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   2671篇
  免费   208篇
  国内免费   3篇
电工技术   18篇
综合类   5篇
化学工业   731篇
金属工艺   13篇
机械仪表   39篇
建筑科学   104篇
矿业工程   2篇
能源动力   47篇
轻工业   547篇
水利工程   23篇
石油天然气   13篇
无线电   101篇
一般工业技术   327篇
冶金工业   660篇
原子能技术   13篇
自动化技术   239篇
  2024年   10篇
  2023年   25篇
  2022年   85篇
  2021年   147篇
  2020年   58篇
  2019年   69篇
  2018年   102篇
  2017年   94篇
  2016年   111篇
  2015年   74篇
  2014年   112篇
  2013年   167篇
  2012年   141篇
  2011年   173篇
  2010年   127篇
  2009年   127篇
  2008年   124篇
  2007年   104篇
  2006年   96篇
  2005年   86篇
  2004年   68篇
  2003年   59篇
  2002年   59篇
  2001年   33篇
  2000年   41篇
  1999年   30篇
  1998年   37篇
  1997年   37篇
  1996年   41篇
  1995年   28篇
  1994年   35篇
  1993年   26篇
  1992年   36篇
  1991年   8篇
  1990年   24篇
  1989年   22篇
  1988年   18篇
  1987年   26篇
  1986年   19篇
  1985年   16篇
  1984年   31篇
  1983年   9篇
  1982年   10篇
  1981年   27篇
  1980年   8篇
  1979年   17篇
  1978年   11篇
  1977年   12篇
  1976年   17篇
  1974年   8篇
排序方式: 共有2882条查询结果,搜索用时 15 毫秒
81.
Computer Supported Collaborative Learning is a pedagogical approach that can be used for deploying educational games in the classroom. However, there is no clear understanding as to which technological platforms are better suited for deploying co-located collaborative games, nor the general affordances that are required. In this work we explore two different technological platforms for developing collaborative games in the classroom: one based on augmented reality technology and the other based on multiple-mice technology. In both cases, the same game was introduced to teach electrostatics and the results were compared experimentally using a real class.  相似文献   
82.
Work organization and team membership is highly complex for modern workers. Teams are often dynamic as personnel change during a project. Dynamic team members have to be actively recruited and personnel changes make it harder for participants to retain group focus. Workers are often members of multiple groups. Though prior work has identified the prevalence of multi-teaming and dynamic teams, it has been unable to explain how workers cope with the challenges the new style of work should cause. This paper systematically characterizes the modern organizational landscape from an individual perspective, by studying how people typically organize work across their multiple collaborative groups. A unique contribution of our work is to examine the interrelationships between the collaborative groups individuals typically participate in. We introduce the notion of a collaboration profile to characterize these interrelations. We expected workers to be overburdened by contributing to multiple teams often with shifting personnel. However, we found that multi-teaming involves productive interrelationships between collaborative groups that ease some of the documented challenges of dynamic teams, such as goal setting, recruiting, and group maintenance. We define a typology that describes the various types of collaborative groups workers participate in, and provide examples of productive interrelations between collaborations. In characterizing interrelations between collaborations, we provide detailed examples of how people exploit resources across their different collaborations to address the problems of working in multiple dynamic teams.  相似文献   
83.
Tobacco use is prevalent among youth with alcohol and other drug problems, yet this issue has received limited research and clinical attention. This study reports on a controlled evaluation of a cigarette smoking intervention with 54 adolescents in treatment for substance abuse, ages 13-18 (22% female). Participants were assessed at 4 time points. A greater proportion of participants in the treatment condition (n = 26) reported cessation attempts and point abstinence than did control participants (n = 28) at all time points. However, significant differences were found only for point abstinence at a 3-month follow-up. These findings provide initial support for the efficacy of a smoking cessation intervention delivered in the context of adolescent substance abuse treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
84.
Cognitive dissonance and effects of self-affirmation on dissonance arousal were examined cross-culturally. In Studies 1 and 2, European Canadians justified their choices more when they made them for themselves, whereas Asian Canadians (Study 1) or Japanese (Study 2) justified their choices more when they made them for a friend. In Study 3, an interdependent self-affirmation reduced dissonance for Asian Canadians but not for European Canadians. In Study 4, when Asian Canadians made choices for a friend, an independent self-affirmation reduced dissonance for bicultural Asian Canadians but not for monocultural Asian Canadians. These studies demonstrate that both Easterners and Westerners can experience dissonance, but culture shapes the situations in which dissonance is aroused and reduced. Implications of these cultural differences for theories of cognitive dissonance and self-affirmation are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
85.
