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   1417篇
  免费   53篇
  国内免费   2篇
电工技术   14篇
综合类   1篇
化学工业   385篇
金属工艺   51篇
机械仪表   29篇
建筑科学   64篇
矿业工程   1篇
能源动力   52篇
轻工业   171篇
水利工程   5篇
无线电   148篇
一般工业技术   282篇
冶金工业   58篇
原子能技术   10篇
自动化技术   201篇
  2024年   2篇
  2023年   10篇
  2022年   30篇
  2021年   52篇
  2020年   25篇
  2019年   26篇
  2018年   26篇
  2017年   22篇
  2016年   32篇
  2015年   27篇
  2014年   52篇
  2013年   109篇
  2012年   81篇
  2011年   132篇
  2010年   97篇
  2009年   83篇
  2008年   83篇
  2007年   63篇
  2006年   66篇
  2005年   49篇
  2004年   38篇
  2003年   41篇
  2002年   37篇
  2001年   20篇
  2000年   19篇
  1999年   22篇
  1998年   15篇
  1997年   31篇
  1996年   17篇
  1995年   22篇
  1994年   15篇
  1993年   12篇
  1992年   10篇
  1991年   13篇
  1990年   4篇
  1989年   10篇
  1988年   4篇
  1987年   12篇
  1985年   10篇
  1984年   6篇
  1983年   4篇
  1982年   5篇
  1981年   3篇
  1980年   6篇
  1979年   9篇
  1978年   7篇
  1977年   3篇
  1976年   3篇
  1973年   3篇
  1972年   1篇
排序方式: 共有1472条查询结果,搜索用时 15 毫秒
81.
Multiple-pass cell for very-long-path infrared spectrometry   总被引:1,自引:0,他引:1  
A multiple-pass cell for mid-IR spectrometry that has been designed to operate in an evacuable environmental chamber is described. Using this new modified White arrangement, we can significantly increase the path length while keeping the spectrometric beam stable. An approximate expression that ties the number of reflections to the optimal signal-to-noise ratio in multiple-reflection cells is derived.  相似文献   
82.
We deal with the permutation routing problem on graphs modeling interconnection networks. In our model, calledrouting via factors, at each routing step, the communication pattern is a directed 1-factor in a symmetric digraph. This adds a new feature, that of continuous packet movement, to preciously studied routing types, where the routing of a permutation is reduced to a sequence of permutations from a given class. We especially focus on bipartite graphs and we give sufficient conditions for a graph to be rearrangeable in our model. We propose a general technic for routing via factors that we apply to the 2D mesh and the hypercube.  相似文献   
83.
Agricultural production is highly dependent on climate variability in many parts of the world. In particular, drought may severely reduce crop yields, potentially affecting food availability at local, regional, and global scales. The Food and Agriculture Organization of the United Nations (FAO) operates the Global Early Warning System (GIEWS), which monitors global food supply and demand. One of the key challenges is to obtain synoptic information on a recurrent and timely basis about drought-affected agricultural zones. This is needed to quickly identify areas requiring immediate attention. The Agricultural Stress Index System (ASIS), based on imagery from the Advanced Very High Resolution Radiometer (AVHRR) sensors on board the National Oceanic and Atmospheric Administration (NOAA) and Meteorological Operational Satellite (METOP) satellites, was specifically developed to meet this need. The system is based on a methodology developed by Rojas, Vrieling, and Rembold over the African continent. This approach has been modified and adapted to the global scale to produce an agricultural stress index (ASI) representing, per administrative unit, the percentage of cropland (or pasture) areas affected by drought over the growing season. The vegetation health index (VHI), based on normalized difference vegetation index (NDVI) and temperature anomalies, is used as a drought indicator. A fused time series of AVHRR data from METOP and NOAA was used to produce a consistent time series of VHI at 1 km resolution. Global phenology maps, indicating the number of growing seasons and their start and end dates, were derived from a multi-annual image set of SPOT-Vegetation (1999–2011). The VHI time series and phenology maps were then combined to produce the ASI for the years 1984 to the present. This allowed evaluation of the suitability of the ASIS to identify drought using historical reports and ancillary data. As a result of this analysis, ASIS was positively evaluated to support the FAO early warning system.  相似文献   
84.
Structural and Multidisciplinary Optimization - Topology optimization is a tool that supports the creativity of structural-designers and is used in various industries, from automotive to...  相似文献   
85.
