全文获取类型
收费全文 | 2836篇 |
免费 | 271篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 29篇 |
综合类 | 1篇 |
化学工业 | 704篇 |
金属工艺 | 49篇 |
机械仪表 | 115篇 |
建筑科学 | 89篇 |
矿业工程 | 7篇 |
能源动力 | 100篇 |
轻工业 | 651篇 |
水利工程 | 27篇 |
石油天然气 | 13篇 |
无线电 | 150篇 |
一般工业技术 | 466篇 |
冶金工业 | 70篇 |
原子能技术 | 26篇 |
自动化技术 | 611篇 |
出版年
2024年 | 14篇 |
2023年 | 45篇 |
2022年 | 101篇 |
2021年 | 185篇 |
2020年 | 122篇 |
2019年 | 146篇 |
2018年 | 152篇 |
2017年 | 148篇 |
2016年 | 149篇 |
2015年 | 124篇 |
2014年 | 177篇 |
2013年 | 359篇 |
2012年 | 233篇 |
2011年 | 226篇 |
2010年 | 171篇 |
2009年 | 155篇 |
2008年 | 116篇 |
2007年 | 88篇 |
2006年 | 72篇 |
2005年 | 44篇 |
2004年 | 42篇 |
2003年 | 45篇 |
2002年 | 37篇 |
2001年 | 15篇 |
2000年 | 15篇 |
1999年 | 14篇 |
1998年 | 23篇 |
1997年 | 14篇 |
1996年 | 7篇 |
1995年 | 10篇 |
1994年 | 7篇 |
1993年 | 14篇 |
1992年 | 3篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1983年 | 2篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1965年 | 2篇 |
1964年 | 1篇 |
1963年 | 2篇 |
1938年 | 2篇 |
排序方式: 共有3108条查询结果,搜索用时 15 毫秒
61.
Effects of heating in air and chlorine atmosphere on the crystalline structure of pure Ta2O5 or mixed with carbon 总被引:1,自引:0,他引:1
J. GonzÁLEZ M. Del C. Ruiz J. B. Rivarola D. Pasquevich 《Journal of Materials Science》1998,33(16):4173-4180
Structure changes undergone by pure amorphous hydrated tantalum oxide mixed with different types of carbon when heated in air or chlorine atmospheres were monitored by X-ray diffraction (XRD) and scanning electronic microscopy (SEM). Heating in air of pure Ta2O5 causes the appearance of the hexagonal structure -Ta2O5 at 973 K and the ortho-rhombic structure -Ta2O5 at 1173 K. Heating in chlorine atmosphere markedly lowers the temperature at which transformation to the orthorhombic phase occurs. This effect is attributed to recrystallization of tantalum oxide from tantalum chloride and oxygen, both in gaseous phase, formed in a previous chlorination step of the amorphous oxide. When the thermal treatment is performed in chlorine atmosphere the presence of carbon permits the detection of the hexagonal form at 753 K; this temperature varies with the type of carbon and the oxide : carbon ration. © 1998 Kluwer Academic Publishers 相似文献
62.
63.
64.
Soledad Escolar Díaz Florin Isaila Alejandro Calderón Mateos Luis Miguel Sanchez García David E. Singh 《The Journal of supercomputing》2010,51(1):76-93
In the last years the Wireless Sensor Networks’ (WSN) technology has been increasingly employed in various application domains.
The extensive use of WSN posed new challenges in terms of both scalability and reliability. This paper proposes Sensor Node
File System (SENFIS), a novel file system for sensor nodes, which addresses both scalability and reliability concerns. SENFIS
can be mainly used in two broad scenarios. First, it can transparently be employed as a permanent storage for distributed
TinyDB queries, in order to increase the reliability and scalability. Second, it can be directly used by a WSN application
for permanent storage of data on the WSN nodes. The experimental section shows that SENFIS implementation makes an efficient
use of resources in terms of energy consumption, memory footprint, flash wear levelling, while achieving execution times similarly
with existing WSN file systems. 相似文献
65.
J. Jesús Cervantes-Sánchez José M. Rico-Martínez Alejandro Tadeo-ChávezGerardo I. Pérez-Soto 《Robotics and Computer》2011
It is presented an integral approach for the kinematic design of spatial, hybrid closed chains which include planar parallelograms into their kinematic structure. It is based on a systematic application of recursive formulae intended for describing the evolution of screws through time. Due to the particular nature of the proposed approach, it can be closely related with Lie algebras and allows to overcome the lacking of group structure offered by a parallelogram when it is going to be considered as a component of a hybrid closed chain. Several application examples are presented in order to show the potential of the proposed approach. 相似文献
66.
