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   7727篇
  免费   177篇
  国内免费   145篇
电工技术   169篇
技术理论   1篇
综合类   520篇
化学工业   762篇
金属工艺   325篇
机械仪表   694篇
建筑科学   688篇
矿业工程   266篇
能源动力   283篇
轻工业   559篇
水利工程   58篇
石油天然气   321篇
武器工业   28篇
无线电   773篇
一般工业技术   390篇
冶金工业   260篇
原子能技术   30篇
自动化技术   1922篇
  2024年   2篇
  2023年   43篇
  2022年   40篇
  2021年   132篇
  2020年   190篇
  2019年   113篇
  2018年   72篇
  2017年   90篇
  2016年   160篇
  2015年   175篇
  2014年   423篇
  2013年   341篇
  2012年   443篇
  2011年   604篇
  2010年   482篇
  2009年   380篇
  2008年   403篇
  2007年   459篇
  2006年   446篇
  2005年   452篇
  2004年   352篇
  2003年   350篇
  2002年   319篇
  2001年   311篇
  2000年   225篇
  1999年   222篇
  1998年   192篇
  1997年   135篇
  1996年   106篇
  1995年   92篇
  1994年   68篇
  1993年   44篇
  1992年   27篇
  1991年   36篇
  1990年   27篇
  1989年   24篇
  1988年   6篇
  1987年   5篇
  1986年   10篇
  1985年   2篇
  1984年   10篇
  1983年   7篇
  1982年   9篇
  1981年   7篇
  1980年   8篇
  1979年   4篇
  1974年   1篇
排序方式: 共有8049条查询结果,搜索用时 16 毫秒
21.
Agent-based modeling (ABM) techniques for studying human-technical systems face two important challenges. First, agent behavioral rules are often ad hoc, making it difficult to assess the implications of these models within the larger theoretical context. Second, the lack of relevant empirical data precludes many models from being appropriately initialized and validated, limiting the value of such models for exploring emergent properties or for policy evaluation. To address these issues, in this paper we present a theoretically-based and empirically-driven agent-based model of technology adoption, with an application to residential solar photovoltaic (PV). Using household-level resolution for demographic, attitudinal, social network, and environmental variables, the integrated ABM framework we develop is applied to real-world data covering 2004–2013 for a residential solar PV program at the city scale. Two applications of the model focusing on rebate program design are also presented.  相似文献   
22.
Science Based Innovation relies on effective Technology Transfer efforts. Defining strategies that increase high-technology projects success in the market is a necessary and challenging activity. This comprises elements like market uncertainty and the need for timely decision making within an environment of limited resources (economic, time, human, among others). In this context, Technology Intelligence (TI) generates useful knowledge to reduce risk and improve decision making. This work provides a tool to identify and qualitatively measure different risks; highlighted by previous TI activities. Such risks, their level and mitigation alternatives are also discussed. Furthermore, we create a simple, yet useful tool to calculate a risk score for technology projects at early stages of development. This tool was developed in a Technology Transfer Office to foster the development of entrepreneurial ventures.  相似文献   
23.
This essay paper focuses on how the idea and use of technology is gradually reorganizing not only the structural arrangements but also redefining relationships and relational patterns. In particular reference to new technological applications and sites that are increasingly used by people for networking and bonding, there is a macro-discourse of being and staying connected through technology. Such platforms assume an easy access or an imagined availability of the other person at all times. Such availability also assumes psychological availability of the person, despite any personal circumstances he/she may be in. Experiencing the compressed space and time has given birth to the debate of quality of life and relations surrounding it vs. the constant flux of technology that restricts the psychological freedom while facilitating a structural freedom to communicate. Technology is an artifact that not only symbolizes values of ease and convenience but also has the potential to affect the deeper assumptions and values people hold about life and relationships. Thus, it mediates our personal, social and organizational realities, pushing us to live in dual worlds.  相似文献   
24.
Heat-bonded nonwoven geotextiles (HBNGs) made from synthetic fibers are widely used in engineering practices. One of the challenges on the way is to link the properties of fibers and the fabric's microstructure to the deformation and failure mechanisms of HBNGs. In this study, a random distribution geometry method was developed to reproduce the complex fibrous structure of HBNG. A piecewise linear model was adopted to reproduce the nonlinear stress-strain relationships of single fibers. The present method has been successfully applied in the simulation of uniaxial and biaxial tensile tests and puncture test. The orientation distribution of fibers and the mechanical behaviors (e.g., deformation, strain localization, force-strain relationship) of HBNG specimen were reasonably simulated. Specifically, the hourglass shape during uniaxial tensile test, the axisymmetric deformation pattern during biaxial tensile test and the trumpet shape during puncture test were all well reproduced. The present method provides an applicable tool to study the complicated mechanical behaviors of HBNG and is also helpful to obtain a better understanding of its deformation and failure mechanisms.  相似文献   
25.
