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   20168篇
  免费   1518篇
  国内免费   522篇
电工技术   647篇
技术理论   1篇
综合类   1734篇
化学工业   3924篇
金属工艺   471篇
机械仪表   751篇
建筑科学   1814篇
矿业工程   417篇
能源动力   378篇
轻工业   2074篇
水利工程   267篇
石油天然气   319篇
武器工业   73篇
无线电   902篇
一般工业技术   3305篇
冶金工业   917篇
原子能技术   138篇
自动化技术   4076篇
  2024年   66篇
  2023年   271篇
  2022年   334篇
  2021年   572篇
  2020年   573篇
  2019年   585篇
  2018年   544篇
  2017年   650篇
  2016年   725篇
  2015年   732篇
  2014年   1222篇
  2013年   1251篇
  2012年   1434篇
  2011年   1639篇
  2010年   1242篇
  2009年   1246篇
  2008年   1022篇
  2007年   1227篇
  2006年   1024篇
  2005年   834篇
  2004年   729篇
  2003年   634篇
  2002年   541篇
  2001年   412篇
  2000年   338篇
  1999年   318篇
  1998年   275篇
  1997年   229篇
  1996年   168篇
  1995年   184篇
  1994年   120篇
  1993年   112篇
  1992年   85篇
  1991年   65篇
  1990年   67篇
  1989年   76篇
  1988年   77篇
  1987年   46篇
  1986年   43篇
  1985年   58篇
  1984年   73篇
  1983年   89篇
  1982年   90篇
  1981年   29篇
  1980年   30篇
  1979年   21篇
  1978年   19篇
  1977年   17篇
  1959年   5篇
  1955年   11篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
Our interest lies in solving sum of squares (SOS) relaxations of large-scale unconstrained polynomial optimization problems. Because interior-point methods for solving these problems are severely limited by the large-scale, we are motivated to explore efficient implementations of an accelerated first-order method to solve this class of problems. By exploiting special structural properties of this problem class, we greatly reduce the computational cost of the first-order method at each iteration. We report promising computational results as well as a curious observation about the behaviour of the first-order method for the SOS relaxations of the unconstrained polynomial optimization problem.  相似文献   
992.
Most surfaces, be it from a fine‐art artifact or a mechanical object, are characterized by a strong self‐similarity. This property finds its source in the natural structures of objects but also in the fabrication processes: regularity of the sculpting technique, or machine tool. In this paper, we propose to exploit the self‐similarity of the underlying shapes for compressing point cloud surfaces which can contain millions of points at a very high precision. Our approach locally resamples the point cloud in order to highlight the self‐similarity of the shape, while remaining consistent with the original shape and the scanner precision. It then uses this self‐similarity to create an ad hoc dictionary on which the local neighborhoods will be sparsely represented, thus allowing for a light‐weight representation of the total surface. We demonstrate the validity of our approach on several point clouds from fine‐arts and mechanical objects, as well as a urban scene. In addition, we show that our approach also achieves a filtering of noise whose magnitude is smaller than the scanner precision.  相似文献   
993.
B. Gunter 《技术计量学》2013,55(4):384-385
We introduce a very general “forward” method of data analysis that starts from a small, robustly chosen subset of the data and shows the effect of adding observations by a forward search. Powerful diagnostic procedures result: The observations are ordered by their agreement with the proposed transformation, masking is overcome, and the inferential effect of each observation is clear. We apply the resulting method to the transformation of both univariate and multivariate data. Other applications of the forward search are mentioned.  相似文献   
994.
吕贻龙 《钢结构》2014,(6):40-42,55
通过对外露式柱脚的受力分析,结合工程实例,对国内常用的锚栓计算方法进行比较,并对GB 50011-2010《建筑抗震设计规范》中对于柱脚锚栓的规定进行论证,可供设计人员参考。  相似文献   
995.
The decay and termite resistance and effects of a robust leaching process on the efficacy of zinc borate-incorporated particleboard were examined. Particleboards (300 × 300 × 15 mm) prepared from particles of mixed wood species generated from demolished construction materials were incorporated with zinc borate at target retentions of 0%, 1%, 1.5% and 2% of the particle weight. An in-line treatment method was utilized to introduce the powdered chemical during the blending stage. ICP analysis indicated that the amount of zinc borate was not lost during manufacturing. Standard static bending tests demonstrated that there was no significant loss in mechanical properties. The decay and termite tests indicated that the efficacy of zinc borate at a higher retention was enough to suppress the biological activity, even after application of a robust leaching process.  相似文献   
996.
