全文获取类型
收费全文 | 12615篇 |
免费 | 733篇 |
国内免费 | 373篇 |
专业分类
电工技术 | 411篇 |
综合类 | 1483篇 |
化学工业 | 2740篇 |
金属工艺 | 995篇 |
机械仪表 | 760篇 |
建筑科学 | 1269篇 |
矿业工程 | 459篇 |
能源动力 | 134篇 |
轻工业 | 415篇 |
水利工程 | 270篇 |
石油天然气 | 288篇 |
武器工业 | 55篇 |
无线电 | 634篇 |
一般工业技术 | 1377篇 |
冶金工业 | 1092篇 |
原子能技术 | 61篇 |
自动化技术 | 1278篇 |
出版年
2024年 | 19篇 |
2023年 | 141篇 |
2022年 | 152篇 |
2021年 | 288篇 |
2020年 | 298篇 |
2019年 | 247篇 |
2018年 | 215篇 |
2017年 | 268篇 |
2016年 | 310篇 |
2015年 | 349篇 |
2014年 | 630篇 |
2013年 | 1165篇 |
2012年 | 831篇 |
2011年 | 818篇 |
2010年 | 625篇 |
2009年 | 666篇 |
2008年 | 636篇 |
2007年 | 813篇 |
2006年 | 722篇 |
2005年 | 670篇 |
2004年 | 589篇 |
2003年 | 543篇 |
2002年 | 444篇 |
2001年 | 380篇 |
2000年 | 290篇 |
1999年 | 254篇 |
1998年 | 185篇 |
1997年 | 182篇 |
1996年 | 159篇 |
1995年 | 151篇 |
1994年 | 128篇 |
1993年 | 78篇 |
1992年 | 88篇 |
1991年 | 57篇 |
1990年 | 38篇 |
1989年 | 42篇 |
1988年 | 35篇 |
1987年 | 26篇 |
1986年 | 18篇 |
1985年 | 26篇 |
1984年 | 15篇 |
1983年 | 13篇 |
1982年 | 16篇 |
1981年 | 19篇 |
1980年 | 6篇 |
1964年 | 6篇 |
1963年 | 7篇 |
1961年 | 5篇 |
1957年 | 8篇 |
1955年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 193 毫秒
1.
Cecilia Berlin Lars-Ola Bligrd Maral Babapour Chafi Siw Eriksson 《人机工程学与制造业中的人性因素》2022,32(1):151-170
In any work system design intervention—for example, a physical workplace re-design, a work process change, or an equipment upgrade—it is often emphasized how important it is to involve stakeholders in the process of analysis and design, to gain their perspectives as input to the development, and ensure their future acceptance of the solution. While the users of an artifact or workplace are most often regarded as being the most important stakeholders in a design intervention, in a work-system context there may be additional influential stakeholders who influence and negotiate the design intervention's outcomes, resource allocation, requirements, and implementation. Literature shows that it is uncommon for empirical ergonomics and human factors (EHF) research to apply and report the use of any structured stakeholder identification method at all, leading to ad-hoc selections of whom to consider important. Conversely, other research fields offer a plethora of stakeholder identification and analysis methods, few of which seem to have been adopted in the EHF context. This article presents the development of a structured method for identification, classification, and qualitative analysis of stakeholders in EHF-related work system design intervention. It describes the method's EHF-related theoretical underpinnings, lessons learned from four use cases, and the incremental development of the method that has resulted in the current method procedure and visualization aids. The method, called Change Agent Infrastructure (abbreviated CHAI), has a mainly macroergonomic purpose, set on increasing the understanding of sociotechnical interactions that create the conditions for work system design intervention, and facilitating participative efforts. 相似文献
2.
三聚硫氰酸单钠盐是一种新型的多官能团化精细化学品。介绍了三聚硫氰酸单钠盐的制备方法,以及其在橡胶硫化、橡胶与金属的硫化粘合等领域的应用研究进展。 相似文献
3.
在近些年的发展中,我国经济水平得到了一个显著的增长,经济的增长推动了城市化的发展进程,进入21世纪,城市绿化工程建设规模呈一个稳定上升的趋势,在这种大的社会环境形势下,如何做好绿化大管径供水管线的安装与腐蚀防护工作成为了行业关注的焦点。大管径供水管线的稳定性关系着城市发展的可持续性,要从多方面做好大管径供水管线的安装工作,采取有效的措施应对管线腐蚀问题。 相似文献
4.
