全文获取类型
收费全文 | 2453篇 |
免费 | 87篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 9篇 |
综合类 | 9篇 |
化学工业 | 531篇 |
金属工艺 | 36篇 |
机械仪表 | 43篇 |
建筑科学 | 180篇 |
矿业工程 | 16篇 |
能源动力 | 74篇 |
轻工业 | 264篇 |
水利工程 | 29篇 |
石油天然气 | 11篇 |
无线电 | 141篇 |
一般工业技术 | 450篇 |
冶金工业 | 309篇 |
原子能技术 | 12篇 |
自动化技术 | 431篇 |
出版年
2023年 | 11篇 |
2022年 | 21篇 |
2021年 | 45篇 |
2020年 | 41篇 |
2019年 | 37篇 |
2018年 | 54篇 |
2017年 | 46篇 |
2016年 | 43篇 |
2015年 | 57篇 |
2014年 | 76篇 |
2013年 | 174篇 |
2012年 | 101篇 |
2011年 | 166篇 |
2010年 | 107篇 |
2009年 | 113篇 |
2008年 | 124篇 |
2007年 | 129篇 |
2006年 | 94篇 |
2005年 | 89篇 |
2004年 | 72篇 |
2003年 | 70篇 |
2002年 | 69篇 |
2001年 | 41篇 |
2000年 | 50篇 |
1999年 | 35篇 |
1998年 | 72篇 |
1997年 | 43篇 |
1996年 | 36篇 |
1995年 | 36篇 |
1994年 | 44篇 |
1993年 | 30篇 |
1992年 | 29篇 |
1991年 | 19篇 |
1990年 | 22篇 |
1989年 | 17篇 |
1988年 | 22篇 |
1987年 | 15篇 |
1986年 | 19篇 |
1985年 | 34篇 |
1984年 | 25篇 |
1983年 | 20篇 |
1982年 | 21篇 |
1981年 | 17篇 |
1980年 | 18篇 |
1979年 | 24篇 |
1978年 | 14篇 |
1977年 | 21篇 |
1976年 | 23篇 |
1975年 | 19篇 |
1973年 | 10篇 |
排序方式: 共有2545条查询结果,搜索用时 0 毫秒
31.
Strategic alignment between an organization's business strategy/capabilities and those of its information technology (IT) unit is an extensively researched subject that addresses the issue of fit between business and technology strategies. A key gap in the literature is lack of recognition that underlying this macro level of alignment are other, more granular levels of alignment involving the interdependent subunits within the corporate IT unit. Given the critical interdependencies between development and testing subunits in software engineering, this paper focuses on an alignment model for ensuring that these two functions work together effectively. A development-testing alignment (DTA) model is described, and a case study investigating its value and application is presented. This DTA is decomposed into distinct components for the purposes of theoretical clarity and pragmatic application. The case study analysis uses the model to understand and interpret development-testing alignment in a Fortune 500 company. We found that the development and testing functions were significantly misaligned, and our model identified close to twenty specific aspects that needed to be considered to enhance alignment. These included changes in specificity of scope, governance, resource availability, competencies, and processes. Our analysis shows that the DTA model can be usefully applied for the purpose of understanding tactical alignment between subunits within a corporate IT unit. It also demonstrates that there is value in considering alignment as a dynamic, context-driven, social phenomenon as well as a useful interpretative lens for exploring organizational interactions and interdependencies. 相似文献
32.
Sangmun Shin Nguyen Khoa Viet Truong Byung Rae Cho Sung Hoon Hong 《Computers & Industrial Engineering》2011
Robust design (RD) and tolerance design (TD) have received much attention from researchers and practitioners for more than two decades, and a number of methodologies for modeling and optimizing the RD and TD processes have been studied. However, there is ample room for improvement. Because most existing research considers RD and TD as separate research fields, the primary objective of this paper is to develop a sequential robust–tolerance design method to jointly determine the best factor settings and the closed-form solutions for the optimal specification limits. We then apply the proposed method to a destructive quality characteristic. Finally, a case study and sensitivity analyses are performed for verification purposes, and further studies are discussed. 相似文献
33.