The use of fibre reinforced polymers (FRPs) to strengthen reinforced concrete (RC) structures has gained a wide popularity in the last decades. Although many experimental and analytical studies are available in literature, some issues are still under discussion in the research communities. Since the typical failure mode of FRP–concrete joints is reported to be debonding of the composite from the concrete substrate [1], the estimation of the bond strength between FRP and concrete substrate represents a key issue for the proper use of this technology. For this reason, several analytical models for the evaluation of the FRP–concrete bond strength and few models for the estimation of the effective bond length were proposed (some of them are included in design codes/recommendations/guidelines); however they were not assessed by means of an appropriate experimental database.This work shows an assessment of twenty analytical models for the evaluation of the FRP–concrete bond strength. The assessment is based on the analysis of a wide experimental database collected from the literature. The results are provided distinguishing between the test setup adopted (single or double shear test, bending test) and the material used (post impregnated sheets or pre impregnated laminates). The accuracy of each model was evaluated by means of a simplified statistical analysis. The influence of the test setup and basic material on the accuracy of the model used was analysed as well. Lastly, the accuracy of twelve available models in providing an estimation of the effective bond length was also assessed.  相似文献   
997.
Within a warehouse, the picking activity often relies on human operators. Therefore, when designing and evaluating a manual picking system, it is important to consider that, besides the high flexibility the pickers are able to warrant, they inevitably require an additional effort due to their ergonomic working conditions. In this paper, the authors propose a new model to consider such additional effort, starting from the concepts of human availability and rest allowance. The new method allows the evaluation of the current configuration of a certain warehouse, considering two different operative situations (directly employed operators and indirectly employed ones). Moreover, it makes it possible to estimate and to understand the benefits that can be achieved by introducing some ergonomic improvements. The proposed procedure has also been applied to a real industrial case study.  相似文献   
998.
朱世君 《城市建筑》2014,(21):194-194
电力规划在城市建设规划中占的地位很重要,不仅保障了城市供电系统的正常运行,而且优秀的电力规划对于城市建设经济成本的节约也有一定作用。因此为了保障整个城市建设规划的良好进行,电力规划工作必须完成好。  相似文献   
999.
Studies of the targets of anti-viral compounds are hot topics in the field of pesticide research. Various efficient anti-TMV (Tobacco Mosaic Virus) compounds, such as Ningnanmycin (NNM), Antofine (ATF), Dufulin (DFL) and Bingqingxiao (BQX) are available. However, the mechanisms of the action of these compounds on targets remain unclear. To further study the mechanism of the action of the anti-TMV inhibitors, the TMV coat protein (TMV CP) was expressed and self-assembled into four-layer aggregate disks in vitro, which could be reassembled into infectious virus particles with TMV RNA. The interactions between the anti-TMV compounds and the TMV CP disk were analyzed by size exclusion chromatography, isothermal titration calorimetry and native-polyacrylamide gel electrophoresis methods. The results revealed that assembly of the four-layer aggregate disk was inhibited by NNM; it changed the four-layer aggregate disk into trimers, and affected the regular assembly of TMV CP and TMV RNA. The four-layer aggregate disk of TMV CP was little inhibited by ATF, DFL and BQX. Our results provide original data, as well as new strategies and methods, for research on the mechanism of action of anti-viral drugs.  相似文献   
1000.
In this paper we present WEEV (Writing Environment for Educational Video games), a methodology for educational point-and-click adventure game authoring. Our approach aims to allow educators to actively collaborate in the educational game development process, using a narrative-based representation. WEEV is based on a pragmatic reinterpretation of previous works on narrativity and video games, enhanced by the use of a novel visual language to represent the flow of the story or narrative. The WEEV methodology has been implemented into an actual tool based on the already established <e-Adventure> platform for educational games. This tool was improved with feedback gathered from formative evaluation, end-users testing (i.e. educators), and actual use in the development of an educational game. The system, still under development, presents some user-interaction problems along with a need for the educational effectiveness of the resulting games to be further analyzed. However, this paper highlights that, according to the qualitative results of evaluations, WEEV can indeed be successfully applied to simplify the game creation process and that by using representations of games that educators can understand, WEEV can help provide educational value to games.  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