首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2597篇
  免费   142篇
  国内免费   65篇
电工技术   55篇
综合类   275篇
化学工业   220篇
金属工艺   41篇
机械仪表   251篇
建筑科学   146篇
矿业工程   13篇
能源动力   13篇
轻工业   136篇
水利工程   5篇
石油天然气   18篇
武器工业   8篇
无线电   96篇
一般工业技术   218篇
冶金工业   843篇
原子能技术   5篇
自动化技术   461篇
  2024年   6篇
  2023年   12篇
  2022年   80篇
  2021年   94篇
  2020年   48篇
  2019年   99篇
  2018年   64篇
  2017年   45篇
  2016年   43篇
  2015年   49篇
  2014年   87篇
  2013年   129篇
  2012年   102篇
  2011年   167篇
  2010年   149篇
  2009年   204篇
  2008年   170篇
  2007年   180篇
  2006年   175篇
  2005年   190篇
  2004年   131篇
  2003年   115篇
  2002年   93篇
  2001年   72篇
  2000年   29篇
  1999年   23篇
  1998年   18篇
  1997年   28篇
  1996年   15篇
  1995年   16篇
  1994年   16篇
  1993年   17篇
  1992年   11篇
  1991年   3篇
  1990年   13篇
  1989年   20篇
  1988年   14篇
  1987年   12篇
  1986年   9篇
  1985年   6篇
  1981年   2篇
  1979年   4篇
  1967年   3篇
  1966年   4篇
  1964年   4篇
  1963年   5篇
  1961年   2篇
  1957年   2篇
  1956年   3篇
  1955年   5篇
排序方式: 共有2804条查询结果,搜索用时 156 毫秒
961.
This paper improves the modeling method for the device with characteristic family presented by L. O. Chua (1977) and results in the one-dimensional fluctuating canonical piecewise-linear model. It is an efficient model. The algorithm for canonical piecewise-linear dynamic networks with one dimensional fluctuating model is discussed in detail.  相似文献   
962.
Mobile terminals have evolved from basic portable telephones to complex and diverse devices that encompass dozens of other features, ranging from tri‐dimensional games to office suites with data transmission capabilities. Variability is value: mobile terminal manufacturers must succeed in fulfilling the requirements of hundreds of mobile telecom operators worldwide, and at the same time increase the value of their brand by adopting a common user interface style while offering the features that the target end‐user category desires. This makes for practically infinite variability and creates a business problem. The complexity of the variability problem increases due to issues such as the ability to ‘plug and play’ and ‘feature descension’ (the down‐scaling of high‐end features and their introduction into lower‐end models). The main lesson we have learned from our experience in this field is that the application of relatively simple architectural patterns usually eases up management of the complexity at the architectural level. However, tackling the variability problem at the technical level is ineffective unless the organization is able to ensure the application of the solutions. We analyze the main challenges that lie behind the variability problem in mobile terminals, at both technical and organizational level, and illustrate some of the solutions we have implemented together with our product developers and system architects. Our experience calls for more applied research in the area of variability management, as well as for a number of enhancements to academic curricula. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
963.
This study focused on how factors outside the home affect the quality of mothering and fathering. Economic pressure and workload were evaluated along with the compensating role of social support on parenting. Information was gathered from 842 mothers and 573 fathers including 139 single-mother and 21 single-father families. The results showed that the nature of the strains, together with parental gender and family structure, influenced their effects on parenting. The results further revealed some gender- and strain-specific protective functions of social support on parenting. For example, economic pressure was related to increased punitive parenting, which was compensated by instrumental and emotional support among the mothers. Workload was related to less authoritative single fathering, which was compensated by instrumental support. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
964.
