全文获取类型
收费全文 | 3798篇 |
免费 | 80篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 40篇 |
综合类 | 4篇 |
化学工业 | 832篇 |
金属工艺 | 89篇 |
机械仪表 | 81篇 |
建筑科学 | 153篇 |
矿业工程 | 11篇 |
能源动力 | 88篇 |
轻工业 | 305篇 |
水利工程 | 27篇 |
石油天然气 | 12篇 |
武器工业 | 2篇 |
无线电 | 344篇 |
一般工业技术 | 598篇 |
冶金工业 | 670篇 |
原子能技术 | 41篇 |
自动化技术 | 584篇 |
出版年
2021年 | 40篇 |
2020年 | 32篇 |
2019年 | 38篇 |
2018年 | 63篇 |
2017年 | 46篇 |
2016年 | 56篇 |
2015年 | 45篇 |
2014年 | 98篇 |
2013年 | 217篇 |
2012年 | 133篇 |
2011年 | 187篇 |
2010年 | 120篇 |
2009年 | 133篇 |
2008年 | 178篇 |
2007年 | 141篇 |
2006年 | 140篇 |
2005年 | 131篇 |
2004年 | 104篇 |
2003年 | 96篇 |
2002年 | 105篇 |
2001年 | 64篇 |
2000年 | 71篇 |
1999年 | 67篇 |
1998年 | 157篇 |
1997年 | 94篇 |
1996年 | 83篇 |
1995年 | 67篇 |
1994年 | 50篇 |
1993年 | 63篇 |
1992年 | 39篇 |
1991年 | 51篇 |
1990年 | 45篇 |
1989年 | 37篇 |
1988年 | 39篇 |
1987年 | 41篇 |
1986年 | 62篇 |
1985年 | 51篇 |
1984年 | 46篇 |
1983年 | 46篇 |
1982年 | 40篇 |
1981年 | 52篇 |
1980年 | 43篇 |
1979年 | 42篇 |
1978年 | 39篇 |
1977年 | 43篇 |
1976年 | 38篇 |
1975年 | 34篇 |
1973年 | 24篇 |
1972年 | 24篇 |
1971年 | 24篇 |
排序方式: 共有3881条查询结果,搜索用时 15 毫秒
91.
Abstract: Enterprise production is becoming more and more knowledge oriented nowadays and knowledge management is playing a key role in making commercial profit and maintaining enterprise competence. Knowledge characterization and measurement are the bases of knowledge management, and this paper aims to develop a method for characterizing and measuring knowledge in a comprehensive and practical way. Knowledge in its static state is modelled as a vector, whose values vary with the situation, and changes in state are modelled as a finite state machine. 相似文献
92.
Understanding argumentation and its role in human reasoning has been a continuous subject of investigation for scholars from
the ancient Greek philosophers to current researchers in philosophy, logic and artificial intelligence. In recent years, argumentation
models have been used in different areas such as knowledge representation, explanation, proof elaboration, commonsense reasoning,
logic programming, legal reasoning, decision making, and negotiation. However, these models address quite specific needs and
there is need for a conceptual framework that would organize and compare existing argumentation-based models and methods.
Such a framework would be very useful especially for researchers and practitioners who want to select appropriate argumentation
models or techniques to be incorporated in new software systems with argumentation capabilities. In this paper, we propose
such a conceptual framework, based on taxonomy of the most important argumentation models, approaches and systems found in
the literature. This framework highlights the similarities and differences between these argumentation models. As an illustration
of the practical use of this framework, we present a case study which shows how we used this framework to select and enrich
an argumentation model in a knowledge acquisition project which aimed at representing argumentative knowledge contained in
texts critiquing military courses of action. 相似文献
93.
A real time control strategy for fuel cell hybrid vehicles is proposed. The objective is to reduce the hydrogen consumption by using an efficient power sharing strategy between the fuel cell system (FCS) and the energy buffer (EB). The energy buffer (battery or supercapacitor) is charge-sustained (no plug-in capabilities). The real time control strategy is derived from a non-causal optimization algorithm based on optimal control theory. The strategy is validated experimentally with a hardware-in-the-loop (HiL) test bench based on a 600 W fuel cell system. 相似文献
94.
Jürgen Bernard Jan Brase Dieter Fellner Oliver Koepler Jörn Kohlhammer Tobias Ruppert Tobias Schreck Irina Sens 《International Journal on Digital Libraries》2010,11(2):111-123
Digital Library support for textual and certain types of non-textual documents has significantly advanced over the last years.
