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   3569篇
  免费   73篇
电工技术   32篇
综合类   5篇
化学工业   634篇
金属工艺   51篇
机械仪表   80篇
建筑科学   161篇
矿业工程   8篇
能源动力   119篇
轻工业   375篇
水利工程   33篇
石油天然气   40篇
武器工业   1篇
无线电   309篇
一般工业技术   458篇
冶金工业   889篇
原子能技术   31篇
自动化技术   416篇
  2023年   10篇
  2022年   10篇
  2021年   21篇
  2020年   22篇
  2019年   27篇
  2018年   39篇
  2017年   42篇
  2016年   46篇
  2015年   34篇
  2014年   72篇
  2013年   230篇
  2012年   127篇
  2011年   180篇
  2010年   162篇
  2009年   146篇
  2008年   182篇
  2007年   207篇
  2006年   176篇
  2005年   134篇
  2004年   106篇
  2003年   90篇
  2002年   84篇
  2001年   69篇
  2000年   66篇
  1999年   90篇
  1998年   119篇
  1997年   93篇
  1996年   76篇
  1995年   73篇
  1994年   75篇
  1993年   74篇
  1992年   63篇
  1991年   38篇
  1990年   59篇
  1989年   51篇
  1988年   39篇
  1987年   48篇
  1986年   39篇
  1985年   53篇
  1984年   53篇
  1983年   50篇
  1982年   28篇
  1981年   36篇
  1980年   13篇
  1979年   30篇
  1978年   14篇
  1977年   21篇
  1976年   26篇
  1975年   19篇
  1973年   13篇
排序方式: 共有3642条查询结果,搜索用时 15 毫秒
71.

Locative Media Experiences (LMEs) have significant potential in enabling visitors to engage with the places that they visit through an appreciation of local history. For example, a visitor to Berlin that is exploring remnants of the Berlin Wall may be encouraged to appreciate (or in part experience) the falling of the Berlin wall by consuming multimedia directly related to her current location such as listening to audio recordings of the assembled crowds on 10th November 1989. However, despite the growing popularity of enabling technologies (such as GPS-equipped smart phones and tablets), the availability of tools that support the authoring of LMEs is limited. In addition, mobile apps that support the consumption of LMEs typically adopt an approach that precludes users from being able to respond with their own multimedia contributions. In this article we describe the design and evaluation of the SHARC2.0 framework that has been developed as part of our long-term and participatory engagement with the rural village of Wray in the north of England. Wray has very limited cellular data coverage which has placed a requirement on the framework and associated tools to operate without reliance on network connectivity. A field study is presented which featured a LME relating to Wray’s local history and which contained multimedia content contributed by members of the community including historic photos (taken from an existing ‘Digital Noticeboard’ system), audio-clips (from a local historian and village residents) and video (contributed during a design workshop). The novelty of our approach relates to the ability of multiple authors to contribute to a LME in-situ, and the utilisation of personal cloud storage for storing the contents associated with a multi-authored LME.

  相似文献   
72.
73.
With the advent of intelligent computer aided design systems, companies such as Boeing are embarking on an era in which core competitive engineering knowledge and design rationale is being encoded in software systems. The promise of this technology is that this knowledge can be leveraged across many different designs, product families, and even different uses (e.g., generative process planning for manufacturing). The current state of the practice attempts to achieve this goal through the reuse of software components. A fundamental problem with this approach to knowledge sharing and reuse is that what we are trying to reuse is software—the end artifact in a long and complicated process that goes from requirement specifications, through a process of design, to implementations. Knowledge sharing and reuse can not easily and uniformly occur at the software level. So what can be done as an alternative? This paper describes a theory, methodology, language, and tool for the semi-automatic development and maintenance of engineering software from requirement specifications. In essence, this paradigm for software development and maintenance is one that explicitly captures requirement specifications, designs, implementations, and the refinement processes that lead from requirements all the way down to software. By recording this entire refinement history, we stand a better chance of leveraging knowledge for different uses.  相似文献   
74.
The primary aims of this study were to establish a client injury baseline for the New Zealand adventure tourism and adventure sport sector, and to examine patterns and trends in claims for injury during participation in adventure activities. Content analysis of narrative text data for compensated injuries occurring in a place for recreation and sport over a 12-month period produced over 15,000 cases involving adventure tourism and adventure sport. As found in previous studies in New Zealand, highest claim counts were observed for activities that are often undertaken independently, rather than commercially. Horse riding, tramping, surfing and mountain biking were found to have highest claim counts, while hang gliding/paragliding/parasailing and jet boating injuries had highest claim costs, suggesting greatest injury severity. Highest claim incidence was observed for horse riding, with female claimants over-represented for this activity. Younger male claimants comprised the largest proportion of adventure injuries, and falls were the most common injury mechanism.  相似文献   
75.
76.
Bakers' yeast reduction of (2E)-3-(2-furanyl)-2-methyl-2-propenal yielded the synthetic intermediate, (2S)-3-(2-furanyl)-2-methylpropanol, of high chiral purity (>97% ee) for the synthesis of the enantiomers of 2,5-dimethylheptadecane and 7-methylheptadecane, two synergistic sex pheromone components of the western hemlock looper (WHL),Lambdina fiscellaria lugubrosa Hulst. In electrophysiological bioassays, (7S)- but not (7R)-7-methylheptadecane elicited strong antennal responses by male WHL antennae. In field trapping experiments, addition of (7S)- but not (7R)-7-methylheptadecane to (5R,11S)-5,11-dimethylheptadecane, the major sex pheromone component of WHL, increased attraction. Attraction to (5R,11S)-5,11-dimethylheptadecane in combination with (7S)-7-methyiheptadecane was further enhanced by the addition of (5S)- but not (5R)-2,5-dimethylheptadecane. Similarly, attraction to (5R,11S)-5,11-dimethylheptadecane combined with (5S)-2,5-dimethylheptadecane increased when 7S- but not (7R)-7-methylheptadecane was added as a third component. We conclude that (7S)-7-methylheptadecane and (5S)-2,5-dimethylheptadecane are the synergistic sex pheromone components of WHL. The synthetic methodology described is applicable to the synthesis of chiral methyl-branched pheromones in other orders of the Insecta, particularly Coleoptera, Diptera and Orthoptera.  相似文献   
77.
78.
79.
80.
Yeast display is a powerful tool for increasing the affinity and thermal stability of scFv antibodies through directed evolution. Mammalian calmodulin (CaM) is a highly conserved signaling protein that undergoes structural changes upon Ca(2+) binding. In an attempt to generate conformation-specific antibodies for proteomic applications, a selection against CaM was undertaken. Flow cytometry-based screening strategies to isolate easily scFv recognizing CaM in either the Ca(2+)-bound (Ca(2+)-CaM) or Ca(2+)-free (apo-CaM) states are presented. Both full-length scFv and single-domain VH only clones were isolated. One scFv clone having very high affinity (K(d) = 0.8 nM) and specificity (>1000-fold) for Ca(2+)-CaM was obtained from de novo selections. Subsequent directed evolution allowed the development of antibodies with higher affinity (K(d) = 1 nM) and specificity (>300-fold) for apo-CaM from a parental single-domain clone with both a modest affinity and specificity for that particular isoform. CaM-binding activity was unexpectedly lost upon conversion of both conformation-specific clones into soluble fragments. However, these results demonstrate that conformation-specific antibodies can be quickly and easily isolated by directed evolution using the yeast display platform.  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