This article presents a procedure for the design of bulk acoustic wave (BAW) filters. The procedure consists of optimizing the modified Butterworth‐Van Dyke model of each resonator, considering appropriate technological parameters. The approach is demonstrated first to design a classical aluminum nitride‐based BAW filter but remains valid for other piezoelectric layers, considering either longitudinal or transverse acoustic wave coupling. The approach is finally applied to the design of a lithium niobate (LiNbO3) BAW filter for wide‐band filtering applications. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.  相似文献   
86.
High-level synthesis (HLS) is a potential solution to increase the productivity of FPGA-based real-time image processing development. It allows designers to reap the benefits of hardware implementation directly from the algorithm behaviors specified using C-like languages with high abstraction level. In order to close the performance gap between the manual and HLS-based FPGA designs, various code optimization forms are made available in today’s HLS tools. This paper proposes a HLS source code and directive manipulation strategy for real-time image processing by taking into account the applying order of different optimization forms. Experiment results demonstrate that our approach can improve more effectively the test implementations comparing to the other optimization strategies.  相似文献   
87.
A profit and a demand are associated with each edge of a set of profitable edges of a given graph. A travel time is associated with each edge of the graph. A fleet of capacitated vehicles is given to serve the profitable edges. A maximum duration of the route of each vehicle is also given. The profit of an edge can be collected by one vehicle only that also serves the demand of the edge. The objective of this problem, which is called the undirected capacitated arc routing problem with profits (UCARPP), is to find a set of routes that satisfy the constraints on the duration of the route and on the capacity of the vehicle and maximize the total collected profit. We propose a branch-and-price algorithm and several heuristics. We can solve exactly instances with up to 97 profitable edges. The best heuristics find the optimal solution on most of instances where it is available.  相似文献   
88.
Owing to the dynamic nature of collaborative environments, the software intended to support collaborative work should adapt itself to the different situations that may occur. This requirement is related to the concept of “context of use”, which has been considered as an important aspect in the design of interactive systems. Nevertheless, two main problems about this concept have been identified by current research in context-aware computing: (1) most of the studies have mainly focused on the context of a single user, so the context of multiple users involved in a common endeavor remains little explored, and (2) adaptability in context-aware systems generally takes into account a reduced number of contextual variables (mainly the user’s location and platform). In this paper, we firstly re-conceptualize the notion of “context of use”, in order to consider the main characteristics of collaborative environments. Based on this new notion, we then design and implement a framework that allows application developers to specify the adaptability of groupware systems in terms of the state of activities, roles, collaborators’ location, available resources, and other typical variables of working groups. This framework has been generalized from scenarios that highlight dynamic situations presented in real collaborative settings. Finally, we validate our proposal by a set of applications that are able to adapt their user interface and functionality, when significant changes are produced in the environment, the working group, and/or the used devices.  相似文献   
89.
This paper is a general overview of the S project, run at Blaise Pascal University between 1996 and 2002. The main goal of the S project was to demonstrate the applicability of skeleton-based parallel programming techniques to the fast prototyping of reactive vision applications. This project has produced several versions of a full-fledged integrated parallel programming environment (PPE). These PPEs have been used to implement realistic vision applications, such as road following or vehicle tracking for assisted driving, on embedded parallel platforms embarked on semi-autonomous vehicles. All versions of S share a common front-end and repertoire of skeletons––presented in previous papers––but differ in the techniques used for implementing skeletons. This paper focuses on these implementation issues, by making a comparative survey, according to a set of four criteria (efficiency, expressivity, portability, predictability), of these implementation techniques. It also gives an account of the lessons we have learned, both when dealing with these implementation issues and when using the resulting tools for prototyping vision applications.  相似文献   
90.
This work presents a straightforward approach aimed at modeling the dynamic I–V characteristics of microwave active solid‐state devices. The drain‐source current generator represents the most significant source of nonlinearity in a transistor and, therefore, its correct modeling is fundamental to predict accurately the current and voltage waveforms under large‐signal operation. The proposed approach relies on using a small set of low‐frequency time‐domain waveform measurements combined with numerical optimization‐based estimation of the nonlinear model parameters. The procedure is applied to a gallium nitride HEMT and silicon FinFET. The effectiveness of the modeling procedure in terms of prediction accuracy and generalization capability is demonstrated by validation of the extracted models under operating conditions different than the ones used for the parameters estimation. Good agreement between measurements and model simulations is achieved for both technologies and in both low‐ and high‐frequency range. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:109–116, 2014.  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