全文获取类型
收费全文 | 90423篇 |
免费 | 1196篇 |
国内免费 | 414篇 |
专业分类
电工技术 | 880篇 |
综合类 | 2333篇 |
化学工业 | 13367篇 |
金属工艺 | 4902篇 |
机械仪表 | 3110篇 |
建筑科学 | 2618篇 |
矿业工程 | 582篇 |
能源动力 | 1230篇 |
轻工业 | 4471篇 |
水利工程 | 1292篇 |
石油天然气 | 354篇 |
无线电 | 9634篇 |
一般工业技术 | 17434篇 |
冶金工业 | 3393篇 |
原子能技术 | 305篇 |
自动化技术 | 26128篇 |
出版年
2022年 | 96篇 |
2021年 | 120篇 |
2020年 | 83篇 |
2019年 | 115篇 |
2018年 | 14533篇 |
2017年 | 13444篇 |
2016年 | 10100篇 |
2015年 | 753篇 |
2014年 | 454篇 |
2013年 | 524篇 |
2012年 | 3450篇 |
2011年 | 9718篇 |
2010年 | 8541篇 |
2009年 | 5830篇 |
2008年 | 7070篇 |
2007年 | 8049篇 |
2006年 | 411篇 |
2005年 | 1458篇 |
2004年 | 1339篇 |
2003年 | 1340篇 |
2002年 | 660篇 |
2001年 | 204篇 |
2000年 | 297篇 |
1999年 | 178篇 |
1998年 | 198篇 |
1997年 | 142篇 |
1996年 | 124篇 |
1995年 | 98篇 |
1994年 | 108篇 |
1993年 | 84篇 |
1992年 | 88篇 |
1991年 | 106篇 |
1990年 | 69篇 |
1989年 | 75篇 |
1988年 | 76篇 |
1987年 | 82篇 |
1986年 | 57篇 |
1985年 | 78篇 |
1984年 | 85篇 |
1983年 | 57篇 |
1981年 | 67篇 |
1980年 | 67篇 |
1979年 | 58篇 |
1978年 | 57篇 |
1977年 | 65篇 |
1976年 | 74篇 |
1968年 | 60篇 |
1966年 | 63篇 |
1955年 | 70篇 |
1954年 | 73篇 |
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
991.
Maintenance as an important part in manufacturing system can keep equipment in good condition. Many maintenance policies help
to decrease the unexpected failures and reduce high operational cost such as conventional preventive maintenance. But these
conventional preventive maintenance policies have the same time interval T that may easily neglect system’s reliability, because the system deteriorates with increased usage and age. Hence, this study
has developed a reliability-centred sequential preventive maintenance model for monitored repairable deteriorating system.
It is supposed that system’s reliability could be monitored continuously and perfectly, whenever it reaches the threshold
R, the imperfect repair must be performed to restore the system. In this model, system’s failure rate function and operational
cost are both considered by the effect of system’s corresponding condition, which helps to decide the optimal reliability
threshold R and preventive maintenance cycle number. Finally, through case study, the simulation results show that the improved sequential
preventive maintenance policy is more practical and efficient. 相似文献
992.
A telebiometric system mechanism model and biometric network protocol for the security of networked manufacturing 总被引:1,自引:1,他引:0
Networked manufacturing changes conventional enterprise activities. With a networked manufacturing system, enterprises are
able to perform a range of activities, such as product planning, design, production, and marketing, in collaboration with
international partners, regardless of geographical location. However, strict security measures are required, as the authentication
and information transfers for networked manufacturing are conducted over a network. With the development of biometric technology,
more and more enterprises are using the unique biometric data of individuals to verify the identity of users, in order to
restrict and provide access to technology research centers or factory facilities. This paper analyzes the vulnerabilities
of the biometric system used for access control and the authentication of access to confidential information in the networked
manufacturing system. In addition, the biometric systems that can be built in an open network environment are classified into
9 general models, and a biometric network protocol is suggested that is secure and compatible with international standards. 相似文献
993.