This special issue, entitled "Evidence-Based Parent and Family Interventions in School Psychology," examines the data that support the use of interventions as methods for changing children's school-related behavior and learning problems. Taken together, the articles reflect the work of the Parent and Family Intervention domain of the Evidence-Based Interventions in School Psychology Task Force. Across the articles in this special issue, the categories of coding criteria in the Manual were used to organize the presentation of results. Six review articles on the evidence base for parent and family intervention appear next; these are followed by commentary from distinguished scholars and a brief reflective comment from the special issue editors. Parent intervention is the exclusive focus of the reviews of parent education and parent consultation. Two reviews focus on the home-school relationship including the articles on parent involvement and home-school collaboration. Two reviews include both parent and family treatments: early childhood family-focused interventions and parent training and family systems interventions. Commentary was sought from the current co-chairs of the Task Force, an expert in evidence-based practice in child clinical psychology, a researcher in family-school linkages and parent consultation, and a methodologist. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献   
86.
The aims of the present study were to examine whether written emotional disclosure would reduce distress among cancer patients and whether it would buffer the effects of high levels of social constraint (negative social responses to patients' expressions of emotion regarding their cancer) on distress. Cancer patients (N=104) were randomly assigned to write about their emotions regarding their cancer 20 min a day for 3 days or to write about a nonemotional topic. They completed questionnaires at baseline and 6 months postintervention. Results showed that written disclosure buffered the effects of social constraints on stress at the 6-month follow-up and that avoidance partly mediated these effects. The present data reinforce the notion that interventions should be tailored to patients' needs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
87.
Oxidation processes can oxidize biorecalcitrant compounds into biodegradable intermediates, which in turn can be treated less expensively by a subsequent biological process. To design such a two-step (chemical+biological) process to treat poorly characterized wastewaters, it is useful to model the time evolution of characteristic global variables, chemical oxygen demand (COD) and biochemical oxygen demand (BOD), in order to develop a useful treatment strategy based upon these classical variables. We consider two simple model reaction networks, requiring three- and five-rate constants, respectively. The first model, proposed recently, involves conversion of a nonbiodegradable species, C, into a single biodegradable intermediate S. Here, biodegradable compounds are immediate kinetic products of oxidation. In general, it is not probable that a single recalcitrant compound undergoes a single-step reaction to CO2. However, when working with complex undefined wastewaters streams, single-step reactions may be used to simplify. The second new model corresponds to a lag time in BOD formation due to the necessity of multiple partial oxidations to reach a first biodegradable intermediate. The second network includes two intermediates, I and S, which are, respectively, nonbiodegradable and biodegradable. We then compare model behavior with an unfortunately sparse literature on BOD and COD values versus time in chemical reactors, and demonstrate the convenience of the first model, and the occasional necessity of the second, which reflects the presence of early intermediates which are nonbiodegradable.  相似文献   
88.
We report in detail on the luminescence imaging setup developed within the last years in our laboratory. In this setup, the luminescence emission of silicon solar cells or silicon wafers is analyzed quantitatively. Charge carriers are excited electrically (electroluminescence) using a power supply for carrier injection or optically (photoluminescence) using a laser as illumination source. The luminescence emission arising from the radiative recombination of the stimulated charge carriers is measured spatially resolved using a camera. We give details of the various components including cameras, optical filters for electro- and photo-luminescence, the semiconductor laser and the four-quadrant power supply. We compare a silicon charged-coupled device (CCD) camera with a back-illuminated silicon CCD camera comprising an electron multiplier gain and a complementary metal oxide semiconductor indium gallium arsenide camera. For the detection of the luminescence emission of silicon we analyze the dominant noise sources along with the signal-to-noise ratio of all three cameras at different operation conditions.  相似文献   
89.
The present paper reports the amount and estimated daily mineral intake of nine elements (Ca, Mg, K, Na, P, Fe, Mn, Cr and Ni) in commercial instant coffees and coffee substitutes (n = 49). Elements were quantified by high-resolution continuum source flame (HR-CS-FAAS) and graphite furnace (HR-CS-GFAAS) atomic absorption spectrometry, while phosphorous was evaluated by a standard vanadomolybdophosphoric acid colorimetric method.Instant coffees and coffee substitutes are rich in K, Mg and P (>100 mg/100 g dw), contain Na, Ca and Fe in moderate amounts (>1 mg/100 g), and trace levels of Cr and Ni. Among the samples analysed, plain instant coffees are richer in minerals (p < 0.001), except for Na and Cr. Blends of coffee substitutes (barley, malt, chicory and rye) with coffee (20–66%) present intermediate amounts, while lower quantities are found in substitutes without coffee, particularly in barley.From a nutritional point of view the results indicate that the mean ingestion of two instant beverages per day (total of 4 g instant powder), either with or without coffee, cannot be regarded as important sources of minerals to the human diet, although providing a supplementation of some minerals, particularly Mg and Mn in instant coffees. Additionally, and for authentication purposes, the correlations observed between some elements and the coffee percentage in the blends, with particular significance for Mg amounts, provides a potential tool for the estimation of coffee in substitute blends.  相似文献   
90.
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