Recently hospitalized bipolar, manic patients (N=53) were randomly assigned to a 9-month, manual-based, family-focused psychoeducational therapy (n=28) or to an individually focused patient treatment (n=25). All patients received concurrent treatment with mood-stabilizing medications. Structured follow-up assessments were conducted at 3-month intervals for a 1-year period of active treatment and a 1-year period of posttreatment follow-up. Compared with patients in individual therapy, those in family-focused treatment were less likely to be rehospitalized during the 2-year study period. Patients in family treatment also experienced fewer mood disorder relapses over the 2 years, although they did not differ from patients in individual treatment in their likelihood of a first relapse. Results suggest that family psychoeducational treatment is a useful adjunct to pharmacotherapy in decreasing the risk of relapse and hospitalization frequently associated with bipolar disorder. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
965.
NZP族陶瓷粉体的合成方法   总被引:5,自引:0,他引:5  
简述了NZP族陶瓷粉体制备中所采用的几种合成方法的基本原理,对比了传统的固相合成、先进的共沉淀法,水热合成法及溶胶凝胶法的各自特点。  相似文献   
966.
Comments on the article by Carlson and Grotevant (see record 1988-17683-001). Carlson and Grotevant's article in this issue provides an excellent and thoughtful overview of observational rating scales as applied to entire family units. Although originally viewed as "clinical" in nature, and lacking in respectable scientific rigor and precision, these assessment devices now have become a useful and flexible approach to the complicated process of family assessment. Notwithstanding the authors' scholarly discussion of issues in utilizing these methods, and their critical review of existing rating formats, I wish to raise three points for discussion: The first concerns the relationship of micro- to macroanalytic procedures, the second focuses on reliability, and the third raises a troubling theoretical issue. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
967.
家庭用电的一些问题的探讨   总被引:1,自引:1,他引:0  
贾小星  蔡科 《山西建筑》2004,30(23):118-119
针对我国家庭用电设计的一些问题,从用电负荷的确定、导线选择、插座、刀闸等方面,介绍了国际关于电气设计的内容及要点,以满足我国家庭用电的要求,确保家庭用电的安全。  相似文献   
968.
In this study, the author describes the nature and occurrence of knowledge-construction links (KCLs) in 3 6th-grade classrooms that varied in degree of learner centeredness. KCLs are operationalized as prior learning that students bring to their current classroom experiences and include school and nonschool experiences. They are hypothesized to facilitate a knowledge-construction process that values prior learning. In the more learner-centered classroom, KCLs occurred in conjunction with open and divergent dialogue, positive reactions to students' use of prior learning, and opportunities within the classroom that allowed students to gain new experiences on which they could draw in further knowledge-construction efforts. In contrast, KCLs were ignored or viewed as inappropriate in the least learner-centered classroom, dialogue about content was convergent, and performance goals were the norm. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
969.
This research examines longitudinally associations between family risk factors and child and parent depression in 302 urban, low-income, African American adolescents (ages 9-15) and their parents across 2 waves of data collection. Diagnostic data revealed that 7.3% of parents and 3.0% of children at Time 1 and 5.4% of parents and 2.8% of children at Time 2 were clinically depressed. Regression analyses revealed that changes in family functioning were concurrently associated with changes in depression for both children and parents. Specifically, increases in conflict and decreases in parental monitoring were associated with increases in child depressive symptomatology, and increases in conflict and decreases in positive parenting were associated with increases in parental depressive symptomatology. Findings are discussed within a framework of understanding family protective factors and the prevention of depression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
970.
Using receiver operating characteristics, the authors examined outcome predictors (variables associated with outcome regardless of treatment) and moderators (variables identifying subgroups with differential treatment effectiveness) in the Multimodal Treatment Study of Children with Attention-Deficit/Hyperactivity Disorder (ADHD; MTA). Treatment response was determined using parent- and teacher-reported ADHD and oppositional defiant symptoms, with levels near or within the normal range indicating excellent response. Among 9 baseline child and family characteristics, none predicted but 3 moderated treatment response. In medication management and combined treatments, parental depressive symptoms and severity of child ADHD were associated with decreased rates of excellent response; when these 2 characteristics were present, below-average child IQ was an additional moderator. No predictors or moderators emerged for behavioral and community comparison treatments. The authors discuss conceptual and clinical implications of research on treatment moderators. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号