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   7802篇
  免费   335篇
  国内免费   11篇
电工技术   88篇
综合类   5篇
化学工业   1960篇
金属工艺   135篇
机械仪表   116篇
建筑科学   393篇
矿业工程   12篇
能源动力   203篇
轻工业   939篇
水利工程   59篇
石油天然气   120篇
武器工业   1篇
无线电   463篇
一般工业技术   1163篇
冶金工业   1457篇
原子能技术   56篇
自动化技术   978篇
  2022年   129篇
  2021年   369篇
  2020年   142篇
  2019年   128篇
  2018年   158篇
  2017年   145篇
  2016年   176篇
  2015年   157篇
  2014年   180篇
  2013年   503篇
  2012年   340篇
  2011年   394篇
  2010年   275篇
  2009年   295篇
  2008年   314篇
  2007年   318篇
  2006年   268篇
  2005年   249篇
  2004年   221篇
  2003年   195篇
  2002年   190篇
  2001年   112篇
  2000年   109篇
  1999年   112篇
  1998年   94篇
  1997年   96篇
  1996年   122篇
  1995年   91篇
  1994年   80篇
  1993年   95篇
  1992年   90篇
  1991年   65篇
  1990年   81篇
  1989年   95篇
  1988年   78篇
  1987年   88篇
  1986年   80篇
  1985年   103篇
  1984年   112篇
  1983年   83篇
  1982年   75篇
  1981年   86篇
  1980年   63篇
  1979年   96篇
  1978年   68篇
  1977年   78篇
  1976年   56篇
  1975年   65篇
  1974年   57篇
  1973年   78篇
排序方式: 共有8148条查询结果,搜索用时 343 毫秒
21.
Comments on the proposal by L. H. Levy et al (see record 1984-27507-001) for a new charter for clinical psychology—human services psychology. Current trends suggest that both clinical and counseling psychology are becoming eclectic and health oriented. Clinical psychology appears to be becoming more involved in community psychology and to be tempering its remedial role with the preventive role. Counseling psychology appears to be becoming less involved in its vocational and preventive roles and more involved in the remedial role. It is concluded that clinical and counseling psychology have come to be increasingly similar and could be integrated into a human services psychology. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
22.
23.
Epoxy-functional spontaneous gradient copolymers of glycidyl methacrylate (G) and n-butyl acrylate (B) were synthesized via atom transfer radical polymerization (ATRP). The copolymerization reactions were carried out in toluene solution at 70 °C, using methyl 2-bromopropionate (MBrP) as initiator and copper chloride with N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (PMDETA) as the catalyst system. The kinetic behaviour of the statistical copolymerizations was studied in a wide composition interval with molar fractions of G ranging from 0.10 to 0.75. The synthesized copolymers were characterized by size exclusion chromatography (SEC) and nuclear magnetic resonance (NMR) spectroscopy. 1H NMR was employed to determine the copolymer composition, demonstrating the gradient character of the copolymers along the main chain in the whole monomer conversion interval. Apart from this, the sequence distribution and stereoregularity were analyzed. These microstructural experimental data agreed well with those calculated from Mayo-Lewis terminal model (MLTM) and a Bernoullian statistic with an isotacticity parameter of σG = 0.28 and a coisotacticity parameter of σ = 0.30.  相似文献   
24.
The present study presents the synthesis of unsaturated polyester resins using only one glycol i.e., ethylene glycol. Polyesters of inorganic solubility in styrene were prepared. Properties of the resins in the noncrosslinked state in the process of crosslinking and after curing were studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3143–3150, 2006  相似文献   
25.
We present the results from a user study looking at the ability of observers to mentally integrate wind direction and magnitude over a vector field. The data set chosen for the study is an MM5 (PSU/NCAR Mesoscale Model) simulation of Hurricane Lili over the Gulf of Mexico as it approaches the southeastern United States. Nine observers participated in the study. This study investigates the effect of layering on the observer's ability to determine the magnitude and direction of a vector field. We found a tendency for observers to underestimate the magnitude of the vectors and a counter‐clockwise bias when determining the average direction of a vector field. We completed an additional study with two observers to try to uncover the source of the counter‐clockwise bias. These results have direct implications to atmospheric scientists, but may also be able to be applied to other fields that use 2D vector fields.  相似文献   
26.
