全文获取类型
收费全文 | 6861篇 |
免费 | 282篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 74篇 |
综合类 | 7篇 |
化学工业 | 1578篇 |
金属工艺 | 111篇 |
机械仪表 | 151篇 |
建筑科学 | 331篇 |
矿业工程 | 9篇 |
能源动力 | 242篇 |
轻工业 | 633篇 |
水利工程 | 62篇 |
石油天然气 | 30篇 |
武器工业 | 2篇 |
无线电 | 603篇 |
一般工业技术 | 1150篇 |
冶金工业 | 974篇 |
原子能技术 | 37篇 |
自动化技术 | 1166篇 |
出版年
2023年 | 68篇 |
2022年 | 107篇 |
2021年 | 175篇 |
2020年 | 128篇 |
2019年 | 129篇 |
2018年 | 179篇 |
2017年 | 157篇 |
2016年 | 197篇 |
2015年 | 164篇 |
2014年 | 232篇 |
2013年 | 426篇 |
2012年 | 383篇 |
2011年 | 449篇 |
2010年 | 336篇 |
2009年 | 385篇 |
2008年 | 365篇 |
2007年 | 380篇 |
2006年 | 275篇 |
2005年 | 260篇 |
2004年 | 213篇 |
2003年 | 191篇 |
2002年 | 166篇 |
2001年 | 115篇 |
2000年 | 119篇 |
1999年 | 116篇 |
1998年 | 122篇 |
1997年 | 128篇 |
1996年 | 89篇 |
1995年 | 107篇 |
1994年 | 90篇 |
1993年 | 68篇 |
1992年 | 68篇 |
1991年 | 33篇 |
1990年 | 54篇 |
1989年 | 68篇 |
1988年 | 51篇 |
1987年 | 39篇 |
1986年 | 53篇 |
1985年 | 58篇 |
1984年 | 50篇 |
1983年 | 56篇 |
1982年 | 37篇 |
1981年 | 35篇 |
1980年 | 33篇 |
1979年 | 28篇 |
1978年 | 19篇 |
1977年 | 20篇 |
1976年 | 26篇 |
1975年 | 30篇 |
1974年 | 22篇 |
排序方式: 共有7160条查询结果,搜索用时 15 毫秒
31.
We compare, in this paper, the far field radiated by two fractal distributions of current. The first one is obtained by a fractal cut following the Cantor arrangement, the second one keeps the length of each previous current element, but modifies the distance between the elements which is now taken as a constant. We establish the analytical formulations of the far field at any step n of the Cantor set. Then, we extract the array factor and we analyse and compare the following properties : convergence of the radiation pattern, wide of the main lobe, side lobes level and directivity. 相似文献
32.
Patrick E. Mcsharry Paulo R. C. Ruffino 《Dynamical Systems: An International Journal》2003,18(3):191-200
The asymptotic angular stability of a dynamical system may be quantified by its rotation number or its winding number. These two quantities are shown to result from different assumptions, made about the flow generating the Poincaré map which results from the sequence of homeomorphisms in S l. An ergodic theorem of existence a.s. of the rotation number for non-linear systems is given. The advantages and disadvantages of both the rotation and winding numbers are discussed. Numerical calculations of the distribution of rotation number and winding number arising from different initial conditions are presented for three different chaotic maps. 相似文献
33.
Patrick McBrayer 《Information Systems Management》1998,15(1):1-4
ATM promises increased functionality and performance for users and decreased costs for corporate voice and data networks. the tips provided here focus on the vendor selection and installation processes, which are critical to the successful design and implementation of an ATM network. 相似文献
34.
Ma Shizhou Beazley Karen F. Nussey Patrick Greene Christopher S. 《Water Resources Management》2021,35(14):4825-4840
Water Resources Management - The Active River Area (ARA) is a spatial approach for identifying the extent of functional riparian area. Given known limitations in terms of input elevation data... 相似文献
35.
Artificial intelligence (AI) has been heralded by many as the next source of business value. Grounded on the resource-based theory of the firm and on recent work on AI at the organizational context, this study (1) identifies the AI-specific resources that jointly create an AI capability and provides a definition, (2) develops an instrument to capture the AI capability of the firms, and (3) examines the relationship between an AI capability and organizational creativity and performance. Findings empirically support the suggested theoretical framework and corresponding instrument and provide evidence that an AI capability results in increased organizational creativity and performance. 相似文献
36.
