全文获取类型
收费全文 | 6919篇 |
免费 | 631篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 41篇 |
综合类 | 4篇 |
化学工业 | 1675篇 |
金属工艺 | 126篇 |
机械仪表 | 144篇 |
建筑科学 | 295篇 |
矿业工程 | 21篇 |
能源动力 | 155篇 |
轻工业 | 1854篇 |
水利工程 | 81篇 |
石油天然气 | 40篇 |
无线电 | 356篇 |
一般工业技术 | 1476篇 |
冶金工业 | 150篇 |
原子能技术 | 25篇 |
自动化技术 | 1110篇 |
出版年
2024年 | 25篇 |
2023年 | 92篇 |
2022年 | 118篇 |
2021年 | 244篇 |
2020年 | 207篇 |
2019年 | 235篇 |
2018年 | 353篇 |
2017年 | 367篇 |
2016年 | 344篇 |
2015年 | 251篇 |
2014年 | 341篇 |
2013年 | 748篇 |
2012年 | 492篇 |
2011年 | 500篇 |
2010年 | 392篇 |
2009年 | 361篇 |
2008年 | 388篇 |
2007年 | 368篇 |
2006年 | 292篇 |
2005年 | 151篇 |
2004年 | 154篇 |
2003年 | 156篇 |
2002年 | 148篇 |
2001年 | 125篇 |
2000年 | 105篇 |
1999年 | 86篇 |
1998年 | 71篇 |
1997年 | 49篇 |
1996年 | 46篇 |
1995年 | 53篇 |
1994年 | 44篇 |
1993年 | 25篇 |
1992年 | 24篇 |
1991年 | 18篇 |
1990年 | 15篇 |
1989年 | 15篇 |
1988年 | 17篇 |
1987年 | 5篇 |
1986年 | 11篇 |
1985年 | 16篇 |
1984年 | 23篇 |
1983年 | 20篇 |
1982年 | 14篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1976年 | 5篇 |
1973年 | 4篇 |
1967年 | 2篇 |
排序方式: 共有7553条查询结果,搜索用时 31 毫秒
101.
102.
Rodolfo Cuevas Juan-Carlos Ferrer Mathias Klapp Juan-Carlos Muñoz 《Journal of Scheduling》2016,19(1):91-106
The potential benefits of using human resources efficiently in the service sector constitute an incentive for decision makers in this industry to intelligently manage the work shifts of their employees, especially those dealing directly with customers. In the long term, they should attempt to find the right balance between employing as few labor resources as possible and keeping a high level of service. In the short run (e.g., 1 week), however, contracted staff levels cannot be adjusted, and management efforts thus focus on the efficient assignment of shifts and activities to each employee. This article proposes a mixed integer program model that solves the short-term multi-skilled workforce tour scheduling problem, enabling decision makers to simultaneously design workers’ shifts and days off, assign activities to shifts and assign those to employees so as to maximize and balance coverage of a firm’s demand for on-duty staff across multiple activities. Our model is simple enough to be solved with a commercial MIP solver calibrated by default without recurring to complex methodologies, such as extended reformulations and exact and/or heuristic column generation subroutines. A wide computational testing over 1000 randomly generated instances suggests that the model’s solution times are compatible with daily use and that multi-skilling is a significant source of labor flexibility to improve coverage of labor requirements, in particular when such requirements are negatively correlated and part-time workers are a scarce resource. 相似文献
103.
This paper proposes a novel pose (position and orientation) consensus controller for networks of heterogeneous robots modeled in the operational space. The proposed controller is a distributed proportional plus damping scheme that, with a slight modification, solves both the leader–follower and leaderless consensus problems. A singularity‐free representation, unit quaternion, is used to describe the robots orientation, and the network is represented by an undirected and connected interconnection graph. Furthermore, it is shown that the controller is robust to interconnection variable time delays. Experiments with a network of two 6‐degrees‐of‐freedom robots are presented to illustrate the performance of the proposed scheme. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
104.