Anti-washout and tissue adhesion properties are essential for the clinical application of injectable bone materials. In this study, we prepared calcium phosphate cement (CPC) with anti-washout and tissue adhesion properties and attempted to build covalent bonds between CPC and the amino groups in bone tissue under a self-regulating pH system in the CPC (acidic to basic). The results of push-out tests demonstrated that a significant enhancement (from 6.42 ± 0.76 N to 61.5 ± 4.09 N) in tissue adhesion was obtained with the addition of 6% (w/w) oxidized sodium alginate (OSA) in CPC. The FTIR, XRD, anti-washout test, XPS, pH test, and SEM results suggested that the synergistic effect of OSA-citric acid (CA) led to the formation of a three-dimensional gel network structure in the CPC, and the Schiff base reaction between aldehyde and amino groups induced adhesion between CPC and the bone tissue. Further, the addition of less OSA had no significant negative effect on the hydration properties of CPC. Our work aims to promote the development of injectable bone material in clinical applications. 相似文献
5.
6.
Maria Cristina Righetti Patrizia Cinelli Laura Aliotta Elisa Bianchi Fabio Tricoli Maurizia Seggiani Andrea Lazzeri 《Polymer International》2022,71(1):47-56
This paper reports the thermal, morphological and mechanical properties of environmentally friendly poly(3-hydroxybutyrate) (PHB)/poly(butylene succinate) (PBS) and PHB/poly[(butylene succinate)-co-(butylene adipate)] (PBSA) blends, prepared by melt mixing. The blends are known to be immiscible, as also confirmed by the thermodynamic analysis here presented. A detailed quantification of the crystalline and amorphous fractions was performed, in order to interpret the mechanical properties of the blends. As expected, the ductility increased with increasing PBS or PBSA amount, but in parallel the decrease in the elastic modulus appeared limited. Surprisingly, the elastic modulus was found properly described by the rule of mixtures in the whole composition range, thus attesting mechanical compatibility between the two blend components. This unusual behavior has been explained as due to co-continuous morphology, present in a wide composition range, but also at the same time as the result of shrinkage occurring during sequential crystallization of the two components, which can lead to physical adhesion between matrix and dispersed phase. For the first time, the elastic moduli of the crystalline and mobile amorphous fractions of PBS and PBSA and of the mobile amorphous fraction of PHB at ambient temperature have been estimated through a mechanical modelling approach. © 2021 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry. 相似文献
7.
Lack of constraint-free crane path planning is one of the critical concerns in the dynamic on-site assembly process of prefabrication housing production (PHP). For decades, researchers and practitioners have endeavored to improve both the efficiency and safety of crane path planning from either static environment or re-planning the path when colliding with constraints or periodically updating the path in the dynamic environment. However, there is a lack of approach related to the in-depth exploration of the nature of dynamic constraints so as to assist the crane operators in making adaptive path re-planning decisions by categorizing and prioritizing constraints. To address this issue, this study develops the smart work packaging (SWP)-enabled constraints optimization service. This service embraces the core characteristics of SWP, including adaptivity, sociability, and autonomy to achieve autonomous initial path planning, networked constraints classification, and adaptive decisions on path re-planning. This service is simulated and verified in the BIM environment, and it is found that SWP-enabled constraints optimization service can generate the constraint-free path when it is necessary. 相似文献
8.
Outcome‐based ventilation: A framework for assessing performance,health, and energy impacts to inform office building ventilation decisions 下载免费PDF全文
This article presents an outcome‐based ventilation (OBV) framework, which combines competing ventilation impacts into a monetized loss function ($/occ/h) used to inform ventilation rate decisions. The OBV framework, developed for U.S. offices, considers six outcomes of increasing ventilation: profitable outcomes realized from improvements in occupant work performance and sick leave absenteeism; health outcomes from occupant exposure to outdoor fine particles and ozone; and energy outcomes from electricity and natural gas usage. We used the literature to set low, medium, and high reference values for OBV loss function parameters, and evaluated the framework and outcome‐based ventilation rates using a simulated U.S. office stock dataset and a case study in New York City. With parameters for all outcomes set at medium values derived from literature‐based central estimates, higher ventilation rates’ profitable benefits dominated negative health and energy impacts, and the OBV framework suggested ventilation should be ≥45 L/s/occ, much higher than the baseline ~8.5 L/s/occ rate prescribed by ASHRAE 62.1. Only when combining very low parameter estimates for profitable impacts with very high ones for health and energy impacts were all outcomes on the same order. Even then, however, outcome‐based ventilation rates were often twice the baseline rate or more. 相似文献
9.
针对传统低压回路电阻测试仪只能在被测设备停电时使用的一大限制,本文提出并设计了一种新型低压回路电阻测试仪。该仪器可在低压设备运行状态下对其回路电阻进行测量,在保证测量精度的前提下减少了设备停电率,大大提高了工作效率。 相似文献
10.