Sidney D'Mello Andrew Olney Claire Williams Patrick Hays 《International journal of human-computer studies》2012,70(5):377-398
We developed an intelligent tutoring system (ITS) that aims to promote engagement and learning by dynamically detecting and responding to students' boredom and disengagement. The tutor uses a commercial eye tracker to monitor a student's gaze patterns and identify when the student is bored, disengaged, or is zoning out. The tutor then attempts to reengage the student with dialog moves that direct the student to reorient his or her attentional patterns towards the animated pedagogical agent embodying the tutor. We evaluated the efficacy of the gaze-reactive tutor in promoting learning, motivation, and engagement in a controlled experiment where 48 students were tutored on four biology topics with both gaze-reactive and non-gaze-reactive (control condition) versions of the tutor. The results indicated that: (a) gaze-sensitive dialogs were successful in dynamically reorienting students’ attentional patterns to the important areas of the interface, (b) gaze-reactivity was effective in promoting learning gains for questions that required deep reasoning, (c) gaze-reactivity had minimal impact on students’ state motivation and on self-reported engagement, and (d) individual differences in scholastic aptitude moderated the impact of gaze-reactivity on overall learning gains. We discuss the implications of our findings, limitations, future work, and consider the possibility of using gaze-reactive ITSs in classrooms. 相似文献
37.
Peter Demeester Burak Bilgin Patrick De Causmaecker Greet Vanden Berghe 《Journal of Scheduling》2012,15(1):83-103
Many researchers studying examination timetabling problems focus on either benchmark problems or problems from practice encountered
in their institutions. Hyperheuristics are proposed as generic optimisation methods which explore the search space of heuristics
rather than direct solutions. In the present study, the performance of tournament-based hyperheuristics for the exam timetabling
problem are investigated. The target instances include both the Toronto and ITC 2007 benchmarks and the examination timetabling
problem at KAHO Sint-Lieven (Ghent, Belgium). The Toronto and ITC 2007 benchmarks are post-enrolment-based examination timetabling
problems, whereas the KAHO Sint-Lieven case is a curriculum-based examination timetabling problem. We drastically improve
the previous (manually created) solution for the KAHO Sint-Lieven problem by generating a timetable that satisfies all the
hard and soft constraints. We also make improvements on the best known results in the examination timetabling literature for
seven out of thirteen instances for the To ronto benchmarks. The results are competitive with those of the finalists of the
examination timetabling track of the International Timetabling Competition. 相似文献
38.
Monique Jackson Ines Benkhemis Micka?l Begon Philippe Sardain Claude Vallée Patrick Lacouture 《Multibody System Dynamics》2012,28(3):225-237
Optimal synthesis of human movement or the prediction of the kinematics of a new movement require not only that the multi-body system be modeled but also that a performance criterion is specified. For sub-maximal movements the selection of a suitable performance criterion, able to generate realistic dynamic behavior is difficult. A two-dimensional simulation model of the take-off phase of a sub-maximal long jump was developed to study the effect of criterion choice on the realism of simulated movements. A parametric optimization technique was employed to obtain solutions to the constrained equations of motion. Seven different criteria were evaluated, by comparing simulated movements with an actual performance, to identify the criterion which most closely approximated that spontaneously minimized by the athlete. Synthesis of the take-off phase of a sub-maximal long jump was found to be sensitive to the chosen criterion, with a criterion based on minimizing joint intersegmental forces found to perform well. 相似文献
39.
Patrick Heymans Quentin Boucher Andreas Classen Arnaud Bourdoux Laurent Demonceau 《International Journal on Software Tools for Technology Transfer (STTT)》2012,14(5):553-566
Software product line engineering seeks to systematise reuse when developing families of similar software systems so as to minimise development time, cost and defects. To realise variability at the code level, product line methods classically advocate usage of inheritance, components, frameworks, aspects or generative techniques. However, these might require unaffordable paradigm shifts for developers if the software was not thought at the outset as a product line. Furthermore, these techniques can be conflicting with a company’s coding practices or external regulations. These concerns were the motivation for the industry–university collaboration described in this paper in which we developed a minimally intrusive coding technique based on tags. The approach was complemented with traceability from code to feature diagrams which were exploited for automated configuration. It is supported by a toolchain and is now in use in the partner company for the development of flight-grade satellite communication software libraries. 相似文献
40.
Successful planning and control of robots strongly depends on the quality of kinematic models, which define mappings between
configuration space (e.g. joint angles) and task space (e.g. Cartesian coordinates of the end effector). Often these models
are predefined, in which case, for example, unforeseen bodily changes may result in unpredictable behavior. We are interested
in a learning approach that can adapt to such changes—be they due to motor or sensory failures, or also due to the flexible
extension of the robot body by, for example, the usage of tools. We focus on learning locally linear forward velocity kinematics
models by means of the neuro-evolution approach XCSF. The algorithm learns self-supervised, executing movements autonomously
by means of goal-babbling. It preserves actuator redundancies, which can be exploited during movement execution to fulfill
current task constraints. For detailed evaluation purposes, we study the performance of XCSF when learning to control an anthropomorphic
seven degrees of freedom arm in simulation. We show that XCSF can learn large forward velocity kinematic mappings autonomously
and rather independently of the task space representation provided. The resulting mapping is highly suitable to resolve redundancies
on the fly during inverse, goal-directed control. 相似文献