全文获取类型
收费全文 | 48669篇 |
免费 | 4807篇 |
国内免费 | 3326篇 |
专业分类
电工技术 | 3851篇 |
技术理论 | 2篇 |
综合类 | 4418篇 |
化学工业 | 3661篇 |
金属工艺 | 3711篇 |
机械仪表 | 7164篇 |
建筑科学 | 2627篇 |
矿业工程 | 2017篇 |
能源动力 | 1003篇 |
轻工业 | 3658篇 |
水利工程 | 745篇 |
石油天然气 | 766篇 |
武器工业 | 390篇 |
无线电 | 3334篇 |
一般工业技术 | 4467篇 |
冶金工业 | 2116篇 |
原子能技术 | 323篇 |
自动化技术 | 12549篇 |
出版年
2024年 | 248篇 |
2023年 | 1042篇 |
2022年 | 1806篇 |
2021年 | 2003篇 |
2020年 | 1861篇 |
2019年 | 1452篇 |
2018年 | 1297篇 |
2017年 | 1571篇 |
2016年 | 1760篇 |
2015年 | 1883篇 |
2014年 | 3085篇 |
2013年 | 2736篇 |
2012年 | 3526篇 |
2011年 | 3686篇 |
2010年 | 2659篇 |
2009年 | 2712篇 |
2008年 | 2570篇 |
2007年 | 3207篇 |
2006年 | 2956篇 |
2005年 | 2565篇 |
2004年 | 2030篇 |
2003年 | 1772篇 |
2002年 | 1509篇 |
2001年 | 1309篇 |
2000年 | 1049篇 |
1999年 | 846篇 |
1998年 | 635篇 |
1997年 | 541篇 |
1996年 | 424篇 |
1995年 | 418篇 |
1994年 | 319篇 |
1993年 | 240篇 |
1992年 | 182篇 |
1991年 | 148篇 |
1990年 | 144篇 |
1989年 | 146篇 |
1988年 | 122篇 |
1987年 | 47篇 |
1986年 | 39篇 |
1985年 | 34篇 |
1984年 | 23篇 |
1983年 | 34篇 |
1982年 | 26篇 |
1980年 | 14篇 |
1979年 | 15篇 |
1963年 | 8篇 |
1961年 | 8篇 |
1959年 | 11篇 |
1958年 | 8篇 |
1955年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
901.
In this paper, we consider an identical parallel machine scheduling problem with release dates. The objective is to minimize the total weighted completion time. This problem is known to be strongly NP-hard. We propose some dominance properties and two lower bounds. We also present an efficient heuristic. A branch-and-bound algorithm, in which the heuristic, the lower bounds and the dominance properties are incorporated, is proposed and tested on a large set of randomly generated instances. 相似文献
902.
We consider a single machine scheduling problem with simple linear deterioration. Job processing times are assumed to be a simple linear function of a job-dependent growth rate and the job's starting time. We seek an optimal schedule, so as to minimize the total absolute deviation of completion times (TADC). We prove several interesting properties of an optimal schedule, and introduce two efficient heuristics which are tested against a lower bound. 相似文献
903.
This paper considers single-machine scheduling problems with deteriorating jobs, i.e., jobs whose processing times are an increasing function of their starting times. In addition, the jobs are related by a series–parallel graph. It is shown that for the general linear problem to minimize the makespan, polynomial algorithms exist. It is also shown that for the proportional linear problem of minimization of the total weighted completion time, polynomial algorithms exist, too. 相似文献
904.
This paper presents a computer-aided measurement plan (CAMP) for an impeller on a coordinate measurement machine (CMM) with a rotating/tilting probe. The blade surfaces of a machined impeller were measured exactly to secure the machining tolerance and surface finish of the impeller. CMM with a rotating and tilting probe is commonly used for this measurement. However, it is not easy to evaluate all the points on the impeller surfaces due to the time-consuming nature of the CMM measurement. In addition, many points cannot be easily accessed by the CMM probe due to the interference between the probe and the impeller blades. Furthermore, the inherent complexity of the existing teaching operation of a probe using a joystick suggests the necessity of developing a new method for the measurement planning of an impeller. Thus, this paper proposes a CAMP for effectively gauging the inspection points based on the ruled line information of the impeller blade surfaces. The proposed plan partitions the surfaces into several measurement regions based on the ruled lines of a blade surface and the approach vectors of the probe. Finally, a case example for an impeller is presented to demonstrate the effectiveness of the proposed strategy. 相似文献
905.
