全文获取类型
收费全文 | 6536篇 |
免费 | 241篇 |
国内免费 | 45篇 |
专业分类
电工技术 | 133篇 |
综合类 | 24篇 |
化学工业 | 827篇 |
金属工艺 | 110篇 |
机械仪表 | 198篇 |
建筑科学 | 346篇 |
矿业工程 | 3篇 |
能源动力 | 148篇 |
轻工业 | 301篇 |
水利工程 | 23篇 |
石油天然气 | 25篇 |
武器工业 | 3篇 |
无线电 | 1473篇 |
一般工业技术 | 1027篇 |
冶金工业 | 1118篇 |
原子能技术 | 33篇 |
自动化技术 | 1030篇 |
出版年
2023年 | 40篇 |
2022年 | 76篇 |
2021年 | 92篇 |
2020年 | 58篇 |
2019年 | 70篇 |
2018年 | 106篇 |
2017年 | 81篇 |
2016年 | 135篇 |
2015年 | 112篇 |
2014年 | 134篇 |
2013年 | 319篇 |
2012年 | 305篇 |
2011年 | 322篇 |
2010年 | 238篇 |
2009年 | 297篇 |
2008年 | 328篇 |
2007年 | 317篇 |
2006年 | 305篇 |
2005年 | 253篇 |
2004年 | 205篇 |
2003年 | 213篇 |
2002年 | 158篇 |
2001年 | 171篇 |
2000年 | 167篇 |
1999年 | 189篇 |
1998年 | 474篇 |
1997年 | 274篇 |
1996年 | 209篇 |
1995年 | 173篇 |
1994年 | 108篇 |
1993年 | 126篇 |
1992年 | 77篇 |
1991年 | 62篇 |
1990年 | 52篇 |
1989年 | 49篇 |
1988年 | 48篇 |
1987年 | 41篇 |
1986年 | 39篇 |
1985年 | 60篇 |
1984年 | 27篇 |
1983年 | 24篇 |
1982年 | 39篇 |
1981年 | 34篇 |
1980年 | 29篇 |
1979年 | 24篇 |
1978年 | 17篇 |
1977年 | 22篇 |
1976年 | 44篇 |
1975年 | 17篇 |
1973年 | 19篇 |
排序方式: 共有6822条查询结果,搜索用时 0 毫秒
101.
We present a model of spatial navigation based on the non-convergent dynamics of brain activity. The system includes a hippocampal module that processes global spatial information and a cortical module that deals with local sensory information. We test the model using several spatial navigation paradigms: goal finding, shortcutting and detouring. Computer simulations show that the performance of the agent qualitatively matches that of animals and related models. This new approach provides a novel interpretation of how the brain accomplishes spatial navigation. 相似文献
102.
Mihai Burcea Wing-Kai Hon Hsiang-Hsuan Liu Prudence W. H. Wong David K. Y. Yau 《Journal of Scheduling》2016,19(6):687-699
We study an offline scheduling problem arising in demand response management in a smart grid. Consumers send in power requests with a flexible set of timeslots during which their requests can be served. For example, a consumer may request the dishwasher to operate for 1 h during the periods 8am to 11am or 2pm to 4pm. The grid controller, upon receiving power requests, schedules each request within the specified duration. The electricity cost is measured by a convex function of the load in each timeslot. The objective of the problem is to schedule all requests with the minimum total electricity cost. As a first attempt, we consider a special case in which the power requirement and the duration a for which a request needs service are both unit-size. For this problem, we present a polynomial time offline algorithm that gives an optimal solution and shows that the time complexity can be further improved if the given set of timeslots forms a contiguous interval. 相似文献
103.
Li Zeng Renren Liu Leo Yu Zhang Yuansheng Liu Kwok-Wo Wong 《Multimedia Tools and Applications》2016,75(10):5439-5453
Recently, an image encryption algorithm based on scrambling and Veginère cipher has been proposed. However, it was soon cryptanalyzed by Zhang et al. using a method composed of both chosen-plaintext attack and differential attacks. This paper briefly reviews the two attack approaches proposed by Zhang et al. and outlines their mathematical interpretations. Based on these approaches, we present an improved chosen-plaintext attack to further reduce the number of chosen-plaintexts required, which is proved to be optimal. Moreover, it is found that an elaborately designed known-plaintext attack can efficiently compromise the image cipher under study. This finding is confirmed by both mathematical analysis and numerical simulations. The cryptanalyzing techniques developed in this paper provide some insights for designing secure and efficient multimedia ciphers. 相似文献
104.
