全文获取类型
收费全文 | 5399篇 |
免费 | 365篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 66篇 |
综合类 | 7篇 |
化学工业 | 1641篇 |
金属工艺 | 60篇 |
机械仪表 | 105篇 |
建筑科学 | 216篇 |
矿业工程 | 11篇 |
能源动力 | 204篇 |
轻工业 | 699篇 |
水利工程 | 45篇 |
石油天然气 | 7篇 |
无线电 | 348篇 |
一般工业技术 | 1015篇 |
冶金工业 | 378篇 |
原子能技术 | 29篇 |
自动化技术 | 938篇 |
出版年
2024年 | 16篇 |
2023年 | 98篇 |
2022年 | 326篇 |
2021年 | 399篇 |
2020年 | 184篇 |
2019年 | 188篇 |
2018年 | 219篇 |
2017年 | 191篇 |
2016年 | 266篇 |
2015年 | 194篇 |
2014年 | 285篇 |
2013年 | 362篇 |
2012年 | 354篇 |
2011年 | 457篇 |
2010年 | 295篇 |
2009年 | 254篇 |
2008年 | 301篇 |
2007年 | 244篇 |
2006年 | 168篇 |
2005年 | 152篇 |
2004年 | 129篇 |
2003年 | 119篇 |
2002年 | 85篇 |
2001年 | 61篇 |
2000年 | 47篇 |
1999年 | 50篇 |
1998年 | 41篇 |
1997年 | 32篇 |
1996年 | 41篇 |
1995年 | 24篇 |
1994年 | 21篇 |
1993年 | 22篇 |
1992年 | 25篇 |
1991年 | 14篇 |
1990年 | 7篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1979年 | 8篇 |
1977年 | 2篇 |
1969年 | 1篇 |
1967年 | 2篇 |
1948年 | 1篇 |
排序方式: 共有5769条查询结果,搜索用时 15 毫秒
61.
Alessandro Agnetis Enrico Grande Pitu B. Mirchandani Andrea Pacifici 《Computers & Operations Research》2009
The paper addresses the problem of locating sensors with a circular field of view so that a given line segment is under full surveillance, which is termed as the disc covering problem on a line. The cost of each sensor includes a fixed component f, and a variable component that is a convex function of the diameter of the field-of-view area. When only one type of sensor or, in general, one type of disc, is available, then a simple polynomial algorithm solves the problem. When there are different types of sensors, the problem becomes hard. A branch-and-bound algorithm as well as an efficient heuristic are developed for the special case in which the variable cost component of each sensor is proportional to the square of the measure of the field-of-view area. The heuristic very often obtains the optimal solution as shown in extensive computational testing. 相似文献
62.
63.
64.
This paper provides an overview of the current state-of-the-art on using constraints in knowledge discovery and data mining. The use of constraints in a data mining task requires specific definition and satisfaction tools during knowledge extraction. This survey proposes three groups of studies based on classification, clustering and pattern mining, whether the constraints are on the data, the models or the measures, respectively. We consider the distinctions between hard and soft constraint satisfaction, and between the knowledge extraction phases where constraints are considered. In addition to discussing how constraints can be used in data mining, we show how constraint-based languages can be used throughout the data mining process. 相似文献
65.
This work describes a system for acoustic‐based navigation that relies on the addition of localization services to underwater networks. The localization capability has been added on top of an existing network, without imposing constraints on its structure/operation. The approach is based on the inclusion of timing information within acoustic messages through which it is possible to know the time of an acoustic transmission in relation to its reception. Exploiting such information at the network application level makes it possible to create an interrogation scheme similar to that of a long baseline. The advantage is that the nodes/autonomous underwater vehicles (AUVs) themselves become the transponders of a network baseline, and hence there is no need for dedicated instrumentation. The paper reports at sea results obtained from the COLLAB–NGAS14 experimental campaign. During the sea trial, the approach was implemented within an operational network in different configurations to support the navigation of the two Centre for Maritime Research and Experimentation Ocean Explorer (CMRE OEX) vehicles. The obtained results demonstrate that it is possible to support AUV navigation without constraining the network design and with a minimum communication overhead. Alternative solutions (e.g., synchronized clocks or two‐way‐travel‐time interrogations) might provide higher precision or accuracy, but they come at the cost of impacting on the network design and/or on the interrogation strategies. Results are discussed, and the performance achieved at sea demonstrates the viability to use the system in real, large‐scale operations involving multiple AUVs. These results represent a step toward location‐aware underwater networks that are able to provide node localization as a service. 相似文献
66.
The aim of this paper is to deal with the problem of fault tolerant control in the framework of discrete event systems modeled as automata. A fault tolerant controller is a controller able to satisfy control specifications both in nominal operation and after the occurrence of a fault. This task is solved by means of a parameterized controller that is suitably updated on the basis of the information provided by online diagnostics: the supervisor actively reacts to the detection of a malfunctioning component in order to eventually meet degraded control specifications. Starting from an appropriate model of the system, we recall the notion of safe diagnosability as a necessary step in order to achieve fault tolerant control. We then introduce two new notions: (i) “safe controllability”, which represents the capability, after the occurrence of a fault, of steering the system away from forbidden zones and (ii) “active fault tolerant system”, which is the property of safely continuing operation after faults. Finally, we show how the problem can be solved using a general control architecture based on the use of special kind of diagnoser, called “diagnosing controller”, which is used to safely detect faults and to switch between the nominal control policy and a bank of reconfigured control policies. A simple example is used to illustrate the new notions and the control architecture introduced in the paper. 相似文献
67.