Previous research on organizational practices is replete with contradictory evidence regarding their effects. Here, the authors argue that these contradictory findings may have occurred because researchers have often examined complex practice combinations and have failed to investigate a broad variety of firm-level outcomes. Thus, past research may obscure important differential effects of specific practices on specific firm-level outcomes. Extending this research, the authors develop hypotheses about the effects of practices that (a) enable information sharing, (b) set boundaries, and (c) enable teams on 3 different firm-level outcomes: financial performance, customer service, and quality. Relationships are tested in a sample of observations from over 200 Fortune 1000 firms. Results indicate that information-sharing practices were positively related to financial performance 1 year following implementation of the practices, boundary-setting practices were positively related to firm-level customer service, and team-enabling practices were related to firm-level quality. No single set of practices predicted all 3 firm-level outcomes, indicating practice-specific effects. These findings help resolve the theoretical tension in the literature regarding the effects of organizational practices and offer guidance as to how to best target practices to increase specific work-related outcomes. Implications for theory, research, and practice are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
27.
State space explosion is a key problem in the analysis of finite state systems. The sweep-line method is a state exploration method which uses a notion of progress to allow states to be deleted from memory when they are no longer required. This reduces the peak number of states that need to be stored, while still exploring the full state space. The technique shows promise but has never achieved reductions greater than about a factor of 10 in the number of states stored in memory for industrially relevant examples. This paper discusses sweep-line analysis of the connection management procedures of a new Internet standard, the Datagram Congestion Control Protocol (DCCP). As the intuitive approaches to sweep-line analysis are not effective, we introduce new variables to track progress. This creates further state explosion. However, when used with the sweep-line, the peak number of states is reduced by over two orders of magnitude compared with the original. Importantly, this allows DCCP to be analysed for larger parameter values. Somsak Vanit-Anunchai was partially supported by an Australian Research Council Discovery Grant (DP0559927) and Suranaree University of Technology. Guy Edward Gallasch was supported by an Australian Research Council Discovery Grant (DP0559927).  相似文献   
28.
Resilience, the ability to adapt or absorb disturbance, disruption, and change, may be increased by team processes in a complex, socio-technical system. In particular, collaborative cross-checking is a strategy where at least two individuals or groups with different perspectives examine the others’ assumptions and/or actions to assess validity or accuracy. With this strategy, erroneous assessments or actions can be detected quickly enough to mitigate or eliminate negative consequences. In this paper, we seek to add to the understanding of the elements that are needed in effective cross-checking and the limitations of the strategy. We define collaborative cross-checking, describe in detail three healthcare incidents where collaborative cross-checks played a key role, and discuss the implications of emerging patterns.  相似文献   
29.
This paper discusses a new application of data mining, quantifying the importance of responding to trigger events with reactive contacts. Trigger events happen during a customer’s lifecycle and indicate some change in the relationship with the company. If detected early, the company can respond to the problem and retain the customer; otherwise the customer may switch to another company. It is usually easy to identify many potential trigger events. What is needed is a way of prioritizing which events demand interventions. We conceptualize the trigger event problem and show how survival analysis can be used to quantify the importance of addressing various trigger events. The method is illustrated on four real data sets from different industries and countries.  相似文献   
30.
Objective: To replicate and extend P. A. Lichtenberg and colleagues' (1996) cross-disciplinary intervention to improve physical and mental health among older adults. Participants: 14 depressed older adults (6 treatment, 8 control). Setting: The short-term rehabilitation unit of an urban nursing home. Intervention: Occupational therapists were trained to treat depression using pleasant events and cognitive-behavioral therapies. Outcome Measures: Geriatric Depression Scale, the Short Form-12, and the Multi-Level Assessment Instrument: Activities of Daily Living. Results: No significant group differences were found in physical or mental health. However, more control group members (75%) than treatment group members (33%) were depressed at study completion. Conclusions: The treatment of depressive symptoms can be integrated with a nonmental health treatment modality. (PsycINFO Database Record (c) 2011 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