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   1444篇
  免费   53篇
  国内免费   2篇
电工技术   12篇
化学工业   223篇
金属工艺   4篇
机械仪表   33篇
建筑科学   56篇
矿业工程   4篇
能源动力   21篇
轻工业   118篇
水利工程   19篇
石油天然气   3篇
无线电   152篇
一般工业技术   253篇
冶金工业   423篇
原子能技术   9篇
自动化技术   169篇
  2023年   12篇
  2022年   11篇
  2021年   21篇
  2020年   15篇
  2019年   23篇
  2018年   19篇
  2017年   29篇
  2016年   22篇
  2015年   14篇
  2014年   21篇
  2013年   72篇
  2012年   43篇
  2011年   58篇
  2010年   44篇
  2009年   32篇
  2008年   58篇
  2007年   56篇
  2006年   43篇
  2005年   36篇
  2004年   44篇
  2003年   44篇
  2002年   25篇
  2001年   38篇
  2000年   41篇
  1999年   44篇
  1998年   96篇
  1997年   72篇
  1996年   45篇
  1995年   36篇
  1994年   24篇
  1993年   41篇
  1992年   30篇
  1991年   13篇
  1990年   22篇
  1989年   23篇
  1988年   21篇
  1987年   12篇
  1986年   21篇
  1985年   8篇
  1984年   13篇
  1983年   12篇
  1982年   11篇
  1981年   9篇
  1980年   12篇
  1979年   14篇
  1978年   19篇
  1977年   16篇
  1976年   19篇
  1975年   6篇
  1974年   9篇
排序方式: 共有1499条查询结果,搜索用时 15 毫秒
81.
M. Rothbart and B. Park (1986) demonstrated that, consistent with the common negativity bias, positive traits are difficult to confirm and easy to disconfirm, whereas the opposite is true for negative traits. This article extends their analysis by showing that trait (dis-)confirmability is moderated by trait content (warmth vs. competence). Study 1 identifies a trait sample representative of warmth and competence. Study 2 shows a strong negativity effect for warmth and a reduced (or absent) negativity effect for competence. Study 3 examines trait properties related to the behavioral range of the trait possessor and to the motivational goals of the perceiver as predictors of trait (dis-)confirmability. The theoretical and practical implications of the authors' findings are discussed, and avenues for future research are suggested. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
82.
Sight-word instruction can improve functioning with various daily, recreational, and work-related tasks among children with moderate to severe disabilities. Previous research has demonstrated the effectiveness of drill methods to teach sight words if the model contains at least 50% known items, which would also increase the number of opportunities to respond (OTR) to the target item. The current study taught five sight words each day to a child diagnosed as moderately mentally retarded using high OTR and moderate OTR conditions and a drill ratio of 10% unknown to 90% known. Results suggested that the high OTR condition led to better retention than the moderate OTR despite containing an equal ratio of unknown to known items between them. Implications for practicing school psychologists and future research are included. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
83.
Objective: Therapeutic processes in cardiac rehabilitation programs are virtually unexamined. Models were tested by which changes in the working alliance between patient and staff (agreement on goals/tasks; emotional bond) may affect outcomes in conjunction with changes in patient self-efficacy to change their diets and increase exercise. Design: Cardiac patients (n = 79) participated in a 12-week program, and completed assessments at early, mid, and late treatment. Main Outcome Measures: Changes in cardiac depression, physical health, perceived exertion during exercise, rate/pressure product at submaximal exercise tolerance, weight loss, return to work, total fat intake. Results: Early-treatment changes in agreement on goals/tasks were related to changes in psychosocial factors and perceived exertion during exercise independent of effects of changes in self-efficacy. Early-treatment changes in goals/tasks and self-efficacy interacted to predict changes in cardiorespiratory fitness, weight loss, and return to work such that patients high on both goals/tasks and self-efficacy showed the most gains. Conclusion: Sound therapeutic relationships between patients and staff may play an important role in facilitating the achievement of a wide-range of salutary outcomes during cardiac rehabilitation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
84.
