全文获取类型
收费全文 | 8030篇 |
免费 | 406篇 |
国内免费 | 21篇 |
专业分类
电工技术 | 72篇 |
综合类 | 4篇 |
化学工业 | 1424篇 |
金属工艺 | 161篇 |
机械仪表 | 161篇 |
建筑科学 | 339篇 |
矿业工程 | 14篇 |
能源动力 | 199篇 |
轻工业 | 633篇 |
水利工程 | 82篇 |
石油天然气 | 23篇 |
无线电 | 756篇 |
一般工业技术 | 1592篇 |
冶金工业 | 1821篇 |
原子能技术 | 60篇 |
自动化技术 | 1116篇 |
出版年
2023年 | 66篇 |
2022年 | 108篇 |
2021年 | 190篇 |
2020年 | 151篇 |
2019年 | 162篇 |
2018年 | 198篇 |
2017年 | 188篇 |
2016年 | 236篇 |
2015年 | 177篇 |
2014年 | 287篇 |
2013年 | 444篇 |
2012年 | 466篇 |
2011年 | 582篇 |
2010年 | 363篇 |
2009年 | 326篇 |
2008年 | 435篇 |
2007年 | 391篇 |
2006年 | 340篇 |
2005年 | 279篇 |
2004年 | 254篇 |
2003年 | 193篇 |
2002年 | 222篇 |
2001年 | 145篇 |
2000年 | 117篇 |
1999年 | 117篇 |
1998年 | 343篇 |
1997年 | 193篇 |
1996年 | 177篇 |
1995年 | 98篇 |
1994年 | 112篇 |
1993年 | 110篇 |
1992年 | 61篇 |
1991年 | 61篇 |
1990年 | 54篇 |
1989年 | 53篇 |
1988年 | 45篇 |
1987年 | 42篇 |
1986年 | 50篇 |
1985年 | 61篇 |
1984年 | 36篇 |
1983年 | 44篇 |
1982年 | 32篇 |
1981年 | 39篇 |
1980年 | 34篇 |
1979年 | 25篇 |
1978年 | 32篇 |
1977年 | 50篇 |
1976年 | 58篇 |
1975年 | 22篇 |
1971年 | 22篇 |
排序方式: 共有8457条查询结果,搜索用时 15 毫秒
91.
Combinatorial interaction testing (CIT) is a cost-effective sampling technique for discovering interaction faults in highly-configurable
systems. Constrained CIT extends the technique to situations where some features cannot coexist in a configuration, and is
therefore more applicable to real-world software. Recent work on greedy algorithms to build CIT samples now efficiently supports
these feature constraints. But when testing a single system configuration is expensive, greedy techniques perform worse than
meta-heuristic algorithms, because greedy algorithms generally need larger samples to exercise the same set of interactions.
On the other hand, current meta-heuristic algorithms have long run times when feature constraints are present. Neither class
of algorithm is suitable when both constraints and the cost of testing configurations are important factors. Therefore, we
reformulate one meta-heuristic search algorithm for constructing CIT samples, simulated annealing, to more efficiently incorporate
constraints. We identify a set of algorithmic changes and experiment with our modifications on 35 realistic constrained problems
and on a set of unconstrained problems from the literature to isolate the factors that improve performance. Our evaluation
determines that the optimizations reduce run time by a factor of 90 and accomplish the same coverage objectives with even
fewer system configurations. Furthermore, the new version compares favorably with greedy algorithms on real-world problems,
and, though our modifications were aimed at constrained problems, it shows similar advantages when feature constraints are
absent. 相似文献
92.
A map‐aided localization approach using vision, inertial sensors when available, and a particle filter is proposed and empirically evaluated. The approach, termed PosteriorPose, uses a Bayesian particle filter to augment global positioning system (GPS) and inertial navigation solutions with vision‐based measurements of nearby lanes and stop lines referenced against a known map of environmental features. These map‐relative measurements are shown to improve the quality of the navigation solution when GPS is available, and they are shown to keep the navigation solution converged in extended GPS blackouts. Measurements are incorporated with careful hypothesis testing and error modeling to account for non‐Gaussian and multimodal errors committed by GPS and vision‐based detection algorithms. Using a set of data collected with Cornell's autonomous car, including a measure of truth via a high‐precision differential corrections service, an experimental investigation of important design elements of the PosteriorPose estimator is conducted. The algorithm is shown to statistically outperform a tightly coupled GPS/inertial navigation solution both in full GPS coverage and in extended GPS blackouts. Statistical performance is also studied as a function of road type, filter likelihood models, bias models, and filter integrity tests. © 2011 Wiley Periodicals, Inc. 相似文献
93.
This paper presents a new approach to improve tool selection for arbitrary shaped pockets based on an approximate polygon subdivision technique. The pocket is subdivided into smaller sub-polygons and tools are selected separately for each sub-polygon. A set of tools for the entire pocket is obtained based on both machining time and the number of tools used. In addition, the sub-polygons are sequenced to eliminate the requirement of multiple plunging operations. In process planning for pocket machining, selection of tool sizes and minimizing the number of plunging operations can be very important factors. The approach presented in this paper is an improvement over previous work in its use of a polygon subdivision strategy to improve the machining time as well as reducing the number of plunges. The implementation of this technique suggests that using a subdivision approach can reduce machining time when compared to solving for the entire polygonal region. 相似文献
94.