Abdolhossein Sarrafzadeh Samuel Alexander Farhad Dadgostar Chao Fan Abbas Bigdeli 《Computers in human behavior》2008,24(4):1342-1363
Many software systems would significantly improve performance if they could adapt to the emotional state of the user, for example if Intelligent Tutoring Systems (ITSs), ATM’s, ticketing machines could recognise when users were confused, frustrated or angry they could guide the user back to remedial help systems so improving the service. Many researchers now feel strongly that ITSs would be significantly enhanced if computers could adapt to the emotions of students. This idea has spawned the developing field of affective tutoring systems (ATSs): ATSs are ITSs that are able to adapt to the affective state of students. The term “affective tutoring system” can be traced back as far as Rosalind Picard’s book Affective Computing in 1997.This paper presents research leading to the development of Easy with Eve, an ATS for primary school mathematics. The system utilises a network of computer systems, mainly embedded devices to detect student emotion and other significant bio-signals. It will then adapt to students and displays emotion via a lifelike agent called Eve. Eve’s tutoring adaptations are guided by a case-based method for adapting to student states; this method uses data that was generated by an observational study of human tutors. This paper presents the observational study, the case-based method, the ATS itself and its implementation on a distributed computer systems for real-time performance, and finally the implications of the findings for Human Computer Interaction in general and e-learning in particular. Web-based applications of the technology developed in this research are discussed throughout the paper. 相似文献
906.
It is well recognized that the impact-acoustic emissions contain information that can indicate the presence of the adhesive defects in the bonding structures. In our previous papers, artificial neural network (ANN) was adopted to assess the bonding integrity of the tile–walls with the feature extracted from the power spectral density (PSD) of the impact-acoustic signals acting as the input of classifier. However, in addition to the inconvenience posed by the general drawbacks such as long training time and large number of training samples needed, the performance of the classic ANN classifier is deteriorated by the similar spectral characteristics between different bonding status caused by abnormal impacts. In this paper our previous works was developed by the employment of the least-squares support vector machine (LS-SVM) classifier instead of the ANN to derive a bonding integrity recognition approach with better reliability and enhanced immunity to surface roughness. With the help of the specially designed artificial sample slabs, experiments results obtained with the proposed method are provided and compared with that using the ANN classifier, demonstrating the effectiveness of the present strategy. 相似文献
907.
A new Mn(II) complex of MnL2Cl2 (L = azino-di(5,6-azafluorene)-κ2-NN′) was synthesized and utilized as an electrochemical indicator for the determination of hepatitis B virus (HBV) based on its interaction with MnL2Cl2. The electrochemical behavior of interaction of MnL2Cl2 with salmon sperm DNA was investigated on glassy carbon electrode (GCE). In the presence of salmon sperm DNA, the peak current of [MnL2]2+ was decreased and the peak potential was shifted positively without appearance of new peaks. The binding ratio between [MnL2]2+ and salmon sperm DNA was calculated to be 2:1 and the binding constant was 3.72 × 108 mol2 L−2. The extent of hybridization was evaluated on the basis of the difference between signals of [MnL2]2+ with probe DNA before and after hybridization with complementary sequence. Control experiments performed with non-complementary and mismatch sequence demonstrated the good selectivity of the biosensor. With this approach, a sequence of the HBV could be quantified over the range from 1.76 × 10−8 to 1.07 × 10−6 mol L−1, with a linear correlation of r = 0.9904 and a detection limit of 6.80 × 10−9 mol L−1. Additionally, the binding mechanism was preliminarily discussed. The mode of interaction between MnL2Cl2 and DNA was found to be primary intercalation binding. 相似文献
908.
So far, most of the applications of robotic technology to education have mainly focused on supporting the teaching of subjects
that are closely related to the Robotics field, such as robot programming, robot construction, or mechatronics. Moreover,
most of the applications have used the robot as an end or a passive tool of the learning activity, where the robot has been
constructed or programmed. In this paper, we present a novel application of robotic technologies to education, where we use
the real world situatedness of a robot to teach non-robotic related subjects, such as math and physics. Furthermore, we also
provide the robot with a suitable degree of autonomy to actively guide and mediate in the development of the educational activity.
We present our approach as an educational framework based on a collaborative and constructivist learning environment, where
the robot is able to act as an interaction mediator capable of managing the interactions occurring among the working students.
We illustrate the use of this framework by a 4-step methodology that is used to implement two educational activities. These
activities were tested at local schools with encouraging results. Accordingly, the main contributions of this work are: i) A
novel use of a mobile robot to illustrate and teach relevant concepts and properties of the real world; ii) A novel use of
robots as mediators that autonomously guide an educational activity using a collaborative and constructivist learning approach;
iii) The implementation and testing of these ideas in a real scenario, working with students at local schools.
相似文献
Alvaro Soto (Corresponding author)Email: |
909.
910.
不同种类支持向量机算法的比较研究 总被引:3,自引:0,他引:3
谢承旺 《小型微型计算机系统》2008,29(1):106-109
介绍一种新型的机器学习方法-支持向量机.论述了不同种类支持向量机算法并指出了每种算法的优劣.实验结果显示了核函数中选择合适的参数对分类器的效果是很重要的,通过实验还重点比较了Chunking、SMO和SVMlight三种典型分解算法,并分析了训练速度优劣的原因.文章最后给出了今后SVM研究方向的一些预见. 相似文献