The supremacy of online white supremacists – an analysis of online discussions by white supremacists
A content analysis was conducted on five different white supremacist online forums to observe the discourse and types of activities occurring within. In addition, web link analysis was conducted on the forums to identify the presence of external links being posted and discussed by members. We found that members used the forums primarily for information provision, recruitment and networking. Based on these results, we discuss the implications that online hate speech have within offline settings, and the affects these activities have on Canadian citizens in light of the recent repeal of section 13 of the Canadian Human Rights Act (1985), the primary tool in Canada with which to deal with hate speech and other activities observed. The insights extracted from this research have provided novel insight into the sentiments and activities of the white supremacist movement online, a relatively unexplored venue of hate speech and propaganda online. 相似文献
105.
Research on better methods to digitally represent microscopic specimens has increased over recent decades. Opaque specimens, such as microfossils and metallurgic specimens, are often viewed using reflected light microscopy. Existing 3D surface estimation techniques for reflected light microscopy do not model reflectance, restricting the representation to only one illumination condition and making them an imperfect recreation of the experience of using an actual microscope. This paper introduces a virtual reflected-light microscopy (VRLM) system that estimates both shape and reflectance from a set of specimen images. When coupled with anaglyph creation, the system can depict both depth information and illumination cues under any desired lighting configuration. Digital representations are compact and easily viewed in an online setting. A prototype used to construct VRLM representations is comprised only of a microscope, a digital camera, a motorized stage and software. Such a system automatically acquires VRLM representations of large batches of specimens. VRLM representations are then disseminated in an interactive online environment, which allows users to change the virtual light source direction and type. Experiments demonstrate high quality VRLM representations of 500 microfossils. 相似文献
106.
Yuet Ling Wong Jieqiong Zhao 《International journal of human-computer interaction》2013,29(2):118-127
Social navigation enables emergent collaboration between independent collaborators by exposing the behavior of each individual. This is a powerful idea for web-based visualization, where the work of one user can inform other users interacting with the same visualization. Results from a crowdsourced user study evaluating the value of such social navigation cues for a geographic map service are presented. Results show significantly improved performance for participants who interacted with the map when the visual footprints of previous users were visible. 相似文献
107.
Bob Fields Paola Amaldi William Wong Satinder Gill 《International journal of human-computer interaction》2013,29(4):359-360
This study used protocol analyses and user drawings of their models of the system to investigate the “getting lost” problem in hypertext navigation. The “getting lost” problem is viewed as occurring when routine expectations of naive users, concerning appropriate linear sequences, are violated. Several ways in which users persistently attempt to work within a linear model, despite its inapplicability, are examined. The transition to more hierarchical user models is described. 相似文献
108.
Shortcut nitrification has been successfully applied in a laboratory scale nitrification-denitrification process consisting of an up-flow anaerobic sludge blanket (UASB) and an aerobic membrane bioreactor (MBR) in treating synthetic and municipal wastewater to simultaneously remove organic carbon and nitrogen. For the treatment of synthetic wastewater, the combined system exhibited a high TOC removal of 98% with a steady ammonia removal efficiency of about 98% in the MBR and a total nitrogen (TN) removal efficiency of 90%. In treating municipal wastewater, due to its low COD concentration, removal efficiencies of TOC, ammonia and TN were 70%, 98% and 60%, respectively. The biogas production was around 76.4 L/m3 wastewater when treating synthetic wastewater. However, little biogas was produced when treating municipal wastewater which was the result of low organic carbon loading to the UASB. Energy analysis has demonstrated that this novel shortcut nitrification process could consume less energy than a conventional process and have the potential of bio-energy generation via biogas production thus helping to achieve a more favorable energy balance. 相似文献
109.
110.
Lot streaming for product assembly in job shop environment 总被引:3,自引:1,他引:2
Assembly job shop scheduling problem (AJSP) is an extension of classical job shop scheduling problem (JSP). AJSP starts with JSP and appends an assembly stage to the completed jobs. Lot streaming (LS) technique is a process of splitting jobs into smaller sub-jobs such that successive operations can be overlapped. This paper combines, for the first time, LS and AJSP, extending LS applicability to both machining and assembly. To solve this complex problem, an efficient algorithm is proposed using genetic algorithms and simple dispatching rules. Experimental results suggest that equal size LS outperforms varied size LS with respect to the objective function. 相似文献