While Digital Library support implies many aspects along the whole library workflow model, interactive and visual retrieval
allowing effective query formulation and result presentation are important functions. Recently, new kinds of non-textual documents
which merit Digital Library support, but yet cannot be fully accommodated by existing Digital Library technology, have come
into focus. Scientific data, as produced for example, by scientific experimentation, simulation or observation, is such a
document type. In this article we report on a concept and first implementation of Digital Library functionality for supporting
visual retrieval and exploration in a specific important class of scientific primary data, namely, time-oriented research
data. The approach is developed in an interdisciplinary effort by experts from the library, natural sciences, and visual analytics
communities. In addition to presenting the concept and to discussing relevant challenges, we present results from a first
implementation of our approach as applied on a real-world scientific primary data set. We also report from initial user feedback
obtained during discussions with domain experts from the earth observation sciences, indicating the usefulness of our approach. 相似文献
95.
Florent Peres Bernard Berthomieu François Vernadat 《Discrete Event Dynamic Systems》2011,21(3):395-424
Complex systems are often designed and built from smaller pieces, called components. Components are open sub-systems meant
to be combined (or composed) to form other components or closed systems. It is well known that Petri nets allow such a component
based modeling, relying on parallel composition and transition synchronization. However, synchronizing transitions that carry
temporal constraints does not yield a compositional method for assembling components, a highly desirable property. The paper
addresses this particular problem: how to build complex systems in a compositional manner from components specified by Time
Petri nets (TPN). A first solution is proposed, adequate for a particular subclass of Time Petri nets but significantly increasing the complexity
of components. Then an improved solution is developed, relying on an extension of Time Petri nets with two relations added
on transitions. This latter solution requires a much simpler transformation of nets, does not significantly increase their
complexity, and is applicable to a larger class of TPN. 相似文献
96.
We construct strict Lyapunov functions for broad classes of nonlinear systems satisfying Matrosov type conditions. Our new constructions are simpler than the designs available in the literature. We illustrate the practical interest of our designs using a globally asymptotically stable biological model. 相似文献
97.
Marttinen Pekka Tang Jing De Baets Bernard Dawyndt Peter Corander Jukka 《IEEE transactions on pattern analysis and machine intelligence》2009,31(1):74-85
Bayesian model-based classifiers, both unsupervised and supervised, have been studied extensively and their value and versatility have been demonstrated on a wide spectrum of applications within science and engineering. A majority of the classifiers are built on the assumption of intrinsic discreteness of the considered data features or on the discretization of them prior to the modeling. On the other hand, Gaussian mixture classifiers have also been utilized to a large extent for continuous features in the Bayesian framework. Often the primary reason for discretization in the classification context is the simplification of the analytical and numerical properties of the models. However, the discretization can be problematic due to its textit{ad hoc} nature and the decreased statistical power to detect the correct classes in the resulting procedure. We introduce an unsupervised classification approach for fuzzy feature vectors that utilizes a discrete model structure while preserving the continuous characteristics of data. This is achieved by replacing the ordinary likelihood by a binomial quasi-likelihood to yield an analytical expression for the posterior probability of a given clustering solution. The resulting model can be justified from an information-theoretic perspective. Our method is shown to yield highly accurate clusterings for challenging synthetic and empirical data sets. 相似文献
98.
This paper proposes a new representation of multibody mechanical systems involving three-dimensional frictional unilateral constraints. The new representation is of the form of a differential algebraic inclusion (DAI) employing a normal cone with a non-Euclidean, singular norm metric. It can be seen as a generalization of a differential algebraic equation (DAE) using Lagrange multipliers, which has been used to represent mechanical systems with equality constraints. The paper also presents an approach to approximate the aforementioned DAI by another form of DAI, which can be equivalently converted into an ordinary differential equation (ODE). The approach can be seen as a generalization of the Baumgarte stabilization, which was originally developed for DAEs. The new DAI representation and its ODE approximation are illustrated with some simple examples. 相似文献
99.
It is shown that, for any time-invariant exponentially stable linear system with additive disturbances, time-varying exponentially stable interval observers can be constructed. The technique of construction relies on the Jordan canonical form that any real matrix admits and on time-varying changes of coordinates for elementary Jordan blocks which lead to cooperative linear systems. The approach is applied to detectable linear systems. 相似文献
100.
In domains like decision theory and social choice theory it is known for a long time that stochastic transitivity properties yield necessary and sufficient conditions for the ranking or utility representability of reciprocal preference relations. In this article we extend these results for reciprocal preference relations originating from the pairwise comparison of random vectors in a machine learning context. More specifically, the expected ranking accuracy (ERA) is such a reciprocal relation that occurs in multi-class classification problems, when ranking or utility functions are fitted to the data in a pairwise manner. We establish necessary and sufficient conditions for which these pairwise bipartite ranking functions can be simplified to a single ranking function such that the pairwise expected ranking accuracies of both models coincide. Similarly as for more common reciprocal preference relations, cycle transitivity plays a crucial role in this new setting. We first consider the finite sample case, for which expected ranking accuracy can be estimated by means of the area under the ROC curve (AUC), and subsequently, we further generalize these results to the underlying distributions. It turns out that the ranking representability of pairwisely compared random vectors can be expressed elegantly in a distribution-independent way by means of a specific type of cycle transitivity, defined by a conjunctor that is closely related to the algebraic product. 相似文献