A new three-phase electrode array with a serpentine electrode is designed and prototyped using PolyMUMPs process for micro
flow pumping. Numerical model of the micropump has been developed using COMSOL Multiphysics™. Experimental testing is conducted
and time-averaged flow velocities from testing and simulation agree well. Peak time-averaged flow velocity of 270 μm/s is
achieved at 30 Hz using ethanol. 相似文献
95.
The knowledge economy offers opportunity to a broad and diverse community of information systems users to efficiently gain
information and know-how for improving qualifications and enhancing productivity in the work place. Such demand will continue
and users will frequently require optimised and personalised information content. The advancement of information technology
and the wide dissemination of information endorse individual users when constructing new knowledge from their experience in
the real-world context. However, a design of personalised information provision is challenging because users’ requirements
and information provision specifications are complex in their representation. The existing methods are not able to effectively
support this analysis process. This paper presents a mechanism which can holistically facilitate customisation of information
provision based on individual users’ goals, level of knowledge and cognitive styles preferences. An ontology model with embedded
norms represents the domain knowledge of information provision in a specific context where users’ needs can be articulated
and represented in a user profile. These formal requirements can then be transformed onto information provision specifications
which are used to discover suitable information content from repositories and pedagogically organise the selected content
to meet the users’ needs. The method is provided with adaptability which enables an appropriate response to changes in users’
requirements during the process of acquiring knowledge and skills. 相似文献
96.
97.
In this paper, we search for theoretical limitations of the Tile Assembly Model (TAM), along with techniques to work around such limitations. Specifically, we investigate
the self-assembly of fractal shapes in the TAM. We prove that no self-similar fractal weakly self-assembles at temperature
1 in a locally deterministic tile assembly system, and that certain kinds of discrete self-similar fractals do not strictly
self-assemble at any temperature. Additionally, we extend the fiber construction of Lathrop et al. (2009) to show that any discrete self-similar fractal belonging to a particular class of “nice” discrete self-similar fractals
has a fibered version that strictly self-assembles in the TAM. 相似文献
98.
Trust mechanisms are used in peer‐to‐peer (P2P) networks to help well‐behaving peers find other well‐behaving peers with which to trade. Unfortunately, these trust mechanisms often do little to keep badly behaving peers from entering and taking advantage of the network, which makes the resulting network difficult or impossible to use for legitimate purposes such as e‐commerce. We propose trust by association, a way of tying peers together in invitation‐only P2P networks in such a way as to encourage the removal of badly behaving peers. We use invitations to create a structure within the otherwise ad hoc P2P network. Using this structure, we create a meta‐reputation system where we measure a peer’s trustworthiness not only by its own behavior, but also by the behavior of the peers it has invited to join. The connection created between the peers takes advantage of the external social relationship that must exist before a peer can be invited into the network. The result is a P2P network where, rather than just trying to marginalize badly behaving peers, there is incentive to kick them out of the network. We present results from a simple simulation showing that our approach works well in general when combined with and compared to an existing trust mechanism. 相似文献
99.
Xilin Yang Matthew Garratt Hemanshu Pota 《Journal of Intelligent and Robotic Systems》2011,61(1-4):267-285
This paper presents a novel and practical procedure for estimating the mean deck height to assist in automatic landing operations of a Rotorcraft Unmanned Aerial Vehicle (RUAV) in harsh sea environments. A modified Prony Analysis (PA) procedure is outlined to deal with real-time observations of deck displacement, which involves developing an appropriate dynamic model to approach real deck motion with parameters identified through implementing the Forgetting Factor Recursive Least Square (FFRLS) method. The model order is specified using a proper order-selection criterion based on minimizing the summation of accumulated estimation errors. In addition, a feasible threshold criterion is proposed to separate the dominant components of deck displacement, which results in an accurate instantaneous estimation of the mean deck position. Simulation results demonstrate that the proposed recursive procedure exhibits satisfactory estimation performance when applied to real-time deck displacement measurements, making it well suited for integration into ship-RUAV approach and landing guidance systems. 相似文献
100.
This paper presents a model which predicts the part orientation error tolerance of a three-fingered robotic gripper. The concept of “self-alignment” is introduced, where the gripper uses the grasping process to bring the workpiece into its final state of orientation. The gripper and part are represented mathematically, and initial contact locations upon grasp closure determined. This information is used to solve for the contact forces present, and criteria are developed to determine if beneficial part motion resulting in self-alignment is expected. The results are visualized via a boundary projected on a reference plane below the part. The model is validated experimentally with a number of part configurations with favorable results. This method presents a useful tool by which the mechanical designer can quantitatively predict the performance of an intuitively designed gripping system. 相似文献