Bettina Fazzinga Sergio Flesca Andrea Tagarelli 《Knowledge and Information Systems》2011,26(1):127-173
An effective solution to automate information extraction from Web pages is represented by wrappers. A wrapper associates a Web page with an XML document that represents part of the information in that page in a machine-readable
format. Most existing wrapping approaches have traditionally focused on how to generate extraction rules, while they have
ignored potential benefits deriving from the use of the schema of the information being extracted in the wrapper evaluation. In this paper, we investigate how the schema of extracted information
can be effectively used in both the design and evaluation of a Web wrapper. We define a clean declarative semantics for schema-based wrappers by introducing the notion of (preferred) extraction model, which is essential to compute a valid XML document containing
the information extracted from a Web page. We developed the SCRAP (SChema-based wRAPper for web data) system for the proposed schema-based wrapping approach, which also provides visual support tools to the wrapper designer.
Moreover, we present a wrapper generalization framework to profitably speed up the design of schema-based wrappers. Experimental
evaluation has shown that SCRAP wrappers are not only able to successfully extract the required data, but also they are robust
to changes that may occur in the source Web pages. 相似文献
68.
Jan Birnstock Tobias Canzler Michael Hofmann Andrea Lux Sven Murano Philipp Wellmann Ansgar Werner 《Journal of the Society for Information Display》2008,16(2):221-229
Abstract— Currently, three issues are identified that decide upon the commercial success of organic light‐emitting diodes (OLEDs), both in display and lighting applications: power efficiency, lifetime, and price competitiveness. PIN OLEDs are widely seen as the preferred way to maximize power efficiency. Here, it is reported that this concept also delivers the world longest lifetimes. For a highly efficient deep‐red PIN OLED, a half‐lifetime of 25,000 hours for a starting brightness of 10,000 cd/m2 and a minimal voltage increase over lifetime is reported. This value corresponds to more than 1 × 106 hours at 1000 cd/m2 using an exponent of n = 1.7, which was measured by driving the OLEDs at different starting luminances. Because there is no initial luminance drop, these PIN OLEDs also exhibit a very high 80% lifetime (>300,000 hours at 1000 cd/m2). New record lifetime values for blue and green will be reported as well. Additionally, further topics that have impact on the production yield and cost such as the newly developed air‐stable organic n‐doping material NDN‐26 and top‐emitting structures will be discussed. 相似文献
69.
Interfacing human and computer with wireless body area sensor networks: the WiMoCA solution 总被引:1,自引:0,他引:1
Elisabetta Farella Augusto Pieracci Luca Benini Laura Rocchi Andrea Acquaviva 《Multimedia Tools and Applications》2008,38(3):337-363
Wireless Body Area Sensor Networks (WBASN) are an emerging technology enabling the design of natural human–computer interfaces
(HCI). Automatic recognition of human motion, gestures, and activities is studied in several contexts. For example, mobile
computing technology is being considered as a replacement of traditional input systems. Moreover, body posture and activity
monitoring can be used for entertainment and health-care applications. However, until now, little work has been done to develop
flexible and efficient WBASN solutions suitable for a wide range of applications. Their requirements pose new challenges for
sensor network designs, such as optimizing traditional solutions for use as environmental monitoring-like applications and
developing on-the-field stress tests. In this paper, we demonstrate the flexibility of a custom-designed WBASN called WiMoCA
with respect to a wide range of posture and activity recognition applications by means of practical implementation and on-the-field
testing. Nodes of the network mounted on different parts of the human body exploit tri-axial accelerometers to detect its
movements. The advanced digital Micro-electro-mechanical system (MEMS) based inertial sensor has been chosen for WiMoCA because
it demonstrated high flexibility of use in many different situations, providing the chance to exploit both static and dynamic
acceleration components for different purposes. Furthermore, the sensibility and accuracy of the sensing element is perfectly
adequate for monitoring human movement, while keeping cost low and size compact, thus meeting our requirements. We implemented
three types of applications, stressing the WBASN in many aspects. In fact, they are characterized by different requirements
in terms of accuracy, timeliness, and computation distributed on sensing nodes. For each application, we describe its implementation,
and we discuss results about performance and power consumption.
相似文献
Andrea AcquavivaEmail: |
70.
We study the complexity of routing a set of messages with multiple destinations (multicast routing) on an n-node square mesh under the store-and-forward model. A standard argument proves that
time is required to route n messages, where each message is generated by a distinct node and at most c messages are to be delivered to any individual node. The obvious approach of simply replicating each message into the appropriate
number of unicast (single-destination) messages and routing these independently does not yield an optimal algorithm. We provide
both randomized and deterministic algorithms for multicast routing, which use constant-size buffers at each node. The randomized
algorithm attains optimal performance, while the deterministic algorithm is slower by a factor of O( log 2
n). We also describe an optimal deterministic algorithm that, however, requires large buffers of size O(c).
A preliminary version of this paper appeared in Proceedings of the 13th Annual ACM Symposium on Parallel Algorithms and Architectures,
Crete, Greece, 2001. This work was supported, in part, by MIUR under project ALGO-NEXT. 相似文献