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   1059篇
  免费   16篇
  国内免费   4篇
电工技术   1篇
综合类   7篇
化学工业   86篇
金属工艺   3篇
机械仪表   6篇
建筑科学   15篇
矿业工程   1篇
轻工业   31篇
水利工程   5篇
武器工业   6篇
无线电   26篇
一般工业技术   29篇
冶金工业   729篇
原子能技术   1篇
自动化技术   133篇
  2024年   5篇
  2023年   6篇
  2022年   18篇
  2021年   24篇
  2020年   10篇
  2019年   13篇
  2018年   6篇
  2017年   14篇
  2016年   4篇
  2015年   18篇
  2014年   10篇
  2013年   21篇
  2012年   32篇
  2011年   89篇
  2010年   81篇
  2009年   75篇
  2008年   77篇
  2007年   92篇
  2006年   64篇
  2005年   65篇
  2004年   77篇
  2003年   71篇
  2002年   49篇
  2001年   37篇
  2000年   7篇
  1999年   4篇
  1998年   3篇
  1997年   5篇
  1996年   3篇
  1995年   10篇
  1994年   13篇
  1993年   4篇
  1992年   7篇
  1991年   4篇
  1990年   2篇
  1989年   5篇
  1988年   3篇
  1987年   2篇
  1980年   2篇
  1975年   2篇
  1965年   5篇
  1964年   5篇
  1963年   8篇
  1962年   4篇
  1961年   4篇
  1960年   4篇
  1959年   2篇
  1958年   2篇
  1956年   2篇
  1955年   1篇
排序方式: 共有1079条查询结果,搜索用时 0 毫秒
1.

This study followed the introduction of the Arthritis Source website into the existing teaching practices of Arthritis Foundation Helpline volunteers. The goal was to examine what factors may affect a particular group of educators adopt a potentially valuable Internet tool into an existing instructional environment. Defining the possible uses of the website in reference to the volunteers' actual job duties helped provide a clearer understanding of how the volunteers might use this new technology. The researchers used qualitative techniques to focus on three volunteers who experienced different physical, environmental and cognitive means that impacted their use of the new tool. Each volunteer experienced varying levels of motivation in areas of learning, satisfaction and responses to outside influences. Each volunteer also had varying amounts of opportunity prompts in which to interact or refer the website. Consequently, Helpline volunteers experienced different rates of adopting the information-intensive website into their traditional work system.  相似文献   
2.
《Ergonomics》2012,55(8):871-880
Work-related chronic injuries occur in muscles, tendons, and nerves. Epidemiological, histological, and physiological data confirm their often disputed physical basis. Terms such as repetitive strain injury and cumulative trauma disorder, when used as a diagnosis, have obscured the issue for they are really statements of causation. Definitive diagnosis is required both to treat and prevent such injuries. Precise terminology that identifies the tissue and its pathology is required. A detailed assessment methodology is described that allows a precise diagnosis. A clear relationship to work stress is necessary both to establish the cause and formulate prevention strategies. Treatment must begin early and be appropriate to the tissue and the nature of the injury. Examples are presented and discussed. Early treatment begins before too much damage has been done and yields better results.  相似文献   
3.
Martin  S.Banks  Kurt  Akeley  David  M.  Hoffman  Ahna  R.  Girshick  王鹏 《现代显示》2009,20(2):17-20
传统的立体显示是通过聚焦诱导,进行深度视觉模糊调节,从而达到立体视觉效果。现在,科研人员开发了一种新型技术——聚焦修正。通过这项技术,将聚焦诱导和深度视觉模仿同步进行,可以使立体景象显示更加快速、准确,同时减轻观看者的视觉疲劳度。  相似文献   
4.
Some postfire annuals with dormant seeds use heat or chemical cues from charred wood to synchronize their germination with the postfire environment. We report that wood smoke and polar extracts of wood smoke, but not the ash of burned wood, contain potent cue(s) that stimulate germination in the postfire annual plant,Nicotiana attenuata. We examined the responses of seeds from six populations of plants from southwest Utah to extracts of smoke and found the proportion of viable seeds that germinated in the presence of smoke cues to vary between populations but to be consistent between generations. With the most dormant genotypes, we examine three mechanisms by which smoke-derived chemical cues may stimulate germination (chemical scarification of the seed coat and nutritive- and signal-mediated stimulation of germination) and report that the response is consistent with the signal-mediated mechanism. The germination cue(s) found in smoke are produced by the burning of hay, hardwood branches, leaves, and, to a lesser degree, cellulose. Moreover, the cues are found in the common food condiment, liquid smoke, and we find no significant differences between brands. With a bioassay-driven fractionation of liquid smoke, we identified 71 compounds in active fractions by GC-MS and AA spectrometry. However, when these compounds were tested in pure form or in combinations that mimicked the composition of active fractions over a range of concentrations, they failed to stimulate germination to the same degree that smoke fractions did. Moreover, enzymatic oxidation of some of these compounds also failed to stimulate germination. In addition, we tested 43 additional compounds also reported from smoke, 85 compounds that were structurally similar to those reported from smoke and 34 compounds reported to influence germination in other species. Of the 233 compounds tested, 16 proved to inhibit germination at the concentrations tested, and none reproduced the activity of wood smoke. By thermally desorbing smoke produced by cellulose combustions that was trapped on Chromosorb 101, we demonstrate that the cue is desorbed between 125 and 150°C. We estimate that the germination cues are active at concentrations of less than 1 pg/seed and, due to their chromatographic behavior, infer that a number of different chemical structures are active. In separate experiments, we demonstrate that cues remain active for at least 53 days in soil under greenhouse conditions and that the application of aqucous extracts of smoke to soil containing seeds results in dramatic increases in germination of artificial seed banks. Hence, although the chemical nature of the germination cue remains elusive, the stability of the germination cues, their water-solubility, and their activity in low concentrations suggest that these cues could serve as powerful tools for the examination of dormant seed banks and the selective factors thought to be important in the evolution of postfire plant communities.  相似文献   
5.
    