Agroindustrial by-products are an abundant source of biocompounds that contain valuable nutrients, which are not exploited. In this work, lignocellulosic wastes (LW) were used in submerged fermentation (SmF) and solid-state fermentation (SSF) by Aspergillus niger NRRL3 to obtain valuable enzymes required in industries. SmF using soya bean hulls (SH), wheat bran (WB) and a by-product of wheat flour (F) produced the highest activities of endo-1,4-β-xylanase (Xyl) and endo-1,4-β-D-glucanase (EG) being at least 3 times lower than those obtained by SSF. The highest ratio of Xyl to EG was obtained in SmF with F. Xyl obtained by SmF with WB was the most thermally resistant. The enzymatic extract obtained in SmF using SH presented a high power of saccharification. The production of enzymes for further application such as bioethanol generation process revalue these LW and can help offset growing environmental problems.  相似文献   
26.
Rice production encountered several challenges, especially among rural farmers in Northern Ghana. The current debate encompasses the belief of cultural norms and religious values as the right theory for the sustainability of agriculture. The belief in abstracts is prioritised to the adoption of improved rice. This paper examined the value attached to traditional rice varieties as a result of societal beliefs, and theoretically underpinned by the Dual-system hypothesis. The finding from three ethnic and religious groups through a survey indicates heterogeneity in the results but also demonstrates the factual importance of culture and religion. This paper, therefore, proposes a new way of categorising farming; as a business and a belief and that policy stream aim at small scale, rural farmers with belief peculiarities needs to adopt cultural and religious strategies to promote adoption.  相似文献   
27.
红花檵木作为一种彩色叶植物广泛应用于园林造景当中,目前在园林景观建设中红花檵木主要以低矮灌木的形式存在,由于其景观应用形式的单一化,严重制约了红花檵木生态、景观、经济价值的充分发挥以及相关行业的进一步发展。文章从红花檵木的生态、生理习性为理论基础出发,通过对两种红花檵木仿生古桩景制作材料及方法的介绍,公开了一种红花檵木古桩景快速成型园林景观应用的新形式、新方法,达到丰富红花檵木景观应用形式,提升其生态、景观价值的目的。同时应用形式的多样化,能促进红花檵木相关上下游产业的发展,为红花檵木景观产业注入新的活力。  相似文献   
28.
毛雪 《石化技术》2020,(2):62-62,69
本文通过对注水配套工艺的优化研究,有效提高奈曼油田分注率和配注合格率,提高精细注水开发效果。  相似文献   
29.
BackgroundDigitalizing food using 3-Dimensional (3D) printing is an incipient sector that has a great potential of producing customized food with complex geometries, tailored texture and nutritional content. Yet, its application is still limited and the process utility is under the investigation of many researchers.Scope and approachThe main objective of this review was to analyze and compare published articles pertaining 3D food printing to ensure how to reach compatibility between the huge varieties of food ingredients and their corresponding best printing parameters. Different from previously published reviews in the same journal by Lipton et al. (2015) and Liu et al. (2017), this review focuses in depth on optimizing extrusion based food printing which supports the widest array of food and maintains numerous shapes and textures. The benefits and limitations of 3D food printing were critically reviewed from a different perspective while providing ample mechanisms to overcome those barriers.Key findings and conclusionsFour main obstacles hamper the printing process: ordinance and guidelines, food shelf life, ingredients restrictions and post processing. Unity and integrity between material properties and process parameters is the key for a best end product. For each group, specific criteria should be monitored: rheological, textural, physiochemical and sensorial properties of the material its self in accordance with the process parameters of nozzle diameter, nozzle height, printing speeds and temperature of printing. It is hoped that this paper will unlock further research on investigating a wider range of food printing ingredients and their influence on customer acceptability.  相似文献   
30.
宗学文  刘洁  权坤  周升栋 《塑料工业》2020,(3):78-81,88
在光固化光敏树脂成型过程中,聚四氟乙烯离型膜会在树脂液位的波动影响下发生变形,进而影响光固化制件的精度,因此需要减小离型膜在制件过程的变形量,确保其相对稳定。首先分析树脂液位变化,通过液位变化量,等效出树脂液波动带给离型膜的载荷,建立离型膜受力模型。然后基于离型薄膜的挠度变形理论,应用Ansys软件进行模拟研究,对不施加预应力和施加不同预应力作用下的离型膜变形结果分析,结果表明施加预应力有利于提高离型膜稳定性,且施加预应力为2. 645M Pa时离型膜受到树脂波动影响最小,位置精度变化在0. 01 mm。  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