Carlos Aguilar‐Ibañez Julio A. Mendoza‐Mendoza Juan C. Martinez Jose de Jesus Rubio Miguel S. Suarez‐Castanon 《国际强度与非线性控制杂志
》2015,25(12):1739-1750
》2015,25(12):1739-1750
A solution to the stabilization problem of a compact set by means of the Interconnection and Damping Assignment Passivity‐Based Control methodology, for an affine nonlinear system, was introduced. To this end, we expressed the closed‐loop system as a Port Hamiltonian system, having the property of almost all their trajectories asymptotically converge to a convenient limit set, except for a set of measure zero. It was carried out by solving a partial differential equation (PDE) or single matching condition, which allows the desired energy level or limit set E to be shaped explicitly. The control strategy was tested using the magnetic beam balance system and the pendulum actuated by a direct current motor (DC‐motor), having obtained satisfactory results. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
105.
106.
Logan Molyneux Krishnan Vasudevan Homero Gil de Zúñiga 《Journal of Computer-Mediated Communication》2015,20(4):381-399
Recent research suggests that social interactions in video games may lead to the development of community bonding and prosocial attitudes. Building on this line of research, a national survey of U.S. adults finds that gamers who develop ties with a community of fellow gamers possess gaming social capital, a new gaming‐related community construct that is shown to be a positive antecedent in predicting both face‐to‐face social capital and civic participation. 相似文献
107.
Differential protein abundance in promastigotes of nitric oxide‐sensitive and resistant Leishmania chagasi strains
下载免费PDF全文
![点击此处可从《Proteomics. Clinical applications》网站下载免费的PDF全文](/ch/ext_images/free.gif)
108.
This research focused on determining the sociocultural factors that build the social perception of the social roles of senior citizens in Chile in the 2002–2012 period. For this purpose, public opinion was studied in newspapers El Mercurio and La Cuarta. Specialized opinion included the Senior Citizen Program of Pontificia Universidad Católica de Chile, the National Service for Senior Citizens, the Social Observatory for Aging and Old Age of Universidad de Chile, and the Society of Geriatrics and Gerontology of Chile. A comprehensive methodology was used, along with a bibliographical four-stage design. The following ten sociocultural factors were identified: Health and Quality of Life, Studies and Data, Social Images of Aging, Gerontological Concepts and Sociopolitical Participation, Gerontological Policies, Plans and Principles, Aging, Production and Gender, Institutionalization, Demographic Growth, Gerontological Training, and Exclusion and Old Age. This work suggests modifying the conceptual premise that emphasizes the inexistence of a social role for elderly people with a vision centered on the heterogeneity of social roles under permanent sociocultural construction. 相似文献
109.
110.
Juan Pedro Muñoz-Gea Josemaria Malgosa-Sanahuja Pilar Manzanares-Lopez 《Peer-to-Peer Networking and Applications》2013,6(3):340-360
Recently, a new peer-assisted architecture to build content delivery systems has been presented. This architecture is based on the use of the storage capacity of end-users’ set-top boxes (STBs), connected in a peer-to-peer (P2P) manner in order to help the content servers in the delivery process. In these systems, the contents are usually split into a set of smaller pieces, called sub-streams, which are randomly injected at the STBs. The present paper is focused on Video on Demand (VoD) streaming and it is assumed that the STB-based content delivery system is deployed over the global Internet, where the clients are distributed over different ISP networks. In this scenario, three different strategies are studied for increasing the percentage of data uploaded by peers, in order to offload the content servers as much as possible. First of all, a new mechanism is presented which determines which sub-stream has to be placed at which STB by a Non-Linear Programming (NLP) formulation. A different strategy for reducing the content server load is to take advantage of the available bandwidth in the different ISP networks. In this sense, two new mechanisms for forwarding the VoD requests to different ISP networks are presented. Finally, the present paper also shows that in some situations the available uplink bandwidth is associated with STBs that do not have the required sub-streams. Regarding this concern, a new mechanism has been designed that dynamically re-allocates some streams, which are being transmitted from specific STBs, to different STBs, in order to find the necessary resources to start new streaming sessions. 相似文献