The detection or discrimination of the second of 2 targets in a rapid serial visual presentation (RSVP) task is often temporarily impaired-a phenomenon termed the attentional blink. This study demonstrated that the attentional blink also affects localization performance. Spatial cues pointed out the possible target positions in a subsequent visual search display. When cues were presented inside an attentional blink (as induced by an RSVP task), the observers' capacity to use them was reduced. This effect was not due to attention being highly focused, to general task switching costs, or to complete unawareness of the cues. Instead, the blink induced a systematic localization bias toward the fovea, reflecting what appears to be spatial compression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
6.
    
The neuroscience of memory enriches and expands our theory of psychoanalytic interaction. There are 2 broad modes of processing memory: implicit (never experienced in symbolic form) and explicit (which is symbolic). Memory is not a thing, but a process, activated by a retrieval cue that is either external or internal. Each memory is an amalgam of the memory itself and the retrieval cue. Using these phenomena derived from the neuroscience of memory, the authors argue that (a) the analyst acts as a retrieval cue making any memory a coconstructed phenomenon; (b) each memory is constructed, transformed, and expanded anew, incrementally leading to new networks and change; and (c) implicit memory, lacking symbolic content, is an underutilized component of psychoanalytic attention. Clinical examples are used as illustrations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
7.
面对主流计算平台对框架轻量化的需求,设计一种基于多任务结构的轻量化抠图框架.将总体任务拆分为两类子任务,其中一类任务用来在语义层面上为高级特征分类,区分前景背景与未知区域的特征;另一类任务用于计算前景与背景图层的线性组合权重.通过与特征分类任务共享高级特征网络的权值获得精准的前景特征,再与低级别卷积特征相融合.所提出的模型能够生成精准的抠图掩膜,同时优化卷积神经网络来实现模型轻量化.在Composition 1K数据集上对比不同方法的实验结果:在分辨率为640×640的输入条件下,所提方法比DIM (deep image matting)和AdaMatting (adaptation and matting)方法分别减少19%和81%的空间消耗;对于同样的数据输入,所提方法需要的处理时间只有DIM消耗时间的五分之一.  相似文献   
8.
为了解决最大稳定极值区(MSER)提取过程中产生的大量重复文本区域和非文本区域难以被剔除影响算法精度的问题,提出了一种基于树修剪和多特征融合的场景文本检测方法。首先提取出边缘叠加的MSER作为文本候选区域;其次设计了一种MSER树修剪算法剔除重复文本区域;然后采用贝叶斯分类器融合多特征剔除非文本区域;最后设定了一系列相似性标准合并文本区域。ICDAR 2011数据集(f=76.8%)上的实验结果低于目前最好的算法[19],但算法在速度上具有明显的优势。  相似文献   
9.
Bullfrogs (Rana catesbeiana), native to eastern North America, were introduced into Oregon in the 1930's. Bullfrogs are highly efficient predators that are known to eat a variety of prey including other amphibians. In laboratory experiments, we investigated whether juvenile Pacific treefrogs (Hyla regilla) recognize adult bullfrogs as a predatory threat. The ability of prey animals to acquire recognition of an introduced predator has important implications for survival of the prey. We found that treefrogs from a population that co-occurred with bullfrogs showed a strong avoidance of chemical cues of bullfrogs. In contrast, treefrogs from a population that did not co-occur with bullfrogs, did not respond to the bullfrog cues. Additional experiments showed that both populations of treefrogs use chemical cues to mediate predation risk. Treefrogs from both populations avoided chemical alarm cues from injured conspecifics.  相似文献   
10.
Metal foreign bodies in the eye are commonly removed utilizing a surgical approach through the vitreous cavity, which requires a maintained ocular pressure by infusion of replacement “irrigation solution”, i.e., electrolyte. However, when in contact with aerated electrolyte, if the fragment comprises galvanized steel, the component metals can act as a bimetallic zinc/steel cell, thereby electrochemically generating injurious amounts of hydroxyl ion OH. The effect on this electrochemical reaction of the compositions of the irrigation solutions in use, and of their analogues, has thus been investigated, to seek the least damaging. The inter-metallic current relates directly to the rate of the injurious reaction, hence amperometry has been the principal probe employed in our study. Establishing reproducible conditions of contact between electrolyte and the steel–zinc combination forms a major focus of the study, which is to attain amperometric reproducibility in the comparison of the electrolytes. Geometry-sensitive directed injection of test solution into a cell with pre-fixed separate steel and Zn electrodes achieved the desiderata. Besides potentiometry and amperometry, pH and buffering by the various test solutions, and the effects of surfactants, were also examined. Free-radical intermediates in the oxygen processes are further injurious suspects. Anaerobic conditions that would preclude both intermediates and OH are unfortunately damaging to the structures of the eye, so alternative surgical procedures are needed. Anti-corrosion aspects are considered.
D. R. RosseinskyEmail:
  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