The refinement calculus is a well-established theory for formal development of imperative program code and is supported by a number of automated tools. Via a detailed case study, this article shows how refinement theory and tool support can be extended for a program with real-time constraints. The approach adapts a timed variant of the refinement calculus and makes corresponding enhancements to a theorem-prover based refinement tool. 相似文献
34.
This paper investigates the fundamental difference between a simple e-tender box and a traditional physical tender box, and
highlights a series of security traps created by the functional differences. Based on our findings, we have defined the security
requirements for an e-tender submission protocol. We also discuss functional limitations of cryptographic technologies. As
a result, two secure e-tender submission protocols are proposed which enable a secure e-tender submission. Protocols are assumed
to run under the condition that all tendering parties (principal and tenderers) are dishonest players. Our informal and formal
security analysis show that these protocols meet their security goals under well known collusion scenarios. Because security
is a process not a product, our approach will have broad industry application for developing secure electronic business processes
in areas other than e-tendering.
相似文献
Colin BoydEmail: |
35.
Towards a continuous microfluidic rheometer 总被引:1,自引:1,他引:0
Pierre Guillot Thomas Moulin Roman Kötitz Matthieu Guirardel Arash Dodge Mathieu Joanicot Annie Colin Charles-Henri Bruneau Thierry Colin 《Microfluidics and nanofluidics》2008,5(5):619-630
In a previous paper we presented a way to measure the rheological properties of complex fluids on a microfluidic chip (Guillot
et al., Langmuir 22:6438, 2006). The principle of our method is to use parallel flows between two immiscible fluids as a pressure
sensor. In fact, in a such flow, both fluids flow side by side and the size occupied by each fluid stream depends only on
both flow rates and on both viscosities. We use this property to measure the viscosity of one fluid knowing the viscosity
of the other one, both flow rates and the relative size of both streams in a cross-section. We showed that using a less viscous
fluid as a reference fluid allows to define a mean shear rate with a low standard deviation in the other fluid. This method
allows us to measure the flow curve of a fluid with less than 250 μL of fluid. In this paper we implement this principle in
a fully automated set up which controls the flow rate, analyzes the picture and calculates the mean shear rate and the viscosity
of the studied fluid. We present results obtained for Newtonian fluids and complex fluids using this set up and we compare
our data with cone and plate rheometer measurements. By adding a mixing stage in the fluidic network we show how this set
up can be used to characterize in a continuous way the evolution of the rheological properties as a function of the formulation
composition. We illustrate this by measuring the rheological curve of four formulations of polyethylene oxide solution with
only 1.3 mL of concentrated polyethylene oxide solution. This method could be very useful in screening processes where the
viscosity range and the behavior of the fluid to an applied stress must be evaluated. 相似文献
36.
Whereas there is a number of methods and algorithms to learn regular languages, moving up the Chomsky hierarchy is proving
to be a challenging task. Indeed, several theoretical barriers make the class of context-free languages hard to learn. To
tackle these barriers, we choose to change the way we represent these languages. Among the formalisms that allow the definition
of classes of languages, the one of string-rewriting systems (SRS) has outstanding properties. We introduce a new type of
SRS’s, called Delimited SRS (DSRS), that are expressive enough to define, in a uniform way, a noteworthy and non trivial class
of languages that contains all the regular languages,
,
, the parenthesis languages of Dyck, the language of Lukasiewicz, and many others. Moreover, DSRS’s constitute an efficient
(often linear) parsing device for strings, and are thus promising candidates in forthcoming applications of grammatical inference.
In this paper, we pioneer the problem of their learnability. We propose a novel and sound algorithm (called LARS) which identifies a large subclass of them in polynomial time (but not data). We illustrate the execution of our algorithm
through several examples, discuss the position of the class in the Chomsky hierarchy and finally raise some open questions
and research directions.