Abstract— A scalable manufacturing process for fabricating active‐matrix backplanes on low‐cost flexible substrates, a key enabler for electronic‐paper displays, is presented. This process is based on solution processing, ink‐jet printing, and laser patterning. A multilayer architecture is employed to enable high aperture ratio and array performance. These backplanes were combined with E Ink electrophoretic media to create high‐performance displays that have high contrast, are bistable, and can be flexed repeatedly to a radius of curvature of 5 mm.  相似文献   
85.
Physics-based flow visualization techniques seek to mimic laboratory flow visualization methods with virtual analogues. In this work we describe the rendering of a virtual rheoscopic fluid to produce images with results strikingly similar to laboratory experiments with real-world rheoscopic fluids using products such as Kalliroscope. These fluid additives consist of microscopic, anisotropic particles which, when suspended in the flow, align with both the flow velocity and the local shear to produce high-quality depictions of complex flow structures. Our virtual rheoscopic fluid is produced by defining a closed-form formula for the orientation of shear layers in the flow and using this orientation to volume render the flow as a material with anisotropic reflectance and transparency. Examples are presented for natural convection, thermocapillary convection, and Taylor-Couette flow simulations. The latter agree well with photographs of experimental results of Taylor-Couette flows from the literature.  相似文献   
86.
87.
Highly accurate real‐time localization is of fundamental importance for the safety and efficiency of planetary rovers exploring the surface of Mars. Mars rover operations rely on vision‐based systems to avoid hazards as well as plan safe routes. However, vision‐based systems operate on the assumption that sufficient visual texture is visible in the scene. This poses a challenge for vision‐based navigation on Mars where regions lacking visual texture are prevalent. To overcome this, we make use of the ability of the rover to actively steer the visual sensor to improve fault tolerance and maximize the perception performance. This paper answers the question of where and when to look by presenting a method for predicting the sensor trajectory that maximizes the localization performance of the rover. This is accomplished by an online assessment of possible trajectories using synthetic, future camera views created from previous observations of the scene. The proposed trajectories are quantified and chosen based on the expected localization performance. In this study, we validate the proposed method in field experiments at the Jet Propulsion Laboratory (JPL) Mars Yard. Furthermore, multiple performance metrics are identified and evaluated for reducing the overall runtime of the algorithm. We show how actively steering the perception system increases the localization accuracy compared with traditional fixed‐sensor configurations.  相似文献   
88.
A technique is proposed for specifying universal quantification and existential quantification (combined with negation) in a two-dimensional (graphical) database query language. Unlike other approaches that provide set operators to simulate universal quantification, this technique allows a direct representation of universal quantification. Syntactic constructs for specifying universal and existential quantifications, two-dimensional translation of universal quantification to existential quantification (with negation), and translation of existentially quantified two-dimensional queries to relational queries are presented. The resulting relational queries can be processed directly by many existing database systems. The authors claim that this technique renders universal quantifications easy to understand. To substantiate this claim, they provide a simple, easy-to-follow guideline for constructing universally quantified queries  相似文献   
89.
The positional distribution of fatty acids in the choline and ethanolamine phosphoglycerides of the L1210 murine leukemia cells was determined and compared to that of normal mouse lymphocytes. The major phospholipids of both cell types had appreciable degrees of positional specificity as evident from the higher percentage of saturated fatty acids in position 1 and of polyunsaturated fatty acids in position 2. The L1210 cells had less arachidonate and more linoleate in position 2 of choline and ethanolamine phosphoglycerides as compared to the normal lymphocytes. However, there were similar proportions of saturated, monoenoic and polyenoic fatty acids in positions 1 and 2 of the phospholipids of the L1210 leukemia cells and the lymphocytes. These data demonstrate that fatty acid positional specificity is retained in the major phospholipids of this rapidly growing tumor.  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