Rafael Marín-LópezAuthor Vitae Fernando Pereñíguez Author VitaeGabriel López Author Vitae Alejandro Pérez-Méndez Author Vitae 《Computer Standards & Interfaces》2011,33(5):494-504
Kerberos is a well-known standard protocol which is becoming one of the most widely deployed for authentication and key distribution in application services. However, whereas service providers use the protocol to control their own subscribers, they do not widely deploy Kerberos infrastructures to handle subscribers coming from foreign domains, as happens in network federations. Instead, the deployment of Authentication, Authorization and Accounting (AAA) infrastructures has been preferred for that operation. Thus, the lack of a correct integration between these infrastructures and Kerberos limits the service access only to service provider's subscribers. To avoid this limitation, we design an architecture which integrates a Kerberos pre-authentication mechanism, based on the use of the Extensible Authentication Protocol (EAP), and advanced authorization, based on the standards SAML and XACML, to link the end user authentication and authorization performed through an AAA infrastructure with the delivery of Kerberos tickets in the service provider's domain. We detail the interfaces, protocols, operation and extensions required for our solution. Moreover, we discuss important aspects such as the implications on existing standards. 相似文献
67.
A technique that provides closed loop integral action depending on the passive outputs of port-controlled Hamiltonian systems is already available. This paper addresses a new method that allows us to add integral action also on system variables having relative degree higher than one, while still preserving the Hamiltonian form and, thus, closed loop stability. The new approach is applied to design speed regulation controllers for the permanent magnet synchronous motor. Closed loop stability and asymptotic rejection of unknown piecewise constant load torques are formally proved. This theoretically predicted control system performance is illustrated via simulation experiments, which also show that the properties hold under parameter uncertainties. This is in line with the usual practice of including integral action in a controller with the aim of improving its closed loop robustness. The fact that the method enhances the range of possible integral actions in the controller, enriched with this robustness property, allows us to assess it as a practically important complement to the well-known interconnection and damping assignment techniques developed in the framework of port-controlled Hamiltonian systems. 相似文献
68.
This paper presents a new approach to Particle Swarm Optimization, called Michigan Approach PSO (MPSO), and its application
to continuous classification problems as a Nearest Prototype (NP) classifier. In Nearest Prototype classifiers, a collection
of prototypes has to be found that accurately represents the input patterns. The classifier then assigns classes based on
the nearest prototype in this collection. The MPSO algorithm is used to process training data to find those prototypes. In
the MPSO algorithm each particle in a swarm represents a single prototype in the solution and it uses modified movement rules
with particle competition and cooperation that ensure particle diversity. The proposed method is tested both with artificial
problems and with real benchmark problems and compared with several algorithms of the same family. Results show that the particles
are able to recognize clusters, find decision boundaries and reach stable situations that also retain adaptation potential.
The MPSO algorithm is able to improve the accuracy of 1-NN classifiers, obtains results comparable to the best among other
classifiers, and improves the accuracy reported in literature for one of the problems.
相似文献
Pedro IsasiEmail: |
69.
Joaquín Nicolás Joaquín Lasheras Ambrosio Toval Francisco J. Ortiz Bárbara Álvarez 《Requirements Engineering》2009,14(1):27-46
Teleoperated systems for ship hull maintenance (TOS) are robotic systems for ship maintenance tasks, such as cleaning or painting
a ship’s hull. The product line paradigm has recently been applied to TOS, and a TOS reference architecture has thus been
designed. However, TOS requirements specifications have not been developed in any rigorous way with reuse in mind. We therefore
believe that an opportunity exists to increase the abstraction level at which stakeholders can reason about this product line.
This paper reports an experience in which this TOS domain was analyzed, including the lessons learned in the construction
and use of the TOS domain model. The experience is based on the application of extensions of well-known domain analysis techniques,
together with the use of quality attribute templates traced to a feature model to deal with non-functional issues. A qualitative
research method (action research) was used to carry out the experience. 相似文献
70.
In this paper, the performance and durability of hybrid PEM fuel cell vehicles are investigated. To that end, a hybrid predictive controller is proposed to improve battery performance and to avoid fuel cell and battery degradation. Such controller deals with this complex control problem by handling binary and continuous variables, piecewise affine models and constraints. Moreover, the control strategy is to track motor power demand and keep batteries close to a desired battery state of charge which is appropriately chosen to minimize hydrogen consumption. It is important to highlight the consideration of constraints which are directly related to the goals of this paper, such as minimum fuel cell power threshold and time limitation between fuel cell startups and shutdowns. Furthermore, different models have been elaborated and particularized for a vehicle prototype. These models include few innovations such as a reference governor which smooths fuel cell power demand during sharp power profiles, forcing batteries to supply such peaks and resulting a longer fuel cell lifetime. Battery thermal dynamics are also taken into account in these models in order to analyze the effect of battery temperature on its degradation. Finally, this paper studies the feasibility of the real implementation, presenting an explicit formulation as a solution to reduce execution time. This explicit controller exhibits the same performance as the hybrid predictive controller does with a reduced computational effort. All the results have been validated in several simulations. 相似文献