This work was supported in part by the IST Program of the European Community, under the PASCAL Network of Excellence, IST-2002-506778. This publication only reflects the authors’ views.
Editor: Georgios Paliouras and Yasubumi Sakakibara 相似文献
37.
This letter aims at studying the impact of iterative Hebbian learning algorithms on the recurrent neural network's underlying dynamics. First, an iterative supervised learning algorithm is discussed. An essential improvement of this algorithm consists of indexing the attractor information items by means of external stimuli rather than by using only initial conditions, as Hopfield originally proposed. Modifying the stimuli mainly results in a change of the entire internal dynamics, leading to an enlargement of the set of attractors and potential memory bags. The impact of the learning on the network's dynamics is the following: the more information to be stored as limit cycle attractors of the neural network, the more chaos prevails as the background dynamical regime of the network. In fact, the background chaos spreads widely and adopts a very unstructured shape similar to white noise. Next, we introduce a new form of supervised learning that is more plausible from a biological point of view: the network has to learn to react to an external stimulus by cycling through a sequence that is no longer specified a priori. Based on its spontaneous dynamics, the network decides "on its own" the dynamical patterns to be associated with the stimuli. Compared with classical supervised learning, huge enhancements in storing capacity and computational cost have been observed. Moreover, this new form of supervised learning, by being more "respectful" of the network intrinsic dynamics, maintains much more structure in the obtained chaos. It is still possible to observe the traces of the learned attractors in the chaotic regime. This complex but still very informative regime is referred to as "frustrated chaos." 相似文献
38.
Marie-Laure Betbeder Philippe Cottier Colin Schmidt Pierre Tchounikine 《AI & Society》2006,20(3):314-330
In this article, we present research in the making of a collective work environment within the framework of a distance education course. We base our theoretical and methodological standpoints on examples of dialogical discourses recorded within the framework of this CSCL system called Symba. In fact, the results of previous research lead us to rethink our vision of the study of collaborative moments between participants in a computer-supported human learning environment that proposes several communication tools. Redefining the methodological process aiming at finding and understanding these rich learning moments is also necessary. We intend to describe “socio-technical” instances during which these collaboration phases appear. More generally speaking, our aim is to draw up both new theoretical and methodological perspectives that would be reusable in CSCL environments; in view of the nature of these two perspectives, and the diversity of the domain knowledge (sociology, cognitivism, linguistics, philosophy, statistics, etc.) brought to bear in the study of the environment in question, our approach constitutes a trans-disciplinary reassessment of the uses of the communication tools—and the study thereof—proposed.
相似文献
Marie-Laure BetbederEmail: |
39.
Indicating that CBMC does not satisfy the monotonic property in terms of the number of interactions, Xu and Zhou proposed an augmented definition of CBMC by adopting cut set instead of glue methods. The augmented CBMC clearly satisfies the monotonic property. However, CBMC is designed to overcome the problem with respect to the number of interactions and, therefore, focuses on the interaction pattern, especially, member connectivity. Consequently, it does not make sense to mention the monotonic property of CBMC with respect to interaction number. Moreover, the notion of glue methods allows several interpretations on the design quality of a class. However, that meaningful interpretation is not possible for the augmented definition due to the removal of the notion of glue methods. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
40.
Content analyses of research published in the 1982 volumes of the Journal of Personality and Social Psychology indicate that social psychologists have largely failed to study subjects drawn from meaningfully defined social groups, to consider social structural variables, to study genuine social interaction, to observe social influences on psychological functioning, or to ask Ss about social issues. It is maintained that with few exceptions, personality researchers have failed to study groups other than college students, to use biographical materials or personal documents, to devise appropriate experimental treatments, to study persons over time, or even to retain the individual as a unit of analysis. Currently, the 2 fields of social and personality psychological research appear to be linked mainly by their deficiencies and appear to have little content worth sharing. Reexamination of each field's traditions and priorities is urgently needed. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献