abusers. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
76.
Katsutoshi Yada 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2007,11(8):811-817
The aim of this paper is to propose a new system for the strategic use of customer data that includes and integrates such
differing data sources as company databases, mobile telephone networks and Internet data and is a consumer research support
system for the discovery of new marketing opportunities. This system, called CODIRO, will be discussed in this paper using
a case study of the effects on sales of processed food product television commercials. A system for verifying the validity
of consumer behavior models will also be described and discussed. Use of the CODIRO analysis system makes it easy to introduce,
into the analytic model, consumer attitude changes and in-store data of many types that have not been used to measure advertising
and promotional activity effectiveness in the past. 相似文献
77.
朝阳沟裂缝性低渗透油田井网适应性研究 总被引:23,自引:13,他引:10
通过对比分析朝阳沟裂缝性低渗透油藏与裂缝主方向分别成11.5°和22.5°的两种不同井网的开发效果,表明与裂缝成11.5°的井网与裂缝匹配性较差,开发效果相对较差。并从油藏的水驱控制程度、压力传导情况、采收率及经济效益等方面研究评价了朝1.55区井网的适应性,为指导油田的加密调整,在技术和经济两方面综合评价确定了合理的井距和井网密度,并针对朝1-55区的地质特征,提出了井网和注水方式调整办法,在朝55区块实施后,取得了较好的现场试验效果。 相似文献
78.
利用CO_2连续激光器在45钢表面进行了激光熔敷镍基合金、镍基Cr_2O_3合金和镍基WC合金,以2Cr13不锈钢为对比材料,系统地研究了激光熔敷层在不同冲击速度和腐蚀介质浓度下的腐蚀磨损特性,并根据组织分析、显微硬度测试及腐蚀磨损后的表面形貌观察,探讨了激光熔敷层的腐蚀磨损过程。结果表明:激光熔敷层的腐蚀磨损性能均比2Cr13不锈钢好。 相似文献
79.
对裂隙岩体中掏糟爆破布孔的影响因素进行了研究,并根据裂分布的情况提出相应的布孔方法和原则。对有关的工程施工具有实际意义。 相似文献
80.