Tristan Behrens Mehdi Dastani Jürgen Dix Michael Köster Peter Novák 《Annals of Mathematics and Artificial Intelligence》2010,59(3-4):277-311
The Multi-Agent Programming Contest is an annual international event on programming multi-agent systems: Teams of agents participate in a simulated cooperative scenario. It started in 2005 and is organised in 2010 for the sixth time. The contest is an attempt to stimulate research in the area of multi-agent system development and programming by (i) identifying key problems in the field and (ii) collecting suitable benchmarks that can serve as milestones for testing multi-agent programming languages, platforms and tools. This article provides a short history of the contest since it started and reports in more detail on the cows and cowboys scenario implemented for the 2008, 2009 and 2010 contest editions. We briefly discuss the underlying technological background and conclude with a critical discussion of the experiences and lessons learned. 相似文献
994.
V. K. De Wansa Wickramaratne A. P. Vinogradov V. V. Ryazanov T. M. Dudnikova 《Pattern Recognition and Image Analysis》2010,20(2):237-240
Calibration of the digital projector is a necessary procedure for many 3D scanners. The proposed method for automatic calibration
of a projector uses binary color templates and searches for the most stable points for minimization of decoding errors. The
camera resolution must significantly exceed the projector’s resolution. The method can be easily adapted for operation with
black-and-white templates. 相似文献
995.
In a number of prior papers we described and explored a new pattern recognition method called Margin-Setting that accomplishes
excellent generalization using very few training samples. The result was a multi-round classifier with each round consisting
of a set of hyperspheres such that if a datum fell within a certain hypersphere, it was labeled with one particular class.
Margin-Setting achieves concurrent low Vapnik-Chervonenkis (VC) dimension and high accuracy which is a consequence of partitioning
the training set into smaller sets that make this possible. This paper extends Margin-Setting from hyperspheres to hyperellipsoids
resulting in improved performance. 相似文献
996.
997.
We consider large volume job shop scheduling problems, in which there is a fixed number of machines, a bounded number of activities
per job, and a large number of jobs. In large volume job shops it makes sense to solve a fluid problem and to schedule the
jobs in such a way as to track the fluid solution. There have been several papers which used this idea to propose approximate
solutions which are asymptotically optimal as the volume increases. We survey some of these results here. In most of these
papers it is assumed that the problem consists of many identical copies of a fixed set of jobs. Our contribution in this paper
is to extend the results to the far more general situation in which the many jobs are all different. We propose a very simple
heuristic which can schedule such problems. We discuss asymptotic optimality of this heuristic, under a wide range of previously
unexplored situations. We provide a software package to explore the performance of our policy, and present extensive computational
evidence for its effectiveness. 相似文献
998.
This paper presents an improved constraint satisfaction adaptive neural network for job-shop scheduling problems. The neural
network is constructed based on the constraint conditions of a job-shop scheduling problem. Its structure and neuron connections
can change adaptively according to the real-time constraint satisfaction situations that arise during the solving process.
Several heuristics are also integrated within the neural network to enhance its convergence, accelerate its convergence, and
improve the quality of the solutions produced. An experimental study based on a set of benchmark job-shop scheduling problems
shows that the improved constraint satisfaction adaptive neural network outperforms the original constraint satisfaction adaptive
neural network in terms of computational time and the quality of schedules it produces. The neural network approach is also
experimentally validated to outperform three classical heuristic algorithms that are widely used as the basis of many state-of-the-art
scheduling systems. Hence, it may also be used to construct advanced job-shop scheduling systems. 相似文献
999.
In this paper we study parallel batch scheduling problems with bounded batch capacity and equal-length jobs in a single and
parallel machine environment. It is shown that the feasibility problem 1|p-batch,b<n,r
j
,p
j
=p,C
j
≤d
j
|− can be solved in O(n
2) time and that the problem of minimizing the maximum lateness can be solved in O(n
2log n) time. For the parallel machine problem P|p-batch,b<n,r
j
,p
j
=p,C
j
≤d
j
|− an O(n
3log n)-time algorithm is provided, which can also be used to solve the problem of minimizing the maximum lateness in O(n
3log 2
n) time. 相似文献
1000.
In this study, a two-machine flowshop producing identical parts is considered. Each of the identical parts is assumed to require
a number of manufacturing operations, and the machines are assumed to be flexible enough to perform different operations.
Due to economical or technological constraints, some specific operations are preassigned to one of the machines. The remaining
operations, called flexible operations, can be performed on either one of the machines, so that the same flexible operation
can be performed on different machines for different parts. The problem is to determine the assignment of the flexible operations
to the machines for each part, with the objective of maximizing the throughput rate. We consider various cases regarding the
number of parts to be produced and the capacity of the buffer between the machines. We present solution methods for each variant
of the problem. 相似文献